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A distributed pressure sensor is proposed and designed for dynamic pressure measurement by using frequency-agile fast Brillouin optical time-domain analysis (BOTDA). A double coated single-mode fiber (SMF) is used as the sensing fiber because of its 1500- $\mu \text{m}$ thickness outer coating that can significantly improve the dependence of the Brillouin frequency shift on pressure. Then, the frequency-agile technique is used to generate frequency-agile pump pulse in BOTDA system so that a fast Brillouin gain spectrum distribution measurement can be achieved. An injection locked scheme is used as both optical filter and optical amplifier to improve the measurement accuracy. As a result, the static pressure sensitivity of the double coated fiber is −3.46 MHz/MPa with the pressure ranging from 0 to 30 MPa. Subsequently, a large dynamic range pressure measurement is performed with a sampling rate of 33.3 kHz and maximum sensing distance of 25 m. Furthermore, it is proved that the uncertainty of dynamic pressure measurement system is 0.03 MPa.

Fiber Fabry-Perot (FP) sensor, as an optical sensor with simple structure and the most application fields, has attracted a lot of attention in recent decades, but it also faces the difficulty of multiplexing. In this paper, we propose and demonstrate a novel multiplexing method of FP sensor with multi-branch configuration interrogated with frequency modulated continuous wave interferometry. By an algorithm based on Fourier transform, the sub-sensors are addressable and their interference spectrum can be demodulated independently. For demonstration, the quasi-distributed refractive index (RI) sensing experiment is realized. The experiment results inherit high RI sensitivity of the traditional FP sensor around 1200 nm/RIU and high RI resolution smaller than 5 × 10−6 RIU. Besides, thanks to the advantage of coherence detection, the spectrum can be demodulated from the reflection signal of

We propose and demonstrate a frequency modulated continuous-wave (FMCW) light detection and ranging (LiDAR) system, which employs double-sideband modulation combining with injection-locking to generate triangular linear frequency modulation light source. A fiber laser working as master laser is modulated by a Mach-Zehnder modulator to produce two first-order sidebands with tuning range of 8–14 GHz, one of which is extracted and amplified by a slave distributed feedback laser. A large carrier suppression ratio up to 20 dB is realized. The experiment results show the spatial resolution of the proposed LiDAR is 2.5 cm, equaling to the theoretical value. The velocity measurement is also performed by extracting Doppler shift. Finally, by combining the proposed LiDAR with 2-axis mechanical galvanometer scanner, the 3D imaging with high precision is realized, and the real scene is well restored. The proposed LiDAR system realizes pure linear frequency modulation without complex linearization algorithm or clock sampling circuit, and has advantages of simple structure and high precision.

A high-sensitivity distributed temperature sensor based on Brillouin scattering is theoretically proposed and experimentally demonstrated. Double-coated single-mode fibers (SMF) are used as sensing fibers to improve the temperature sensitivity of Brillouin frequency shift (BFS). The thermomechanical model of double-coated fiber based on Lame formula is established, and the reasons for improving the BFS temperature sensitivity are analyzed. In the simulation, the BFS temperature sensitivity is improved with increasing of outer coating thermal expansion coefficient, Young’s modulus, and radius, but the effect of Poisson’s ratio can be ignored. In the experiment, four kinds of optical fibers are designed to verify the theoretical results, including a single-coated fiber and three double-coated fibers. The outer coating radii of double-coated fibers are $450~\mu \text{m}$ , $1000~\mu \text{m}$ and $1500~\mu \text{m}$ , respectively. The BFS temperature sensitivity of these fibers are calculated to be 1.07 MHz/°C, 3.28 MHz/°C, 4.57 MHz/°C and 6.04 MHz/°C within the temperature range of −30 to 40 °C, respectively. With a spatial resolution of 1.5 m, the maximum BFS temperature sensitivity of the double-coated SMFs is measured, which is about 6 times higher than that of single-coated SMF, achieving a maximum measurement error less than 0.05 °C.

