Intracavity Optical Parametric Oscillator Research Articles

3 μm mid-infrared compact intracavity optical parametric oscillator based on KTA and MgO:PPLN

3 μm mid-infrared compact intracavity optical parametric oscillator based on KTA and MgO:PPLN

Exploring the criterion for the self-pulsing suppression of mid-IR intracavity OPO with self-Raman scattering.

The stimulated Raman scattering (SRS) from the Nd:YVO4 gain medium is originally employed to eliminate the self-pulsing effect from the intracavity optical parametric oscillator (OPO) for achieving a continuous-wave (CW) mid-infrared output. The SRS with a second-order pump-wave power depletion is applied as the damping for the coupling between OPO pump-wave relaxation oscillation and signal-wave depletion. The SRS threshold conditions for different cavity and diode-pumped mode size designs are theoretically and experimentally explored. By using different resonators, the CW mid-infrared output from 120 mW to 1.56 W at the diode pump power from 3 to 19.3 W can be successfully demonstrated.

Low-threshold CW eye-safe vortex generation from an intracavity pump-wave off-axis pumped OPO.

A low-threshold efficient setup for CW wavelength versatile vortex generation is proposed. The intracavity optical parametric oscillator is utilized for low-threshold operation. By using the pump-wave off-axis pumping for the signal-wave oscillator, high-order Hermite-Gaussian modes at the eye-safe region can be obtained, which can further generate a vortex via an astigmatism mode converter. The overall laser performance is additionally verified to be better by comparing it with the diode off-axis pumping method where the TEM1,0 pump wave was generated first for the signal-wave TEM1,0 mode oscillation. This method is expected to be further applied for more complicated structured light generation.

3.8 µm pulse burst self-optical parametric oscillator utilizing a programmable step-active Q-switch with Nd:MgO:PPLN crystal

This paper reports a 3.8 µm pulse burst self-optical parametric oscillator (SOPO) employing the Nd:MgO:PPLN crystal, achieving programmable mid-infrared pulse burst output based on step-active Q-switching technology. Building on the intracavity optical parametric oscillator (IOPO) theory, a theoretical model for the step-active Q-switched self-optical parametric oscillator is developed by introducing idler photon and step loss terms. The simulation results elucidate the evolution of population inversion and photon numbers and determine step-active Q-switching loss values for different sub-pulse numbers. Additionally, a 3.8 µm pulse burst laser output with a repetition rate of 10 kHz is experimentally achieved using the step-active Q-switching signal designed from the theoretical simulation. The effective programming of the step-active Q-switching signal achieves control over 2-4 sub-pulses, 260-1000 ns intervals, and any amplitude ratios. The experimental and simulation results demonstrate consistency, offering valuable insights for optimizing the Q-switching technology in other SOPO systems.

High-power idler-resonant intracavity KTA OPO driven by a dual-loss-modulated Q-switched mode-locked laser with AOM and Sb2Te3 nanosheets

By using Sb2Te3 nanosheets as saturable absorbers (SA) and an acousto-optic modulator (AOM), a laser-diode (LD) end-pumped idler-resonant KTiOAsO4 (KTA)-based intracavity optical parametric oscillator (IOPO) pumped by a dual-loss-modulated Q-switched mode-locked (QML) laser has been realized. The experimental results show that the pulse widths of the Q-switched envelope and the mode-locking pulse numbers underneath the Q-switched envelope decrease as the pump power increases. When the pump power reaches a certain value, only one mode-locking pulse underneath a Q-switched envelope exists, resulting in the generation of the subnanosecond mode-locking pulses of OPO with the repetition rate of AOM. The minimum mode-locking pulse durations of the signal and idler waves were measured to be 545 and 936 ps at an AOM frequency of 1 kHz and a diode pump power of 22.45 W, corresponding to the maximum peak powers of 648 and 185 kW, respectively. Furthermore, a set of coupled rate equations for the dual-loss-modulated QML laser-pumped intracavity idler-resonant OPO was formulated according to the Gauss distribution of intracavity photon density. The numerical simulations of these equations agree with the experimental results. These results collectively suggest the potential application of Sb2Te3 as a promising nanomaterial in the realm of optoelectronics.

