KTiOPO4 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.

Refined Sellmeier and thermo-optic dispersion formulas for BaGa4Se7

This paper reports on the refined Sellmeier and thermo-optic dispersion formulas for BaGa4Se7 that provide a good reproduction of the temperature-dependent phase-matching conditions for type-2 difference-frequency generation between the signal and idler outputs of a Nd:YAG laser-pumped KTiOPO4 optical parametric oscillator in the 8.457–9.092 µm and 12.075–14.201 µm spectral ranges at 20–150°C and recent experiments within these wavelength and temperature ranges performed by other authors.

Experimental and theoretical study on an intracavity KTiOPO4 optical parametric oscillator pumped by a dual loss modulated Q-switched and mode-locked laser

In this paper, a sub-nanosecond KTiOPO4 (KTP)-based intracavity optical parametric oscillator (IOPO) pumped by a dual-loss modulated Q-switched and mode-locked (QML) laser with an acousto-optic modulator (AOM) and a Cr4+:YAG saturable absorber (Cr4+:YAG-SA) has been demonstrated. By changing the initial transmission of Cr4+:YAG-SA and the transmission of the output coupler at the signal wavelength, the signal pulse width compression can be realized. At an incident pump power of 8.3W and an AOM repetition rate of 15kHz, a single signal pulse underneath Q-switched envelope with the shortest pulse width of 220ps was obtained. The experimental results reveal that this is a simple and effective way to obtain the sub-nanosecond OPO signal pulses. In addition, the related coupled rate equations have been set up and the simulation results agreed with the experimental results well.

High-peak-power sub-nanosecond intracavity KTiOPO4 optical parametric oscillator pumped by a dual-loss modulated laser with acousto-optic modulator and single-walled carbon nanotube

A high-peak-power low-repetition-rate sub-nanosecond intracavity KTiOPO4 (KTP) optical parametric oscillator (OPO) pumped by a doubly Q-switched and mode-locked (QML) YVO4/Nd:YVO4 laser with an acousto-optic modulator (AOM) and a single-walled carbon nanotube saturable absorber (SWCNT-SA) has been demonstrated. A maximum output power of 373 mW at a signal wavelength of 1570 nm was obtained. The smallest pulse width, highest pulse energy, and greatest peak power of mode-locking pulses were estimated to be 119 ps, 124 µJ, and 1.04 MW, respectively, under a maximum incident pump power of 8.3 W and an AOM repetition rate of 2 kHz. This OPO operation paves a simple way to produce eye-safe laser sources at 1570 nm with low repetition rates, small pulse widths, and high peak powers.

High-Repetition-Rate Terahertz Generation in QPM GaAs With a Compact Efficient 2-<inline-formula> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math> </inline-formula> KTP OPO

An efficient tunable high-repetition-rate KTiOPO4 (KTP) optical parametric oscillator (OPO) was deployed as a compact terahertz (THz) source for the first time. The KTP OPO was intracavity pumped by an acousto-optical Q-switched Nd:YVO4 laser and emitted two tunable wavelengths near degeneracy. The OPO tuning range extended continuously from 2.068 to 2.191 $\mu \text{m}$ with a maximum output power of 3.29 W at 24 kHz, corresponding to an optical–optical conversion efficiency of 20.69%, believed to be among the highest reported. A periodically inverted quasi-phase-matched GaAs crystal was used to generate the THz wave by the difference frequency generation (DFG) method based on a dual-wavelength laser. The maximum output THz power was $0.6~\mu \text{W}$ at 1.244 THz, and the DFG energy conversion efficiency was $4.32\times 10^{\mathrm {-7}}$ . This provides a potential practical palm-top tunable THz sources for portable applications.

Theoretical and experimental studies on coexistent OPO and SRS from a KTiOPO4 pumped by an AO Q-switched Nd:LGGG laser

Coexistent intracavity KTiOPO4 optical parametric oscillator (OPO) and stimulated Raman scattering (SRS) processes pumped by an acousto-optical Q-switched Nd:LuxGd3−xGa5O12 (Nd:LGGG) laser were presented for the first time. The Stokes radiations at 1093.2/1125.8 nm and a signal wave of 1570 nm were generated. At an incident pump power of 9.25 W and pulse repetition rate of 3 kHz, the maximum output powers of 375 mW at 1570 nm and 98 mW at 1093.2/1125.8 nm were obtained for the signal wave and Stokes radiations, respectively, corresponding to a total conversion efficiency of 5.1 %. A set of coupled rate equations for coexistent OPO and SRS processes was developed, and the numerical solutions agreed with the experiment results.

