This PDF file contains the front matter associated with SPIE Proceedings Volume 7578, including the Title Page, Copyright information, Table of Contents, and the Conference Committee listing.

We discuss past, present and future spaceborne laser instruments for high-resolution mapping of Earth and planetary surfaces. Previous spaceborne-laser-altimeters projected and imaged a single laser spot for surface-height measurements. In contrast, the recent Lunar Orbiter Laser Altimeter (LOLA) instrument on the Lunar Reconnaissance Orbiter (LRO) uses a non-scanning multi-beam system for surface topography mapping. The multi-beam instrument facilitates surface slope measurement and reduces the time-to-completion for global high-resolution topographic mapping. We discuss our first-year progress on a three-year swath-mapping laser-altimetry Instrument Incubator Program (IIP) funded by the NASA Earth Science Technology Office (ESTO). Our IIP is a technology development program supporting the LIdar Surface Topography (LIST) space-flight mission that is a third-tier mission as recommended by the National Research Council (NRC) for NASA's Earth Science programs.

NASA's space-borne laser missions have been dominated by low repetition rate (<100Hz) Q-switched laser systems, which use Nd:YAG laser crystals, and are pumped by quasi-continuous wave (QCW) 808 nm laser diode arrays (LDAs). The diode group at NASA Goddard Space Flight Center (GSFC) has been responsible for the screening and qualification of LDAs for several missions. The main goal has been to identify LDAs that can withstand the harsh space environment, and minimize risks associated with LDA degradation or failure. This paper presents a summary of recent research activities, and describes the results from extended testing of multiple LDAs in air and vacuum environments.

Over the last two decades NASA Goddard Space Flight Center (GSFC) has developed several laser systems for space application. The aging behavior of a laser system varies depending on the complexity of the system and the technologies used. One limitation of reliability models trying to predict system performance has been the lack of test data. Extended testing is an effective way to determine the reliability, and long term stability of laser systems. In this paper the results from extended testing of two laser system are presented. One system has been operating for over two and a half billion shots in air while the second system has accumulated half a billion shots while operating in a vacuum environment.

A compact, passively q-switched, single mode laser has been developed for space based lidar applications. The Nd:YAG laser produces 50mJ pulse-energy at 100 Hz repetition rate in a near diffraction limited beam with more than 99.99% of the pulses in a single longitudinal mode. This laser was initially developed as a candidate for the ICESat-2 mission, which requires five years continuous operation in space. The laser is based on two newly developed technologies, Etalon Coupled High Output (ECHO) oscillator and Ring Amplified Solid State Laser (RASSL). In this paper, we will present the laser design and discuss the laser performance and experimental results. We will also present a unique laser package concept.

The first NASA Ice, Cloud and land Elevation Satellite (ICESat) was launched in January 2003 and placed into a nearpolar orbit whose primary mission was the global monitoring of the Earth's ice sheet mass balance. ICESat has accumulated over 1.8 B shots in space and provided a valuable dataset in the study of ice sheet dynamics over the past few years. NASA is planning a follow-on mission ICESat-2 to be launched tentatively in 2015. In this paper we will discuss the development effort of the laser transmitters for the ICESat-2 mission.

The thin-disk laser concept with its advantages high efficiency, excellent beam quality, and low depolarization losses provides a reliable platform for the generation of high power lasers in the infrared as well as the green spectral range. By employing intracavity-frequency conversion, we have obtained a maximum output power of 700 W at 515 nm and a repetition rate of 100 kHz from a Q-switched Yb:YAG thin-disk laser. An LBO crystal cut for critical phase matching of type I was mounted near one of the end mirrors inside the laser cavity. An optical efficiency (green output power with respect to incident pumping power) greater than 35% could be reached. By changing the low-loss duration at the Q-switch the pulse duration of the laser system can be adjusted between 200 ns and 750 ns with the longer pulse durations being generated with the highest efficiency. This feature can be used to maintain a constant pulse duration when varying the pumping power or repetition rate. The beam parameter product of 4 mmmrad (M² < 25) allows for beam delivery via an optical fiber with 100 μm core diameter. To the best of our knowledge, the average power significantly exceeds all previously published results for lasers in the visible spectrum.

We report on the development of a ytterbium-based disk amplifier for an ultra-short pulse laser using edge-pumped architecture and offering excellent scalability to high-average power in the kW-range. The disk has a composite construction with undoped perimetral edge designed to channel pump light while efficiently outcoupling amplified spontaneous emission. Uniform extraction of waste heat together with uniform pumping offers very low optical path distortion and allows for amplification of near diffraction limited beams in nanosecond-class pulses. This work discusses performance modeling of the edgepumped disk amplifier using a newly developed time-dependent 2-dimensional (spatial) model for dynamic pumping and extraction. Selection of laser materials and an innovative two-disk amplifier architecture for multiple extractions are also presented.

While the Disk laser concept was invented in the early 90s, the first industrial products were available in the beginning of this decade. Since then, the disk laser is used in mass production and serves a large variety of application fields. The output power per disk has continually increased and reached a level of 2.5 kW per disk in 2007. As of today, the disk principle has not reached any fundamental limit regarding output power per disk or beam quality, and offers many advantages over other high power resonator architectures. In early 2009 TRUMPF released a new series of industrial disk lasers. This series is based on an output power of 4 kW per disk. Scalability of output power is achieved by serial coupling of several disks without influencing the beam quality of the system, with output powers of up to 16 kW at work piece. The new TruDisk laser series has incorporated several advancements compared to older generation disk lasers, which have allowed a considerable reduction of running cost, investment cost and footprint. This paper will explain important details of the TruDisk laser series and process relevant features of the system, like pump diode arrangement, resonator design and integrated beam guidance. In addition, advances in applications in the thick sheet area and very cost efficient high productivity applications like remote welding, remote cutting and cutting of thin sheets will be discussed.

In this paper, I present quantitative designs of 25-kW and 100-kW laser oscillators containing a number of Yb-ceramic YAG rotary disk laser generators. A design of an unstable resonator for the 100- kW laser is also presented. The design is modular, with identical Yb-YAG rotary disk laser generators stacked in series in a laser oscillator. Each rotary disk laser generator is identically pumped and cooled. The calculations for one design example shows that with a 10-disk laser oscillator, 100-kW of laser power may be extracted from an unstable resonator of magnification 3 at 46% optical efficiency and 53% slope efficiency. Assuming 60% efficient laser diodes will be possible in the near future, the 100-kW rotary disk laser design will require 367 kW of electrical power to produce 65 kW of power in a far-field bucket of angular radius 1.5 λ/D.

We demonstrate the first thin disk epitaxial Tm-laser based on the monoclinic KLu(WO4)2 with 15 at. % doping. The doped epitaxial layer serving as an active medium is only 80 μm thick. The large absorption enables efficient pumping with only a single double pass of the pump radiation from the diode-laser. For output coupling between 0.4% and 2.8 %, the slope efficiency in the continuous-wave regime is in the 7-11% range and the laser threshold is 1.5...2.5 W of absorbed pump power. The laser emission spectra are centered at ~1850, 1915 and 1940 nm for output couples of 2.8%, 1.6% and 0.4% transmission, respectively. In all cases the emission spectra are "structured", consisting of a number (typically 5...10) of narrow emission lines spread irregularly over 15...30 nm.

