Integrated Fourier Transform Spectrometer

The NASA/NSF commissioned EPRV Working Grouprsquo;s final report calls for the development of spectrographs with spectral resolution exceeding 100,000 operating across the visible/NIR spectrum to support the characterization of earth analogs orbiting solar-type stars through radial velocity measurements.nbsp; While bulk optical instruments that require large volume/mass and complex environmental controls may work for the first phase that addresses the needs of ground-based telescopes, the development of an integrated instrument using photonic waveguide technology can adequately address the challenges posed by future mission concepts such as HabEx and LUVOIR where the demands of space deployment preclude bulky instruments.nbsp; The Phase II effort will produce a demonstration of a Fourier Transform Spectrometer that operates over 700-900nm with a resolution of 10,000.nbsp; nbsp;The envisioned integrated Fourier Transform Spectrometer uses a two stage system design to implement the network of switchable optical path delays with 14 bits of control.nbsp; One addresses the need to implement fine control of the optical path delay in the sub um to micrometersnbsp; range while the other addresses the coarse delays in the range of millimeters of optical path.nbsp;nbsp; The former is implemented with a novel cladding mode modulator that can provide a selection of two refractive indices for the propagating mode and the other uses an exchange/bypass (sometimes called cross/bar) switch to select one of two waveguides of differing lengths for the light to follow.nbsp; The system architecture should allow a very compact system to be realized, substantially reducing the volume and mass that needs to be temperature stabilized, a very important and practical system constraint.nbsp;nbsp;