Abstract

A nonresonant optical parametric oscillator (NRO) is an optical parametric oscillator (OPO) in which each interacting frequency makes a single round trip in the cavity. A linear two-mirror NRO is illustrated in Fig. 1. A typical narrow-line operation consists of a high-energy pump and low-energy signal injected through mirror 1, which is transmissive at these wavelengths; the desired idler wave would be output through mirror 2. The ideal nonresonant OPO does not have any cold-cavity resonance, as the name implies. This lead to suggestions in early published articles¹ that the NRO exhibited continuously tunable narrow-line operation when seeded because of this lack of resonances. However, the addition of a gain material in the cavity couples the phases of the three waves and establishes cavity resonances. The resonance behavior is more complicated than a simple singly resonant OPO, for example, as the circulating energy is transferred between the idler and signal waves on successive passes in the cavity. This transfer of energy retains phase information, and therefore maximum gain will occur when the cavity round-trip propagation distance is an integral multiple of the seed frequency.

© 1995 Optical Society of America