Based on the dual peak resonance of long-period fiber grating（LPFG）, a novel film sensor is presented, in which films sensitive to the surrounding gases are coated on the cladding of the fiber grating region, and th...Based on the dual peak resonance of long-period fiber grating（LPFG）, a novel film sensor is presented, in which films sensitive to the surrounding gases are coated on the cladding of the fiber grating region, and the intervals of the dual peak resonant wavelengths change with the film refractive index. According to the coupled-mode theory, a triple-clad numerical model is developed to analyze the relation between the sensitivity Sn and the thin film optical parameters （the film thickness h3 and the refractive index n3） and the fiber grating parameters （the grating period A and the core index modulation σ）. By using optimization method, the optimal film optical parameters and the grating structure parameters are obtained. Numerical simulation shows that the sensitivity of this scheme to refractive index of the films is predicted to be more than 10-7. The theoretic analysis provides straightforward foundation for the actual highly sensitive film sensors.展开更多
To obtain the influence rules of the coating parameters of a long-period fiber grating(LPFG)with respect to temperature,strain and refractive index sensing properties,based on the mode coupling theory,a strict four-la...To obtain the influence rules of the coating parameters of a long-period fiber grating(LPFG)with respect to temperature,strain and refractive index sensing properties,based on the mode coupling theory,a strict four-layer theorietical model of a metal film coated LPFG is established,and these parameters that affect the spectral characteristics of the metal film coated LPFG are studied.The simulation results show that there is an optimal metal film thickness on the surface of the LPFG that will induce the surface-plasmon resonance(SP R)effect,which results in higher sensitivity to the environmental temperature and refractive index but has little influence on the strain There is theoretical evidence that when the silver thickness is between0.8and1.2nm,the refractive index sensitivity will reach the peak point of42.4026,at which the refractive index sensor sensitivity is increased by4.S%.The theoretical results of coating a long-period fiber grating provide a good theoretical basis and guidance for LPFG design and parameters optimization展开更多
A new model is proposed to explain the physical mechanism of the extraordinary transmission enhancement in subwavelength metallic grating.The extraordinary transmission enhancement is described by the co-operation of ...A new model is proposed to explain the physical mechanism of the extraordinary transmission enhancement in subwavelength metallic grating.The extraordinary transmission enhancement is described by the co-operation of Fabry-Perot-like(FPL) resonance and the surface plasmon polariton(SPP) resonance.The rigorous coupled-wave analysis(RCWA) and the finite difference time domain(FDTD) method are employed to illustrate the model by calculating the transmission and the field distributions in the subwavelength metallic grating,respectively.And the numerical calculations show that transmission enhancement is achieved when the coupling resonance of the incident light,the surface plasmon polariton mode and the Fabry-Perot-Like mode is happened,which are in good agreement with the proposed model.展开更多
A novel design of a two-axis fast steering mirror(FSM) with piezoelectric actuators is proposed for incoherent laser beam combination. The mechanical performance of the FSM is tested. The results show that the tilting...A novel design of a two-axis fast steering mirror(FSM) with piezoelectric actuators is proposed for incoherent laser beam combination. The mechanical performance of the FSM is tested. The results show that the tilting range of the mirror is about 4 mrad, and the 1st-order resonance frequency is about 250 Hz. A self-designed grating encoder is taken as the sensor, which ensures the optimal precision of 10 μrad. The novel mechanical design can meet the requirement of engineering in incoherent laser beam combination.展开更多
A long period fiber grating （LPFG） fabricated upon the all-solid photonic bandgap fiber by CO2 laser irradiation was investigated, and its resonance wavelength was at 1335.76nm with a modulation depth of 15dB and a ...A long period fiber grating （LPFG） fabricated upon the all-solid photonic bandgap fiber by CO2 laser irradiation was investigated, and its resonance wavelength was at 1335.76nm with a modulation depth of 15dB and a 3-dB bandwidth of 2.6nm. We studied its strain, temperature, and index sensor characteristics, the strain sensitivity of 0.992 pm/m was obtained by using linear fit, and the relationship between the refractive index and wavelength obeyed the distribution of quadratic function. Also, we demonstrated its temperature response was relatively insensitive （21.51 pm/~C）.展开更多
基金the National Natural Science Foundation of China (No 60777035)Research Project of the Education Committee of Shanghai(No 07ZZ87)Shanghai Leading Aca-demic Discipline Project (No T0501)
文摘Based on the dual peak resonance of long-period fiber grating（LPFG）, a novel film sensor is presented, in which films sensitive to the surrounding gases are coated on the cladding of the fiber grating region, and the intervals of the dual peak resonant wavelengths change with the film refractive index. According to the coupled-mode theory, a triple-clad numerical model is developed to analyze the relation between the sensitivity Sn and the thin film optical parameters （the film thickness h3 and the refractive index n3） and the fiber grating parameters （the grating period A and the core index modulation σ）. By using optimization method, the optimal film optical parameters and the grating structure parameters are obtained. Numerical simulation shows that the sensitivity of this scheme to refractive index of the films is predicted to be more than 10-7. The theoretic analysis provides straightforward foundation for the actual highly sensitive film sensors.
