Passive alignment between the light source and coupling lenses may be one of the crucial and yet challenging technical fields to produce low-cost optical modules for telecom and datacom applications. In our presentation, we report the current status of our integration technologies of both surface and edge emitting type lasers with coupling lenses. We propose surfacemountable silicon microlens whose diameter is identical to a conventional optical fiber. The microlens can be passively aligned in the silicon v-groove to realize beam coupling between an edge emitting laser diode and an optical fiber. Coupling efficiency of -3.2dB between distributed feed-back laser diode and a single-mode fiber was experimentally confirmed. Precise rod shape is fabricated by D-RIE technology. We also report monolithic integration of the silicon substrate and a surface-emitting light source accomplished by direct bonding technology. The corresponding collimating lens is fabricated on the back-surface of the same silicon substrate. Passive alignment between the light source and the corresponding lenses are ensured by using a double-view mask aligner with sub-micron accuracy.
We propose a silicon microlens that is mountable on a silicon v-groove platform for low-cost telecommunication optical modules. The proposed silicon microlens has a rod shape which has the diameter of 125 micrometers , identical to a single-mode fiber. Therefore, it can be passively embedded in the v-groove in conjunction with the optical fiber with high precision. We employed diffractive microlens that can be fabricated on the top surface of the rod by conventional LSI technology. Better coupling efficiency between a laser diode and an optical fiber is expected with silicon diffractive lenses as compared with conventional silica ones. The coupling efficiency of -0.7 dB between two single-mode fibers was obtained with silicon lenses significantly better than -1.4 dB of insertion loss obtained by a pair of silica diffractive lenses. With good coupling efficiency and the ease of packaging by surface mount technology (SMT), silicon diffractive microlens is promising for low-cost and high- performance optical module applications.