Electro Optical Infra-red Shutter.

Using electro-optical modulation to efficiently and quickly control light in thermal imaging devices instead of mechanical shutters.

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Electro-optical modulation is an attractive alternative as it simplifies operation, provides significantly higher modulation speed, shrinks dimensions, is resistant to mechanical shocks and is silent.

University of Birmingham researchers have proposed, research and developed solid-state modulators/shutters based on the electro-refractive effect to replace their mechanical counterparts. In the heart of our modulator is a technology based on the fusion of micro-and nano-patterned surfaces with the electro-refractive effect. This technology produces a semiconductor optical structure fully transparent for the middle and far infrared radiation in a passive state. Pumping optically the free charge carriers into the structure activates the modulator. At a specific charge density the structure will almost completely block the incoming radiation. Periodically driven excitation of the structure modulates a passing through signal synchronised with the external driver. The speed of the modulation can reach GHz regime with the modulation contrast above 90%. Moreover the modulation occurs over a narrow band around a specific resonance infrared frequency given by the properties of the structure.

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