- PhD Students
Optical Quilt Packaging (OQP) is a scheme for chip-to-chip optical integration that will allow for direct optical interconnects (i.e., without external waveguides) between semiconductor optical sources, on-chip beam- combining optics, optical waveguides, and detectors.
On-chip optical sensors are compact platforms for sensitive, low-cost monitoring of biological and chemical species in real time by measuring changes in light that interacts with the analyte on a chip. Mid-infrared (MIR) sensors could play a vital role in biological and chemical sensing because many relevant molecules exhibit strong vibrational resonance in the MIR spectrum of λ~3-14 µm. Quantum cascade lasers (QCL) are a common source of MIR. As QCL is a very expensive platform to build the sensor (with source, interaction medium, and detector), there is a greater need to build the sensors with discrete material source, interaction medium and detector. To realize such a scheme a high-efficiency, low-cost inter-chip optical coupling technique is required.
Optical “Quilt Packaging®” (OQP) is a novel microelectromechanical system (MEMS) based packaging technique for low-cost, highly efficient optical coupling between MIR laser sources and interaction platforms. Waveguides of separate substrates are aligned with sub-micron accuracy by protruding, lithographically defined interdigitated copper nodules placed on the side of the chip. Chip-to-chip optical integration via Optical Quilt Packaging allows for direct optical interconnects between semiconductor optical sources, on-chip beam-combining optics, optical waveguides, and detectors. In Optical Quilt Packaging waveguides of separate substrates are aligned with sub-micron accuracy by protruding, lithographically-defined interdigitated copper nodules on the side of the chip. The technique inherently provides extremely wide spectral coverage with sources ranging from the visible, infrared, and mid-infrared. At the same time it presents the scope to design separately optimized optical sources, interaction mediums, and detectors preferred for enhanced performance on chip mid-infrared optical sensing. It is possible to combine optical waveguide chips made with both Si/Ge and III-IV materials into a single heterogeneous platform using OQP using conventional fabrication processes.
We fabricated initial test OQP structures on a bare Si wafer. The double-trench ridge waveguide structures on two separate chips were aligned via Cu nodules with a resulting misalignment of ~1 μm and an inter-chip waveguide-to-waveguide distance of ~10 μm (left figure below). We are working on fabricating this OQP structure on a Ge-on-Si platform, which could be used as the sensing platform of the modular mid-IR detection system (right figure below).
Please see the published results.
1. Tahsin Ahmed, Thomas Butler, Aamir A. Khan, Jason M. Kulick, Gary H. Bernstein, Anthony J. Hoffman, and Scott S. Howard, “FDTD modeling of chip-to-chip waveguide coupling via optical quilt packaging,” Proc. SPIE 8844, Optical System Alignment, Tolerancing, and Verification VII, 88440C (September 10, 2013). http://proceedings.spiedigitallibrary.org/proceeding.aspx?articleid=1736995
2. Tahsin Ahmed, Aamir A Khan, Genevieve Vigil, Jason M Kulick, Gary H Bernstein, Anthony J Hoffman, Scott S Howard, “Optical Quilt Packaging: A New Chip-to-Chip Optical Coupling and Alignment Process for Modular Sensors,” CLEO: Applications and Technology,San Jose, California, USA, June 8-13, 2014.