The effects of thermalization on the performance of passively Q-switched IC-OPOs

In this paper, we report a new model for passively Q-switched intracavity optical parametric oscillators (IC-OPOs), using Cr:YAG as a Q-switch crystal. The model considers the effects of thermalization in the Nd:YAG laser crystal, excited state absorption in the Cr:YAG saturable absorber, nonlinear loss due to pump depletion in the nonlinear crystal, the thermal lens effect and the mode overlap of the fields within the nonlinear crystal. The calculated pulse width for the 1,064 nm pump light was 6.2 ns compared to the experimental result of 6 ns, while the signal wave was calculated to have a pulse width of 1.75 ns compared to the experimental result of 2 ns. The model is shown to accurately calculate both the temporal and output power characteristics of the IC-OPO, which has not been previously reported to the best of our knowledge.

Investigations on saturable absorption characteristic of PdS2 and its application to high-peak-power sub-nanosecond intracavity OPO

In this work, a unique pentagonal TMD material, palladium disulfide (PdS2) nanosheets were fabricated by the liquid-phase exfoliation (LPE) process, and the physical characteristics were also investigated. The nonlinear transmittance is measured by the power scanning method and the modulation depth is fitted to be 15.3%. Based on the transmittance curve, the saturable absorption parameters of PdS2 are calculated, including 5.85 × 10−19 cm2 ground-state absorption cross-section, 1.63 × 10−19 cm2 excited-state absorption cross-section, and 683.5 μs excited-state lifetime. By employing both PdS2 as a saturable absorber (SA) and an acousto-optic modulator (AOM), a doubly Q-switched and mode-locked (QML) laser-pumped intracavity KTiOPO4 (KTP) optical parametric oscillator (OPO) was realized. The pulse energy and the pulse width of the Q-switched envelope for signal wave have been measured. At higher pump power, the high-peak-power low-repetition-rate sub-nanosecond mode-locking pulse of signal wave is generated, in which there is only one mode-locked pulse underneath a Q-switched envelope. The measured shortest signal pulse duration is 530 ps, corresponding to a peak power of 337 kW, at an incident pump power of 9.81 W and an acousto-optic modulator (AOM) repetition rate of 1 kHz. In addition, by considering the Gauss distribution of intracavity photon density, a set of coupled rate equations for a doubly QML laser-pumped intracavity OPO was given and the numerical simulations agreed with the experimental results. These results indicate that PdS2 is a promising nonlinear optical material for optical applications in the near-infrared (NIR) region.

Sub-nanosecond single mode-locking pulse generation in an intracavity KTP optical parametric oscillator with a few-layer Bi2Te3 topological insulator saturable absorber

By utilizing the ultrasound-assisted liquid phase exfoliation process, Bi2Te3 nanosheets are synthesized and deposited onto a quartz plate to form a saturable absorber (SA), in which nonlinear absorption characteristics around 1 μm are investigated with a home-made Q-switched laser. With the as-prepared Bi2Te3 SA employed, a sub-nanosecond KTiOPO4 (KTP) based intracavity optical parametric oscillator (IOPO) pumped by a dual-loss-modulated Q-switched and mode-locked (QML) laser is successfully realized. With a short duration of sub-nanosecond and a repetition rate of several kilohertz (kHz), the signal wave’s single mode-locking pulse existed underneath a Q-switched envelope can be formed. At an incident pump power of 8.92 W and an acousto-optic modulator (AOM) repetition rate of 2 kHz, a signal wave’s single mode-locking pulse underneath a Q-switching envelope with a measured minimum pulse duration of 520 ps is accomplished. It is the first demonstration of such Bi2Te3 SA utilized in a solid-state QML IOPO laser, to the best of our knowledge. According to the experimental results, this provides an efficient and straightforward approach to acquire sub-nanosecond OPO signal wave pulses. Additionally, the relevant coupled rate equations are established, and the simulation results match the experimental results, revealing the potential of Bi2Te3 as a nanomaterial for optoelectronic applications.

Generating dual-wavelength VECSEL by selecting birefringence filter material and the application toward mid-infrared region via intracavity OPO.

A method for realizing a synchronized watt-level dual-wavelength vertical-external-cavity surface-emitting-laser (VECSEL) by using a tilted birefringence filter (BRF) is demonstrated. It is verified that by selecting suitable BRF material with different refractive index differences between extraordinary wave and ordinary wave, the dual-wavelength emission with a free spectrum range from sub-THz to tens of THz can be achieved. The output characteristics of such a dual-wavelength VECSEL are thoroughly investigated including its wavelength tunability and power difference. Finally, the intracavity optical parametric oscillator is applied to efficiently convert the dual-wavelength laser toward the mid-infrared region. The gain competition and longitudinal mode hopping performances for the multi-wavelength mid-infrared output are explored.

