F. G. Colville

Continuous-wave, singly resonant, intracavity parametric oscillator

Performance characteristics of a continuous-wave intracavity optical parametric oscillator are described by use of an experimental arrangement comprising a KTP singly resonant oscillator located within a Ti:sapphire laser cavity and analyzed by use of a steady-state model. Internal and external powers, circulating fields, tuning ranges, spectral bandwidths, and amplitude-stability levels are measured and discussed. The nonresonant idler tunes from 2.53 to 2.87 microm, delivers a maximum output power of approximately 0.4W and displays long-term amplitude-stable operation. The total downconverted power approaches the optimum power coupled out of the Ti:sapphire laser in the absence of frequency conversion.

Continuous‐wave, dual‐cavity, doubly resonant, optical parametric oscillator

We have demonstrated a continuous‐wave optical parametric oscillator that uses separate optical cavities to resonate independently the nondegenerate signal and idler frequencies. The three‐mirror cavity utilizes the type II phase‐matching geometry in lithium triborate, with the orthogonally polarized signal and idler fields separated by an intracavity, dichroic‐coated, Brewster‐angled beam splitter. This dual‐cavity oscillator can overcome mode and cluster hopping effects, which are characteristic of doubly resonant, continuous‐wave optical parametric oscillators. We measure a pump power threshold of ≊200 mW and smooth tuning over ≊0.4 GHz. The tuning range is limited by pump resonance effects within the idler cavity.

Continuous-wave parametric oscillation in lithium triborate

We demonstrate a continuous-wave optical parametric oscillator that uses lithium triborate as the nonlinear material in a temperature-tuned noncritical phase-matched type I geometry. Pumped at 514.5 nm, the triply resonant oscillator has a threshold of 50 mW. We obtain peak output powers of 90 mW corresponding to a 10% external conversion efficiency and measure a tuning range of 0.966 to 1.105 μm, limited by the bandwidth of the mirrors. Operating the optical parametric oscillator both at and away from degeneracy, we observe rapid changes in output power as a function of cavity length owing to competition between signal and idler mode pairs.

High-power, continuous-wave, singly resonant, intracavity optical parametric oscillator

A high-power continuous-wave optical parametric oscillator based on the nonlinear material KTiOAsO4 and pumped internal to a tunable Ti:sapphire laser is described. The use of the intracavity pumping approach has enabled operation of a singly resonant oscillator (SRO), resulting in the generation of as much as 1.46 W of infrared power in a 11.5-mm-long crystal. Amplitude-stable signal and idler outputs, each in excess of 500 mW, over the respective wavelength ranges of 1.11–1.20 and 2.44–2.86 μm have been extracted from the SRO. We demonstrate up to 90% down-conversion of the optimum Ti:sapphire output power to the SRO, confirming our recent theoretical predictions. The performance characteristics of the device demonstrate that practical, stable, and efficient operation of continuous-wave SROs at watt-level output power can be readily achieved in conventional birefringent materials by exploiting the intracavity pumping approach.

Doubly-resonant optical parametric oscillators: tuning behaviour and stability requirements

By way of a theoretical analysis and demonstration of experimental results, we contrast the influence of type-I and type-II phase-matching on the tuning behaviour and stability requirements of doubly-resonant optical parametric oscillators. Specifically, for near-degenerate operation, we illustrate the advantages of type-II, as opposed to type-I, phase-matching with regard to obtaining single signal and idler mode-pair output. For type-II phase-matching, single cluster and multiple cluster output is shown to depend on the level of pumping and the position of the clusters with respect to the optimum phase-matching condition. Within the experimental type-II phase-matched geometry, we maintain a single signal and idler mode-pair on resonance using a simple cavity length servo-control feedback-loop.