Widely tunable and monochromatic terahertz difference frequency generation with organic crystal 2-(3-(4-hydroxystyryl)-5,5-dime-thylcyclohex-2-enylidene) malononitrile

We report an experimental study on widely tunable terahertz (THz) wave difference frequency generation (DFG) with hydrogen-bonded crystals 2-(3-(4-hydroxystyryl)-5,5-dime-thylcyclohex-2-enylidene) malononitrile (OH1). The organic crystals were pumped by a ∼1.3 μm double-pass KTiOPO4 optical parametric oscillator. A tuning range of 0.02–20 THz was achieved. OH1 crystals offer a long effective interaction length (also high output) for the generation below 3 THz, owing to the low absorption and favorable phase-matching. The highest energy of 507 nJ/pulse was generated at 1.92 THz with a 1.89-mm-thick crystal. Comprehensive explanations were provided, on the basis of theoretical calculations. Cascading phenomenon during the DFG process was demonstrated. The photon conversion efficiency could reach 2.9%.

Dual-loss-modulated Q-switched mode-locked laser intracavity pumped temperature-tuned subnanosecond KTiOPO4 optical parametric oscillator.

Using an acousto-optic modulator (AOM) and Cr4+:YAG as the dual-loss modulation, an intracavity KTiOPO4 optical parametric oscillator (OPO) pumped by a simultaneously Q-switched and mode-locked (QML) YVO4/Nd:YVO4 laser was realized. The shortest mode-locking pulse duration of the signal wave at 1573 nm was directly measured as 450 ps at an AOM frequency of 2 kHz and a diode pump power of 10.5 W, corresponding to a peak power of 35.5 kW. The temperature tuning of the output signal wavelength was realized in the range from 1571.99 to 1572.61 nm with a blueshift ratio of 0.027 nm/°C. A set of coupled rate equations for the dual-loss-modulated QML laser pumping intracavity OPO was built for the first time to our knowledge. The numerical solutions were fitted with the experimental results.

Intracavity KTP optical parametric oscillator driven by a KLM Nd:GGG laser with a single AO modulator

Abstract An intracavity KTiOPO4 (KTP) optical parametric oscillator (OPO) pumped by a Kerr lens mode-locking (KLM) Nd:GGG laser near 1062 nm with a single AO modulator was realized for the first time. The mode-locking pulses of the signal wave were obtained with a short duration of subnanosecond and a repetition rate of several kilohertz (kHz). Under a diode pump power of 8.25 W, a maximum output power of 104 mW at signal wavelength near 1569 nm was obtained at a repetition rate of 2 kHz. The highest pulse energy and peak power were estimated to be 80 μJ and 102 kW at a repetition rate of 1 kHz, respectively. The shortest pulse duration was measured to be 749 ps. By considering the Gaussian spatial distribution of the photon density and the Kerr-lens effect in the gain medium, a set of the coupled rate equations for QML intracavity optical parametric oscillator are given and the numerical simulations are basically fitted with the experimental results.

Widely tunable and monochromatic terahertz difference frequency generation with organic crystal DSTMS

Widely tunable and monochromatic terahertz (THz) difference frequency generation with organic crystal DSTMS was investigated experimentally. A double-pass KTiOPO4 optical parametric oscillator, pumped by a frequency-doubled Nd:YAG laser, was employed as the source of dual wavelength. The THz tuning spectrum covered a range of 0.88−19.27 THz. The dependence of the THz output on the crystal thickness and pump wavelength was studied. The results were well explained based on theoretical calculations. With a pump energy of 2.47 mJ, the output energy reached 85.3 nJ/pulse at 3.80 THz, which corresponded to a peak power of 17.9 W and photon conversion efficiency of .

