Fabry-Perot Interference Research Articles

Optical-thermally actuated graphene mechanical resonator for humidity sensing

This paper demonstrates an optical-thermally actuated multi-layer graphene resonator for humidity sensing. A ∼10-layered graphene resonator with a diameter of 125 µm peripherally clamped on the fiber ferrule end face was actuated to vibrate using the intensity-modulated laser, and the vibration was detected based on the optical fiber Fabry-Perot interference method. The humidity sensing experiment exhibited an up to 350 Hz/%RH humidity sensitivity in the range of 0–100 % RH at 25 °C, which was 10 times higher than those of the previously reported Quartz Crystal Microbalance (QCM)-based humidity sensors. Also, a good repeatability of the frequency-humidity response was observed for the presented graphene resonator. Moreover, in view of the coupling effect of temperature on the graphene resonator, the temperature drift of 0.942 kHz/°C was measured in the range of 25–50 °C, thereby inducing an absolute humidity error of about 0.6 g/(m3·°C).

Ultrafast light emission at telecom wavelengths from a wafer-scale monolayer graphene enabled by Fabry-Perot interferences.

Ultrafast light emission from monolayer graphene shows attractive potential for developing integrated light sources for next-generation graphene-based electronic-photonic integrated circuits. In particular, graphene light sources operating at the telecom wavelengths are highly desired for the implementation of graphene-based ultrahigh-speed optical communication. Currently, most of the studies on ultrafast light emission from graphene have been performed in the visible spectrum, while studies on ultrafast emission at the telecom wavelengths remain scarce. Here, we present experimental observations of strong ultrafast thermal emission at telecom wavelengths from wafer-scale monolayer graphene. Our results show that the emission spectra can be strongly modified by the presence of the cavity effect to produce an enhanced emission at telecom wavelengths. We corroborate our experimental results with simulations and show that by designing a suitable cavity thickness, one can easily tune the emission profile from visible to telecom wavelength regardless of the pump power. In addition, we demonstrate that the insertion of a monolayer of hexagonal boron nitride between graphene and the substrate helps improve the thermal stability of graphene, thereby providing more than five times enhancement of the ultrafast thermal emission. Our results provide a potential solution for stable on-chip nanoscale light sources with ultrahigh speed modulation.

High sensitivity fiber optic acceleration sensor based on Fabry-Perot interferometer

• This paper proposes a high sensitivity fiber optic acceleration sensor based on Fabry-Perot interference. • The sensitivity of the sensor is 3.81 nm/g at 300 Hz, and the resonance frequency of the sensor is 800 Hz. • The sensor has a simple structure, low cost and easy to fabricate. A high sensitivity fiber optic acceleration sensor based on Fabry-Perot interferometer is proposed and experimentally demonstrated. The proposed sensor is composed of a sensor pedestal, a mass block, elastic diaphragm and two reflectors, wherein the collimating reflector 1 and the reflector 2 constitute a fiber Fabry-Perot (F-P) interference cavity. By analyzing the relevant parameters of F-P interference theory, we modulate the F-P reflection spectrum with high finesse, and demodulate the F-P reflection spectrum by wavelength demodulation method to obtain the acceleration signal. Through simulation analysis and experimental verification, the resonant frequency, sensitivity and lateral anti-interference ability of the sensor have been investigated. The experimental results show that the resonant frequency of the sensor is 800 Hz, the sensitivity is 3.81 nm/g when the frequency is 300 Hz, the resolution is 0.263 mg, and the lateral anti-interference degree is less than 5 %. Furthermore, the proposed acceleration sensor exhibits the advantages of simple structure and low cost, and has great application prospects in the vibration monitoring of the pitch bearing of wind power generation.

A temperature-compensated force sensor based on a cascaded FPI for needle force sensing

In order to solve problems of puncture force sensing error and delay caused by the change of temperature, a cascaded Fabry–Perot interference (FPI) sensing structure consisting of an air cavity and a silica cavity was proposed, and force–temperature dual-parameter sensing and decoupling models were established. The puncture experiments of hard silica gel and soft silica gel at room temperature show that the cascaded FPI has high force resolution and can effectively perceive the small changes of cutting force during the puncture process. The puncture experiment of hard silica gel after increasing the temperature shows that the cascaded FPI can simultaneously measure the cutting force and temperature at the tip of a flexible needle, and effectively eliminate the pseudo-force caused by temperature during the puncture process.

