Letter abstract
Nature Photonics 2, 238 - 241 (2008)
Published online: 2 March 2008 | doi:10.1038/nphoton.2008.28
Subject Category: Nonlinear optics
Observation of two-photon emission from semiconductors
Alex Hayat1, Pavel Ginzburg1 & Meir Orenstein1
Abstract
Two-photon emission is a process in which electron transition between quantum levels occurs through the simultaneous emission of two photons. This phenomenon is important for astrophysics and atomic physics1, 2, and semiconductor two-photon emission was recently proposed as a compact source of entangled photons, essential for practical quantum information processing3, 4, 5, and three orders of magnitude more efficient6 than the existing down-conversion schemes. Two-photon absorption in semiconductors has been extensively investigated7, 8, 9, 10, 11; however, spontaneous semiconductor two-photon emission has not been observed, nor has it been fully analysed theoretically so far. We report the first experimental observations of two-photon emission from semiconductors and develop a corresponding theory. Spontaneous two-photon emission is demonstrated in optically pumped bulk GaAs and in electrically driven GaInP/AlGaInP quantum wells. Singly stimulated two-photon emission measurements demonstrate the theoretically predicted two-photon optical gain in semiconductors12, 13, 14, 15—a necessary ingredient for any realizations of future two-photon semiconductor lasers. A photon-coincidence experiment is presented to validate the simultaneity of the electrically driven GaInP/AlGaInP two-photon emission, limited only by the detector's temporal resolution.
- Department of Electrical Engineering, Technion, Haifa 32000, Israel
Correspondence to: Alex Hayat1 e-mail: ahayat@tx.technion.ac.il
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