A Simple All-Fiber Solc Filter Based on 45-Tilted Fiber Gratings

A simple all-fiber Solc filter (AFSF), which consists of two 45°-tilted fiber gratings (45°-TFGs) UV-inscribed in the polarization-maintaining fiber (PMF) and a series of PMF cavities, is proposed and demonstrated. The performance of the proposed filter has been theoretically simulated and experimentally verified. Both the simulated and experimental results show that the bandwidth of the filter could be tuned by the PMF sub-cavity length and the number of PMF cavities. And the free spectral range (FSR) only depends on the sub-cavity length. As a proof of that, the bandwidths of AFSF with different number of PMF sub-cavity (N=2, N=3, N=4) and the same PMF sub-cavity length of 30cm are 4 nm, 2.6nm, and 2nm, respectively. The FSRs of 3-stage AFSF with different PMF sub-cavity length (L=20 cm and L=40 cm) are 15.3 nm and 7.97 nm, respectively. Furthermore, we have also investigated the tunability of the AFSF by controlling the temperature of PMF cavity with a tuning sensitivity around 1.205 nm°/c. Compared with existing fiber-optic Solc filters, the AFSF with prominent advantages such as extremely simple and robust structure, thermal tunability in wavelength, and low cost will bring a bright future for applications in optical communication and sensing systems

L-band GHz femtosecond passively harmonic mode-locked Er-doped fiber laser based on nonlinear polarization rotation

Via using an L-band optimized in-fiber polarizing grating device, a GHz L-band femtosecond passively harmonic mode-locked (PHML) Er-doped fiber laser based on nonlinear polarization rotation (NPR) is firstly demonstrated. 4.22 GHz pulses with the duration of 810 fs and super-mode suppression ratio (SMSR) of 32 dB are obtained under the pump power of 712 mW corresponding to 215th harmonic order. The central wavelength of 4.22 GHz pulses is 1581.7 nm with 10.1 nm 3-dB bandwidth. Furthermore, under this fixed pump power, higher harmonic orders can also be attained by rotating the polarization controllers (PCs) properly. The highest repetition rate we obtained is 7.41 GHz with the SMSR of 20.7 dB

Theoretical analysis and experimental demonstration of the radiation mode distribution of 45° TFG

In this paper, we have theoretically analyzed and experimentally demonstrated the spatial distribution of the radiation mode of 45° tilted fiber grating (TFG). The simulation results have shown the intensity distribution of the radiation mode along the fiber axis exhibited an exponential reduction. In experiment, we have observed the radiation mode pattern of a 5-mm long 45°TFG. The captured profiles along the radial direction and axial direction were in good agreement with the simulated results of the model

Numerical and Experimental Characterization of Radiation Mode of 45° Tilted Fiber Grating

In this paper, we have numerically and experimentally investigated the radiation mode of 45° tilted fiber grating (45° TFG). By introducing the axial distributions into the volume current method, we have established a three-dimensional theoretical model to analyze spatial distributions of the radiation mode of 45° TFG, and measured the radiation mode spatial distributions in experiment. Both numerical and experimental results show that the radiation mode of 45° TFG exhibits an exponential reduction along the fiber axial direction, and a quasi-Gaussian profile along the radial direction of fiber. Additionally, we have also measured the detailed polarization-dependent azimuthal intensity distributions of radiation modes of both s-and p-polarized core modes. The degree of polarization of radiation mode is around 99.886%, which is independent of the length and the polarization extinction ratio of the grating. Moreover, for the first time, we have experimentally observed a very weak p-polarized component existing in the radiation mode, which has matched well with the simulation results

Widely Wavelength-tunable Mode-locked Fiber Laser Based on a 45° Tilted Fiber Grating and Polarization Maintaining Fiber

We present a passively mode-locked Erbium-doped fiber laser with tunable parameters including central wavelength, 3-dB bandwidth, and pulse duration. The mode-locking mechanism of the laser is realized by using single-walled carbon nanotubes (SWCNTs) polyvinyl alcohol composite film as a saturable absorber. The tunable operation is implemented via a fiber birefringence filter consisting of a polarization maintaining (PM) fiber and a Brewster fiber grating. The laser achieves a maximum spectral tuning range of 36 nm with 8-cm PM fiber. The maximum spectral width variation of 5.19 nm is acquired when the PM fiber is 12 cm. Simultaneously, the spectral widths of pulses at different central wavelengths are also adjustable. Furthermore, the total cavity length is 8.28 m, which is the shortest cavity length to obtain such wide tuning range in an Erbium-doped fiber laser based on SWCNTs

Genetic Regulation of N6-Methyladenosine-RNA in Mammalian Gametogenesis and Embryonic Development

Emerging evidence shows that m(6)A is the most abundant modification in eukaryotic RNA molecules. It has only recently been found that this epigenetic modification plays an important role in many physiological and pathological processes, such as cell fate commitment, immune response, obesity, tumorigenesis, and relevant for the present review, gametogenesis. Notably the RNA metabolism process mediated by m(6)A is controlled and regulated by a series of proteins termed writers, readers and erasers that are highly expressed in germ cells and somatic cells of gonads. Here, we review and discuss the expression and the functional emerging roles of m(6)A in gametogenesis and early embryogenesis of mammals. Besides updated references about such new topics, readers might find in the present work inspiration and clues to elucidate epigenetic molecular mechanisms of reproductive dysfunction and perspectives for future research

Generation of 64-fs L-band stretched pulses from an all-fibre Er-doped laser

We demonstrate an L-band all-fibre erbium-doped laser mode locked by nonlinear polarisation rotation and working in the stretched-pulse regime. The use of a single segment of gain fibre with appropriate length and dispersion and a Brewster fibre grating optimised for the L band as an in-fibre polariser enables the generation of pulses at 1.59-μm central wavelength, which can be linearly compressed to 64-fs duration. Numerical simulations of the laser model support our experimental findings. Our laser design gives a route towards low-cost and low-complexity fibre-integrated laser sources for applications requiring L-band ultrashort pulses

64-fs L-band pulse generation by an all-fibre Er-doped laser

We demonstrate a L-band all-fibre erbium-doped laser mode-locked by nonlinear polarisation rotation. The use of a single gain segment with appropriate length and dispersion and a L-band optimised Brewster fibre grating as an in-fibre polariser enables the generation of 64-fs pulses at 1.59µm