Objective: DNA copy number alterations and difference expression are frequently observed in ovarian cancer. The purpose of this way was to pinpoint gene expression change that was associated with alterations in DNA copy number and could therefore enlighten some potential oncogenes and stability genes with functional roles in cancers, and investigated the bioinformatics significance for those correlated genes. Method: We obtained the DNA copy number and mRNA expression data from the Cancer Genomic Atlas and identified the most statistically significant copy number alteration regions using the GISTIC. Then identified the significance genes between the tumor samples within the copy number alteration regions and analyzed the correlation using a binary matrix. The selected genes were subjected to bioinformatics analysis using GSEA tool. Results: GISTIC analysis results showed there were 45 significance copy number amplification regions in the ovarian cancer, SAM and Fisher’s exact test found there have 40 genes can affect the expression level, which located in the amplification regions. That means we obtained 40 genes which have a correlation between copy number amplification and drastic up- and down-expression, which p-value ere overlapped with the several published studies which were focused on the gene study of tumorigenesis. Conclusion: The use of statistics and bioinformatics to analyze the microarray data can found an interaction network involved. The combination of the copy number data and expression has provided a short list of candidate genes that are consistent with tumor driving roles. These would offer new ideas for early diagnosis and treat target of ovarian cancer.

Purpose: This study aims to evaluate the treatment plans of Volumetric-modulated arc therapy (VMAT) and intensity-modulated radiation therapy (IMRT) techniques for cervical-thoracic esophageal cancers. Methods and Materials: Sixty patients were retrospectively identified. Several parameters were evaluated based on target conformity and dose-volume histograms of organs at risk (lung, spinal cord, and heart). A phantom for time comparison was also assessed for each plan. Results: The IMRT plans (5f-IMRT: V95% = 99.4 ± 0.3, 7f-IMRT: V95% = 99.8 ± 0.1) results in better PTV coverage than RA plans (Single-arc: V95% = 95.8 ± 3.2, Double-arc: V95% = 95.4 ± 2.3). The target dose conformity of the 5f-IMRT plan was inferior to all plans (CI = 70.4 ± 7.1). The Single-arc plan achieved the best conformity (CI = 72.5 ± 4.6), whereas the Double-arc plan (CI = 72.1 ± 5.1) was slightly inferior to the Single-arc plan but superior to the 7f-IMRT plan (CI = 71.7 ± 8.6). The total MU was reduced by 42.1% in VMAT plan. The average MU needed to deliver the dose of 60 Gy for Single-arc (423.5 ± 52.1 MU) was found to be the least. Similarly, the average MU for the 5f-IMRT, 7f-IMRT and Double-arc were 868.2 ± 182.0 MU, 870.0 ± 225.3 MU and 548.8 ± 47.2 MU, respectively. The delivery time in VMAT plans was reduced from 193.8 seconds to 99.2 seconds by around 48.8% compared to IMRT plans. Conclusion: For similar PTV parameters, VMAT delivers a lower dose to organs at risk than IMRT in a shorter time, and this has warranted clinical implementation.

Purpose: Verified the delivered dose distribution of lung cancer Stereotactic Body Radiotherapy (SBRT) using the cone-beam CT images. Methods: Twenty lung cancer patients who underwent SBRT with 100 CBCT images were enrolled in this study. Delivered dose distributions were recalculated on CBCT images with the deformed and non-deformed methods, respectively. The planned and delivered dose distributions were compared using the dose-volume histograms. Results: The delivered target coverage (V100) per patient inside target volume deviated on average were 0.83% ± 0.86% and 1.38% ± 1.40% for Pct vs. Pcbct and Pct vs. Pdcbct, respectively. The Conformity Index (CI) and Gradient Index (GI) showed a good agreement among the plans. For the critical organs, only minor differences were observed between the planned dose and the delivered dose. Conclusions: CBCT images were a useful tool for setup and dose delivery verification for lung cancer patients who underwent SBRT.

