However, this spectroscopic technique presents several problems. Two different laser sources are required to generate the two frequency combs. Moreover, the two frequency combs require a high mutual coherence (Note 3) and frequency stability, making them difficult to control. Consequently, the overall measurement system becomes large, complex, and expensive, impeding its practical application (Fig. 3(a)).
Research methods and results
To overcome the problem, the research group re-examined the laser source configuration, focusing on the miniaturization and robustness of the frequency comb. Consequently, they succeeded in developing an all-fiber mechanism-sharing dual-comb fiber laser that is compact and does not require free-space optics using a saturable absorber micro-optic component and a polarization-maintaining fiber device (Fig. 4). The advantage of this scheme is that the two frequency combs share the same noise level. This reduces the influence of external noise, resulting in very high relative stability (Fig. 5). Furthermore, fast, high-resolution measurements of the absorption spectra of the gas molecules were performed using this new dual-comb fiber laser (Fig. 6).
Impact on society
The newly developed dual-comb fiber laser is compact and robust, owing to its all-fiber design. Thus, it is a promising light source for spectroscopic system for plants and other real-world applications. This technology has the potential to improve efficiency and energy savings in industrial fields of increasing importance in the future and is expected to contribute to a stable energy supply, economic benefits, and environmental protection.
These results were obtained through the following projects and research projects:
Adaptable and Seamless Technology Transfer Program through Target-Driven R and D (JPMJTM22B6), Research Foundation for Opto-Science and Technology, Hattori Hokokai Foundation, Mayekawa Houonkai Foundation, and Japan Society for the Promotion of Science (22H00303).
Optics Continuum Online Issue August 15 2023 issue
All-polarization-maintaining dual-comb fiber laser with mechanically shared cavity configuration and micro-optic component
Takumi Yumoto, Wataru Kokuyama, Shinichi Matsubara, Takeshi Yasui, and Yoshiaki Nakajima*（*responsible author）