Mode Selection And Phase-locked Efficiency Of Output Beam From Diode Laser Array Using External Cavity

The compact construction of high-power diode laser arrays, characterized by higher overall efficiency with a longer operating lifetime than any other laser type, is extremely attractive for applications such as material processing and solid-state laser pumping. It also faces a number of challenges in terms of beam quality improvement and bandwidth reduction. In this work, we present the way to improve the beam quality of diode laser arrays.In-phase mode selection with the amplitude compensator at a high current was analyzed theoretically. Phase locking of a diode laser array by an external cavity consisting of a mode selecting mirror or a phase grid was studied theoretically, on the basis of Fresnel diffraction and coupled mode theory. Variation of coupling mode efficiency versus phase of the feedback light was analyzed when a cylindrical lens was inserted in a Talbot cavity. The wavelength selection and stabilization of a volume Bragg grid was studied. The optimization of the cylindrical lens and the blaze grid was abtained, in order to improve the efficiency of wavelength beam combining. The self-phase locking of a single emitter was achieved experimentally and demonstrated availability of phase locking. A single lobe indicating in-phase mode with a power of 0.83 W was observed by tilting the external cavity. The width of the spectrum was reduced from 1.7 to 0.14 nm. A single lobe with a power about 1 W and a width of spectrum of 0.16nm were observed with an amplitude compensator. By adopting a volume Bragg grid, a stable spectrum with a central wavelength of 807.4 nm and a width of 0.4 nm were obtained that didn't shift with the temperature of the heat sink and the current. With wavelength beam combining technology, a round spot of output beam with a power of 2.39 W with a far field divergence of 1.2mrad was achieved.