Critical study of pulsed parametric oscillators with intracavity optical parametric amplification (original) (raw)
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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
Journal of Nonlinear Optical Physics & Materials, 2017
We present modeling and design of continuous-wave (cw) singly-resonant optical parametric oscillator (SR-OPO) with an intracavity idler absorber to enhance the conversion efficiency for the signal by suppressing the back conversion of the signal and idler to the pump. Following plane wave analysis, we arrive at the optimum parameters of the OPO, with the intracavity idler absorber, to achieve high conversion efficiency for the signal. For a given pump intensity, we have analyzed the effect of position and number of absorbers required for optimum performance of the device. The model is also extended to the case in which the signal is absorbed, yielding higher conversion efficiency for the idler (in mid-IR region). The magnitude of absorption and the effect of intercrystal phase shift on the conversion efficiency are also discussed. We also present an analytical solution for twin-crystal SR-OPO with an absorber in between, taking into account the variation of signal amplitude inside t...
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.
Design, optimization, and characterization of a narrow-bandwidth optical parametric oscillator
Journal of the Optical Society of America B, 1999
The design, optimization, and performance of a narrow-bandwidth high-repetition-rate singly resonant picosecond optical parametric oscillator, based on a noncritical phase-matched lithium triborate crystal and synchronously pumped by the second harmonic of a mode-locked Nd:YLF laser, is described. The spectral bandwidth of the signal output is reduced with an intracavity birefringent filter to 0.06 nm. Furthermore, the filter allowed fast scanning of the output wavelength within the phase-matching bandwidth. A maximum average signal output of 1.6 W in pulses with a duration of 22 ps was obtained when the optical parametric oscillator was pumped four times above threshold with a 4-W pump source. With the present mirror set the signal and the idler wavelengths were tunable from, respectively, 740 to 930 nm and 1220 to 1830 nm. The total external power conversion efficiency was better than 55%.
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.
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.
Improving the efficiency of an optical parametric oscillator by tailoring the pump pulse shape
Optics express, 2010
The conversion efficiency of an optical parametric oscillator is reduced by energy consumption during build-up of signal and idler intensities and due to back-conversion effects. By tailoring the pump pulse temporal shape, we are able to improve the conversion efficiency by minimizing build-up time and back-conversion. Simulations predict a significant improvement in 1064 nm to 4000 nm idler conversion by using a double-rectangular temporal shape rather than using a simple Gaussian pulse. Experimental results qualitatively verify the effect resulting in a 20% improvement of a rectangular pulse over a Gaussian pulse.
Applied Physics B, 2004
An efficient diode-pumped passively Q-switched Nd:GdVO 4 /Cr 4+ :YAG laser was employed to generate a highrepetition-rate, high-peak-power eye-safe laser beam with an intracavity optical parametric oscillator (OPO) based on a KTP crystal. The conversion efficiency for the average power is 8.3% from pump diode input to OPO signal output and the slope efficiency is up to 10%. At an incident pump power of 14.5 W, the compact intracavity OPO cavity, operating at 46 kHz, produces average powers at 1571 nm up to 1.2 W with a pulse width as short as 700 ps.