Chemically Activated Direct Bonding (CADB®) has become widely utilized as an epoxy-free assembly process for solid state laser crystals in high fluence and other aggressive environments. While data has been presented as to both optical and mechanical properties of these bond interfaces, previous research has hinted that sample preparation plays a large part in the final results. Surface finish of samples and any surface defects or sub-surface damage present can lead to artificially low strength values and other inconclusive results. In the current study, we prepared samples with polished surfaces to improve the accuracy of the bond strength measurements. Here we present strength data for bonded and bulk samples of common laser materials such as YAG, phosphate glass, and fused silica.

We report on the results of an experimental and theoretical investigation of the relevant performance attributes of Yb:YAG thin disk gain elements for use in high brightness resonators. We compare the laser operation, under extremely high pump and laser power densities, of crystalline thin disks to ceramic disks with undoped, amplified spontaneous emission (ASE) suppressing caps. The disks were operated with impingement cooling either directly on the back (high reflecting) surface or on heat spreaders. Although high optical efficiency was generally maintained, we found a marked difference in both the strength of ASE and the thermo-optical performance of the disks.

We report total-reflection active-mirror laser experiments by using a cryogenic Yb:YAG composite ceramic. The composite ceramic has no high reflection coating on the bottom surface, and is cooled with liquid nitrogen directly. We obtained 273 W output power with optical efficiency of 65% and slope efficiency of 72% against the absorbed pump power. The laser power and optical efficiency will be improved more when the pump power increases further. To investigate thermal effects of the laser material in more detail, we have measured the thermal lens focal length and the temperature of Yb:YAG. We observed thermal lensing effect of f ~ 2000 mm, and the maximum temperature of 150 K for 400 μm-thick Yb:YAG sample. We have also studied the theoretical analysis of thermal distribution in the composite ceramic.

A planar waveguide laser consisting of a 13mm x 12mm x 150μm Yb:YAG core with 1mm high sapphire claddings is edge pumped using two 450W diode stacks with custom aberration correcting phase-plates. A plano-concave resonator gives 400W average power in a low-order transverse, multi-longitudinal mode beam with 75% slope efficiency, comparable to other thin disk and slab lasers. Transverse beam quality is improved through use of novel mode selective toroidal laser-cut resonator mirrors, whilst lateral beam quality is improved through the use of an unstable resonator. Uniform gain with an amplification of 3-4 per pass shows promise for amplifier operation.

Increasing the output power of Nd:YAG's ⁴F_3/2→⁴I_9/2 quasi-four-level transition is attractive for providing a highradiance source with a wavelength below 1micron for applications at the life sciences interface, ranging and sensing, or as a vital element for next-generation display technologies, when frequency converted into the blue-green part of the visible spectrum. Reabsorption losses at the lasing wavelength combined with a relatively low stimulated emission crosssection and competition with the much stronger 1.06 micron transition, demands a configuration with high pumping intensity, comparable to the pump saturation intensity at 808 nm, to achieve efficient operation. However, even with the availability of increasingly bright diode-lasers, the thermal deficit of the excitation cycle and the thermo-optic properties of the YAG host medium currently limit the achievable output power at 9xx nm. Presented here is a double-clad planarwaveguide Nd:YAG laser, operating at a lasing wavelength of 946 nm with an output power in the 100 W regime and better than 50% optical to optical conversion efficiency. The enhanced thermal management characteristics of the waveguide structure have enabled power-scaling well beyond that possible in a bulk laser configuration. These advantages and further power-scaling possibilities will be discussed.

Through an optimal combination of crystal shape, cooling and resonator design, InnoSlab lasers possess unified advantageous features of short pulse duration and high peak output power, high pulse repetition rate, high beam quality and high flexibility in beam profile, from circular beam profile, through line shaped one dimensional Top-hat, to two dimensional Top-hat with rectangular cross section. We report diode end pumped, electrooptically q-switched Nd:YLF, Nd:YAG and Nd:YVO₄ slab laser and their efficient harmonic generation in near field. Using oscillator/amplifier with Nd:YAG slabs over 50mJ pulse energy at 6kHz was obtained. The pulse length is 7ns and the peak power is as high as 7MW. With Nd:YVO₄ slabs 400W average power at 50kHz was obtained. The pulse length is as short as 8ns. Because of the high peak power over 300W second harmonic is achieved by two LBO crystals.

The green cw laser presented in this work is realized by means of a Pr:YLF crystal emitting at 523 nm that is pumped by a blue GaN laser diode in an extremely short resonator. With a 500 mW-diode a laser has been achieved with M² = 1, a slope of 40 % and an output power of 140mW with an absorbed pump power of 410 mW which results in an electrooptical efficiency of 6.5 %. Despite the reduced overlap with a 1 W-diode the output power rises to 290 mW with an absorbed pump power of 850 mW and the M² increases only slightly. Based on these results a compact laser package has been accomplished using a monolithic micro optics for the beam shaping of the diode light and joining all components with a low-shrinkage adhesive on a common base plate. In a first test of the alignment strategy a laser with an output power of 92 mW has been achieved by means of the 500 mW pump power.

In this work the reduction of conversion efficiency due to spectral bandwidth of fiber laser radiation is investigated. Subsequently, compensation optics to correct the spectral phase mismatching inside the nonlinear crystal is dimensioned and tested. For the experimental study a laboratory fiber laser setup is used consisting of a seed diode and a three stage fiber amplifier. The laser delivers an average output power of up to 100 W at 1 MHz. Even below the Raman threshold the output is far away from Fourier limit, providing a nearly Lorentzian spectral shape and a temporal pulse width of 800 ps. As the bandwidth increases nearly linearly with the pump power of the third amplifier stage, this parameter could be controlled for the experiments. All conversion experiments are conducted with a moderate load of the nonlinear crystals, i.e. intensity less than 150 MW/cm2. Without compensation of the spectral phase mismatch, a maximum conversion efficiency of 15 % is attained for a Type I configuration with a 20mm long LBO crystal. Using the compensation setup 27 W of green light are obtained from 60 W infrared light at a bandwidth of 4.7 nm. Therefore the efficiency rises to 44% at the same load.

We have developed a new, frequency tripled 355 nm CW laser to produce power up to 200 mW. The noise level of the laser is 0.2% rms within an 8 MHz bandwidth and with a peak to peak noise of 2%. Side pumped Nd:YVO₄ is the gain medium. The laser mode efficiently samples the diode array pump mode. Frequency doubling and tripling is internal to the 1064 nm cavity. This paper discusses the characteristics such as power, the noise performance and the beam quality of the laser, along with some potential applications.

