Infrared Array page

Many of the instruments being built by the IoA Instrumentation Group are based on the infrared arrays produced by Rockwell International Science Centre. These are hybrid arrays using Mercury-Cadmium-Telluride and are sensitive to radiation in the wavelength range 1-2.5 um.

Devices:

HAWAII

Hawaii QE curve from Rockwell.

The Hawaii array is a 1024 x 1024 pixel array, currently the largest format near infrared array available. The CIRSI camera will use four of these arrays to produce a survey instrument with 4 million pixels, 64 times the survey efficeny of a NICMOS camera.

Hawaii technical information at Rockwell and a local copy

PICNIC

The Picnic is a 256 x 256 pixel array which replaces the older NICMOS device. The PICNIC array uses the same design of readout circuitry as the HAWAII array and so should achieve the same improved noise performance. Since the infrared detector material for both arrays is manufactured on the same wafer the quantum efficiency should be identical.

Two PICNIC arrays will be used in the COHSI spectrograph

Picnic technical information at Rockwell and a local copy

Technology:

These arrays are very different in technology and operation to the CCD detectors visible astronomers are familiar with. Each device is actually two systems joined together in a hybrid array. An infrared detector material ( HgCdTe ) converts the infrared photons into electrons, this charge is stored in a seprate readout circuit made from conventional CMOS Silicon devices. The two parts of the detector are bonded together with microscopic metalic Indium bonds which make the electrical connection to each pixel. For more details of these devices see chapter 2 of Martin Beckett's thesis

URL http://www.ast.cam.ac.uk/~optics - Revised: 25 Jan 97

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Comments to: mgb@ast.cam.ac.uk