Low-threshold, high-efficiency, high-repetition-rate optical parametric generator based on periodically poled LiNbO3

We report a high-repetition-rate optical parametric generator (OPG) with a periodically poled lithium niobate (PPLN) crystal pumped by an acousto-optically Q-switched CW-diode-end-pumped Nd:YVO_4 laser. For the maximum 1064nm pump power of 970mW, the maximum conversion efficiency is 32.9% under the conditions of 250℃, 1064nm pulse repetition rate of 22.6kHz and pulse width of 12ns, and the PPLN OPG threshold in the collinear case is less than 23.7μJ. The output power increases with the increase of the crystal temperature. The 1485－1553nm signal wave and 3383－3754nm idler wave are obtained by changing the temperature and the angle of the PPLN crystal.     

Harmonically pump a femtosecond optical parametric oscillator to 1.13 GHz by a femtosecond 515 nm laser

We demonstrate a harmonically pumped femtosecond optical parametric oscillator(OPO)laser using a frequency-doubled mode-locked Yb:KGW laser at a repetition rate of 75.5 MHz as the pump laser.Based on a bismuth borate nonlinear crystal,repetition rates up to 1.13 GHz are realized,which is 15 times that of the pump laser.The signal wavelength is tunable from 700 nm to 887 nm.The maximum power of the signal is 207 m W at the central wavelength of 750 nm and the shortest pulse duration is 117 fs at 780 nm.The beam quality(M^2 factor)in the horizontal and vertical directions of the output beam are 1.077 and 1.141,respectively.     

A 1kHz Fe:ZnSe Laser Gain-Switched by a ZnGeP_2 Optical Parametric Oscillator at 77 K

We demonstrate a Fe:ZnSe laser gain-switched by a 2.9 m ZnGeP_2 optical parametric oscillator under pulse repetition frequency of 1 kHz at liquid nitrogen temperature of 77 K. The maximum output power is 63 m W with pulse duration of 34.4 ns. The wavelength covers 3686.6–4088.6 nm and centers at 3897.7 nm. The output power decreases with increasing the temperature of the crystal in 77–222 K.     

High-Average-Power Nanosecond Quasi-Phase-Matched Single-Pass Optical Parametric Generator in Periodically Poled Lithium Niobate

A pulsed nanosecond optical parametric generator (OPG) in periodically poled lithium niobate (PPLN) crysal is presented. The pump laser is an acousto-optically Q-switched Nd:YVO4 laser with the maximum average power of 6.58 W. When the repetition rate is 50kHz and the pulse width of the pump source is 80ns, the maximum average total output power of the single-pass PPLN OPG is about 1.9 W, which includes 1.322 W of 1.536μm signal radiation. The length of the PPLN crystal is only 38.7mm (at room temperature) with a grating period of 28.93μm (at room temperature). The 1.502-1.536μm signal radiation and 3.652-3.465μm idler radiation are obtained by adjusting the PPLN crystal temperature from 155℃ to 250℃.     

High-Efficiency High-Power Nd：YAG Laser under 885 nm Laser Diode Pumping

A high-efficiency high-power Nd：YAG laser under 885 nm laser diode （LD） pumping is demonstrated. The laser crystal is carefully designed, and the overlapping between the pump modes and the laser modes is optimized. The maximum output power at 1064 nm is 87W under the absorbed pump power 127.7 W, corresponding to a slope efficiency of 72.4% and an optical-optical efficiency of 68.1%. The optical-optical efficiency is 58.4% for the pump power emitted directly from the LD. To our best knowledge, this is the maximal optical-optical conversion efficiency obtained for the LD end-pumped Nd：YAG lasers so far.     

An efficient intracavity-pumped KTP optical parametric oscillator at 1572 nm

We demonstrate an efficient and eye-safe wavelength intracavity optical parametric oscillator (OPO), based on a KTP crystal inside a Q-switched Nd:YVO4 laser end pumped by a fiber-coupled diode laser. In the acousto-optic Q-switched operation with the pulse repetition rate of 10 kHz, a 1572-nm eye-safe laser with the average power of 237 mW at the incident pump power of 5.64 W is obtained. Under the pulse repetition rate of 5 kHz, the signal light with pulse width of 2 ns and peak power of 18.5 kW is achieved. The conversion efficiency of the average power is 4.2% from pump diode to OPO signal output and the signal pulse duration is about 13 times shorter than that of the depleted pump light.     

A Low-Pump-Threshold High-Repetition-Rate Intracavity Optical Parametric Generator Based on Periodically Poled Lithium Niobate

A low-pump-threshold high-repetition-rate intracavity optical parametric generator （IOPG） by using a periodically poled lithium niobate （PPLN） is reported. The PPLN, which is 18.7mm long and has a grating period of 28.93tzm at room temperature, is inserted in a diode-end-pumped Nd：YV04 laser with an acousto-optic Q switch. The parametric generation threshold is 1.3 W （diode laser power） at a Q-switch repetition rate of 19 kHz. At an incident diode pump power of 5 W, an average signal output power of 280mW has been achieved. The signal pulse duration is approximately 85 ns. By changing the crystal temperature from 120℃ to 250℃, the signal wavelength can be tuned from 1.493μm to 1.538μm.     