We propose a high-sensitivity dynamic distributed pressure sensor using frequency-scanning phase-sensitive optical time-domain reflectometry (φ-OTDR) in a single-mode fiber (SMF), where an injection locking laser working as both filter and amplifier is used to generate the multi-frequency signals under a double-sideband modulation. The pressure sensitivity of the SMF is measured to be 702.5 MHz/MPa, which is approximately 1000 times larger than that of the Brillouin optical time-domain analysis technique. Subsequently, a dynamic pressure experiment is carried out in the case of rapid pressure relief from 2 to 0 MPa so that a maximum sampling rate of 33.3 kHz for a 25-m SMF is achieved, and the measurement uncertainty of 0.61 kPa for the proposed scheme is demonstrated.

A sensitivity-enhanced distributed hydrostatic pressure sensor based on Brillouin optical time domain analysis (BOTDA) technique is theoretically proposed and experimentally demonstrated, where double-layer polymer coatings are used on the single-mode fibers (SMF) to enhance the hydrostatic pressure sensitivity. The pressure-induced strain model of multilayer coated fibers based on Lame formula is established to analyze the enhancement mechanism of pressure sensitivity of Brillouin frequency shift (BFS). Simulation results show that BFS pressure sensitivity can be enhanced by increasing the outer coating radius or by decreasing the outer coating Young's modulus and Poisson's ratio. Four types of optical fibers are designed including single-coated and double-coated fibers to verify theoretical results, where the outer coating radius of double-coated fibers are 450, 1000, and 1500 μm, respectively. Experimental results show that the BFS pressure sensitivity are −0.75 MHz/MPa, −1.65 MHz/MPa, −2.66 MHz/MPa and −3.61 MHz/MPa in the range of 0–30 MPa after temperature compensation for above four kinds of fibers, respectively. The maximum pressure sensitivity is measured about five times higher than single-coated SMF, and the maximum measurement error of pressure sensing system is less than 0.09 MPa with a spatial resolution of 1.5 m.

Brillouin-based optical fiber sensors have been developed over the past few years and played a significant role for distributed temperature and strain measurements, which include many properties such as high measurement accuracy, large measurement range and environmental suitability. Among these sensors, Brillouin optical fiber sensors via optical chirp chain (OCC) become an ideal choice for ultrafast distributed measurement to distinguish quick-changing events in practical applications. This paper begins with the introduction of the concept and the generation schemes of OCC, the spectra distortion characteristic of OCC Brillouin signal are analyzed. The efforts towards such OCC based Brillouin optical fiber sensing for ultrafast measurement are reviewed here as well, with the OCC based Brillouin optical time domain analysis and the OCC based Brillouin optical time domain reflectometry, which give distinguished performance for dynamic measurement, long distance measurement and one end access measurement. Meanwhile, the consequent future challenges of OCC based distributed sensing are discussed and presented, such as as high spatial resolution and high accuracy measurement.

We proposed a temperature-compensated distributed refractive index (RI) sensor using an etched multi-core fiber (MCF) in optical frequency domain reflectometry. The MCF contains inner and outer cores and is etched until the outer core is exposed. Therefore, the outer core can be used for distributed RI sensing, and the inner core can be used for temperature compensation. The sensing length of 19 cm and the spatial resolution of 5.3 mm are achieved in the experiment. The RI sensing range is as wide as 1.33–1.44 refractive index units (RIU), and the maximum sensitivity of 47 nm/RIU is obtained around 1.44 RIU. Additionally, the temperature sensitivity is 9.8 pm/°C. Using this sensor, we successfully detected the glycerol diffusion process in water.

