Ultra-sensitive micro-displacement sensor based on a U-shaped bent SMF.

Sensors based on irregularly shaped bent optical fiber devices have attracted considerable interest in many applications. However, the effective interference length and bent radius of the irregular shape fiber have not been given accurately. Here an equivalent arc model is proposed to define the effective interference length and bent radius of the U-shaped fiber device: the U-shaped optical fiber is equivalent to a regular arc.

Rotation angle measurement method based on self-mixing interference of a fiber laser.

A rotation angle measurement method based on self-mixing interference (SMI) of a fiber laser is proposed. The rotation angle can be calculated indirectly by the displacement measured by SMI. In the experiment, a linear cavity fiber laser with simple structure and high flexibility is used as the optical source for measuring the deflection angle.

NbCT MXene-tilted fiber Bragg grating optofluidic system based on photothermal spectroscopy for pesticide detection.

An optofluidic system based on photothermal spectroscopy is proposed, which combines molecular photothermal effect with NbCT MXene-tilted fiber Bragg grating (TFBG) for the detection of organophosphorus pesticides (OPs) with temperature compensated. Under the irradiation of excitation light, the photothermal effect of OPs produces a detectable change in the refractive index of the sample, and the concentration of chlorpyrifos can be quantified using TFBG. The NbCT MXene coated TFBG allow more molecules to be absorbed on the surface of TFBG, which enhances the interaction between light and matter, and improves the sensitivity of detection.

Enhanced photothermal signal detection by graphene oxide integrated long period fiber grating for on-site quantification of sodium copper chlorophyllin.

An enhanced photothermal signal detection method based on graphene oxide (GO) integrated long period fiber grating (LPFG) for on-site sodium copper chlorophyllin (SCC) quantification is proposed. SCC, as a porphyrin compound, can be photonically excited to induce a stronger photothermal effect. GO offers superior molecular adsorption and thermal conductivity properties; depositing it on the LPFG surface significantly improves the sensitivity and detection efficiency of the SCC photothermal signal, when irradiated with a 405 nm laser.

Simultaneous measurement of the BOD concentration and temperature based on a tapered microfiber for water pollution monitoring.

An optical sensor that simultaneously measures the concentration of the biochemical oxygen demand (BOD) and temperature in water based on a tapered microfiber is proposed for environmental monitoring. The sensor is characterized by a strong evanescent field, which is more sensitive to liquids with a low refractive index and a low transmission loss. The results show that as the BOD concentration increases, the interference spectrum shifts toward longer wavelengths, the spectral loss decreases, and the sensitivities of the BOD are 12.

Magnetic sensor based on serial-tilted-tapered optical fiber for weak-magnetic-field measurement.

An optical fiber magnetic field sensor based on serial-tilted-tapered fiber (STTF) integrated with magnetic fluid is proposed. The compact STTF structure consists of two closely tilted-tapered fibers with a length of approximately 836 µm, which results in stronger mode coupling. The transmission characteristics of the proposed sensor under different magnetic field intensities (MFIs) have been studied.

Microfiber coupler with a Sagnac loop for water pollution detection.

The measurement of chloride ion concentrations has been studied for the purpose of monitoring the quality of water resources. In this paper, a chloride ion sensor based on a microfiber coupler with a Sagnac loop is proposed. The microfiber coupler, which acts as the sensing unit and has a diameter of 10 μm and a length of 1 mm, is fabricated using the flame-brushing technique, and the two ends are connected to form a Sagnac loop, which acts as a reflector to enhance the reflection in the structure.

Tunability of Hi-Bi photonic crystal fiber integrated with selectively filled magnetic fluid and microfluidic manipulation.

Optical fiber microfluidics technology can implement the mutual tune of the light field and fluid in micro-nano scale. In this paper, one core of high-birefringence photonic crystal fiber (Hi-Bi PCF) is used as a microfluidic channel. The birefringence of FeO nanofluid is experimentally and theoretically investigated by selectively infiltrating the magnetic fluid into the core of the Hi-Bi PCF.

