Power instability of singly resonant optical parametric oscillators: Theory and experiment (original) (raw)
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Continuous-wave, intracavity optical parametric oscillators: an analysis of power characteristics
Applied Physics B: Lasers and Optics, 1998
We describe the steady-state and transient power characteristics of continuous-wave intracavity singly resonant parametric oscillators (ICSROs). The operation characteristics of recently demonstrated ICSROs are reviewed. We derive a rate-equation model for the ICSRO which features a multi-frequency laser field. The steady-state behaviour of the device is detailed and methods to optimise the signal and idler outputs are presented. A Liapunov analysis tests the high-power stability of the system. We find that ICSROs do not suffer from the problems of instability which are characteristic of other intracavity frequency-mixing schemes and, as such, represent practical continuous-wave sources capable of high output powers and conversion efficiencies. Finally, we quantify the level of practical stability through an analysis of the novel transient behaviour of the ICSRO. We find that, to optimise the power stability, the signal cavity lifetime should be made as large as possible.
Applied Physics B, 2009
We demonstrate that for a given pump source, there is an optimum pump threshold to achieve the maximum single-frequency output power in singly resonant optical parametric oscillators. Therefore, cavity losses and parametric amplification have to be adjusted. In particular, continuous-wave output powers of 1.5 W were achieved with a 2.5 cm lithium niobate crystal in comparison with 0.5 W by a 5 cm long crystal within the same cavity design. This counter-intuitive result of weaker amplification leading to larger powers can be explained using a model from L.B. Kreuzer (Proc. Joint Conf. Lasers and Opt.-Elect., p. 52, 1969). Kreuzer also states that single-mode operation is possible only up to pump powers which are 4.6 times the threshold value. Additionally, implementing an outcoupling mirror to increase losses, single-frequency waves with powers of 3 W at 3.2 μm and 7 W at 1.5 μm could be generated simultaneously.
Intracavity continuous-wave singly resonant optical parametric oscillators
Journal of the Optical Society of America B, 1999
The operating characteristics and experimental performance of continuous-wave (cw) singly resonant optical parametric oscillators (ICSRO's) pumped internally to the cavity of the pump laser are described. We outline the operating principles, design criteria, and optimization procedure for maximum downconversion and power extraction and highlight the merits of the intracavity approach, including low input power requirement, potential for 100% downconversion efficiency, high-power operational stability, and power scalability. The predicted behavior and many of the attractive practical features of these devices are demonstrated in cw ICSRO's based on the birefringent nonlinear materials KTiOPO 4 and KTiOAsO 4 and on the quasi-phase-matched nonlinear materials periodically poled LiNbO 3 , RbTiOAsO 4 , and KTiOPO 4 , pumped internally to cw Ti:sapphireand diode-pumped solid-state lasers. Maximum extracted infrared powers of 1.46 W, downconversion efficiencies of as much as 90%, minimum input power thresholds of 310 mW, and wavelength tuning to 4 m in the mid-infrared are demonstrated.
Optics express, 2012
We report herein the enhancement in both power and efficiency performance of a continuous-wave intra-cavity singly resonant optical parametric oscillator (ICSRO) by introducing finite resonant wave output coupling. While coupling out the resonant wave to useful output, the output coupling increases the SRO threshold properly thus suppresses the back-conversion under high pump power. Therefore, the down-conversion efficiency is maintained under high pump without having to raise the threshold by defocusing. With a T = 9.6% signal wave output coupler used, the SRO threshold is 2.46 W and the down-conversion efficiency is 72.9% under the maximum pump power of 21.4 W. 1.43 W idler power at 3.66 μm and 5.03 W signal power at 1.5 μm are obtained, corresponding to a total extraction efficiency of 30.2%. The resonant wave out coupling significantly levels up the upper limit for the power range where the ICSRO exhibits high efficiency, without impeding its advantage of low threshold.
