Coupling optics of laser diode to triangular index fiber via upside down tapered cylindrical microlens on the tip of the fiber

Abstract Using the ABCD matrix framework, we estimate the coupling optics (CO) between a laser diode (LD) and a tapered cylindrical lensed circular core triangular index fiber (TIF). It is essential to note that the coupling optics provide nice performance in the vertical plane, whereas the horizontal plane exhibits inferior results. Taking care of the performance in the vertical plane only, we theoretically predict and assess the coupling efficiency (CE) using ABCD matrix formalism. We provide analytical formulae for coupling efficiencies. The said studies have been carried out for two frequently utilized wavelengths, namely 1.3 and 1.5 µm. In terms of coupling efficiency, the wavelength of 1.5 µm has been identified to be more effective. Our theory addresses the narrow aperture that the cylindrical microlens (CML) provides. The findings indicate the possibility of ensuring improved optical signal transmission by optimizing lens radius and distance of the laser source from the coupler. It will be highly beneficial to the designers and packagers dealing with this kind of coupler.