20W of continuous-wave sodium D_2 resonance radiation from sum-frequency generation with injection-locked lasers

Abstract

A 20-W all-solid-state continuous-wave single-frequency source tuned to the sodium D2a line at 589.159 nm has been developed for adaptive optical systems. This source is based on sum-frequency mixing two injection-locked Nd:YAG lasers in lithium triborate in a doubly resonant external cavity. Injection locking the Nd:YAG lasers not only ensures single-frequency operation but also allows the use of a single rf local oscillator for Pound-Drever-Hall locking both the injection-slave and the sum-frequency cavities. We observe power-conversion efficiencies in excess of 55% and a linearly polarized diffraction-limited output tunable across the sodium D2 line (589.156 to 589.160 nm) with no change in output power and with high amplitude and pointing stability.

Yellow nanosecond sum-frequency generating optical parametric oscillator using periodically poled LiNbO3

“…In their approach 1.2 W of yellow light at 578 nm was generated at a repetition rate of 10 kHz. Another approach often used to reach the yellow spectral region is sum-frequency generation (SFG) of two neodymium lasers operating around 1064 nm and 1320 nm respectively [2][3][4]. Many Watts of yellow light have been generated in this way by using external cavity sum-frequency generation of two injection locked lasers [4].…”

Daylight operation of a sodium laser guide star for adaptive optics wavefront sensing

“…The laser generates ∼6.5 W of narrowband continuous-wave light in a beam that is circularly polarized to take advantage of optical pumping. 12 It is installed on an optical bench next to the UA's 1.5-m Kuiper telescope on Mount Bigelow in Arizona. The beam has a Gaussian profile and is launched through a 10-cm aperture that is separated from the Kuiper telescope's optical axis by ∼5 m. For the experiment described in this paper, the laser launch projector was pointed at zenith and the Kuiper telescope pointed slightly off zenith to place the sodium resonance beacon at about a 90-km range within its field of view.…”

Injection mode-locked guide star laser concept and design verification experiments

“…It uses two cw non planar ring oscillator (NPRO) lasers [17], each stabilized accurately to the wavelengths near 1064 nm and 1319 nm required to produce the Na wavelength by SFG [7]. For robust operation and control we propose using an active servo to accomplish this as shown, but in practice this may not be necessary due to the inherent stability of the NPROs [18]. From the output of each of these cw lasers, we slice a pulse of about 1 ns duration to inject into the slave power resonator for injection modelocking.…”