Novel deep centers for high-performance optical materials

Abstract

Materials exhibiting strong optical emission also exhibit strong absorption at the same wavelengths because both emission and absorption are governed by the same optical dipole and density-of-states. Laser action requires a carrier injection large enough for emission to exceed absorption at laser wavelengths. Thus, strong self-absorption at luminescent wavelengths raises the operating current of LEDs, lasers, and optical amplifiers. Here we demonstrate that, contrary to conventional expectations, materials designed with novel deep centers achieve surprisingly large optical emission while, simultaneously, the inverse process of optical absorption remains very small. A striking consequence is that materials designed with our novel deep centers achieve transparency at a carrier injection which is four-orders-of-magnitude lower than in all technologically important semiconductors. Simultaneously, and surprisingly, our novel deep centers in GaAs achieve an optical gain, Einstein B coefficient, and radiative efficiency significantly larger than in direct-band-gap materials at 1.3–1.5 μm. We engineered this dramatic reduction of the injection to achieve transparency while retaining strong optical emission in our novel material by making use of a Franck–Condon shift of absorption away from luminescent wavelengths.