Photonic Gas Research Articles

Silicon-based double fano resonances photonic integrated gas sensor

The telecommunication wavelengths are crucial for developing a photonic integrated circuit (PIC). The absorption fingerprints of many gases lie within these spectral ranges, offering the potential to create a miniaturized gas sensor for PIC. This work presents novel double Fano resonances within the telecommunication band, based on silicon metasurfaces for selective gas sensing applications. Our proposed design comprises periodically coupled nanodisk and nanobar resonators mounted on a quartz substrate. Fano resonances can be engineered across the range from λ = 1.52 μm to λ = 1.7 μm by adjusting various geometrical parameters. A double detection sensor of carbon monoxide (CO) at λ = 1.566 μm and nitrous oxide (N2O) at λ = 1.674 μm is developed. The sensor exhibits exceptional refractometric sensitivity to CO of 1,735 nm/RIU with an outstanding FOM of 11,570 at the first Fano resonance (FR1). In addition, the sensor shows a sensitivity to N2O of 194 nm/RIU accompanied by an FOM of 510 at the second Fano resonance (FR2). The structure reveals absorption losses of 6.3% for CO at the FR1, indicating the sensor selectivity to CO. The sensor is less selective at FR2 and limited to spectral shifts induced by each gas type. Our proposed design holds significant promise for the development of a highly sensitive double-sensing refractometric photonic integrated gas sensor.

An (AlN/GaN)N D (AlN/GaN)N Photonic Crystal-based Gas Sensor

Over the past few years, more studies have been conducted on the use of photonic crystals (PCs) in the detection field. Particularly fascinating for use as gas sensors are these materials’ outstanding spectrum sensitivity and small design. Using one-dimensional PCs as the theoretical foundation, this work aims to develop and analyze a nanoscale system that can identify the concentration of gases in ambient air and differentiate it from contaminated air. The intended structure is composed of layers of gallium nitride (GaN) and aluminum nitride (AlN) that alternate. In between these layers is a defective layer cavity that is filled with polluted air, which has a refractive index that is quite similar to pure air. The transfer matrix method (TMM) was used to perform numerical results for the proposed sensor. This sensor achieves average sensitivity of 1791 nm/RIU, average quality factor and figure of merit (FoM) of 1833 and 2287, respectively. We therefore think that the suggested detector’s design offers a strong candidate for accurate and efficient detection.

Fabrication of Spherical Colloidal Supraparticles via Membrane Emulsification.

Colloidal supraparticles are micrometer-scale assemblies of primary particles. These supraparticles have potential application in photonic materials, catalysis, gas adsorption, and drug delivery. Thus, the synthesis of colloidal supraparticles with a narrow size distribution and high yield has become essential. Here, we demonstrate membrane emulsification as a high-throughput approach for fabricating spherical supraparticles with a narrow size distribution and control over particle size and crystallinity. Spherical supraparticles with well-ordered surface structures are synthesized by generating emulsion droplets of an aqueous colloidal dispersion in fluorocarbon oil using a Shirasu porous glass membrane followed by the consolidation of particles through water removal within the emulsion. We systematically investigate process parameters, including the flow rate of the particle dispersion, the particle concentration, and the average pore diameter of the membrane, on the mean size and size distribution of the supraparticles, revealing key factors governing supraparticle properties and production throughput. A comparative evaluation with commonly employed methods highlights the advantage of membrane emulsification, which combines well-defined internal structure and controlled supraparticle sizes with comparably high yields on the order of tens of grams per day. Importantly, in contrast to widely used droplet-based microfluidics, membrane emulsification allows fabrication of supraparticles in nonfluorinated oil. Overall, membrane emulsification offers a simple yet versatile method for fabricating colloidal supraparticles with high quality and yield and may serve as a bridge between existing high-precision techniques, such as droplet-based microfluidics, and high-throughput processes with less control, such as spray-drying.

