A synchronously pumped optical parametric oscillator (SPOPO) has been proved to be attractive sources for laser gyro applications. First of all, SPOPO offers a solution for the gain competition problem often encountered in solid-state lasers, since OPO has a lifetime equal to the pump pulse duration, and therefore no interactions between two counter-circulating pulses. Secondly, a synchronously pumped optical parametric oscillator (OPO) offers a unique means to control the pulse crossing point anywhere in a ring cavity. Another advantage over other systems is the wide tunability featured by OPO system, which is important for applications such as detecting ultra-low magnetic fields, where the laser radiation has to be tuned to a narrow atomic transition.

In order to reduce the beat note bandwidth to less than 100 Hz, the relative position of the two pump spots should be controlled to within 25 pm. The only practical solution is to place the OPO crystal inside the cavity of both OPO and pump laser, which ensures that CW and CCW pulses occupy exactly the same geometrical mode of the pump cavity. Our OPO cavity was configured both as a ring cavity and a linear cavity. The example of beatnote measurement of intracavity pumped OPO is shown below. Our experiment has demonstrated the exceptional sensitivity of this system as a differential interferometer.

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