This PDF file contains the front matter associated with SPIE Proceedings Volume 10123, including the Title Page, Copyright information, Table of Contents, and Conference Committee listing.

GaAsBi offers the possibility to develop near-IR semiconductor lasers such that the spin-orbit-split-off energy (ΔSO) is greater than the bandgap (Eg) in the active region with lasing wavelengths in the datacom/telecom range of 1.3-1.6 μm. This promises to suppress the dominant efficiency-limiting loss processes as Auger recombination, involving the generation of “hot” holes in the spin-orbit split-off band (the so-called “CHSH” process), and inter-valence band absorption (IVBA), where emitted photons are re-absorbed in the active region, thereby increasing the internal optical losses and negatively impacting upon the laser characteristics being responsible for the main energy consumption. In addition to growth and fabrication processes refinement, a key aspect of efforts to continue the advancement of the GaAsBi material system for laser applications is to develop a quantitative understanding of the impact of Bi on key device parameters. In this work, we present the first experimental measurements of the absorption, spontaneous emission, and optical gain spectra of GaAsBi/AlGaAs QW lasers using a segmented contact method and a theoretical analysis of these devices, which shows good quantitative agreement with the experiment. Internal optical losses of 10-15 cm-1 and peak modal gain of 24 cm-1 are measured at threshold and a peak material gain is estimated to be 1500 cm-1 at current density of 2 kA/cm-2, which agrees well with the calculated value of 1560 cm-1. The theoretical calculations also enabled us to identify and quantify Bi composition variations across the wafer and Bi-induced inhomogeneous broadening of the optical spectra.

Ga(AsBi) quantum well (QW) active regions are an alternate to dilute-nitride QWs for achieving lasers in the telecom wavelength regions (λ~1.3-1.55μm) on GaAs substrates. Ludewig et al first reported the successful operation of Ga(AsBi) single quantum well laser in 2013 [1] with low threshold current densities, Jth=1.56kA/cm2 where (AlGa)As was used as a barrier material for low Bi-content QWs to improve the electron confinement in the conduction band and reduce thermally activated carrier leakage from the QW. We implement here the use of tensile-strained Ga(AsP) as a QW barrier material, providing carrier confinement as well as potential for strain-balancing. Laser structures employing a single GaAs0.976Bi0.024 quantum well (SQW) with either GaAs0.8P0.2, Al0.15Ga0.85As, or GaAs barrier materials were grown by MOVPE on a nominally singular (001) GaAs substrate Ridge waveguide lasers, 25μm-wide and 1mm-long ridge, were fabricated and characterized under pulsed current conditions. The threshold current densities for devices are 5.9kA/cm2 and 5.8kA/cm2 for GaAsP barriers and Al0.15Ga0.85As barriers respectively, with a lasing wavelength of 960nm. Devices with GaAs barriers only lased at higher currents for a short wavelength transition ~900nm. While threshold currents are relatively high, no post growth thermal annealing was performed on these laser materials. Thermal annealing studies will be presented indicating significant improvement in QW luminescence and reduction in Jth can be achieved after the post-growth in-situ annealing. [1] Ludewig, P., Knaub, N., Hossain, N., Reinhard, S., Nattermann, L., Marko, I. P., and Volz, K. 2013. Appl. Phys. Lett., 102(24), 242115.

To overcome the limitations placed on the operating characteristics of diode lasers by recombination outside their active region, two novel designs were proposed for them: one using double tunneling-injection (injection of both electrons and holes) into the active region, and the other using two asymmetric barrier layers (ABLs) flanking the active region. The barrier layers are asymmetric in that they have considerably different heights for the carriers of opposite signs. The ABL located on the electron- (hole-) injecting side of the structure provides a low barrier (ideally no barrier) for electrons (holes) [so that it does not prevent electrons (holes) from easily approaching the active region] and a high barrier for holes (electrons) [so that holes (electrons) injected from the opposite side of the structure do not overcome it]. The use of ABLs should thus ideally prevent the simultaneous existence of electrons and holes (and hence parasitic electron-hole recombination) outside the active region. In this work, we calculate the threshold and power characteristics of quantum dot lasers with ABLs. We show that quantum dot lasers with ABLs offer close-to-ideal performance: low threshold current density, very high characteristic temperature (virtually temperature-independent operation), close-to-unity internal differential quantum efficiency, and linear light-current characteristic.

An overview is given about the recent improvement in 1.55 μm QD lasers for direct modulation. Based on improved QD epitaxy, which reduces the inhomogeneous size distribution, record values in small signal modulation bandwidth of more than 15 GHz and in digital modulation of up to 35 GBit/s were obtained. Due to the high modal gain and robust ground state transition, the temperature dependence of the laser performance could be very much improved with characteristic temperatures of T₀ = 125 K and T₁ near to 400 K. This allow a temperature stable modulation bandwidth between 15-60 °C of (14 +/- 1) GHz sufficient for 25 GBit/s digital modulation.

We present state-of-the-art performance from laser based light sources based on semipolar GaN. Recent advances toward the commercialization of blue, InGaN semipolar laser diodes are described. Additionally, we introduce next generation white light sources based on laser-pumped phosphor architectures.

Waveguide (WG) architectures of 420-nm emitting InAlGaN/GaN diode lasers are analyzed by photoluminescence (PL) and photocurrent (PC) spectroscopy using a nearfield scanning optical microscope (NSOM) for excitation and detection. The measurements with a spatial resolution of ~100 nm are implemented by scanning the fiber tip along the unprepared front facets of standard devices. PL is collected by the fiber tip, whereas PCs are extracted from the contacts that are anyway present for power supply. The mechanisms of signal generation are addressed in detail. The components of the ‘optical active region’, multiple quantum wells (MQW), WGs, and cladding layers are separately inspected. Even separate analysis of p- and n-sections of the WG become possible. Defect levels are detected in the p-part of the WG. Their presence is consistent with the doping by Mg. An increased efficiency of carrier capture into InGaN/GaN WGs compared to GaN WGs is observed. Thus, beyond the improved optical confinement, the electrical confinement is improved, as well. NSOM PL and PC at GaN based devices do not reach the clarity and spatial resolution for WG mode analysis as seen before for GaAs based devices. This is due to higher modal absorption and higher WG losses. NSOM based optical analysis turns out to be an efficient tool for analysis of single layers grown into InAlGaN/GaN diode laser structures, even if this analysis is done at a packaged ready-to-work device.

