We demonstrate a compact interrogation method for resonance-based biosensors, based on an integrated photonic chip with an array of resonant-cavity enhanced photodetectors. Due to the high signal-to-noise ratio, wavelength shifts in the 10 pm range can be measured, orders of magnitude smaller than the sensor and interrogator linewidths. This approach allows the read-out of resonance-based optical biosensors with simple integrated components, potentially enabling compact and low-cost sensing systems for point-of-care diagnostics.
We demonstrate a novel, fully-integrated approach to spectral sensing in the near-infrared range suitable for analyzing the chemical composition of organic materials. The sensor consists of 16 detector pixels, each forming a resonant-cavity enhanced photodetector consisting of an InGaAs/InP photodiode and a tuning layer enclosed in a planar cavity formed by two metal mirrors. For wavelengths meeting the resonance condition of the optical cavity, the absorption in the photodiode is enhanced, which leads to a wavelength-specific response of the photodetector. As the thickness of the tuning layer is varied throughout the pixels, each of the 16 photodetectors features an individual complex spectral response with several peaks of about 50 nm linewidth and responsivity above 0.1 A/W. All pixels together cover the whole wavelength range from 900 nm to 1700 nm, allowing for the analysis of broad spectral features typical for diffuse reflectance spectra of organic materials in the near-infrared range. The photocurrents read-out from the spectral sensors can be combined with chemometric analysis methods to determine the material composition. We demonstrate the performance of the spectral sensor for the determinate of moisture in rice grains, leading to a coefficient of determination of R² = 0.97. Other demonstrated applications include the quantification of the sugar content in tomatoes, fat and protein content in raw cow milk and the classification of different types of plastic. With a size of 1.5 mm by 1.5mm and a fabrication scheme based on optical lithography, this on-chip spectral sensor yields potential for large-scale production. Together with the mechanical stability of the sensor, this approach is an important step towards portable, low-cost spectral sensing solutions.
Many high performance computers (HPC) and cloud computing applications rely on distributing tasks among large numbers of virtual and real servers. This implies that advancements in performance of data centers and HPCs is increasingly dependent on connectivity. In order to insure high degree of connectivity at increasing bit rates and distances the demand for large bandwidth-distance product connections is increasing. These can almost exclusively be provided using optical interconnects. Traditionally optical-interconnect come in the form of pluggable transceivers. However the increases in number of connections and bit-rate poses a limit to further scaling (the front-plate bottleneck). A shift towards mid-board optics is in the making but requires solutions which are compact, power efficient and low cost for manufacturing. In this talk we will present our most recent demonstrations of high density optical interconnect solutions as well as high density switches. First some details about the design aspects and advantages of compact electronic switches employing mid-board optical engines will be discussed. Then, for addressing the challenge of low cost optical interconnects, we will give details on our recent work targeting high channel count VCSELs based sub-modules. Results based on 2.5D and 3D assembly on high resistivity silicon will be discussed as well as the use of direct die attach to flexible PCBs for making high density interconnects.
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