Programmable Micro-Diffraction Gratings (PMDG) are a new type of micro-opto-electro-mechanical systems (MOEMS), opening new observational capabilities in future astronomical instrumentation. PMDG components are built with the mature micro-electronics technology, allowing a high number of moving elements as well as high performance uniformity over the whole device. Programmable gratings are based on a serial of parallel ribbons able to move out of the plane. Typical dimensions are 5μm-wide and 200μm-long ribbons. By using electrostatic force, ribbons are actuated and a grating could be formed. A few ribbons are efficient enough to diffract the light; then, locally, this grating acts as a ON-OFF switch. If the spectrum is focused on this type of device, by setting ON and OFF a selected number of "wavelengths", the spectral response of the spectrograph is programmable. The Darwin mission will search, detect and characterize exo-planets, using high-contrast nulling interferometry, coupled with spectroscopic observation. We propose a new observational concept for Darwin using a programmable spectrometer. By tailoring the spectral response, sensitivity as well as signal to noise ratio of the instrument will be increased. A demonstrator breadboard has been designed and built. This demonstrator permits the tailoring of spectral patterns by the PMDG component, and optical analysis of the obtained results both in spectral channel and imaging channel. Typical exo-planet spectra have been generated and set by the PMDG. Simulated signatures of exo-planets with life forms are clearly revealed and characterized. These new observational modes using PMDG devices would optimize and enhance exo-planet detection and characterization capabilities in Darwin-like missions.

Date Published: 28 July 2008
PDF: 12 pages
Proc. SPIE 7013, Optical and Infrared Interferometry, 70132P (28 July 2008); doi: 10.1117/12.790518

Published in SPIE Proceedings Vol. 7013:
Optical and Infrared Interferometry
Markus Schöller; William C. Danchi; Françoise Delplancke, Editor(s)