In May 2018, LaserFocusWorld, an international laser pointer industry magazine, reported on the breakthrough in the research of photonic darkening and deep ultraviolet energy-transmission hollow fiber in Shanghai Institute of Optics and Fine Mechanics. The anti-resonant air-core quartz fiber developed by Shanghai Guangji Institute’s high-power laser unit technology laboratory achieves a low-loss transmission of 0.1dB/m in the 218nm band, which is nearly an order of magnitude lower than that of conventional fused silica fiber. In the process of transmitting a 266nm Q-switched laser with a pulse width of 17ns, a pulse energy of 0.47μJ, and a repetitive frequency of 30kHz, the hollow fiber has no photon darkening phenomenon within one hour, far exceeding the performance of the refractive index type quartz fiber. The research results were published in Opt. Express 26, 10879 (2018).
The traditional refractive index light guiding solid fiber represented by quartz fiber has achieved great success in the fields of fiber communication, fiber sensing and fiber laser pointer. Various optical fiber products have become indispensable in national defense, industry and basic research. Tool of. In recent years, with the development and introduction of new materials, the low-loss transmission window of refractive index-type optical fibers has been expanding, covering the visible to mid-infrared bands. However, at the ultraviolet and deep ultraviolet wavelengths, limited by the intrinsic absorption and multiphoton absorption of the glass material, the refractive index fiber loss is sharply increased; and the photon darkening effect caused by high energy photons fundamentally limits the conventional fiber. Application in the field of ultraviolet laser transmission. With the maturity of UV and deep ultraviolet solid-state laser technology, the demand for high-power laser transmission in the ultraviolet band is increasingly urgent for new low-loss, photon-darkening fibers.
The hollow core fiber, that is, the core region has no high refractive index material, and is mainly filled with gas or vacuum. Unlike the principle of total reflection of a refractive index type solid fiber, a hollow core fiber achieves low loss propagation of light in a low refractive index core region by introducing a complex cladding structure. Anti-resonant air-core fiber is a new type of air-core fiber that has emerged in recent years. It has the advantages of wide transmission window, low transmission loss and good single mode. Compared with the refractive index type fiber, the coverage of the optical fiber field and the fiber material of the hollow fiber can be reduced to 10-4-10-5, which makes the laser core resistant to laser damage threshold, anti-photon darkening and anti-irradiation performance. Sharply improved, while fiber material absorption, fiber nonlinearity and fiber dispersion are rapidly reduced, especially for high power laser pointer transmission and extreme wavelength laser low loss transmission.