Due to their unique physical properties, nonlinear materials are gradually demonstrating significant potential in the field of optics. Gold nanoparticles supported on carbon black (Au/CB), possessing low loss and high nonlinear characteristics, serve as an excellent material for saturable absorber (SA) in ultrafast fiber lasers. In this study, we investigated the performance of Au/CB material and designed an ultrafast fiber laser based on Au/CB SA, successfully observing stable fundamental mode-locking and pulse bunch phenomena. Specifically, when the fiber laser operates in fundamental mode-locking state, the center wavelength of optical spectrum is 1 558.82 nm, with a 3 dB bandwidth of 2.26 nm. Additionally, to investigate the evolution of real-time spectra, the dispersive Fourier transform (DFT) technology is employed. On the other hand, the pulse bunch emitted by the laser is actually composed of numerous random sub-pulses, exhibiting high-energy characteristics. The number of sub-pulses increases with the increase of pump power. These findings contribute to further exploring the properties of Au/CB material and reveal its potential applications in ultrafast optics.

A D-type photonic crystal fiber (PCF) sensor based on surface plasmon resonance (SPR) principle is designed. In order to excite the SPR effect, a gold film is plated on the open-loop channel of the sensor, the free electrons in a metal are resonated with photons. The structural parameters are fine-tuned and the sensing performance of the sensor is studied. The results show that the maximum spectral sensitivity reaches 18 000 nm/RIU in the refractive index range of 1.24—1.32, and the maximum resolution is 5.56×10-6 RIU. The novel structure with high sensitivity and low refractive index provides a new perspective for fluid density detection.

Quantum cascade lasers (QCLs) have broad application potentials in infrared countermeasure system, free-space optical communication and trace gas detection. Compared with traditional Fabry-Prot (FP) cavity and external cavity, distributed feedback quantum cascade lasers (DFB-QCLs) can obtain narrower laser linewidth and higher integration. In this paper, the structure design, numerical simulation and optimization of the Bragg grating of DFB-QCLs are carried out to obtain the transmission spectrum with central wavelength at 4.6 m. We analyze the relationship among the structure parameters, the central wavelength shift and transmission efficiency using coupled-wave theory and finite-difference time-domain (FDTD) method. It is shown that the increase in the number of grating periods enhances the capabilities of mode selectivity, while the grating length of a single period adjustment directly determines the Bragg wavelength. Additionally, variations in etching depth and duty cycle lead to blue and red shifts in the central wavelength, respectively. Based on the numerical simulation results, the optimized design parameters for the upper buffer layer and the upper cladding grating are proposed, which gives an optional scheme for component fabrication and performance improvement in the future.

We proposed and demonstrated the ultra-compact 1 310/1 550 nm wavelength multiplexer/demultiplexer assisted by subwavelength grating (SWG) using particle swarm optimization (PSO) algorithm in silicon-on-insulator (SOI) platform. Through the self-imaging effect of multimode interference (MMI) coupler, the demultiplexing function for 1 310 nm and 1 550 nm wavelengths is implemented. After that, three parallel SWG-based slots are inserted into the MMI section so that the effective refractive index of the modes can be engineered and thus the beat length can be adjusted. Importantly, these three SWG slots significantly reduce the length of the device, which is much shorter than the length of traditional MMI-based wavelength demultiplexers. Ultimately, by using the PSO algorithm, the equivalent refractive index and width of the SWG in a certain range are optimized to achieve the best performance of the wavelength demultiplexer. It has been verified that the device footprint is only 2×30.68 m2, and 1 dB bandwidths of larger than 120 nm are acquired at 1 310 nm and 1 550 nm wavelengths. Meanwhile, the transmitted spectrum shows that the insertion loss (IL) values are below 0.47 dB at both wavelengths when the extinction ratio (ER) values are above 12.65 dB. This inverse design approach has been proved to be efficient in increasing bandwidth and reducing device length.

