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Encyclopedia of Laser Physics and Technology

Laser Noise

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Ask RP Photonics for advice on any aspect of laser noise, be it origins, simulation and modeling, optimization, measurement, or its effects. Note that Dr. Paschotta has a particularly strong expertise in this area. A Powerpoint presentation gives more details.

Definition: fluctuations of various parameters of laser light, such as the optical power and phase

Due to various influences of quantum noise and fluctuations of various technical origins, the output of a laser always contains some noise. There are different kinds of laser noise:

(This article is not considering acoustical noise emitted by laser devices.)

intensity noise spectrum

Figure 1: Intensity noise spectrum of a solid-state laser.

Origins of Laser Noise

The origins of laser noise can be divided into two groups:

Particularly for solid-state lasers, noise is often strong around the relaxation oscillation frequency and weak at frequencies well above this frequency (see Figure 1). Semiconductor lasers exhibit strongly damped relaxation oscillations, but with very high frequencies, which can be well above 1 GHz.

Impacts of Laser Noise

Laser noise is important for many laser applications. Some examples are:

Methods for Noise Reduction

Laser noise can be reduced in many ways:

A prerequisite for effective noise reduction is that the origin of the most disturbing noise is known, as well as the parameters determining the laser's sensitivity to thus noise influences. Depending on the case, it can be more effective to either reduce noise influences themselves or the laser's sensitivity.

Bibliography

[1]A. L. Schawlow and C. H. Townes, "Infrared and optical masers", Phys. Rev. 112 (6), 1940 (1958)
[2]C. C. Harb et al., "Intensity-noise dependence of Nd:YAG lasers on their diode-laser pump source", J. Opt. Soc. Am. B 14 (11), 2936 (1997)
[3]B. C. Buchler et al., "Feedback control of laser intensity noise", Phys. Rev. A 57 (2), 1286 (1998)
[4]T. C. Ralph et al., "Understanding and controlling laser intensity noise", Opt. Quantum Electron.. 31, 583 (1999)
[5]R. Paschotta, "Noise of mode-locked lasers. Part I: Numerical model", Appl. Phys. B 79, 153 (2004); R. Paschotta, "Noise of mode-locked lasers. Part II: Timing jitter and other fluctuations", Appl. Phys. B 79, 163 (2004)
[6]R. Paschotta et al., "Optical phase noise and carrier-envelope offset noise of mode-locked lasers", Appl. Phys. B 82 (2), 265 (2006)
[7]R. Paschotta, H. R. Telle, and U. Keller, "Noise of Solid State Lasers", chapter 12 in "Solid-State Lasers and Applications", editor: Alphan Sennaroglu, CRC Press, Taylor and Francis Group, LLC, pp. 473–510, 2007, ISBN 0-8493-3589-2

See also: noise specifications, quantum noise, shot noise, intensity noise, phase noise, linewidth, Schawlow-Townes linewidth, coherence, stabilization of lasers, mode hopping, Spotlight article 2006-08-01, Spotlight article 2006-08-20

Categories: fluctuations and noise, lasers

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