Integrated Photonic Sensors for the Detection of Toxic Gasses—A Review

Gas sensing is crucial for detecting hazardous gasses in industrial environments, ensuring safety and preventing accidents. Additionally, it plays a vital role in environmental monitoring and control, helping to mitigate pollution and protect public health. Integrated photonic gas sensors are important due to their high sensitivity, rapid response time, and compact size, enabling precise recognition of gas concentrations in real-time. These sensors leverage photonic technologies, such as waveguides and resonators, to enhance performance over traditional gas sensors. Advancements in materials and fabrication techniques could further improve their efficiency, making them invaluable for environmental monitoring, industrial safety, and healthcare diagnostics. In this review, we delved into photonic gas sensors that operate based on the principles of evanescent field absorption (EFA) and wavelength interrogation methods. These advanced sensing mechanisms allow for highly sensitive and selective gas detection, leveraging the interplay of light with gas molecules to produce precise measurements.

Three-dimensional photonic crystal optical gas sensor for trace detection and ultrafast response of chemical warfare agent in atmospheric humidity

Chemical warfare agents (CWAs) are toxic that pose a threat to the environment and human health, even trace amounts of CWAs can be fatal. In view of this, there is an urgent need to develop gas sensors for trace detection and ultrafast response of CWAs. Herein, an optical gas sensor has been proposed based on metal−organic frameworks (MOFs) three−dimensional (3D) photonic crystal to detect trace CWAs’ simulant (dimethyl methylphosphonate, DMMP) in different atmospheric humidity (RH 20 %, RH 40 %, RH 60 %, RH 80 %). At relative humidity (RH) of 20 %, the sensor shows excellent selectivity of DMMP due to the specific interactions of van der Waals force between UiO−67 and phosphoryl oxygen (OP) group of DMMP (C3H9O3P), the ultrahigh sensitivity (42.7 ppb), ultrafast response (0.5 s) are profit from the ordered superstructure of 3D photonic crystal and its complete photonic bandgap. At higher humidity (RH 40%–80 %), the sensor shows excellent stability, long–term repeatability, and it still keeps ultrahigh sensitivity (12.1 ppb), ultrafast response (0.49 s) for DMMP at RH 80 %. Moreover, an optical gas sensor array has been prepared to solve the problem of cross−sensitive between DMMP and other CWAs at highest humidity (RH ≥ 80 %), the average classification accuracy can reach 98.6 %.

Selective gas detection using phase change material infused photonic crystal

A photonic crystal-based optical gas detector is proposed, incorporating phase change material (PCM) to modulate the sensing properties. The multi-gas detection process is designed in the range of 650 nm to 2500 nm. Ge2Sb2Te5 (GST) is employed as a phase change material with significant optical property variations. It can exist in two self-sustaining, bi-stable phases: a crystalline GST (CGST) and an amorphous GST (AGST). The dielectrics (i.e., Si, SiO2, GST, and Au) are used in various combinations, such as Au-Si, Au-Si-SiO2, Au-GST-SiO2, and GST-Au. Plane light waves are used to model the nanoporous structures over a broad wavelength range (650 nm to 2500 nm). The optical spectral response of the structures, including the reflectivity spectrum, power absorption spectrum, and electric field distribution, is investigated by varying the GST thickness, dimension, and geometry of the nanoholes. Liquid ammonia has the highest selectivity of any gas from 650 nm to 1000 nm, at about 29%, whereas carbon monoxide has the maximum sensitivity of 32%. The interchanging of layers increases the sensitivity of all the gases. With a sensitivity and selectivity of 78% and 40%, respectively, carbon monoxide exhibits the greatest values.

Photonic crystal gas sensors based on metal-organic frameworks and polymers.

A photonic crystal (PC) is an optical microstructure with an adjustable dielectric constant. The PC sensor was deemed a powerful tool for gas molecule detection due to its excellent sensitivity, stability, online use and tailorable optical performance. The detection signals are generated by monitoring the changes of the photonic band gap when the sensing behavior occurs. Recently, many efforts have been devoted to improving the PC sensor's detection performance and reducing technical costs by selecting and refining functional materials. In this case, metal-organic frameworks (MOFs) with a large specific surface, tunable structural properties and polymers with unique swelling properties have attracted increasingly attention. In this review, a systematic review of PC gas sensors based on MOFs and polymers was carried out for the first time. Firstly, the optical properties and gas sensing mechanism of PCs were briefly summarized. Secondly, a detailed discussion of the structural properties and rapid preparation methods of distributed Bragg reflectors (DBRs), opals and inverse opals (IOPCs) was presented. Thirdly, the recent advances in MOF, polymer and MOF/polymer-based PC sensors over the past few years were summarized. It should be noted that the sensitivity and selectivity enhancement strategy by appropriate material species selection, organic ligand functionalization, metal-ion doping, diverse functional material arrays, and multi-component compounding were analyzed in detail. Finally, prospects on PC gas sensors are given in terms of preparation methods, material functionalization and future applications.