High-Sensitivity Fiber-Optic Low-Frequency Acoustic Detector Based on Cross-Correlation Demodulation

Fiber-optic acoustic sensors based on Fabry-Perot (F-P) interference structure have advantages of compact structure, high sensitivity, convenience to manufacture and immunity to electromagnetic interference. To simplify the demodulation system of the fiber-optic F-P sensor and reduce the demodulation cost, a low-frequency acoustic detector based on the principle of optical cross-correlation (OCC) demodulation is proposed. A fiber-optic F-P interference sensor based on the phenylene sulfide (PPS) diaphragm is used as a low-frequency acoustic detection unit. The OCC demodulation system of the F-P acoustic sensors mainly includes a superluminescent diode (SLED), a flat glass wafer and single-mode fibers. The flat glass wafer is used as the static correlation reference cavity of the PPS diaphragm-based F-P acoustic sensor. The experimental results show that the detector is responsive to low-frequency acoustic waves from below 20 Hz to 250 Hz. For the acoustic waves with a frequency of 20 Hz, the minimum detection limit (MDL) of sound pressure is 0.65 mPa. The detector has the potential for low-cost and high-sensitivity acoustic detection for applications such as infrasonic detection and photoacoustic gas detection.

Simultaneous measurement of salinity and temperature based on Fabry-Perot interference and anti-resonance effect

In this work, we demonstrate a novel cascaded fiber-optic structure depending on Fabry-Perot interference and anti-resonance (AR) effect for seawater salinity and temperature simultaneous measurement. An in-fiber microchannel Fabry-Perot interferometer (FPI) is obtained in a single-mode fiber (SMF) by using femtosecond laser radiation and hydrofluoric acid corrosion, which is filled with thermosensitive polymer and able to measure the temperature. A section of hollow-core fiber (HCF) is fused between the SMFs with the square micro-slots ablated on the ends, and the liquid can easily flow into the HCF. To our knowledge, this is the first time that the capillary-type HCF was used as a microfluidic device to measure seawater salinity. Through model analysis and experimental tests, it is confirmed that the proposed sensor can simultaneously measure the salinity and temperature, the corresponding minimum detectable resolutions reach 0.0008‰ and 0.001 ℃, respectively. The performance tests show that the sensor has accurate measurement results, good stability, and repeatability. Besides, the proposed HCF-based internal liquid analysis structure is a promising approach for highly reliable and ultrasensitive biochemical sensing.

Active Fano resonance switch using dual-layer graphene in an embedded dielectric metasurface.

We propose an active optical Fano switch (OFS) based on an embedded dielectric metasurface (EDM) including dual-layer graphene (DLG). An EDM is a dielectric grating overlapped by two cladding layers, and it excites a Fano resonance. DLG is positioned inside the upper cladding layer to maximize light-graphene interaction. Thus, with a small change of the chemical potential (µc) of graphene, a resonance wavelength is tuned to switch the OFS on and off. First, a red-parity asymmetric Fano resonance is realized, and a sharp asymmetric lineshape is achieved by controlling the structural parameters of the EDM and the interaction between the Fano resonance and additional weak Fabry-Perot interference for efficient switching. The distance of a peak-to-dip wavelength (Δλp-d) and the change of chemical potential (Δµc) for switching is analyzed by varying the duty cycle (DC) and grating thickness (tg) of the EDM. Furthermore, switching contrast as a figure of merit (FoM) is analyzed. With DC of 0.5 and tg of 70 nm, the OFS requires Δλp-d of 7.3 nm and Δµc of 0.25 eV. The FoM of 0.97 is achieved. By adjusting the two parameters, the switching condition is tuned. In the case of a blue parity, the effect of the two parameters exhibits a similar trend to that of the red parity. The FoM, however, is lower due to the reversed parity.