Continuous-Wave Parametric Oscillator Pumped In The Ultraviolet

We demonstrate what is to our knowledge the first continuous-wave optical parametric oscillator pumped by an ultraviolet source. An argon-ion laser operating at 364 nm is used to pump the nonlinear material lithium triborate, which generates tunable radiation in the blue-green and near-infrared spectral regions. With the cavity stabilized to stay on a single-frequency mode pair, we measure a threshold of 115 mW and a maximum output power of 103 mW. By use of a noncritical phase-matched, type II geometry, tuning ranges from 502 to 494 nm (signal) and 1.32 to 1.38 μm (idler) are observed.

Mode selection in doubly-resonant optical parametric oscillators

By using a computer model to calculate the threshold for each signal and idler mode-pair in doubly resonant optical parametric oscillators, we investigate the effects of the three principal tuning parameters (temperature, cavity length, and pump wavelength) on the mode selection. Through consideration of type I and type II noncritical phase-matched geometries for lithium triborate optical parametric oscillators, we illustrate that the tuning behavior depends on the difference between the refractive indexes experienced by the signal and idler fields. >

CONTINUOUS-WAVE LIB3O5 OPTICAL PARAMETRIC OSCILLATOR PUMPED BY A TUNABLE TI:SAPPHIRE LASER

We have demonstrated a continuous‐wave optical parametric oscillator that uses lithium triborate as the nonlinear material and a tunable Ti:sapphire laser as the pump source. By exploiting type I noncritical phase matching and a combination of temperature and pump frequency tuning, we have generated widely tunable radiation from 1.49 to 1.70 μm, limited by the bandwidth of the optical coatings. Total output powers of 30 mW and pump depletions of 40% have been obtained at two times the oscillation threshold of 360 mW. We discuss the application of this nonlinear frequency conversion process to several recently proposed experiments.

Doubly resonant optical parametric oscillator formed by index matching cavity mirrors directly onto an uncoated LiB(3)O(5) crystal.

We demonstrate the use of index-matching fluid to contact cavity mirrors directly onto an uncoated LiB(3)O(5) crystal to form a compact, stable resonator for use as an optical parametric oscillator. Specifically, we report on the characteristics of a continuous-wave, doubly resonant, type II phase-matched LiB(3)O(5) optical parametric oscillator formed in this way. Using a single-frequency argon-ion pumping laser operating at 514.5 nm, we measured a pump power threshold of approximately 100 mW and a total external conversion efficiency of approximately 15%. By altering the crystal temperature under noncritical phase matching, we measured coarse frequency tuning over approximately 36 THz, limited only by mirror coating bandwidths. We discuss also the transverse and longitudinal mode properties of the optical parametric oscillator outputs.

Continuous-wave intracavity optical parametric oscillators

Continuous-wave (cw) singly resonant intracavity optical parametric oscillators (OPOs) are attractive sources for generating highpower, narrow-linewidth, stable radiation in the near-infrared.’,* Recent progress in this new field is outlined herein, including a comparison between KTP and KTA, ktalons to stabilize the single-frequency output, and techniques for optimizing the output powers for the resonant or nonresonant OPO fields. The Tisapphire (TIS) lasers are longitudinally pumped by low-power argon-ion lasers and configured to accommodate two intracavity tightly focused spots (Fig. 1). They operate with high intracavity powers by minimizing resonator loss and tuning around the peak of the gain profile. One-way circulating powers of 50 W are available to surpass singly resonant OPO thresholds. Spatial hole burning, characteristic of the standing-wave laser, results in a pump bandwidth of 20 GHz. The OPO is formed by dual pumplsignal high-reflectors as mirrors M, and M,, and a dichroic-coated beamsplitter to discriminate the resonant pump and signal. An external mirror M, defines the OPO cavity. Mirrors M, and M, are antireflecting at the longwavelength idler. The idler output is optimized by maximizing the total downconverted power, achieved by carefully choosing the ratio of TIS to OPO thresholds.2 At 9.7 W argon-ion input, the downconverted OPO power is 1.5 W, -70% of the maximum power provided by the TIS in