Powerful Optically Pumped Far-Infrared Laser with Stable Output Power

Abstract

This paper describes the characteristics of the output stability of a powerful optically pumped far-infrared laser and the related physical phenomena used to measure and to improve the stability characteristics. First, we mention that the frequency stability of the CO 2 pump laser, measured with Doppler-free and pressure-broadened Stark Lamb dip signals, is about 250 kHz drift per hour in the free-running mode and about 150 kHz p-p in the actively stabilized mode. Next, we show that optical resonant feedback disturbed the output stability of our far-infrared laser. Then, we show that the output stability, resonant feedback, and temperature stability are closely related and that stable output can be obtained by controlling the temperature by using high-power chillers and a long idling time. Offset-hole input couplers also reduce the feedback. As a result, FIR output is stabilized to within a few percent.