Applied Physics B, 2007
It is known that the idler conversion efficiency of optical parametric oscillators (OPOs) can be increased by adding a second nonlinear crystal in the cavity. This crystal is pumped by the signal and acts as an optical parametric amplifier (OPA) for the idler. However, this technique unavoidably increases the oscillation threshold because of additional losses and increased build-up time due to cavity lengthening. In this paper, we investigate both theoretically and experimentally the benefits and drawbacks of this so called OPO-OPA configuration versus the singly resonant OPO (SRO) configuration. Calculations are found to be in agreement with an experimental study of a SRO and an OPO-OPA operating near 3.4 µm both pumped by a 90-mJ 27-ns Nd:YAG laser. Our study reveals that the OPO-OPA needs to be driven at least two times above threshold to produce more idler energy than the SRO. In addition, near 3 µm the OPO-OPA is particularly efficient given that the difference frequency wave generated in the second crystal is also output coupled. PACS 42.65.Yj; 42.65.Sf
Continuous-wave, two-crystal, singly-resonant optical parametric oscillator: Theory and experiment
Optics Express, 2013
We present theoretical and experimental study of a continuouswave, two-crystal, singly-resonant optical parametric oscillator (T-SRO) comprising two identical 30-mm-long crystals of MgO:sPPLT in a fourmirror ring cavity and pumped with two separate pump beams in the green. The idler beam after each crystal is completely out-coupled, while the signal radiation is resonant inside the cavity. Solving the coupled amplitude equations under undepleted pump approximation, we calculate the maximum threshold reduction, parametric gain acceptance bandwidth and closest possible attainable wavelength separation in arbitrary dualwavelength generation and compare with the experimental results. Although the T-SRO has two identical crystals, the acceptance bandwidth of the device is equal to that of a single-crystal SRO. Due to the division of pump power in two crystals, the T-SRO can handle higher total pump power while lowering crystal damage risk and thermal effects. We also experimentally verify the high power performance of such scheme, providing a total output power of 6.5 W for 16.2 W of green power at 532 nm. We verified coherent energy coupling between the intra-cavity resonant signal waves resulting Raman spectral lines. Based on the T-SRO scheme, we also report a new technique to measure the temperature acceptance bandwidth of the single-pass parametric amplifier across the OPO tuning range.
Generation of 6.6-µm Optical Parametric Oscillation with Periodically Poled LiNbO_3
Applied Optics, 1999
Greater than 6-m-oscillation was demonstrated by means of optical parametric oscillation with periodically poled LiNbO 3 ͑PPLN͒. The interaction length and thickness were 40 mm and 500 m. The pump source used was a Q-switched Nd:YAG laser with a pulse duration of 120 ns and a repetition rate of 1 kHz. The tuning ranges of the idler waves were 6.57-6.56, 6.22-6.12, and 6.06 -5.94 m for PPLN wafers of 20-, 21.3-, and 22-m periods, respectively.
Critical study of pulsed parametric oscillators with intracavity optical parametric amplification
Conference on Lasers and Electro-Optics and 2006 Quantum Electronics and Laser Science Conference, CLEO/QELS 2006, 2006
It is known that the idler conversion efficiency of optical parametric oscillators (OPOs) can be increased by adding a second nonlinear crystal in the cavity. This crystal is pumped by the signal and acts as an optical parametric amplifier (OPA) for the idler. However, this technique unavoidably increases the oscillation threshold because of additional losses and increased build-up time due to cavity lengthening. In this paper, we investigate both theoretically and experimentally the benefits and drawbacks of this so called OPO-OPA configuration versus the singly resonant OPO (SRO) configuration. Calculations are found to be in agreement with an experimental study of a SRO and an OPO-OPA operating near 3.4 µm both pumped by a 90-mJ 27-ns Nd:YAG laser. Our study reveals that the OPO-OPA needs to be driven at least two times above threshold to produce more idler energy than the SRO. In addition, near 3 µm the OPO-OPA is particularly efficient given that the difference frequency wave generated in the second crystal is also output coupled. PACS 42.65.Yj; 42.65.Sf