An optically pumped caesium-beam frequency standard (known as the KRISS-1) has been constructed at the Korea Research Institute of Standards and Science (KRISS) and the first measurements of long-term frequency stability have been made. Two methods were used to make the frequency standard immune to variations in the environmental temperature: an σ π -polarized laser was used as a pumping source, and the difference between two sequential error signals was used as a feedback signal in the digital servo loop. A frequency stability of at s for a temperature variation of was achieved with the KRISS-1.

Photoacoustic detection of optical absorption in bulk solids is investigated with sample-transducer configuration using 5-nsec tunable dye laser pulses. The technique is shown to be sensitive for the measurements of nonlinear as well as linear absorption. The analysis of the resonant character of the piezoelectric transducer and the photoacoustic response of solids is also presented.