Μm Optical Parametric Oscillator Research Articles

Compact 2-μm Hundred Hertz optical parametric oscillator Based on KTP crystal

A 100 Hz compact 2 μm optical parametric oscillator (OPO) based on a type II non-critically phase-matched KTiOPO4 crystal (KTP) was reported. The monolithic KTP crystal was pumped with a passively Q-switched 1064 nm Nd:YAG laser. At a repetition rate of 100 Hz and a single pulse energy of 5.8 mJ of pump light, a 2128-nm laser output was achieved with a maximum of 1.17 mJ of parametric light at the degenerate point, with a parametric light pulse width of approximately 10.5 ns, corresponding to a pump to parametric light conversion efficiency of 20.1 %.

High Pulse Energy, Narrow Linewidth 6.45 μm from an Optical Parametric Oscillator in BaGa4Se7 Crystal

This paper presents a high pulse energy, narrow linewidth, mid-infrared (MIR) laser at 6.45 μm, based on a BaGa4Se7 (BGSe) crystal optical parametric oscillator (OPO) pumped by 1.064 μm laser. The maximum pulse energy at 6.45 μm was up to 1.23 mJ, with a pulse width of 24.3 ns and repetition rate of 10 Hz, corresponding to an optical–optical conversion efficiency of 2.1%, from pump light 1.064 μm to idler light 6.45 μm. The idler light linewidth was about 6.8 nm. Meanwhile, we accurately calculated the OPO phase-matching condition at BGSe crystal pumped by 1.064 μm laser, and a numerical simulation system was performed to analyze the input–output characteristics at 6.45 μm, as well as the effect of crystal length on the conversion efficiency. Good agreement was found between measurement and simulation. To the best of our knowledge, this is the highest pulse energy at 6.45 μm, with the narrowest linewidth for any all-solid-state MIR ns laser in BGSe-OPO pumped by simple 1.064 μm oscillator. This simple and compact 6.45 μm OPO system, with high pulse energy and narrow linewidth, can meet the requirements for tissue cutting and improve tissue ablation accuracy.

Narrow linewidth 2.1 μm optical parametric oscillator with intra-cavity configuration based on wavelength-locked 878.6 nm in-band pumping

We report on an intra-cavity optical parametric oscillator (OPO) based on MgO-doped periodically poled lithium niobate (MgO:PPLN) crystal in-band pumped by a wavelength-locked 878.6 nm laser diode (LD). A narrow linewidth 2.1 μm laser output is obtained by using a reflection volume Bragg grating (VBG). The stability of the resonator under high pump power and the spot mode matching of the parametric laser oscillation process are considered comprehensively to determine the optimal cavity parameters. In the experiment, a narrow linewidth of 2.1 μm maximum output power of 4.7 W is obtained with the pulse duration of 8.55 ns, the linewidth of 1.89 nm at 80 kHz repetition rate, corresponding to the maximum optical-optical conversion efficiency of 11.6%.

Wavelength-Locked 878.6 nm In-Band Pumped Intra-Cavity 2.1 μm Optical Parametric Oscillator* *Supported by the National Natural Science Foundation of China under Grant No 61505013, the Postdoctoral Science Foundation of China under Grant No 2016M591466, and the Science and Technology Department Project of Jilin Province under Grant Nos 20170204046GX and 20190101004JH.

We report herein a high-power folded intra-cavity 2.1 μm optical parametric oscillator (ICOPO) which is the first example of an ICOPO that utilizes a wavelength-locked 878.6 nm in-band pumped Nd:YVO4 laser as the pump source. The thermal effect of PPMgLN crystal and the divergence angle of the incident laser are considered comprehensively to determine the 2128 nm degenerate temperature. In the experiment, the functions of different output coupler transmittances and different repetition rates on the parametric laser output power are studied, respectively. The temperature versus parametric laser output power in an in-band pumped non-wavelength-locked 880 nm laser diode (LD) and in a wavelength-locked 878.6 nm LD is compared. A maximum output power of 5.87 W is obtained at the pump power of 56.9 W when the repetition rate is 80 kHz. The corresponding conversion efficiency is 14.55%, with a linewidth of 73.65 nm and pulse width of 3.62 ns. The wavelength-locked 878.6 nm LD in-band pumping technology can stabilize the 2.1 μm laser output power of Nd:YVO4 crystal effectively in the environment of intense temperature change.

High-efficiency, tunable 8-9 μm BaGa4Se7optical parametric oscillator pumped at 21 μm

A high-efficiency, tunable 8-9 μm optical parametric oscillator with a type-II phase-matching BaGa4Se7 crystal pumped by a 2090.7 nm acousto-optical Q-switched Ho:YAG laser was demonstrated for the first time. A maximum average idler output power of 314 mW at 8925.7 nm and 1 kHz was achieved with a pulse duration of 16 ns and a spectral bandwidth of 67.8 nm under the incident pump power of 9.58 W, corresponding to a slope efficiency of 7.44% and quantum slope efficiency of 32%. Furthermore, the idler tuning range of 8-9 μm was demonstrated. The results indicate the potential of BaGa4Se7 pumped at 2.1 μm as a candidate for realizing high-efficiency long-wavelength infrared laser radiation.

