We researched the external cavity spectral beam combination (SBC) of laser diode (LD) with pigtail output. Two laser diodes with pigtail output, center wavelength of 976nm, and about 45% of electric-to-optical (e-o) conversion efficiency was employed to achieve spectral beam combination. This method demonstrated the feasibility of closed loop SBC of LD with pigtail. The free running spectrum, single laser spectrum with locked wavelength, after combination spectrum were measured. It showed that the spectral width of free running and tunnel range of single laser locked is about 12nm, 6nm respectively. The feedback efficiency of external cavity is about 1.55% when the transmission of cavity output mirror is about 30%. The combination power of 1.63W was obtained, the o-o(optical-to-optical) transferable efficiency is about 25%. The deterioration factor beam quality is about 1.2×, meanwhile, the efficiency loss of SBC and the reason of deterioration of beam quality were analyzed due to the internal loss of external cavity, the transmission loss of grating. In this way, the space stitching, configuration of single chip can transfer to fiber arrangement and organization, due to flexibility and miniaturization of fiber, that will provide a novel thinking for SBC of LD in high power direct application.
Fiber coupled diode laser source is one of the important applications of diode laser. Aimed at a multi-mode fiber of 105μm core diameter and 0.15 numerical aperture, a fiber coupled diode laser system based on a novel reflected aspherical beam shaping component which combines the beam collimating and re-orienting is designed, and a single polarization model is used to validate the design. The simulation and experiment all show that: the system can couple 16 single emitter diode lasers into the multi-mode fiber of 105μm core diameter and 0.15 numerical aperture. In the principle validate experiment of 8 emitters, when the operation current is 10.5A, the output power can achieve 62W, the brightness is 10MW(cm2·sr), and the E-O efficiency is 52%, separately. In this design, the ratio of the system length and width can be adjusted by changing the offset of the reflected aspherical beam shaping component, so that the system can satisfy different structure demands. Moreover, the novel beam shaping component will effectively conduce to reducing the components amount in the system, which can improve the system integration and reliability. This fiber coupled diode laser can be applied in fiber pumping, material processing and many other areas after being engineered.
Fiber-coupled diode laser pumping source is one of the key components of high-power fiber laser system. Its performance is significant to the output power of fiber laser system. A 1.8kW fiber-coupled diode laser system is designed by using ZEMAX optical design software. The technologies of high-precision beam collimation, spatial multiplexing, polarization multiplexing, beam expanding, focusing and coupling are used to couple the beams of 42 diode laser bars into a fiber with a core diameter of 200μm and NA 0.22. Every beam emit from diode laser bar is single polarization, and its central wavelength is 976nm @ 55W. The desigh result showed the fiber output power could reach 1800W, and the fiber-coupling efficiency was 78%, the brightness was 37MW/(cm2·sr),corresponding. This fiber-coupled system can be used in fiber pumping, material process and many other areas.
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