基金National Natural Science Foundation of China(No.51309001)Scientific Research Key Project of Anhui Province(No.KJ2017A041)
文摘To obtain the influence rules of the coating parameters of a long-period fiber grating(LPFG)with respect to temperature,strain and refractive index sensing properties,based on the mode coupling theory,a strict four-layer theorietical model of a metal film coated LPFG is established,and these parameters that affect the spectral characteristics of the metal film coated LPFG are studied.The simulation results show that there is an optimal metal film thickness on the surface of the LPFG that will induce the surface-plasmon resonance(SP R)effect,which results in higher sensitivity to the environmental temperature and refractive index but has little influence on the strain There is theoretical evidence that when the silver thickness is between0.8and1.2nm,the refractive index sensitivity will reach the peak point of42.4026,at which the refractive index sensor sensitivity is increased by4.S%.The theoretical results of coating a long-period fiber grating provide a good theoretical basis and guidance for LPFG design and parameters optimization
基金Supported by the National Natural Science Foundation of China under Grant Nos.60977048 and 61078046the International Collaboration Program of Ningbo under Grant No.2010D10018the International Joint Projects CNR/CAS Agreement and the K.C.Wong Magna Fund in Ningbo University,China
文摘A new model is proposed to explain the physical mechanism of the extraordinary transmission enhancement in subwavelength metallic grating.The extraordinary transmission enhancement is described by the co-operation of Fabry-Perot-like(FPL) resonance and the surface plasmon polariton(SPP) resonance.The rigorous coupled-wave analysis(RCWA) and the finite difference time domain(FDTD) method are employed to illustrate the model by calculating the transmission and the field distributions in the subwavelength metallic grating,respectively.And the numerical calculations show that transmission enhancement is achieved when the coupling resonance of the incident light,the surface plasmon polariton mode and the Fabry-Perot-Like mode is happened,which are in good agreement with the proposed model.
基金supported by the Technology Project of Changchun City(No.2013270)
文摘A novel design of a two-axis fast steering mirror(FSM) with piezoelectric actuators is proposed for incoherent laser beam combination. The mechanical performance of the FSM is tested. The results show that the tilting range of the mirror is about 4 mrad, and the 1st-order resonance frequency is about 250 Hz. A self-designed grating encoder is taken as the sensor, which ensures the optimal precision of 10 μrad. The novel mechanical design can meet the requirement of engineering in incoherent laser beam combination.
文摘A long period fiber grating （LPFG） fabricated upon the all-solid photonic bandgap fiber by CO2 laser irradiation was investigated, and its resonance wavelength was at 1335.76nm with a modulation depth of 15dB and a 3-dB bandwidth of 2.6nm. We studied its strain, temperature, and index sensor characteristics, the strain sensitivity of 0.992 pm/m was obtained by using linear fit, and the relationship between the refractive index and wavelength obeyed the distribution of quadratic function. Also, we demonstrated its temperature response was relatively insensitive （21.51 pm/~C）.
