Mid-infrared optical upconversion by integrating an InAsSb photodetector with a GaAs light emitting diode

Abstract

We report the fabrication and experimental results of a midinfrared optical up-converter that was fabricated using wafer fusion technology. Midinfrared optical upconversion from 4.0 to 0.84 µm was demonstrated at temperatures up to 200 K. Introduction:Thermal imaging in the range of 3 to 5 µm wavelength has became increasingly important due to the large number of applications for military and civilian purposes [1] such as military and police target detection and acquisition, predictive maintenance (early failure warning) on mechanical and electrical equipment, and pollution effluent detection. The standard procedure for fabricating InSb-based focal plane arrays for thermal imaging is based on indium bump technology. However this "one-piece-at-a time" process limits the yield and scalability of this technique. An alternative method to implement a thermal imaging camera is to integrate monolithically a photodetector and a light emitting diode (LED) to form an optical upconverter [2]. By using such a mid-infared (MIR) to near-infrared (NIR) optical upconverter, in combination with a commerciallyavailable Si CCDs camera, MIR detection and large-area MIR imaging functionality can be achieved. In a previous study some of the present authors have successfully demonstrated upconversion operation in the range of 3-5 µm based on InSb photodiode and GaAs/AlGaAs LED [3], but the device works only at cryogenic temperatures, which requires expensive, bulky, power-hungry and time-consuming cooler to operate. These factors limit the applications of the InSb-based upconverters. The addition of As to the InSb compound material, yielding InAsSb ternary, slightly increases the band gap and consequently decreases the maximum detectable wavelength to below 5 µm. Nevertheless, the detector maintains the same excellent detectivity of an InSb infrared photodetector at much higher temperatures [4]- [5], which are attainable through a thermal-electrical cooler. This enhancement will have profound impacts on the thermal imaging devices in the 3-5 µm range for high performance, easy implementation and low cost thermal imaging camera. In this work, we proposed and demonstrated a wafer-fused MIR optical upconverter that consists of an InAsSb photodiode and a GaAs LED. The external upconversion efficiency was measured to be 0.06 W/W at 200 K.