Intracavity Optical Parametric Oscillator Research Articles

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.

Experimental optimization and dynamics solution of active-passive Q-switched intracavity optical parametric oscillator based on EO modulator and layered-WSe2 SA

By applying a prepared 3 nm-thick tungsten diselenide (WSe2) saturable absorber to an electro-optic (EO) modulated fundamental-light laser, an active and passive Q-switched intra-cavity optical parametric oscillator (IOPO) has been experimentally realized. Benefiting from the saturable absorption property of WSe2, the output characteristics of Q-switched IOPO with signal-light oscillating are obviously improved, including the 93.7%-increased peak power, 54.6%-compressed pulse width, 30.1%-improved conversion efficiency, 60.1%-improved pulse-train stability, 17.8%-improved beam quality, and 27.4%-shortened linewidth. With the values of absorption parameters calculated from the measured nonlinear-transmittance curve of WSe2, the rate equations for dual-loss Q-switched IOPO with WSe2 saturable absorber and electro-optic modulator are numerically solved. The theoretical values correspond to the experimental data well.

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%.

Tunable THz-radiation in a ZnGeP2 single crystal pumped by dual-wavelength degenerate optical parametric oscillator

A compact continuously tunable dual-wavelength source of radiation based on a diode pumped Nd:AG laser and an intracavity degenerate optical parametric oscillator (IDOPO) was demonstrated for the first time. The generation of two pulses of radiation with mutually orthogonal polarization and a wavelength difference from 0 to 500 nm is realized. The pulse energy reached ~1 mJ with a pulse duration of 10 ns at a repetition rate up to 1 kHz. Terahertz (THz) radiation was obtained using a difference frequency generation DFG in a single crystal ZnGeP2. The tuning range of the THz radiation in the wavelength range ~120–270 µm was realized. The maximum average power of THz radiation achieved in the experiment was ~3.3 nW at a wavelength of λ = 181 µm.

An active and passive dual-loss Q-switched intracavity OPO based on few-layer WS2 saturable absorber

A 2.5 nm-thickness tungsten disulfide (WS2) saturable absorber (SA) was successfully fabricated by the electron beam evaporation (EBE) combined with post vulcanization. By applying the prepared WS2 SA to an acousto-optic (AO) Q-switched fundamental laser, a dual-loss-modulated Q-switched intracavity optical parametric oscillator (IOPO) has been experimentally realized. Because of the participation of WS2 SA, the problem of output decline was alleviated when the pump power was between 8.6 W and 10.8 W. The pulse width could be maximally compressed by 73% in WS2 SA based active-passive Q-switched IOPO with 10 kHz pulse-repetition rate, and the shortest pulse width in experiment was 1.098 ns. Benefiting from the pulse compression, the maximum pulse peak power in dual-loss-modulated Q-switched IOPO was 427% higher than that in AO active Q-switched IOPO. The application of WS2 SA also contributed to the stability of signal pulse train whose root mean square error (RMS) was efficiently lowered from 0.01776 to 0.00954. The nonlinear conversion efficiency was improved by approximate 38.2% in the dual-loss-modulated Q-switched IOPO.

Experimental and dynamical study of a dual Q-switched intracavity OPO based on few-layer MoSe2 SA.

A 2.5nm-thickness molybdenum diselenide (MoSe2) saturable absorber (SA) is prepared by electron beam evaporation (EBE) method. Applying the prepared MoSe2 SA to an acousto-optic (AO) Q-switched fundamental laser, a dual-loss-modulated intra-cavity optical parametric oscillator (IOPO) has been experimentally realized. The signal-pulse train from this IOPO has 0.0053 standard deviation (SD) of pulse amplitude. When the MoSe2 SA is applied to IOPO, the signal pulse is compressed by maximum 68%, the peak power increases by 274%, and the nonlinear conversion increases by 12.6%. To solve the established rate equation of IOPO, the ground-state and excited-state absorption cross section of MoSe2 are rationally estimated to be 1.04×10-18cm-2 and 6.25×10-19cm-2 from the measured transmittance curve, and the excited-state lifetime is 275.6µs. The numerical solution of the equations fits the experimental data well.

A new approach to optimize the signal output power of the intracavity single resonator optical parametric oscillator

In this paper, the signal output power of an intracavity optical parametric oscillator is optimized so that the signal output power becomes maximum. The particle swarm optimization (PSO) algorithm is implemented to some practical setups and the results are compared with some experimental data in order to confirm our method. Finally, the PSO algorithm is performed on the rate equations to obtain and suggest the optimum values for gain medium length, nonlinear crystal length and output coupler reflectivity at signal wavelength simultaneously, in which the largest signal output power can be obtained. The numerical results show that at 25.9W for input power, the signal output power can be reached up to 4.55 W. In addition, the signal output power can be increased by 20%, by selecting appropriate values for the gain medium length, nonlinear crystal length and output coupler reflectivity at signal wavelength.

A High Conversion Efficiency Q-Switched Intracavity Nd:YVO4/KTA Optical Parametric Oscillator under Direct Diode Pumping at 880nm**Supported by the National Natural Science Foundation of China under Grant Nos 61505226 and 61535013, and the Fund of Chinese Academy of Sciences under Grant No 6141A01071701.

We report a high conversion efficiency Q-switched Nd:YVO4/KTiOAsO4 (KTA) intracavity optical parametric oscillator (IOPO) operating near 3.5 μm based on direct 880 nm laser diode (LD) pumping. A maximum average idler output power of 2.6 W with a pulse width of about 7.9 ns is achieved under an absorbed LD power of 45.4 W at a pulse repetition rate (PRR) of 10 kHz. The maximum optical-optical conversion efficiency from LD power to OPO mid-infrared (MIR) output of 6.74% is achieved. To our knowledge, this is the highest conversion efficiency for a KTA-IOPO by exploiting a Q-switched laser as the parent fundamental pump source. The beam quality factors M2 of the MIR beam at the full output power with a PRR of 10 kHz are within 2.12 in both the horizontal and vertical directions, indicating a near Gaussian mode.