Two-level laser light statistics

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 rates. Lasers exhibit excess noise at low pumping levels.

Rate-equation approach to laser light statistics

“…Consider now the very special case where γ = 0 and N ӷ α, i.e., the laser is thresholdless and has very low loss. The normalized photocurrent spectral density reads (12) Ᏽ is thus unity at low and high pumping levels and goes to a minimum in between these bounds. The minimum value, Ᏽ min , and the corresponding pumping value are (13) It can be shown that this minimum is the absolute minimum of Ᏽ, irrespectively of the values of γ, N, and α [7].…”

“…The numerical method and the analytical method are found to agree for the range of parameters considered. More extensive treatments considering other laser schemes will appear elsewhere [7,12]. Section 3 describes the complete treatment of a two-mode laser derived from a classical four-level scheme.…”