Metalenses are two-dimensional planar metamaterial lenses, which have the advantages of high efficiency and easy integration. However, most metalenses cannot modulate the light intensity, which limits their applications. To deal with it, taking advantage of flexible regulation of the beam amplitude and phase by the metalens, the geometric phase method is selected to design the dual-function metalens. It can effectively eliminate chromatic aberration in a visible light band from 535 nm to 600 nm and achieve amplitude modulation. After transmitting the metalens, the amplitudes of the beam respectively turn into 0.2 and 0.9. In this way, the amount of transmission of metalens in the preset band can be quantitatively controlled. According to the distribution characteristics of light diffraction intensity, the metalens designed can play a dual modulation role of achromatism and interference double-beam equilibrium in the paper, to meet the needs of miniaturization and integration of the optical system. The achromatic and amplitude-modulated metalens will have great application potential in optical holographic imaging and super-resolution focusing.

In this paper, we propose a single-port dual-beam leaky-wave antenna (LWA) in the terahertz (THz) band based on a composite spoof surface plasmon polariton (SSPP) waveguide. The antenna can generate three independent transmission channels by exciting two independent modes inherent to hole and groove structures, respectively. By periodic modulation of the hole and groove structures, we achieve dual-beam scanning through a broad radiation angle using only the -1st space harmonics of the two modes, hence avoiding the instability of the -2rd space harmonic. Within the operating frequency range of 0.62—0.85 THz, the gain ranges from 13.5 dBi to 17 dBi for the backward beam, and from 6 dBi to 11.8 dBi for the forward beam. The antenna can accomplish continuous backward beam through broadside to forward beam scanning with a total scanning range of 116° and an average efficiency of about 92%. The antenna exhibits a great potential in the design of multi-transceiver radar system in the THz band and multi-beam LWAs.

The performance of decoding algorithm is one of the important influential factors to determine the communication quality of optical camera communication (OCC) system. In this paper, we first propose a decoding algorithm with adaptive thresholding based on the captured pixel values under an ideal environment, and then we further propose a decoding algorithm with multiple features, which is more suitable under the existence of the interference of light sources. The algorithm firstly determines the light-emitting diode (LED) array profile information by removing the interfering light sources through geometric features, and then identifies the LED state by calculating two grayscale features, the average gray ratio (AGR) and the gradient radial inwardness (GRI) of the LEDs, and finally obtains the LED state matrix. The experimental results show that the bit error ratio (BER) of the decoding algorithm with multiple features decreases from 1×10-2 to 5×10-4 at 80 m.

We have numerically presented an actively mode-locked fiber laser with tunable repetition rate based on phase modulator. By finely optimizing intra-cavity parameters, the ultrashort pulses with tunable repetitive frequency at giga hertz level can be easily generated due to the balance between dispersion and nonlinearity in the fiber laser cavity. When the pulse frequency is changed from 1.0 GHz to 4.2 GHz, the spectral width increases from ~15.65 nm to ~27.25 nm. In addition, the corresponding pulse duration decreases from ~81.59 ps to ~31.57 ps. Moreover, these output pulses with giga hertz repetitive rates and the picosecond widths can be further compressed by using the reasonable dispersion medium. For the pulse regime with repetition frequency at giga hertz level, the obtained smallest pulse duration is about ~62 fs based on chirp pulse compression. We hope that these simulation results can promote further research and application in the ultrashort pulse lasers with high repetition rate.

A high-performance zinc oxide (ZnO)/polyvinylpyrrolidone (PVP) humidity sensor was prepared by simple coprecipitation method with PVP as surfactant. The coprecipitation method has low reaction temperature, little energy consumption and simple preparation, which is suitable for large-scale production. The PVP makes sample’s surface with more hydroxyl and oxygen vacancies than pure ZnO, which can absorb more water molecules and promote the decomposition of water molecules into H3O+ to form effective ion conduction. When the molar ratio of PVP to ZnO is 1: 1, the ZnO/PVP humidity sensor has low hysteresis (~4.2%), short response/recovery time (9/10 s), excellent stability and high sensitivity with more than 4 orders of magnitude in relative humidity (RH) range from 11% to 95%. Moreover, the ZnO/PVP humidity sensor can distinguish different respiratory states of human body, which has a potential in monitoring and prevention of respiratory diseases.