Slow-light-enhanced on-chip 1D and 2D photonic crystal waveguide gas sensing in near-IR with an ultrahigh interaction factor

Nanophotonic waveguides hold great promise to achieve chip-scale gas sensors. However, their performance is limited by a short light path and small light–analyte overlap. To address this challenge, silicon-based, slow-light-enhanced gas-sensing techniques offer a promising approach. In this study, we experimentally investigated the slow light characteristics and gas-sensing performance of 1D and 2D photonic crystal waveguides (PCWs) in the near-IR (NIR) region. The proposed 2D PCW exhibited a high group index of up to 114, albeit with a high propagation loss. The limit of detection (LoD) for acetylene (C2H2) was 277 parts per million (ppm) for a 1 mm waveguide length and an averaging time of 0.4 s. The 1D PCW shows greater application potential compared to the 2D PCW waveguide, with an interaction factor reaching up to 288%, a comparably low propagation loss of 10 dB/cm, and an LoD of 706 ppm at 0.4 s. The measured group indices of the 2D and 1D waveguides are 104 and 16, respectively, which agree well with the simulation results.

High Moisture-Barrier Performance of Double-Layer Graphene Enabled by Conformal and Clean Transfer.

Graphene films that can theoretically block almost all molecules have emerged as promising candidate materials for moisture barrier films in the applications of organic photonic devices and gas storage. However, the current barrier performance of graphene films does not reach the ideal value. Here, we reveal that the interlayer distance of the large-area stacked multilayer graphene is the key factor that suppresses water permeation. We show that by minimizing the gap between the two monolayers, the water vapor transmission rate of double-layer graphene can be as low as 5 × 10-3 g/(m2 d) over an A4-sized region. The high barrier performance was achieved by the absence of interfacial contamination and conformal contact between graphene layers during layer-by-layer transfer. Our work reveals the moisture permeation mechanism through graphene layers, and with this approach, we can tailor the interlayer coupling of manually stacked two-dimensional materials for new physics and applications.

Photonic bandgap fiber-based gas sensor with high sensitivity and high birefringence

Photonic bandgap fiber-based gas sensor with high sensitivity and high birefringence

Simultaneous Trapping of Two Optical Pulses in an Atomic Ensemble as Stationary Light Pulses.

The stationary light pulse (SLP) refers to a zero-group-velocity optical pulse in an atomic ensemble prepared by two counterpropagating driving fields. Despite the uniqueness of an optical pulse trapped within an atomic medium without a cavity, observations of SLP so far have been limited to trapping a single optical pulse due to the stringent SLP phase-matching condition, and this has severely hindered the development of SLP-based applications. In this Letter, we first show theoretically that the SLP process in fact supports two phase-matching conditions and we then utilize the result to experimentally demonstrate simultaneous SLP trapping of two optical pulses for the duration from 0.8 to 2.0 μs. The characteristic dissipation time, obtained by the release efficiency measurement from the SLP trapping state, is 1.22 μs, which corresponds to an effective Q factor of 2.9×10^{9}. Our Letter is expected to bring forth interesting SLP-based applications, such as, efficient photon-photon interaction, spatially multimode coherent quantum memory, creation of exotic photonic gas states, etc.

New hybrid photonic crystal fiber gas sensor with high sensitivity for ammonia gas detection

A new hybrid photonic crystal fiber (PCF) with circular rings based microstructure core gas sensor has been proposed for detecting ammonia gas at the wavelength of 1.544 μm. The finite element method has been used for numerical investigation. According to the results, the relative sensitivity is obtained as high as 70.25% at a wavelength of 1.544 μm. Furthermore, high birefringence and effective area are acquired by orders of 1.24 × 10−3 and 13.35 μm2, respectively. Finally, a low confinement loss of 1.202 × 10−1 dB/m is gained at the same wavelength. The absorption spectroscopy system can be used for detecting ammonia gas for experimental work. The theoretical results show that the proposed PCF still exhibits high relative sensitivity for a low concentration of ammonia gas at the wavelength of 1.544 μm, which makes the sensors detect gas precisely and can be used for medical and industrial applications.

