Fiber Resonator Research Articles

Cavity soliton in a cyclic polarization permutation fiber resonator.

Cavity solitons are shape-preserving waveforms infinitely revolving around a cavity, which have numerous applications from spectroscopy to telecommunications. Although the cavity solitons have been widely studied for their special time-frequency characteristics over the past decade, the spectral flatness will be a large limitation in some applications without any extra filtering process. In this paper, we report on the generation of a distinct cavity soliton in a cyclic polarization permutation fiber resonator. With the simultaneous excitation of two orthogonal polarization modes with equally opposite dispersion, vectorial cavity solitons possessing broader and flatter spectra can be generated. In order to verify the concept, a numerical model of the polarization-maintaining fiber is proposed and the soliton with a flattened spectrum can be formed. The results enrich the soliton dynamics in the vectorial dissipation system.

Quantifiable Effect of Interparticle Plasmonic Coupling on Sensitivity and Tuning Range for Wavelength-Mode LSPR Fiber Sensor Fabricated by Simple Immobilization Method

Herein a gold nanosphere (AuNS)-coated wavelength-mode localized surface plasmon resonance (LSPR) fiber sensor was fabricated by a simple and time-saving electrostatic self-assembly method using poly(allylamine hydrochloride). Based on the localized enhanced coupling effect between AuNSs, the LSPR spectrums of the AuNS monolayer with good dispersity and high density exhibited a favourable capability for refractive index (RI) measurement. Based on the results obtained from the optimization for AuNS distribution, sensing length, and RI range, the best RI sensitivity of the fiber modified by 100 nm AuNS reached up to about 2975 nm/RIU, with the surrounding RI range from 1.3322 to 1.3664. Using an 80 nm AuNS-modified fiber sensor, the RI sensitivity of 3953 nm/RIU was achieved, with the RI range increased from 1.3744 to 1.3911. The effect of sensing length to RI sensitivity was proven to be negligible. Furthermore, the linear relationship between the RI sensitivity and plasma resonance frequency of the bulk metal, which was dependent on the interparticle plasmon coupling effect, was quantified. Additionally, the resonance peak was tuned from 539.18 nm to 820.48 nm by different sizes of AuNSs-coated fiber sensors at a RI of 1.3322, which means the spectrum was extended from VIS to NIR. It has enormous potential in hypersensitive biochemistry detection at VIS and NIR ranges.

Real-Time Detection of Circulating Tumor Cells in Bloodstream Using Plasmonic Fiber Sensors.

Circulating tumor cells (CTCs) are single cancer cells or cancer cell clusters that are present in the circulatory system. Assessing CTC levels in patients can aid in the early detection of cancer metastasis and is essential for the purposes of accurate cancer prognosis. However, current in vitro blood tests are limited by the insufficient blood samples and low concentration levels of CTCs, which presents a major challenge for practical biosensing devices. In this work, we propose the first surface plasmon resonance (SPR) fiber probe to work intravenously, which offers a real-time detection of CTCs in bloodstreams. By exposing the protein-functionalized fiber probe to circulating blood, a continuous capture of CTCs ensures a constant increase in enrichment and hence greatly enhances enumeration accuracy. The performance of our plasmonic fiber probe was demonstrated to specifically detect Michigan Cancer Foundation-7 (MCF-7) breast cancer cells in flowing whole mouse blood. Further, a detection limit of ~1.4 cells per microliter was achieved by using an epithelial cell adhesion molecule (EpCAM) antibody-based receptor layer and a 15 minute enrichment period. This pilot study validates real-time CTC detection directly in the bloodstream by using plasmonic fiber probes, which exhibit promising clinical potential for in vivo diagnostic tests involving low concentration biomarkers in circulating blood.

