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Graphene and hBN as two-dimensional materials with excellent optical properties can be combined with other materials. In this paper, graphene and hBN is sequentially deposited on the surface of the silicon-core fiber to serve as transverse magnetic (TM) or transverse electric (TE) mode polarizer alternatively depending on the input wavelength and the diameter of the silicon-core. The Gr/hBN stack structure on the surface silicon-core microfiber is used not only for enlarging the wavelength bandwidth, such as from 350 nm (TM) and 670 nm (TE) for double Gr/hBN stack to 300 nm (TM) and 550 nm (TE) for single Gr/hBN stack, but also enhancing the light-graphene interaction to multiply the polarization extinction ratio, as compared with that of monolayer graphene. Small radius silicon core could provide large light-graphene interaction for flat extinction ratio with different thickness of the hBN.

A coupled equivalent circuit for high-speed Si photodiodes is proposed, which is composed of a traditional resistance-capacitance-limited equivalent circuit and a carrier transit-limited equivalent circuit connected by a voltage controlled current source. All the resistances and capacitances in the carrier transit-limited equivalent circuit have physical meaning according to Laplace Transform. The proposed coupled equivalent circuit was applied to the Si p-i-n photodiodes and agreed well with the measured reflection coefficients and frequency response curves. Again, the minority carrier lifetime, diffusivity and interface state is verified to be the main limiting factors to the frequency response. This improved modeling can provide an effective way to design high speed photodiodes.

The 4.2% mismatch at the Si/Ge interface has a significant impact on Si/Ge photodetectors. However, few researchers have attempted to determine the major noise source or study the effects of the Si/Ge interface on the dark current, the responsivity and the 3-dB bandwidth of these devices. In this letter, we found that the dark current was dominated by generation-recombination processes that were enhanced by trap-assisted-tunneling around the interface below 220 K, with a characteristic tunneling energy of $E_{00}=14$ meV corresponding to an effective mass of $m^{*}=18m_{0}$ . This behavior can be explained by the rise in the heavy-hole band caused by the compressive strain on the Ge layer. When the temperature increased above 240 K, Shockley-Read-Hall recombination was clearly observed and believed to be dominant. The responsivity, the collection efficiency and the absorption efficiency were all extracted at 850 nm, 1310 nm, and 1550 nm. The absorption coefficient around the interface was found to be lower than that of the bulk material. In addition, comparison of the measured 3-dB frequency (~20.6 GHz @ −0.5 V) with the theoretical value (~29.37 GHz) indicated that defects have little effect on the bandwidth at high frequencies.

Graphene-microfiber with the advantage of graphene material and microfiber has been hailed as a wonderful optical waveguide. In this paper, its fabrication, optical properties and applications have been presented. Here, we present our recent progress in the graphene-microfiber waveguides from photonic devices, e.g., optical polarizers and optical modulators to mode-locking in fiber laser. With the novel nanotechnology emerging, graphene-microfiber could offer new possibilities for the future optic circuits, systems and networks.

Photodetection with high responsivity at the wavelength of 1060 nm is highly desirable for light detection and ranging (LiDAR) as well as the recent emergence of swept-source optical coherent tomography (SS-OCT) applications. However, the absorption coefficient $\alpha $ of Si material at 1060 nm under the bias of 0 V is very low due to its approach to the absorption bandgap edge of Si material. In this letter, the carrier-collection-enhanced structure is proposed, which functions as multiple carrier collection paths, which enhances the external quantum efficiency of photodiodes. An efficient Si photodiode with responsivity of 0.49 A/W at 1060 nm at 0 V is demonstrated, which is 2.5 times of that of commercial products. The cost-effective fabrication of Si photodiodes greatly enhances the system performance of LiDAR and OCT.