We proposed a multiplexing method of optical fiber Fabry-Perot interferometer (FPI) for multi-point refractive index (RI) sensing application. This method is based on the frequency modulated continuous wave (FMCW) interferometry, in which a series of FPIs are connected by fiber couplers as like the bus-structure. Due to the spatial difference among FPIs, the reflection signals from different FPIs can be separated in spatial domain by Fourier transform. Applying inverse Fourier transform, the interference spectra of every FPIs can be demodulated independently in wavelength domain. Three FPIs are multiplexed for verifying the multi-point RI sensing ability of the proposed method. The experimental results show that the proposed multiplexing method performs well in multi-point RI sensing applications. In the RI range of 1.3334~1.3410, the RI sensitivities of the multiplexed FPIs are as high as 1200 nm/RIU, and the RI measurement accuracies are as high as 5×10-6 RIU. In addition, the sensing system can demodulate the interference spectrum from the reflected signal as low as 5 pW. When the light source power is 3.2 mW, the theoretical maximum multiplexing number is 8000. This work provides an efficient solution for multi-point RI sensing.

We provided an effective method that optical fiber surface plasmon resonance (SPR) can be used to displacement measurement. By fabricating a Kretschmann configuration on a micro-structure fiber which is produced by splicing a short segment of graded-index fiber (GIF) with a plastic-clad silica (PCS), we made a novel micro-displacement sensor. We employed a single-mode fiber (SMF) to change the radial position of the incident beam as the displacement. In the GIF, the angle between light beam and fiber axis, which is changed by the displacement, will lead to changes of resonance angle in the PCS. Thus the resonance wavelength shifts. The detection range of the proposed sensor is 0–25 μm; and its sensitivity is related to the refractive index (RI) of liquid surrounding in which the sensing zone is immersed (named cladding liquid). The higher the cladding liquid RI, the higher the sensitivity. Under cladding liquid RI of 1.41, the resonance wavelength redshifts from 801 nm to 839 nm when the displacement changes from 0 μm to 25 μm. When the displacement is close to 25 μm, the sensitivity reaches a maximum of 2.43 nm/μm, which transcends almost all of other optical-fiber micro-displacement sensors. The proposed micro-displacement sensor will have potential applications in high precision instruments.

We propose and demonstrate a dual-channel surface plasmon resonance (SPR) sensor based on a microstructured hollow fiber (MHF), which is available for microfluidic chips. Two channels contain an internal sensing channel inside of the MHF due to the hollow structure, and an external sensing channel outside of the MHF. We employ a fiber grinding-polishing & butt-jointing technology to configure the hollow fiber SPR sensing probe. We plate the gold coatings on the internal and external sensing channels with the thickness of 50 nm, respectively. When the refractive index of the testing samples is in the range of 1.333–1.385, the range of resonance wavelengths in the internal sensing channel is 712nm–1010 nm, and the range of resonance wavelengths in the external sensing channel is 618nm–700 nm. The testing sensitivity of the internal sensing channel is 5645 nm/RIU and testing sensitivity of the external sensing channel is 1576 nm/RIU. Due to the special structure of the MHF, where an air hole in the MHF, the hollow fiber SPR sensor has the superiority of being easy to be multiplexed in a microfluidic chip system.

We propose and demonstrate a novel dual-channel SPR refractive index sensor based on hetero-core structure fiber. For the traditional hetero-core structure fiber SPR sensor, the resonance wavelength range is unchangeable. We solve this issue by polishing the traditional hetero-core structure fiber as circular truncated cone shape. By this method, we can adjust the resonance wavelength range flexible by changing fiber polishing angle. With increasing of fiber polishing angle, the resonance wavelength range will red-shift. When fiber polishing angle is 14°, and refractive index range is from 1.333 to 1.385, the resonance wavelength range is from 754 nm to 965 nm, which is away from that of the traditional hetero-core structure fiber SPR sensor (600 nm to 700 nm). Therefore, we realize dual-channel sensing by wavelength division multiplexing technology. The sensitivity of two channels are 1980.77 nm/RIU and 4057.69 nm/RIU respectively. In addition, the resonance wavelength and sensitivity of the sensor have a well consistency no matter which working way we adopt. The proposed dual-channel SPR sensor has important applications for multiple analytes detection.