Recent Advancements in Resonant Fiber Optic Gyro—A Review

The fiber optic gyro (FOG), which is currently one of the most widely used fiber optic sensors, has firmly occupied a considerable market share of inertial sensors and offers the benefits of high stability and easy integration. The resonant FOG, also known as the RFOG, is a sensor that identifies a rotation rate by employing the use of a fiber ring resonator. It possesses a higher application potential in terms of optical stability and system miniaturization because it is an FOG of the second generation. This review begins with an exploration of the RFOG principle and then moves on to concentrate on the two aspects of RFOG optical noises suppression and signal processing in order to examine the progression of RFOG in the most recent years. Several distinct types of RFOG schemes that have a high application potential are dissected individually; these are the types of schemes that are anticipated to become mainstream application schemes in the not-too-distant future. In the end, the prospect and research challenge of RFOG are presented to help researchers clarify research directions. This article presents an in-depth analysis of the current state of research regarding RFOG-related technologies and offers a forecast regarding the path that the inertial sensor will take in the foreseeable future.

Simulation and optimization of spectral parameters of resonant optical gyroscope

As a new inertial navigation device, the resonant optical gyroscope offers advantages that include high precision, device integration, impact resistance, and solid-state realization. This device will be widely used in future military and civil applications. Following consideration of the factors that affect accuracy improvement of resonant fiber optic gyroscopes, the relationships among the insertion loss, coupling coefficient, and unit length loss of the cavity fiber and the resonance depth, full width at half maximum, and fineness of the transmission spectrum line are analyzed. To improve the transmission spectrum’s resonance depth, the coupling coefficient should be controlled at 0.2 and the optical coupler insertion loss should be reduced as far as possible. Additionally, the laser linewidth effects on the transmission spectrum and the limit sensitivity are analyzed. It is found that if the laser linewidth of the resonant optical gyroscope is less than 100 kHz, it can meet the resonance depth requirements, thus, providing a technical reference for further research into integrated optical waveguide gyroscopes.

Hyperbolic-Metamaterials-Based SPR Temperature Sensor Enhanced by a Nanodiamond-PDMS Hybrid for High Sensitivity and Fast Response.

A high-performance surface plasmon resonance (SPR) fiber sensor is proposed with hyperbolic metamaterials (HMMs), nanodiamonds (NDs), and polydimethylsiloxane (PDMS) to enhance the temperature sensitivity and response time. The HMM with tunable dispersion can break through the structural limitations of the optical fiber to improve the refractive index (RI) sensitivity, while NDs and PDMS with large thermo-optic coefficients enable to induce significant RI change under varied thermal fields. The ternary composite endows the sensor with a high temperature sensitivity of -9.021 nm/°C, which is 28.6 times higher than that of the conventional gold film-based SPR sensor. Furthermore, NDs with high thermal conductivity (2200 W/mK) effectively expedite the thermal response of PDMS, which reduces the response time from 80 to 6 s. It is believed that the proposed sensors with high sensitivity, fast response time, and compact size have great potential for applications in industrial production, healthcare, environmental monitoring, etc.

Simultaneous measurements of refractive index and temperature based on a no-core fiber coated with Ag and PDMS films

A compact surface plasmon resonance (SPR) fiber optic sensor, being utilized to simultaneously measure refractive index (RI) and temperature, is proposed and experimentally demonstrated in this paper. One part of a no-core fiber (NCF) was coated with a silver (Ag) film, and the other part was coated with a silver/polydimethylsiloxane (Ag/PDMS) composite film to stimulate the SPR effect. Due to the two heterogeneous films, two dips appeared in the transmission spectrum and were used to achieve the dual-parameter measurements. The experimental results showed that the RI sensitivity reached 2121.43 nm/RIU and 0 nm/RIU, while the temperature sensitivity reached –0.32 nm/°C and –2.21 nm/°C for the two dips, respectively. Based on the obtained transfer matrix, the measurements of RI and temperature could be demodulated. This designed sensor showed the merits of simple structure, easy to implement, and high sensitivity, demonstrating application prospects in dual-parameter monitoring.