We explored whether red blood cell distribution width (RDW), a routinely checked item of complete blood cell counts, was an indicator of long-term euglycemia remission in patients with type 2 diabetes after short-term continuous subcutaneous insulin infusion (CSII).We analyzed the original data of patients enrolled in three randomized control trials from 2002 to 2014. CSII was administered to drug-naїve patients with newly diagnosed type 2 diabetes to achieve and maintain euglycemia for 2weeks.A total of 185 patients were involved and 98 patients (52.97%) who achieved and maintained euglycemia for at least 12months were classified as the remission group, and the others as the non-remission group. Patients in remission group had a relatively lower value for baseline RDW (38.82±2.76vs 39.89±2.78fL, p=0.017) compared with those in non-remission group. A graded decrease of remission rate (67.50%, 55.00%, 53.66% and 30.77% for Quartile 1 to Quartile 4 respectively, P0.05) was observed with the increasing of RDWs. The risk of hyperglycemic relapse was significantly increased for those in the highest quartile compared with the lowest (hazard ratio=2.68; 95% CI, 1.38-5.22). Those who achieved euglycemia within 7days or obtained a better fasting glucose after therapy had preferable remission rates.Patients with lower baseline RDWs are more likely to maintain a one-year euglycemia remission after short-term CSII. A faster normalization of glucose during treatment and a lower fasting glucose after therapy are correlated with a long-term glucose control.

In this study, the welding-brazing process of pulsed double electrode gas metal arc welding (pulsed DE-GMAW) provides a potential method to join dissimilar metals (i.e., joining of aluminum alloys to galvanized mild steel). In order to evaluate the stability of welding process, a mathematical model of the alternation of droplet transfer for the pulsed DE-GMAW is established based on the spring-mass-damper model. The droplet alternative transfer is a free flight with short circuiting transfer mode, which is analyzed and detected during the welding process with double pulsed current. Meanwhile, the pulsed DE-GMAW technology is found to be feasible to join the aluminum alloys to the galvanized mild steel. The variable weldability process of aluminum-galvanized steel could be obtained with a wire by optimizing welding parameters. Microstructures of the intermetallic reaction layer and bonding mechanism of optimized weld-brazed specimens with aluminum ER4043 and ER5356 wires are analyzed and conducted by SEM and tensile test.

Monolayer pentagonal silicon dicarbide is a 2D material composed entirely of pentagons, and it possesses novel electronic properties possibly leading to many potential applications. In this paper, using first-principles calculations, we have systematically investigated the electronic, mechanical and transport properties of monolayer penta-SiC2 by strain-engineering. By applying in-plane tensile or compressive strain, it is possible to modulate the physical properties of monolayer penta-SiC2, which subsequently changes the transport behaviour of the carriers. More interestingly, at room temperature, the uniaxial compressive strain of −8% along the a-direction can enhance the hole mobility of monolayer penta-SiC2 along the b-direction by almost three orders of magnitude up to 1.14 × 106 cm2 V−1 s−1, which is much larger than that of graphene, while similar strains have little influence on the electron mobility. The ultrahigh and strain-modulated carrier mobility in monolayer penta-SiC2 may lead to many novel applications in high-performance electronic and optoelectronic devices.

Silicon PIN photodiodes in the visible wavelength range have been widely applied in aerospace, defense, security, medical, and scientific instruments because of their high sensitivity and low cost. In this paper, the phenomena of the current kink and the capacitance frequency dispersion are observed. Contamination at the p-type Ohmic contact interface is proposed to explain the current kink effect and capacitance frequency dispersion, according to the temperature-dependent I-V measurement results in which trap-assisted tunneling process demonstrated.

Graphene-microfiber with the advantage of graphene material and the microfiber has been hailed as a wonderful waveguide in optics. A tutorial introduction to the graphene-microfiber (GMF) waveguides including the effect of graphene on waveguide, fabrication and applications has been presented. Here, we reviewed recent progress in the graphene waveguides from mode-locking and Q-switching in fiber laser to gas sensing and optical modulation. A brief outlook for opportunities and challenges of GMF in the future has been presented. With the novel nanotechnology emerging, GMF could offer new possibilities for future-optic circuits, systems and networks.

