scholarly journals Wavelength-Flattened Directional Coupler Based Mid-Infrared Chemical Sensor Using Bragg Wavelength in Subwavelength Grating Structure

Nanomaterials ◽  
2018 ◽  
Vol 8 (11) ◽  
pp. 893 ◽  
Author(s):  
Bowei Dong ◽  
Ting Hu ◽  
Xianshu Luo ◽  
Yuhua Chang ◽  
Xin Guo ◽  
...  
Keyword(s):  
Directional Coupler ◽  
Chemical Sensor ◽  
Bragg Reflection ◽  
Coupling Efficiency ◽  
High Sensitivity ◽  
Fdtd Simulation ◽  
Bragg Wavelength ◽  
Mid Infrared ◽  
Subwavelength Grating ◽  
Surrounding Refractive Index

In this paper, we report a compact wavelength-flattened directional coupler (WFDC) based chemical sensor featuring an incorporated subwavelength grating (SWG) structure for the mid-infrared (MIR). By incorporating a SWG structure into directional coupler (DC), the dispersion in DC can be engineered to allow broadband operation which is advantageous to extract spectroscopic information for MIR sensing analysis. Meanwhile, the Bragg reflection introduced by the SWG structure produces a sharp trough at the Bragg wavelength. This sharp trough is sensitive to the surrounding refractive index (RI) change caused by the existence of analytes. Therefore, high sensitivity can be achieved in a small footprint. Around fivefold enhancement in the operation bandwidth compared to conventional DC is achieved for 100% coupling efficiency in a 40 µm long WFDC experimentally. Detection of dichloromethane (CH2Cl2) in ethanol (C2H5OH) is investigated in a SWG-based WFDC sensor 136.8 µm long. Sensing performance is studied by 3D finite-difference time domain (FDTD) simulation while sensitivity is derived by computation. Both RI sensing and absorption sensing are examined. RI sensing reveals a sensitivity of −0.47% self-normalized transmitted power change per percentage of CH2Cl2 concentration while 0.12% change in the normalized total integrated output power is realized in the absorption sensing. As the first demonstration of the DC based sensor in the MIR, our device has the potential for tertiary mixture sensing by utilizing both changes in the real and imaginary part of RI. It can also be used as a broadband building block for MIR application such as spectroscopic sensing system.

Chemical Sensors Based on Fiber Bragg Grating

2011 ◽  
Vol 84-85 ◽  
pp. 582-585 ◽  
Author(s):  
Ming Fu Zhao ◽  
De Yi Huang ◽  
Bin Zhou ◽  
Lei Zi Jiao
Keyword(s):  
Refractive Index ◽  
Fiber Bragg Grating ◽  
Chemical Sensor ◽  
Bragg Grating ◽  
Wavelength Shift ◽  
Bragg Wavelength ◽  
Chemical Substances ◽  
Fbg Sensor ◽  
Surrounding Refractive Index ◽  
The Relationship

In this paper, measurement method for the refractive index of chemical substances based on fiber Bragg grating (FBG) sensor was proposed. The relation between Bragg wavelength shift and surrounding refractive index (SRI) was analyzed theoretically and experimentally. The SRI sensitivity of the chemical sensor could be enhanced by reducing the cladding thickness of the FBG using hydrofluoric acid (HF) solution etching process. The experimental results indicated that the variation of Bragg wavelength increased as the SRI increased. In the low SRI region, the relationship between the Bragg wavelength shift and the change of the SRI was approximately linear.

scholarly journals Towards lab-on-chip ultrasensitive ethanol detection using photonic crystal waveguide operating in the mid infrared

Nanophotonics ◽  
2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Ali Rostamian ◽  
Ehsan Madadi-Kandjani ◽  
Hamed Dalir ◽  
Volker J. Sorger ◽  
Ray T. Chen
Keyword(s):  
Photonic Crystal ◽  
Slow Light ◽  
High Sensitivity ◽  
Guided Wave ◽  
Silicon On Insulator ◽  
Group Index ◽  
Photonic Crystal Waveguide ◽  
Mid Infrared ◽  
Lab On Chip ◽  
On Chip

Abstract Thanks to the unique molecular fingerprints in the mid-infrared spectral region, absorption spectroscopy in this regime has attracted widespread attention in recent years. Contrary to commercially available infrared spectrometers, which are limited by being bulky and cost-intensive, laboratory-on-chip infrared spectrometers can offer sensor advancements including raw sensing performance in addition to use such as enhanced portability. Several platforms have been proposed in the past for on-chip ethanol detection. However, selective sensing with high sensitivity at room temperature has remained a challenge. Here, we experimentally demonstrate an on-chip ethyl alcohol sensor based on a holey photonic crystal waveguide on silicon on insulator-based photonics sensing platform offering an enhanced photoabsorption thus improving sensitivity. This is achieved by designing and engineering an optical slow-light mode with a high group-index of n g  = 73 and a strong localization of modal power in analyte, enabled by the photonic crystal waveguide structure. This approach includes a codesign paradigm that uniquely features an increased effective path length traversed by the guided wave through the to-be-sensed gas analyte. This PIC-based lab-on-chip sensor is exemplary, spectrally designed to operate at the center wavelength of 3.4 μm to match the peak absorbance for ethanol. However, the slow-light enhancement concept is universal offering to cover a wide design-window and spectral ranges towards sensing a plurality of gas species. Using the holey photonic crystal waveguide, we demonstrate the capability of achieving parts per billion levels of gas detection precision. High sensitivity combined with tailorable spectral range along with a compact form-factor enables a new class of portable photonic sensor platforms when combined with integrated with quantum cascade laser and detectors.