A series of single-unit and tandem blue phosphorescent organic light-emitting diodes (OLEDs) were prepared by ad-justing the concentration of dopant based on the structure of ITO/NPB/EL unit/Alq3/Cs2CO3/Al. The results show that tandem device with doping concentration of 10 wt% has appropriate energy transfer, which achieves the best perfor-mance with a maximum current efficiency of 3.4 cd·A-1. Further study found that current efficiency and power effi-ciency of the tandem OLED adding BCP as hole blocking layer (HBL) can achieve 7.85 cd·A-1 and 0.72 lm·W-1, re-spectively. It is 2.88 times and 1.57 times larger than those of sing-unit devices, and green peak is restrained effective-ly.

A real-time label-free DNA biosensor based on thin-core fiber (TCF) interferometer is demonstrated experimentally. The proposed biosensor is constructed by splicing a TCF between two segments of single mode fibers (SMFs) and in-tegrated into a microfluidic channel. By modifying the TCF surface with monolayer poly-l-lysine (PLL) and sin-gle-stranded deoxyribonucleic acid (ssDNA) probes, the target DNA molecules can be captured in the microfluidic channel. The transmission spectra of the biosensor are measured and theoretically analyzed under different biosensing reaction processes. The results show that the wavelength has a blue-shift with the process of the DNA hybridization. Due to the advantages of low cost, simple operation as well as good detection effect on DNA molecules hybridization, the proposed biosensor has great application prospects in the fields of gene sequencing, medical diagnosis, cancer de-tection and environmental engineering.

A 1 550 nm long-wavelength vertical cavity surface emitting laser (VCSEL) on InP substrate is designed and fabri-cated. The transfer matrix is used to compute reflectivity spectrum of the designed epitaxial layers. The epitaxial layers mainly consist of 40 pairs of n-AlxGayIn(1-x-y)As/InP, and 6 strain compensated AlxGayIn(1-x-y)As/InP quantum wells on n-InP substrate, respectively. The top distributed Bragg reflection (DBR) mirror system has been formed by fabricat-ing 4.5 pairs of SiO2/Si. The designed cavity mode is around 1 536 nm. The dip of the fabricated cavity mode is around 1 530 nm. The threshold current is 30 mA and the maximum output power is around 270 μW under CW opera-tion at room temperature.

A graded-index mode division multiplexer with low loss and low crosstalk is proposed. The transmission channel adopts a pure silica core with large effective area to achieve low attenuation, which effectively reduces the splicing loss with pure silica core few-mode transmission fiber. Low differential mode group delay is realized by using grad-ed-index distribution. Also the effective index difference of the modes is greater than 0.5×10-3 to ensure low crosstalk between modes. The performance of the mode division multiplexer is investigated using the beam propagation method and full-vector finite element method. The result shows that the coupling efficiency of multiplexer is better than .0.479 dB, and the extinction ratio is higher than 31.2 dB in the wavelength of 1 400—1 700 nm. In C band, the aver-age coupling efficiency of all mode channels of multiplexer is better than that of .0.140 dB, which shows flatness. The proposed scheme is an effective way to implement a multiplexer with low crosstalk, low loss, low fusion loss, high coupling efficiency, high extinction ratio and wide operating band.

We numerically demonstrate that whispering-gallery modes (WGMs) in a microsphere resonator with three layers of high, low and high refractive index (RI) are analyzed by using the finite difference time domain (FDTD) method. To make the light couple in and out of the microsphere, a phase matched waveguide is used to overlap the WGMs eva-nescent radiation field. By changing the gap between the microsphere and waveguide, the WGMs of two high-RI lay-ers are efficiently excited. The stored energy and the mode volume are optimized for sensing applications. The cou-pling structure reveals a good sensitivity of 38.29 nm/RIU (RI unit).

