Side-polished Fiber Research Articles

Broadband and tunable fiber polarizer based on a graphene photonic crystal fiber.

The recent flourishing development of two-dimensional (2D) graphene has sparked considerable interest and extensive research on graphene-based optical fiber polarizers. However, studies on graphene-optical fiber polarizers focused on the structure with graphene films attached to side-polished fibers, which face challenges such as low birefringence of 10-6, low polarization extinction ratio (PER), and narrow polarizing window of tens of nanometers. Here, a fiber polarizer based on a graphene-photonic crystal fiber (Gr-PCF) is proposed firstly, which exhibits high birefringence of ∼2.5 × 10-3, high PER of ∼111 dB/mm, broad polarizing window of >400 nm, and tunable polarization states. Graphene or graphene/hBN/graphene (Gr/hBN/Gr) heterojunctions are attached to the surface of two square holes in the PCF to make one of the polarizing modes attenuate significantly. The tunability of the Fermi level (EF) in Gr/hBN/Gr enables the proposed device to function as a polarizer or a polarization-maintaining fiber. The combination of PCF's endless single-mode feature and graphene's broadband optical response feature enables the fiber polarizer to exhibit a wide spectrum range with single-mode transmission characteristics.

A Fiber optics based surface enhanced Raman spectroscopy sensor for chemical and biological sensing

This paper investigates an innovative surface-enhanced Raman scattering (SERS) sensor developed on a side-polished multimode optical fiber core. The optical fiber was integrated into specifically designed 3-dimensional printed mold, where manual polishing of the fiber took place. Microsphere Photolithography (MPL) techniques was employed to pattern periodic nanoantenna arrays on the polished surface, incorporating multiple disk diameters at a fixed periodicity. Subsequent gold deposition/lift-off were carried out to transfer the pattern from the photoresist to the fiber core, resulting in highly periodic hexagonal closed pack (HCP) arrays of nanodisks. These arrays can significantly enhance the SERS signal intensity compared to that of the fiber tip. The sensor's performance was demonstrated using various concentrations of Rhodamine 6G (R6G) dye ranging from 10−5 to 10−9 M as a function of disk diameter and sensing surface area. The resulting spectra revealed characteristic peak positions that aligned well with the fingerprint Raman spectra of R6G. The results demonstrates that the sensitivity is 10−9 M for the sensor with an 800 nm disk diameter.

Dual-channel photonic crystal fiber dual-parameter sensor exploiting surface plasmon resonance

A surface plasmon resonance (SPR) based sensor using a negative curvature circular side-polished photonic crystal fiber was proposed. The sensor’s sensitivity was analyzed using the finite element method. The impact of structural parameters was investigated. The sensor exhibits an average wavelength sensitivity (WS) of 7846 nm/RIU in the refractive index range of 1.370–1.396 and 2350 nm/RIU in the range of 1.330–1.370, with maximum WS of 46000 nm/RIU. For refractive index and magnetic field dual-parameter sensing, the simultaneously obtained magnetic field sensitivity is 0.84 nm/mT. The proposed SPR sensor demonstrates remarkable sensitivity, making it suitable for refractive index and magnetic field sensing applications.

Surface roughness analysis of side-polished fiber based on the importance of texture features

In order to explore the use of side-polished fibre (SPF) for microprobe-type "lab-on-fibre", this study presents an analysis of the surface roughness in side-polished fiber (SPF) using the gray level co-occurrence matrix (GLCM) texture feature analysis method. Experimental results show that the flat areas of the SPF polished surface exhibit texture characteristics with high mean values in contrast and entropy, and low mean values in the angular second moment (ASM), homogeneity, and correlation. Employing the random forest (RF) feature importance ranking method based on the Gini coefficient and out-of-bag (OOB) error estimation, this study assesses the sensitivity of various GLCM texture parameters in classifying different roughness levels of the SPF polished surfaces. A feature subset comprising variance, ASM, entropy, and contrast is identified as optimal. Utilizing this subset, the paper conducts an RF classification validation experiment on the roughness of the SPF polished surfaces, with results showing an RF classification accuracy of 95.65%.This research provides evidence for exploring the impact of rough polished surfaces in SPF optic sensors on the light coupling mechanism with environmental materials and its influence on sensor sensitivity. It lays the foundation for exploring the precise identification of high-sensitivity areas on SPF polished surfaces.