Serial-tilted-tapered fiber with high sensitivity for low refractive index range.

We propose an optical fiber sensor for low refractive index (RI) based on a serial-tilted-tapered fiber (STTF), which can be considered as two tightly concatenated micro Mach-Zehnder interferometers (MZIs). The STTF has a compact length of 959.8 μm, and can realize point detection and sensing in limited space.

Tunable interlayer coupling and Schottky barrier in graphene and Janus MoSSe heterostructures by applying an external field.

A Janus MoSSe monolayer, synthesized recently though the chemical vapor deposition method [A. Y. Lu, H.

Random Multiple Scattering Enhanced Photoacoustic Gas Spectroscopy with Disordered Porous Ceramics.

Light-gas interaction can be enhanced by using disordered porous materials because multiple random scattering increases light intensity near the surface of the material. Here we report signal enhancement of photoacoustic gas spectroscopy with disordered porous ceramics. The amplitude and frequency characteristics of photoacoustic signal due to gas absorption in disordered materials are modeled theoretically.

Ultrasensitive terahertz modulation by silicon-grown MoS2 nanosheets.

Two-dimensional (2D) materials play more and more important roles these days, due to their broad applications in many areas. Herein, we propose an optically-pumped terahertz (THz) modulator, based on Si-grown MoS2 nanosheets. The broadband modulation effect has been proved by THz time domain spectroscopy and numerical simulation.

Photonic crystal fiber modal interferometer based on thin-core-fiber mode exciter.

A thin-core-fiber excited photonic crystal fiber modal interferometer has been proposed and experimentally demonstrated. By employing a thin-core fiber as the mode exciter, both of the core and cladding modes propagate in the photonic crystal fiber and interfere with each other. The experimental results show that the transmission dips corresponding to different-order modes have various strain responses with opposite shift directions.

Synthesis of Large-Area Highly Crystalline Monolayer Molybdenum Disulfide with Tunable Grain Size in a H2 Atmosphere.

Large-area and highly crystalline monolayer molybdenum disulfide (MoS2) with a tunable grain size was synthesized in a H2 atmosphere. The influence of introduced H2 on MoS2 growth and grain size, as well as the corresponding mechanism, was tentatively explored by controlling the H2 flow rate. The as-grown monolayer MoS2 displays excellent uniformity and high crystallinity evidenced by Raman and high-resolution transmission electron microscopy.

Low-temperature cross-talk magnetic-field sensor based on tapered all-solid waveguide-array fiber and magnetic fluids.

A compact fiber-optic magnetic-field sensor based on tapered all-solid waveguide-array fiber (WAF) and magnetic fluid (MF) has been proposed and experimentally demonstrated. The tapered all-solid WAF is fabricated by using a fusion splicer, and the sensor is formed by immersing the tapered all-solid WAF into the MF. The transmission spectra have been measured and analyzed under different magnetic-field intensities.

Highly sensitive twist sensor employing Sagnac interferometer based on PM-elliptical core fibers.

A highly sensitive optical fiber twist sensor has been proposed by employing a Sagnac interferometer based on polarization-maintaining elliptical core fibers (PM-ECFs). The twist effects have been theoretically analyzed and experimentally demonstrated. Based on the photoelastic effect, the resonance wavelength linearly shifts with the increment of twist and the wavelength shift is also dependent on the torsion direction.

Magnetically controllable wavelength-division-multiplexing fiber coupler.

In this paper, a magnetically controllable wavelength-division-multiplexing (WDM) fiber coupler has been proposed and experimentally demonstrated. A theoretical model has been established to analyze the influences of the weak as well as strong couplings to the wavelength tunability of this coupler. Experimental results show that the operation wavelength tunability of the proposed WDM coupler could be fulfilled for an applied magnetic field intensity range of 0 Oe to 500 Oe, and particularly it possesses high operation performances within the magnetic field intensity ranging from 25 Oe to 125 Oe when additional transmission loss and isolation are both considered.

