Microbottle Resonator Research Articles

Highly-selective and temperature-compensated toluene sensor based on MOF-actuated optical WGM microresonator

This paper reports an optical fiber toluene sensor based on whispering gallery mode (WGM) microbottle resonator. The sensor includes a single-mode fiber (SMF)- no-core fiber (NCF)- SMF offset structure, which can be used as not only a coupler to couple light into the microbottle but also a multimode interferometer. The microbottle is formed by self-assembly of polydimethylsiloxane (PDMS) polymer doped with metal-organic framework (MOF) under the action of surface tension and gravity. The high specific surface area, suitable pore size, nitrogen-containing functional groups of MOF-Fe-PD and nonpolar groups on PDMS impart the high sensitivity and specific response of the sensor to toluene. When toluene is captured by the MOF and PDMS, the refractive index and volume of the cavity change, which affects the mode shift of WGM. According to test results, WGM of the sensor shows a linear sensitivity of 12.44pm/ppm with toluene concentration between 0 ppm and 337 ppm at room temperature, but it is affected by temperature crosstalk. While multimode interference dip is only sensitive to temperature, which can compensate for the mode shift of WGM caused by temperature change. Repeatability experiments show that the response and recovery time of the sensor are less than 70s. The method provides a toluene sensor with high selectivity, stable performance and simple preparation, which has potential environmental benefits and good industrial application prospects.

Lever-enabled milli-Newton mechanical force detection via a microbottle resonator.

We demonstrate a milli-Newton mechanical force sensor based on a whispering gallery mode microbottle resonator (MBR). A lever model is established by coupling the MBR with a tapered fiber, whose ratio of load arm to effort arm (RLE) is flexibly adjusted to enlarge the detection range. The mechanical force is induced by attaching a capillary on the MBR stem and applying the downward displacement, which deforms the MBR's radius and thus shifts the resonance wavelength. The dependence of the capillary displacement on the mechanical force is theoretically deduced and verified. Experimentally, the sensors with different RLEs are built, and the maximum sensitivity of -10.48 pm/mN with a resolution of 40 µN is obtained. The achieved detection range is 0-4 mN, which depends on the capillary displacement and RLE of the lever. With the merits of easy fabrication and flexible structure, the proposed sensor shows great potential in biomedical and structural health monitoring.

Graphene oxide-coated microbottle resonators for relative humidity sensing

Graphene oxide-coated microbottle resonators for relative humidity sensing

Packaged WGM MBR sensor for high-performance temperature measurement using CNN-based multimode barcode images.

The whispering gallery mode (WGM) optical microresonator sensors are emerging as a promising platform for precise temperature measurements, driven by their excellent sensitivity, resolution and integration. Nevertheless, challenges endure regarding stability, single resonant mode tracking, and real-time monitoring. Here, we demonstrate a temperature measurement approach based on convolutional neural network (CNN), leveraging the recognition of multimode barcode images acquired from a WGM microbottle resonator (MBR) sensor with robust packaged microresonator-taper coupling structure (packaged-MTCS). Our work ensures not only a high sensitivity of -14.28 pm/℃ and remarkable resolution of 3.5 × 10-4 ℃ across a broad dynamic range of 96 ℃ but also fulfills the demands for real-time temperature measurement with an average detection accuracy of 96.85% and a speed of 0.68s per image. These results highlight the potential of high-performance WGM MBR sensors in various fields and lay the groundwork for stable soliton microcomb excitation through thermal tuning.

Analysis and optimization of optical frequency comb spectra of magnesium fluoride microbottle resonator