Plasmonic fiber optic biosensors with barium titanate and titanium dioxide thin films

In this paper, two structures of surface plasmon resonance fiber optic biosensors with the addition of a thin layer of titanium dioxide and barium titanate are introduced and studied comparatively. The sensitivity of these biosensors has been calculated using the transfer matrix method. Adding a thin layer of barium titanate and titanium dioxide after the gold layer, both make increase the sensitivity of the biosensor due to the transfer of free charge between the gold and the dielectric. The obtained results of the comparative study show that the titanium dioxide layer can be a suitable alternative to barium titanate for further increase of the sensitivity of the fiber optic surface plasmon resonance biosensor.

Monolithic highly multi-mode XLMA-fiber resonator for high power operation.

Highly multi-mode fiber resonators can be an excellent solution to achieve high output power with homogeneous beam profiles, while nonlinear effects are suppressed due to the high number of modes and high mode-field areas. While highly reflective fiber-Bragg-gratings (HR-FBGs) are a well-developed technology in single-mode fibers, in multi-mode fibers HR-FBGs are under investigation to enable monolithic resonators. Here, we present a monolithic multi-mode fiber resonator in a > 50 µm core diameter XLMA-fiber. We achieve a slope efficiency of up to 50%, stable wavelength operation at 1074 nm and homogeneous beam profiles using an HR-FBG with app. 70% reflectivity.

Sea‐Urchin‐MnO2 for Broadband Optical Modulator

AbstractManganese dioxide (MnO2) is considered to be one of the nanomaterials with enormous value in research and application because of its high theoretical specific capacitance, large specific surface area and porosity, excellent electron transfer ability, and excellent light absorption ability. However, exploring superior nonlinear absorption of MnO2 in the broadband spectrum is still the key challenge to harvesting their greatest potential. In this paper, the optical modulator based on MnO2 is fabricated, and its nonlinear optical performance is measured. The results indicate that the modulation depth is 4.4% and the saturable intensity is 32.8 MW cm−2 at 1.5 µm region. What's more fascinating is that the modulator based on MnO2 is integrated into Er‐doped and Tm‐doped fiber resonators to successfully demonstrate its broadband mode‐locking operations. The coexistence of harmonic bound state pulse and conventional soliton pulse, as well as dual‐wavelength solitons, have been obtained in a communication window and conventional soliton in a 2 µm‐band can be also achieved. This demonstrates that MnO2 serves as a broadband optical modulator, which makes MnO2 more competitive in the future ultrafast photonics and helps to expand the frontier of photonic technology.

Period-timing bifurcation evolution in a nonlinear polarization rotation fiber laser

Period-timing bifurcation phenomenon widely exists in fiber laser. We investigate the period-timing bifurcation phenomenon in fiber resonator. Large period-timing of single pulse occurs due to mutual competition between dispersive wave and soliton. In addition, period-timing of soliton molecule is observed due to mutual attraction and repulsion between adjacent pulses. Furthermore, local periodic bifurcation has been obtained. All the period-timing bifurcation phenomena are related to many factors such as fiber birefringence, small signal gain, nonlinear effect and dispersion, etc. Exploring period-timing bifurcation is helpful to understand the dynamic evolution of pulse. Period-timing bifurcation has important applications in optical communication system, optical logic operation, all-optical computing and so on.

Back-Reflection in Resonant Fiber Optic Gyroscope and the Suppression Method

Backscattering and back-reflection are one of the main factors restricting the improvement of resonant fiber optic gyroscope accuracy. At present, most researches focus on backscattering. Due to the dependence on narrow linewidth laser, the interference of back-reflection light and the main light produces fluctuations in light intensity, which deteriorates the angle random walk of the resonant fiber optic gyroscope. This paper focuses on the back-reflection light outside the fiber ring resonator, taking the reflection on the end face of the photoelectric detector as an example, and simulates the influence on the detection noise of resonant fiber optic gyroscope. According to the frequency spectrum of intensity noise caused by back-reflection, a suppression method including length matching and frequency separation is proposed. The simulation and experimental results show that this method can effectively reduce the influence of back-reflection, and the angle random walk is improved by 6.06 dB with this method.