Nonlocal Theory of the Photon Gas Evolution Beginning from the Planck Time

Evolution of the photon gas (PG) in the Planck period is considered as a particular case of the physical vacuum (PV) hydrodynamics. Nonlocal quantum hydrodynamic equations are applied for calculation of the photon gas evolution. In general case, PG hydrodynamics contains gravitation in the explicit form. Exact analytical solutions of PG hydrodynamics are obtained. Solutions show the exponential growth of gradient values for internal energy in time and space. In comparison with phenomenological General Relativistic Theory, Nonlocal quantum hydrodynamics (NQH) does not lead to contradictions in all limit cases. Theory of physical vacuum and the theory of photonic gas are related theories. These theoretical (analytical!) results confirm the result of direct observations (Arno Alan Penzias and Robert Woodrow Wilson, Nobel Prize (1978) for their discovery of cosmic microwave background; John C. Mather and George F. Smoot. Nobel Prize (2006) for their discovery of the blackbody form and anisotropy of the cosmic microwave background radiation).

Modified Bose-Einstein condensation in an optical quantum gas

Open quantum systems can be systematically controlled by making changes to their environment. A well-known example is the spontaneous radiative decay of an electronically excited emitter, such as an atom or a molecule, which is significantly influenced by the feedback from the emitter’s environment, for example, by the presence of reflecting surfaces. A prerequisite for a deliberate control of an open quantum system is to reveal the physical mechanisms that determine its state. Here, we investigate the Bose-Einstein condensation of a photonic Bose gas in an environment with controlled dissipation and feedback. Our measurements offer a highly systematic picture of Bose-Einstein condensation under non-equilibrium conditions. We show that by adjusting their frequency Bose-Einstein condensates naturally try to avoid particle loss and destructive interference in their environment. In this way our experiments reveal physical mechanisms involved in the formation of a Bose-Einstein condensate, which typically remain hidden when the system is close to thermal equilibrium.

Performance analysis of different slot waveguide structures for evanescent field based gas sensor applications

Slot waveguide has emerged as a potential candidate for the design of evanescent field absorption based photonic gas sensors, etc. In this paper, three different slot waveguide structures, i.e., conventional slot, partial-strip-loaded slot, and full-strip-loaded slot waveguides have been explored, to analyze their sensing performance for methane gas. In anticipation of improvement in evanescent field ratio in slot region, and hence, the sensing capabilities of the gas sensor, the slot waveguide structures have been designed by depositing the germanium layer over the calcium fluoride in different manners. Several waveguide parameters, such as evanescent field ratio, propagation loss, and sensitivity have been considered for the analysis and comparison of the presented slot waveguide structures, by varying the arm-width and thickness of germanium layer. Simulation results have demonstrated that the full-strip-loaded slot waveguide has the superior performance, in terms of higher evanescent field (28%), and higher sensitivity (73.76 L/Mol), which is closely followed by the partial-strip-loaded slot waveguide, for a target value of propagation loss (3 dB/cm). However, the conventional slot waveguide provides slightly larger optimum waveguide length (0.86 cm), as compared to other presented slot waveguides.

Photonic spin Hall effect and terahertz gas sensor via InSb-supported long-range surface plasmon resonance

The photonic spin Hall effect (SHE), featured by a spin-dependent transverse shift of left- and right-handed circularly polarized light, holds great potential for applications in optical sensors, precise metrology and nanophotonic devices. In this paper, we present the significant enhancement of photonic SHE in the terahertz range by considering the InSb-supported long-range surface plasmon resonance (LRSPR) effect. The influences of the InSb/ENZ layer thickness and temperature on the photonic SHE were investigated. With the optimal structural parameters and temperature, the maximal spin shift of the horizontal polarization light can reach up to 2.68 mm. Moreover, the spin shift is very sensitive to the refractive index change of gas, and thus a terahertz gas sensing device with a superior intensity sensitivity of 2.5 × 105 μm/RIU is proposed. These findings provide an effective method to enhance the photonic SHE in the terahertz range and therefore offer the opportunity for developing the terahertz optical sensors based on photonic SHE.

