We proposed and experimentally demonstrated a cascaded tilted fiber Bragg grating(TFBG) for enhanced refractive index sensing. The TFBG is UV-inscribed in series in ordinary single-mode fiber(SMF) and reduced-diameter...We proposed and experimentally demonstrated a cascaded tilted fiber Bragg grating(TFBG) for enhanced refractive index sensing. The TFBG is UV-inscribed in series in ordinary single-mode fiber(SMF) and reduced-diameter SMF with the same tilt angle, and then excites two sets of superposed spectral combs of cladding modes. The cascaded TFBG with total length of 18 mm has a much wider wavelength range over 100 nm and narrower wavelength separation than that of a TFBG only in the SMF, enabling an enlarged range and a higher accuracy of refractive index measurement. The fabricated TFBG with the merits of enhanced sensing capability and temperature self-calibration presents great potentials in the biochemical sensing applications.展开更多
We have UV-inscribed fiber Bragg gratings(FBGs), long-period gratings(LPGs), and tilted fiber gratings(TFGs) into mid-IR 2μm range using three common optical fiber grating fabrication techniques(two-beam holographic,...We have UV-inscribed fiber Bragg gratings(FBGs), long-period gratings(LPGs), and tilted fiber gratings(TFGs) into mid-IR 2μm range using three common optical fiber grating fabrication techniques(two-beam holographic, phase mask, and point-by-point). The fabricated FBGs have been evaluated for thermal and strain response. It has been revealed that the FBG devices with responses in mid-IR range are much more sensitive to temperature than that in near-IR range. To explore the unique cladding mode coupling function, we have investigated the thermal and refractive index sensitivities of LPGs and identified that the coupled cladding modes in mid-IR range are also much more sensitive to temperature and surrounding medium refractive index change. The 45° tilted fiber gratings(45°-TFGs) as polarizing devices in mid-IR have been investigated for their polarization extinction characteristics. As efficient reflection filters and in-cavity polarizers, the mid-IR FBGs and 45°-TFGs have been employed in fiber laser cavity to realize multi-wavelength 2 μm Tm-doped CW and mode locked fiber lasers, respectively.展开更多
We report an efficient power tapping device working in near infra-red (800 nm) wavelength region based on UV-in- scribed 45° tilted fiber grating (45°-TFG) structure. Five 45°-TFGs were UV-inscribed in ...We report an efficient power tapping device working in near infra-red (800 nm) wavelength region based on UV-in- scribed 45° tilted fiber grating (45°-TFG) structure. Five 45°-TFGs were UV-inscribed in hydrogenated PS750 fiber using a custom-designed phase mask with different grating lengths of 3 mm, 5 mm, 9 mm, 12 mm and 15 mm, showing polarization dependent losses (PDLs) of 1 dB, 3 dB, 7 dB, 10 dB and 13 dB, respectively. The power side-tapping efficiency is clearly depending on the grating strength. It has been identified that the power tapping efficiency increases with the grating strength and deceases along the grating length. The side-tapped power profile has also been examined in azimuthal direction, showing a near-Gaussian distribution. These experimental results clearly demonstrated that 45°- TFGs may be used as in-fiber power tapping devices for applications requiring in-line signal monitoring.展开更多
We propose and demonstrate a sensitive vector twist sensor based on a small period long period fiber grating(SP-LPFG)fabricated with a femtosecond(fs)laser.The fabricated SP-LPFG is compact in size(2.8 mm)and shows st...We propose and demonstrate a sensitive vector twist sensor based on a small period long period fiber grating(SP-LPFG)fabricated with a femtosecond(fs)laser.The fabricated SP-LPFG is compact in size(2.8 mm)and shows strong polarization dependent peaks in its transmission spectrum due to the vectorial behavior of high-order cladding modes.Twist sensing is realized by monitoring the polarization dependent peaks,since the polarization of input light changes with fiber twist.The proposed sensor can be interrogated by the peak intensity and wavelength,with high twist sensitivity that reaches 0.257 dB/deg and 0.115 nm/deg,respectively.展开更多
Different types of microstructures including microchannels and microslots were made in optical fibers using femtosecond laser inscription and chemical etching.Integrated with UV-inscribed fiber Bragg gratings,these mi...Different types of microstructures including microchannels and microslots were made in optical fibers using femtosecond laser inscription and chemical etching.Integrated with UV-inscribed fiber Bragg gratings,these microstructures have miniature,robustness and high sensitivity features and have been used to implement novel devices for various sensing applications.The fiber microchannels were used to detect the refractive index change of liquid presenting sensitivities up to 7.4 nm/refractive index unit(RIU)and 166.7 dB/RIU based on wavelength and power detection,respectively.A microslot-in-fiber based liquid core waveguide as a refractometer has been proposed and the device was used to measure refractive index,and a sensitivity up to 945 nm/RIU(10−6/pm)was obtained.By filling epoxy in the microslot and subsequent UV light curing,a hybrid waveguide grating structure with polymer core and glass cladding was fabricated.The obtained device was highly thermal responsive,demonstrating a linear coefficient of 211 pm/◦C.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61775182 and 61505165)Marie Sktodowska-Curie Individual Fellowships in the European Union’s Horizon 2020 Research and Innovation Programme(Grant No.660648)
文摘We proposed and experimentally demonstrated a cascaded tilted fiber Bragg grating(TFBG) for enhanced refractive index sensing. The TFBG is UV-inscribed in series in ordinary single-mode fiber(SMF) and reduced-diameter SMF with the same tilt angle, and then excites two sets of superposed spectral combs of cladding modes. The cascaded TFBG with total length of 18 mm has a much wider wavelength range over 100 nm and narrower wavelength separation than that of a TFBG only in the SMF, enabling an enlarged range and a higher accuracy of refractive index measurement. The fabricated TFBG with the merits of enhanced sensing capability and temperature self-calibration presents great potentials in the biochemical sensing applications.
