Sum frequency generation of sodium resonance radiation

Abstract

We have generated pulsed, high power, sodium resonance radiation by sum frequency mixing the 1.06 microm and 1.32 microm outputs of two Nd:YAG lasers with an average power conversion efficiency of 30%. The wavelength of the sum radiation was tuned across the full Doppler width of the sodium-vapor D(2) absorption by tuning the wavelength of either Nd:YAG laser with intracavity etalons. The wavelength of the 1.32 microm Nd:YAG laser was also tuned by injection seeding with a GaInAsP/InP diode laser. We have used this sodium resonance radiation for the lidar observation of the earth's naturally occurring atomic-sodium layer at 90 km altitude.

Sodium temperature lidar based on injection seeded Nd:YAG pulse lasers using a sum-frequency generation technique

“…Fine control of the wavelengths is carried out by tuning the seeder crystal temperature. The seeder wavelength increases linearly with the crystal temperature (e.g., 6. …”

“…One of the best solutions for generating a 589 nm resonance light is a Nd:YAG laser. The sum frequency generation (SFG) of a 589 nm coherent light has been demonstrated with two Nd:YAG lasers operating at 1064 and 1319 nm [6,7]. This technique has already been applied to laser guide star adaptive optics [8], but most lasers are still continuous wave (cw) types and they are untested and require a radically different approach to obtaining altitude and spectral information.…”

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

“…Our approach uses sum-frequency generation of two mode-locked Nd:YAG lasers to achieve the desired Na wavelength, similar to previous designs [7,8,11]. Our major contribution is the application of injection mode-locking [14,15] as a robust method for simultaneous control of the absolute wavelength, bandwidth and timing for SFG.…”

“…1. 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].…”

“…Finally, engineering requirements of reliability, robustness and efficiency are important for applications of lasers to telescopes situated on remote mountain tops. Approaches to the laser include the first generation dye lasers [6], the more reliable sumfrequency generation (SFG) using solid state lasers [7,8] and recently fiber lasers [9,10], combined with various laser waveform techniques ranging from cw to mode-locking [11]. However, to the best of our knowledge no single approach has fully satisfied all the requirements simultaneously.…”