First time! Significant progress has been made in low repetition rate fully polarization maintaining nine cavity fiber lasers

Recently, the research team of the Aerospace Laser Technology and System Department of the Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, reported for the first time a low repetition frequency full polarization maintaining 9-shaped cavity fiber laser at 915 nm. The relevant research results were published in Optics Express under the title "Low repetition rate 915 nm figure-9 ultrafast laser with all fiber structure".

Laser with a wavelength around 900 nm is highly favored in the field of optical measurement due to its high responsiveness on silicon-based detectors. The low repetition rate fiber laser in this band can effectively reduce distance ambiguity in Time of Flight (TOF), and has the characteristics of good beam quality, compact structure, and long-term stability, making it an ideal light source for space detection. However, due to the strong dispersion and nonlinear effects of single-mode fibers, it is difficult for lasers to achieve single pulse operation in long fiber cavities. Therefore, the repetition frequency of traditional mode-locked fiber lasers is usually limited to tens to hundreds of MHz.

In response to the above issues, researchers have proposed a low repetition rate fully polarized nine cavity fiber laser with a central wavelength of 915 nm. By designing and optimizing the laser structure, high-energy single pulse output was achieved at low repetition rates. The optimized seed was amplified in one stage to obtain a pulse output with a pulse width of 15.2 ps and a single pulse energy of 4.7 nJ at a repetition frequency of 3.1 MHz. The mode locking performance of the laser has been confirmed through long-term power and spectral stability tests. This compact and long-term reliable fiber laser is a promising light source for future space laser ranging.

This work was supported by the Youth Innovation Promotion Association of the Chinese Academy of Sciences, the National Natural Science Foundation of China, and the Shanghai Natural Science Foundation.

Figure 1. Experimental setup diagram of a 915 nm low repetition rate fully polarization maintaining nine cavity fiber laser

Figure 2. Long term stability testing of output power and spectrum, and output characteristics of pulses in frequency and time domains

Source: Yangtze River Delta Laser Alliance