Graphene, as two-dimensional material with many properties of the gate-voltage tunable Fermi-level and zero band gap, can be utilized for optical modulators by the integration with other material. In this work, an electro-optic modulator based on the fiber-surface waveguide and graphene capacitance has been proposed with the device length of 50 μm, featuring excellent controllable polarization modulation (polarization extinction ratio over 0.12 dB/μm), large modulation bandwidth of ∼40 GHz @ hBN and ∼25 GHz @ Al2O3, and energy consumption low to 11.5 pJ/bit for hBN and 4 pJ/bit for Al2O3. The polarization can be controlled by tuning the core radius from 130 nm for the TE polarized modulation with modulation efficiency over ∼2.56 dB V−1 (Al2O3) and ∼1.15 dB V−1 (hBN) to 170 nm for the TM polarized modulation efficiency up to ∼3.03 dB V−1 (Al2O3) and ∼1.3 dB/V (hBN). This work not only promotes the development of future polarization modulation technology, but also paves the way toward multifunctional fiber devices and systems.

Flexible light-emitting diodes (LEDs) are highly desired for wearable devices, flexible displays, robotics, biomedicine, etc. Traditionally, the transfer process of an ultrathin wafer of about 10–30 μm to a flexible substrate is utilized. However, the yield is low, and it is not applicable to thick GaN LED chips with a 100 μm sapphire substrate. In this paper, transferable LED chips utilized the mature LED manufacture technique are developed, which possesses the advantage of high yield. The flexible LED array demonstrates good electrical and optical performance.

For exploring a strong electro-optic effect from a graphene/hexagonal boron nitride (hBN) structure, here a comprehensive study for investigating the integrated broadband graphene/hBN modulators has been presented. Two representative configurations with a S i 3 N 4 waveguide were compared, focusing on optimizing the hBN thickness, waveguide width and height, and graphene size to balance their performances. It was found that 200 µm long devices with 65 nm hBN thickness allow for ∼ 80 G H z modulation bandwidth, 35.4 dB extinction ratio, and over 700 nm operation spectral range. Compared to the ridge S i 3 N 4 waveguide, the buried S i 3 N 4 waveguide was more suitable as an optical waveguide for the graphene/hBN modulator to obtain a large modulation depth of ∼ 0.17 d B µ m and a large operation spectral range from 750 to ∼ 1640 n m .

Two-dimensional (2D) nano-structured tin monoxide (SnO) offers fascinating possibilities as anode material for lithium ion batteries (LIBs). 2D architectures of SnO are highly desirable to access advanced lithium storage properties however their application is impeded by the lack of synthetic method. In this study, we report a scalable synthetic route to facilely deriving SnO/pristine-graphene (p-G) 2D-2D heterostructure from bulk SnO and graphite. A “top-down” synthetic method was found effective in transforming SnO micro-sized particles into nanosheets down to a few nanometers in thickness. Assembled with pristine graphene (p-G), the SnO nanosheets were used to build a SnO/p-G heterostructure that delivers remarkable Li-ion storage performances: reversible capacities of 633.9 mAh g−1 after 100 cycles at 0.05 A g−1, and excellent cycling stabilities (0.027% capacity fade per cycle at 1 A g−1 after 700 cycles) were obtained. In comparison, raw SnO exhibited severe SEI over-growth and continuous capacity decay from the on-set at 0.05 A g−1. The structural advantages of 2D-2D heterostructure were elucidated to understand its exceptional lithium storage properties. This study demonstrates a facile and scalable strategy for producing 2D-2D heterostructures from low-cost bulk materials for LIBs application.

