Mesa Photonics’ compact, pre-aligned Herriott cell is easy-to-use and can be set up in just a few minutes. It gives you a 6-m-long optical path length in a structure that is only 30 cm long and weighs just 400 g including fiber collimator and detector. Simply attach the fiber from your laser to the collimator and a coaxial cable to the detector, and you are ready to run. No additional optics or alignment are needed. The cell is ideal for outdoor open path measurements including deployment on board UAV’s.
Herriott cells were invented at Bell Labs in the mid-1960’s for use as optical delay lines [Herriott and Schulte, Applied Optics 4 883 (1965)].
Their compact design and re-entrant optical trajectories are perfect for tunable diode laser absorption spectroscopy (TDLAS). The beam is refocused on each reflection to minimize divergence and allow large numbers of optical passes within a small structure. In Mesa Photonics design, the laser beam makes 34 passes between two mirrors. Compared to White cells, Herriott cells are less expensive, easier to align, and – most important – much less prone to unwanted optical interference fringes.
Mesa Photonics cell is intended for use at near-infrared wavelengths (~750 to 2600 nm). Longer wavelength options are available. The Herriott cell body is 3D printed nylon and then coated with epoxy to improve moisture resistance. Mirrors are held in commercial cage components secured by carbon-fiber rods to keep the structure rigid and light weight.
Our Herriott cells have been used successfully mounted on top of a battery-powered UAV as part of a NASA funded research project (Contract NNX15CA09C).