Highly sensitive near-field leakage-enhanced optical fiber SPR sensor based on gold nanoarrays modulation

A novel near-field leakage-enhanced optical fiber surface plasmon resonance (NLF-SPR) sensor based on the synergistic sensitization of cuboid gold nanoarrays and WSe2 film is proposed for the first time to our knowledge. The sensor is composed of a side-polished multimode fiber, a continuous gold film, a continuous tungsten selenide (WSe2) film, and well-arranged cuboid gold nanoarrays. The sensor leverages the high carrier mobility characteristic of the WSe2 film, the near-field leakage enhancement arising from the nanoarrays structure, and the localized electric field enhancement property introduced by nanotips to enhance the refractive index sensitivity. In order to optimize the spectral characteristic, the modulation of electric field distribution and spectral characteristic by the structural parameters of gold nanoarrays is investigated through three-dimensional (3D) finite element simulation. Results show that in the refractive index range of 1.3332–1.3432 refractive index unit (RIU), the average sensitivity of the NLF-SPR sensor can reach up to 10108 nm/RIU, and the highest sensitivity can reach up to 14692.46 nm/RIU. The average sensitivity and the highest sensitivity are 1.87 times and 2.56 times higher, respectively, than those of the side-polished fiber SPR sensor with a monolayer gold film. Furthermore, the experimental results demonstrate that the near-field leakage enhancement introduced by gold nanoarrays improves the performance of the fiber SPR sensor, resulting in a 49.3 % increment in sensitivity. The experimental results are in agreement with the trend of the simulation results. Even better performance improvements have been achieved compared to existing methods and a more flexible approach to performance tuning is provided. With the maturity and development of various nanoarray processing techniques such as focused ion beam, electron beam lithography, and nanoimprint lithography, the proposed NLF-SPR sensor has the potential to be fabricated on a large scale and is expected to be widely employed in biomedical, clinical applications, and other fields.

Directional bending sensor based on Mach-Zehnder interferometer formed by side-polished multimode fiber

This work proposes a fiber bending sensor based on the Mach-Zehnder interferometer (MZI) constructed using a side-polished multimode fiber (MMF) with bending direction recognition. The sensor is fabricated by directly fusing a section of side-polished MMF sandwiched between two no-core fibers (NCFs) to an input and output single-mode fibers (SMFs). As the applied curvature varies from 0 m−1 to 1.64 m−1, the transmission spectra of the sensor exhibit distinct and linear wavelength shift in opposite directions. The maximum sensitivity observed in 0° and 180° bending is 3.252 nm/m−1 and −1.146 nm/m−1, respectively. The maximum temperature sensitivity is 0.0621 nm/°C and this effect can be compensated by using the sensitivity matrix. The advantages of the proposed sensor include its ability to accurately quantify the direction and magnitude of bending, temperature crosstalk elimination, and cost-effectiveness. These features make the sensor highly desirable for a wide range of practical directional bending applications, such as medical wearable devices for human joint range of motion monitoring.

A simple structure and high sensitivity side-polished micro-structured fiber RI sensor based on gold-coated open-loop channel

A simple structure and high sensitivity side-polished micro-structured fiber RI sensor based on gold-coated open-loop channel

Spider silk biological material for Q-switched temperature sensor

Abstract A temperature sensor using compact design and highly sensitivity of side polished fiber and fiber Bragg grating as the sensing elements, Q-switched pulse fiber laser source with spider silk as a saturable absorber is proposed and demonstrated. Spider silk sample was gently collected from a live spider, specifically, the jumping spider of Plexippus sp. which then incorporated within the laser cavity by deposited the silk onto the surface of the fiber ferrule to facilitate the generation of Q-switched pulse fiber laser. The temperature variations were detected by monitoring the pulse train and radio frequency shift from the oscilloscope. The performance of the side polished fiber sensor probe shows a sensitivity of 0.1522 kHz/°C, with 0.9479 coefficient of determination value as the temperature increased from -0.5 °C to +3.1 °C. Besides, a linear temperature re-sponse in the range of 25 °C – 55 °C with a sensitivity of 0.0423 kHz/°C, and a linear correlation coefficient of 0.951 was experimentally achieved for a fiber Bragg grating device. The spider silk as a saturable absorber material is compatible with fiber optic interconnection and the temperature sensing characteristics were successfully demonstrated. The sensor's straight-forward design further enhances its desirability as a sensor for temperature monitoring, including in the field of biological treatments, consumer electronics, detection of chemical analytes, and medical diagnosis.

