Optimization of taper structures for III-V on Silicon lasers

Abstract

IntroductionUsing silicon as a platform for realizing complex integrated photonic circuits is rapidly gaining interest both from the scientific community as from the industry. Tremendous progress in realizing passive devices, high speed modulators and Ge-based detectors has been made over the last decade (for a recent review see [1]). However, efficient light generation directly from silicon, given its indirect bandgap, has not yet been shown. Therefore an alternative approach based on bonding high quality epi-layers on prepatterned silicon waveguide structures has been developed by several groups . We recently proposed a new structure [6] whereby light in the gain section is maximally confined in the III-V quantum well layers. At the ends of the gain section, light is coupled to the silicon waveguide layers using an adiabatic taper. Initial results showed Fabry-Perot type devices operating with threshold currents as low as 30mA and output powers up to 4mW [6]. Here we present a study focusing on the adiabatic taper and show how its design influences the operation of the device.

Novel adiabatic tapered couplers for active III–V/SOI devices fabricated through transfer printing

“…Such optical coupling structures can be made highly efficient [16,17,18] and ultra-compact [19] but typically require a lateral alignment accuracy better than 300 nm [19,20]. Currently the alignment accuracy in high-throughput transfer printing lies between 500 nm and 1 µm such that those conventional coupling structures are not suited for transfer printing.…”

Ultra-thin DVS-BCB adhesive bonding of III-V wafers, dies and multiple dies to a patterned silicon-on-insulator substrate

“…6. Recently, heterogeneously integrated III-V/silicon lasers and photodetectors, using this 'cold bonding' method have been demonstrated [7,[19][20][21]. The results illustrate the robustness and solid bonding strength during the III-V opto-electronic component fabrication and we believe it can provide a promising alternative to a direct bonding technique for the fabrication of integrated photonic components.…”

“…The major challenge in the bonding process is the fact that deep submicrometer layer thicknesses are required to achieve optical coupling from the top active III-V layer into the bottom SOI waveguides. This optical coupling can be achieved in various ways, including the use of hybrid modes [8,17] and the use of a double taper structure, using taper-based mode transformers both in the III-V and silicon waveguides [7,[18][19][20]. Both approaches can be made tolerant to bonding layer thickness variations on the order of tens of nanometer.…”

“…This approach shows high yield for ultra-thin bonding thicknesses below 50 nm, as well as a good uniformity of the DVS-BCB layer thickness after wafer bonding over the full wafer area. This process was applied to achieve ultra-thin DVS-BCB bonding layers for the fabrication of several photonic devices, such as III-V/SOI lasers [7,[18][19][20][21].…”