Infrared Wavelength Converter for Imaging Applications Based On Quantum Well Devices

摘要

A mid-infrared (MIR) and/or far-infrared (FIR) to near-infrared (NIR) converter (10) for imaging applications is disclosed. The converter (10) makes use of the properties of Optical Readout Quantum Well Infrared Photodetectors (ORQWIP) (20), an NIR source (16), and a conventional near infrared detector device (24). In combination, an MIR or FIR light source (12) to be imaged is focused by lenses or mirrors (17) into a beam combiner (18) along with an NIR probe wave generated by the NIR source (16). The lower conduction level electrons (50a-50g) of the OR-QWIP (20) absorb MIR/FIR photons (60) and are excited to an upper conduction level (48) or free electron band (166) of the OR-QWIP (20) corresponding to the MIR/FIR wavelength (60), while valence band electrons (54a-54g) of the ORQWIP (20) absorb NIR photons (52) and are excited to the freed-up lower conduction level (46) corresponding to the NIR wavelength (52). The resulting change in transmittance of NIR radiation due to absorption is recorded by conventional near infrared detection equipment such as a standard digital camera (24). If multiple layers (202a-202d) of AlGaAs are alternated with multiple layers (200a-200c) of GaAs of the same thickness and composition, then identical quantum wells (203, 223) will result, all of which absorb a single MIR/FIR wavelength and a single NIR wavelength. If multiple layers (246a-246d) of AIGaAs are alternated with multiple layers (244a-244c) of GaAs of different thicknesses and/or composition, then quantum wells (249, 259) having different energy level differences will result, the multiple quantum wells (249, 259) absorbing multiple MIR/FIR wavelengths (256a-256c, 264a-264c) and multiple NIR wavelengths (258a-258c, 270a, 270c).