Optical design of the system
Interferometer coupled to a white cell
The Gasex system consist of an interferometer module including also the MCT detector and an IR light source and a Multi-reflection gas cell. The light is produced by a black body radiation module and modulated by a dual corner cube interferometer.The light is then coupled into the Gas cell (where the gas to be analysed is injected) where it is relfected back and forth 32 times. Finally the light focused on the MCT detector.
How does the interferometer work?
Permanentely aligned interferometer
The heart of the FT-Rocket is dual corner-cube (retro-reflector) interferometer. The two corner-cubes are solidary to a common swinging arm, which rotates to create an optical path difference in the two arms of the interferometer.
This type of design is called a permanently aligned interferometer, as the alignment of the system is known to be the most robust against vibrations and temperature drifts. It never has to be realigned.
The swinging arm of the interferometer rotates on wear-free flexure system, making this mechanical system extremely robust and durable.
Solid-state reference laser
For measuring the movement of the mirrors, a solid-state reference laser is coupled into the interferometer. Compared to classic HeNe lasers, the solid-state lasers that we use are more compact and have a much longer life-time. They have a very low temperature-induced wavelegnth drift and, when kept at constant temperature with a Peltier element, their wavelength can be stabilized to a few PPM, thus providing a very accurate and reproducible wavelength scale. This is crucial for ensuring a day-to-day and unit-to-unit consistency..