Fundamental Mode-Locking of a Composite-Cavity Electro-optic Microchip Laser for Microwave Photonics

Compact solid-state lasers are an attractive potential source for high speed, low noise optical pulses suitable for microwave photonic systems such as optical A/D conversion or digital communications. These small devices can be mode-locked at the fundamental cavity resonance, thereby avoiding the complications arising from the presence of supermodes in harmonically mode-locked lasers. An Nd: YVO4/MgO:LiNbO3microchip laser was mode-locked at a fundamental frequency of 20 GHz. When locked to a synthesizer, the phase noise was source-limited to -72 dBc/Hz at 1 kHz offset. A coupled optoelectronic oscillator structure was then used to mode-lock the device without a microwave source, yielding a further reduced phase noise of -95 dBc/Hz at 1 kHz offset.