Sources of phase noise in an injection-locked solid-state laser

We experimentally and theoretically investigate the sources of phase noise for an injection-locked, diode-laser-pumped Nd:YAG laser. We use a fully qu antum-mechanical model of the laser to describe the output phase noise of t he laser explicitly in terms of the input noise sources. We compare the fre e-running and injection-locked output noise with the quantum-noise limit (Q NL), and we find excellent quantitative agreement between the results of ou r experiments and theory. We show that the phase noise of the injection-lac ked laser can never be at the QNL for frequencies less than the injection-l ocking range. However, at frequencies well outside the linewidth of the sla ve laser, the phase noise can be at the QNL. We show that, although the tec hnical noise of the laser system can be substantially reduced by injection locking, the influence of cavity-length fluctuations on the phase noise of an injection-locked laser is finite and much greater than the QNL. These fl uctuations are the major impediment to achieving near-ideal performance for the injection-locked phase noise. (C) 2000 Optical Society of America [S07 40-3224(00)02001-4].