Silicon Photonic Biochemical Sensor on Chip Based on Interferometry and Phase-Generated-Carrier Demodulation

Abstract

Integrated biochemical sensors based on Mach-Zehnder interferometers (MZIs) rely on the evanescent field detection principle to monitor the phase shift induced by a refractive index change on the surface of the sensing arm, providing a high sensitivity thanks to the long interaction length with the analyte. This paper presents an integrated refractive index and biochemical sensor based on a pair of balanced MZIs realized on silicon-on-insulator. The device includes a thermal phase modulator in one of the branches of each MZI to extract univocally the induced phase change by applying active phase detection based on the phase generated carrier technique. The direct modulation of the MZI results in a simple configuration of the sensor, only requiring a fixed wavelength laser and a photodetector, enabling the possibility of full monolithic integration. The results of refractive index measurements show a detection limit down to 4.88 × 10-7 RIU. Additionally, an immunoassay reports the binding of anti-bovine serum albumin (BSA) to BSA, with anti-BSA concentrations down to 33.33 nM. Index Terms-Optical sensors, chemical and biological sensors, photonic integrated circuits, interferometry, phase modulation. I. INTRODUCTION I N THE past decades, there has been a growing interest in integrated photonic biochemical sensors for a wide range of applications, such as clinical diagnosis, food safety and chemical and biological warfare surveillance [1]. In particular, silicon

Interferometer-based chemical sensor on chip with enhanced responsivity and low-cost interrogation

“…For these reasons, most silicon-photonic devices based on 220nm-thick SOI are designed for TE polarization. Our reference device is in fact based on the fundamental TE-mode of a 220 × 480 nm 2 , which is the one used in [ 12 ].…”

Inverse design and characterization of compact, broadband, and low-loss chip-scale photonic power splitters

“…Even for design challenges traditionally dominated by intuition-based approaches, such as grating couplers, mirrors, waveguide bends, and beam splitters, inverse design can offer significant improvements by minimizing footprints [24][25][26] and extending bandwidths [27,28]. Here we are concerned with the inverse design of compact, highly efficient, broadband, 50:50 power splitters, which are essential devices in both quantum photonic architectures [29][30][31] and classical applications such as signal routing [32], spectroscopy [33], and imaging [34]. Our method applies to any material platform, but we consider silicon, which offers advanced fabrication technology and integration with electronics and nanomechanics [35].…”

High-Performance Bimodal Evanescent-Field Sensor With Coherent Phase Readout

“…To avoid ambiguity in the readout, modulation techniques combined with algorithms based on Fourier Series deconvolution or trigonometric properties can be used to obtain a linear readout at the expense of system simplicity and computational load [14], [19]. Phase-generated carrier (PGC) techniques have also been employed for univocal readout in MZI-based biosensors, using only two photodetectors, but require adding heaters to the chip in order to perform an external phase modulation [20]. Modal demultiplexing combined with coherent detection aided by an optical hybrid has the potential to provide both low-loss excitation and splitting of the sensing modes and inherently linear phase readout [21], [22].…”