A compact and efficient continuous wave, single mode, diode-pumped solid state laser is reported. The laser is based on cascaded 2:nd order non-linear processes for intra-cavity frequency tripling to 355 nm wavelength using periodically poled materials. CW emission exceeding 30 mW has been reached. The total size of the laser head is 125x70x45 mm³ (LxWxH), the ring cavity itself takes an area of only 30x20 mm² (LxW).

We report a fast-switching two-component frequency-converted laser with reduced speckle visibility. A bottom-emitting passively Q-switched laser with integrated electroabsorber, folding mirror and coupling lens was successfully applied with a waveguide-type periodically poled magnesium oxide doped lithium niobate crystal to generate second harmonic light at 532 nm. Reduced speckle visibility was demonstrated when operating the laser in self-pulsating mode when compared to continuous-wave operation even when using a nonlinear crystal with narrow acceptance bandwidth of 0.24 nm @ 1064 nm. The spectral width of the infrared light was 0.33 nm in pulsed mode and 0.08 nm in continuous-wave mode resulting in visible light spectral width of 0.12 nm and 0.03 nm in self-pulsating and continuous-wave mode.

Since the first introduction of DPSS lasers at 561 nm in 2004, the power level required by some biotechnical applications has always increased. Oxxius has contributed to fulfill the demand thanks to the introduction of the SLIM-561 100mW in 2008 and of the SLIM-561 200mW and 300mW in 2009. More recently, new dyes or nano-dots have required shorter wavelengths (such as 553 nm) and new applications such as Laser Doppler Velocimetry requiring both high power and single frequency operation have appeared. In this presentation, we demonstrate how to further increase the power. 553nm and 561 nm emission are obtained by frequency doubling the 1106 nm and 1123 nm lines of Nd:YAG. The latter transitions are significantly weaker than the 1064 nm line. As a consequence, any loss in the cavity significantly increases the laser threshold. Because of the perfect alignment of the crystal interfaces and the low divergence of the intracavity beam, monolithic cavities demonstrate significantly reduced round-trip losses compared to standard cavities. Consequently, laser threshold can be dramatically reduced and the nonlinear loss, responsible for the visible emission, can easily dominate the linear losses. We have taken standard monolithic cavities of our commercial SLIM-561 products and have increased the pumping power up to 2.8 W. Yellow and Yellow-green powers have not shown any sign of saturation and 0.5 W could be achieved at both wavelengths. This results in a record 18% pump to signal optical efficiency. We have checked that the emission remained single frequency whatever the pumping power.

Single longitudinal mode visible DPSS are more and more used in devices where performance can be affected by short term (minutes) frequency drifts and hops. Long exposure holography and Raman spectrometry are applications requiring high frequency stability. Resonant external cavity frequency doubling (to generate CW deep UV) and pumping doubly resonant OPOs may be even more demanding applications in terms of frequency stability. Mechanical vibrations and thermal fluctuations are usual sources of short term frequency variations or instabilities. Monolithic ring cavities (such as NPRO) are known to solve this problem but they are quite expensive to manufacture. We will show that much simpler linear monolithic cavities used in our standard product line (SLIM-532, SLIM-550, SLIM-561 and SLIM-660) present best of class frequency stabilities compatible with the most demanding applications. Frequency tuning capabilities will be discussed and could be used in an active stabilization of the laser. Some applications can benefit from long term wavelength stability as well. Raman spectra can be monitored without control of the pump wavelength if the long term stability is good. In addition, narrow filters can be used to measure small Stokes shifts. We are monitoring several monolithic laser sources. After more than 6000 hours of operations, the wavelength shift is within 1 pm. The laser source has been restarted more than 1000 times without any change of the operating wavelength. Finally, thermal cycles do not impact the wavelength. In conclusion, we demonstrate that monolithic linear cavities are best suited for all applications requiring wavelength stability.

We report on creation of frequency doubled E-O Q-switched Nd:YAG laser lasing Single Longitudinal and Transversal mode radiation at 1319 nm (⁴F_3/2 to ⁴I_11/2 transition) at repetition rate of 10 Hz. By means of linear resonator stable redlight pulses were obtained at 660 nm having Emax = 5mJ output energy and τ = 50 ns (FWHM) pulse duration by using NCPM LBO crystal as an extra-cavity frequency doubler. Laser design incorporates particularly made fast negative feedback loop controls for pulse buildup control. It allowed obtaining much more stable laser performance as well as much shorter Optical Jitter and fast pulse buildup time. To best our knowledge, these are the first time such pulse energy, rep rate Transversal and Longitudinal mode structure ever achieved in compact flashlamp pumped E-O Q-Switched laser operating at 1319 nm.

Optically Pumped Semiconductor Lasers - OPSLs - have been introduced in 2001. Their unique features such as power scalability and wavelength flexibility, their excellent beam parameters, power stability and reliability opened this pioneering technology access to a wide range of applications such as flow cytometry, confocal microscopy, sequencing, medical diagnosis and therapy, semiconductor inspection, graphic arts, forensic, metrology. This talk will introduce the OPSL principles and compare them with ion, diode and standard solid state lasers. It will revue the first 10 years of this exciting technology, its current state and trends. In particular currently accessible wavelengths and power ranges, frequency doubling, ultra-narrow linewidth possibilities will be discussed. A survey of key applications will be given.

In recent years, optically pumped semiconductor disk lasers (OPSDLs) have attracted increasing interest due to their capability of delivering simultaneously high output power and excellent beam quality. Here we report on group-III-Sbbased OPSDLs allowing to cover the wavelength range around and above 2 μm. First the current state-of-the-art and recent progress for OPSDLs emitting in the 2.0-to-2.3 μm spectral range is presented, which includes power scaling through the use of multiple gain elements and as well as spectral tuning and line width narrowing, exploiting in both cases the versatility of the external cavity concept. Then, results on III-Sb-based OPSDLs emitting at 2.8 μm with a cw output power of up to 0.12 W and a peak output power in pulsed mode of >0.5 W, both data referring to roomtemperature operation, are presented. In both cases, the active region of the OPSDL chip consists of compressively strained GaInAsSb quantum well (QW) layers embedded between AlGaAsSb barrier and pump-light-absorbing layers. The emission wavelength is controlled by adjusting the composition of the quaternary QW material. The active region is grown on top of an epitaxial GaSb/AlAsSb Bragg mirror. For efficient heat extraction, SiC intra-cavity heat spreaders were bonded to the surface of the cleaved laser chips. An N-shaped resonator with one OPSDL chip acting as an end mirror and the second OPSDL chip as a folding mirror was used for power scaling, while a V-shaped resonator configuration with a birefringent tuner inserted into the collimated beam path of the resonator was employed for wavelength tuning. Optical pumping was achieved by standard fiber-coupled diode laser modules emitting at 980 nm.

We report the performance and characteristics of a GaInNAs-based tunable fibre vertical-cavity surface-emitting laser emitting at a wavelength of ~1200nm which may find application as a source in gasoline octane detection. The device, which is pumped through the fibre by 810nm diodes, can emit more than 0.3mW of output power and is tunable over 17nm around 1197nm.

