Infrared Detectors for Astronomical Applications

Infrared Detectors for Astronomical ApplicationsMark DrzymalaRafal PiersiakWilliam Herschel- Astronomer

Discovered Infrared Light in 1800Infrared Discovery

Rafal2Infrared and the Human Eye Human Eye can only detect 0.01% of light at 0.75 microns Infrared spectrum ranges from ~1 to ~1000 micronsNear InfraredMid InfraredFar Infrared

Infrared in Astronomy Visible spectrum light obstructed by dust and gasses Near infrared unobscured by dust and gasses, smaller stars visible Far infrared emitted by dustColder than coldest arctic night Most of the infrared spectrum absorbed by Earths atmosphere

How is Infrared Detected Photovoltaic EffectElectrons in valence band absorb photon energy and jump to conduction band Electrons flow from n-type to readout integrated circuit (ROIC) then back into p-type

Detector Materials Near Infrared (1-5um)InSb (Indium Antimonide) 1-6.7umHgCdTe (Mercury Cadmium Telluride) 0.8-25um Mid Infrared (5-28um)SiGa (Gallium-doped Silicon)SiAs (Arsenic-doped Silicon) Far Infrared (28 200um)Bolometers photons absorbed and thermalized, change in resistance measuredPrimary Characteristics Low readout noise 12e- Very high quantum efficiency 100% Extremely low dark current 0.01e-/sRead Out NoiseLow read out noise requires:Proper mating of the detector and the readout circuit.Minimal power consumption (few mWs)

The Design of a readout circuit is very involved! Ideal Detector Readout noise 12e- Realistic Detector Readout noise 15e- 30e-Quantum Efficiency Low readout noise 12e- Very high quantum efficiency 100% Extremely low dark current 0.01e-/sEfficiency of converting incident photons into electrons. Ideal Detector Quantum efficiency 100% Realistic Detector Quantum efficiency = 50% - 70%Dark CurrentThe relatively small electric current that flows through a photosensitive device when no photons are entering the device. Ideal Detector Dark current 0.01e-/s Realistic Detector Dark current 0.05e-/sSensor Implementation2048x2048 H2RGsensor array

Mosaic of 35 H2RG2048x2048 sensor arrays11Current Research Extrasolar Planets Finding Invisible Galaxies(Formed just after the Big Bang)

An infrared image of the HR 8799 system. The central blob is noise left over after light from the star has been largely removed. The three known planets can be seen: HR 8799d (bottom), HR 8799c (upper right), and HR 8799b (upper left).12Future Astronomical DetectorsInAs has dropped to 10s of nanoamps230 Kelvin = -45 deg F200 Kelvin = -100 deg FRedshift to 0.8 2.5 um range131.11mTypical IR LED 940 - 950nm

IR Experiment14Thank You