We propose and demonstrate a cascaded distributed multichannel fiber surface plasmon resonance (SPR) refractive index (RI) sensor by using a gold film coating thickness adjustment approach. For a multimode fiber-based SPR sensor, different gold film thicknesses produce different resonance wavelengths, different dynamic ranges, and even different testing sensitivities. Therefore, we design and fabricate a cascaded distributed two–channel multimode fiber SPR sensor with the gold film thickness of 30 nm in #1 sub–channel and 60 nm in #2 sub–channel. The corresponding testing sensitivities are 1712 nm/RIU and 3038 nm/RIU with the RI range of 1.333–1.385. The experimental results indicate that, in the range of 20nm–60 nm, the smaller is the gold film thickness, the larger is the RI testing range, and the lower is the testing sensitivity, and the deeper is the resonance dip. In addition, it is worthy to say that, the testing sensitivity and the dynamic range of the cascaded distributed multichannel fiber SPR sensor keep unchanged after multiple sensing sub-channels being cascaded–connected. By using the gold film thickness adjustment approach, we overcome the limit of adjusting and separating the dynamic ranges of the multichannel fiber SPR sensors effectively.

We proposed a novel temperature-compensated multi-point refractive index (RI) sensing system by the combination of the cascaded Fabry-Perot (FP) sensors and the frequency modulated continuous wave (FMCW) interferometry. The former is used for simultaneous sensing of RI and temperature, and the latter is used for multiplexing a series of the cascaded FP sensors to realize multi-point sensing. By means of Fourier transform-based algorithms, the interference spectra of each sub-FP sensors can be divided and demodulated independently. Experimentally, three cascaded FP sensors are multiplexed to verify multi-point RI and temperature sensing ability. RI sensitivity up to ∼1200 nm/RIU is obtained within RI range from 1.3330 to 1.3410, and temperature sensitivity up to ∼0.17 nm/°C is obtained within temperature range from 20 °C to 80 °C. The RI precision is as high as 10−5 RIU and the temperature precision is as high as 0.05 °C. In addition, the prospective multiplexing number could reach about 4000 estimated by the minimum detectable light power. The proposed sensing system has potential advantages in the practical applications that require a large number sensing points.

We propose and demonstrate a reflective-distributed surface plasmon resonance (SPR) sensor based on the twin-core fiber. Firstly, we study the effects of the fiber dual tapered (DT) probe grinding angle on the SPR dynamic range. The results show that for larger grinding angles, the resonance wavelength increases, resulting in a higher testing sensitivity. By using this method, we can make the sensor operate in an optimal waveband. Secondly, on the basis of the results above, we grind the DT probe to be an asymmetric wedge shape to configure two grinding angles (6° and 17°) to realize the distributed sensing. Results show that, with the refractive index detecting a range of 1.333–1.385, we can get two separated sensing zones, 591–715 nm and 729–966 nm, the testing sensitivity are 2385 nm/RIU and 4558 nm/RIU respectively. By using this method, we can detect multiple analytes in the same sensing area simultaneously, besides that we can also effectively compensate for the errors caused by background index interference, and the refractive index change resulting from the non-specific binding, or physical absorption and others. It worth to say that by using this method, we can adjust and control the resonance wavelength by changing the fiber grinding angle, while keeping the testing sensitivity is not reduced. For practical applications, this reflective distributed fiber-based sensor is much suitable for biochemical sensing, it has small size and can enter a small testing spaces (μm scale). The diameter of the twin-core fiber is the only 125 μm, which helps to be integrated into a micro-fluidic chip. In this paper, we integrate the fiber probe into an infusion needle to simulate blood vessels on-line monitoring.