The self-heterodyne detection Brillouin optical time domain reflectometer (BOTDR) system using broad-band laser is proposed to reduce coherent Rayleigh noise and improve the system performance. Compared with the system with narrow-band laser, the stimulated Brillouin scattering (SBS) threshold can be improved by about 3 dB. The experi-mental results of the narrow-band laser measurements for three times independently and the broad-band laser meas-urement for one time are compared. The root-mean-square (RMS) errors of Brillouin linewidth for two systems with narrow-band laser and broad-band laser are 6.9 MHz and 2.7 MHz, respectively, and the RMS errors of temperature for the heated fiber are about 1.3 °C and 0.7 °C. With the broad-band laser, signal-to-noise ratio (SNR) of the un-heated fiber is approximately equivalent to that of the integrated three independent Brillouin signals for the narrow-band laser, and the results are believed to be beneficial for performance improvement and measurement time reduc-tion.

A temperature-insensitive polarization filter and a neotype sensor based on a hybrid-circular-hole microstructured op-tical fiber (MOF) are proposed. Numerical investigations demonstrate that the x polarized component of silica core mode can couple to the cladding mode in the researched wavelength, while the y polarized component would not. Fur-thermore, the resonant region can be controlled by changing the diameters or coordinates of the air holes, and the MOF has good performance on stability of temperature. Moreover, the hybrid-circular-hole structure is propitious to selec-tively integrate different functional materials. Two different materials are integrated into this proposed MOF, the ap-plication of the Sagnac interferometer in temperature sensing is studied, and two groups of dips would be observed in the transmission spectra, which have different temperature sensitivities. Therefore, the proposed MOF can be used as a flexible temperature-insensitive polarization filter or potentially applied to a two-parameter sensor.

Based on frequency demodulation method, a novel fiber Bragg grating (FBG) velocimeter which can achieve wind speed and temperature synchronous measurement is proposed in this paper. The wind speed and temperature synchro-nous measurement is realized by cup anemometer (CA) signal modulation and Hilbert-Huang transformation (HHT) signal processing. The working principle of the novel FBG velocimeter is demonstrated and its theory calculation model is also set up by using basic mechanical knowledge and blade element momentum (BEM). Further, calibration experiment is carried out on one prototype of the FBG velocimeter to obtain its measurement performance. HHT is in-troduced to deal with calibration experiment data. After data analyses, the results show that the novel FBG velocimter can achieve high-precision wind speed measurement of 0.012 m/s with minimum detection limit of 0.41 m/s, and its temperature detection precision is 10.6 pm/°C.

An implantable optrode composed of fiber and multi-channel flexible thin-film electrode is developed. The flexible recording electrode is made from polyimide and is wrapped around the optical fiber. The front end of the fiber is ta-pered by wet etching. With the tapered shape, the light can leak from the sidewall of the fiber, and the tapered tip makes it easy to be implanted. The flexible electrode is attached with its recording sites aligning to the tapered part on the fiber. With this method, the fiber acts as an optical waveguide, as well as a support probe for flexible thin-film electrode. This novel device simplifies the fabrication process and decreases the size of the optrode. The device works well in vivo and the optical caused spike can be recorded with signal-to-noise ratio of 6:1.

We report a time-of-flight photon-counting imaging system in conjunction with a single-photon detector mounted with a fiber optic taper, which equivalently enlarges the active area of the single-photon detector by 100 times. The field of view of the imaging system is extended from ±0.57° to ±7° by using the fiber optic taper to collect the scattered pho-tons. Since only a single avalanche photodiode is used, the noise level of the system is maintained at a low level. We demonstrate the scanning of the targets at a stand-off distance of 28 m with a centimeter depth resolution.

In this paper, p-chlorophenylacetic acid and p-fluorophenylacetic acid were applied to modify the indium tin oxide (ITO) electrodes. The surface work functions of unmodified ITO, p-chlorophenylacetic acid modified ITO (Cl-ITO) and p-fluorophenylacetic acid modified ITO (F-ITO) are 5.0 eV, 5.26 eV and 5.14 eV, respectively, and the water contact angles are 7.3°, 59.1° and 46.5°, respectively. The increase of the work function makes the hole injection ability of the devices im-proved, which is proved by the hole transport devices. The self-assembly (SAM) layers transfer hydrophilic ITO to hydro-phobic ITO, which makes ITO more compatible with the hydrophobic organic layers, making the organic film more stable during the operation. After modification, the organic light emitting diodes (OLEDs), SAM-modified ITO/NPB/Alq3/LiF/Al, with better performance and stability were fabricated. Especially, the OLED with Cl-ITO (Cl-OLED) has a maximum lumi-nance of 22 428 cd/m2 (improved by 32.9%) and a half-lifetime of 46 h. Our results suggest that employing organic acids to modify ITO surface can enhance the stability and the luminescent properties of OLED devices.