The range of applications of blue and green lasers is increasing from year to year. Driving factors are costs and performance. On one hand we study the characteristics of low power R&D c-plane laser structures with improved Gaussian vertical and horizontal beam profile: We present new best values for efficiencies of single mode green lasers of 10.8% at 517nm and new long wavelength data at 532nm with efficiency of 6.5%. Furthermore, we present a new R&D design of a blue single mode laser diode with a very low threshold of 8.5mA. On the other hand, recent R&D results on broad area multi-mode power designs are shown: Efficiencies of 43% at 4W optical output power are achieved. Lifetime tests as long as 10000h are presented. High reliability is reached by a new facet design.

Here, we review recent progress that contributes to the applicability of passively mode-locked semiconductor lasers by improving their timing and amplitude stability. Experimental concepts include passive electrical stabilization, and extended optical feedback configurations. The overall aim is to reduce both amplitude and timing instabilities thus accessing the increased potential of mode-locked lasers towards nonlinear imaging and time-critical applications.

A new compact 1030 nm picosecond light source which can be switched between pulse gating and mode locking operation is presented. It consists of a multi-section distributed Bragg reflector (DBR) laser, an ultrafast multisection optical gate and a flared power amplifier (PA), mounted together with high frequency electronics and optical elements on a 5×4 cm micro bench. The master oscillator (MO) is a 10 mm long ridge wave-guide (RW) laser consisting of 200 μm long saturable absorber, 1500 μm long gain, 8000 μm long cavity, 200 μm long DBR and 100 μm long monitor sections. The 2 mm long optical gate consisting of several RW sections is monolithically integrated with the 4 mm long gain-guided tapered amplifier on a single chip. The light source can be switched between pulse gating and passive mode locking operation. For pulse gating all sections of the MO (except of the DBR and monitor sections) are forward biased and driven by a constant current. By injecting electrical pulses into one section of the optical gate the CW beam emitted by the MO is converted into a train of optical pulses with adjustable widths between 250 ps and 1000 ps. Peak powers of 20 W and spectral linewidths in the MHz range are achieved. Shorter pulses with widths between 4 ps and 15 ps and peak powers up to 50 W but larger spectral widths of about 300 pm are generated by mode locking where the saturable absorber section of the MO is reversed biased. The repetition rate of 4.2 GHz of the pulse train emitted by the MO can be reduced to values between 1 kHz and 100 MHz by utilizing the optical gate as pulse picker. The pulse-to-pulse distance can be controlled by an external trigger source.

Mode-locked semiconductor laser technology is a promising technology candidate considered by European Space Agency (ESA) for optical metrology systems and other space applications in the context of high-precision optical metrology, in particular for High Accuracy Absolute Long Distance Measurement. For these applications, we have designed, realized and characterized a multi-section monolithic-cavity tapered laser diode with a record cavity length of 13.5mm. The laser operates at 975nm wavelength with average output power up to 600mW. It is based on a MOVPE grown laser structure with Aluminium free active region enabling high optical gain, low internal losses and low series resistance. It reaches passive mode-locking operation on fundamental cavity round trip frequency of 2.88GHz with chirped pulse width of 6.2ps and time bandwidth product of 8 for the average output power of 250mW. Alongside with passive mode-locking operation, we discuss other lasing regimes in these very long tapered lasers.

In this paper an overview is presented of results obtained with mode-locked semiconductor laser systems that are monolithically integrated using a standardized photonic integration platform based on InP. The laser systems are operating around 1550nm. In this technology platform the basic components that form the laser circuits such as amplifiers, passive waveguides and filters, as well as the semiconductor processing are standardized. Several of the possibilities that such a standardized technology offer are demonstrated by a number of examples of realized devices such as low repetition rate mode-locked lasers, a stabilized comb system and a wide frequency comb source.

In the paper, we elaborate our recent work on monolithic (by epitaxial growth) and heterogeneous (by adhesive bonding) integration techniques that may pave the path to the final solutions of IIIV lasers on silicon in different scenarios. In the case of on-chip optical interconnects, a large number of IIIV lasers with high integration density are highly demanded. By using a buffer-less selective growth technique, we are able to grow submicron-sized InP waveguides directly on silicon. All the dislocations are confined at the interface between Si and InP, which leads to the successful demonstration of a distributed feedback (DFB) laser array with good uniformity. Thanks to the minimized buffer layer thickness (20 nm) and the standard top-down laser process flow, it is possible to demonstrate very high integration density of IIIV lasers on silicon. Recently, by growing InGaAs/InP heterostructures on the virtual lattice-matched InP-on-Si template, we are able to achieve room-temperature lasing at communication wavelength range. On the other hand, the relatively mature bonding based heterogeneous integration technology has been well developed over the last decade, and the integration of various laser configurations on silicon lead to more system level demonstrations. Here, we present our recent work on IIIV-on-Si mode-locked lasers. Thanks to the extremely low silicon waveguide loss, we are able to achieve record-low repetition rate of 1GHz, with an extremely low RF linewidth (sub-kHz). Such devices are promising for applications such as spectroscopy, microwave photonics etc.

High temperature stability and high feedback-noise tolerance of the quantum dot lasers are advantageous features for application to silicon photonics. A silicon optical interposer with the bandwidth-density of 15Tbps/cm2 at 125 °C was demonstrated using flip-chip bonding method. Moreover, we report the first demonstration of a hybrid silicon quantum dot (QD) laser, evanescently coupled to a silicon waveguide. InAs/GaAs QD laser structures with thin AlGaAs lower cladding layers were transferred, by means of direct wafer bonding, onto silicon waveguides defining cavities with adiabatic taper structures and distributed Bragg reflectors (DBRs). The laser operates at temperatures up to 115 °C under pulsed current conditions, with a characteristic temperature T0 of 303 K near room temperature. Furthermore, by reducing the width of GaAs/AlGaAs mesa down to 8 μm, continuous-wave operation is realized at 25 °C.

Silicon integration of mid-infrared (MIR) photonic devices promises to enable low-cost, compact sensing and detection capabilities that are compatible with existing silicon photonic and silicon electronic technologies. Heterogeneous integration by bonding III-V wafers to silicon waveguides has been employed previously to build integrated diode lasers for wavelengths from 1310 to 2010 nm. Recently, Fabry-Perot Quantum Cascade Lasers integrated on silicon provided a 4800 nm light source for MIR silicon photonic applications. Distributed feedback (DFB) lasers are appealing for many high-sensitivity chemical spectroscopic sensing applications that require a single frequency, narrow-linewidth MIR source. While heterogeneously integrated 1550 nm DFB lasers have been demonstrated by introducing a shallow surface grating on a silicon waveguide within the active region, no mid-infrared DFB laser on silicon had previously been reported. Here we demonstrate quantum cascade DFB lasers heterogeneously integrated with silicon-on-nitride-oninsulator (SONOI) waveguides. These lasers emit over 200 mW of pulsed power at room temperature and operate up to 100 °C. Although the output is not single mode, the DFB grating nonetheless imposes wavelength selectivity with 22 nm of thermal tuning.