Slow optical vortices in multicoil fiber resonators

In this paper, we theoretically study the transmission of optical vortices (OVs) through a uniform N-turn coil of a multimode fiber. We suggest a scalar-approximation treatment based on coupled mode equations in slow amplitudes and study transformations of OVs and their orbital angular momentum (OAM) in such fiber resonators. We show that such resonators may exert super-efficient parametric control over the topological charge and OAM of the outcoming optical field. We study group delay time for transmitted OVs and show the possibility to implement on the basis of such coil resonators the delay lines for OAM light beams. This property is potentially important for optical fiber OAM communications.

Graphene‐assisted synthesis NH3 gas sensor based on silicon photonics crystal fiber and surface plasmon resonance

ObjectiveIn this article, we theoretically simulated a silicon core-based photonics crystal fiber combined with the Au/graphene coating thin-film to surround the fiber-air-holes with a plasmonic active medium for sensing NH3 gas concentrations. MethodsBy means of our previous research experiences and the related theory, the complex refractive index of graphene under different concentrations of NH3 exposing was analyzed and calculated by using the finite element method. ResultThe sensing average sensitivity of 0.0269 nm/ppm for the proposed NH3-gas sensor was theoretically predicted for the concentration of NH3 in the range from 1 ppm to 1000 ppm. In addition, the proposed photonics crystal fiber sensor can be extended into the other field applications, such as medical diagnostics, bio-chemical detection etc.

Characterization of the sensitivity of a surface plasmon resonance (SPR) fiber optic sensor composed of silver and nickel oxide layers

A surface plasmon resonance based fiber optic sensor is presented experimentally using silver and nickel oxide layers. The sensitivity analysis of the sensor has been carried out. Also, the influence of the nickel oxide layer thickness upon the sensitivity has been examined. The sensitivity is enhanced with the increase in thickness of nickel oxide layer up to 10 nm and decreased at larger values. The sensor composed of 40 nm silver-10 nm nickel oxide layers provides the highest sensitivity.

A Temperature Sensor Exploiting Plasmonic Phenomena Changes in Multimode POFs

A novel sensing method for temperature measurements of liquids, exploiting plasmonic resonance in multimode plastic optical fibers (POFs), has been devised. The possibility to measure the temperature is useful in several application fields of plasmonic sensors, such as when a binding test between a receptor and an analyte occurs, considering that the binding parameters are a function of the temperature. The novel temperature sensor consists of two different D-shaped POF connected in a cascade. The first element is a thermosensitive platform with a thin silicone layer on the POF core, whereas the second is a conventional surface plasmon resonance (SPR) D-shaped POF sensor. The operating principle of the novel temperature sensor is based on the variations of light launch conditions in the SPR-POF sensor as a consequence of the temperature changes in the solution covering the thermosensitive platform. In this way, the input light ray angle changes with the temperature, producing a shift in resonance wavelength conditions. The proposed sensor has been tested, as proof of concept, in a temperature range from <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$20^{\circ }\text{C}$ </tex-math></inline-formula> to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$38^{\circ }\text{C}$ </tex-math></inline-formula> with a step size of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$3^{\circ }\text{C}$ </tex-math></inline-formula> , to establish the role of the silicone layer on the thermosensitive platform and the best configuration in terms of sensitivity.