<sec>Optical frequency comb has shown great potential applications in many areas including molecular spectroscopy, RF photonics, millimeter wave generation, frequency metrology, atomic clock, and dense/ultra-dense wavelength division multiplexed high speed optical communications. Optical frequency comb in the microresonator supporting whispering-gallery mode has attracted widespread interest because of its advantages such as flexible repetition rate, wide bandwidth, and compact size. The exceptionally long photon lifetime and small modal volume enhance light-matter interaction, which enables us to realize intracavity nonlinear frequency conversions with low pump threshold. With the advantages of small size, low power consumption, wide spectral coverage and adjustable dispersion, the magnesium fluoride microresonator optical frequency comb has potential applications in optical communication and mid-infrared spectroscopy.</sec><sec>In this work, the spectral characteristics of the optical frequency comb generated by a magnesium fluoride whispering-gallery mode microbottle resonator platform are investigated. In order to optimize the spectral distribution of the optical frequency comb of the magnesium fluoride microbottle resonator, the second-order dispersion and higher-order dispersion of the bottle resonator structure under different curvatures and axial modes are solved iteratively by the finite element method, and the spectral evolutions of the optical frequency comb under different axial mode excitations are simulated by solving the nonlinear Schrödinger equation through the split-step Fourier method. The results show that near-zero anomalous dispersion tuning can be achieved in a wide bandwidth range by exciting low-order axial mode at an optimal radius of curvature, while the high-order axial mode will lead the microbottle resonator to present the weak normal dispersion. The weaker anomalous dispersion in the lower-order axial mode broadens the bandwidth of the optical comb, demonstrating that the third-order dispersion and the negative fourth-order dispersion can broaden the Kerr soliton optical comb; the weak normal dispersion in the higher-order axial mode suppresses the generation of the Kerr optical comb, and the Raman optical comb dominates. The selective excitation of Kerr soliton combs and Raman combs can be achieved by modulating the axial mode of the microbottle resonator under suitable pumping conditions. The present work provides guidance for designing the dispersion in magnesium fluoride microresonator and the experimental tuning of broadband Kerr soliton optical combs and Raman optical combs.</sec>

All-Optical Tuning of Microbottle Resonator Assisted by a Movable Probe With Magnetic Nanoparticles

All-Optical Tuning of Microbottle Resonator Assisted by a Movable Probe With Magnetic Nanoparticles

Acetone gas sensor based on PVA self-assembled WGM microbottle resonator coated with PDMS

In this paper, an acetone gas sensor based on a polyvinyl alcohol (PVA) self-assembled whispering gallery mode (WGM) microbottle resonator coated with polydimethylsiloxane (PDMS) is proposed and demonstrated. The preparation of the PVA self-assembled microresonator and the coating of PDMS are all finished by employing a dip coater. Compared with the PVA microresonator and the PDMS microresonator, the PVA microresonator coated with PDMS shows the highest acetone gas sensitivity, which is up to −6.34 pm/ppm. Besides, it can effectively reduce the effects of humidity on the detection of acetone gas compared to the PVA microresonator. Since the concentration of acetone in breathing gas is an indicator of diabetes, the proposed sensor with the benefits of small size, low cost, and simple manufacture using non-toxic materials presents promising applications for painless and non-invasive diagnosis of diabetes.

Laser structure based on an erbium-doped fiber ring and a whispering gallery mode microbottle resonator.

A novel fiber laser structure, to the best of our knowledge, based on an erbium-doped fiber ring (EDFR) and a silica microbottle resonator (MBR) is proposed and investigated experimentally. Two fiber laser samples based on MBRs with different geometries and diameters of 200 and 150µm are fabricated, and their performance is studied experimentally. Periodic whispering gallery mode spectra of the MBRs are dependent on the position of the fiber taper used for coupling of light into the MBR, and this dependence is explored to achieve lasing at different wavelengths by moving the light coupling point along the axis of the microbottle incorporated into the proposed EDFR-MBR system. The influences of the pump laser power and light polarization on the system performance and laser stability are also investigated. Single-mode lasing with a maximum optical signal-to-noise ratio of 32dB is demonstrated.

Review of Microbottle Resonators for Sensing Applications

Microbottle resonators (MBR) are bottle-like structures fabricated by varying the radius of an optical fiber. MBRs can support whispering gallery modes (WGM) by the total internal reflection of the light coupled into the MBRs. MBRs have a significant advantage in sensing and other advanced optical applications due to their light confinement abilities in a relatively small mode volume and having high Q factors. This review starts with an introduction to MBRs’ optical properties, coupling methods, and sensing mechanisms. The sensing principle and sensing parameters of MBRs are discussed here as well. Then, practical MBRs fabrication methods and sensing applications are presented.

Characteristics and Temperature Sensing Application of Optical Microbottle Resonators

Characteristics and Temperature Sensing Application of Optical Microbottle Resonators

Comparative study an effect of polymethyl methacrylate coating on optical microbottle resonator for enhancing sensing performance for ethanol liquid sensor

AbstractThis paper observed the performance of the coated optical microbottle resonator (MBR) for the liquid ethanol concentration sensor. The MBR is prepared in three sizes by a technique known as “soften‐and‐compress” from silica fiber SMF‐28 with parameters named stem diameter, bottle length, and bottle diameter. The MBR is then coated with PMMA by the “drop‐casting” technique used as an ethanol sensor. The MBR‐PMMAs were characterized by microfiber diameter and managed to have a Q‐factor. The ethanol liquid concentration used is from 10% to 100% ppm. The sensitivity, linearity, repeatability, stability, and wavelength shift results were then used to determine the performance of MBR‐PMMAs as an ethanol sensor. The most significant size of MBR‐PMMA, known as “C,” is defined as an excellent ethanol liquid concentration sensor. Additionally, the resonator's size is determined and may influence its ability to perform well as a sensor.