Theoretical study of diode pumped intracavity backward optical parametric oscillator based on periodically poled lithium niobate

Theoretical study of diode pumped intracavity backward optical parametric oscillator based on periodically poled lithium niobate

Diode-Pumped Intracavity OPO KTP/YAG:Nd3+ laser for Cr2+:ZnSe pumping

Electro-optically Q-switched side-pumped diode-pumped KTP/YAG:Nd3+ nanosecond laser system with an intracavity collinear optical parametric oscillation was proposed as a pump source for Cr2+:ZnSe laser. Energy parameters of Cr2+:ZnSe laser were investigated with respect to the wavelength of the pump laser. Under optimal conditions, pumping with laser pulses with an energy of 10.5 mJ and a duration of 7.2 ns at a wavelength of 1950 nm allowed to obtain 3.2 ns pulses at a wavelength of 2494 nm with slope optical-to-optical conversion efficiency of 5.5%.

Low-threshold dual-wavelength CW mid-IR laser from shared intracavity quasi-phase-matched OPO.

A low-threshold continuous wave dual-wavelength mid-infrared laser is demonstrated by using an intracavity optical parametric oscillator (OPO) with a dual-wavelength pump wave. To realize a high-quality dual-wavelength pump wave, a composite Nd:YVO4/Nd:GdVO4 gain medium is applied for a linear polarized state and synchronization output. With the quasi-phase-matching OPO process, it is found that the dual-wavelength pump wave shares equal signal wave oscillation and leads to a lower OPO threshold. Finally, a diode threshold pumped power of barely 2 W can be achieved for the balanced intensity dual-wavelength watt-level mid-IR laser.

High efficiency, low threshold, high repetition rate H-β Fraunhofer line light at 486.1 nm generation by an intracavity frequency-doubled optical parametric oscillator

High efficiency, low threshold, high repetition rate H-β Fraunhofer line light at 486.1 nm generation by an intracavity frequency-doubled optical parametric oscillator

Study on linewidth compression at 3.8 μm with multiple F-P etalon pumped by compound intra-cavity optical parametric oscillator

A compact, multiple F-P etalon and narrow linewidth intra-cavity single-resonant mid-infrared optical parametric oscillator based on MgO:PPLN is reported, which is composed of a 1064 nm gain cavity and a mid-infrared frequency conversion cavity. The narrow linewidth at 3.8 μm can be obtained indirectly through the linewidth compression at the fundamental wavelength and the signal wavelength. The linewidth at 3.8 μm is 0.73 nm without adjacent mode when the fundamental wavelength is acted by the single F-P etalon with the thickness of 2.5 mm and the signal wavelength is acted by the dual F-P etalon with the thickness of 2.5 mm and 0.5 mm. Meanwhile, the output power of 1.06 W is obtained, corresponding to the conversion efficiency of 2.41%, the pulse width of 11.17 ns is obtained synchronously, and the beam quality factor M2 at 3.8 μm are Mx2 = 1.92 and My2 = 1.87, respectively. It provides a method for intra-cavity pumped mid-infrared linewidth compression.

Theoretical and experimental study on gain competition adjustment of intracavity pumped dual-wavelength optical parametric oscillator using an aperiodically poled lithium niobate at approximately 3.30 and 3.84 μm

An intracavity pumped dual-wavelength optical parametric oscillator based on a single MgO:APLN crystal at approximately 3.30 and 3.84 μm was studied using a folded-type double cavity, which consists of a 1.06 μm resonator and dual-wavelength optical parametric oscillator. With the maximum incident diode power of 43.84 W, the maximum output powers of 1.43 W at 3.30 μm and 2.47 W at 3.84 μm were obtained under T = 70%@1.57 μm and T = 25%@1.47 μm at a repetition rate of 40 kHz, corresponding to conversion efficiencies of 3.26% and 5.63%, respectively. The pulse widths of 11.35 ns at 3.30 μm and 13.17 ns at 3.84 μm were obtained synchronously. A dual-wavelength optical parametric energy conversion model was set up to simulate the influence of the transmittance at resonant signal wavelengths on the output power of idler wavelengths. Both theoretical and experimental results demonstrated that the relationships in output power between 3.30 and 3.84 μm can be affected by adjusting the transmittance at signal wavelengths.

