There is a rapidly growing demand to use silicon and silicon nitride (Si 3 N 4 ) integrated photonics for sensing applications, ranging from refractive index to spectroscopic sensing. By making use of advanced CMOS technology, complex miniaturized circuits can be easily realized on a large scale and at a low cost covering visible to mid-IR wavelengths. In this paper we present our recent work on the development of silicon and Si 3 N 4 -based photonic integrated circuits for various spectroscopic sensing applications. We report our findings on waveguide-based absorption, and Raman and surface enhanced Raman spectroscopy. Finally we report on-chip spectrometers and on-chip broadband light sources covering very near-IR to mid-IR wavelengths to realize fully integrated spectroscopic systems on a chip.

Abstract-In this letter, we report a novel high-index-contrast silicon nitride arrayed waveguide grating (AWG) for very nearinfrared wavelengths. This device is fabricated through a process compatible with a complementary metal-oxide-semiconductor fabrication line and is therefore suitable for mass fabrication. The large phase errors that usually accompany high-index-platform AWGs are partly mitigated through design and fabrication adaptions, in particular the implementation of a two-level etch scheme. Multiple devices are reported, among which a 0.3-mm 2 device which, after the subtraction of waveguides loss, has a −1.2 dB on-chip insertion loss at the peak of the central channel and 20-dB crosstalk for operation ∼900 nm with a channel spacing of 2 nm. These AWGs pave the way for numerous largescale on-chip applications pertaining to spectroscopy and sensing.

We present a low-cost integrated nanophotonic lab-on-a-chip platform suitable for point-of-care (POC) biomarker analysis.

Tuberculosis (TB) is the leading global cause of death from a single infectious agent. Registered incidence rates are low, especially in low-resource countries with weak health systems, due to the disadvantages of current diagnostic techniques. A major effort is directed to develop a point-of-care (POC) platform to reduce TB deaths with a prompt and reliable low-cost technique. In the frame of the European POCKET Project, a novel POC platform for the direct and non-invasive detection of TB in human urine was developed. The photonic sensor is integrated in a disposable cartridge and is based on a highly sensitive Mach-Zehnder Interferometer (MZI) transducer combined with an on-chip spectral filter. The required elements for the read-out are integrated in an instrument prototype, which allows real-time monitoring and data processing. In this work, the novel POC platform has been employed for the direct detection of lipoarabinomannan (LAM), a lipopolysaccharide found in the mycobacterium cell wall. After the optimization of several parameters, a limit of detection of 475 pg/mL (27.14 pM) was achieved using a direct immunoassay in undiluted human urine in less than 15 minutes. A final validation of the technique was performed using twenty clinical samples from TB patients and healthy donors, allowing the detection of TB in people regardless of HIV coinfection. The results show excellent correlation to those obtained with standard techniques. These promising results demonstrate the high sensitivity, specificity and applicability of our novel POC platform, which could be used during routine checkups in developing countries.

Abstract:The Mach-Zehnder interferometer (MZI) and the Vernier-cascade are highly responsive photonic sensors with large design freedom. They are therefore very suitable for interrogation through a broadband source and an on-chip spectral filter, a sensing scheme that is well equipped for point-of-care applications. In this work, the MZI is shown to outperform the Vernier-cascade through a better minimum detectable wavelength shift as well as a higher power efficiency, indicating its superiority in this sensing scheme. Fabricated MZIs yield bulk detection limits down to 8.8 × 10 −7 refractive index units (RIU) in a point-of-care compatible measuring setup, indicating the potential of the proposed sensing scheme.