Optimised CCD AntiReflection Coating Graded thickness AR coating

Optimised CCD Anti-Reflection Coating Graded thickness AR coating (for fixed-format spectroscopy) Andrew Kelt, Andrew Harris and Paul Jorden E 2 V Technologies, 106, Waterhouse Lane, Chelmsford, Essex, CM 1 2 QU, United Kingdom Simon Tulloch Isaac Newton Group, Apartado De Correos 321, 38700 Santa Cruz de La Palma, Islas Canarias, SPAIN • Backthinned CCDs normally use a single wavelength antireflection coating to maximise QE • E 2 v designed custom evaporation technique to allow a graded AR coating • Test results – Optimised spectral response from 300 -1000 nm along 60 mm length of the sensor. Reduction of fringes when minimum reflection matches illuminated wavelength. • Results of spectral response, reflectivity, and fringe amplitudes are presented.

Optimised CCD Anti-Reflection Coating Sample CCD 44 -82 with graded coating This side of CCD is optimised for the blue This side of CCD is optimised for the red

Optimised CCD Anti-Reflection Coating

Optimised CCD Anti-Reflection Coating Optimised spectral response cf fixed wavelength AR coat [Curves are for deep depletion CCD] Please see poster for all the other data. Thanks! SUMMARY • Low reflectivity = High QE Optimises QE across full wavelength range. • Low reflectivity in the red = Low fringing Reduced fringes at red wavelengths • AR coat can be matched to spectrograph output. Ideal choice for Fixed Format Spectrographs.