In this paper, a ring cavity of Er:YAG laser with a single corner cube prism is investigated. Due to the depolarization effect of the corner cube, the tunable output coupling ratio was 0.25% to 72.67% by changing the angle of the λ / 4 plate according to the calculation results of Jones matrix. An experiment for checking the anti-detuning performances of the single corner cube cavity was also carried out. The results indicated that the output power was stable at the rotating angles of <3.06 deg and 1.637 deg along the vertical and horizontal directions, respectively. Under continuous wave operation, a 5.4 W vertically-polarized laser of 1645.1 nm was acquired through double polarizers with the beam quality factors (M2) of 1.17 in the x direction and 1.42 in the y direction, and the slope efficiency was 45.47%. Additionally, under the condition of a pulse-repetition-frequency (PRF) of 200 Hz, the pump power of 29.04 W, a maximum pulse energy of 2.2 mJ was realized, and the minimum pulse width was 86 ns, leading to a peak power of 25.58 KW.
We reported an actively mode-locked Ho:LuVO4 laser pumped with a Tm-doped fiber laser as the pump source for the first time. In the continuous wave (CW) mode, the maximum output power of 3.07 W at the absorbed pump power of 16.3 W was achieved with a central wavelength of 2073.8 nm, corresponding to an optical–optical conversion efficiency of 18.8%. The beam quality factor M2 was calculated to be 1.4. In CW mode-locked operation, the maximum laser output of 3.04 W at the same pump power was obtained with the same central wavelength of 2073.8 nm, corresponding to an optical–optical conversion efficiency of 18.7%. The repetition rate of the mode-locked pulse was 82.7 MHz with a single pulse energy of 36.8 nJ and pulse duration of 363.3 ps.
A repetition-frequency-controllable double Q-switched (DQS) Ho:LuAG laser at 2098.34 nm with acousto-optic modulator (AOM) and Cr2+:ZnS saturable absorber (SA) was investigated. The maximum output power of 5.3 W was obtained at the AOM repetition frequency (RF) of 3.72 kHz, corresponding to the slope efficiency of 29.8%. The largest pulse energy of 2.8 mJ with the shortest pulse width of 54.2 ns was observed at the AOM RF of 2.64 kHz. Compared with the passively Q-switched Ho:LuAG laser, the DQS Ho:LuAG laser could generate shorter pulse width and larger pulse energy, and its RF could be controlled by the AOM RF.
A high power ZnGeP2 (ZGP) optical parametric oscillator (OPO) with good beam quality pumped by a Q-switched Ho:YAG laser was demonstrated. The maximum output power of the ZGP OPO with a four-mirror ring cavity was about 5.04 W around 8.1 μm with 83.9 W Ho incident pump power, corresponding to a slope efficiency of 9.2 %. The ZGP OPO produced 36.0 ns far-IR pulse laser in the 8.0-8.3 μm spectral regions. The beam quality was measured to be M2~1.6 at the highest output power.
We present the experimental results on the laser characteristics of diode-pumped passively Q-switched Tm,Ho:GdVO4 and Tm,Ho:YVO4 lasers with a Cr2+:ZnS saturable absorber emitting in the 2-μm range. The Tm,Ho:GdVO4 laser exhibits better performance than the Tm,Ho:YVO4 laser. The minimum pulse duration of 32.7 ns is obtained with the pulse energy of 0.30 mJ, corresponding to the peak power of 9.1 kW. The slope efficiencies of continuous wave and passively Q-switched Tm,Ho:GdVO4 lasers are 49.9% and 36.5%, corresponding to the Q-switching efficiency of 70.2%.
The second harmonic generation (SHG) of Q-switched Ho:LuAG laser in a KTP crystal was demonstrated. Under the Type II phase matching conditions, we obtained the maximum second harmonic energy per pulse of 6.82μJ and the minimum pulse width of 67.3ns at 1050.30nm in the fundamental wavelength of 2100.65nm, corresponding to a peak power of about 0.101kW. By inserting a 0.05mm-thickness YAG uncoated etalon, the maximum second harmonic energy per pulse of 4.83μJ and the minimum pulse width of 70.6ns at 1046.89nm was obtained in the fundamental wavelength of 2093.86nm, corresponding to a peak power of about 0.068kW.
A compact continuous-wave and actively Q-switched Ho:LuVO4 laser pumped by a 1.94 μm Tm:YAP laser is demonstrated. The maximum output power of 6.7 W at 2058.13 nm in continuous-wave regime is obtained at an absorbed pump power of 17.8 W, corresponding to a slope efficiency of 48.4%. For Q-switched operation, average output power of 6.65 W and pulse width of 22.3 ns are obtained with a repetition frequency of 20 kHz, corresponding to a central wavelength of 2058.13 nm. In addition, different Q-switched pulses at repetition frequencies of 20, 30, 40, 50, and 60 kHz are investigated comparatively.
A continuous wave (CW) Tm:YAP laser resonantly pumped Ho:YLF laser in CW mode and passive Q-switched (PQS) mode with multilayer graphene as a saturable absorber is reported. A comparison analysis of laser performances with two different output couplers is carried out. In PQS mode, an maximum average output power of 2.26 W is obtained, corresponding to a slope efficiency of 20.7%. The minimum pulse width observed is 651.9 ns with a center wavelength of 2057.16 nm with a 300-mm radius curvature and 50% transmission output coupler. Meanwhile, the maximum pulse repetition frequency of 59.2 kHz is obtained. The beam quality factor of M2 was 1.2, which is the near diffraction limit. The results show that multilayer graphene can be used as a saturable absorber in a Ho:YLF laser around a 2-μm wavelength.
