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We report an actively Q-switched fiber laser with cylindrical vector beam emission using a few-mode fiber Bragg grating as mode selection and acousto-optic modulator to achieve the ideal ns pulse. Both radially and azimuthally polarized beams have been obtained by tuning the polarization controllers. The generated Q-switched CVB operates at central wavelength of 1055.6 nm with a spectrum bandwidth...
We demonstrate a dispersion managed Erbium doped all-fiber laser with 101.75MHz repetition rate using 45°TFG to realize mode locking based on nonlinear polarization rotation technique. In our experiment, stable dual-pulse tightly bound states were observed under the pump power of505mW.
In this paper we propose and demonstrate a novel all-fiber fused-type mode selective coupler (MSC) that capable of converting LP01 mode to LP11 mode with high efficiency and purity. Unlike other coupler fabrication techniques for which single mode fiber (or few mode fiber) must be pre-tapered, the advantage of our proposed coupler is that pre-tapering is not required. Two different fibers of the MSC...
This paper proposes a novel fiber ring laser utilizing taper-coupled double-microsphere-cavities (TC-DMC) to stabilize its single-longitudinal-mode operating with a 0.01 nm narrow bandwidth. Fundamental properties including whispery gallery mode (WGM) mode distribution and transmission spectra in the DMC are investigated both theoretically and experimentally. Due to Vernier effect, the WGM spectrum...
A multiwavelength Er-doped fibre ring laser system using all fibre Lyot filter and highly nonlinear fibre was experimentally demonstrated, with degree of polarization up to 99.9% and 50 channels output.
A high-quality nanolayer graphene (NLG) coated hollow core fiber (HCF) platform has been demonstrated for accurate monitoring of refractive index (RI) changes so far mainly operate in liquids but not in air. The NLG with high index is deposited on the outer surface of the HCF, and an enhanced anti-resonant reflecting guidance is formed, which induces sharp periodic lossy dips in the transmission spectrum...
A phase-sensitive optical time domain reflectometry sensing system based on Ultra-weak FBG Array using double pulses is proposed. The principle of this sensing system is elaborated. A series of simulations are carried out to optimize the parameters to increase the sensing distance of this system. The parameters contain reflectivity of UWFBG, the interval between adjacent UWFBGs and pulse width. The...
We propose and demonstrate an all-fiber passively mode-locked laser with pulsed cylindrical vector beam output based on a mode selective coupler (MSC) in a figure-8 cavity, The MSC made of a two mode fiber and a standard single mode fiber is used as both the intracavity transverse mode converter and mode splitter. Through adjusting the polarization state in the laser cavity, both radially and azimuthally...
45° tilted fiber grating (TFG) possesses a series of merits, such as strong polarization dependant loss (PDL), low insertion loss, superior compatibility, and compactness. One of the most prominent features of such polarizing device is the all-fiber structure. This polarizing element plays an important role in all-fiber integrated systems which have been widely investigated in the last two decades...
Software vulnerability remains a serious challenge to the software engineering domain over the past decade as a result of the recent technological advancement in information systems. The rapid development in software applications and failure on the part of system developers to properly analyze program codes before been released to the market increases the chance for data breaches. It is a known fact...
Software vulnerability detecting is an important way of discovering the existing loopholes in software in order to ensure the information security. With the rapid development of the information technology in our society, a large variety of application software with various potentially vulnerabilities has emerged. Therefore, a timely discovery and repair of these loopholes before they are exploited...
In this paper, a novel self-calibration algorithm is proposed for two-dimensional (2-D) direction-of-arrival (DOA) estimation based on L-shaped array (LSA) with mutual coupling. In this method, we construct a transformation matrix to eliminate the mutual coupling between subarrays, and then the DOA estimation problem of LSA is transformed into that of uniform linear arrays (ULAs). Then we only need...
A distributed vibration sensing technique using double optical pulse based on phase-sensitive optical time-domain reflectometry (Φ-OTDR) and ultra-weak FBG (UWFBG) array is proposed for the first time. The single mode sensing fiber is integrated with UWFBG array which has uniform spatial interval and ultra-weak reflectivity. The relatively high reflectivity of the UWFBG, compared with the Rayleigh...
An all-fiber CVB laser based on a few-mode FBG with switchable radially and azimuthally polarized beam generation has been demonstrated. The CVB fiber laser operates at single wavelength of 1054 nm with a 3 dB line width of less than 0.02 nm, signal-to-background ratio of more than 55 dB. And the output power can reach 75 mW, which is the highest CVB power from all-fiber laser.
We have theoretically analyzed the diffractive characteristics of radiation mode of 45° tilted fiber gratings. The simulated angular dispersion for the 45 ° TFG with 748nm period at 1550nm is around 0.053°/nm, which is quite close to the experimental result.
We demonstrate a continuous tunable mode locked Erbium fiber laser using a tilted fiber grating based birefringent filter and carbon nanotube based saturable absorber. The central wavelength can be tuned from 1558 nm to 1564 nm while maintaining ultrashort pulse emission.
The successful fabrication of MIR Ge-on-Si waveguides written by both the high-resolution electron beam lithography (EBL) approach, as well as the wafer scale, high throughput approach using 365 nm i-line stepper lithography is reported. A low propagation loss of ∼2.7 dB/cm at a wavelength of 3.8 μm is shown for Ge-on-Si waveguides patterned using the i-line stepper. The waveguide etching technique,...
We propose and investigate an ultra-compact dual-parameter sensor for simultaneous detection of concentration and temperature using the 0th-order and the 1st-order modes of a single photonic crystal rectangular holes nanobeam multimode microcavity (PC-RNMC).
A modal interferometer was proposed to realize multi-channel mode conversion in two mode fiber. The near-filed pattern confirmed the LP01 mode was converted into LP11 mode at the destructive wavelengths. The mode conversion was realized at 20-channels in the C+L wavelength band with conversion efficiency up to 99.5% and insertion loss lower than 0.6 dB.
Long period grating with a grating period of 15 μm is fabricated with a femtosecond laser. Such a small period grating enables coupling of fundamental core mode with high order cladding modes that have effective refractive index close to water, and exhibits an enhanced sensitivity in low refractive index region.
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