Vii. Quantum Electronics

The primary objective in this program is the development of an extremely stable, low-jitter, single-frequency cw dye laser for use in a variety of applications such as optical communication and ultrahigh-resolution spectroscopy, and for studying fundamental interactions between radiation and matter. During the past year we have been concerned with the short-term stabilization of commercially available cw dye lasers. The main emphasis has been on improving performance without major redesign of the cavity. A Spectra-Physics single-frequency cw dye laser Model 580 was modified by extending the cavity approximately 10 cm and inserting an electro-optic phase modulator within this space. The phase modulator is an AD*P crystal, made by Interactive Radiation, Inc., and is free from resonances over a wide range of frequencies up to 400 MHz. A composite wideband feedback loop with 2 MHz bandwidth was used to lock the laser frequency to the side of a transmission resonance of an external Fabry-Perot cavity having a 1-MHz resonance width. In this way, the high-frequency response was provided by the intracavity phase modulator and a large dynamic range was provided by the PZT length transducer on which the output mirror was mounted. The use of this feedback loop reduced the rms jitter from 10 MHz to ~30 kHz. The reduction of the laser jitter was demonstrated by heterodyning two similar but independently stabilized dye lasers. The narrow laser linewidth was also demonstrated by the excitation of narrow hyperfine-structure resonances in a molecular beam of 12. The 800 kHz measured linewidth of an individual I2 line included a natural width of 400 kHz and residual Doppler broadening from molecular beam geometry.