Versatile Lithium Niobate Platform for Photoacoustic/Thermoelastic Gas Sensing and Photodetection

We present a lithium niobate multi-functional platform (LN-MFP) that seamlessly integrates photoacoustic spectroscopy, light induced thermoelastic spectroscopy, and photodetection into a single on-chip device. By levering LN's strong piezoelectric and thermoelastic properties, along with an optimized fork-shaped design, our platform achieves high sensitivity and selectivity across a broad spectral range—from visible to long-wave infrared wavelengths. Experimentally we demonstrate trace gas detection of nitrogen dioxide, water vapor, acetylene, carbon dioxide, methane, and ammonia, achieving parts-per-billion detection limits. To further enhance on-chip integration, we implement a custom packaging solution featuring a printed circuit board with transimpedance amplification and a quantum cascade laser chip, enabling direct wire bonding to the LN-MFP. Exploiting a 4.6 µm quantum cascade laser chip, we successfully demonstrate carbon monoxide detection via second-harmonic measurements, highlighting the LN-MFP’s potential for fully integrated spectroscopic applications. This compact, integrated, multi-functional architecture significantly reduces system complexity and footprint, paving the way for portable, scalable sensing systems in environmental monitoring, point-of-care diagnostics, and on-site chemical analysis, marking a key advancement in integrated photonics.