Polarization navigation system is a hotspot in the field of bionic navigation. Compared with point source polarized light navigation sensor, the polarization information acquisition method based on image sensor and imaging technolo-gy has better robustness, and it can obtain more polarization information. In this paper, an embedded imaging polari-zation sensor for glimmer environment application is designed and developed. The multi-channel video processing technology of TMS320DM642 is used to capture the polarization information of charge coupled device (CCD) camera with three channels. The images are processed by digital signal processer (DSP) in real time, and the angle of polariza-tion (AOP) image is calculated simultaneously with an acquisition and calculation speed of 10 frame per second. Sen-sor can obtain absolute rotation angle, and the AOP image can be displayed on liquid crystal display (LCD). It pro-vides an effective experimental platform for the research of imaging polarization mode navigation device based on embedded system.

The multiband co-aperture optical system with compact structure can achieve full and effective integration of mul-ti-source intelligence information, which is one of the development direction of the optical system. Dichroic beam splitter is a vital optical component to make several systems with different bands share one aperture. The effect of the dichroic beam splitter on the multiband co-aperture optical system is analyzed by matrix optics method and primary aberration theory. The results indicate that the reflection angle of the dichroic beam splitter as a reflector changes im-aging direction, and the wedge angle of the dichroic beam splitter as a transmission component increases some aberra-tions.

A method to generate Airy beam by combining the Fresnel holographic lens and the cubic phase of Airy beam is proposed. The detailed theoretical derivation to express the optical transform principle of the proposed method is presented. And excellent experimental results are demonstrated. It is shown that this approach works well and simplifies the experimental facility effectively, especially reducing the optical system length to half of that of the conventional method. In addition, the proposed method can realize the beam propagation trajectory control of Airy beam and generate Airy beam array.

A kind of efficient non-doped white organic light-emitting diodes (WOLEDs) were realized by using a bright blue-emitting layer of 4,4-bis(2,2-diphenylvinyl)-1,1-biphenyl (DPVBi) combining with red emitting ultrathin layer of ［2-methyl-6-［2-(2,3,6,7-tetrahydro-1H,5H-benzo［ij］quinolizin-9-yl)ethenyl］-4H-pyran-4-ylidene］propane-dinitrile (DCM2) and green emitting ultrathin layer of 10-(2-benzothiazolyl)-2,3,6,7-tetrahydro-1,1,7,7-tetramethyl-1H,5H, 11H(1)-benzopyropyrano(6,7-8-i,j)quinolizin-11-one (C545T) with different thicknesses of 0.05 nm, 0.10 nm and 0.20 nm. For comparing, a doped WOLED was also fabricated, in which C545T and DCM2 are codoped into DPVBi layer to provide blue, green and red emission for obtaining white emission. The maximum luminance and power efficiency of the doped WOLED are 5 765 cd/m2 at 16 V and 5.23 lm/W at 5 V, respectively, and its Commission Internationale de l’Eclairage (CIE) coordinate changes from (0.393 7, 0.445 3) at 5 V to (0.300 7, 0.373 8) at 12 V. When the thickness of the ultrathin C545T layer in non-doped WLEDs increases, the emission luminance increases, but all non-doped devices are in the yellow white region. The device with 0.10-nm-thick C545T has a maximum efficiency of 15.23 cd/A at 8 V and a maximum power efficiency of 6.51 lm/W at 7 V, and its maximum luminance is 10 620 cd/m2 at 16 V. CIE coordinates of non-doped WLEDs with C545T thickness of 0.05 nm, 0.10 nm and 0.20 nm are (0.447 3, 0.455 6), (0.464 0, 0.473 1) and (0.458 4, 0.470 0) at 8 V, respectively.

