A novel temperature-insensitive strain sensor based on bandwidth demodulation of the reflected light from the tapered fiber grating is presented, which is simple and low-cost and has considerable potential particularl...A novel temperature-insensitive strain sensor based on bandwidth demodulation of the reflected light from the tapered fiber grating is presented, which is simple and low-cost and has considerable potential particularly application for strain sensing,and with the development of the interrogation system, it can demodulate both the bandwidth and the center wavelength of the reflected light from TFG to measure strain and temperature simultaneously.展开更多
Metal-coated fiber Bragg grating（FBG）temperature sensors were prepared via electroless nickel（EN）plating and tin electroplating methods on the surface of normal bare FBG.The surface morphologies of the metal-coate...Metal-coated fiber Bragg grating（FBG）temperature sensors were prepared via electroless nickel（EN）plating and tin electroplating methods on the surface of normal bare FBG.The surface morphologies of the metal-coated layers were observed under a metallographic microscope.The effects of pretreatment sequence,pH value of EN plating solution and current density of electroplating on the performance of the metal-coated layers were analyzed.Meanwhile, the Bragg wavelength shift induced by temperature was monitored by an optical spectrum analyzer.Sensitivity of the metal-coated FBG（MFBG）sensor was almost two times that of normal bare FBG sensor.The measuring temperature of the MFBG sensor could be up to 280℃,which was much better than that of conventional FBG sensor.展开更多
A high sensitive long period fiber grating（LPFG） sensor for the detection of nitrite is proposed, which is realized by coating multiple poly（sodium 4-styrensulfonate）（PSS） and poly（diallyldimethylammonium） chl...A high sensitive long period fiber grating（LPFG） sensor for the detection of nitrite is proposed, which is realized by coating multiple poly（sodium 4-styrensulfonate）（PSS） and poly（diallyldimethylammonium） chloride （PDDA） layers on the fiber grating surface. The sensitivity of this LPFG sensor is maximum when the number of assembled layers is 70. Under this condition, a nitrite concentration of 3×10^-3 mol/L, which is lower than the National Food Additive Standard, 4.2×10^-3 mol/L, can be distinguished. The sensitivity is further increased by 30% when nitrite was determined in the sucrose solution with a concentration of 65%, which provides a new solution for the best refraction index approaching matched index of the fiber cladding. Compared with chemical methods, this nitrite detection technology offers some advantages, such as high accuracy, non toxicity, high speed, low cost, without chemical reagent, and is suitable for foodstuff security detection.展开更多
Suspension of micrometer-sized 1,4-bis（4-methylstyryl）benzene（p-MSB） was converted into colloidal nanocrystal solution by irradiation with an femtosecond laser（800 nm, 1 kHz）. The prepared nanocrystals were rect...Suspension of micrometer-sized 1,4-bis（4-methylstyryl）benzene（p-MSB） was converted into colloidal nanocrystal solution by irradiation with an femtosecond laser（800 nm, 1 kHz）. The prepared nanocrystals were rectangular with ca. 100 nm in size. The same crystal structure as that of bulk crystals was confirmed by X-ray diffraction measurement. UV-Vis spectra and emission spectra of the nanoparticle dispersions in dichloromethane（poor solvent） were examined. The nanocrystal exhibits large quantum yield（89%）. The nonlinear optical properties of the nanocrystals were further studied by Z-scan technique with femtosecond laser duration of 120 fs at a wavelength of 800 nm. The results show that the nanocrystals exhibit strong nonlinear absorption.展开更多
The authors investigated size-dependent amplified spontaneous emission（ASE） from organic crystals. Specifically, N-（4-{4-[4-（diphenylamino）styryl]styryl}phenyl）-N-phenylbenzene amine（Ph-TPA2） organic crystals ...The authors investigated size-dependent amplified spontaneous emission（ASE） from organic crystals. Specifically, N-（4-{4-[4-（diphenylamino）styryl]styryl}phenyl）-N-phenylbenzene amine（Ph-TPA2） organic crystals were used in the experiment. The ASE threshold was decreased with the decrease of the width of the crystal at the same gain length, which reflects that total internal reflection plays an important role on the ASE properties in these slab organic crystals. The ASE properties pumped by one- and two-photon were also comparatively studied. We found that the thresholds of ASE in two-photon pumping condition are less size-dependent than those in singlephoton condition because of the nonlinear light generation processes in two-photon absorption processes.展开更多
The method to pump the FBG w ritten into an Er 3+-doped optical fiber is proposed to increase the group velocity of a probing pulse based on the facts that pump-induced process chan ges the refractive index and disp...The method to pump the FBG w ritten into an Er 3+-doped optical fiber is proposed to increase the group velocity of a probing pulse based on the facts that pump-induced process chan ges the refractive index and dispersion associated with the 4 I_ 15/2- 4I_ 13/2 transition in Er 3+ -doped optical fiber. The system equations are derived. The effects of pump power an d doping concentration on the group velocity are discussed.展开更多
A robust high temperature sensor probe based on a Ni-coated fiber Bragg grating（FBG） was fabricated by Ni electroplating of femtosecond laser written FBG. The probe can resist high temperature up to 800℃ with a hig...A robust high temperature sensor probe based on a Ni-coated fiber Bragg grating（FBG） was fabricated by Ni electroplating of femtosecond laser written FBG. The probe can resist high temperature up to 800℃ with a high sensitivity of 32.2 pm/℃. It also has a good mechanical strength even after high temperature annealing. The thermal strain of the probe was simulated by the finite element method（FEM）. The Bragg resonant wavelength shift with temperature and its sensitivity change with the thickness of the Ni-coated layer were also calculated.展开更多
基金This work is supported by the Innovation Foundation of ChinaAerospace Science and Technology (No. 021390-068)
文摘A novel temperature-insensitive strain sensor based on bandwidth demodulation of the reflected light from the tapered fiber grating is presented, which is simple and low-cost and has considerable potential particularly application for strain sensing,and with the development of the interrogation system, it can demodulate both the bandwidth and the center wavelength of the reflected light from TFG to measure strain and temperature simultaneously.