Micro-displacement measurements play a crucial role in many industrial applications. Aiming to address the defects of existing optical-fiber displacement sensors, such as low sensitivity and temperature interference, we propose and demonstrate a novel surface plasmon resonance (SPR)-based optical-fiber micro-displacement sensor with temperature compensation. The sensor consists of a displacement-sensing region (DSR) and a temperature-sensing region (TSR). We employed a graded-index multimode fiber (GI-MMF) to fabricate the DSR and a hetero-core structure fiber to fabricate the TSR. For the DSR, we employed a single-mode fiber (SMF) to change the radial position of the incident beam as displacement. The resonance angle in the DSR is highly sensitive to displacement, thus, the resonance wavelength of the DSR shifts. For the TSR, we employed polydimethylsiloxane (PDMS) as a temperature-sensitive medium, whose refractive index is highly sensitive to temperature, thus, the resonance wavelength of the TSR shifts. The displacement and temperature detection ranges are 0&ndash, 25 &mu, m and 20&ndash, 60 &deg, C, the displacement and temperature sensitivities of the DSR are 4.24 nm/&mu, m and &minus, 0.19 nm/&deg, C, and those of the TSR are 0.46 nm/&mu, 2.485 nm/&deg, C, respectively. Finally, by means of a sensing matrix, the temperature compensation was realized.

Curvature measurement plays an important role in many fields. Aiming to overcome shortcomings of the existing optical fiber curvature sensors, such as complicated structure and difficulty in eliminating temperature noise, we proposed and demonstrated a simple optical fiber curvature sensor based on surface plasmon resonance. By etching cladding of the step-index multimode fiber and plating gold film on the bare core, the typical Kretschmann configuration is implemented on fiber, which is used as the bending-sensitive region. With increases in the curvature of the optical fiber, the resonance wavelength of the SPR (Surface Plasmon Resonance) dip linear red-shifts while the transmittance decreases linearly. In the curvature range between 0 and 9.17 m&minus, 1, the wavelength sensitivity reached 1.50 nm/m&minus, 1 and the intensity sensitivity reached &minus, 3.66%/m&minus, 1. In addition, with increases in the ambient temperature, the resonance wavelength of the SPR dips linearly blueshifts while the transmittance increases linearly. In the temperature range between 20 and 60 &deg, C, the wavelength sensitivity is &minus, 0.255 nm/&deg, C and the intensity sensitivity is 0.099%/&deg, C. The sensing matrix is built up by combining the aforementioned four sensitivities. By means of the dual modulation method, the cross-interference caused by temperature change is eliminated. Additionally, simultaneous measurement of curvature and temperature is realized.

We propose and demonstrate a novel optical-fiber micro-displacement sensor based on surface plasmon resonance (SPR) by fabricating a Kretschmann configuration on graded-index multimode fiber (GIMMF). We employ a single-mode fiber to change the radial position of the incident beam as the displacement. In the GIMMF, the angle between the light beam and fiber axis, which is closely related to the resonance angle, is changed by the displacement; thus, the resonance wavelength of the fiber SPR shifts. This micro-displacement fiber sensor has a wide detection range of 0–25 μm, a high sensitivity with maximum up to 10.32 nm/μm, and a nanometer resolution with minimum to 2 nm, which transcends almost all of other optical-fiber micro-displacement sensors. In addition, we also research that increasing the fiber polishing angle or medium refractive index can improve the sensitivity. This micro-displacement sensor will have a great significance in many industrial applications and provide a neoteric, rapid, and accurate optical measurement method in micro-displacement.

