Intensity noise of an injection-locked Ti:sapphire laser: analysis of the phase-noise-to-amplitude-noise conversion

We describe the characterize a compact ring Ti:sapphire laser injection locked to an extended-cavity semiconductor source. The laser system has a good spectral purity and allows for fast scans, keeping the injectionlocking condition. We analyze experimentally the amplitude noise properties of the free-running and injected laser and show good agreement with a quantum-mechanical model. In spite of the sub-shot-noise properties of the semiconductor source, the injected laser exhibits strong excess amplitude fluctuations. We show that this effect is due to the conversion of the strong phase noise of the semiconductor laser into amplitude noise of the injected Ti:sapphire laser.