Continuous-wave optically-pumped micro-disk lasers epitaxially grown on silicon with single mode lasing at communication wavelengths from liquid helium to room temperature is reported. Growth of the InAs quantum dots (QDs) gain medium was carried out on high crystalline quality GaAs/InP-on-silicon templates. Special defect filtering techniques have been employed to minimize the impact of the highly lattice-mismatched heteroepitaxial growth on (001) silicon substrates. Compared with quantum wells, the multi-stack InAs QDs are less sensitive to residual defects originated from the hetero-interfaces. Using QDs in a micro-disk resonant cavity with minimized non-radiative surface recombination leads to low-threshold lasing in the micro-disks with a few microns in diameter.

The development of energy-efficient ultra-compact nanolaser diodes integrated in a Silicon photonic platform is of paramount importance for the deployment of optical interconnects for intra-chip communications. In this work, we present our results on InP-based electrically injected photonic crystal (PhC) nanolaser integrated on a SOI waveguide circuitry. The lasers emit at room temperature in a continuous wave regime at 1560nm and exhibit thresholds of 0.1mA at 1V. We measure more than 100μW of light coupled into the SOI waveguides giving a wall-plug efficiency greater than 10%. The principle of the lasers relies on the use of a 1D PhC nanocavity made of InP-based materials positioned on top of a SOI waveguide to enable evanescent wave coupling. More in details, the laser cavity is a 650nm-wide rib waveguide drilled with a single row of equally sized holes (radius~100nm). The distance between the holes is varied to obtain Q-factors larger than 106 for a structure fully encapsulated in silica with material volume of the order of the cubic wavelength. Vertically, the InP heterostructure is a 450nm thick NIP junction embedding 5 strained InGaAsP quantum wells emitting at 1.53μm. By smartly positioning the metallic contacts, this configuration enables the efficient electrical injection of electron-holes pairs within the cavity without inducing optical losses which led us to demonstrate the laser emission coupled ta a Si waveguide.

Wavelength scale coherent optical sources are vital for a wide range of applications in nanophotonics ranging from metrology and sensing to nonlinear frequency generation and optical switching. In these respects, semiconductor nanowires (NWs) are of particular interest since they represent the ultimate limit of downscaling for photonic lasers with dielectric resonators. By virtue of their unique one-dimensional geometry NW-lasers combine ultra-high modal gain, support low-loss guided modes and facilitate low threshold lasing tuneable across the UV, visible and near infra-red spectral regions. Recently, optically pumped NW lasers have been demonstrated at room temperature and they can now be site-selectively integrated onto silicon substrates. While the fundamental carrier relaxation and gain dynamics of NW-lasers have been explored, the coherent dynamics have hitherto received comparatively little attention. In this contribution, we demonstrate that GaAs-AlGaAs core-shell nanowire lasers grown on silicon are capable of emitting pairs of phase-locked picosecond laser pulses when subject to incoherent pulsed optical excitation. By probing the two-pulse interference that emerges within the homogeneously broadened laser emission, we show that pulse pairs remain mutually coherent over timescales extending beyond ~30ps, much longer than the emitted laser pulse duration (~3 ps). Simulations performed by solving the optical Bloch equations produce good quantitative agreement with experiments, revealing how the phase information is stored in the gain medium close to transparency.

Nanoscale lasers are the key component in the integrated photonics chips and have attracted much interests. Nanoblets and nanowires lasers, as one of the candidates for the nanoscale lasers, have been developed for one more decades. Many kinds of nanowire lasers with different functionalities, such as wavelength tunable, single mode, polarized emission and so on, have been demonstrated. However, the reported single mode nanowire lasers are mostly realized through microfabrication process, careful manipulation and complicated structures. Here, we present a new type of lateral emission single mode nanobelt lasers with high polarization ratio which are fabricated by the one step traditional VLS (Vapor Liquid Solid) growth. Different from the traditional nanobelt lasers which are based on the FP cavity formed in the longitudinal direction, the emission of this novel nanoblet laser is lateral which is contribute to the special wire-like structures grown on the nanobelt. It shows band edge emission and the wavelength is centered at 712.6 nm with linewidth about 0.18 nm. The threshold reach as low as 15 uJ/cm2 benefit from the unique morphology which provides enhanced confinement factor for optical modes. Meanwhile the laser emission is highly polarized with polarization ration as high as 0.91. This lateral emission single mode nanobelt laser with high polarization ratio, low threshold and simple fabrication technique offers an economic and effective choice to the future optical applications.

Two of the most successful microcresonator concepts are the vertical cavity surface emitting laser (VCSEL), where light is confined between distributed Bragg reflectors (DBRs), and the distributed feedback (DFB) laser, where a periodic grating provides positive optical feedback to selected modes in an active waveguide (WG) layer. Our work concerns the combination of both into a composite device, facilitating coherent interaction between both regimes and giving rise to novel laser modes in the system. In a first realization, a full VCSEL stack with an organic active layer is evaporated on top of a diffraction grating with a large period (approximately 1 micron), leading to diffraction of waveguided modes into the surface emission of the device. Here, the coherent interaction between VCSEL and WG modes, as observed in an anticrossing of the dispersion lines, facilitates novel hybrid lasing modes with macroscopic in-plane coherence [1]. In further studies, we decrease the grating period of such devices to realise DFB conditions in a second-order Bragg grating which strongly couples photons via first-order light diffraction to the VCSEL. This efficient coupling can be compared to more classical cascade-coupled cavities and is successfully described by a coupled oscillator model [2]. When both resonators are non-degenerate, they are able to function as independent structures without substantial diffraction losses. The realization of such novel devices provides a promising platform for photonic circuits based on organic microlasers. [1] A. Mischok et al., Adv. Opt. Mater., early online, DOI: 10.1002/adom.201600282, (2016) [2] T. Wagner et al., Appl. Phys. Lett., accepted, in production, (2016)

Cascade pumping of type-I quantum well gain sections was utilized to increase output power and efficiency of GaSb-based diode lasers operating in spectral region from 1.9 to 3.3 μm. Two-step ridge waveguide design with shallow 5-μm-wide and deep 15-μm-wide etched sections yielded λ ~ 2 μm lasers generating 250 mW of continuous wave output power in nearly diffraction limited beam when mounted epi-down. The same device mounted epi-up demonstrated output power of about 180 mW. Lasers operating in the wavelength range above 3.2 μm with variable deep etched ridge width and two-step ridge design were fabricated and characterized. Two-step ridge waveguide design yielded the lowest threshold current and the highest slope efficiency. Tens of mW of continuous wave output power was obtained in nearly diffraction limited beams in the wavelength range from 3.2 to 3.3 μm near and above 20 °C in both epi-up and epi-down mounting configurations. Laterally-coupled 2-nd-order distributed feedback lasers operated near 3.22 μm in continuous wave regime at room temperatures with more than 10 mW of output power at room temperature in epi-up mounted configuration.