In this work, we explore the possibility of using hybrid graphene/GaN phototransistors to get high responsivity, high speed, and large photosensitive area. The responsivity of our hybrid graphene/GaN phototransistors with a relatively large 15.2 mm2 active area reaches 361 mA/W at 10 V and the response time is ~5 ms, much better performance than traditional GaN photodetectors. This is because graphene acts as the carrier transport channel with a high mobility and greatly increases the charge collection efficiency. Our results should shed more light on the role of graphene in hybrid phototransistors and open a feasible pathway to develop large area ultraviolet photodetectors with high responsivity and high speed.

This study analyses electromagnetic interference (EMI) noise sources generated from a new type of flyback converter which is operated from a self-supplied power control integrated circuit (IC). On the basis of analysis, a new analytical mathematical model of common-mode (CM) EMI noise path is presented. This model is easier to construct and allows researchers to better understand the impact of each parameter on CM EMI noise than former models. According to the proposed model, the capacitors from the traces connected to the ground (GND), voltage drain drain (VDD), current sense (CS) and feedback (FB) pins to the ground demonstrate the greatest impact on CM EMI. Two improved layouts are designed to verify the analysis result. The layouts were driven by the newly developed model. Test results show that they correspond with theoretical calculations supporting the analysis and the model that was developed in the course of this work.

An Ldi/dt effect model in the float ground driver system of plasma display panel (PDP) is established. First, considering key parasitic parameters, this study analyses the Ldi/dt effect appeared in power supply and ground pins because of switching transition of float-ground integrated circuits. Second, a set of differential equations model is described and validated with a good agreement with experiments. Based on the model, time-domain transient voltages and frequency spectra of the Ldi/dt effect are simulated and analysed with different values of parameter elements. Finally, subject to system demand limitation and the proposed model, the manual parameter design for reducing the Ldi/dt effect is presented, and a PDP system is used to validate the proposed approach.

An absorption-adjustable graphene saturable absorber is used in a simple fiber laser system for an active control of the pulse-width of optical pulses. Such a saturable absorber is created by tightly attaching the graphene film onto the upper surface of the microfiber, thus an enhanced evanescence-field interaction between the propagating light along the microfiber length and graphene can be achieved. By tuning the polarization state of the light beam launched into the saturable absorber from TE to TM mode, the pulse-width of the pulses is varied between ~ 9.24 and ~ 2.32 ps.

Graphene has attracted a lot of research interest, especially as a saturable absorber (SA). However, improvement on thermal damage threshold is critical for the SA. Here, graphene covered on the microfiber is developed for this purpose by use of the light-graphene interaction via the evanescent field of the guided mode in the microfiber. Such interaction is numerically studied by using the theory of the electromagnetic field. Theoretical and experimental results indicate that graphene covered on the upper surface of the microfiber can be used as a polarization-dependent SA as well as an optical polarizer. When the radius size of the microfiber is down to 0.8 μm, its polarization extinction ratio is up to ~27 dB. When the radius of microfiber is up to ~3 μm, a polarization-dependent SA can be obtained with high thermal damage threshold of ~975.82 MWcm-2 for p -polarization and ~1233.2 MWcm-2 for s-polarization, and its polarization-dependent modulation depth varies from ~10.25% to ~12.85%.

This paper presents a method for detecting the heat-dissipation capability of the slow-wave structure (SWS) in a helix traveling wave tube (TWT) using an external heat source. This method utilizes transient temperature rise detection technology and structure function method to nondestructively detect the heat-dissipation capability of SWS. An analytical model is built, and the method is verified by using the simulation tool ANSYS. Furthermore, a dedicated test probe is designed based on this method, and a 2.5-mm diameter helix TWT is measured. The results reveal that the method can effectively detect parts with large thermal resistance in SWS, thereby providing the basis for eliminating the failure products and improving the production process of SWS.

