Observation and analysis of mode competition in optic parametric oscillators

摘要

We report on 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 a monitor. We observed three types of operation mutually dependent on the seedlaser wavelengths: a free running OPO, one seedlaser seeding the OPO, and both seed-lasers seeding the OPO at the same time.