We report a low-temperature 1.3μm AlGaInAs quantum-well laser pumped by a 1.06μm active Q-switched laser quenched by a low-temperature vacuum system. An average power of 330mW is achieved at temperature as low as 233K compared to the average power of 50mW obtained at room-temperature without cooling device both at pumping repetition rate of 30 kHz. And the average rate of gain peak shift was found to be 0.47 nm/K between 293-133 K.

We report a GaInNAs/GaAs-based disk laser producing 7 W output power at 1180 nm wavelength at a temperature of 15 °C. The laser generated more than 5 W of output power when it was forced to operate with a narrow spectrum at 1178 nm. The gain mirror was grown using a molecular beam epitaxy reactor and it comprised 10 GaInNAs QWs and a 25.5- pair GaAs/AlAs distributed Bragg reflector.

Intra-cavity frequency doubling (ICFD) of electrically and optically surface emitting diode lasers in the near IR region become more interesting [1-3] and will have an enormous impact in the display market. In this paper, Watts-level green laser is generated by ICFD of multi-emitters laser bar using a MgO-doped periodically poled lithium niobate (MgO: PPLN) bulk crystal, which has the potential to be scalable to high production volumes and low costs with immense implication for laser-based projection displays.

Yb:YAG ceramic laser materials, fabricated by vacuum sintering technology, were optically investigated within different laser set-up configurations. The established nanopowder vacuum sintering process shows good potential for mass fabrication of multicomposite ceramic laser materials with different dopant concentrations. 5%, 7%, 10% single dopant and 7%/20% core-cladding multi-composite Yb:YAG materials were fabricated and investigated. The highest measured slope efficiency, for the composite ceramic laser materials was 81%, at 1030 nm emission wavelength, similar to Yb:YAG single crystals.

Analyzed are thermally induced aberrations in optical beams propagating through solid-state laser media. Several geometrical configurations are considered: cylindrical rod, thin disk and slab. Predicted are thermally-induced optical effects in the temperature range of 77 - 770K. The analysis is based on an analytical solution to the problems of nonlinear heat transfer and material stressstrain field. Predictions are made for the temperature field, stress distribution, refractive index profile, ray trajectories, focal lengths, beam phases and aberrations. Most optimistic results are obtained for thin disk configuration in which the disk is attached to a heatsink and to a conducting cap on either facet.

We report the highest average power modelocking using the nonlinear mirror (NLM) technique of a novel bounce geometry laser with excellent beam quality. A diode-side pumped Nd:YVO4 slab lasing at 1064nm was used in a bounce-oscillator configuration employing a stigmatic spatial TEM00 design. Incorporation of a type-I phase-matched BiBO nonlinear crystal (NLC) in a NLM configuration produced 12W of self-starting, continuous-wave (CW) modelocking with pulse duration 14ps and repetition rate 110MHz. This is the highest power recorded using the NLM technique and was operated with high long-term stability. The system exploits the capacity of NLM modelocking over SESAM modelocking, for sustaining higher average and peak powers without onset of optical damage occurring.

The pump beam generation line of an optical parametric chirped pulse amplifier (OPCPA) system providing few-cycle pulses with energy in the millijoule range at repetition rates up to 10 kHz is presented. The overall design of the system is briefly discussed including stretching-compressing and parametric amplification. The main emphasis is on the requirements on the pump beam for successful pumping of a parametric amplifier. Aspects of the design of the multistage hybrid amplifier line are detailed and performances of each stage are presented.

Chirped Bragg Gratings (CBGs) recorded in photo-thermo-refractive (PTR) glass have been successfully used as ultrashort pulse stretchers and compressors in a variety of solid-state and fiber chirped pulse amplification (CPA) laser systems. Compared to traditional pairs of surface gratings, CBG-based stretchers and compressors offer significant advantage in compactness and robustness. They are insensitive to polarization, require virtually no alignment and can handle high average and peak power. At the current technology stage PTR-glass CBGs can provide up to 30 nm spectral bandwidth and up to 300 ps stretched pulse duration. In this paper we propose a concept of sectional CBGs, where multiple CBGs with different central wavelengths recorded in separate PTR-glass wafers are stacked and phased to form a single grating with effective thickness and bandwidth larger than each section. We present results of initial experiment in which pulses from a femtosecond oscillator centered at 1028 nm are stretched by a 32-mm thick CBG to about 160 ps and recompressed by a monolithic 32-mm CBG with 11 nm bandwidth and by a sectional CBG with two 16-mm thick sections each having ~ 5 nm bandwidth and offset central wavelengths: 1025.5 and 1031 nm. In both cases, compressed pulse duration of 350-400 fs, ~ 1.1 × transform-limit was obtained. These results allow CBG-based pulse stretchers and compressors with high stretch ratio and wide bandwidth to be constructed from multiple sections.

In this paper, I present the design of a dispersive delay generator that is capable of producing 1 ns per 1 nm dispersive delay in a compact footprint. The path length delay produced by a grating and free space is amplified by introduction of a total internal reflection surface operating at an angle of incidence near the critical angle. Both positive and negative amplification may be realized in this technique by changing the orientation of the angular dispersion amplifier optic. The device is not wavelength sensitive and it uses bulk optics, which can handle high average power and high peak power. Because this method produces significant pulse stretching for a given pulse bandwidth, it may lead to higher peak power laser sources in the future. This delay generator has applications in pulse compressor, pulse stretcher or pulse shaper in chirped pulse amplification and high-resolution time gated spectroscopy. The delay generator can also be fabricated on silicon wafers for photonics integrated circuits.

Photons are non-interacting entities. Light beams do not interfere by themselves. Light beams constituting different laser modes (frequencies) are not capable of re-arranging their energies from extended timedomain to ultra-short time-domain by themselves without the aid of light-matter interactions with suitable intra-cavity devices. In this paper we will discuss the time-gating properties of intra-cavity "mode-locking" devices that actually help generate a regular train of high energy wave packets.

In this work, resonant diode pumping has been demonstrated for Q-switched and CW Er:YAG solid state lasers (SSLs) at eye-safe wavelengths. Resonant pumping was realized by using high spectral brightness 1470 nm laser diodes. An efficient 1645 nm CW laser with output power >3.5 W in the TEM₀₀ mode was demonstrated. More than 11 mJ of output pulse energy in the TEM₀₀ mode has been achieved for Q-switched operation at 20Hz repetition rate. M² of the output beam was better than 1.5 over the entire range of output pulse energies. We achieved an output peak power of ~400 kW.

An efficient, compact diode-laser-pumped 2.94μm Er:YAG laser operating at 1.5 W continuous output power in a TEM₀₀ beam with M²<1.2 has demonstrated pulsed operation in the quasi-cw regime with energies up to 9 mJ. Power scaling and output beam fiber-coupling at 85% efficiency in a hermetic package will be described.

