{"id":3128,"date":"2011-07-19T20:13:43","date_gmt":"2011-07-19T20:13:43","guid":{"rendered":"https:\/\/mtlsites.mit.edu\/annual_reports\/2011\/?p=3128"},"modified":"2011-07-19T20:13:43","modified_gmt":"2011-07-19T20:13:43","slug":"co-axial-integration-of-iii-v-ridge-waveguide-laser-diodes-with-sioxny-waveguides-on-silicon-2","status":"publish","type":"post","link":"https:\/\/mtlsites.mit.edu\/annual_reports\/2011\/co-axial-integration-of-iii-v-ridge-waveguide-laser-diodes-with-sioxny-waveguides-on-silicon-2\/","title":{"rendered":"Co-axial Integration of III-V Ridge-waveguide Laser Diodes with SiOx<\/sub>Ny<\/sub> Waveguides on Silicon"},"content":{"rendered":"

Our ongoing research integrating 1.55-\u00b5m 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 has made significant strides in the past year.\u00a0 We are working towards the goal of co-axially coupling III-V laser diodes and semiconductor optical amplifiers with waveguides on Si wafers; to do so, we use techniques consistent with fabricating waveguides on Si-CMOS wafers and integrating the III-V gain elements after all standard front- and back-end Si processing has been completed.<\/p>\n

A novel micro-cleaving technique has been used to produce active ridge waveguide platelets on the order of 6 \u00b5m thick and 100 \u00b5m wide, with precisely controlled lengths (in the current work 300 \u00b1 1.25 \u00b5m) and very high-quality end facets.\u00a0 Typical ridge guide platelet lasers have thresholds under 30 mA.<\/p>\n

Passive micro-cleaved platelets have been integrated within dielectric recesses etched through the oxy-nitride (SiOx<\/sub>Ny<\/sub>) waveguides on a wafer so that the ridge and SiOx<\/sub>Ny<\/sub> waveguides are co-axially aligned.\u00a0 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.\u00a0 Simulations indicate that with further optimization of the mode profile in the III-V waveguide, the loss can be reduced to below 1 dB.<\/p>\n

We have also performed extensive device design and optimization for co-axial recess integration and have recently completed a comparison of co-axial coupling with the evanescently coupled III-V\/Si hybrid integration approach recently introduced by researchers at UCSB and Intel.\u00a0 The latter comparison revealed that the approach we have taken, co-axial end-fire coupling, and the UCSB\/Intel approach, vertical evanescent coupling, are complementary, with each optimal for certain applications.\u00a0 At the same time it pointed out a number of distinct advantages for co-axial coupling of recess-integrated platelet lasers including higher operating efficiency, smaller device footprint, greater flexibility in choice of materials, lower cost, higher modularity, and easier integration of different wavelength emitters [1<\/a>] <\/sup>.<\/p>\n\n\t\t