Diode-Pumped Quasi-Three-Level Passively Q-Switched Nd：GGG Laser with a Codoped Nd,Cr：YAG Saturable Absorber

We demonstrate the first quasi-three-level passively Q-switched Nd：GGG laser at 937nm using a Nd, Cr：YAG crystal as the saturable absorber. The dependences of the average output power, the repetition rate and the pulse width on the incident pump power are obtained. A maximum average output power of 1.18 W with repetition rate of 35kHz and pulse width of 45ns is achieved at an incident pump power of 18.3 W. The corresponding optical-to-optical and slope efficiencies are 6% and 10%, respectively.     

Watt-level Pr^3+:YLF deep red laser pumped by a fiber-coupled blue LD module or a single-emitter blue LD

A power-scaled laser operation of Pr:YLi F4(YLF)crystal at 720.9 nm pumped by a 443.6 nm laser diode(LD)module was demonstrated.The 20 W module was used to pump the Pr:YLF crystal,and a maximum output power of 3.03 W with slope efficiency of 30.04%was obtained.In addition,a 5 W blue LD was also used to pump the Pr:YLF laser,and a maximum output power of 0.72 W was obtained at room temperature.The output power was limited by the wavelength mismatch between the single-emitter LD and the absorption peak of the crystal.     

The influence of stimulated temperature-dependent emission cross section on intracavity optical parametric oscillator

In this paper, the influence of temperature on the intracavity optical parametric oscillator(IOPO) is investigated by using the stimulated temperature-dependent emission cross section of laser crystal. The rate equations under plane wave approximation have been used for simulation of signal output pulse. Results show that the signal output pulse width is decreased by increasing the laser crystal temperature. Also, the signal output energy is increased by the increasing of the laser crystal temperature. The simulation results for IOPO based on Nd:YAG and Nd:YVO_4, show that the signal pulse energies are increased by 3.2 and 5.6 times respectively when the laser crystal temperature increased from 15℃ to 300℃. The presented model indicates that the temperature sensitivity of Nd:YVO_4-based IOPOs is more than that of Nd:YAG-based IOPOs which is expected from a physical point of view.     

High-average-power,high-repetition-rate dual signal optical parametric oscillator based on PPMgLN

<正>A high-average-power,high-repetition-rate dual signal optical parametric oscillator based on periodically poled MgO-doped lithium niobate(PPMgLN) with a phase-reversed grating is reported.The pump laser is an acousto-optically Q-switched Nd:YVO_4 laser with a maximum average power of 7.6 W.When the repetition rate is 50 kHz and the pulse width of the pump source is 23 ns,the maximum average dual signal output power is about 1.9 W,leading to a conversion efficiency of 25%.Over a 30-min interval,the instability of the signal power measured is less than 0.5%.     

A high-power high-stability Q-switched green laser with intracavity frequency doubling using a diode-pumped composite ceramic Nd：YAG laser

We successfully obtain a high-average-power high-stability Q-switched green laser based on diode-side-pumped composite ceramic Nd:YAG in a straight plano-concave cavity. The temperature distribution in composite ceramic Nd:YAG crystal is numerically analyzed and compared with that of conventional Nd:YAG crystal. By using a composite ceramic Nd:YAG rod and a type-II high gray track resistance KTP (HGTR-KTP) crystal, a green laser with an average output power of 165 W is obtained at a repetition rate of 25 kHz, with a diode-to-green optical conversion of 14.68%, and a pulse width of 162 ns. To the best of our knowledge, both the output power and optical-to-optical efficiency are the highest values for green laser systems with intracavity frequency doubling of this novel composite ceramic Nd:YAG laser to date. The power fluctuation at around 160 W is lower than 0.3% in 2.5 hours.     

High power doubly resonant all-intracavity deep blue laser at 447 nm based on sum-frequency-mixing technology

A high power continuous-wave deep blue laser at 447 nm is obtained by using a doubly cavity and a type H critical phase matching KTP crystal for intracavity sum-frequency-mixing. With the incident pump power of 240 W for the Nd：YAP crystal and 120 W for the other Nd：YAP crystal, the deep blue laser output of 5.7 W at 447 nm with near fundamental mode is obtained, and the beam quality M^2 value equals 2.53 in both horizontal and vertical directions at the maximum output power. The power stability is better than 2% at the maximum output power during half an hour. The experimental results show that the intracavity sum-frequency mixing by doubly resonant is an effective method for high power blue laser.     

Diode-Pumped Passive Q-Switched 946-nm Nd：YAG Laser with 2.1-W Average Output Power

We demonstrate a diode-pumped passive Q-switched 946nm Nd: YAG laser with a diffusion-bonded composite laser rod and a co-doped Nd, Cr:YAG as saturable absorber. The average output power of 2.1 W is generated at an incident pump power of 14.3 W. The peak power of the Q-switched pulse is 643 W with 80kHz repetition rate and 40.8 ns pulse width. The slope efficiency and optical conversion efficiency are 17.6% and 14.7%, respectively.     

