Study On The Low Divergence Broad-area Semiconductor Lasers Base On GaSb

The broad-area(BA) 2 μm GaSb based semiconductor lasers with low divergence were studied in this dissertation. In the lateral direction(slow axis) of diode laser, a fish-bone shape microstructure was used to control the lateral modes for the purpose of high lateral beam quality. In the vertical direction or the fast axis of laser, the Bragg reflection waveguide(BRW) was selected, in which light was confined by the photonic band-gap(PBG) effect rather than the conventional total interface reflection(TIR). The BRW lasers(BRLs) had demonstrated the advantages of large mode volume, high power and high brightness operation, which benefit for the solving of high vertical beam divergence, high catastrophic optical damage(COD) threshold, poor beam quality and low brightness of the diode lasers. Therefore, these techniques are in demand and important for many realistic applications.In this dissertation, the main works are as follows:1) The BA GaSb based BRLs are designed using the transfer matrix method and Bloch theory. And the design and calculation methods of BRLs are presented in detail.2) The dependence of far-field(FF) on the thickness of Bragg reflectors and center layer, the composition of Bragg reflector were simulated by using the Lumerical Mode Solutions software. The corresponding optical confinement factors(OCF) were also calculated. Finally, the 2μm GaSb based BRLs with an ultra-low vertical divergent FF angle less than 10° was optimized.3) A finite difference time domain(FDTD) 2D model was used to simulate the guided modes in the BA waveguide with the fish-bone microstructure using the commercially available Lumerical FDTD software package.4) The fish-bone trenches were fabricated on the waveguide of GaAs based BA BRLs, the result reveals that a decrease of 22.2% on the lateral divergence angles was achieved, which demonstrated the effectiveness of the designed microstructure on the improvement of divergence.5) 2μm GaSb based BA lasers with the fish-bone microstructure shows that a 56.4% improvement on the lateral divergence angles. The corresponding emission power is increased about 19%. The proposed fish-bone microstructure almost does not change the fabrication processing of BA lasers, and shows the advantages of simple fabrication, low cost and high volume producing, which supplies an effective approach for the low lateral divergence GaSb based BA lasers.