Efficient powerful laser sources in the two-micron regime are in demand for many applications in the areas of remote-sensing, defense, medicine, and materials interactions. Dramatic progress has been demonstrated in cw-power scaling of 2-micron fiber lasers; however, power-scaling in a pulsed mode of operation is limited by nonlinear effects and a relatively low damage-threshold-power. To fully capitalize on the potential advantage for high pulse-energies of the conventional 'bulk' 2-micron solid-state laser, extreme measures have to be taken to mitigate the three-level character and thermal effects in the laser medium resulting from heat generated during the pump cycle. Alleviation of these detrimental effects can be achieved by simply cooling the gain medium to cryogenic temperatures, benefitting from lower population in the terminal laser levels, and a large increase in the thermal conductivity, with a proportional decrease in the thermo-optic coefficient (dn/dT) and expansion coefficient. Combined these result in a massive reduction in thermo-optic aberrations. In this paper, we report on improved measurements of the spectroscopic properties of Ho:YAG at various temperatures between room and liquid nitrogen temperatures, utilizing a multi-Watt Tm-fiber ASE source we have been able to properly identify the absorption features of interest with an accuracy better than 0.2nm. Results for other Ho-doped gain media will be discussed and the latest performance of a cooled 2-micron Ho:YAG laser in-band pumped by a narrow-linewidth Tm-fiber laser presented.

A tunable master oscillator power amplifier (MOPA) fiber laser system based on thulium doped silica fiber designed for investigation of multi-kilometer propagation through atmospheric transmission windows existing from ~2030 nm to ~2050 nm and from ~2080 nm to beyond 2100 nm is demonstrated. The system includes a master oscillator tunable over >200 nm of bandwidth from 1902 nm to beyond 2106 nm producing up to 10 W of linearly polarized, stable, narrow linewidth output power with near diffraction limited beam quality. Output from the seed laser is amplified in a power amplifier stage designed for operation at up to 200 W CW over a tuning range from 1927 - 2097 nm. Initial field tests of this system at the Innovative Science & Technology Experimental Facility (ISTEF) laser range on Cape Canaveral Air Force Station, Florida will be discussed. Results presented will include investigation of transmission versus wavelength both in and out of atmospheric windows, at a variety of distances. Investigations of beam quality degradation at ranges up to 1 km at a variety of wavelengths both in and out of atmospheric transmission windows will be also presented. Available theoretical models of atmospheric transmission are compared to the experimental results.

This work is focused on study and optimization of diffusion of Fe in ZnSe from the metal phase, comparative spectroscopic characterization of kinetic properties of Fe:ZnSe crystals with a wide range of concentrations, and energy scaling of the Fe:ZnSe gain-switched laser. Iron doping of ZnSe polycrystals was performed by thermal diffusion from the iron film made by thermal evaporation process. Special cleaning of the ZnSe surfaces and optimization of the ZnSe substrate temperature and the rate of Fe evaporation resulted in significant enhancement of the diffusion process and enabled fabrication of high optical density crystals with Fe concentration up to 2x10²⁰ cm^-3. The diffusion coefficient and diffusion length of iron in ZnSe at 1000°C were estimated as 2.1x10^-9 cm²/s and 1.3 mm, respectively. We report a detailed absorption, emission, and kinetics of fluorescence of Fe:ZnSe spectroscopy performed over a broad range of Fe concentrations (5x10¹⁸ - 2x10²⁰ cm^-3) and temperatures (14-300K) under direct 2.78μm excitation.

PWO crystals were grown using the Czochralski method with concentrations from 0.2% to 4%. The polarized optical absorption, emission, and kinetics of fluorescence were measured at room temperature and low (14K) over a spectral range of 0.2 to 3 microns. The spectroscopic data were then used to calculate the absorption and luminescence cross sections. The maximum absorption cross at ⁴I_13/2→⁴I_15/2 transition section was calculated to be σ=8.0x10^-21 cm² at 1500 nm and E||z polarization of incident light. The measured luminescence lifetime at this transition was 5.6 ms.

The objective of this work was to develop a compact and efficient Tm-fiber-Ho:YAG, hybrid laser passively Q-switched by Cr:ZnSe saturable absorber. We used a folded semi-hemispherical 10 cm long cavity with a plane output coupler and a 0.5 m concave high reflector. In these experiments we studied the performance of two high optical quality Cr:ZnSe crystals as saturable absorbers with initial transmissions of 93.9% and 70% at 2.1 μm. With the 93.9% transmission crystal, passive Q-switching was realized with a maximum output power of 5 W, pulse energy of 0.5 mJ, pulse duration of 150 ns, and Q-switched-to-CW-mode extraction efficiency of 60%. With the 70% transmission crystal, passive Qswitching was achieved with a 75% Q-switched-to-CW-mode extraction efficiency, pulse energy of 3 mJ, and duration of 7ns. The laser demonstrated sustained damage-free, TEM000 operation with 0.5 MW of peak power showing promise for applications requiring high-peak-power, diffraction-limited beams, and single-frequency regimes of operation.

We present compact, highly-efficient, widely-tunable CW lasers based on Cr²⁺:ZnS and Cr²⁺:ZnSe gain media longitudinally pumped by a single-emitter, 1.5 W, 1685 nm InP semiconductor laser. The Cr2+:ZnSe laser demonstrates 35% slope, and 24% real optical efficiency, respectively, up to 400 mW of output power, and is tunable from 2200 to 2700 nm. The Cr²⁺:ZnS laser shows 44% slope, and 31% real optical efficiency, respectively, up to 500 mW of output power, and is tunable over 2100-2700 nm. The single-emitter diode pumping of chromium-doped chalcogenides allows for fabrication of middle-infrared tunable laser sources where low- or mid-range output powers are sufficient, while low footprint and miniature packaging are strictly required. In our presentation we will discuss the laser design issues specific to diode pumping, demonstrate the performance of the Cr:ZnS and Cr:ZnSe laser systems with different transmissions of the output couplers, describe several approaches for convenient wavelength tuning, and perform a comparison of diode pumping efficiency to that of fiber-laser pumping.

We demonstrate a high-power (7.5 W) polycrystalline Cr²⁺:ZnSe CW laser system utilizing an astigmaticallycompensated Kogelnik-configuration master oscillator and a normal-incidence slab power amplifier demonstrating over 2X gain. Experimental results are compared with an improved theoretical model of amplification in this type of system.

The issue of microlasers and micro-chip laser devices, passively Q-switched and doped with rare earth lasing ions is well established. The various components of such monolithic lasers are diffusion-bonded to the gain medium or alternatively separated. Laser performance of several configurations based on various hosting crystals, as well as analytical modeling of the Q-switching process will be presented and discussed. The effect of various types of Q-switches on the laser performance will be presented and analyzed.