Intracavity optical parametric oscillator pumped by an actively Q-switched Nd:YAG laser

A non-critically phase-matched KTiOPO4 optical parametric oscillator (OPO) intracavity pumped by a laser diode end-pumped acousto-optically Q-switchedNd:YAG laser is experimentally demonstrated. The highest average power is obtained at the pulse repetition rate (PRR) of around 15 kHz, which is different from the widely reported Nd:YVO4 laser pumped OPO in which the highest average power is obtained at a very high PRR, e.g. 80 kHz. With an incident laser diode power of 6.93 W and a pulse repetition rate of 15 kHz, an average signal power of 0.72 W is obtained with a peak power of 7.7 kW and an optical-to-optical conversion efficiency of 10.4%.

Wavelength-agile mid-infrared (5-10 μm) generation using a galvano-controlled KTiOPO_4 optical parametric oscillator

A wavelength-agile mid-infrared (IR) ZnGeP2 (ZGP) optical parametric oscillator (OPO) using a galvano-controlled double-crystal KTiOPO4 (KTP) OPO was demonstrated. The mid-IR wavelength was tuned by varying the KTP OPO pump wavelength while the ZGP crystal angle remained fixed. Rapid tuning of the KTP OPO was achieved by changing the crystal angle by using the galvano scanner. Our mid-IR source can jump to a different wavelength without scanning through the intermediate wavelengths while also permitting continuous-wavelength scanning. The mid-IR source can be tuned from approximately 5to10 microm at a phase-matching angle of 51 degrees , while the pump wavelength is controlled in the 1.95-2.2 microm range.

Spectral and spatial limiting in an idler-resonant PPKTP optical parametric oscillator

The spectral and spatial properties of a non-collinear signal- and idler-resonant periodically poled KTiOPO4 optical parametric oscillator (OPO) have been investigated. The lower angular dispersion of the idler-resonant OPO allows for generation of up to two-times smaller spectral bandwidths at large non-collinear angles, and at the same time the beam quality improves considerably compared with the signal-resonant case. The overall efficiency reached 67% in both cases.

Tunable phase-matched optical parametric oscillators based on a cylindrical crystal

The use of cylindrical nonlinear crystals is a good way to extend the angular-tuning capability of optical parametric oscillators. We consider the example of a 1064-nm-pumped KTiOPO4 optical parametric oscillator phase matched in the x–z plane. A 31.5° angular tuning is demonstrated, limited by the spectral range of the mirrors. The measured slope efficiency and threshold energy are compared with the values published for a similar optical parametric oscillator that uses a parallelepipedic crystal. We study the beam quality of the emitted signal. The experiments with a plano–plano cavity point out the spatial-filtering effect due to the short focal length of the cylindrical crystal placed in the cavity. A simple model based on the coupling of the pump and the signal Gaussian beams in the cavity is developed. We then investigate the respective effects of the different experimental parameters on the output beam quality: radius of curvature of the mirrors, cavity length, crystal radius, pump-beam waist size, and spectral-tuning range of the signal beam. These calculations lead to the definition of the optimum configuration associated with a low M2 independent of the emitted wavelength. An experimental demonstration of that solution is given with excellent results: M2<1.5 is obtained, constant over 9° angular tuning.

Multiwatt high-repetition-rate 2-µm output from an intracavity KTiOPO_4 optical parametric oscillator

We have obtained 6.5 W of 2-mum output from a near-degenerate, type II KTiOPO(4) (KTP) optical parametric oscillator (OPO) pumped within the cavity of a Q-switched diode-pumped Nd:YAG laser that operates at 3 kHz. We adopted the simplest configuration with a compact diode-pumped Nd:YAG module pumping the doubly resonant KTP OPO in its randomly polarized resonator with an acousto-optic Q switch. Attempts to increase the 2-mum output power by pumping this intracavity KTP OPO with a polarized laser beam by use of thermal birefringence compensation configurations are discussed.

Single-mode KTiOPO_4 optical parametric oscillator

A tunable KTiOPO4 optical parametric oscillator (OPO) operating in a single longitudinal mode of its resonator is described. Single-mode operation has been achieved by use of an intracavity Fabry–Perot etalon in a short-length OPO resonator. The crystal is pumped by the second harmonic of an injection-seeded Nd:YAG laser. The tuning range observed with a crystal cut at 60° is 0.75–0.87 μm for the signal beam and 1.83–1.37 μm for the idler beam. The linewidth of the OPO is approximately 200 MHz (0.0066 cm−1), which is close to the Fourier-transform limit. The total output energy was measured to be as much as 0.6 mJ per pulse.