Broadband and omnidirectional antireflection coating is generally an effective way to improve solar cell efficiency, because the destructive interference between the reflected and incident light can maximize the light transmission into the absorption layer. In this paper, we report the incident quantum efficiency ηin, not incident energy or power, as the evaluation function by the ant colony algorithm optimization method, which is a swarm-based optimization method. Also, SPCTRL2 is proposed to be incorporated for accurate optimization because the solar irradiance on a receiver plane is dependent on position, season, and time. Cities of Quito, Beijing and Moscow are selected for two- and three-layer antireflective coating optimization over λ = [300, 1100] nm and θ = [0°, 90°]. The ηin increases by 0.26%, 1.37% and 4.24% for the above 3 cities, respectively, compared with that calculated by other rigorous optimization algorithms methods, which is further verified by the effect of position and time dependent solar spectrum on the antireflective coating design.

Vertical cavity surface emitting lasers (VCSELs) are widely used in optical communications and optical interconnects due to their advantages of low threshold, low power consumption and so on. Wet nitrogen oxidation technology, which utilizes H2O molecules to oxidize the Al0.98Ga0.02As, is used for electrical and optical mode confinement. In this paper, the effects of oxidation time, oxidation temperature and oxidation anisotropy on the oxidation rate are explored and demonstrated. The ratio of oxidation rate on [0–11] to [011] crystal orientation is defined as oxidation anisotropy coefficient, which decreases with the increase of oxidation temperature and oxidation time. In order to analyze the effect of the oxidation anisotropy on the VCSEL performance, an oxide-aperture of the VCSELs with two difference shapes is designed and then fabricated. The static performance of these fabricated VCSELs has been measured, whose threshold current ratio ~ 0.714 is a good agreement with that of the theoretical calculation value ~ 0.785. Our research on wet nitrogen oxidation and its anisotropy serves as an important reference in the batch fabrication of large-area VCSELs.

An analytical model is proposed to analyse the energy recovery circuit (ERC) efficiency of plasma display panel (PDP) data driver integrated circuit (IC). The experimental measurements agree with the analysis results very well. The analysis results show that the ERC efficiency of PDP data driver IC is influenced by three factors: the value of charge time T ERC , the channel resistor R on and the capacitance of C L . The range of T ERC is restricted in actual PDP system. C L is determined by physical parameters of PDP panel, and its value is nearly changeless. Therefore the ERC efficiency of PDP data driver IC can be improved significantly by using superior DPLD (double-channel p-type lateral extended drain metal oxidesemi conductor) transistor that has smaller R on .

Graphene with zero-band gap can be easily saturated under strong excitation due to Pauli blocking. In this work, the graphene oxide membrane is reduced on the surface of microfiber by use of high temperature heating. Such reduced graphene oxide can interact with the strong evanescent field of the microfiber and enable saturable absorption in passively mode-locked fiber laser. The system can be effectively utilized to directly generate ultra-wide-band doublet pulses for high-capacity wireless communication applications.

In this paper, robotic reposition error measurement method based on laser interference remote positioning is presented, the geometric error is analyzed in the polishing system based on robot and the mathematical model of the tilt error is presented. Studies show that less than 1 mm error is mainly caused by the tilt error with small incident angle. Marking spot position with interference fringe enhances greatly the error measurement precision, the measurement precision of tilt error can reach 5 um. Measurement results show that reposition error of the polishing system is mainly from the tilt error caused by the motor A, repositioning precision is greatly increased after polishing system improvement. The measurement method has important applications in the actual error measurement with low cost, simple operation.