We have realized a single frequency Q-switched Nd:YAG laser with precisely controllable lasing time and thus enabled synchronization of multi-laser systems. The use of injection seeding to the slave ring oscillator results in unidirectional Q-switched laser oscillation with suppression of bidirectional Q-switched oscillation that otherwise would be initiated from spontaneous emission if the seeding laser is not present. Under normal condition, the cavity is high in loss during the pumping period; then a Pockels cell opens the cavity to form the pulse build up, with a second Pockels cell to perform cavity dumping, generating the Q-switched pulse output with optimized characteristics. The two Pockels cells can be replaced by a single unit if an adjustable gated electrical pulse is applied to the Pockels cell in which the pulse front is used to open the cavity and the falling edge to dump the laser pulse. Proper selection of the pump parameters and Pockels-cell gating enables operation of the system in a mode in which the Q-switched pulse can be formed only under the seeding condition. The advantage of the realized regime is in stable laser operation with no need in adjustment of the seeded light wavelength and the mode of the cavity. It is found that the frequency of the Q-switched laser radiation matches well to the injected seeded laser mode. By using two-stage amplifiers, an output energy better than 300 mJ has been achieved in MOPA configuration without active control of the cavity length and with pulse width adjustability from several nanoseconds to 20 ns. The Q-switched oscillator operates not only at precisely controlled firing time but also can be tuned over wide range. This will enable multi-laser systems synchronization and frequency locking down each other if necessary.

We report on a diode-pumped, monolithic and passively Q-switched microchip laser generating 200 ps pulses at a wavelength of 1064 nm with a repetition rate of up to 2 MHz. By varying the pump intensity we can change the repetition rate in the range from 100 kHz to 2 MHz and achieve pulse energies from 400 nJ to 130 nJ respectively, while still maintaining singe transversal and longitudinal mode operation. The microchip laser is based on Nd:YVO₄ as the gain medium and a SESAM as the passive Q-switch. It is monolithically bonded with spin-on-glass as the bonding agent. The timing jitter was measured to be shorter than 40 ns for low and 2.5 ns for high repetition rates resulting in a relative timing jitter smaller than 1%. The output of this type of laser can be amplified easily to the range of few tens of watts using only one amplification stage based on a photonic crystal fiber. The combination of picoseconds pulses, high average power and high repetition rates makes this system very interesting for many applications like e.g. micromachining with high processing speed and nonlinear frequency conversion with high average power.

A diode-pumped frequency-doubled Nd:YAG laser has been demonstrated which emits 7.2 W of 532-nm radiation in the CW mode as well as 23 ns, 2.7 mJ pulses at a repetition rate of 10 kHz in the Q-switched mode. The high power in both modes was achieved by intra-cavity second harmonic generation in lithium triborate. The nonlinear output coupling through SHG in this laser causes a factor of 5.7 change of intra-cavity power between the CW and the Q-switched mode. The resulting variation of the thermal lens in the laser rod makes it challenging to maintain a geometrically stable cavity in both operation regimes, which is essential for diffraction limited beam quality. Diffraction limited beam quality with M² values of less than 1.1 in the CW and less than 1.2 in the Q-switched regime was achieved by a novel dual-stabilityrange cavity-design. This design provides geometrically stable cavity configurations in both operation regimes, which are separated by an unstable region. This cavity makes it possible to switch between the two operation regimes without any moving components.

To address the issue of pulse-to-pulse timing jitter in a passively Q-switched Cr:YAG/Nd:YAG laser, we have developed a technique for optical triggering, where the energy from a single bar diode was used to bleach a thin sheet within the Cr:YAG saturable absorber from a direction orthogonal to the lasing axis. A strong anisotropy for bleaching effect was observed; with appropriate polarization of the bleaching light the transmission through the saturable absorber was increased from 45% to 63%. This technique was applied to a monolithic Cr:YAG/Nd:YAG laser operating under steady state conditions. By placing the Q-switched pulse at the time corresponding to the steepest slope for change in transmission during bleaching, which occurs ~1μs after the bleaching diode trigger, we measured an 12.5X reduction in the pulse-to-pulse timing jitter, from 100ns for free running operation to 8ns with optical triggering.

Small fibre connectors capable of handling medium powered lasers are available on the market from multiple suppliers. Typical connector types are the SMA905 and LD80. The capability to handle power losses, for example radiation falling outside the fibre core is, due to the small size and restrictive design, limited. A new type of SMA fibre connector, designed for high-power loss capability will be presented. The basic principle is to strip off the losses in terms of radiation rather than being absorbed in the fibre connector. The radiation is instead absorbed in the female connector housing or within the laser housing, where it can easily be cooled away. In this paper both the principles and measurement of power capability are presented. Furthermore, in order to give a perspective of the available high-power SMA fibre connectors on the market today, a comparison between the best competitive products is presented.

Although fiber delivery of 25 fs laser pulses were recently shown possible reported results are restricted to 1 to 2 m single-mode optical fiber due to the high amount of group delay dispersion, guiding losses or fiber nonlinearities. On the other hand conceivable applications of ultrashort laser pulses in inhospitable environment, their use for security or even telecommunication purposes require optical pulses to be delivered over much longer fiber distances. Here we demonstrate 160 fs laser pulses from a Ti:Sapphire laser travelling over 45 m optical fiber. In theory even 130 fs can be sent through 50 m single-mode fiber with the herein described technique.

Circularly polarized, 25 fs 5 mJ pulses generated at a repetition rate of 1 kHz from a two-stage chirped pulse amplifier were spectrally broadened by means of nonlinear propagation in a Ne-filled hollow fiber. Subsequent compression with dispersive mirrors resulted in 5.2 fs, 1.7 mJ pulses. After recompression an all-reflective achromatic phase retarder was used to obtain linear polarization.

The basic principles of faraday isolation and thermal effects in the rod geometry under high power operation have been reviewed. The temperature dependency of the verdet-constant and the magnetization of NdFeB have been identified as the limiting factor of isolation ratio for an unchilled high power isolator device. The focal shift due to the isolator with rod-geometry is independent from beam diameter and strongly depending on beam quality. A highly compact isolator for unpolarized radiation up to 400 W fundamental mode for industrial application surrounding with minimal thermal lensing has been developed. At 400 W and 10-40 °C a transmission of 95-97 %, an isolation larger 20 dB, a thermal focus shift of less than 2 rayleigh ranges and a M² smaller than 1.2 have been achieved.

We used 9.9-ns, single-longitudinal-mode, TEM00 pulses tightly focused to an 8-micron radius spot to measure single-shot and multiple-shot damage thresholds of pure and Nddoped ceramic Yttrium Aluminum Garnet (YAG), and of pure, Nd-doped, Cr-doped, and Yb-doped crystalline YAG. By tightly focusing the laser beam, we kept the damage threshold powers below the SBS threshold, and minimized the effect of self focusing. The size of the focus spot was measured using surface third harmonic generation. We found both single-shot and multiple-shot damage thresholds to be deterministic. At the single-shot damage threshold in YAG, breakdown always occurs on the trailing edge of the laser pulse. However, for multiple-shot damage threshold, breakdown occurs at the peak of the n^th laser pulse. Our measured damage thresholds for doped and undoped, ceramic and crystalline YAG range from 1.1 to 2.2 kJ/cm². We also report some damage morphologies in crystalline YAG.

