Novel deep centers for high-performance optical materials |
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Authors: | JL Pan JE McManis M Gupta MP Young JM Woodall |
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Institution: | (1) Yale University, P.O. Box 208284, New Haven, CT 06520-8284, USA |
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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.
PACS 71.55.Eq; 71.55.-i; 78.67.-n; 81.10.-h; 85.60.Jb |
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