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Narrow-linewidth Lasers

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Definition: single-frequency lasers with a narrow optical emission spectrum

German: Laser mit geringer Linienbreite, schmalbandige Laser

Categories: fluctuations and noise, lasers

How to cite the article; suggest additional literature

A number of laser applications (see below) require lasers with a very small optical linewidth, i.e., with a narrow optical spectrum. The term narrow-linewidth lasers usually applies to single-frequency lasers, i.e., lasers oscillating on a single resonator mode with low phase noise and thus with high spectral purity. Typically, such lasers also exhibit low intensity noise.

Types of Narrow-linewidth Lasers

The most important types of narrow-linewidth lasers are the following:

Essential Factors for a Narrow Laser Linewidth

For achieving a narrow emission bandwidth (linewidth) from a laser, several issues of laser design have to be observed:

Of course, the design optimization requires that the relative importance of different noise sources is known, because different measures can be required depending on which noise source is dominant. For example, measures which minimize the linewidth according to the Schawlow–Townes equation will not necessarily minimize the actual linewidth, if this is determined e.g. by mechanical noise.

Noise Characterization and Specification

Both the characterization and the specification of the noise of narrow-linewidth lasers are far from trivial issues. Various measurement techniques are discussed in the article on linewidth, and particularly for linewidth values of a few kilohertz or less such measurements are demanding. Furthermore, a linewidth value alone can not be considered a complete noise characterization; it is preferable to have a complete phase noise spectrum, apart from information on relative intensity noise. At least, the linewidth value should be specified together with a measurement time, and possibly with some information concerning frequency drifts for longer time intervals.

Of course, different applications have different requirements, and it should be checked in detail how tight noise specifications should really be demanded in any particular case.

Applications of Narrow-linewidth Lasers

Bibliography

[1]M. Fleming and A. Mooradian, “Spectral characteristics of external-cavity controlled semiconductor lasers”, IEEE J. Quantum Electron. 17 (1), 44 (1981)
[2]K. Kobayashi and I. Mito, “Single frequency and tunable laser diodes”, J. Lightwave Technol. 6 (11), 1623 (1988)
[3]S. P. Smith et al., “Narrow-linewidth stimulated Brillouin fiber laser and applications”, Opt. Lett. 16 (6), 393 (1991)
[4]N. Uehara and K. I. Ueda, “193-mHz beat linewidth of frequency-stabilized laser-diode-pumped Nd:YAG ring lasers”, Opt. Lett. 18 (7), 505 (1993)
[5]Y. Shevy and H. Deng, “Frequency-stable and ultranarrow-linewidth semiconductor laser locked directly to an atom-cesium transition”, Opt. Lett. 23 (6), 472 (1998)
[6]B. C. Young et al., “Visible lasers with subhertz linewidths”, Phys. Rev. Lett. 82 (19), 3799 (1999)
[7]R. M. Williams et al., “Kilohertz linewidth from frequency-stabilized mid-infrared quantum cascade lasers”, Opt. Lett. 24 (24), 1844 (1999)
[8]St. A. Webster et al., “Subhertz-linewidth Nd:YAG laser”, Opt. Lett. 29 (13), 1497 (2004)
[9]J. Geng et al., “Narrow linewidth fiber laser for 100-km optical frequency domain spectroscopy”, IEEE Photon. Technol. Lett. 17 (9), 1827 (2005)
[10]A. Polynkin et al., “Single-frequency fiber ring laser with 1 W output power at 1.5 μm”, Opt. Express 13 (8), 3179 (2005)
[11]H. Stoehr et al., “Diode laser with 1 Hz linewidth”, Opt. Lett. 31 (6), 736 (2006)
[12]J. Geng et al., “Dual-frequency Brillouin fiber laser for optical generation of tunable low-noise radio frequency/microwave frequency”, Opt. Lett. 33 (1), 16 (2008)
[13]S. Vogt et al., “Demonstration of a transportable 1 Hz-linewidth laser”, Appl. Phys. B 104 (4), 741 (2011)

(Suggest additional literature!)

See also: linewidth, single-frequency lasers, laser applications, laser noise, noise specifications, spectroscopy
and other articles in the categories fluctuations and noise, lasers

In the RP Photonics Buyer's Guide, 77 suppliers for narrow-linewidth lasers are listed.

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