STED microscopy has gained recognition as a method to break the diffraction limit of conventional light microscopy. Despite being a new technique, STED is already successfully implemented in life science research. The resolution enhancement is achieved by depleting fluorescent markers via stimulated emission. The performance is significantly dependent on the laser source and the fluorescence markers. Therefore the use of novel fluorescent markers in conjunction with the right laser system was the main focus of our research. We present new developments and applications of STED microscopy, unraveling structural details on scales below 90nm and give an overview of required specifications for the solid state laser systems.

Recent advances in the design of gain modules for diode-pumped solid-state lasers have allowed the manufacture of high-powered Q-switched products. The high available pulse energy and good mode quality enable highly efficient harmonic conversion, enabling the generation of several hundred watts of average power at a wavelength of 532nm. Among the applications for which this class of product may be suited is the rapid drilling of small-diameter holes in aluminum sheet. To investigate this application, plates of several aluminum alloys were drilled under a variety of conditions. The drilled plates were sectioned and subjected to analysis by optical metallography. The initial results indicate ways in which the process may be optimized.

TRUMPF presents the flexibility of the thin disk laser technology in this paper. Used on CW lasers, short pulsed laser based on cavity-dumping including intracavity frequency conversion and ultrafast MOPA systems, lasers based on disk technology are important tools for a variety of industries. By employing a cavity-dumped thin disk laser, a wide range of pulse durations and up to 750 watts is available. In addition, TRUMPF's TruMicro 7250 combines this technology with intracavity frequency conversion. The compact generation of the TruMicro Series 5000 offers six picosecond pulse duration and 50 W average power.

INNOSLAB lasers are characterized by: short pulse length and high peak power, high pulse repetition rate, high beam quality and flexibility in beam profile, from circular beam profile, through line shaped one dimensional Top-hat, to two dimensional top-hat with rectangular or square cross section. Their tailor able beam profiles open for INNOSLAB laser a variety of applications with high energy efficiency, such as glass milling, parallel scribing, high throughput ablation, particle imaging velocimetry and pumping of dye lasers.

In this work, we present a continuous-wave yellow laser operating at 586.5nm based on self-Raman conversion in Nd:GdVO₄. We report more than 4.2W CW and 5.5W instantaneous output at a 50% duty cycle regime. This is the highest CW power of a self-Raman laser to be reported so far. We also demonstrate the integration of this laser cavity into a console for applications in ophthalmology, and more specifically for retinal photocoagulation therapies.

We report on oscillator-amplifier system based on two highly doped 2.4 at. % crystalline Czochralski grown Nd:YAG crystals in a diode pumped bounce geometry configuration under quasi-continuous pumping. The oscillator was passively mode-locked by the semiconductor saturable absorber in transmission mode. The output pulse train consisted of 5 pulses with total energy of 270 μJ and pulse duration of 75 ps. The output train from the oscillator was amplified to the energy of 1 mJ by single pass amplifier.

The lead thiogallate (Dy:PbGa₂S₄) crystal doped with trivalent dysprosium ions was used as a laser active medium for obtaining radiation in mid-IR spectral region. To prove in-band pumping, the Er:YAP laser generating 1.66 μm radiation was used. This radiation was focused by CaF2 lens (f = 100 mm) on the investigated Dy:PbGa₂S₄ crystal placed inside the resonator formed by an in-coupling flat-dichroic mirror with low reflectivity at pumping wavelength and with high reflectivity within the 4-5 μm spectral range, and by an out-coupling concave mirror (500 mm curvature) with reflectances of 86%, 88%, 89%, and 93% at 4325 nm. Three Dy:PbGa₂S₄ active crystals were investigated. The Dy:PbGa₂S₄ laser was working at room temperature without any cooling. The maximal reached output energy was as high as 275 μJ for the optimal mirror reflectance and the best Dy:PbGa₂S₄ crystal. The incident pumping energy was 132 mJ. The measured output radiation wavelength was 4332 nm with the spectral width of 62 nm. From the point of efficiency it was recognized that the in-band pumping directly into ⁶H_11/2 level results in decrease of lasing threshold and increase of slope efficiency.

Cr:ZnSe laser coherently longitudinally pumped with Tm:YAP microchip laser was realised. The pumping laser consisted of Tm:YAP crystal (3x3 mm) with resonator mirrors deposited directly on its faces (on rear face the dielectric layer with high reflectance for 1998 nm wavelength and high transmittance for 790 nm pumping radiation wavelength; on output face the dielectric layer with reflectance 97% at 1998 nm wavelength). The maximal output power was 5.5 W and the generated radiation wavelength was 1998 nm. The main advantage of this pumping was stable and still output without relaxation spikes (non-spiking). The Tm:YAP laser radiation was collimated and focused by the set of two CaF2 lenses. The pumping beam spot diameter inside the Cr:ZnSe crystal was 300 μm. The Cr:ZnSe laser resonator consisted of flat rear mirror (HT at 1998 nm and HR at 2100 - 2900 nm) and curved output coupler (r = -150 mm, R = 95% at 2100 - 2700 nm). The maximal output energy of stable radiation was 4 mJ (pulse duration 10 ms, repetition rate 10 Hz). For wavelength tuning the Lyott filter (quartz plate under Brewster angle) was placed between the Cr:ZnSe crystal and output coupler. The generated radiation wavelength was continuously tunable from 2246 - 2650 nm.

We characterize the optical bistability observed in a diode-pumped Yb:GdVO4 laser operating in the continuous-wave regime at room temperature. The bahavior of this laser is rather complex as a result of the coexistence and switching between the σ and π polarization states characteristic of this uniaxial crystal. The bistability range extends over more that 1 W in terms of absorbed pump power while the output power at the up-threshold increases abruptly from 0 to 0.71 W. We analyze in more detail the influence of the Yb concentration, the crystal thickness, the output coupling, and the cavity configuration on the bistability.

In this paper we report on comparison of laser results reached by Pr-doped oxide and fluoride crystals under GaN-laser diode pumping at room temperature. As oxide and fluoride crystal representatives, Pr:YAlO₃ (Pr:YAP) and Pr:LiYF₄ (Pr:YLF) crystals were used. Pumping was accomplished by multimode GaN-laser diodes capable of providing output powers of up to 1W at wavelengths corresponding with Pr:YAP and Pr:YLF absorption peaks. For both samples, efficient stimulated emission in the red laser transition has been demonstrated, and laser results regarding the output power, threshold, and slope efficiency with respect to the absorbed power have been compared.

