Migrating the Mach-Zehnder chemical and bio-sensor to the mid-infrared region

Abstract

The properties of integrated optical phase-modulated Mach-Zehnder interferometers (IO-MZI) are used to set up a new generation of chemical and biochemical sensors working in the mid-infrared. First applications of the MZI principle were introduced in the beginning 1990s. They range from a gas sensor to monitor organic solvent concentrations 1 to setting up an immunoassay for the detection of the herbicide simazine 2 . Most if not all sensors of MZI type operate at wavelengths of the visible or near infrared spectrum. There are several reasons to change this strategy and move into the mid-infrared spectral range (MIR): higher manufacturing tolerances, increased evanescent field penetration depth, signal amplification by surface enhanced infrared absorption effect (SEIRA), species identification by MIR fingerprints.The basis of the planned MIR-MZI is a GaAs waveguide pattern epitaxially grown on a substrate 3 . As a first step towards nanostructuring the waveguide surface, chemical deposition of Au nanoparticles on GaAs transducers was established. For the use of MIR-MZI sensors in bioanalytical assay development, chemical immobilization of molecular recognition elements on GaAs transducers was carried out. The modified surfaces were characterized by atomic force microscopy (AFM), dark field microscopy, contact angle measurements and ellipsometric data as well as by a modified version of Reflectometric Interference Spectroscopy (RIfS) 4 . It was possible to monitor both the immobilization of gold nanoparticles and time-resolved specific binding using a model antibody antigen assay.After successful setup of relevant assays with RIfS, e.g. the detection of bacteria or endocrine disruptors, the assays are designed to be transferred onto the mid-infrared Mach-Zehnder interferometer.

Critical assessment of relevant methods in the field of biosensors with direct optical detection based on fibers and waveguides using plasmonic, resonance, and interference effects

“…A photograph of the reader, a diagram of on-chip components, and the results of the biomolecular interaction in case of C-reactive protein is given [319]. An interesting idea is the migration of the Mach-Zehnder chemical sensor and biosensor to the mid-infrared region (MIR) as has been done in the application of the new device for the detection of the herbicide simazine [320,321]. By these means, selectivity information of MIR and sensitivity of Mach-Zehnder can be combined.…”

Gallium arsenide waveguides as a platform for direct mid-infrared vibrational spectroscopy

“…For photonic sensing devices, different structural sensing architectures based on thin-film GaAs waveguide technology have been recently pioneered by the research team of Mizaikoff and collaborators. However, to date, such sensing concepts including slab waveguides [2][3][4] and Mach-Zehnder interferometers (MZI) have been combined with cascade laser light sources (i.e., quantum and interband cascade lasers [QCLs, ICLs]) rather than broadband infrared spectrometers [5][6][7]. Hence, the present study for the first time combines GaAs waveguides with Fourier transform infrared (FT-IR) spectroscopy facilitating a more ubiquitous usage of this new generation of waveguide materials.…”

“…Thiol-terminated long-chained organic molecules are in fact ideally suited for GaAs surface modification, as-similarly to gold-thiol anchoring groups also strongly bind to GaAs [9,10]. Bifunctional SAMs allow for further chemical modification after attachment of a first monolayer [5,11]. It should be noted though that passivating native oxide layers have to be removed from the GaAs surface prior to any immobilization scheme [12].…”

Highly Sensitive Refractive Index Sensor Based on Polymer Long-Period Waveguide Grating With Liquid Cladding

“…However, considering the development of sensor-on-chip (SOC), and the compatibility and integration of the waveguide sensor and correspondence signal process system, the planar waveguide has more priority in the application of sensor fields. Currently, different working principles such as micro-ring/micro-cavity [5][6][7][8], Mach-Zehnder (M-Z) interferometer [9,10], and slot waveguide [11] are widely used to form sensors, and the corresponding sensor sensitivity is normally in the order of 10 2 -10 3 nm/RIU.…”