Direct Imaging and wavefront control- Spectroscopy

Question 1

List components of slit spectrograph

Answer 1

1. Objective
2. Slit
3. Collimator
4. Disperser: A prism (Wedge shaped piece of glass composed of some material with a wavelength-dependent index of refraction) or grating (Planar or curved optical surface with a repeated series of finally space parallel grooves (reflection) or slits (transmission))
5. (Ian) Re-imaging lens
6. Camera

Question 2

List components of IFS

Answer 2

(I usually see these as IFUs) Typically fibers (tho other optics possible) are fed from the focal plane, often with microlenslets to focus light into each fiber. Fibers are then lined up, and fed to a dispersing element. Detector then gets a spectra in one axis, and fibers are indexed on the other axis. Focal plane can then be reconstructed by knowing where each fiber originated in the focal plane, and a 3D datacube is often produced, representing X-Y-wavelength

Question 3

How to increase spectral range?

Answer 3

1. Ordinary spectrograph that uses an order-sorting filter with large Δλ and m = 1
2. Echelle spectrograph that uses a cross-dispenser, a prism or grating to separate orders in the perpendicular direction, having small Δλand m = 10-100