Observation and analysis of mode competiotion in optic parametric oscillators

Abstract

We report of an experimental investigation and an analytical description of mode competition in an optical parametric ring oscillator (OPO). A ring cavity was spectrally controlled by injection seeding techniques. Upon injecting the signal wavelength at a power level of 2 mW the relevant idler wave was generated and monitored through a 2 cm long methane absorption cell. Mode competition was observable when two seedlasers operating at almost the same signal wavelengths were injected collinearly into the OPO. Both seedlasers were about 0.5 nm apart, and within the same acceptance bandwidth of the used nonlinear crystal (KTP). Simultaneous injection of the two seedlasers was performed by keeping the resonator dependent gain of one injected wavelength parameterized while the other was tuned. The influence of one seedlaser on the second was measured by using the generated idler waves, and the absorption cell as monitor. We observed three types of operation, mutually dependent on the seedlaser wavelengths, the free running OPO, one seedlaser seeds the OPO and both seedlasers seed the OPO at the same time.