Implementation of the step-taper active-region (STA) design to 8-9 μm-emitting quantum cascade lasers (QCLs) has resulted in both high T₀ and T₁ values: 220 K and 665 K, and short lower-level lifetimes: 0.12 ps. In turn, the internal differential efficiency η_id, which is the product of the injection efficiency and the differential laser-transition efficiency, reaches values as high as 86 % for both 8.4 μm- and 8.8 μm-emitting QCLs. Such η_id values are 30-50% higher than those obtained from conventional QCLs emitting in the 7-11 μm wavelength range. Achieving both carrier-leakage suppression and miniband-like carrier extraction in mid-infrared (IR) QCLs leads to η_id values close to the fundamental limit of ~ 90 %. In turn, the currently employed fundamental wallplug-efficiency limits over the mid-IR wavelength range have to be increased by ~ 34 % (e.g., the wallplug-efficiency limit at λ= 4.6 μm increases from 29 % to 39 %). Preliminary results from STA-type 4.8-5.0 μm-emitting QCLs include 1.5 W CW operation, and 77 % internal differential efficiency; that is, 30-50% higher than the η_id values obtained from conventional 4.0-6.5μm-emitting QCLs.

5.6 μm quantum cascade lasers based on Al 0.78 In 0.22 As/In 0.69 Ga 0.31 As active region composition with measured pulsed room temperature wall plug efficiency of 28.3% are reported. Injection efficiency for the upper laser level of 75% was measured for the new design by testing devices with variable cavity length. Threshold current density of 1.7kA/cm² and slope efficiency of 4.9W/A were measured for uncoated 3.15mm × 9μm lasers. Threshold current density and slope efficiency dependence on temperature in the range from 288K to 348K for the new structure can be described by characteristic temperatures T₀ ~ 140K and T₁ ~710K, respectively. Experimental data for inverse slope efficiency dependence on cavity length for 15-stage quantum cascade lasers with the same design are also presented. When combined with the 40-stage device data, the new data allowed for separate evaluation of the losses originating from the active region and from the cladding layers of the laser structure. Specifically, the active region losses for the studied design were found to be 0.77 cm^-1, while cladding region losses - 0.33 cm^-1. The data demonstrate that active region losses in mid wave infrared quantum cascade lasers largely define total waveguide losses and that their reduction should be one of the main priorities in the quantum cascade laser design.

Coupled-cavity lasers have attracted wide attention in the past, in particular for telecommunication applications where their wavelength tunability and ability for side mode suppression are desirable. The inherent sensitivity of these devices to changes in the optical coupling has also led to their proposed use in optical sensing systems. Small changes to the refractive index of the coupler section can lead to shifts in the resonance frequency of the laser. Here we present an alternative approach to coupled-cavity sensing that exploits changes to the imaginary part of the refractive index of the coupler. An optical loss, introduced to the cavity by the passage of micro-particles, influences the optical loss of the lasing mode and changes the threshold gain requirement of the laser. The sub-linear nature of the gain-current density characteristics of the quantum confined gain medium amplifies this effect, producing an even larger perturbation in output power. We demonstrate this sensing mechanism using a monolithic coupled-cavity particle detector with on-chip capillary fill microfluidics and an in-line photo-detector section for photo-voltage transduction. Both laser and detector are pulsed allowing for a time-resolved measurement to be taken.

Shifted excitation Raman difference spectroscopy is a powerful tool to separate the weak Raman lines from disturbing background light like fluorescence, day light or artificial light. When exciting the sample alternatingly with two slightly shifted wavelengths, the Raman lines follow the change whereas the background remains unchanged. Therefore, background free Raman spectra can be obtained measuring the two Raman spectra, subtracting the two signals and applying a reconstruction algorithm. When the spectral distance between the two wavelengths is the width of the Raman lines under study best signal-to-noise ratios can be achieved. In this work, monolithic dual wavelength Y-branch DBR ridge waveguide diode lasers with resistor heaters over the DBR gratings will be presented. The devices have a total length of 3 mm and a RW stripe width of 2.2 μm. The wavelengths are defined and stabilized using 500 μm long 10th order gratings with a designed spectral distance of 0.62 nm. Using the resistor heaters, this distance can be adjusted. The monolithic devices reach optical output powers up to 180 mW. Over the full range, they operate in single mode. The emission width is smaller than 13 pm (FWHM). At an output power of 50 mW the conversion efficiency is 0.22, which only slightly decreases down to 0.18 at maximal power. At an output power of 100 mW and with heater currents smaller than 600 mA, the spectral distance can be tuned from 0 nm up to 2 nm. The spectra remain single mode.

We developed fiber coupled, narrow line, tunable, highly reliable, compact and robust laser source at 1651nm. The developed laser source exhibits a narrow spectral width ~2MHz at >400mW of CW output power in a single mode fiber. Tuning range >1nm was demonstrated.

A dual-wavelength diode laser with sub-MHz narrowband emission at 785 nm is presented. The device is investigated for both emission lines up to an optical power of 150 mW. A stable spectral distance between the two laser wavelengths of 0.6 nm (10 cm^-1) over the whole power range is achieved. At 20 mW the emission shows a minimum 3 dB width of 250 kHz and below 1 MHz for output powers up to 80 mW. The results demonstrate that besides the already demonstrated suitability of these devices for Raman spectroscopy and shifted excitation Raman difference spectroscopy, the dual-wavelength diode laser have also the potential for sub-MHz spectroscopic applications.

