antireflection coating

[Ralph Florentin]

> 
> Dear all,
> 
> We are designing a multifiber spectrograph for the VLT (FUEGOS) and we are
> looking for spurious images and scattered light in the optical design. We
> do not yet know what CCD we will be used nor what antireflection coating
> will be used to enhance the quantum efficiency from 0.37 to 1 micron. We
> would be interested by informations (or references), concerning different
> kind of coatings, on their reflectivity in all the above spectrum and their
> scattering properties. The spectrograph camera is opened at a focal ratio
> f/1.5
> Thank you
> 
> Jean Pierre Picat
> Observatoire Midi Pyr=E9n=E9es
> 14 Avenue Edouard Belin
> 31400 Toulouse   France
> tel (33)61332929  Fax (33) 61536722
> 
> 
> 

Dear Jean Pierre,
	We are having our thinned CCDs (Loral 2kx2k, thinned by Mike Lesser)
coated with a two layer AR coating that cover the spectral band 300-1100 nm very
effectively. The coating is:
	HfO2 (50 nm thick) + MgF2 (100 nm thick)
These CCDs, after UV flooding yield extremely high QE througout the spectrum:
75 % at 300 nm, > 80 % at 400 - 800 nm, 40 % at 900 nm, 5 % at 1060 nm.
ESO uses similar coatings. By adjusting the relative thicknesses of the
AR layers you can optimize for max. QE at selected wavelength ranges.
Mike Lesser is the one to ask.
Kind regards
Ralph.

Ralph Florentin Nielsen
Copenhagen University Observatory
Brorfelde, Dk-4340 Toelloese,
Denmark.