We propose a novel dual-channel Surface Plasmon Resonance (SPR) fiber sensors based on the incident angle adjusting method. By grinding fiber tip to form wedge-shape with different angles, we can easier adjust the incident angle in fiber, and then the SPR wavebands will change corresponding. The simulation and experiment demonstrate that the SPR wavebands will red-shift with increasing of the fiber grinding angle. Based on this, we cascade two fiber tips whose grinding angles are 5° and 15° respectively. Under the tests of the refractive index (RI) range from 1.333 to 1.385, the SPR wavebands are 576∼683nm and 677∼955nm respectively. Therefore, we can demodulate SPR signal by wavelength division multiplexing (WDM) technology. Sequentially, we can detect two analytes simultaneously. This dual-channel SPR fiber sensor has important significance in the fields of multichannel liquid refractive indices and temperature selfreference measurements.

We propose and demonstrate a novel and compact optical-fiber temperature sensor with a high sensitivity and high figure of merit (FOM) based on surface plasmon resonance (SPR). The sensor is fabricated by employing a single-mode twin-core fiber (TCF), which is polished as a circular truncated cone and coated with a layer of gold film and a layer of polydimethylsiloxane (PDMS). Owing to the high refractive index sensitivity of SPR sensors and high thermo-optic coefficient of PDMS, the sensor realizes a high temperature sensitivity of -4.13 nm/°C to -2.07 nm/°C in the range from 20°C to 70°C, transcending most other types of optical-fiber temperature sensors. Owing to the fundamental mode beam transmitting in the TCF, the sensor realizes a high FOM of up to 0.034/°C, more than twice that of SPR sensors based on multimode fiber. The proposed temperature sensor is meaningful and will have potential applications in many fields, such as biomedical and biomaterial.

We demonstrate a multiband background-free terahertz (THz) switch in photoactive chiral metamaterial using polarization conversion. Orthogonal arrangement of two asymmetrical split-ring apertures allows a high polarization conversion efficiency and low copolarization transmission. The chiral metamaterial embedded with photoactive silicon promises a dynamic control on cross-polarization transmission and thus enables an efficient background-free THz switch. The on/off state of THz metamaterial switching can be efficiently controlled by an optical pump. The realization of a cross-polarization THz switch provides a new mechanism of mode switching to control THz wave propagation and will be a promising candidate for polarization devices.

The problem of guaranteed-cost stabilization via static output feedback is studied. The guaranteed-cost stabilization controller is designed by using the static output feedback control strategy, Lyapunov stability theory, and SOS technique. It not only makes the closed-loop systems asymptotically stable for all possible uncertainties, but also satisfies certain quadratic performance index. The optimal guaranteed-cost stabilization controller via static output feedback and the minimum upper-bound of the quadratic performance index are obtained by solving the corresponding optimization problems. Finally, the simulations show the correctness and validity of the results.

We demonstrate a tunable terahertz (THz) switch in photoactive chiral metamaterial based on manipulating polarization conversion. The on/off state can be controlled by optical pump and the cross polarization conversion is as high as 96%.

We propose and demonstrate an effective method to adjust the dynamic range of a fiber surface plasmon resonance (SPR) sensor by introducing a multimode fiber-sensing probe with a dual-truncated-cone (DTC) structure. When the grind angle of the DTC structure increases, the dynamic range redshifts. Based on this result, we fabricate a quasi-distributed two-channel multimode fiber SPR sensor by cascaded-connecting a DTC-sensing probe of 14° grind angle and a traditional transmitted multimode fiber (TMF)-sensing probe in the same fiber. The corresponding sensitivities of two sensing probes are 3423.08 nm/RIU and 2288.46 nm/RIU. By using this quasi-distributed multichannel fiber SPR-sensing approach, we may improve the detecting accuracy by extracting, calibrating, and compensating for the signals caused by the nonspecific bindings, other physical absorptions, and temperature changes in detecting samples, truly achieving dynamic detection in real-time. The excellence of this multichannel fiber SPR sensor is that the sensitivity of each subchannel-sensing probe stays unreduced after it is cascaded-connected in the main-channel fiber; the sensor is based on the multimode fiber, which is inexpensive, accessible, and convenient to be universalized in applications.