Ultraviolet (UV) photodetectors with high responsivity and speed are highly desirable for imaging and remote sensing applications. Limited by the crystalline quality of a GaN-based material, which is ideal for UV photodetection, the further improvement of the performance is minimal. A hybrid graphene/unintentionally doped (UID) GaN UV photodetector with both high responsivity and high speed is reported. Holes in graphene, which are induced by the photogenerated electrons trapped at the graphene/UID GaN interface according to the capacitive effect, have a long lifetime owing to the electron-hole pair separation in space. Graphene acts as a carrier transport channel and greatly increases the charge collection efficiency under an external bias voltage. The responsivity of a hybrid graphene/UID GaN photodetector with a photosensitive area of 2 mm2 reaches 5.83 A/W at −10 V with a specific detectivity of ∼1011 Jones. The response time is ∼5 ms, which is faster than that of traditional GaN photodetectors. These results will provide a feasible route to UV detection with high performance.Ultraviolet (UV) photodetectors with high responsivity and speed are highly desirable for imaging and remote sensing applications. Limited by the crystalline quality of a GaN-based material, which is ideal for UV photodetection, the further improvement of the performance is minimal. A hybrid graphene/unintentionally doped (UID) GaN UV photodetector with both high responsivity and high speed is reported. Holes in graphene, which are induced by the photogenerated electrons trapped at the graphene/UID GaN interface according to the capacitive effect, have a long lifetime owing to the electron-hole pair separation in space. Graphene acts as a carrier transport channel and greatly increases the charge collection efficiency under an external bias voltage. The responsivity of a hybrid graphene/UID GaN photodetector with a photosensitive area of 2 mm2 reaches 5.83 A/W at −10 V with a specific detectivity of ∼1011 Jones. The response time is ∼5 ms, which is faster than that of traditional GaN photodetectors. These...

Due to high transmittance and high mobility, graphene is one of the promising candidates for a current spreading layer, which is crucial to light emitting diode (LED) performance. In this paper, improved AlGaInP LED performance was reported after graphene was applied on the GaP surface. Due to its lowered work function difference than with the GaN material, the electrical properties remain the same without additional voltage bias. The light output power is enhanced by about 40% under the current injection of 5 mA at room temperature, which was confirmed by the light emission profile analysis in this study. Such results indicate that raphene is a promising candidate as a current spreading layer under low current injection.

A theoretical study of nonlinear effects in the external cavity semiconductor laser (ECSL) with sampled fiber grating is presented; such effects are responsible for asymmetric side-mode suppression ratio or power characteristics, and hysteresis phenomena. Impacts of material and geometrical parameters on nonlinear effects of such lasers were analyzed and discussed. Apodization and interleaved technologies were demonstrated to be helpful with expanding tuning range and suppressing nonlinear effects. Based on this, a new ECSL with interleaved sampled grating has been proposed.

Electrochemical behavior of remarkably low levels of Ribonucleic acid yeast (yRNA) is studied through differential pulse voltammetry (DPV), and kinetic parameters of the electrochemical reaction have also been calculated through square-wave voltammetry (SWV), based on immobilization of yRNA on the surface of a CPB-cellulose modified electrode. YRNA/ CPB-cellulose/ITO conductive glass electrode is demonstrated by Infrared reflect (IR) and electrochemical impedance spectroscopy (EIS). The oxidation peak potential of yRNA shifts negatively with increasing pH. The peak currents decrease gradually in successive scans and no corresponding reduction peaks occur, indicating that oxidation process of yRNA is completely irreversible. Variables influencing DPV response of yRNA, such as pH, pulse amplitude and electrolyte concentration, are explored and optimized. Peak currents are proportional to the concentration of yRNA in the range of 0.1 μg mL−1–1.0 μg mL−1, and the linear regression coefficient equals 0.9923. The detection limit for yRNA is 1.0×10−10 g mL−1. Interferences of L-cysteine, L-alanine, Hemoglobin, Uridine 5′-monophosphate, Guanosine 5′-monophosphate, Adenosine 5′-triphosphate and some metal ions (Co3+, Cr3+, Ni2+, Hg2+, Zn2+, etc) are negligible. The methods adopted here are more sensitive and selective than currently applied techniques and overcome the drawback of absorption spectroscopy arising from a strong interference due to other UV-absorbing substances.

