Directly interfacing a photonic integrated circuit allows at best an alignment tolerance of a few micrometer due to the small dimensions of optical (coupling) features on chip, but when using microlenses integrated on the substrate-side, alignment tolerances for interfacing the chips can greatly be relaxed. This is demonstrated on a 750 μm thick chip with standard grating couplers (operation wavelength around 1550 nm). Low roughness silicon microlenses were realized by transferring reflowed photoresist into the silicon substrate using reactive ion etching. The microlens allows interfacing the chip from the backside with an expanded beam, drastically increasing lateral alignment tolerances. A 1 dB alignment tolerance of ±8 μm and ±11 μm (along and perpendicular to the grating coupler direction, respectively) was experimentally found when a 40 μm mode field diameter beam was used at the input.
Laser integration and photonics chip packaging are the two key challenges that require attention to drive down the cost/bit metric for silicon photonics based optical interconnects. We try to address the latter by demonstrating optical interfaces that fit well in an overall scheme of 2.5D/3D electro-optic integration needed for a high performance computing environment. A through-substrate coupling interface provides the benefit of bonding a silicon photonic chip face-up on a package substrate such that the device-side of the chip remains accessible for die-stacking and fiber-array packaging, thereby offering a promising alternative to flip-chip based packaging. In this paper, we demonstrate three through-substrate coupling elements to enable alignment tolerant and energy-efficient integration of silicon photonics with board-level or package-level optical interconnects : (i) a downward directionality O-band grating coupler with a peak -2.3 dB fiber-to-silicon waveguide coupling efficiency; (ii) polymer microlenses hybrid integrated onto the substrate of a silicon photonic chip to produce an expanded collimated beam at λ=1310 nm for a distance of more than 600 μm; (iii) a ball lens placed in a through-package via to result in a 14 μm chip-to-package 1-dB lateral alignment tolerance for coupling into a 20×24 µm squared cross-section board-level polymer waveguide.
We report the simulation and analytical results obtained for homogenous or bulk sensing of protein on Siliconon-
insulator strip waveguide based microring resonator. The radii of the rings considered are 5 μm and 20 μm;
the waveguide dimensions are 300 × 300 nm. A gap of (i) 200 nm and (ii) 300 nm exists between the ring and
the bus waveguide. The biomaterial is uniformly distributed over a thickness which exceeds the evanescent field
penetration depth of 150 nm. The sensitivities of the resonators are 32.5 nm/RIU and 17.5 nm/RIU (RIU - Refractive index unit) respectively.