Switchable multi-wavelength fiber laser based on a taper-coupled microbottle resonator

A multi-wavelength erbium-doped fiber laser (EDFL) based on a taper-coupled microbottle resonator is proposed and investigated experimentally. The taper-coupled microbottle resonator has the comb filter characteristics with Q factor 2.9 × 104, which is integrated into an EDFL system. The taper-coupled microbottle resonator was packaged by ultraviolet glue, which has excellent stability of output power and wavelength at room temperature. Then, switchable dual-, triple-, quad- and quint-wavelength fiber laser states can be achieved by adjusting the polarization controller (PC). Furthermore, for dual-wavelength and triple-wavelength laser state, the position of output wavelengths also can be precisely modulated with the PC. The developed multi-wavelength EDFL has the optical signal to noise ratio as high as 40 dBm, and the wavelength shift and peak power fluctuation are less than 0.03 nm and 6 dBm.

Optical fiber hydrogen sensor based on self-assembled PDMS/Pd-WO3 microbottle resonator

In this paper, a new optical fiber hydrogen(H2) sensor based on a self-assembled microbottle resonator was proposed. The self-assembled microbottle was simply obtained by coating the single-mode fiber (SMF) with an internal composite material layer of palladium-tungsten trioxide (Pd-WO3) that was sensitive to H2 and an outer organic polymer material layer of polydimethylsiloxane (PDMS) with a significant thermal response. The microbottle resonator was further fabricated by coupling a tapered fiber with the self-assembled microbottle to excite whispering gallery mode (WGM). When the WGM resonator is exposed to H2, H2 molecules penetrate the PDMS and undergo redox reaction with the Pd-WO3. After the PDMS absorbs the reaction heat, its volume and refractive index will change, along with the wavelength shift of the WGM resonator. Therefore, a simple and low-cost H2 sensor is realized by observing the shift of resonance wavelength. Experimental results showed that the hydrogen sensor had a maximum sensitivity of − 3.091 nm/% at 25 ℃. And the resonance wavelength just shifted a small distance when the relative humidity increased from 22.87 % to 84.59 % or the temperature rose from 20.2 ℃ to 30 ℃, which indicated the sensor had preferable resistance to disturbances of external humidity and temperature.

Simulation of Optical Hollow Microbottle Resonator for Sensing Applications

Simulation of Optical Hollow Microbottle Resonator for Sensing Applications

Broadband Manipulation of Stokes Raman Frequency Combs Via Mode Division Multiplexing in Optical Microcavities

We theoretically and experimentally investigate broadband manipulation of Stokes frequency comb generation in a silica microbottle resonator. We realize selective excitation of spectrally trapped Stokes combs belonging to distinct transverse mode families and a spectral tuning range up to ∼14.3 nm via coupling engineering by exciting distinct axial mode families with appropriate quality factors ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Q</i> s). Moreover, radial mode number selection, microcavity diameter control, or injection power adjustment also enables us to shift the Stokes comb wavelength. The tuning bandwidth can be extended to hundreds of nanometers by theoretical prediction using the bottle modal analysis and Coupled Lugiato Lefever (LL) equations simulation. We also show that multiple regimes in two-dimensional (2D) patterns can be selectively triggered depending on the cavity detuning, including Kerr frequency comb, single-frequency Raman lasing, multimode Raman lasing, and soliton crystal-like state. Our approach provides a scheme for greatly extending the wavelength tuning range of compact Raman laser devices with high performance.

Packaged optofluidic microbottle resonator for high-sensitivity bidirectional magnetic field sensing.