In this paper,a self-mode-locked Nd:YVO4 picosecond vortex laser is demonstrated, which can operate on the different Laguerre-Gaussian (LG) modes at 1 064 nm. A π/2 mode converter is utilized to realize the picosecond vortex laser with LG mode transformed from the high-order Hermite-Gaussian (HG) mode. For the proposed laser, the mode-locked pulse repetition rate is 1.81 GHz. The average output powers of LG12 mode and LG02 mode are 1.241 W and 1.27 W, respectively, and their slope efficiencies are 23.2% and 24%, respectively.

An all fiber magnetic field sensor with peanut-shape structure based on multimode fiber (MMF) is proposed and experimentally demonstrated. The sensing structure and magnetic fluid (MF) are both encapsulated in capillary, and the effective refractive index of MF is affected by surrounding magnetic field strength. The measurement of magnetic field is realized by observing the wavelength drift of interference peak. The transmission spectrum generated by Mach-Zehnder interferometer (MZI) includes core-core mode interference and core-cladding mode interference. Experimental results demonstrate that the core-cladding mode interference is sensitive to magnetic field, and the magnetic field sensitivity is 0.047 8 nm/mT. In addition, two kinds of interference dips are sensitive to temperature, and the sensitivities are 0.060 0 nm/°C and 0.052 6 nm/°C, respectively. So the simultaneous measurement of magnetic field strength and temperature can be achieved based on sensitivity matrix.

We experimentally evaluate and optimize the time constant of solar irradiance absolute radiometer (SIAR). The systemic error introduced by variable time constant is studied by a finite element method. The results shown that, with a classic time constant of 30 s for SIAR, the systemic errors are 0.06% in the midday and 0.275% in the morning and afternoon. The uncertainty level which can be considered negligible for SIAR is also investigated, and it is suggested that the uncertainty level has to be less than 0.02%. Then, combining the requirement of international comparison with these two conclusions, we conclude that the suitable time constant for SIAR is 20 s.

In this paper, we mainly study the preparation of an optical biosensor based on porous silicon (PSi) Bragg mirror and its feasibility for biological detection. The quantum dot (QD) labeled biotin was pipetted onto streptavidin functionalized PSi Bragg mirror samples, the affinity reaction between QD labeled biotin and streptavidin in PSi occurred, so the QDs were indirectly connected to the PSi. The fluorescence of QD enhanced the signal of biological reactions in PSi. The performance of the sensor is verified by detecting the fluorescence of the QD in PSi. Due to the fluorescence intensity of the QDs can be enhanced by PSi Bragg mirror, the sensitivity of the PSi optical biosensor will be improved.

In this paper, we mainly study the preparation of an optical biosensor based on porous silicon (PSi) Bragg mirror and its feasibility for biological detection. The quantum dot (QD) labeled biotin was pipetted onto streptavidin functionalized PSi Bragg mirror samples, the affinity reaction between QD labeled biotin and streptavidin in PSi occurred, so the QDs were indirectly connected to the PSi. The fluorescence of QD enhanced the signal of biological reactions in PSi. The performance of the sensor is verified by detecting the fluorescence of the QD in PSi. Due to the fluorescence intensity of the QDs can be enhanced by PSi Bragg mirror, the sensitivity of the PSi optical biosensor will be improved.

A novel multi-beam folded waveguide (MBFW) circuit, which can enhance the output power and interaction efficiency of sub-terahertz (THz) traveling wave tube (TWT), is presented in the paper. Operating with fundamental mode and multiple electron beams means that a larger beam current can be used for a higher output power. The characteristics of the MBFW structure are analyzed and optimized. Compared with the single-beam folded waveguide (SBFW) TWT, the output power of the MBFW TWT increases from 3.64 W to 25.45 W at 140 GHz and its electronic efficiency increases from 1.06% to 7.4% under the conditions of an input peak power of 10 mW, a beam voltage of 9.55 kV and a current of 12 mA. The optimized MBFW structure can be successfully fabricated by micro milling, with dimension errors below expectation, and the measured transmission characteristics are in good agreement with the design.

