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With high-temporal coherence and low-phase noise, narrowlinewidth lasers have important applications in spectroscopy, holography, and coherent detection. At present, ultra-narrowlinewidth lasing is generated by solid-state, optical fiber, and semiconductor lasers, which serve as a good light source for scientific research and industrial applications. In this article, we summarize the fundamental techniques and review recent developments in narrow-linewidth lasers. Moreover, typical applications of narrow-linewidth lasers are discussed to provide reliable and easy-to-use references for comparing the performance of narrow-linewidth lasers.

A narrow-linewidth laser with excellent temporal coherence is an important light source for microphysics, space detection, and high-precision measurement. An ultranarrow-linewidth output with a linewidth as narrow as subhertz has been generated with a theoretical coherence length over millions of kilometers. Traditional grating spectrum measurement technology has a wide wavelength scanning range and an extended dynamic range, but the spectral resolution can only reach the gigahertz level. The spectral resolution of a high-precision Fabry–Pérot interferometer can only reach the megahertz level. With the continuous improvement of laser coherence, the requirements for laser linewidth measurement technology are increasing, which also promotes the rapid development of narrow-linewidth lasers and their applications. In this article, narrow-linewidth measurement methods and their research progress are reviewed to provide a reference for researchers engaged in the development, measurement, and applications of narrow-linewidth lasers.

An all-solid-state pulse width adjustable Nd:YAG nanosecond laser at 1064 nm is demonstrated based on the bidirectional voltage supplied Q-switched technology. Continuously adjustable pulse-width from 4.6 to 32.3 ns is generated in a linear cavity, which is laser diode side-pumped at 808 nm at 100 Hz repetition rate. With 27 ns Q-switch duration, the shortest pulse width of 4.6 ns with single pulse energy of 0.77 mJ and a near-Gaussian beam quality (M 2 < 1.6) is obtained. Our results suggest an approach to generating pulsewidth adjustable nanosecond lasers for applications in LIDAR.

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