Single-frequency narrow-linewidth optical fiber laser based on double optical fiber coupling ring and saturable absorber

Abstract

The invention discloses a single-frequency narrow-linewidth optical fiber laser based on a double optical fiber coupling ring and a saturable absorber, and belongs to the field of the optical fiber laser. A structure thereof comprises a pumping source (1), a wave-division multiplexer (2), a gain optical fiber (3), a double coupling optical fiber ring (4), a polarization beam splitter (5), a first2*2 optical coupler (6), a Bragg optical fiber grating (7), a non-pumped erbium-doped optical fiber (8), a first optical isolator (9), a second optical isolator (10), and a third optical isolator (11). The double coupling optical fiber ring and the non-pumped erbium-doped optical fiber are respectively used as a mode filter and a saturable absorber to commonly help the optical fiber laser to acquire the single longitudinal mode output. The self-writing optical fiber grating formed in thenon-pumped erbium-doped optical fiber has extremely narrow bandwidth, and has excellent mode filtering characteristic, so that the length of the double optical fiber coupling ring is unnecessary to set as extremely short, and the realization difficulty is greatly reduced. The high-performance single-frequency laser output can be acquired, and the single-frequency laser output can be applied to a high-precision time frequency transmission system and a microwave photonics as the laser source.

Description

technical field [0001] The invention relates to a single-frequency fiber laser, in particular to a single-frequency narrow-linewidth fiber laser based on a double-fiber coupling ring and a saturable absorber. Background technique [0002] Compared with other types of lasers, fiber lasers have significant advantages such as low laser threshold, good output beam quality, and high conversion efficiency. Moreover, due to the high "surface area / volume" ratio of the optical fiber and good heat dissipation effect, it can be designed as a high-reliability laser light source that is easy to system integration. With its remarkable laser characteristics such as high monochromaticity and high coherence, single-frequency fiber lasers have not only gradually become important laser light sources in the fields of coherent optical communication systems and laser ranging, but also in microwave photonics, fiber optic detectors and high-precision lasers. Emerging technologies such as spectrosc...

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Problems solved by technology

[0003] It is a direct and effective method to use a multi-resonator structure or a Mach-Zehnder interference structure in a fiber laser to obtain a single longitudinal mode output, but the resonator structure and the Mach-Zehnder interference structure are more complicated, and the structure needs to be set very accurately The length of the coupler or the length of the fiber, in many cases, the setting accuracy needs to reach the order of centimeters, which greatly increases the difficulty of fusion splicing

In addition, the complex resonator structure will bring greater loss, which will eventually affect the output performance of the laser

Using a piece of unpumped ytterbium-doped fiber or unpumped thulium-doped fiber as a saturable absorber in a fiber laser to complete mode selection, and using a narrow linewidth Bragg grating are also several effective methods to achieve single longitudinal mode output of the laser. However, the high price and the large connection loss in the cavity are obvious problems

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