Abstract

We propose a new method for dividing an optical frequency into two tunable subharmonics using an optical parametric oscillator (CPO). With high efficiency, this scheme converts an input pump of frequency f_p into two intense subharmonic outputs whose frequencies f₁ and f₂ are tunable and equal to approximately half of the input frequency. By energy conservation, the output sum frequency f₁ + f₂ exactly equals the input frequency f_p. The tunable subharmonic frequencies can be precisely determined and controlled by measuring their difference frequency f₁ − f₂ and phase locking it to a microwave or millimeter wave frequency source, and they serve as useful frequency markers. The frequency stability of the OPO outputs is limited by the input pump linewidth, making it possible to transfer, without degradation, the frequency resolution of an optical frequency standard to its subharmonics. Several of the proposed frequency dividers, with their tunable outputs and narrow linewidths, can be operated in series or in parallel for the purpose of measuring, comparing, and synthesizing frequencies, from optical to microwave.

© 1989 Optical Society of America