Interferometry

Low noise lasers enable interferometry with unprecedented and otherwise unattainable precision. High precision interferometry now enables the study of previously unobserved phenomena such as gravitational waves. The direct detection of gravitational waves stands at the beginning of a whole new field of astronomy. Gravitational waves are emitted by very massive accelerated objects such as black holes, which are often not visible with conventional telescopes.

For this purpose, large scale Michelson interferometers housed within vacuum systems with an arm length of several kilometers are in operation or being built at several sites around the world. A passing gravitational wave will cause a very small arm length change in such an interferometer. Great care is exercised to suppress all other potential noise sources to below the strength of the signal that is to be detected. Such unwanted noise sources are seismic noise, thermal noise, electronic noise, as well as excess noise associated with the laser. Multiple stage monolithic suspensions of the interferometer optics and advanced interferometer designs with arm cavities and additional power and signal recycling mirrors are being used to address these noise sources. The seed laser of choice in these high precision interferometers is Coherent Mephisto because of its sub-kHz linewidth and very low-frequency noise.

In related experiments, fundamental quantum optics effects and the generation and application of squeezed light are studied. The observation of these effects is only possible when an ultra-stable low noise laser system is available. Although gravitational waves research represents the most demanding requirements, Coherent Mephisto can also be used in other applications, where precise interferometric methods are employed, including absolute frequency metrology, free-space optical communication schemes and others.

When a higher output power is needed, the Mephisto MOPA (up to 55 W) is available with the same stability parameters. Interferometry applications at different wavelength such as 1319 nm or 532 nm are also possible.

Many other experiments or measurement techniques use interferometry with much less stringent requirements than gravitational waves detection. For these experiments, single-frequency lasers like the Sapphire-SF family of Innova Ion lasers operated in single-frequency modality are a convenient match and offer many different wavelengths.