Combination of equivalent reflection cavity model and transmission line theory is applied in theoretical analysis of external cavity semiconductor lasers with sampled fiber Bragg grating. The effects of device parameters on the resonant cavity mode and the side mode suppression ratio have been discussed. For a perfect anti-coated facet and the high coupling efficiency, it is found that the Vernier effect between combed reflectivity peaks and F–P cavity modes can be destroyed and the laser will work on multi-wavelength. The high coupling efficiency plays the same role as the lower anti-reflection coating reflectivity in the side mode suppression ratio and the mode resonance. Finally, the side mode suppression ratio is investigated in detail depending on the anti-coating reflectivity, the coupling efficiency and the high-reflection coating reflectivity.

A polarization-dependent saturable absorber is developed by the use of graphene-polymer film covered microfiber. The evanescent field of the guided mode propagating along the microfiber can effectively interact with graphene. Polarization analysis shows that the single-layer graphene-based saturable absorber is more sensitive to polarization and has larger modulation depth than that of multi-layer graphene. Such a saturable absorber exhibits large saturable absorption power of >56.03 mW, and is easy to fabricate and compatible with optical fiber system. It has high potential in wide range of photonics applications.

We propose a convenient, inexpensive technique to monitor the fast early stage of catastrophic optical damage (COD) in 808-nm high-power laser diodes (LDs). Using an optical system based on the 1550-nm laser diode illuminant and photodiode, we measured the facet reflectivity, which gives information about the surface morphology of the output facet with a temporal resolution of 2 ns, allowing us to trace the rapid early COD process in a transient, real-time mode. The formation of the detected 4-μm-long COD damaged area, which caused a local uneven surface at the output facet and a rapid drop in facet reflectivity at 1550 nm from 28% to 2%, was completed within 20–30 ns, 10 ns shorter than that in the longer-wavelength devices.

Vertical-cavity surface-emitting lasers (VCSELs) have been widely used in short-reach optical communication links and interconnects because of their high modulation speed and low energy consumption. In this paper, the effect of heat dissipation on the modulation bandwidth of high-speed 850-nm VCSELs has been investigated. With increasing bottom distributed Bragg reflector (DBR) diameter from 34 μm to 46 μm, optical output power increased as well as the −3 dB modulation bandwidth. The maximum small-signal modulation bandwidth of 16.2 GHz was achieved with an aperture of 5 μm. Thermal analysis showed that the heat dissipation of the bottom DBR diameter, which determined the differential gain of the quantum wells, has a strong effect on the modulation bandwidth.

A graphene-coated polarizer based on the surface silicon-core microfiber has been proposed and numerically analyzed. The numerical discussion shows that our proposed polarizer serves alternatively as TM-pass or TE-pass polarizers depending on the change of the radius of the silicon core. Their polarization extinction ratios can be adjusted by the structure parameters of the ellipticity, the major and minor diameter of the microfiber, and the thickness of the graphene film. When the length of the graphene film is 1.5 mm, extinction ratios of ~30 and ~32 dB can be respectively achieved at the wavelength of 1.55 μm for TM-pass and TE-pass polarizers. The operation wavelength range of the TM- and TE-pass polarizer could cover ~400 and ~1000 nm, respectively. Our proposed polarizer provides a flexible way to manipulate the polarization of the light in the fiber and highly integrated optical fiber system.

A simple, compact, and robust refractive index sensor is developed, by twisting a pair of silica microfibers to form a coupling device. The transmission spectrum of the device is highly sensitive to the surrounding refractive index and the highest sensitivity obtained is -2377 nm/refractive index unit (RIU), at the refractive index value of - 1.3680, for the fibers with diameter of ~4.2 μm, and the sensitivity can be further increased to - 2735 nm/RIU for a smaller fiber diameter of ~2.8 μm. Such a device is easy to construct, of low cost, and compatible with the optical fiber system.