Compactly Efficient CW 3 to 4.5 μm Wavelength Tunable Mid-Infrared Laser in Optically Pumped Semiconductor Laser With Intracavity OPO

An efficient continuous-wave (CW) mid-infrared laser with a tunable wavelength range from 3 to 4.5 μm is demonstrated by using intracavity optical parametric oscillator (ICOPO). An optically pumped semiconductor laser (OPSL) is applied as the parent pumped laser gain medium to eliminate self-modulation effect caused by Nd-doped gain medium with ICOPO for fulfilling true CW emissions. Simultaneously, the OPSL gain chip with flip-chip packaging method can avoid mode hopping resulted from internal heat spreader etalon when strong depletion in ICOPO was achieved. The diode pump criteria of the OPSL is first investigated to prevent thermal roll over. By observing the spectral and temporal dynamics of the parent pumped OPSL with and without OPO operation, the true CW and mode-hop-free quality of the laser is verified. A low diode pump threshold of 2.67 W is obtained for the mid-IR idler emission and a total extracted idler power is 250 mW at a diode pump power of 8 W. Finally, the wavelength tunability is confirmed by adjusting the horizontal location of the multiple channel MgO:PPLN crystal, which indicated the feasibility of practical application in such a compact configuration.

Intracavity optical parametric oscillator: Model of dynamic system with different values of time delay for pump and signal radiation

Most of intracavity pumped optical parametric oscillators (OPO) are made nowaday according to a scheme with a single-resonance OPO located in the cavity of a pump laser. Usually the cavities of the pump and OPO (signal) emission have different values of round-trip time (delay). Aim of the study is therefore to build up the mathematical model of intracavity optical parametric oscillator (ICOPO) considered as a time-delay dynamic system with two values of delay in both cavities (the pump and signal). Methods. The model allows to analyze the steady state (equilibrium point) of the dynamic system and its stability with the help of characteristic equation’s solution. Results. Countless set of the characteristic equation roots is shown to consist of complex-conjugate pairs with imaginary parts which are nearly multiples of intermode beat frequencies in the pump and signal cavities. The diagram of stability depending on the position of nonlinear crystal in the resonator was built on the parameter plane. Features of the plane partition into the areas of stability/instabilty vs behavior of the characteristic equation roots are examined. Discussion. The results of the study allow to consider an ICOPO as the time-delay dynamic system thus adding to the physical picture of intracavity parametric oscillators.

Development of a deep-ultraviolet pulse laser source operating at 234 nm for direct cooling of Al+ ion clocks.

We report on the development of a 250-MHz 234 nm deep-ultraviolet pulse source based on a flexible wavelength-conversion scheme. The scheme is based on a frequency-doubled optical parametric oscillator (FD-OPO) together with a cascaded frequency conversion process. We use a χ(2) nonlinear envelope equation to guide the design of an intra-cavity OPO crystal, demonstrating a flexible broadband tunable feature and providing as high as watt-level of a frequency-doubled signal output centered at 850 nm, which is served as an input wave for the cascaded frequency conversion process. As much as 3.0 mW of an average power at 234 nm is obtained, with an rms power stability of better than 1% over 20 minutes. This deep-ultraviolet pulse laser source can be used for many applications in quantum optics and for direct laser cooling of Al+ ion clocks.

A compact and high efficiency intracavity OPO based on periodically poled lithium niobate

We demonstrate a compact, high efficiency and widely tunable intracavity singly resonant optical parametric oscillator (IC-OPO) based on multichannel periodically poled lithium niobate (PPLN). The IC-OPO is composed of 808 nm pump laser diode (LD), Nd:YVO4 laser and linear OPO. The continuous-wave (CW) mid-infrared (MIR) output laser is tunable from 2.25 to 4.79 μm. The maximum output power exceeds 1.08 W at 3.189 μm at 9.1 W LD pump power and the conversion efficiency is 11.88%. We also build up a prototype with volume of 145 × 85 × 42.5 mm3 and its total weight is less than 2 kg. The measured power stability is 1.3% Root Meat Square (RMS) for a 3 h duration under simulated high temperature conditions of 40 °C. RMS is 2.6% for a 4 h duration when simulated temperature is − 40 °C.

Suppression of relaxation-oscillations in intra-cavity optical parametric oscillators by two-photon absorption.

The applications of continuous-wave (cw), intra-cavity optical parametric oscillators (ICOPO) in molecular sensing and spectroscopy have been hampered by their relaxation-oscillation and power-stability problems. To solve these problems, we propose a two-photon-absorption (TPA) mechanism into ICOPOs. In a proof-of-principle experiment, we inserted a CdTe plate into an ICOPO as a TPA medium and demonstrated efficient suppression of relaxation-oscillations, obtaining an intensity-noise reduction of over 70 dB at the relaxation-oscillation frequency. To the best of our knowledge, this is the first demonstration of relaxation-oscillation suppression in ICOPOs based on TPA.