Experimental Observation of a Large Excess Quantum Noise Factor in the Linewidth of a Laser Oscillator Having Nonorthogonal Modes

Abstract

Several authors have predicted a substantial excess noise factor ${K}_{p}$ multiplying the quantum-limited Schawlow-Townes linewidth for laser oscillators having nonorthogonal spatial modes, such as unstable-resonator lasers. Experimental observations of this factor have to date, however, been limited in both number and detail. We report here a detailed experimental measurement of this factor in a diode-pumped hard-edged unstable-resonator Nd:YV${\mathrm{O}}_{4}$ laser. The measured excess noise factor ${K}_{p}\ensuremath{\simeq}330$ is in reasonable agreement with the theoretically predicted value.