Graphene pasted on the surface of a nanostructure, e.g., microfiber, enables such graphene-based devices to have excellent photonic and electronic properties. In this paper, an all-optical modulator based on a polymer-supported bilayer graphene film half-wrapped on the surface of the microfiber has been theoretically presented and discussed to make the best use of its ultrawide bandwidth. According to the theoretical analyses on the graphene-microfiber modulator, 100 Gbit/s 8 channel synchronous modulation has been realized with ∼14.88 and ∼14.80 dB modulation depth, respectively, for two polarized modes. The channel wavelength of such modulator covers C, L, and U bands. To ensure the extinction ratio of 16 channel synchronous modulation to be larger than 5 dB, the bilayer graphene-microfiber interaction length of the modular should be greater than 93.06 μm and the diameter of the microfiber should be around 1.8 μm. Under this condition, it also has a tolerance on signal deterioration, as it could effectively decrease the noise of “0” signal.

A digital concatenated grating is presented to tackle that problem of creating a flat ldquotop-hatrdquo comb reflector for tunable lasers. A novel, monolithic, widely tunable semiconductor laser with these gratings is proposed and demonstrated theoretically.

A novel graphene saturable absorber is used in fiber laser for optical pulse generation. Such saturable absorber is created by tightly attaching the graphene film onto the surface of microfiber based on its evanescent field.

Diabetes is a global public health challenge that imposes heavy burdens on communities and individuals. Metformin, the first-line medication for diabetes, has the superiority of reducing risk of macrovascular diseases, all-cause mortality and even possibly cancers. Recent observational studies, however, have demonstrated that long-term metformin therapy increases the probability of vitamin B12 and folate deficiency, and might contribute to the progression of diabetic peripheral neuropathy. Despite metformin is widely used and extensively studied, randomized controlled trials performed to explore the effects of metformin on vitamin B12 and folate are limited. Besides, whether short-term treatment causes vitamin deficiency is a pending issue. We postulate that even a few-month treatment with metformin results in the decrease of vitamin B12 and folate. However, supplementation of vitamin B12 rather than the combination of vitamin B12 and folate might be profitable based on the mechanism of metformin on vitamins in patients with type 2 diabetes. This viewpoint differs from those of majority that a combined supplementation of vitamin B12 and folate is inclined to be advised.

We describe a novel pyruvate selective sensor in which corn tissue, as the biocatalytic layer, is coupled to a fluorescent indicator-based fiber-optic CO2 optrode. This sensor showed shorter response times and a lower detection limit without loss of enzymatic stability as compared to a corn tissue-based pyruvate selective membrane electrode previously studied.

The theoretical basis and experimental evidence for a Stern-Volmer type relationship using the fluorescence ratio (I bl /I) in the absence (I bl ) and presence (I) of CO 2 as response function for fluorescence-based fiber-optic CO 2 sensors is explored. By choosing the right indicator, appropriate bicarbonate concentration, and a thin enough sensing layer, a fiber-optic CO 2 sensor with a usable linear range can be easily achieved using I bl /I as the response function. This allows the possibility of one-point calibration, which cannot be accomplished if the measured fluorescence intensity (I) is used directly as the response function.

In this paper, a simple, compact and robust refractive index sensor has been developed, which is constructed by twisting a pair of silica microfiber to form a coupling device. The transmission spectrum of the device is highly sensitive to the surrounding refractive index and the highest sensitivity of -1665nm/RIU (refractive index unit) can be obtained at the refractive index value of 1.3605 for the fibers with diameter of 2.1μm. The developed sensor device is easy to construct, of low cost and compatible with optical fiber system.

The theoretical model considering nonlinear effects in the external cavity semiconductor laser with sampled fiber grating has been presented. Such effects are including the asymmetric side mode suppression ratio (SMSR) or power characteristics, and hysteresis phenomena. This theoretical model is based on the transmission line theory on compound cavity. The parameters of the laser, e.g. active section length and phase section length, have been optimized to suppress such nonlinear effects, which makes the device control simple and reliable, while the performances such as 16nm tuning range, 40dB SMSR, 8.5mW output power can be maintained.

A novel, monolithic, widely tunable digital concatenated grating DBR laser for optical communications and sensors is proposed. Continuous tuning over 60 nm with high SMSRs and low threshold gains has been demonstrated here with simulated results.