MEMS-based Spectrographs Recent Advances on their Optical Design P. Spanò INAF Osservatorio Astronomico di Brera, ITALY STScI, Baltimore June 25, 2010

MEMS-based Spectrographs: Advances on their Optical Design INAF & O.A.Brera Since 2003 O.A.Brera is one of the 19 institutes currently part of the Instituto Nazionale di Astrofisica (INAF) 12 “Observatories” and 7 Institutes former belonging to the National Research Council (CNR) STScI Baltimore June 25, 2010 MEMS-based Spectrographs: Advances on their Optical Design

MEMS-based Spectrographs: Advances on their Optical Design Merate Observatory STScI Baltimore June 25, 2010 MEMS-based Spectrographs: Advances on their Optical Design

MEMS-based Spectrographs: Advances on their Optical Design From ground to SPACE We, GOLEM (Gruppo Ottiche e LEnti Merate) are a small team of astronomers and engineers located in Merate We works mainly for ground-based telescopes (e.g., the GRB shooter REM in La Silla, Chile) and focal plane instrumentation (e.g., X-shooter on ESO VLT in Paranal, Chile, again) for optical-to-NIR wavelengths More recently, we were involved in space-based projects, like SPACE (now EUCLID) STScI Baltimore June 25, 2010 MEMS-based Spectrographs: Advances on their Optical Design

MEMS-based Spectrographs: Advances on their Optical Design SPACE STScI Baltimore June 25, 2010 MEMS-based Spectrographs: Advances on their Optical Design

MEMS-based Spectrographs: Advances on their Optical Design ESA led a study to merge together the two Dark Energy missions, SPACE and DUNE into EUCLID Weak-lensing and BAOs as probes for DE 1.2m shared telescope VIS + NIR photometry NIR spectroscopy STScI Baltimore June 25, 2010 MEMS-based Spectrographs: Advances on their Optical Design

Digital Micromirror Devices STScI Baltimore June 25, 2010 MEMS-based Spectrographs: Advances on their Optical Design

MEMS-based Spectrographs: Advances on their Optical Design DMD principles - I ON: +12° OFF: -12° Incident ray DMD micromirror can tilt (along its diagonal) by +/- 12 deg (in the Cinema DLP) They correspond to two different states: On and Off A third state (power off) exists, with a 0° angle DMD micromirror DMD surface STScI Baltimore June 25, 2010 MEMS-based Spectrographs: Advances on their Optical Design

MEMS-based Spectrographs: Advances on their Optical Design DMD principles - II STScI Baltimore June 25, 2010 MEMS-based Spectrographs: Advances on their Optical Design

MEMS-based Spectrographs: Advances on their Optical Design DMD principles - III Tilt happens along the diagonal of the micromirror, so a 45 deg rotation of the device is required to keep chief rays within a plane perpendicular to the DMD surface STScI Baltimore June 25, 2010 MEMS-based Spectrographs: Advances on their Optical Design

DMD illumination geometry - I Rotation axis of the DMD mirror 45° Reflected ray DMD area DMD micromirror 0° 24° (angle w.r.t. DMD normal) DMD normal STScI Baltimore June 25, 2010 MEMS-based Spectrographs: Advances on their Optical Design

DMD illumination geometry - II 28º 16.73º 24º 16.73º 4º 17.9º 20º 17.9º 23º 24º 4º 23º Minimum and maximum Equal amplitude One perpendicular to field STScI Baltimore June 25, 2010 MEMS-based Spectrographs: Advances on their Optical Design

MEMS-based Spectrographs: Advances on their Optical Design RITMOS (Meyer et al. 2004) F/8 beam 0.8” micromirrors (@Mees 0.6m tel.) 11’x8’ FoV (@Mees 0.6m tel.) 0.39-0.49 um R=6000 STScI Baltimore June 25, 2010 MEMS-based Spectrographs: Advances on their Optical Design