The integration of multiple optical elements on a common substrate to create photonic integrated circuits (PIC) has been successfully applied in: fibre-optic communications, photonic computing and optical sensing. The push towards III-Vs on silicon promises a new generation of integrated devices that combine the advantages of both integrated electronics and optics in a single substrate. III-V edge emitting laser diodes offer high efficiency and low threshold currents making them ideal candidates for the optically active elements of the next generation of PICs. Nevertheless, the highly divergent and asymmetric beam shapes intrinsic to these devices limits the efficiency with which optical elements can be free space coupled intra-chip; a capability particularly desirable for optical sensing applications e.g. [1]. Furthermore, the monolithic nature of the integrated approach prohibits the use of macroscopic lenses to improve coupling. However, with the advent of 3D direct laser writing, three dimensional lenses can now be manufactured on a microscopic-scale [2], making the use of micro-lens technology for enhanced free space coupling of integrated optical elements feasible. Here we demonstrate the first use of 3D micro-lenses to improve the coupling efficiency of monolithically integrated lasers. Fabricated from IP-dip photoresist using a Nanoscribe GmbH 3D lithography tool, the lenses are embedded directly onto a structured GaInP/AlGaInP substrate containing arrays of ridge lasers free space coupled to one another via a 200 μm air gap. We compare the coupling efficiency of these lasers with and without micro-lenses through photo-voltage and beam profile measurements and discuss optimisation of lens design.

This paper, originally published on 20 April 2017, has been withdrawn per author request.

Mid-infrared (MIR; 3-20 μm) sensor technology is increasingly applied in environmental analysis, process monitoring and biodiagnostics due to the inherent molecular specificity enabling the discrimination of molecular components at ppm-ppb concentration levels. Recently emerging strategies taking advantage of innovative waveguide technologies including substrate-integrated hollow waveguides for detecting vapor phase media, and thin-film planar waveguides for analyzing liquid or solid state samples in combination with highly efficient light sources including quantum cascade and interband cascade lasers facilitate the development of compact and robust MIR on-chip sensing platforms for label-free chem/bio sensing and diagnostics.

Terahertz quantum-cascade vertical external cavity surface emitting laser (VECSELs) are made possible through the development of amplifying reflectarray metasurfaces. The metasurface is made up of sub-wavelength arrays of antenna coupled sub-cavities loaded with quantum-cascade active material. The QC-VECSEL approach allows scaling of laser power while maintaining a high quality, near diffraction limited beam - something which has been a long standing challenge for THz quantum-cascade lasers with sub-wavelength metallic waveguides. The latest results of cavity and metasurface engineering are presented, including the demonstration of a focusing reflectarray metasurface that enables a "flat-optics" hemispherical VECSEL cavity, with improved geometric stability and a Gaussian profile beam with beam quality parameter of M2=1.3.

Plasmonic lasers generate coherent long-range or localized surface-plasmon-polaritons (SPPs), where the SPP mode exists at the interface of the metal (or a metallic nanoparticle) and a dielectric. Metallic-cavities sup- porting SPP modes are also utilized for terahertz quantum-cascade lasers (QCLs). Due to subwavelength apertures, plasmonic lasers have highly divergent radiation patterns. Recently, we theoretically and experimentally demonstrated a new technique for implementing distributed-feedback (DFB), which is termed as an antenna- feedback scheme, to establish a hybrid SPP mode in the surrounding medium of a plasmonic laser’s cavity with a large wavefront. This technique allows such lasers to radiate in narrow beams without requirement of any specific design considerations for phase-matching. Experimental demonstration is done for terahertz QCLs that show beam-divergence as small as 4-degrees. The antenna-feedback scheme has a characteristic feature in that refractive-index of the laser’s surrounding medium affects its radiative frequency in the same vein as refractive- index of the cavity. Hence, any perturbations in the refractive-index of the surrounding medium could lead to large modulation in the laser’s emission frequency. Along this line, we report ~57 GHz reversible, continuous, and mode-hop-free tuning of such QCLs operating at 78 K based on post-process deposition/etching of a dielectric on an already mounted QCL chip. This is the largest tuning range achieved for terahertz QCLs when operating much above the temperature of liquid-Helium. We review the aforementioned experimental results and discuss methods to increase optical power output from terahertz QCLs with antenna-feedback. Peak power output of ~13 mW is realized for a 3.3 THz QCL operating in a Stirling cooler at 54 K. A new dual-slit photonic structure based on antenna-feedback scheme is proposed to further improve output power as well as provide enhanced tunability.

Recent work has been showing the possibility of generating frequency combs at terahertz frequencies using terahertz quantum cascade lasers. The main efforts so far were on getting the laser to work in a stable comb operation over an as broad as possible spectral bandwidth. Another issue is the scattered farfield of such combs due to their subwavelength facets of the used metal-metal waveguide. In contrast to single mode lasers the monolithic approaches of distributed feedback lasers or photonic crystals cannot be used. We present here a monolithic broadband extractor compatible with frequency comb operation based on the concept of an end-fire antenna. The antenna can be fabricated using standard fabrication techniques. It has been designed to support a bandwidth of up to 600 GHz at a central frequency of 2.5 THz. The fabricated devices show single lobed farfields with only minor asymmetries, increased output power along an increased dynamical range of frequency comb operation. A side-absorber schematics using a thin film of Nickel has been used to suppress any higher-order lateral modes in the laser. The reported frequency combs with monolithic extractors are ideal candidates for spectroscopic applications at terahertz frequencies using a self-detected dual-comb spectroscopy setup due to the increased dynamical range along with the improved farfield leading to more output power of the frequency combs.

High-resolution terahertz (THz) heterodyne spectroscopy is an important technique in astronomy. So far frequencies above 2.5 THz could not be accessed by this technique because of the lack of a suitable local oscillator. A novel local oscillator based on a THz quantum-cascade laser allows for the observation of the fine-structure line of neutral atomic oxygen at 4.7448 THz. The local oscillator has been implemented in the GREAT (German REceiver for Astronomy at Terahertz frequencies) spectrometer on SOFIA, the Stratospheric Observatory for Infrared Astronomy. The design and the performance of the local oscillator will be presented.

We discuss novel approaches to improve the tuning bandwidth and power output of terahertz (THz) sources based on difference-frequency generation (DFG) in mid-infrared quantum cascade lasers (QCLs). Using a double Littrow external-cavity system, we experimentally demonstrate that both doubly-resonant terms and optical rectification terms in the expression for the intersubband optical nonlinearity contribute to THz generation in DFG-QCLs and report THz DFG-QCLs with the optimized optical rectification terms. We also demonstrate a hybrid DFG-QCL device on silicon that enables significant improvement on THz out-coupling efficiency and results in more than 5 times higher THz output power compared to that of a reference device on its native semi-insulating InP substrate. Finally, we report for the first time the THz emission linewidth of a free-running continuous-wave THz DFG-QCL.