We report a continuous wave (CW) Tm:YLF laser-resonantly pumped Ho:LuAG laser in CW mode and passive Q-switched (PQS) mode with multilayer graphene as a saturable absorber. The lasing performance with different output couplers is analyzed. The best result was obtained with −150-mm radius curvature and 10% transmission output coupler. Under the CW mode, Ho:LuAG laser generated a maximum 1.3-W output power at the center wavelength of 2100.65 nm, corresponding to a slope efficiency of 34.6%. In PQS mode, the minimum pulse width observed is 784.7 ns with a center wavelength of 2100.65 nm at the pump power of 5.4 W. Meanwhile, the maximum output power is 0.37 W with a pulse repetition frequency of 47.3 kHz. The results show that the multilayer graphene can be used as a saturable absorber in a Ho3+-doped laser around a 2-μm wavelength.
This paper report the A-O Q-switched LD end pumped 8% Tm, 1.4%Ho:YLF laser. The fiber-coupled pump laser deliver maximum 15W around 792nm At 10 KHz pulse repetition frequencies (PRF), The average output power of 4.1 W, the pulse width of 32ns and peak power of 0.012MW at 2.05um were achieved. The pulse fluctuation is less than ± 2%. The pulse amplitude instability at last higher rate equation was analyzed.
A room-temperature Tm,Ho:YLF laser is constructed with a 2.5-mm-long Tm(6%) and Ho(0.4%) co-doped yttrium lithium fluoride crystal pumped by a laser diode operating at 792nm. The output power as a function incident pump power at different output coupler transmission values is given. At room temperature, the laser operates on a single transverse mode (TEM00) at 2.066μm, the laser threshold pump power is 55mW, and its maximum output power and optical-to-optical conversion efficiency are 388mW and 14.1% respectively. At the same time, the output power and optical-to-optical conversion efficiency as a function of incident pump power at different temperatures are obtained. Furthermore, the experimental results are explained reasonably.
In this paper, we report a high efficient and high power continuous wave diode-pumped cryogenic Tm(5% at.), Ho(0.5% at.):GdVO4 laser. One pumping source of Tm,Ho:GdVO4 laser is a fiber-coupled laser diode with fiber core diameter of 0.4 mm and numerical aperture (N. A.) of 0.3, supplying 14.8 W power at 793.6 nm. Another fiber-coupled LD radiation wavelength is centered at 805 nm with 0.22 N.A. and the same core diameter delivering power of greater than 30 W. For input pump power of 13.6 W at 794.2nm, the maximum output power of 4.2W, optical-to-optical conversion efficiency of 31% and slope efficiency 38% have been attained at 2.048 μm. The maximum cw power of 7.9-W is achieved by 805 nm LD under power of 26 W, corresponding to 40% optical-optical conversion efficiency relative to absorbed pumping power, which is close to quantum limited efficiency of 2 μm laser.
In this paper, we report a high power of cryogenic cooling Tm(8 at %), Ho(1.4 at %):YLF dual end pumped by two fiber coupled laser diodes at 792nm. Each pumping laser head delivers 15W power in an inner fiber core area of 0.4mm and numerical number of 0.3. The highest continuous-wave (cw) power of 10.2W at 2.051μm is attained under pumping power of 30W, corresponding to optical-optical conversion efficiency of 33%, and the slope efficiency is greater than 36%. The maximum acousto-optical Q-switched quasi-continuous wave output power is 9.2 W at pulse repetition frequency of 10kHz, corresponding to greater than 90% extraction efficiency in the full-width half-maximum pulse width of 34ns.
We have developed a high efficient, all-solid-state approach by using potassium titanyl phosphate (KTP)-based optical parametric oscillator to frequency shift Nd:YAG 1.064 micrometer to eye-safe wavelength at 1.57 micrometer. To reduce the threshold of KTP OPO, we reflected back the deleted pump wave according to original light path. The maximum energy conversion efficiency 64% and quantum conversion efficiency 94% was achieved when the OPO was pumped by Nd:YAG laser at 1064 nm.
Potassium Titanium Oxide Phosphate (KTP) is a new nonlinear frequency-conversion crystal. It has high nonlinear coefficient, high damage threshold, easily-polished surface, and a broad transparency range. In this paper, the calculation method of angle phase-matching for parametric generation in KTP was presented. The angle phase-matching curve and their characteristics in KTP pumped by 532 nm, 694.3 nm radiation were calculated and analyzed. The propagating principal plane (x-y plane) and 56 degree(s) cut angle to z-axis were selected in our experiment, and the measured results agreed well with the calculated ones. The quality of laser beam is an important factor of affecting OPO threshold fluence and conversion efficiency, so the phase-conjugate technology of Stimulated Brillouin Scattering (SBS) for improving the pump laser beam quality was discussed and applied to the pump laser system. The tuning curves and output energy of KTP OPO pumped by Ruby laser (0.6943 micrometers ), the second harmonic of Nd:YAG (0.532 micrometers ) were measured and compared with the theoretical cases. An important result was obtained that the amplified back SBS light which was employed to pump KTP OPO could greatly reduce the OPO threshold.
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