Abstract

Using an unstable laser cavity leads to enhancement of the quantum (Schawlow-Townes) linewidth [1]. The nonorthogonality of the transverse modes in such a cavity leads to a transverse excess noise factor K_⊥. The value of K_⊥ is expected to be extremely sensitive to the detailed transverse field distribution. Certain special configurations have been modeled theoretically, for example a hard-edged unstable confocal resonator [2] and a variablereflectivity-mirror unstable resonator [3]. A first experimental confirmation of the transverse excess noise was done by comparing two diode pumped Nd:YAG lasers: one with a stable and the other with an unstable cavity [4].

© 1996 IEEE