The Lowell Fabry-Perot Interferometer is a state-of-the-art, observatory-class, ground-based system available at a modest cost. Attributes include vertical mounting, few moving parts, simplified pointing system, frequency-stabilized laser, and flat field shuttering, resulting in highest precision of geophysical measurement. In addition, SSI offers installation services, which entail carrying the system through first-light into routine operations, with daily data collection and automatic analysis.


  • Custom design and fabrication – we fit the FPI to your space
  • Resonant cavity spacing from 3μm to 6cm
  • Maximum throughput for a given spectral resolution
  • Temperature stabilization and pressure control
  • Pressure pot with PID controlled pressure servo to maintain proper gas pressure in tuned etalon cavity
  • 150mm etalon with >80% reflectivity from 550nm – 900nm
  • Etalon cage with invar contacts to minimize thermal expansion
  • 0.4nm FWHM 3-cavity interference filters; CWL = 630nm and 557.7nm
  • Custom weatherproof NEMA-4 housing available

Lowell Doppler (Air-Gap) Interferometer
*Click for larger view