Investigation of collimating and focusing lenses' impact on laser diode stack beam parameter product.
The paper presents a new expression for determining the beam parameter product of a multi-emitter laser diode module made by stacking several single emitter chips. The proposed formula takes into account the effect of collimating and focusing lenses and has been validated experimentally, obtaining excellent agreement between theoretical expectations and measurements. A practical application to optimize the lenses' configuration for the design of a fiber-coupled multi-emitter module is also reported.