One diode-pumped solid-state laser was frequency-locked to another using current modulation of the pump laser. Our Nd:YAG microchip lasers operated at 1.32 μm, similar to the operation first reported by Zayhowski and Mooradian.1 A 1-mm-long piece of Nd:YAG was polished flat and parallel; dielectric mirrors were deposited directly on the polished faces. The pump mirror had 99.9% reflectivity at 1.3μm and high transmission at the pump wavelength; the output mirror had 98% reflectivity at the oscillating wavelength and reflected the pump. The lasers were pumped with butt-coupled GaAlAs diode lasers. The devices were packaged in thermoelectrically controlled TO-3 cans that incorporated optical isolators. A relative frequency jitter of ~250 kHz over a 15-s period (Fig. 1) and a relative frequency drift of several megahertz over 1 h were observed for the free-running devices.
© 1991 Optical Society of AmericaPDF Article