Jacques Arnaud, Laurent Chusseau, Fabrice Philippe

Optics Communications, Elsevier, 2002, 213, pp.325

ABSTRACT

The statistics of the light emitted by two-level lasers is evaluated on the basis of generalized rate equations. According to that approach, all fluctuations are interpreted as being caused by the jumps that occur in active and detecting atoms. The intra-cavity Fano factor and the photo-current spectral density are obtained analytically for Poissonian and quiet pumps. The algebra is simple and the formulas hold for small as well as large pumping ates. Lasers exhibit excess noise at low pumping levels.

LIEN VERS  L’ARTICLE : TWO-LEVEL LASER LIGHT STATISTICS

Jacques Arnaud

Optical and Quantum Electronics, 34, 393-410, 2002

ABSTRACT

Lasers essentially consist of single-mode optical cavities containing two-level atoms with a supply of energy called the pump and a sink of energy, perhaps an optical detector. The latter converts the light energy into a sequence of electrical pulses corresponding to photo-detection events. It was predicted in 1984 on the basis of Quantum Optics and verified experimentally shortly thereafter that when the pump is non-fluctuating the emitted light does not fluctuate much. Precisely, this means that the variance of the number of photo-detection events observed over a sufficiently long period of time is much smaller than the average number of events.

Light having that property is said to be “sub-Poissonian”. The theory presented rests on the concept introduced by Einstein around 1905, asserting that matter may exchange energy with a wave at angular frequency ω only by multiples of ~ ω. The optical field energy may only vary by integral  multiples of ~ ωas a result of matter quantization and conservation of energy. A number of important results relating to isolated optical cavities containing two-level atoms are first established on the basis of the laws of Statistical Mechanics. Next, the laser system with a pump and an absorber of radiation is treated. The expression of the photo-current spectral density found in that manner coincides with the Quantum Optics result.

The concepts employed in this paper are intuitive and the algebra is elementary. The paper supplements a previous tutorial paper (Arnaud, 1995) in establishing a connection between the theory of laser noise and Statistical Mechanics.

LIEN VERS  L’ARTICLE : RATE EQUATION THEORY OF SUB-POISSONIAN LASER LIGHT

J. Arnaud, L. Chusseau, F. Philippe

European Journal of Physics, 23, pp. 489-500, 2002

ABSTRACT

Carnot established in 1824 that the efficiency of cyclic engines operating between a hot bath at absolute temperature T hot and a bath at a lower temperature T cold cannot exceed 1−T cold/T hot. We show that linear oscillators alternately in contact with hot and cold baths obey this principle in the quantum as well as in the classical regime. The expression of the work performed is derived from a simple prescription. Reversible and non-reversible cycles are illustrated. The paper begins with historical considerations and is essentially self-contained.

LIEN VERS  L’ARTICLE : CARNOT CYCLE FOR AN OSCILLATOR