Highly Sensitive Air Pressure Sensor Based on Fabry-Perot Interference

A highly sensitive optical fiber air pressure sensor based on Fabry–Perot interferometer is proposed and demonstrated. The sensor is fabricated by flat-cut single-mode optical fiber, capillary glass tube, stainless steel sleeve, nylon substrate, and metal aluminum film. The finite element simulation was performed in two steps using the COMSOL Multiphysics software. In the first step, the structural mechanics module is used to simulate the deformation of the membrane under a fixed pressure, so as to obtain the corresponding sensor cavity lengths under different pressure. In the second step, the wave optics module is used to get the reflection spectrum of the sensor under different cavity lengths. Then the linear relationship between the reflection spectral shift of the sensor and the pressure is obtained. Thus, the average spectral sensitivity of the sensor under air pressure is −3.10335 nm/KPa. A metal-aluminum thin film F-P cavity sensor was fabricated for experimental verification. According to the experimental results, when the air pressure ranges from 0 Pa to 1000 Pa, the spectral sensitivity of the sensor is as high as −3.10 nm/KPa. This is almost consistent with the simulation result. The sensor has exhibited potential application in the fields of measurement of airway pressure and environmental monitoring.

Fabry-Perot Interference Fiber Acoustic Wave Sensor Based on Laser Welding All-Silica Glass

Due to the small difference between the thermal expansion coefficients of silica optical fiber and silica glass, they are used as probe materials of optical fiber acoustic wave sensors. According to the light absorption characteristics of a pressure-sensitive silica diaphragm and silica glass, the laser welding of an all-silica Fabry–Perot (FP) interference optical fiber acoustic wave sensor with a CO2 laser is proposed. For understanding the influence of thermal expansion of sealing air in an FP cavity and the drift of interference-intensity demodulation working point of a FP interference acoustic wave sensor, we designed a process for the laser welding of an ultra-thin silica diaphragm and sleeve and optical fiber and sleeve. The exhaust hole of the FP cavity is reserved in the preparation process, and an amplified spontaneous emission light source and a tunable optical-fiber FP filter are introduced to stabilize the working point. The sensor is tested with a 40 kHz sound vibration signal. The results show that the sound pressure sensitivity of the sensor to an acoustic source of 0.02–0.1 W/cm2 is 6.59 mV/kPa. The linearity coefficient is 0.99975, indicating good linearity.

A Compact Fiber Cascaded Structure Incorporating Hollow Core Fiber With Large Inner Diameter for Simultaneous Measurement of Curvature and Temperature

A compact fiber cascaded structure for simultaneous measurement of curvature and temperature based on Fabry-Perot (FP) interference and anti-resonant (AR) mechanism is designed and experimentally demonstrated. The proposed structure is manufactured by sandwiching a segment of hollow core fiber (HCF) with large inner diameter and suitable length between two segments of single mode fibers (SMFs). Three sample sensors were fabricated with different HCF lengths. With theoretical analysis and experimental verifications, an HCF length of 1197 <i>&#x03BC;</i>m was selected for curvature and temperature experiments. The reflection fringes based on FP interference and transmission envelopes based on AR mechanism can be monitored to measure curvature and temperature variations at the same time. From experimental results, the sensitivities of curvature based on AR mechanism and FP interference are 0.2345 nm&#x002F;m^&#x2212;1 and -0.1021 nm&#x002F;m^&#x2212;1, and those of sensitivities of temperature are 0.0172 nm&#x002F;&#x00B0;C and 0.0017 nm&#x002F;&#x00B0;C, respectively. Therefore, the different responses in curvature and temperature based on two mechanisms enable the proposed structure to simultaneously measure curvature and temperature.

2.4 ng/√Hz low-noise fiber-optic MEMS seismic accelerometer.

This paper introduces a fiber-optic microelectromechanical system (MEMS) seismic-grade accelerometer that is fabricated by bulk silicon processing using photoresist/silicon dioxide composite masking technology. The proposed sensor is a silicon flexure accelerometer whose displacement transduction system employs a light intensity detection method based on Fabry-Perot interference (FPI). The FPI cavity is formed between the end surface of the cleaved optical fiber and the gold-surfaced sidewall of the proof mass. The proposed MEMS accelerometer is fabricated by one-step silicon deep reactive ion etching with different depths using the composite mask, among which photoresist is used as the etching-defining mask for patterning the etching area while silicon dioxide is used as the depth-defining mask. Noise evaluation experiment results reveal that the overall noise floor of the fiber-optic MEMS accelerometer is 2.4 ng/H z at 10 Hz with a sensitivity of 3165 V/g, which is lower than that of most reported micromachined optical accelerometers, and the displacement noise floor of the optical displacement transduction system is 208 fm/H z at 10 Hz. Therefore, the proposed MEMS accelerometer is promising for use in high-performance seismic exploration applications.