We demonstrate that an application of a III-V-on-silicon hybrid concept to terahertz (THz) Cherenkov difference frequency generation (DFG) quantum cascade laser (QCL) sources (THz DFG-QCLs) can dramatically improve THz output power and mid-infrared-to-THz conversion efficiency. Completely processed THz DFG-QCLs grown on a 660-μm-thick native InP substrate are transfer-printed onto a 1-mm-thick high-resistive Si substrate using a 100-nm-thick SU-8 as an adhesive layer. Room temperature device performance of the reference InP and hybrid Si THz DFG-QCLs of the same ridge width (22 μm) and cavity length (4.2 mm) have been experimentally compared. The target THz frequency of 3.5 THz is selected for both devices using the dual-period first order surface gratings to select the mid-infrared pump wavelength of 994 cm^-1 and 1110 cm^-1. At the maximum bias current, the reference InP and hybrid Si devices produced THz power of 50 μW and 270 μW, respectively. The mid-infrared-to-THz conversion efficiency corresponds to 60 μW/W² and 480 μW/W², respectively, resulting in 5 times higher THz power and 8 times higher conversion efficiency from the best-performing hybrid devices. A hybrid Si device integrated in a Littrow external-cavity setup showed wavelength tuning from 1.3 THz to 4.3 THz with beam-steering free operation.

High-quality thin films of highly aligned semiconducting single-wall carbon nanotubes have been recently demonstrated. They have excellent absorption and photoluminescence properties; however, fast nonradiative recombination of carriers prevents their use as a gain medium in lasers. Here we predict that such films can operate as efficient sources of ultrashort radiation pulses under the conditions of superfluorescence, i.e. cooperative interband recombination of injected electrons and holes. Superfluorescence develops much faster than nonradiative recombination and leads to high-intensity, coherent pulses of near/mid-infrared radiation.

Recombination of carriers in the direct-bandgap base of a transistor-injected quantum cascade laser (TI-QCL) is shown to be controllable through the field applied across the quantum cascade region located in the transistor’s base-collector junction. The influence of the electric field on the quantum states in the cascade region’s superlattice allows free flow of electrons out of the transistor base only for field values near the design field that provides optimal QCL gain. Quantum modulation of base recombination in the light-emitting transistor is therefore observed. In a GaAs-based light-emitting transistor, a periodic superlattice is grown between the p-type base and the n-type collector. Under different base-collector biasing conditions the distribution of quantum states, and as a consequence transition probabilities through the wells and barriers forming the cascade region, leads to strong field-dependent mobility for electrons in transit through the base-collector junction. The radiative base recombination, which is influenced by minority carrier transition lifetime, can be modulated through the quantum states alignment in the superlattice. A GaAs-based transistor-injected quantum cascade laser with AlGaAs/GaAs superlattice is designed and fabricated. Radiative base recombination is measured under both common-emitter and common-base configuration. In both configurations the optical output from the base is proportional to the emitter injection. When the quantum states in the superlattice are aligned the optical output in the base is reduced as electrons encounter less impedance entering the collector; when the quantum states are misaligned electrons have longer lifetime in the base and the radiative base recombination process is enhanced.

Volume Bragg gratings (VBGs) recorded in photo-thermo-refractive (PTR) glass are holographic optical elements that are effective spectral and angular filters withstanding high power laser radiation. Reflecting VBGs are narrow-band spectral filters while transmitting VBGs are narrow-band angular filters. The use of these optical elements in external resonators of semiconductor lasers enables extremely resonant feedback that provides dramatic spectral and angular narrowing of laser diodes radiation without significant power and efficiency penalty. Spectral narrowing of laser diodes by reflecting VBGs demonstrated in wide spectral region from near UV to 3 μm. Commercially available VBGs have spectral width ranged from few nanometers to few tens of picometers. Efficient spectral locking was demonstrated for edge emitters (single diodes, bars, modules, and stacks), vertical cavity surface emitting lasers (VCSELs), grating coupled surface emitting lasers (GCSELs), and interband cascade lasers (ICLs). The use of multiplexed VBGs provides multiwavelength emission from a single emitter. Spectrally locked semiconductor lasers demonstrated CW power from milliwatts to a kilowatt. Angular narrowing by transmitting VBGs enables single transverse mode emission from wide aperture diode lasers having resonators with great Fresnel numbers. This feature provides close to diffraction limit divergence along a slow axis of wide stripe edge emitters. Radiation exchange between lasers by means of spatially profiled or multiplexed VBGs enables coherent combining of diode lasers. Sequence of VBGs or multiplexed VBGs enable spectral combining of spectrally narrowed diode lasers or laser modules. Thus the use of VBGs for diode lasers beam control provides dramatic increase of brightness.

A novel marco channel cooler (MaCC) has been developed for packaging high power diode vertical stacked (HPDL) lasers, which eliminates many of the issues in commercially-available copper micro-channel coolers (MCC). The MaCC coolers, which do not require deionized water as coolant, were carefully designed for compact size and superior thermal dissipation capability. Indium-free packaging technology was adopted throughout product design and fabrication process to minimize the risk of solder electromigration and thermal fatigue at high current density and long pulse width under QCW operation. Single MaCC unit with peak output power of up to 700W/bar at pulse width in microsecond range and 200W/bar at pulse width in millisecond range has been recorded. Characteristic comparison on thermal resistivity, spectrum, near filed and lifetime have been conducted between a MaCC product and its counterpart MCC product. QCW lifetime test (30ms 10Hz, 30% duty cycle) has also been conducted with distilled water as coolant. A vertical 40-MaCC stack product has been fabricated, total output power of 9 kilowatts has been recorded under QCW mode (3ms, 30Hz, 9% duty cycle).

A 1030 nm distributed Bragg reflector (DBR) tapered diode laser with optimized vertical layer structure and lateral design is presented. At a heatsink temperature of 15°C the developed laser provides up to 16 W of optical output power. The maximum electro-optical efficiency is 57%. Intrinsic wavelength stabilization is obtained by a 7th order DBR grating and results in a narrowband emission over the whole power range. Ion implantation next to the ridge-waveguide is applied in order to suppress propagation of unwanted lateral side modes. The highest diffraction-limited central lobe power measured for this device is 9.1 W. With these properties the presented high brightness laser is suitable for applications such as nonlinear frequency conversion.

