Continuous-wave, singly-resonant, optical parametric oscillator based on periodically poled KTiOPO4

Single-frequency optical parametric oscillator intracavity-pumped by a visible VECSEL for low-noise down-conversion to 1.55 µm

We report, to the best of our knowledge, the first optical parametric oscillator (OPO) pumped by a visible AlGaInP-based vertical-external-cavity surface-emitting laser (VECSEL). Tunable emission over 1155-1300 nm in the signal and 1474-1718 nm in the idler are observed by temperature adjustment of a 40 mm-long 5%-MgO:PPLN crystal intracavity-pumped at 690 nm. When optimized for low oscillation threshold, and by implementing resonant idler output-coupling (TOC = 1.7%), extracted output powers of 26.2 mW (signal) and 5.6 mW (idler; one-way) are measured, corresponding to a total down-conversion efficiency and extraction efficiency of 70.2% and 43%, respectively. Further, a total down-conversion efficiency of 72.1% is achieved in the absence of idler output-coupling. Of particular interest for high-precision applications, including quantum optics experiments and squeezed light generation, high stability and single-frequency operation are also demonstrated. We measure RMS stabilities of 0.4%, 1.8% and 2.3% for the VECSEL fundamental, signal and idler, with (resolution-limited) frequency linewidths of 2.5 MHz (VECSEL) and 7.5 MHz (signal and idler).

Tunable, high-power, high-order optical vortex beam generation in the mid-infrared

We report the generation of tunable high-order optical vortices in the mid-infrared (mid-IR) using a picosecond optical parametric oscillator (OPO). The OPO is based on MgO:PPLN as the nonlinear gain medium and synchronously pumped by a mode-locked Yb-fiber laser at 1064 nm. Using a singly-resonant oscillator configuration for the OPO, we have achieved direct transfer of pump optical vortices to the non-resonant idler beam, with the resonant signal in the Gaussian cavity mode. We demonstrate the successful transfer of pump optical vortices of order, l_p= 1 to 5, to the idler beam of the same order across the mid-IR, with an output power of 630 mW to 130 mW across 2538 nm to 4035 nm for the highest idler vortex order, l_i= 5. To the best of our knowledge, this is the first report of an OPO pumped by a vortex beam of order as high as l_p= 5 and generating idler vortices of high order in the mid-IR.

Power Scaling of CW Crystalline OPOs and Raman Lasers

Optical parametric oscillators (OPOs) and Raman lasers are two nonlinear-based laser technologies that extend the spectral range of conventional inversion lasers. Power and brightness scaling of lasers are significant for many applications in industry, medicine, and defense. Considerable advances have been made to enhance the power and brightness of inversion lasers. However, research around the power scaling of nonlinear lasers is lacking. This paper reviews the development and progress of output power of continuous-wave (CW) crystalline OPOs and Raman lasers. We further evaluate the power scalability of these two laser technologies by analyzing the cavity architectures and gain materials used in these lasers. This paper also discusses why diamond Raman lasers (DRLs) show tremendous potential as a single laser source for generating exceedingly high output powers and high brightness.

Stable, continuous-wave, intracavity, optical parametric oscillator pumped by a semiconductor disk laser (VECSEL)

We report relaxation oscillation free, true continuous-wave operation of a singly-resonant, intracavity optical parametric oscillator (OPO) based upon periodically-poled, MgO-doped LiNbO3 and pumped internal to the cavity of a compact, optically-excited semiconductor disk laser (or VECSEL). The very short upper-laser-state lifetime of this laser gain medium, coupled with the enhancing effect of the high-finesse pump laser cavity in which the OPO is located, enables a low threshold, high efficiency intracavity device to be operated free of relaxation oscillations in continuous-wave mode. By optimizing for low-power operation, parametric threshold was achieved at a diode-laser power of only 1.4 W. At 8.5 W of diode-laser power, 205 mW of idler power was extracted, indicating a total down-converted power of 1.25 W, and hence a down-conversion efficiency of 83%.

Doppler-free spectroscopy using a continuous-wave optical frequency synthesizer

A continuous-wave (cw) optical frequency synthesizer is demonstrated by using a monolithic-type cw optical parametric oscillator (cw-OPO) and an optical frequency comb. The cw-OPO is phase locked to an optical frequency comb that is phase locked to an atomic clock. The output frequency of the cw-OPO is frequency shifted with an electro-optic modulator, which makes it possible to tune the frequency continuously over 10 GHz. Furthermore, Doppler-free spectroscopy is performed using the optical frequency synthesizer for a cesium D1 line at 895 nm. The observed linewidth of 5 MHz is the natural linewidth of cesium. The center frequency of the line is consistent with a previous report.