Relative frequency stability of stable He-Ne gas laser structures

Extreme care has been used to build stable He-Ne gas lasers of an integral design that includes the mirrors and the gas discharge tube in a single structure. Cornings ULE and 99JJW ultra low thermal expansion materials are used for the main components and ultra high vacuum type materials are used throughout. Beat-frequency measurements between two lasers were performed under pressure- and temperature-controlled conditions yielding a beat-frequency spectral width of the order of kHz over a measuring interval of 30 seconds. This result was achieved under ordinary laboratory conditions without any elaborate sound and vibration isolation.