title: Production of a coherent pair of light beams with a microwave frequency difference from a single extended-cavity diode laser.
abstract: We produced a pair of coherent laser beams with a 3-GHz frequency difference by optically phase locking two modes from a single, multimode extended-cavity diode laser. This method is complementary to either a direct modulation or an optical phase locking of two independent lasers. A large differential frequency shift between the two modes of the laser allows efficient phase locking. We developed a simple theory to account for the large differential frequency shift. Allan deviation of the beat frequency when the two modes are phase-locked drops as an inverse of the measurement time and it reaches 10(-14) when the time is 1 h. Coherent population trapping spectroscopy of Rb atoms using the phase-locked beams resulted in a spectrum as narrow as that of the case using direct modulation by a stable frequency synthesizer.
authors.affiliation: Department of Physics, Korea University, Seoul 136-713, Korea.
authors.forename: Sin Hyuk
authors.initials: SH
authors.lastname: Yim
authors.forename: D
authors.initials: D
authors.lastname: Cho