Optical design of new generation compact, high resolution and high Doppler precision optical spectrograph

摘要

We report optical design of new generation compact, high resolution, high throughput and high Doppler precision opticalspectrograph. This spectrograph uses cross-dispersed echelle design with white pupils and also takes advantage of a fiberimage slicer to slice one 2 arcsec telescope input fiber image (80 micron at f/4 at the KPNO 2.1 meter telescope) intofour 1 arcsec images (40 micron). The small sliced images coupled with slow optics play a key role in achieving highspectral resolution within very compact instrument design to substantially reduce construction cost while increasing theinstrument stability for high Doppler precision over a long time. This optical spectrograph is called EXtremely highPrecision ExtrasolaR planet Tracker III (EXPERT-III). The coupling of the fiber sliced images with an R4 echelle with a98mm diameter pupil produces R=110,000 in the entire optical wavelength region. It also uses a two-prismcross-disperser to produce nearly homogeneous spectral order coverage while taking advantage of the anamorphicmagnification of the prisms to allow large wavelength coverage (380nm-900nm) in a single exposure with a 4kx4k CCDdetector. This very high resolution mode is designed to reach extremely high Doppler precision for radial velocitymeasurements of bright solar type stars. The spectrograph is also directly coupled with an 80 micron telescope fiber-fedimage to obtain high throughput with R=60,000 for stellar spectroscopy. Details about the optical design andperformance are reported.© (2012) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.