Liquid-filled photonic-crystal-fiber-based multimodal interferometer for simultaneous measurement of temperature and force.

In this paper, a multimodal interferometer based on the liquid-filled photonic crystal fiber (PCF) has been proposed and experimentally demonstrated for simultaneous measurement of temperature and force. Experimental results show that different spectral minima have distinctive sensitivities to the temperature and force. The proposed interferometer shows the temperature sensitivities of -9.

Temperature-insensitive optical fiber refractometer based on multimode interference in two cascaded no-core square fibers.

A temperature-insensitive optical fiber refractometer, based on multimode interference in no-core square fibers, has been proposed and experimentally demonstrated. The refractometer is formed by a single-mode fiber sandwiched between two segments of no-core square fibers through cleaving and fusion splicing. The transmission spectra characteristic of refractive index (RI) and environmental temperature have been investigated.

Tunable optical and magneto-optical properties of ferrofluid in the terahertz regime.

The dielectric property and magneto-optical effects of ferrofluids have been investigated in the terahertz (THz) regime by using THz time-domain spectroscopy. The experiment results show that the refractive index and absorption coefficient of ferrofluid for THz waves rise up with the increase of nanoparticle concentration in the ferrofluid. Moreover, two different THz magneto-optical effects have been found with different external magnetic fields, of which mechanisms have been theoretically explained well by microscopic structure induced refractive index change in the magnetization process and the transverse magneto-optical effect after the saturation magnetization, respectively.

Magnetic field tunability of optical microfiber taper integrated with ferrofluid.

Optical microfiber taper has unique propagation properties, which provides versatile waveguide structure to design the tunable photonic devices. In this paper, the S-tapered microfiber is fabricated by using simple fusion spicing. The spectral characteristics of microfiber taper integrated with ferrofluid under different magnetic-field intensities have been theoretically analyzed and experimentally demonstrated.

Load-insensitive temperature sensor based on azobenzene-chloroform-solution-filled microstructured optical fiber.

A solid-core microstructured optical fiber is infiltrated with the Dispersed Yellow 7 and chloroform mixture solution, resulting in the appearance of several transmission dips with different temperature and axial load responses. The temperature- and load-dependent spectral characteristics of these dips have been investigated and the experimental results indicate that they are pretty temperature-sensitive, but insensitive to the variation of applied axial load. Such a compact fiber-optic device with electric perturbation immunity could be employed for load-insensitive temperature sensing with high sensitivity.

Multi-mode interferometer-based twist sensor with low temperature sensitivity employing square coreless fibers.

An all-fiber twist sensor based on multimode interferometer (MMI) has been proposed and fabricated by splicing both ends of a section of square no-core fiber (NCF) with a single mode fiber. We have investigated the transmission spectral characteristics of the square fiber under different applied twisting angles. Within a torsion angle range of -360°~360°, the wavelength and transmission sensitivities are 1.

A reflective photonic crystal fiber temperature sensor probe based on infiltration with liquid mixtures.

In this paper, a reflective photonic crystal fiber (PCF) sensor probe for temperature measurement has been demonstrated both theoretically and experimentally. The performance of the device depends on the intensity modulation of the optical signal by liquid mixtures infiltrated into the air holes of commercial LMA-8 PCFs. The effective mode field area and the confinement loss of the probe are both proved highly temperature-dependent based on the finite element method (FEM).

Agarose gel-coated LPG based on two sensing mechanisms for relative humidity measurement.

A relative humidity (RH) sensor based on long-period grating (LPG) with different responses is proposed by utilizing agarose gel as the sensitive cladding film. The spectral characteristic is discussed as the ambient humidity level ranges from 25% to 95% RH. Since increment of RH will result in volume expansion and refractive index increment of the agarose gel, the LPG is sensitive to applied strain and ambient refractive index; both the resonance wavelength and coupling intensity present particular responses to RH within two different RH ranges (25%-65% RH and 65%-96% RH).