scholarly journals Mid-infrared photoacoustic gas monitoring driven by a gas-filled hollow-core fiber laser

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Yazhou Wang ◽  
Yuyang Feng ◽  
Abubakar I. Adamu ◽  
Manoj K. Dasa ◽  
J. E. Antonio-Lopez ◽  
...  
Keyword(s):  
Fiber Laser ◽  
Signal To Noise Ratio ◽  
High Sensitivity ◽  
Laser Source ◽  
High Signal ◽  
Mid Infrared ◽  
Raman Fiber Laser ◽  
Custom Made ◽  
Core Fiber ◽  
Detection Technologies

AbstractDevelopment of novel mid-infrared (MIR) lasers could ultimately boost emerging detection technologies towards innovative spectroscopic and imaging solutions. Photoacoustic (PA) modality has been heralded for years as one of the most powerful detection tools enabling high signal-to-noise ratio analysis. Here, we demonstrate a novel, compact and sensitive MIR-PA system for carbon dioxide (CO2) monitoring at its strongest absorption band by combining a gas-filled fiber laser and PA technology. Specifically, the PA signals were excited by a custom-made hydrogen (H2) based MIR Raman fiber laser source with a pulse energy of ⁓ 18 μJ, quantum efficiency of ⁓ 80% and peak power of ⁓ 3.9 kW. A CO2 detection limit of 605 ppbv was attained from the Allan deviation. This work constitutes an alternative method for advanced high-sensitivity gas detection.

scholarly journals Fabrication of Graphene Nanomesh FET Terahertz Detector

Micromachines ◽  
2021 ◽  
Vol 12 (6) ◽  
pp. 641
Author(s):  
Yuan Zhai ◽  
Yi Xiang ◽  
Weiqing Yuan ◽  
Gang Chen ◽  
Jinliang Shi ◽  
...  
Keyword(s):  
Room Temperature ◽  
Energy Gap ◽  
Coupling Efficiency ◽  
High Sensitivity ◽  
Fabrication Process ◽  
Monolayer Graphene ◽  
Terahertz Waves ◽  
Wet Process ◽  
Graphene Nanomesh ◽  
Thz Detector

High sensitivity detection of terahertz waves can be achieved with a graphene nanomesh as grating to improve the coupling efficiency of the incident terahertz waves and using a graphene nanostructure energy gap to enhance the excitation of plasmon. Herein, the fabrication process of the FET THz detector based on the rectangular GNM (r-GNM) is designed, and the THz detector is developed, including the CVD growth and the wet-process transfer of high quality monolayer graphene films, preparation of r-GNM by electron-beam lithography and oxygen plasma etching, and the fabrication of the gate electrodes on the Si3N4 dielectric layer. The problem that the conductive metal is easy to peel off during the fabrication process of the GNM THz device is mainly discussed. The photoelectric performance of the detector was tested at room temperature. The experimental results show that the sensitivity of the detector is 2.5 A/W (@ 3 THz) at room temperature.

A Mid-Infrared Dual-Comb Spectrometer for High Sensitivity Multi-Component Trace Gas Detection

2020 ◽  
Author(s):  
Leonard Nitzsche ◽  
Jens Goldschmidt ◽  
Jens Kießling ◽  
Sebastian Wolf ◽  
Frank Kühnemann ◽  
...  
Keyword(s):  
High Sensitivity ◽  
Gas Detection ◽  
Trace Gas ◽  
Trace Gas Detection ◽  
Mid Infrared

scholarly journals On-chip silicon mode blocking filter employing subwavelength-grating based contra-directional coupler

2018 ◽  
Vol 26 (25) ◽  
pp. 33005 ◽  
Author(s):  
Yu He ◽  
Yong Zhang ◽  
Hongwei Wang ◽  
Yikai Su
Keyword(s):  
Directional Coupler ◽  
Subwavelength Grating ◽  
On Chip

Chaos of interband cascade lasers in the mid-infrared regime

2020 ◽  
Author(s):  
Yu Deng ◽  
Zhuo-Fei Fan ◽  
Shiyuan Zhao ◽  
Frédéric Grillot ◽  
Cheng Wang
Keyword(s):  
Semiconductor Lasers ◽  
Near Infrared ◽  
Optical Feedback ◽  
Nonlinear Dynamical Systems ◽  
Initial Conditions ◽  
Electrical Power ◽  
High Sensitivity ◽  
Light Sources ◽  
Mid Infrared ◽  
Operation Conditions

Abstract Chaos in nonlinear dynamical systems is featured with irregular appearance and with high sensitivity to initial conditions. Near-infrared semiconductor lasers subject to optical feedback from an external reflector are popular chaotic light sources, which have enabled multiple applications. Here, we report the fully-developed chaos in a mid-infrared interband cascade laser with external optical feedback. The chaos leads to significant electrical power enhancement over a frequency span of 500 MHz. In addition, the laser also exhibits periodic oscillations or low-frequency fluctuations before producing chaos, depending on the operation conditions. This work paves the way for extending chaos investigations from the near-infrared regime to the mid-infrared regime, which can stimulate potential applications in this spectral range.

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