Single mode tapered semiconductor lasers producing watt-class output powers often suffer from beam quality degradation as drive current increases. The dominant degradation mechanism is believed to be poor gain clamping in the periphery of the optical mode; as the injection current is increased, excess gain in this region eventually leads to parasitic lasing in the amplifier section of the device. However, this effect has not previously been directly observed and other effects such as thermal lensing and gain guiding also likely contribute. Nevertheless, it has been previously shown that by engineering the overlap of the gain profile with the nonuniform optical intensity distribution, performance can be significantly improved. In this work, we report on the direct observation and mapping of the 2D gain profile in a tapered semiconductor laser. InGaAsP-based tapered diode lasers are fabricated with windowed openings on the back (substrate) side of the chip. The devices are soldered junction down for continuous wave operation. An optical microscope is used to observe and map the 2D spontaneous emission profile, and hence gain and carrier density, of the device under operation. The results are compared to a theoretical model to better understand the physical limitations of beam quality degradation in tapered diode lasers.

Focused ion beam milling was used to fabricate on-chip unstable resonator cavity quantum well laser devices. A cylindrical mirror was formed at the back facet of the broad area device emitting near 2 μm. Compared to the Fabry-Pérot cavity device, the unstable resonator cavity device exhibits a 2x diffraction limited beam. The preliminary results demonstrate that a much higher brightness can be reached in this class of broad area devices.

The solid state laser relies on the laser diode (LD) pumping array. Typically for high peak power quasi-CW (QCW) operation, both energy output per pulse and long term reliability are critical. With the improved bonding technique, specially Indium-free bonded diode laser bars, most of the device failures were caused by failure within laser diode itself (wearout failure), which are induced from dark line defect (DLD), bulk failure, point defect generation, facet mirror damage and etc. Measuring the reliability of LD under QCW condition will take a rather long time. Alternatively, an accelerating model could be a quicker way to estimate the LD life time under QCW operation. In this report, diode laser bars were mounted on micro channel cooler (MCC) and operated under QCW condition with different current densities and junction temperature (T_j ). The junction temperature is varied by modulating pulse width and repetition frequency. The major concern here is the power degradation due to the facet failure. Reliability models of QCW and its corresponding failures are studied. In conclusion, QCW accelerated life-time model is discussed, with a few variable parameters. The model is compared with CW model to find their relationship.

The terahertz (THz) spectral range (lambda ~ 30µm – 300µm) is also known as the “THz-gap” because of the lack of compact semiconductor devices. Various real-world applications would strongly benefit from such sources like trace-gas spectroscopy or security-screening. A crucial step is the operation of THz-emitting lasers at room temperature. But this seems out of reach with current devices, of which GaAs-based quantum cascade lasers (QCLs) seem to be the most promising ones. They are limited by the parasitic, non-optical LO-phonon transitions (36meV in GaAs), being on the same order as the thermal energy at room temperature (kT = 26meV). This can be solved by using larger LO-phonon materials like ZnO (E_LO = 72meV). But to master the fabrication of ZnO-based QC structures, a high quality epitaxial growth is crucial followed by a well-controlled fabrication process including ZnO/ZnMgO etching. We use devices grown on m-plane ZnO-substrate by molecular beam epitaxy. They are patterned by reactive ion etching in a CH4-based chemistry (CH4:H2:Ar/30:3:3 sccm) into 50μm to 150μm square mesas. Resonant tunneling diode structures are investigated in this geometry and are presented including different barrier- and well-configurations. We extract contact resistances of 8e-5 Omega cm^2 for un-annealed Ti/Au contacts and an electron mobility of above 130cm^2/Vs, both in good agreement with literature. Proving that resonant electron tunneling can be achieved in ZnO is one of the crucial building blocks of a QCL. This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 665107.

Superradiance is one of the many fascinating phenomena predicted by quantum electrodynamics that have first been experimentally demonstrated in atomic systems and more recently in condensed matter systems like quantum dots, superconducting q-bits, cyclotron transitions and plasma oscillations in quantum wells (QWs). It occurs when a dense collection of N identical two-level emitters are phased via the exchange of photons, giving rise to enhanced light-matter interaction, hence to a faster emission rate. Of great interest is the regime where the ensemble interacts with one photon only and therefore all of the atoms, but one, are in the ground state. In this case the quantum superposition of all possible configurations produces a symmetric state that decays radiatively with a rate N times larger than that of the individual oscillators. This phenomenon, called single photon superradiance, results from the exchange of real photons among the N emitters. Yet, to single photon superradiance is also associated another collective effect that renormalizes the emission frequency, known as cooperative Lamb shift. In this work, we show that single photon superradiance and cooperative Lamb shift can be engineered in a semiconductor device by coupling spatially separated plasma resonances arising from the collective motion of confined electrons in QWs. These resonances hold a giant dipole along the growth direction z and have no mutual Coulomb coupling. They thus behave as a collection of macro-atoms on different positions along the z axis. Our device is therefore a test bench to simulate the low excitation regime of quantum electrodynamics.

Massless Dirac electrons in graphene and on the surface of 3D topological insulators such as Bi2Se3 demonstrate strong nonlinear optical response and support tightly confined surface plasmon modes. Although both systems constitute an isotropic medium for low-energy in-plane electron excitations, their second-order nonlinear susceptibility becomes non-zero when its spatial dispersion is taken into account. In this case the anisotropy is induced by in-plane wave vectors of obliquely incident or in-plane propagating electromagnetic waves. In this work we develop a rigorous quantum theory of the second-order nonlinear response and apply it to the parametric amplification of mid-infrared and Thz radiation. We show that a strong near-infrared or mid-infrared laser beam obliquely incident on graphene can experience a parametric instability with respect to decay into lower-frequency (idler) photons and THz surface plasmons. The parametric gain leads to efficient generation of THz plasmons. Furthermore, the parametric decay process gives rise to quantum entanglement of idler photon and surface plasmon states. This enables diagnostics and control of surface plasmons by detecting idler photons. A similar parametric process can be implemented in topological insulator thin films.