Theoretical Investigation of Broadband Frequency Conversion Bridging the Mid-Infrared and Telecom Band Through a Chalcogenide/Sio2 Hybrid Waveguide

Capturing the distinctive spectral fingerprints of molecules in the infrared (IR) region is of vital importance in gas detection. However, it is still limited by the resolution, sensitivity and signal to noise ratio of IR detectors. Here, a broadband frequency conversion scheme from the middle IR band (MIR) to the telecom band based on four-wave mixing process is proposed and theoretically investigated, combining the advantages of well-established detectors in the telecom band and unique molecular vibrations in the MIR band. A flat and low dispersion profile is generated in an asymmetric Ge-As-Se/SiO2 hybrid waveguide, which exhibits four zero-dispersion wavelengths and a dispersion variation of sub-20 ps/nm/km. Furthermore, taking advantage of the high order phase-matching, an ultra-broad 3-dB continuous wavelength conversion bandwidth covering 1454–4521 nm is achieved, which to the best of our knowledge is the widest frequency conversion bandwidth in the chip-scale devices. In addition, a fabrication scheme is proposed for the precise manipulation of dispersion. It holds great potential for practical applications in photonic integrated gas sensing, biomedical diagnostics.

Design and optimization of index guiding photonic crystal fiber-based gas sensor

Hydrogen sulfide(H2S) and methane(CH4) are flammable, toxic, and colorless gases that exist in oil rigs/refineries. The PCF based gas sensors can detect the concentration of chemical materials such as hydrogen sulfide and methane. This paper presents a hexagonal PCF for sensing these gases. Characteristics of the proposed structure have been investigated for the wavelength range of 1.1 μm–1.6 μm using the full vector finite element method (FEM). The numerical results show that using non-circular holes around the central ring holes and a higher number of ring holes improves sensitivity and confinement loss respectively. Eventually, the relative sensitivity is enhanced to 62.07% and 67.07% and also the confinement loss 2.33 × 10−9dB/m and 8.61 × 10−5dB/m at the wavelength of 1.33 μm and λ = 1.578 μm at which the CH4 and H2S have a strong absorption line, respectively.

A simple structure of PCF based sensor for sensing sulfur dioxide gas with high sensitivity and better birefringence

Abstract This paper describes a micro-cored photonic crystal fiber-based gas sensor that uses a simple structure and proper analysis has done to detect sulfur dioxide gas. SO2 is a significant air pollutant that may aggravate existing respiratory and cardiovascular diseases. The numerical investigation has been done in a range of wavelengths from 0.9 ​μm to 1.1 ​μm and as usual, the proposed structure is numerically analyzed by using the complete finite element method. A Perfectly Matched Layer (PML) is used to investigate the optical parameters. We tested the performance of the designed PCFs for sensing sulfur dioxide as a gas sample. We designed the core section of the proposed structure with only a circular shape hole to minimize design complexity. The relative sensitivity can be increased by changing the diameter of the air holes in the microstructure core, cladding holes even the thickness of the PML. The proposed sensor's test is carried out on different Pitch values, PML thickness values, core region's hole diameter variations, cladding hole diameter variations. At fixed wavelength of 1 ​μm, the maximum relative sensitivity obtained here is around 70% with a better birefringence value 1.0 ​× ​10−03 and lower confinement loss.

Hollow-Core Photonic Crystal Fiber Gas Sensing.

Fiber gas sensing techniques have been applied for a wide range of industrial applications. In this paper, the basic fiber gas sensing principles and the development of different fibers have been introduced. In various specialty fibers, hollow-core photonic crystal fibers (HC-PCFs) can overcome the fundamental limits of solid fibers and have attracted intense interest recently. Here, we focus on the review of HC-PCF gas sensing, including the light-guiding mechanisms of HC-PCFs, various sensing configurations, microfabrication approaches, and recent research advances including the mid-infrared gas sensors via hollow core anti-resonant fibers. This review gives a detailed and deep understanding of HC-PCF gas sensors and will promote more practical applications of HC-PCFs in the near future.