On-chip near-infrared gas sensing based on slow light mode multiplexing in photonic crystal waveguides.

Photonic crystal slow light waveguides present a breakthrough in the manipulation of optical signals and enhancing the interaction between light and matter. In particular, two-dimensional (2D) photonic crystal waveguides (PCWs) on silicon photonic chips hold promise in improving the sensitivity of on-chip gas sensors. However, the development of the gas sensors based on 2D PCWs suffers from a high propagation loss and a narrow slow light bandwidth.

Surface-enhanced infrared absorption (SEIRA) based on Metasurface: Principles, biochemical sensing applications, and future perspective.

As a powerful analytical technique, surface-enhanced infrared absorption (SEIRA) typically employs periodic nanostructured arrays to generate highly localized and intense electromagnetic near-field enhancements. Infrared vibrations of target sensing molecules located in these periodic nanostructured fields are enhanced by orders of magnitude enabling a spectroscopic characterization with unprecedented sensitivity. This remarkable enhancement effect enables SEIRA to overcome the inherent limitations of conventional infrared spectroscopy, particularly the small molecular absorption cross-sections.

On-chip near-infrared multi-gas sensing using chalcogenide anti-resonant hollow-core waveguides.

On-chip infrared spectroscopic gas sensing using a hollow-core anti-resonant reflecting optical waveguide (ARROW) with a large external confinement factor (ECF) was rarely reported due to the complex fabrication process and polarization dependence. Alternatively, we proposed ARROW gas sensors using chalcogenide (ChG) anti-resonant layers which require thermal evaporation and epoxy resin bonding for fabrication instead of the complicated wafer bonding process. Polarization characteristics and ethylene (CH) sensing performance at 1.

Development and Field Deployment of a ppb-Level SO/NO Dual-Gas Sensor System for Agricultural Early Fire Identification.

Sulfur dioxide (SO) and nitrogen dioxide (NO) are chemical indicators of crop straw combustion as well as significant atmospheric pollutants. It is challenging to promptly detect natural "wildfires" during agricultural production, which often lead to uncontrollable and substantial economic losses. Moreover, both "wildfires" and artificial "straw burning" practices pose severe threats to the ecological environment and human health.

Slow-Light-Enhanced Polarization Division Multiplexing Infrared Absorption Spectroscopy for On-Chip Wideband Multigas Detection in a 1D Photonic Crystal Waveguide.

Slow-light photonic crystal waveguide (PCW) gas sensors based on infrared absorption spectroscopy play a pivotal role in enhancing the on-chip interaction between light and gas molecules, thereby significantly boosting sensor sensitivity. However, two-dimensional (2D) PCWs are limited by their narrow mode bandwidth and susceptibility to polarization, which restricts their ability for multigas measurement. Due to quasi-TE and quasi-TM mode guiding characteristics in one-dimensional (1D) PCW, a novel slow-light-enhanced polarization division multiplexing infrared absorption spectroscopy was proposed for on-chip wideband multigas detection.

Near-Infrared Off-Axis Cavity-Enhanced Optical Frequency Comb Spectroscopy for CO/CO Dual-Gas Detection Assisted by Machine Learning.

Cavity-enhanced direct frequency comb spectroscopy (CE-DFCS) is widely used as a highly sensitive gas sensing technology in various gas detection fields. For the on-axis coupling incidence scheme, the detection accuracy and stability are seriously affected by the cavity-mode noise, and therefore, stable operation inevitably requires external electronic mode-locking and sweeping devices, substantially increasing system complexity. To address this issue, we propose off-axis cavity-enhanced optical frequency comb spectroscopy from both theoretical and experimental aspects, which is applied to the detection of single- and dual-gas of carbon monoxide (CO) and carbon dioxide (CO) in the near-infrared.

Mid-infrared auto-correction on-chip waveguide gas sensor based on 2f/1f wavelength modulation spectroscopy.

Compared to the most commonly used on-chip direct absorption spectroscopy (DAS) gas detection technique, the second harmonic (2f) based on-chip wavelength modulation spectroscopy (WMS) proposed by our group has the faculty to suppress noise and improve performance, but the accuracy of 2f WMS is easily affected by optical power variation. A mid-infrared auto-correction on-chip gas sensor based on 2f/1f WMS was proposed for decreasing the influence of the variation of optical power. The limit of detection of methane (CH) obtained by a chalcogenide waveguide with a length of 10 mm is 0.

Ultra-Wideband Mid-Infrared Chalcogenide Suspended Nanorib Waveguide Gas Sensors with Exceptionally High External Confinement Factor beyond Free-Space.

On-chip waveguide sensors are potential candidates for deep-space exploration because of their high integration and low power consumption. Since the fundamental absorption of most gas molecules exists in the mid-infrared (e.g.

WMS-based near-infrared on-chip acetylene sensor using polymeric SU8 Archimedean spiral waveguide with Euler S-bend.

SU8 is a cost-effective polymer material that is highly suitable for large-scale fabrication of waveguides. However, it has not been employed for on-chip gas measurement utilizing infrared absorption spectroscopy. In this study, we propose a near-infrared on-chip acetylene (CH) sensor using SU8 polymer spiral waveguides for the first time to our knowledge.

On-chip mid-infrared silicon-on-insulator waveguide methane sensor using two measurement schemes at 3.291 μm.

Portable or even on-chip detection of methane (CH) is significant for environmental protection and production safety. However, optical sensing systems are usually based on discrete optical elements, which makes them unsuitable for the occasions with high portability requirement. In this work, we report on-chip silicon-on-insulator (SOI) waveguide CH sensors at 3.

Mid-infrared ChG-on-MgF waveguide gas sensor based on wavelength modulation spectroscopy: publisher's note.

This publisher's note contains corrections to Opt. Lett.46, 4797 (2021)OPLEDP0146-959210.

Mid-infrared ChG-on-MgF waveguide gas sensor based on wavelength modulation spectroscopy.

A novel, to the best of our knowledge, mid-infrared chalcogenide (ChG) on magnesium fluoride () waveguide gas sensor was fabricated by using the lift-off method. was used as a lower cladding layer to increase the external confinement factor for enhancing light-gas interaction. Wavelength modulation spectroscopy (WMS) was used in carbon dioxide () detection at the wavelength of 4319 nm (2315.

Theoretical study of microcavity-enhanced absorption spectroscopy for mid-infrared methane detection using a chalcogenide/silica-on-fluoride horizontal slot-waveguide racetrack resonator.

The reported chalcogenide (ChG) rectangular waveguide sensors with a small evanescent field need a large waveguide length to obtain an enhanced light-gas interaction effect. To make such sensors compact and improve the light-gas interaction effect, a microcavity-enhanced absorption spectroscopy technique for methane (CH) detection was proposed using a mid-infrared chalcogenide/silica-on-fluoride horizontal slot-waveguide racetrack resonator. For the horizontal slot waveguide, an equivalent sensor model (ESM) and related formulations were proposed to simplify the analysis of the racetrack resonator sensor model (RRSM), and the ESM was verified through a comparison between the theoretical result of ESM and the simulation result of RRSM based on the finite element method (FEM).