Excess spontaneous emission in non-Hermitian optical systems. I. Laser amplifiers
Petermann first predicted in 1979 the existence of an excess-spontaneous-emission factor in gain-guided semiconductor lasers. We show that an excess spontaneous emission of this type, and also a correlation between the spontaneous emission into different cavity modes, will in fact be present in all open-sided laser resonators or optical lens guides. These properties arise from the non-self-adjoint or non-power-orthogonal nature of the optical resonator modes. The spontaneous-emission rate is only slightly enhanced in stable-resonator or index-guided structures, but can become very much larger than normal in gain-guided or geometrically unstable structures. Optical resonators or lens guides that have an excess noise emission necessarily also exhibit an ''excess initial-mode excitation factor'' for externally injected signals. As a result, the excess spontaneous emission can be balanced out and the usual quantum-noise limit recovered in laser amplifiers and in injection-seeded laser oscillators, but not in free-running laser oscillators.
- Research Organization:
- Max-Planck Institut fuer Quantenoptik, D-8046 Garching, West Germany
- OSTI ID:
- 6404218
- Journal Information:
- Phys. Rev. A; (United States), Vol. 39:3
- Country of Publication:
- United States
- Language:
- English
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