Abstract

A novel scheme for generating a comb of precisely known optical frequency markers based on the use of optical parametric oscillators (OPOs) is proposed. The method provides identification and distribution of thousands of channel frequencies in densely packed wavelength or frequency division multiplexed systems, with sub-MHz accuracy over a large bandwidth of 10 THz or more. An OPO converts an input pump of frequency f_p into two intense, coherent subharmonic outputs whose frequencies f₁ and f₂ are tunable and sum to f_p. By measuring the beat frequency f₁–f₂ relative to a microwave frequency reference, the output frequencies are precisely determined, and the OPO functions as an optical frequency divider.¹ A single laser can be used to pump several OPOs whose outputs can then be phase locked to provide a comb of precisely known optical frequency markers. Assuming beat detection of 500 GHz, a set of ten OPOs would cover a ten-THz band. Absolute frequency reference can be obtained if one of the outputs or the pump is locked to an atomic line. This system’s precision is limited by the pump linewidth and the OPO mechanical stability. Recent experimental work on KTP OPO-dividers is discussed.

© 1991 Optical Society of America