Recess integration of micro-cleaved laser diode platelets with dielectric waveguides on silicon

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Abstract
Ongoing research directed at integrating 1.55 μm III-V ridge waveguide gain elements (i.e. diode lasers and semiconductor optical amplifiers) co-axially aligned with, and coupled to, silicon oxy-nitride waveguides on silicon substrates is presented. The integration techniques used are highly modular and consistent with fabricating waveguides on Si-CMOS wafers and doing the integration of the III-V gain elements after all standard front- and back-end Si processing has been completed. A novel micro-cleaving technique is used to produce active ridge waveguide platelets on the order of 6 µm thick and 100 μm wide, with precisely controlled lengths, in the current work 300 ± 1 μm, and cleaved end facets. Typical ridge guide micro-cleaved platelet lasers have thresholds under 30 mA. Micro-cleaved platelets are bonded within dielectric recesses etched through the oxy-nitride (SiOxNy) waveguides on a wafer so the ridge and SiOxNy waveguides are co-axially aligned. Transmission measurements indicate coupling losses are as low as 5 db with air filling the gaps between the waveguide ends, and measurements made through filled gaps indicate that the coupling losses can be reduced to below 1.5 dB with a high index (n = 2.2) dielectric fill. Simulations indicate that with further optimization of the mode profile in the III-V waveguide the loss can be reduced to below 1 dB. The paper concludes with a discussion of device design and optimization for co-axial recess integration, and with a comparison of co-axial coupling with the hybrid evanescent vertical coupling III-V/Si integration approach recently introduced by researchers at UCSB and Intel.

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