Study on combined reflectors for improving efficiency of high power near-infrared emitters

Abstract

In this study, a combined reflector was suggested to improve the efficiency of high-power near-infrared (NIR) emitters. The combined reflector was fabricated by combining a distributed Bragg reflector (DBR) and an omnidirectional reflector (ODR). In the wafer bond process required for fabricating a high-power NIR emitter, the combined reflector was fabricated such that the developed DBR, which grew as the lowest layer of the epitaxial structure, bonded directly to the ODR deposited on the silicon wafer. The DBR in the combined reflector efficiently reflected photons emitted downward at a certain angle of 20° from the active region. A large number of photons, except at a certain angle by the DBR, are reflected by the other ODR. Therefore, the combined reflector might have favorable reflectivity properties produced by either DBRs or ODRs. As a result, photons emitted downward from the active region of the near-infrared emitter could be efficiently reflected upward and sideways by using a combined reflector of DBRs and ODR. From the results of the characteristics, the NIR emitter with the efficient combined reflector displays a 166% and 118% higher output power than that with either DBRs or ODR. Further, it was re-proved that there exist paramount characteristics of DBRs and ODR in a combined reflector through measurement of photometric and radial theta.