Demonstration and investigation of pulsed injected locked solid-state laser oscillators with high frequency stability due to gain gratings without any active stabilization

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The goal of this application is to investigate pulsed oscillators injection locked via gain gratings in loop resonators. The great advantage of such a scheme is its potential for high precision frequency stability without the need for any active stabilization circuit or actuator in contrast to state of the art frequency stabilization schemes. A stable monolithic non-planar ring oscillator will be used as seed laser that is injected into the high power loop. One of the loop resonator mirrors is a gain grating in the laser active material which is not fixed in position and thus can compensate for fluctuations of the resonator length. Single frequency operation can be realised very well in loop oscillators because of the coherence beam requirements to form the gain gratings and the Bragg selectivity of gain gratings themselves. A frequency locking of a loop oscillator emitting pulses with nanosecond duration, and energy in the mJ-range with identical frequencies or almost identical frequencies of the seed laser and loop oscillator with sub-MHz deviation was not demonstrated yet and will be in the focus of this application. The resonance behaviour of the loop will be investigated in detail. An injection locked pulsed solid state laser oscillator without active stabilization would be a major advance for many tasks in physics and technology especially for mobile lidar applications. In perspective such a scheme could be extended to continuous-wave-injection locking, or could be applied for coherent combination of laser sources.