High-efficiency intracavity 2 μm degenerate optical parametric oscillator

A high-efficiency 2 μm optical parametric oscillator based on MgO-doped periodically poled LiNbO3 intracavity pumped by a 1.064 μm Q-switched Nd:YVO4 laser is reported. With the intense fluence inside the laser cavity, a maximum 2 μm average power of 3.5 W is obtained at 15 kHz repetition rate in a degenerate state. A maximum optical-to-optical conversion efficiency of 17.5% with a slope efficiency of 25% is achieved when the laser diode power is 20 W. To the best of our knowledge, the efficiency is the highest ever achieved from an intracavity degenerate optical parametric oscillator in 2 μm region. The pulse duration of 2 μm is 1.4 ns, which is much shorter than that of 1.064 μm. A bandwidth of 30 nm is obtained at a degenerate wavelength of 2128 nm. The M2 values for the 2 μm beam are 3.47 and 3.54 in the horizontal and vertical directions, respectively. The standard deviation of the power fluctuation is ～ 2% at the maximum power in half an hour.

A highly efficient 3.2 μm optical parametric oscillator pumped by a passively Q-switched Nd:YVO4 laser

We describe a compact all-solid-state singly resonant optical parametric oscillator (SRO) based on a Cr4+: YAG Q-switched Nd:YVO4 laser. The SRO is based on periodically poled MgO:LiNbO3 (PPMgLN) as the nonlinear material. By exploiting a 35 mm PPMgLN crystal, we achieved the SRO operation threshold at a pump power of only 140 mW. At 1.78 W of pump laser with a pulse width of 10 ns and a repetition of 50 kHz, 360 mW average power at 3.2 μm and a mid-infrared conversion efficiency of 20% were achieved.

1.8 μm optical parametric oscillator based on KTiOPO4

A 1.8 μm optical parametric oscillator pumped by a diode end-pumped acousto-optically Q-switched Nd:YAG is demonstrated. A 30-mm-long KTiOPO4 crystal cut with an angle of θ = 59.4°, φ = 0° is employed as the OPO crystal. 685 mW signal laser at 1.8 μm is obtained at the diode pump power of 13 W and the pulse repetition rate of 25 kHz. Simultaneously, 265 mW idler emission at 2.6 μm is obtained. The corresponded diode-to-OPO conversion efficiency is 7.3%. The pulse width of the signal and idler wave are measured to be 4.5 and 2.5 ns, respectively. This gives a peak power of 6.1 and 4.2 kW, respectively.

Narrow-band, tunable 2 μm optical parametric oscillator based on MgO:PPLN at degeneracy with a volume Bragg grating output coupler

A degenerate optical parametric oscillator (OPO) using an MgO:PPLN crystal and a volume Bragg grating (VBG) output coupler is presented. By changing the temperature of the VBG, the resonance of the OPO can be tuned exactly on the degeneracy point. A single-longitudinal and a multi-longitudinal mode pump scheme as well as the performance of the optical parametric oscillator on and off degeneracy are compared. It was found that the multi-longitudinal mode pump setup provides superior results with respect to spectral width and stability at degeneracy. At 2128.4 nm, a spectral width of less than 0.7 nm, an output power of 1.7 W with a slope efficiency of 31.8%, and low power fluctuation of 0.3% were achieved.

Efficient 18 μmKTiOPO_4 optical parametric oscillator pumped within an Nd:YAG/SrWO_4 Raman laser

A 1.8 μm optical parametric oscillator (OPO) based on a noncritically phase-matched KTiOPO4 crystal is demonstrated. OPO and stimulated Raman scattering techniques are successfully combined in an acousto-optically Q-switched Nd:YAG/SrWO4 Raman laser. The device efficiently realizes three steps of conversion: from a laser diode wavelength of 808 nm to the fundamental wavelength of 1064 nm; next, to the Stokes wavelength of 1180 nm; and finally to the OPO signal wavelength of 1810 nm. With an incident diode power of 7.2 W and a pulse repetition rate of 15 kHz, an average signal power of 485 mW is obtained with a diode-to-signal conversion efficiency of 6.75%. The beam quality factors (M2) of the signal wave in both horizontal and vertical directions are measured to be 1.7±0.2. The numerical output power results of the system, the thermal lensing, and the stability parameter of the cavity are also discussed.

Mid-infrared optical parametric oscillator based on ZnGeP2 pumped by 2- \mum laser

We present a 3~5 μm optical parametric oscillator (OPO) based on ZGP pumped by KTP OPO 2.1-μm laser. The tuning curves of ZGP OPO are calculated. The x 6 x 18 (mm) ZGP crystal, whose end faces are antireflection coated at 2.1 and 3.7~4.6 μm, is cut as Θ =53.5o, Φ =0o. When the pump power of 2.1-μm polarized laser is 15 W at 8 kHz, 5.7-W output power and 46.6% slope efficiency are obtained with a ZGPtype I phase match. Central wavelengths of the signal and idler lasers are 4.10 and 4.32 μm, respectively. Pulse duration is about 27 ns. Beam quality factor M2 is better than 1.8. The tunability of 3~5 μm can be achieved by changing the angle of the ZGP crystal.

Pulse-series 1.57 μm optical parametric oscillator pumped by a Q-switched Nd:YAG laser with a variable reflectivity mirror

A method of generating 1.57 μm pulse-series eye-safe laser based on optical parametric oscillator (OPO) was developed. The 1.57 μm pulse-series OPO was pumped by a Q-switched Nd:YAG laser with a variable reflectivity unstable resonator. Every pulse-series includes three micro-pulses, and the pulse repetition rates, pulse numbers and pulse intervals were adjustable. The maximum output energy of the 3-micro-pulse-series was 274 mJ. The optical-optical efficiency of the OPO was about 40%.