Characteristics of the optical parametric oscillator and its use for selective excitation

Techniques are presented for obtaining stable, single mode output from an optical parametric oscillator and for aligning such an oscillator with a molecular or atomic transition. A line width of 10(-3) cm(-1) or less was obtained with a long term frequency stability of 10(-3) cm(-1) or better. It has been demonstrated that an OPO can stay aligned for several hours with an absorption line of half-width 0.01 cm(-1).