The development prospects of Brillouin lasers

(1) Research on multi-wavelength Brillouin fiber laser based on photonic crystal fiber (PCF). The maturity of Dense Wavelength Division Multiplexing (DWDM) technology puts forward higher requirements on the performance of multi-wavelength fiber lasers. In order to further increase the communication capacity, the number of channels in the wavelength division multiplexing system increases, and the number of wavelengths output by the multi-wavelength fiber laser is increasing. The multi-wavelength Brillouin fiber lasers that have been reported so far all have a narrow gain spectrum, which limits the laser oscillation of more wavelengths. Photonic crystal fiber (PCF), also known as holey fiber (HF), micro-structured fiber (MF), is a new type of fiber composed of a single material with periodic micron-sized air holes in the cladding. In 2006, P. Dainese et al. studied SBS in photonic crystal fibers. They found that due to the special fiber structure and stress, this fiber can generate multiple acoustic modes, resulting in multiple modes of SBS with different Stokes shifts at the same time. Therefore, when designing multiple wavelengths Brillouin fiber lasers have considerable advantages. The special properties of photonic crystal fibers not only expand the frequency generation range of SBS, but also explore a series of special applications.　　 (2) Using the combination of SBS effect and mode-locking technology to study high-repetition rate multi-wavelength ultra-short optical pulse fiber lasers. Compared with other short pulse light sources, the high repetition rate multi-wavelength ultrashort optical pulse has the advantages of wider spectral width, better stability and broadband coherence, so it is widely used in optical communication, all-optical regeneration, and optical coherence layer. Analysis and optical frequency measurement. Passive mode locking is the use of nonlinear optical effects in optical fibers or other components to achieve mode locking, and is an effective method for generating ultra-short optical pulses. Using the gain bandwidth of the doped fiber, in theory, femtosecond optical pulses can be directly generated. The SBS-based Brillouin fiber laser is the key technology to achieve multi-wavelength laser output. Combining it with mode-locking technology to achieve high repetition rate multi-wavelength ultra-short optical pulse fiber laser is important for the research and development of Brillouin fiber lasers. One of the directions.　　(3) Develop high-power Brillouin single-frequency fiber lasers. In the high-power fiber laser resonator, due to the high intensity and coherence of the laser, the scattering of various spontaneous and random fluctuations of the incident light in the fiber can interfere with the subsequent incident light, and finally form a scattering with a light intensity equivalent to the incident light. Light, which produces stimulated scattering effect. The generation mechanism of stimulated Brillouin scattering and stimulated Rayleigh scattering in optical fiber is the same. The difference between the two is that stimulated Rayleigh scattering is a kind of elastic scattering, while stimulated Brillouin scattering is a kind of inelastic scattering. Therefore, the stimulated Brillouin scattering and the stimulated Rayleigh scattering are inseparable, and the stimulated Brillouin scattering and the stimulated Rayleigh scattering will occur simultaneously in the fiber resonator. Stimulated Rayleigh scattering provides additional feedback for the resonant cavity, which not only reduces the threshold of stimulated Brillouin scattering rapidly, but also narrows the linewidth of the output laser significantly. Using the SBS effect to achieve single-frequency laser output is a development direction of narrow-linewidth fiber lasers. (4) Use the SBS effect of various special fibers to produce high-stability Brillouin fiber lasers. The design of gain medium and laser cavity is still the key to making high-performance, low-cost Brillouin fiber lasers. Ordinary single-mode fiber (SMF) can be used as the Brillouin gain medium, but the nonlinear coefficient of ordinary fiber is small, resulting in a smaller Brillouin gain. In order to increase the laser output power, Brillouin fiber lasers generally use erbium-doped fiber amplifier (EDFA) as the gain medium, which combines the nonlinear Brillouin gain in the single-mode fiber and the linear gain in the EDFA to compensate for the loss of the resonator. , Constitutes a Brillouin erbium-doped fiber laser. In recent years, with the development of manufacturing technology, a variety of single-mode fibers of different materials have been produced. Due to the different material components, the Brillouin frequency shift, line width and gain coefficient of different fibers are quite different. Among them, the chalcogenide fiber, tellurite glass fiber and bismuth fiber have very high nonlinear coefficients, which can greatly reduce the SBS threshold, thereby greatly shortening the fiber length of the Brillouin fiber laser, and it only takes a few meters to achieve stability. The output of the Brillouin laser eliminates the environmental sensitivity caused by the excessively long EDF in the Brillouin fiber laser, making the output wavelength more stable and easy to tune. It is one of the effective methods to make a highly stable Brillouin fiber laser. one.