We demonstrate a high-sensitivity bidirectional magnetic field sensor based on a packaged optofluidic microbottle resonator (OFMBR) filled with magnetic fluid (MF). The relationship between sensitivity and different wall thicknesses and radial modes of OFMBR is theoretically analyzed. Then the thin-wall OFMBR is fabricated by etching a capillary with the fusion discharge process. The OFMBR and tapered fiber is packaged with a portable and robust coupling configuration. By applying perpendicular or parallel magnetic field directions to the OFMBR, opposite refractive index responses of the MF can be obtained, with resonant wavelengths redshifted or blueshifted as the magnetic field intensity is increased. A magnetic field sensitivity of 98.23 pm/mT can be obtained by using the second-order radial mode when the magnetic field is perpendicular to the packaged OFMBR. When the magnetic field is parallel to the packaged OFMBR, the sensitivity is -304.80 pm/mT by using the third-order radial mode and the detection limit reaches 0.0656 mT. The proposed sensor has the advantages of easy fabrication, high sensitivity, and reliability, showing a great potential in bidirectional magnetic field application.

Temperature-independent relative humidity sensing properties of polymer micro-bottle resonators coated with graphene oxide

A polymer-based micro-bottle resonator coated with graphene oxide (GO) film is presented to improve the relative humidity (RH) sensing performance. Polymeric material Loctite 3525 was coated onto a quartz fiber and cured by using UV light irradiation and thermal reflow technology. A layer of GO film was prepared on the micro-bottle resonator by the dip impregnation method, which realized a high Q-factor (>104) transmission of energy by appropriately designing a wave-guide resonator coupling. By optimizing the concentration of GO dip impregnation solution, high sensitivity and figure of merit (FoM) of 0.161 nm/%RH and 2.01/%RH were achieved in the RH range of 22–81%. In addition, after high-temperature annealing at 300 °C, the temperature sensitivity decreased by an order of magnitude from 0.793 nm/°C to 0.068 nm/°C, which significantly reduces the cross-sensitivity between humidity and temperature. The proposed resonator has the advantages of being compact in size, low in cost, high sensitivity, and low in temperature crosstalk.

Monitoring and identifying pendant droplets in microbottle resonators

Optofluidic resonators are capable of characterizing various fluidic media. Here, we propose an optofluidic microbottle resonator (OFMBR) that is applied to generate pendant droplets, whose maximum mass is related to the liquid surface tension. Mass and type of droplets forming along the OFMBR stem can be monitored in real time by spectrum variation. As a pendant droplet grows, increased droplet gravity introduces a decreased coupling gap and compressive force between the tapered fiber and OFMBR, leading to a resonance wavelength shift. The operation mechanism of the proposed sensors is validated by theoretical simulation and experimental results. From the experimental spectra, a liquid mass sensor with maximum sensitivity of − 3.34 pm / mg is obtained, and distilled water and alcohol can be identified. This scheme provides a new thread for droplet generation as well as fluidic properties characterization.

Comparative Study on Sensing Properties of Fiber-Coupled Microbottle Resonators With Polymer Materials

Optical whispering gallery mode (WGM) microbottle resonators based on a variety of polymer materials (benzocyclobutene (BCB), UV88 (Relentless, China) and Loctite3525 (HenKel, Germany)) were fabricated and investigated experimentally. The polymer materials were spin-coated onto the fiber and cured by ultraviolet (UV) light followed by heating to form a microbottle structure of different shapes and diameters. The WGMs were excited by tapered fiber, and the spectral characteristics of all realized microbottle cavities were evaluated, such as quality factor (Q > 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sup> ), free spectral range and polarization mode (TE and TM). The temperature and refractive index (RI) sensing performance are analyzed and Q-factor changes during the sensing process. In addition, a newly application of UV light intensity sensing for the polymer microbottle resonators was also demonstrated firstly. According to the experimental results that the microbottle resonator of BCB displays good UV light intensity sensitivity (0.0011 <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">nm</i> /( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">mw/cm</i> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> )) and figure of merit (FOM) (0.0122/( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">mw/cm</i> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> )). This sensor is a simple structure, low-cost material, robust performance, and possesses attractive application prospects in sensing and optical devices.

A Study of Optical Micro-bottle Resonator Humidity Sensor

This experiment reports the fabrication of the optical Micro-bottle Resonator (MBR) as a relative humidity (RH) sensor. The MBR is fabricated via the “soften-and-compress” method to create the bottle-shaped with diameter Db = 175 um. The MBR is then optically excited using a 8 μm microfiber and was found to have a Q Factor of >105. The MBR was then employed as a humidity sensor with the RH level percentage range between 40% to 100% and the performance is compared with a non MBR microfiber. The MBR sensor was found to have a sensitivity of 0.2973 dBm/%, linearity >90% and and is superior to the bare microfiber in all measured parameters. The MBR humidity sensor was also found to have good repeatability and stability over a period of 60 seconds compare to bare microfiber.