5C1 - Intra-cavity perturbation of a gas laser by Faraday effects in glasses

The output intensity of a laser can be internally modulated by time-varying perturbation of the losses in the laser cavity. This technique greatly improves the efficiency of modulation over the external modulation methods, and is therefore important for various proposed applications of lasers. We have studied the intra-cavity loss perturbation in a He-Ne laser utilizing the diamagnetic Faraday effect in glasses. In comparison with electrooptic crystals, glasses introduce a much smaller amount of static optical loss to the cavity, resulting in a higher output from the laser. Experimental observations of the modulated laser output confirm the predictions of our theoretical analysis. Furthermore, this modulation technique enables us to measure Faraday rotation of the modulator material as small as 0.01 seconds of arc, which represents an enhancement of the measurement sensitivity by two orders of magnitude over the conventional technique.