| The high-power laser diode array (LDA) has many advantages such as compactness, low cost, high photoelectric efficiency and high output of power et. al., but the output beam quaintly of the LDA is very poor. Phase-locking of the LDA by external cavity (EC) can improve its beam quaintly to enlarge its application scope, this technique is promising.The properties of a phase-locked LDA by internal coupling have been investigated for decades, but it is rare for the high- power LDA phase-locking by EC. In the research of the far field structure of a phase-locked LDA by internal coupling, the terms that "single lobe" and "double lobes" were commonly mentioned. But these descriptions are not accurate enough and, in some circumstances, will lead to an incorrect judgment for the order of super modes for a high-power LDA phase-locked by EC.The coherent output of a LDA has been achieved by a simple EC consisted of a commercial LDA, a fast axis collimation lens and an external mirror. The structure of the far field is very complex. The far field detailed structure of a LDA phase-locked by EC has been derived and been compared with the experiments results. The phase-locking far field of a high-power LDA with broad aperture andpitch, commonly, is multi-lobed irrespecting the order of a super mode (SM). When the LDA running in the highest super mode (HSM) or the lowest super mode (LSM), the structure of the far field is periodical single-iobed and the angular spacing between two neighbor lobes is equal to λ / d ; for the other SM, the far field is consisted of periodical lobe pairs, the angular spacing between two pairs is λ/d and that of the lobes in a pair is depend on the order of SM j; in a far field profile with broad divergence angle, the difference of the HSM and the LSM or the jth SM and the (M+1-j)th SM is only a angular displacement of λ/2d and it is difficult to distinguish these SMs unless the normal direction of the LDA facet is accurately known.
|
PDF Full Text Request