Theory And Experimental Study On Coherent Fiber Coupling Of Laser Diode Array

Laser Diode Array (LDA), including linear laser diode array and laser diode stack, is an attractive technique to realize higher output power. It has applied to many fields such as material processing, communication, medical, diode pumped solid laser and military because of its high power, high efficiency, small size and long lifetime. However, as a result of its low spatial coherence, LDA suffers from a poor beam quality which limits the direct application in many fields. Therefore, to improve the beam quality of LDA is an essential work to extend the field of its application. The existing phase-locking means are some feedback devices which direct role in LDA while they can not improve the spatial symmetry of LDA efficiently. They also have the problem how to select the fundamental super mode.Fiber coherent coupling is a novel phase-locking means which can improve the spatial symmetry because of the beam shaping of fiber array. This thesis founds the theory model of LDA coherently coupled by fiber array, and deduces coupling coefficients matrix and the near/far field distribution of LDA. The phase-locking mean is easier to work in fundamental super mode than other means. A theory model needs to be founded, for the reason that phase locking of fiber coherent coupling is sensitive of the parameters of its cavity. This thesis founded the super mode theory model of fiber coherent coupling LDA by coupled mode theory. The coupling coefficient matrix and near/far field intensity distribution was deduced. Furthermore, we found that the fundamental mode is easier to selected than higher modes. We analyzed the coupling coefficient of the LDA phase-locked by fiber array and found the best result of the parameters of some classical cavities by genetic algorithm. Then we analyzed the stability of different result and got the cavity which is most suitable for phase-locking.Finally, we achieve the phase-lock of LDA coherently coupled by fiber array in the condition that the work current is little higher then threshold current, while the FWHM of the spectrum has narrowed to 0.3nm.