Design and Analysis of Surface Plasmon Resonance Sensor with Open-Loop Side-Polished Photonic Crystal Fiber

Design and Analysis of Surface Plasmon Resonance Sensor with Open-Loop Side-Polished Photonic Crystal Fiber

High-performance Fabry-Perot fiber optic sensors from one-step laser side-polished platforms

A facile one-step non-contact process was developed for preparing the substrates for Fabry-Perot-based side-polished optical fiber sensors. A carbon dioxide (CO2) laser cladding removal technique was used to control the profile of the polished fiber surface and to introduce two reflective cavities. The substrates were characterized for a range of cavity lengths and their thermal response was studied. This device added a degree of freedom to the design of optical fiber based Fabry-Perot sensors and its potential was demonstrated by coating the substrate with polydimethylsiloxane (PDMS). The resulting sensors had a three-order of magnitude increase in sensitivity when compared to the substrate. The polished flat surface provided a route for the integration of novel materials for sensing applications, particularly those where polarization control was vital for light-matter interaction, for example, low dimensional materials such as graphene or MXene. The inherent simplicity, mechanical stability, and scalability of this approach are important steps for the realization of practical devices of this type.

Amplified frequency-shifted interferometry fiber loop ringdown glucose sensors using side-polished fiber

An amplified frequency-shifted interferometry fiber loop ringdown (FSI-FLRD) sensor is proposed for the concentration measurement of glucose solutions. It detects glucose concentrations by measuring the ringdown distance of the continuous light in the fiber ringdown loop (RDL) instead of the ringdown time of the pulsed light in the loop as in traditional FLRD glucose sensors. A bidirectional erbium-doped fiber amplifier (Bi-EDFA) and a segment of side-polished fiber (SPF) are respectively inserted into the RDL to compensate the loop attenuation and to act as the sensing probe. The proposed optical sensor was tested with glucose solutions in the concentration range from 0 to 14 % at room temperature, which exhibits a linear response with a sensitivity of 0.0013 km−1/% (4.12x10−4 dB/%) for the 0–8 % glucose solutions. Additionally, it also achieved a system stability of 0.75 %, with a measuring resolution of around 2.63 %. The experimental results show the proposed sensor has simple structure, low cost, robust stability and good resolution, and it is a suitable alternative for the detection of glucose concentrations in biological detection, component analysis and on-line quality control in food industry.

Asymmetric Laser Field Interaction with MXene Coated on the Side Surface of Optical Fibers for Ultrafast Nonlinear Switches.

In recent years, there has been significant interest in researching ultrafast nonlinear optical phenomena involving light-matter interactions in two-dimensional (2D) materials, owing to their potential applications in optics and photonics. MXene, a recently developed 2D material, has garnered considerable attention due to its graphene-like properties and highly tunable electronic/optical characteristics. Herein, we demonstrate ultrafast all-optical switches based on four-wave-mixing (FWM) utilizing the nonlinear optical property of MXene Ti3C2Tx. In order to realize the device, we deposited multilayered Ti3C2Tx in the form of a supernatant solution onto the polished surface of a side-polished optical fiber, enabling the interaction of Ti3C2Tx with the asymmetric evanescent field of the incident input. We systematically characterized the nonlinear optical responses derived from the Ti3C2Tx layers. The fabricated device exhibits notable performance metrics, an enhancement of the extinction ratio, and a conversion efficiency of the newly generated signal, displaying 5.3 and 5.2 dB, respectively. Additionally, the device operates at high modulation frequencies, reaching up to 20 GHz, and demonstrates high-resolution detuning with channel distances of up to 15 nm. Our findings highlight the potential of MXene-based materials for ultrafast optical data management systems.

Evanescent wave quartz-enhanced photoacoustic spectroscopy employing a side-polished fiber for methane sensing

We present an all-fiber-based laser gas analyzer (LGA) employing quartz-enhanced photoacoustic spectroscopy (QEPAS) and a side-polished fiber (SPF). The LGA comprises a custom quartz tuning fork (QTF) with 0.8 mm prong spacing, two acoustic micro-resonators (mR) located on either side of the prong spacing, and a single-mode fiber containing a 17 mm polished section passing through both mRs and QTF. The SPF polished face is positioned to enable the evanescent wave (EW) to create a photoacoustic wave and excite the fundamental flexural mode of the QTF. Sensor performance was demonstrated using methane in nitrogen gas mixtures, with CH4 mixing ratios ranging from 75 ppmv to 1% (by volume), measured with an accumulation time of 300 ms, and a minimum detection limit of 34 ppmv subsequently determined. The EW-QEPAS sensor is ideal for miniaturization, as it does not contain any free-space optics and is suitable for gas sensing in harsh environments and where mobility is required.

