NOISE SOURCES DESCRIBING QUANTUM EFFECTS IN THE LASER OSCILLATOR.
MASSACHUSETTS INST OF TECH CAMBRIDGE RESEARCH LAB OF ELECTRONICS
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Quantum noise in the laser means those properties of the laser output that are caused by the quantum nature of the electromagnetic field and of the material systems and reservoirs with which it interacts. It is shown that a fully quantum-mechanical treatment of the laser can be formulated in a noise-source formalism, for which the noise sources are operators. A definition is given for the Gaussian character of operators in an appropriate ensemble, and it is shown that the noise sources for the laser are Gaussian. Special laser models are treated. The first model requires that the relevant relaxation time constants of the material be much smaller than those of the field the second model drops this restriction. The final operator equations are solved by means of a linearization approximation that is only justified for operation points sufficiently above threshold. The first model takes the quantum nature of the field above threshold or equivalently the commutator of certain noise-source operators consistently into account the second model neglects these quantum effects. The results are compared with the predictions of a semiclassical theory in which classical equations contain noise sources that correctly represent properties of the field below threshold. Author
- Lasers and Masers