Phase Demodulation Methods for Optical Fiber Vibration Sensing System: A Review

In recent years, phase demodulation methods for optical fiber vibration sensors (OFVS) have attracted more and more attention, aiming to accurately detect vibration signals. The principles of phase modulation and demodulation in OFVS are firstly introduced. Then, three classical phase demodulation methods are described, including phase generated carrier (PGC) demodulation method, <inline-formula> <tex-math notation="LaTeX">${3}\,\,\times \,\,{3}$ </tex-math></inline-formula> coupler demodulation method, and in-phase and quadrature (IQ) demodulation method. Furthermore, the state of art of phase demodulation methods in various OFVS are reviewed. As the results of analysis, different structures of OFVS need appropriate demodulation methods for vibration detection. The Fourier transform method, fringe counting method and PGC demodulation method have strong applicability for Fabry-Perot interference OFVS. The scalability of interferometers provides convenience for PGC demodulation method and <inline-formula> <tex-math notation="LaTeX">${3}\,\,\times \,\,{3}$ </tex-math></inline-formula> coupler demodulation method in the OFVS with composite structure. PGC demodulation method, <inline-formula> <tex-math notation="LaTeX">${3}\,\,\times \,\,{3}$ </tex-math></inline-formula> coupler demodulation method and quadrature demodulation method are good choices for dynamic sensing in FBG-OFVS. The IQ demodulation method is a popular choice for phase sensitive optical time domain reflectometry at present. This paper provides a reference for the OFVS to realize vibration detection with appropriate phase demodulation method.

Integration of Highly Luminescent Lead Halide Perovskite Nanocrystals on Transparent Lead Halide Nanowire Waveguides through Morphological Transformation and Spontaneous Growth in Water.

The integration of highly luminescent CsPbBr3 quantum dots on nanowire waveguides has enormous potential applications in nanophotonics, optical sensing, and quantum communications. On the other hand, CsPb2 Br5 nanowires have also attracted a lot of attention due to their unique water stability and controversial luminescent property. Here, the growth of CsPbBr3 nanocrystals on CsPb2 Br5 nanowires is reported first by simply immersing CsPbBr3 powder into pure water, CsPbBr3- γ Xγ (X = Cl, I) nanocrystals on CsPb2 Br5 -γ Xγ nanowires are then synthesized for tunable light sources. Systematic structure and morphology studies, including in situ monitoring, reveal that CsPbBr3 powder is first converted to CsPb2 Br5 microplatelets in water, followed by morphological transformation from CsPb2 Br5 microplatelets to nanowires, which is a kinetic dissolution-recrystallization process controlled by electrolytic dissociation and supersaturation of CsPb2 Br5 . CsPbBr3 nanocrystals are spontaneously formed on CsPb2 Br5 nanowires when nanowires are collected from the aqueous solution. Raman spectroscopy, combined photoluminescence, and SEM imaging confirm that the bright emission originates from CsPbBr3 -γ Xγ nanocrystals while CsPb2 Br5 -γ Xγ nanowires are transparent waveguides. The intimate integration of nanoscale light sources with a nanowire waveguide is demonstrated through the observation of the wave guiding of light from nanocrystals and Fabry-Perot interference modes of the nanowire cavity.

Simultaneous Measurement of Salinity and Temperature Based on Fabry-Perot Interference and Anti-Resonance Effectsimultaneous Measurement of Salinity and Temperature Based on Fabry-Perot Interference and Anti-Resonance Effect

Simultaneous Measurement of Salinity and Temperature Based on Fabry-Perot Interference and Anti-Resonance Effectsimultaneous Measurement of Salinity and Temperature Based on Fabry-Perot Interference and Anti-Resonance Effect

Fabry-Perot interference pattern scattered by a sub-monolayer array of nanoparticles

Understanding scattering of visible and infrared photons from nanomaterials and nanostructured materials is increasingly important for imaging, thermal management, and detection, and has implications for other parts of the electromagnetic spectrum (e.g., x-ray scattering and radar). New, interesting reports of photon scattering as a diagnostic probe, from inelastic x-ray scattering and interference to ‘nano-FTIR’ microscopy using infrared photons, have been published and are under active investigation in laboratories around the world. Here, we report, for the first time to our best knowledge, the experimental discovery of a Fabry–Perot interference pattern that is scattered by the sub-monolayer array of plasmonic Ag nanoparticles, and confirm it analytically and with rigorous numerical FDTD simulations.