Dual-parameter sensor for simultaneously measuring refractive index and temperature based on no-core fiber and SPR effect

Refractive index and temperature are two basic properties of matter. Therefore, we propose a dual-parameter sensor based on no-core fiber and surface plasmon resonance (SPR). It can simultaneously measure temperature and refractive index. The sensor structure comprises no-core fiber, metal silver, and polydimethylsiloxane (PDMS). Metallic silver is used to excite the SPR effect, and PDMS is a suitable temperature-sensitive material. The silver film is deposited on the bottom of no-core fiber for refractive index measurement. Silver film and PDMS are deposited on the top of no-core fiber for temperature measurement. Numerical results show that refractive index and temperature can be reflected in the same spectrum, and the two parameters do not interfere with each other. This phenomenon improves the efficiency of measurement. In addition, the maximum spectral sensitivities of the sensors are 5200 nm/RIU and 7.2 nm/℃, respectively. The results also show that the sensor's performance is not sensitive to the change in structural parameters, which makes the sensor easy to prepare. Dual parameter measurement and simple structure make the sensor unique. It has good application prospects in biochemical detection, environmental monitoring, medical sensing, and other fields.

Suppressing backscattering noise of a resonant fiber optic gyroscope using coherent detection.

This paper provides a novel, to the best of our knowledge, method for suppressing backscattering noise of a resonant fiber optic gyroscope (RFOG) with a coherent detection technique. The light from the fiber ring resonator is mixed with a reference beam rather than being demodulated directly in traditional configurations, generating a coherent signal with a radio frequency. The central frequencies of the two reference lights used for the clockwise and counterclockwise waves are different to avoid the effect of backscattered waves. Besides, a common phase modulation is applied on the two counter-propagating waves to eliminate the parasitic effect due to the residual amplitude modulation in the phase modulator. Two demodulation schemes for the rotation rate detection from the coherent signals are then proposed and demonstrated, with performance on noise suppression tested. One is the beat-frequency demodulation, and the other is the self-mixing demodulation technique. The influence of backscattering intensity is reduced from 270°/h to 3°/h and 0.05°/h with the two demodulation techniques, respectively, showing a full suppression of backscattering noise.

Lossy mode resonance refractometer operating in the 1.55 µm waveband based on TiOxNy thin films deposited onto no-core multimode fiber by DC magnetron sputtering

We propose and demonstrate the use of titanium oxynitrides (TiOxNy) as flexible material for lossy-mode resonance (LMR) fiber sensing applications. The LMR characteristics of TiOxNy are investigated for a fiber refractometer consisting of a multimode fiber structure, which includes a no-core fiber coated with a thin film of TiOxNy, because of transitional phases between TiN and TiO2. The material coating was achieved through the N-O exchange during the film synthesis by reactive-magnetron DC sputtering. For a suitable sputtered coating with thickness of ∼270 nm, the 2nd LMR order is generated within the 1.55 µm wavelength region, compatible with fiber optic systems. The spectral response for the 2nd and the 3rd LMR orders of the candidate fiber structure was characterized for liquid refractive index (RI) variations from a set of isopropyl alcohol (IPA)/glycerin solutions. For glycerin concentrations ranged from 0% to 35% (RI from 1.3602 to 1.4091), it was found that the 2nd LMR order is significantly more sensitive than the 3rd LMR order, whose sensitivities are of 1238.445 nm/RIU and 111.39 nm/RIU, respectively.

Evaluation and Suppression of the Effect of Laser Frequency Noise on Resonant Fiber Optic Gyroscope

This article provides a novel method to analyze and calculate the effect of laser frequency noise on a resonant fiber optic gyroscope (RFOG). The output signal of the fiber ring resonator is expressed as the sum of various harmonic responses. It is found that the laser frequency noise at certain noise frequency would be demodulated together with the rotation-induced frequency signal, and thus deteriorating the gyro output stability. A theoretical model is then setup. The effect of laser frequency noise on the RFOG based on the separate modulation-demodulation technique is numerically evaluated and the effectiveness of the reciprocal modulation-demodulation technique is verified both theoretically and experimentally. The measured angular random walk of the reciprocal RFOG improves as the detected light power at the photodetector increases, which indicates that the measured angular random walk reaches the theoretical shot-noise limited sensitivity in the RFOG. The best value is 0.0021 °/√h when the light power arrived at the photodetector is 69 μW.