Here we present lifetime test results of 4 groups of quantum cascade lasers (QCL) under various aging conditions including an accelerated life test. The total accumulated life time exceeds 1.5 million device·hours, which is the largest QCL reliability study ever reported. The longest single device aging time was 46.5 thousand hours (without failure) in the room temperature test. Four failures were found in a group of 19 devices subjected to the accelerated life test with a heat-sink temperature of 60 °C and a continuous-wave current of 1 A. Visual inspection of the laser facets of failed devices revealed an astonishing phenomenon, which has never been reported before, which manifested as a dark belt of an unknown substance appearing on facets. Although initially assumed to be contamination from the environment, failure analysis revealed that the dark substance is a thermally induced oxide of InP in the buried heterostructure semiinsulating layer. When the oxidized material starts to cover the core and blocks the light emission, it begins to cause the failure of QCLs in the accelerated test. An activation energy of 1.2 eV is derived from the dependence of the failure rate on laser core temperature. With the activation energy, the mean time to failure of the quantum cascade lasers operating at a current density of 5 kA/cm² and heat-sink temperature of 25°C is expected to be 809 thousand hours.

Quantum cascade (QC) lasers achieve population inversion by selecting quantum wells (QW) thicknesses so that the inherent scattering mechanisms ensure a higher population of electrons in the upper laser state compared to the lower laser state. Previously, longitudinal optical (LO) phonons have been considered the fastest, most significant scattering process in QC lasers. Recently, it has been shown that interface roughness (IFR) can have substantial effects in determining the effective lifetimes within QW systems [1]. Simulations have shown that IFR scattering lifetimes can be the dominant scattering process for selected QW configurations [2]. Here we have designed and fabricated three QC structures, which differ in the positioning of a strategically placed monolayer barrier to selectively affect the IFR scattering lifetimes of the energy levels in the QC structures. Initial current-voltage characteristics suggest a shorter carrier transit time through the QC structure due to increased interface roughness interactions. We also observed an expected narrowing of the EL spectra based on these same interactions. Using these results, we have also designed a QC laser using IFR scattering as the determining process for maintaining population inversion. By using IFR scattering, we were able to design an energy separation between the lower laser level and subsequent injector levels much greater than the LO phonon energy without compromising fast carrier depopulation from the lower laser level. This in effect opens doors for completely new intersubband design techniques. This work is supported in part by MIRTHE (NSF-ERC).

Interband cascade lasers (ICLs) have proven to be efficient semiconductor sources of coherent mid -infrared (mid-IR) radiation. Single mode distributed-feedback (DFB) ICLs are excellent high-resolution spectroscopic sources for targeting important molecular species in the mid-IR fingerprint region, but are limited to a narrow spectral tuning range. Recent developments in multi-heterodyne spectroscopy with multi-mode Fabry-Perot (FP) lasers have enabled significant progress towards broadband high-resolution spectroscopic sensing applications in the mid-infrared. Here, we characterize the mode structure and tuning properties of multi-mode FP-ICLs for the purpose of evaluating the feasibility of ICL-based multiheterodyne spectroscopy.

Conditions of fabrication of first order distributed-feedback surface gratings designed for single-mode Al_0.45Ga_0.55As/GaAs quantum cascades lasers with the emission wavelength of about 10μm are presented. The 1 μm-deep rectangular-shaped gratings with the period of about 1.55 μm and duty cycle in the range of 65-71% made by the standard photolithography are demonstrated. The wavenumber difference of about 7 cm^-1 at 77 K is observed for the radiation emitted by lasers fabricated from the same epitaxial structure with ridge widths in the range of 15-25 μm. Moreover, the emission wavelength of the lasers could be tuned with temperature at a rate of 1 nm/K in the temperature range of 77-120 K. The full width at half maximum of the emitted spectra is ~ 0.4 cm^-1.

In this paper we present the development of the instrumentation for accurate evaluation of the thermal characteristics of quantum cascade lasers based on CCD thermoreflectance (CCD TR). This method allows rapid thermal characterization of QCLs, as the registration of high-resolution map of the whole device facet lasts only several seconds. The capabilities of the CCD TR are used to study temperature dissipation schemes in different designs of QCLs. We report on the investigation of thermal performance of QCLs developed at the Institute of Electron Technology, with an emphasis on the influence of different material system, processing technology and device designs. We investigate and compare AlInAs/InGaAs/InP QCLs (lattice matched and strain compensated) of different architectures, i.e., double trench and buried heterostructure (BH) in terms of thermal management. Experimental results are in very good agreement with numerical predictions of heat dissipation in various device constructions. Numerical model is based on FEM model solved by commercial software package. The model assumes anisotropic thermal conductivity in the AR layers as well as the temperature dependence of thermal conductivities of all materials in the project. We have observed experimentally improvement of thermal properties of devices based on InP materials, especially for buried heterostructure type. The use of buried heterostructure enhanced the lateral heat dissipation from the active region of QCLs. The BH structure and epilayer-down bonding help dissipate the heat generated from active core of the QCL.

Recently, W-class photonic-crystal surface-emitting lasers (PCSELs) with both a single spectrum and narrow spot beam pattern are reported. These highly coherent PCSEL properties cause a highly bright laser light that is useful for various applications. To improve the PCSEL output power, it is important to enlarge the emitting area to reduce the heat generation effect. However, multi-mode oscillation occurs in a broad emitting area because the difference in the threshold gain between the fundamental and higher modes becomes narrower as the emitting area is broadened. In this work, we fabricate PCSELs with double-hole lattice points that decrease the optical confinement to prevent multi-mode oscillation. The fabricated device, consisting of an AlGaAs/InGaAs material system designed to be oscillated at a wavelength of 940nm, has an emitting area of 300 × 300 μm². In a square lattice photonic crystal whose lattice period equals the lasing wavelength embedded in PCSELs, the distance between the centers of the double hole is set to one quarter of the lasing wavelength to decrease in-plane coupling caused by interference. We confirm that this device is oscillated at the Γ point of band edge A in the photonic band structure. The peak power is more than 5 W under pulse operation at 10 A. The device has a narrow beam divergence of less than 1° and single lobe spectrum in spite of the broad emitting area, so these double-hole lattice points are an effective structure to improve the PCSEL output power.

This paper proposes a design for the monolithic high-contrast mirror designed for infrared radiation. We use a fully vectorial model to search for the construction parameters of semiconductor monolithic high-contrast grating (MHCG) mirror providing maximal power reflectance. Such mirror can play a role of optical coupler, being alternative for distributed Bragg reflectors (DBRs). DBRs for mid- and long-wavelength infrared radiation are technologically highly demanding in terms of uniform quarter-wavelength layers control. Our results comprise a complete image of possible highly reflecting MHCG mirror constructions for potential use in optoelectronic infrared devices and systems.