文摘We have UV-inscribed fiber Bragg gratings(FBGs), long-period gratings(LPGs), and tilted fiber gratings(TFGs) into mid-IR 2μm range using three common optical fiber grating fabrication techniques(two-beam holographic, phase mask, and point-by-point). The fabricated FBGs have been evaluated for thermal and strain response. It has been revealed that the FBG devices with responses in mid-IR range are much more sensitive to temperature than that in near-IR range. To explore the unique cladding mode coupling function, we have investigated the thermal and refractive index sensitivities of LPGs and identified that the coupled cladding modes in mid-IR range are also much more sensitive to temperature and surrounding medium refractive index change. The 45° tilted fiber gratings(45°-TFGs) as polarizing devices in mid-IR have been investigated for their polarization extinction characteristics. As efficient reflection filters and in-cavity polarizers, the mid-IR FBGs and 45°-TFGs have been employed in fiber laser cavity to realize multi-wavelength 2 μm Tm-doped CW and mode locked fiber lasers, respectively.
文摘We report an efficient power tapping device working in near infra-red (800 nm) wavelength region based on UV-in- scribed 45° tilted fiber grating (45°-TFG) structure. Five 45°-TFGs were UV-inscribed in hydrogenated PS750 fiber using a custom-designed phase mask with different grating lengths of 3 mm, 5 mm, 9 mm, 12 mm and 15 mm, showing polarization dependent losses (PDLs) of 1 dB, 3 dB, 7 dB, 10 dB and 13 dB, respectively. The power side-tapping efficiency is clearly depending on the grating strength. It has been identified that the power tapping efficiency increases with the grating strength and deceases along the grating length. The side-tapped power profile has also been examined in azimuthal direction, showing a near-Gaussian distribution. These experimental results clearly demonstrated that 45°- TFGs may be used as in-fiber power tapping devices for applications requiring in-line signal monitoring.
基金supported by the National Natural Science Foundation of China (Nos. 11574070, 11874126, and 51803037)the Leading Talents of Guangdong Province Program (No. 2016LJ06D506)the Natural Science FoundationofGuangdongProvince,China(No. 2019A1515011229)
文摘We propose and demonstrate a sensitive vector twist sensor based on a small period long period fiber grating(SP-LPFG)fabricated with a femtosecond(fs)laser.The fabricated SP-LPFG is compact in size(2.8 mm)and shows strong polarization dependent peaks in its transmission spectrum due to the vectorial behavior of high-order cladding modes.Twist sensing is realized by monitoring the polarization dependent peaks,since the polarization of input light changes with fiber twist.The proposed sensor can be interrogated by the peak intensity and wavelength,with high twist sensitivity that reaches 0.257 dB/deg and 0.115 nm/deg,respectively.
文摘Different types of microstructures including microchannels and microslots were made in optical fibers using femtosecond laser inscription and chemical etching.Integrated with UV-inscribed fiber Bragg gratings,these microstructures have miniature,robustness and high sensitivity features and have been used to implement novel devices for various sensing applications.The fiber microchannels were used to detect the refractive index change of liquid presenting sensitivities up to 7.4 nm/refractive index unit(RIU)and 166.7 dB/RIU based on wavelength and power detection,respectively.A microslot-in-fiber based liquid core waveguide as a refractometer has been proposed and the device was used to measure refractive index,and a sensitivity up to 945 nm/RIU(10−6/pm)was obtained.By filling epoxy in the microslot and subsequent UV light curing,a hybrid waveguide grating structure with polymer core and glass cladding was fabricated.The obtained device was highly thermal responsive,demonstrating a linear coefficient of 211 pm/◦C.