基金the National Natural Science Foundation of China(No.60777038).
文摘Metal-coated fiber Bragg grating（FBG）temperature sensors were prepared via electroless nickel（EN）plating and tin electroplating methods on the surface of normal bare FBG.The surface morphologies of the metal-coated layers were observed under a metallographic microscope.The effects of pretreatment sequence,pH value of EN plating solution and current density of electroplating on the performance of the metal-coated layers were analyzed.Meanwhile, the Bragg wavelength shift induced by temperature was monitored by an optical spectrum analyzer.Sensitivity of the metal-coated FBG（MFBG）sensor was almost two times that of normal bare FBG sensor.The measuring temperature of the MFBG sensor could be up to 280℃,which was much better than that of conventional FBG sensor.
基金Supported by the National Natural Science Foundation of China(Nos.60707016 and 60807030)
文摘A high sensitive long period fiber grating（LPFG） sensor for the detection of nitrite is proposed, which is realized by coating multiple poly（sodium 4-styrensulfonate）（PSS） and poly（diallyldimethylammonium） chloride （PDDA） layers on the fiber grating surface. The sensitivity of this LPFG sensor is maximum when the number of assembled layers is 70. Under this condition, a nitrite concentration of 3×10^-3 mol/L, which is lower than the National Food Additive Standard, 4.2×10^-3 mol/L, can be distinguished. The sensitivity is further increased by 30% when nitrite was determined in the sucrose solution with a concentration of 65%, which provides a new solution for the best refraction index approaching matched index of the fiber cladding. Compared with chemical methods, this nitrite detection technology offers some advantages, such as high accuracy, non toxicity, high speed, low cost, without chemical reagent, and is suitable for foodstuff security detection.
基金Supported by the National High-Tech Research and Development Program of China(No.2009AA03Z401)the National Natural Science Foundation of China(Nos.61077002,60807030)
文摘Suspension of micrometer-sized 1,4-bis（4-methylstyryl）benzene（p-MSB） was converted into colloidal nanocrystal solution by irradiation with an femtosecond laser（800 nm, 1 kHz）. The prepared nanocrystals were rectangular with ca. 100 nm in size. The same crystal structure as that of bulk crystals was confirmed by X-ray diffraction measurement. UV-Vis spectra and emission spectra of the nanoparticle dispersions in dichloromethane（poor solvent） were examined. The nanocrystal exhibits large quantum yield（89%）. The nonlinear optical properties of the nanocrystals were further studied by Z-scan technique with femtosecond laser duration of 120 fs at a wavelength of 800 nm. The results show that the nanocrystals exhibit strong nonlinear absorption.
基金Supported by the National High-Tech Research and Development Program of China(No.2009AA03Z401)the National Natural Science Foundation of China(Nos.61077002, 60807030)the Project of National Lab for Tsinghua Information Tech-nologies, China
文摘The authors investigated size-dependent amplified spontaneous emission（ASE） from organic crystals. Specifically, N-（4-{4-[4-（diphenylamino）styryl]styryl}phenyl）-N-phenylbenzene amine（Ph-TPA2） organic crystals were used in the experiment. The ASE threshold was decreased with the decrease of the width of the crystal at the same gain length, which reflects that total internal reflection plays an important role on the ASE properties in these slab organic crystals. The ASE properties pumped by one- and two-photon were also comparatively studied. We found that the thresholds of ASE in two-photon pumping condition are less size-dependent than those in singlephoton condition because of the nonlinear light generation processes in two-photon absorption processes.
基金National High Technology Research and Development Programof China(863 -307 -08 -07)
文摘The method to pump the FBG w ritten into an Er 3+-doped optical fiber is proposed to increase the group velocity of a probing pulse based on the facts that pump-induced process chan ges the refractive index and dispersion associated with the 4 I_ 15/2- 4I_ 13/2 transition in Er 3+ -doped optical fiber. The system equations are derived. The effects of pump power an d doping concentration on the group velocity are discussed.
基金the National Natural Science Foundation of China
文摘A robust high temperature sensor probe based on a Ni-coated fiber Bragg grating（FBG） was fabricated by Ni electroplating of femtosecond laser written FBG. The probe can resist high temperature up to 800℃ with a high sensitivity of 32.2 pm/℃. It also has a good mechanical strength even after high temperature annealing. The thermal strain of the probe was simulated by the finite element method（FEM）. The Bragg resonant wavelength shift with temperature and its sensitivity change with the thickness of the Ni-coated layer were also calculated.