Temporal jittering has been problem in industrial application of passively Q-switched laser. To address this, we tried two methods. The first is preventing pump laser absorption in the Cr:YAG, which is used for saturable absorber. The saturation of the Cr:YAG should be affected by intracavity photons generated by stimulated emission in Nd:YVO₄ crystal for reliable Q-switching operation. To prevent pump absorption, we applied 808 nm mirror coating on the Cr:YAG crystal. This coating also enhanced efficiency of pump laser utilization because the reflected beam was reabsorbed in the Nd:YVO₄ crystal. As the second method, we applied pulsed current to the laser diode. The Q-switched laser is generated only after the pulse diode laser beam was absorbed in the Nd:YVO₄ crystal. The pulsewidth of current pulse was carefully adjusted for Q-switched output pulse per each pump pulse. Air circulation is reduced by contacting crystals together and applying output coupler coating on the Cr:YAG crystal surface.

Er:YAlO₃ crystals as active materials for coherent resonant pumping by Er:glass laser were investigated. The Er:YAP rods had 1 at.% concentration of Erbium/Yttrium (Er/Y) and were 10 mm or 20 mm in length. The output characteristics of the designed and constructed lasers, i.e., the spatial beam structure, temporal profile, and efficiency were derived. For 555 mJ incident Er:glass pump energy (1535 nm wavelength), the generated output energy was 20 mJ at the lasing wavelength 1623 nm. For comparison, three Er:YAG crystals with various Er/Y concentrations and lengths were also evaluated under the same conditions. These lasers generated energy at 1648 nm. The main advantage of resonantly pumped lasers is low quantum defect related with lower cooling demand. Therefore, with the used repetition rate 0.5 Hz, it was not necessary to cool the active crystals.

Compact Q-switched diode-pumped laser, emitting radiation at eye-safe wavelength 1444 nm, was studied. This laser was based on composite crystal (diameter 5mm) consisting of 4mm long Nd:YAG active medium diffusion bonded with 1mm long V:YAG saturable absorber (initial transmission @ 1444nm 94 %). The laser resonator mirrors were directly deposited onto the composite crystal surfaces. These mirrors were designed to ensure emission at 1444nm and to prevent parasitic lasing at other Nd³⁺ transmissions. The pump mirror (R < 10% for pump radiation @ 808 nm, R < 2% @ 1064 nm, R < 15% @ 1330 nm, HR @ 1444 nm) was placed on the Nd³⁺-doped YAG part. The output coupler with reflectivity 94% for the generated wavelength 1444nm was placed on the V³⁺-doped part (R < 5% @ 1064 nm, R < 15% @ 1330 nm). Temperature dependence of giant pulse energy and length was studied independently on pumping pulses duty cycle. It was found that for constant duty cycle 1% and for crystal holder temperature rise from 8.2 up to 43.2 °C the pulse width dropped from 31 to 5.1 ns and pulse energy rose from 17 to 57 μJ. This represents a pulse peak power increase from 0.54 up to 11kW. From a mathematical model of passively Q-switched laser it follows that this behaviour can be explained by temperature caused increase of ground-state absorption and ground-state to excited-state absorption ratio (FOM) of V:YAG saturable absorber at wavelength 1444nm in case if FOM ~ 1.

This report for the first time presents the results of parameter optimisation of ultra-narrow-linewidth frequency-doubled CW Ti:Sapphire lasers pumped with 12.5-18.5 W of 532-nm light. Proposed laser systems are designed for atom cooling and provide output radiation power of more than 1.5 W at 399/401 nm (Ytterbium/Erbium) and more than 1 W at 421 nm (Dysprosium) pumped at 18.5 W. The output power of single-frequency radiation at 421 nm achieved during the present work is the highest published to-date for a commercially available system achieving a 10 kHz linewidth.

LIBS (Laser Induced Breakdown Spectroscopy) systems are capable of real-time chemical analysis with little or no sample preparation. A Q-switched laser is configured such that laser induced plasma is produced on targeted material. Chemical element line spectra are created, collected and analyzed by a fiber spectrometer. Line spectra emission data is instantly viewed on a head mounted display. "Eye-safe" Class I erbium glass lasers provide for insitu LIBS applications without the need for eye-protection goggles. This is due to the fact that Megawatt peak power Q-switched lasers operating in the narrow spectral window between 1.5um and 1.6um are approximately 8000 times more "eye-safe" than other laser devices operating in the UV, visible and near infrared. In this work we construct and demonstrate a LIBS system that includes a hand held eye-safe laser gun. The laser gun is fitted with a micro-integrating sphere in-situ target interface and is designed to facilitate chemical analysis in remote locations. The laser power supply, battery pack, computer controller and spectrophotometer components are packaged into a utility belt. A head mounted display is employed for "hands free" viewing of the emitted line spectra. The system demonstrates that instant qualitative and semi-quantitative chemical analyses may be performed in remote locations utilizing lightweight commercially available system components ergonomically fitted to the operator.

The complex behavior of the optical wave in laser resonators requires a comprehensive model of thermal lensing and the dynamic, 3-dimensional behavior of the laser beam. To this end, we perform a combined finite element analysis (FEA) of the optical wave and of thermal lensing. Here, the simulation of the optical wave is the most challenging task. Therefore, we also discuss another method, Dynamic Multimode Analysis, which is suitable for a wide range of lasers. Finally, we present a complex heat model in order to analyze the interaction of heat generation, thermal lensing, laser dynamics, and the beam profile.

We report on the 5 μm emission characteristics and energy transfer properties of Tb³⁺ doped KPb₂Br₅ and Nd³⁺ doped KPb₂Br₅ sensitized by Tm3+ ions. A series of co-doped samples of Tm,Tb: KPb₂Br₅ and Tm,Nd: KPb₂Br₅ samples were prepared from purified starting materials of PbBr₂, KBr, and rare earth halides. Resonant excitation into the ³H₆ → ³F₄ absorption transition of Tm³⁺ at ~1760 nm resulted in an enhanced 5 μm emission from Tb³⁺ and Nd³⁺ ions in Tm,Tb: KPb2Br5 and Tm,Nd: KPb₂Br₅, respectively. The existence of energy transfer between Tm → Tb and Tm → Nd was further evidenced by the quenching of the emission decay times of the ³F₄ → ³H₆ transition of Tm³⁺ in doubly doped Tm,Tb: KPb₂Br₅ and Tm,Nd: KPb₂Br₅ compared to singly doped Tm: KPb₂Br₅.

In this paper the practical realization of a single frequency, monolithic diode pumped Nd:YVO4/YVO4/KTP microchip laser operating at 532nm is presented. The optical crystals formed the laser resonator were bonded together with UV curable adhesive. Elementary analysis of the single mode operation of such a laser configuration is presented. Period of the Lyot filter, temperature mode-hop free range of designed laser was calculated. The single frequency operation has been obtained in a birefringent filter, where an YVO₄ beam displacer acts as an ideal polarizer. We have obtained stable single frequency operation, in the two spectral ranges around 1064nm. Investigation of the single frequency operation range shifting with pump power was done. Experimental results are in good agreement with theoretical analysis. The laser operated with output power up to 85mW at 532nm. The total optical efficiency (808nm to 532nm) was 9%. The beam has a Gaussian profile and the M2 parameter was at the level of 1.2.