A High Precision Fiber Optic Fabry–Perot Pressure Sensor Based on AB Epoxy Adhesive Film

This paper proposes a Fabry–Perot pressure sensor based on AB epoxy adhesive with ultra-high sensitivity under low pressure. Fabry–Perot interference, located between single-mode fiber (SMF) and hollow-core fiber (HCF), is an ultra-thin AB epoxy film formed by capillary action. Then the thick HCF was used to fix the HCF and SMF at both ends with AB epoxy adhesive. Experimental results show that when the thickness of AB epoxy film is 8.74 μm, and the cavity length is 30 μm, the sensor has the highest sensitivity. The sensitivity is 257.79 nm/MPa within the pressure range of 0–70 kPa. It also investigated the influence of the curing time of AB epoxy on the interference spectrum. Experiments showed that the interference spectrum peak is blue-shifted with the increase of curing time. Our study also demonstrated the humidity stability of this pressure sensor. These characteristics mean that our sensor has potential applications in the biomedical field and ocean exploration.

Plug-in label-free optical fiber DNA hybridization sensor based on C-type fiber Vernier effect

A reflective Fabry-Perot interference (FPI) label-free biosensor based on Vernier effect is designed and implemented for in situ real-time DNA hybridization detection. The sensor is made by splicing single-mode fiber (SMF), a segment of C-type fiber and SMF. The Vernier effect occurs between the solid cavity FPI and the air cavity FPI. In our experiment, a high sensitivity of 10791.12 nm/RIU is obtained in the refractive index (RI) range of 1.3311–1.3450. On this basis, we immobilized probe DNA (pDNA) on the surface of SMF to detect the complementary DNA (cDNA), demonstrating use for label-free sensing of DNA hybridization. The experimental results show that the sensor can detect 1 µM cDNA with high specificity. The paper demonstrates the first research of optical fiber DNA biosensor based on the open microcavity FPI Vernier effect. In addition, the sensor has the advantages of high sensitivity, strong stability, simple structure and simple fabrication. It can also be applied to other biomolecule detection based on probe-target biological binding events, which has great application potential in medical diagnostics, food science, genetic engineering and other biological fields.

Fabry-Perot interference and piezo-phototronic effect enhanced flexible MoS2 photodetector

Fabry-Perot interference and piezo-phototronic effect enhanced flexible MoS2 photodetector

Characterization of In(Ga,Al)As/GaAs metamorphic heterostructures for mid-IR emitters by FTIR photoreflectance spectroscopy

Infrared photoreflectance (PR) spectra of In(Ga,Al)As/GaAs metamorphic heterostructures have been obtained using a novel photomodulation FTIR spectroscopy technique. An analysis of the PR spectra features allowed us to estimate the critical point energies corresponding to the direct interband transitions in various regions of the In(Ga,Al)As heterostructures, and distinguish the PR signals originating from Fabry-Perot interference. Observation of Franz-Keldysh oscillations originating from the InAlAs virtual substrate and an InGaAs waveguide layer has enabled determination of the built-in electric field intensities within the heterostructures. The obtained results open up possibilities for contactless control of free carrier concentration in In(Ga,Al)As/GaAs metamorphic heterostructures developed for growth of emitters of mid-IR spectral range.

Characteristics of rising temperatures through laser irradiation using a temperature sensor integrated optical fiber probe for soft tissue ablation

A new structure composed of silica optical fibers for soft tissue ablation is proposed and fabricated in this study. Laser irradiation and temperature monitoring are simultaneously performed using a wavelength-division multiplexing technique with a single optical fiber probe. A 1.55-μm wavelength range light is used for temperature measurement. The fabricated Fabry–Perot interference temperature sensor comprising a glass capillary and a graded-index multimode fiber exhibits good temperature sensor characteristics. The probe end is terminated with a glass capillary having a declined glass cap. This portion suppresses the reflected light backward to the incident fibers. Because the reflected light at this portion does not affect the interference of internal reflected light, regardless of the outer medium, stable temperature measurement is confirmed. A 1.48-μm laser irradiation method is investigated as a thermal source for soft tissue ablation. The characteristics of rising temperatures through laser irradiation of chicken-breast meat are investigated and indicate sufficient temperature increases for thermal ablation of soft tissue. A good estimation of the thermal protein denaturation region is achieved through a simple analytical equation using the measured value at the fiber tip temperature sensor.