Study and Characterization of Silicon Nitride Optical Waveguide Coupling with a Quartz Tuning Fork for the Development of Integrated Sensing Platforms

Study and Characterization of Silicon Nitride Optical Waveguide Coupling with a Quartz Tuning Fork for the Development of Integrated Sensing Platforms

This work demonstrates an ultra-compact optical gas-sensing system, consisting of a pigtailed laser diode emitting at 1392.5 nm for water vapor (H<sub>2</sub>O) detection, a silicon nitride (Si<sub>3</sub>N<sub>4</sub>) optical waveguide to guide the laser light,...

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Bibliographic Details
Main Authors: Luigi Melchiorre, Ajmal Thottoli, Artem S. Vorobev, Giansergio Menduni, Angelo Sampaolo, Giovanni Magno, Liam O’Faolain, Vincenzo Spagnolo
Format: Article
Language:English
Published: MDPI AG 2025-06-01
Series:Sensors
Subjects:
LITES
optical gas sensing
photonic integration
piezoelectric resonator
QEPAS
quartz tuning fork
Online Access:https://www.mdpi.com/1424-8220/25/12/3663
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Summary:This work demonstrates an ultra-compact optical gas-sensing system, consisting of a pigtailed laser diode emitting at 1392.5 nm for water vapor (H<sub>2</sub>O) detection, a silicon nitride (Si<sub>3</sub>N<sub>4</sub>) optical waveguide to guide the laser light, and a custom-designed, low-frequency, and T-shaped Quartz Tuning Fork (QTF) as the sensitive element. The system employs both Quartz-Enhanced Photoacoustic Spectroscopy (QEPAS) and Light-Induced Thermoelastic Spectroscopy (LITES) techniques for trace gas sensing. A 3.8 mm-wide, S-shaped waveguide path was designed to prevent scattered laser light from directly illuminating the QTF. Both QEPAS and LITES demonstrated comparably low signal-to-noise ratios (SNRs), ranging from 1.6 to 3.2 for a 1.6% indoor H<sub>2</sub>O concentration, primarily owing to the reduced optical power (~300 μW) delivered to the QTF excitation point. These results demonstrate the feasibility of integrating photonic devices and piezoelectric components into portable gas-sensing systems for challenging environments.
ISSN:1424-8220

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