High power red laser generation by second harmonic generation with GTR-KTP crystal

In this Letter, a gray-tracking-resistant—potassium titanyl phosphate(GTR-KTP) crystal is used for intracavity frequency doubling red laser generation for the first time. Under the 808 nm LD pump power of 180 W, as high as 12.5 W of red laser output is obtained with the optimum repetition rate of 7 k Hz. Within the red laser power variation range between the maximum to 70%, a temperature tolerance is measured to be 35°C. The results prove that GTR-KTP should be a potential nonlinear crystal for red laser generation.     

Electro-optically Q-switched 946 nm laser of a composite Nd:YAG crystal

A depolarization phenomenon in an electro-optical crystal in a quasi-three-level 946 nm Nd:YAG laser is observed. A compensation of the thermal effects in electro-optical crystals is achieved by employing a quarter-wave plate, with one optical axis parallel to the laser polarization. This technique allows for the production of an electro-optically Q-switched 946 nm Nd:YAG laser at 1 k Hz. A maximum output power of 350 m W at 1 k Hz repetition frequency and 11 ns pulse duration are achieved with an output coupler of 10% transmission under the incident pump power of 11.1 W, corresponding to a peak power of ～32 k W.     

Simultaneous all-solid-state multi-wavelength lasers --- a promising pump source for generating highly coherent terahertz waves

A diode-end-pumped Nd:YAG dual-wavelength laser operating at 1319 and 1338 nm is demonstrated. The maximum average output power of the quasi-continuous wave linearly polarized dual-wavelength laser is obtained to be 2.1 W at a repetition rate of 50 kHz with an output power instability of less than 0.38% and beam quality factor M² of 1.45. Using the two lines, the highly coherent and narrow linewidth terahertz radiation of 3.23 THz can be generated in an organic 4-N, N-dimethylamino--methyl-stilbazolium tosylate (DAST) crystal. Meanwhile, the multi-wavelength red laser at 659.5, 664 and 669 nm is generated by frequency doubling and sum frequency processes in a lithium triborate (LBO) crystal. The average red laser output power is enhanced up to 1.625 W at a repetition rate of 15 kHz with an output power instability of better than 0.53% and beam quality factor M² of 6.05. Using the three lines, it is possible to generate the multi-wavelength THz radiation of 3.3, 3.43 and 6.73 THz in an appropriate difference frequency crystal.     

Low-threshold mid-IR MgO:PPLN optical parametric generation with high reflectivity mirror for signal wavelength

A low-threshold middle-infrared(mid-IR)MgO:PPLN optical parametric generation(OPG)pumped by a laser diode(LD)end-pumped Z-type Nd:YLF laser at 1047 nm is realized with high reflectivity(HR) mirror for signal.At repetition rate of 10 kHz,the OPG threshold of 50μJ has been achieved with HR mirror for signal.Compared with the threshold without mirror,the threshold decreases by 17%.Using HR mirror for pump at output side of crystal,the threshold of 40μJ is achieved.The 2.7-4.1μm continuous tunable output is produced with seven grating periods from 28.5 to 31.5μm and temperatures from 30 to 200℃.When the incident average pump power is 3 W,the OPG idler output power is 0.46 W at 3.26μm,which corresponds to optical-to-optical conversion efficiency up to 15.3%.     

Multi-wavelength continuous-wave Nd:YVO_4 self-Raman laser under in-band pumping

Multi-wavelength continuous-wave self-Raman laser with an a-cut composite YVO_4/Nd:YVO_4/YVO_4 crystal pumped by an 879-nm wavelength-locked laser diode is demonstrated for the first time. Multi-wavelength Raman lasers at 1168.4, 1176, 1178.7, and 1201.6 nm are achieved by the first Stokes shift of the multi-wavelength fundamental lasers at 1064, 1066.7, 1073.6, 1084, and 1085.6 nm with two Raman shifts of 890 and 816 cm~(-1). A maximum Raman output power of 2.56 W is achieved through the use of a 20-mm-long composite crystal, with a corresponding optical conversion efficiency of 9.8%. The polarization directions of different fundamental and Raman lasers are investigated and found to be orthogonal π and σ polarizations. These orthogonally polarized multi-wavelength lasers with small wavelength separation pave the way to the development of a potential laser source for application in spectral analysis, laser radar and THz generation.     

A periodically poled LiNbO3 in wavelength conversion optical parametric generator from 2 to 3.88 ——4.34 μm

A periodically poled lithium niobate （PPLN） optical parametric generator （OPG） pumped by a laser diode （LD）-pumped Q-switched Tm,Ho：GdVO4 laser operated at 2.048 μm with pump pulse of 25 ns and repetition rate of 10 kHz is reported. A continuous tunable middle-infrared （mid-IR） spectrum of 3.88 - 4.34 μm is obtained by changing the crystal temperature from 50 to 124℃. When the incident pump power is 3 W, the total OPG output power is 95 mW, corresponding to optical conversion efficiency of 3.2%.