Ultrahigh Refractive Index Sensitivity With Lossy Mode Resonance in a Side-Polished Low-Index Polymer Optical Fiber

Ultrahigh Refractive Index Sensitivity With Lossy Mode Resonance in a Side-Polished Low-Index Polymer Optical Fiber

Ultrasensitive SPR sensor using PDMS-filled side-polished hollow-core fiber

Ultrasensitive SPR sensor using PDMS-filled side-polished hollow-core fiber

Side-Polished Coherent Fiber Bundle Assemblies: A Pathway to Large Imaging Arrays

Side-Polished Coherent Fiber Bundle Assemblies: A Pathway to Large Imaging Arrays

Side-polished Silica-Fluoride Multimode Fibre Pump Combiner for Mid-IR Fibre Lasers and Amplifiers

Side-polished Silica-Fluoride Multimode Fibre Pump Combiner for Mid-IR Fibre Lasers and Amplifiers

D-shape Optical Fiber Development and Enhancement as a Refractive Indices Sensor Using Surface Plasmon Resonance

This article showcases the development and utilization of a side-polished fiber optic sensor that can identify altered refractive index levels within a glucose solution through the investigation of the surface Plasmon resonance (SPR) effect. The aim was to enhance efficiency by means of the placement of a 50 nm-thick layer of gold at the D-shape fiber sensing area. The detector was fabricated by utilizing a silica optical fiber (SOF), which underwent a cladding stripping process that resulted in three distinct lengths, followed by a polishing method to remove a portion of the fiber diameter and produce a cross-sectional D-shape. During experimentation with glucose solution, the side-polished fiber optic sensor revealed an adept detection sensitivity of 0.2015 au. /RIU. In order to improve sensitivity, a recent sensor was subjected to a coating process utilizing a thin film layer of gold (Au) measuring a thickness of 50 nm. The sensor was subsequently subjected to a series of tests utilizing the same glucose solutions as in previous experiments. A notable enhancement in sensitivity was observed when utilizing gold as the sensing material, with an equivalent maximum sensitivity of 3.101 au. /RIU.

High resolution curvature sensor based on enhanced backscattering in side polished optic fiber

A high-resolution curvature sensor based on enhanced backscattering in side polished optic fiber is proposed and experimentally investigated. Directional curvature sensor fabrication procession and operating principle are introduced. A push–pull structure with 2 side polished curvature sensors sticking on opposite sides of an elastic beam is used to enhance sensitivity and responsive linearity. Experiments are carried out by high accuracy relative intensity (RI) measurement system based on modified pulse self-referencing technology. Experimental results show that curvature sensor can achieve a sensitivity of 15.21 dB/m−1 in the curvature range of −0.48–0.48 m−1, and the curvature resolution is as low as 2 × 10−5m−1.

Impact of structural parameters on multimode D-shaped optical fiber refractive index sensors for different materials

In this work, a D-shaped optical fiber sensor has been experimentally developed to compare how the refractive index (RI) of a water analyte (used as the cladding layer over a small length of the stripped D-polished optical fiber) changes due to the inclusion of an unknown concentration of two distinct materials, one with a low RI and the other with a high RI. No metal film is deposited in the proposed D- shaped optical fiber sensor and hence we demonstrate the sensor's ability to detect the lowest concentration of the added material into the water analyte without employing the surface plasmon modes. A side-polished multi-mode optical fibre with various sensing lengths and polishing depths is used to construct the D-shaped fibre sensor. Experimental results verify that in a tunable refractive index (RI), the sensitivity increases with the sensing length due to the increase in the interaction area between the surrounding material and the sensing area. The sensitivity also increases with polishing depth in the high-RI range for materials with higher concentrations. The D-shaped fibre sensor's maximum sensitivity of 25.076 a.u./RIU is attained in the range of low refractive index values (1.3329) to (1.3345) RIU. Nonetheless, its maximum sensitivity drops to 0. 317 a.u./RIU at the high refractive index region of 1.348–1.4048 RIU. This sensor is predicted to have potential uses in low-RI materials with very low concentrations. Therefore, the best D-shape fibre sensor was used to detect the lowest concentration of the sodium chloride solution in the low refractive index range, and it was found that the lowest detected concentration was 0.012% with a high sensitivity of 327.32 a.u./RIU.