Abstract

An optical parametric oscillator (OPO) performs the high-efficiency conversion of an input signal into two intense, coherent subharmonic outputs whose frequencies are tunable and whose linewidths are essentially limited by the input pump linewidth. By phase locking their difference frequency to a microwave, millimeter wave, or infrared reference source, the output frequencies are precisely determined, and the OPO functions as an optical frequency divider. The OPO dividers can be operated in series or in parallel to measure, compare, and synthesize frequencies from microwave to optical with high precision and resolution. The wide tunability of OPO's makes possible custom-tailored OPO configurations to suit a particular application. An example of this is the use of four phase-locked OPO dividers for the measurement of the hydrogen 1S-2S two-photon transition frequency (2λ = 0.486 µm) relative to the 3.39 µm CH₄-stabilized He:Ne laser. A special parallel OPO configuration permits the generation of a comb of precisely known frequency markers, which are particularly useful in areas of high-precision measurements and frequency standards. A line-narrowing effect for the generation of ultrastable radiation will be discussed.

© 1990 Optical Society of America