The organic light-emitting devices (OLEDs) using 4,4’,4’’-tris{N-(3-methylphenyl)-N-phenylamin}triphenylamine (m-MTDATA) and MoO3or 1,3,5-triazo-2,4,6-triphosphorine-2,2,4,4,6,6-tetrachloride (TAPC) and MoO3as the hole-injection layer (HIL) were fabricated. MoO3can be expected to be a good injection layer material and thus enhance the emission performance of OLED. The highest occupied molecular (HOMO) of MoO3is between those of m-MTDATA or TAPC and N,N’-bis-(1-naphthyl)-N,N’-diphenyl-1,1’-biphenyl-4,4’-diamine (NPB), which reduces the hole-injection barrier and improves the luminance of the OLEDs. The current efficiency is improved compared with that of the device without the MoO3layer. The highest luminous efficiency of the device with 2-nm-thick MoO3as HIL is achieved as 5.27 cd/A at 10 V, which is nearly 1.2 times larger than that of the device without it. Moreover, the highest current efficiency and power efficiency of the device with the structure indium-tin oxide (ITO)/TAPC (40 nm)/MoO3(2 nm)/TcTa:Ir(ppy)3 (10%, 10 nm)/ tris-(8-hydroxyquinoline) aluminium (Alq) (60 nm)/LiF (1 nm)/Al are achieved as 37.15 cd/A and 41.23 lm/W at 3.2 V and 2.8 V, respectively.

A refractive index insensitive temperature sensor based on waist-enlarged few mode fiber (FMF) bitapers is presented. The first section of FMF is spliced between two single-mode fibers. In fusion process, the waist-enlarged FMF bitapers can be obtained by large current discharging repeatedly. The refractive index and temperature sensing mechanisms are analyzed. For the sensors with different sizes, the refractive index and temperature experiments have been performed. The results show that in the refractive index ranges of 1.335 0—1.346 6 and 1.348 2—1.419 3, the refractive index insensitivity is verified. In a temperature range of 31.9—90 °C, the sensor sensitivity can be up to 85.57 pm/°C. In addition, it has a compact structure. Therefore, the sensor can avoid the cross sensitivity for measuring the refractive index and temperature simultaneously.

We investigate a novel GaAs-based laser power converters (LPCs) grown by metal-organic chemical vapor deposition (MOCVD), which uses a single monolithic structure with six junctions connected by tunnel junctions to obtain a high output voltage. The LPCs with diameters of active aperture of 2 mm and 4 mm were fabricated and tested. The test results show that under an 808 nm laser, two LPCs both show an open circuit voltage of above 6.5 V. A maximum power conversion efficiency of 50.2% is obtained by 2 mm sample with laser power of 0.256 W, and an output electric power of 1.9 W with laser power of 4.85 W is obtained by 4 mm sample. The performances of the LPCs are deteriorated under illumination of high flux, and the 4 mm sample shows a higher laser power tolerance.

A magnetic field sensor with a magnetic fluid (MF)-coated intermodal interferometer is proposed and experimentally demonstrated. The interferometer is formed by sandwiching a segment of single mode fiber (SMF) between a segment of multi-mode fiber (MMF) and a spherical structure. It can be considered as a cascade of the traditional SMF-MMF-SMF structure and MMF-SMF-sphere structure. The transmission spectral characteristics change with the variation of applied magnetic field. The experimental results exhibit that the magnetic field sensitivities for wavelength and transmission loss are 0.047 nm/mT and 0.215 dB/mT for the interference dip around 1 535.36 nm. For the interference dip around 1548.41nm, the sensitivities are 0.077 nm/mT and 0.243 dB/mT. Simultaneous measurement can be realized according to the different spectral responses.

A continuously tunable microwave photonic notch filter with complex coefficient based on phase modulation is proposed and demonstrated. The complex coefficient is generated using a Fourier-domain optical processor (FD-OP) to control the amplitude and phase of the optical carrier and radio-frequency (RF) phase modulation sidebands. By controlling the FD-OP, the frequency response of the filter can be tuned in the full free spectral range (FSR) without changing the shape and the FSR of the frequency response. The results show that the center frequency of the notch filter can be continuously tuned from 17.582 GHz to 29.311 GHz with FSR of 11.729 GHz. The shape of the frequency response keeps unchanged when the phase is tuned.