MEMS-based Spectrographs: Advances on their Optical Design IRMOS (MacKenty et al. 2004) F/5.6 beam 17um micromirrors (=0.2”@KPNO 4m) 3’x2’ FoV (@KPNO 4m) 0.85-2.5 um (ZJHK) R=300-3000 STScI Baltimore June 25, 2010 MEMS-based Spectrographs: Advances on their Optical Design

SPACE DMD-baseline (Content et al., Durham Univ.) F/2.2 beam 14um micromirrors (=1” @ 1.2m) 49’x34’ FoV 0.9-1.7 um R=400 Very complex mirrors, large & heavy, complex mechanisms STScI Baltimore June 25, 2010 MEMS-based Spectrographs: Advances on their Optical Design

SPACE DMD altenative I (by Grange et al., Lab. Astroph. Marseille) F/2.7 beam 14um micromirrors (=0.9” @ 1.2m) 26’x14’ FoV 1.0-1.7 um R=400 Simpler, smaller, reduced performances STScI Baltimore June 25, 2010 MEMS-based Spectrographs: Advances on their Optical Design

SPACE DMD altenative II (by Spanò et al., INAF) F/4 beam 14um micromirrors (=0.6” @ 1.2m) 20’x11’ FoV 0.9-1.75 um R=400 Very compact, small field 50cm STScI Baltimore June 25, 2010 MEMS-based Spectrographs: Advances on their Optical Design

MEMS-based Spectrographs: Advances on their Optical Design TIR prisms STScI Baltimore June 25, 2010 MEMS-based Spectrographs: Advances on their Optical Design

MEMS-based Spectrographs: Advances on their Optical Design TIR on beamers STScI Baltimore June 25, 2010 MEMS-based Spectrographs: Advances on their Optical Design

MEMS-based Spectrographs: Advances on their Optical Design Beamer Requirements STScI Baltimore June 25, 2010 MEMS-based Spectrographs: Advances on their Optical Design

Example of TIR image quality (Bowron, et al. SPIE 5186,2003) STScI Baltimore June 25, 2010 MEMS-based Spectrographs: Advances on their Optical Design

DMD @ Galileo Telescope STScI Baltimore June 25, 2010 MEMS-based Spectrographs: Advances on their Optical Design

MEMS-based Spectrographs: Advances on their Optical Design A simplified approach Modular design, simple layout, cheap optics Low resolution “Large” field of view High efficiency “Off-the-shelf” optics STScI Baltimore June 25, 2010 MEMS-based Spectrographs: Advances on their Optical Design

The starting idea (Zamkotsian et al., ASP Conf. 207, 2000) F/7 beam Proposed for NIRMOS Two spherical mirrors and a convex spherical grating 1:1 Offner-like design STScI Baltimore June 25, 2010 MEMS-based Spectrographs: Advances on their Optical Design

MEMS-based Spectrographs: Advances on their Optical Design The design Two arms: Spectro & Imaging Wavelengths: 400-800 nm Spectral resolution: 250 Focal ratio: F/4 FoV: 4.5’x7’ Detectors: 2kx2k (spect.), 1kx1k (imaging) STScI Baltimore June 25, 2010 MEMS-based Spectrographs: Advances on their Optical Design

MEMS-based Spectrographs: Advances on their Optical Design STScI Baltimore June 25, 2010 MEMS-based Spectrographs: Advances on their Optical Design

MEMS-based Spectrographs: Advances on their Optical Design Optical details STScI Baltimore June 25, 2010 MEMS-based Spectrographs: Advances on their Optical Design

MEMS-based Spectrographs: Advances on their Optical Design Slits and spectra STScI Baltimore June 25, 2010 MEMS-based Spectrographs: Advances on their Optical Design

MEMS-based Spectrographs: Advances on their Optical Design Mechanical layout STScI Baltimore June 25, 2010 MEMS-based Spectrographs: Advances on their Optical Design

MEMS-based Spectrographs: Advances on their Optical Design Summary DMD spectrographs with enhanced FoV can be designed with faster beams TIR prisms can be very effective to keep size very small Simpler designs if Offner-type configurations are selected STScI Baltimore June 25, 2010 MEMS-based Spectrographs: Advances on their Optical Design