We propose a high temperature-sensitive long period fiber grating（LPFG） sensor fabricated by using the femtosecond laser transversal-scanning method. The femtosecond pulses scan over the whole fiber core and some pa...We propose a high temperature-sensitive long period fiber grating（LPFG） sensor fabricated by using the femtosecond laser transversal-scanning method. The femtosecond pulses scan over the whole fiber core and some part of the cladding region; the modified regions are more extended. It is found that the LPFG-I fabricated by the transversal-scanning method shows higher temperature sensitivity and better temperature uniformity than that of LPFG-II written by the femtosecond laser point-by-point method. The LPFG-I with a temperature sensitivity of 75.96 pm/°C in the range of 25°C–400°C is measured. Moreover, in the range from 400°C to 800°C, a higher temperature sensitivity of 148.64 pm/°C and good linearity of 0.99 are achieved, while the temperature sensitivity of LPFG-II is only 95.55 pm/°C. LPFG-I exhibits better temperature characteristics, which, to the best of our knowledge, has the highest sensitivity in silica fiber temperature sensors.展开更多
The writing of an internal diffraction grating in optical glass plate is demonstrated using low-density plasma formation excited by a high-intensity femtosecond Ti:sapphire laser. The same diffraction efficiency at &#...The writing of an internal diffraction grating in optical glass plate is demonstrated using low-density plasma formation excited by a high-intensity femtosecond Ti:sapphire laser. The same diffraction efficiency at ±1,±2, and 0 order is achieved by multiple layers writing. The dependences of diffractive efficiency on the irradiated energy, the speed of writing, the numerical aperture (NA) of the focusing objective, and materials are investigated in detail. The grating is birefringent. It is attributed to residual stress interaction between glass and femtosecond laser pulse.展开更多
The fabricated gratings used for an 800-nm compressed laser pulse have more than 90% di?raction e?ciency in the –1st order for TE polarization within 760–860 nm, and the maximum value is 94.3%. The laserinduced dama...The fabricated gratings used for an 800-nm compressed laser pulse have more than 90% di?raction e?ciency in the –1st order for TE polarization within 760–860 nm, and the maximum value is 94.3%. The laserinduced damage threshold(LIDT) of the gratings increases from 0.53 to 0.75 J/cm 2 in the normal beam in a pulse width τ of 40–100 fs. The LIDT of the gratings is observed a τ 0. 25 scaling in the pulse width region. The damage morphologies of the gratings indicate that the initial damage of the gratings locates at the grating lines, a position that coincides with that of the electric field maximum.展开更多
基金supported by the National Natural Science Foundation of China(NSFC)(Nos.91323301,51505505,51475482,and 51475481)the Natural Science Foundation of Hunan Province(No.2016JJ3147)+2 种基金the China Postdoctoral Science Foundation(Nos.2015M572264 and 2016T90757)the Self-selected Topic Fund of State Key Laboratory of High Performance and Complex Manufacturing(No.ZZYJKT2015-08)the Fundamental Research Funds for the Central Universities of Central South University
文摘We propose a high temperature-sensitive long period fiber grating（LPFG） sensor fabricated by using the femtosecond laser transversal-scanning method. The femtosecond pulses scan over the whole fiber core and some part of the cladding region; the modified regions are more extended. It is found that the LPFG-I fabricated by the transversal-scanning method shows higher temperature sensitivity and better temperature uniformity than that of LPFG-II written by the femtosecond laser point-by-point method. The LPFG-I with a temperature sensitivity of 75.96 pm/°C in the range of 25°C–400°C is measured. Moreover, in the range from 400°C to 800°C, a higher temperature sensitivity of 148.64 pm/°C and good linearity of 0.99 are achieved, while the temperature sensitivity of LPFG-II is only 95.55 pm/°C. LPFG-I exhibits better temperature characteristics, which, to the best of our knowledge, has the highest sensitivity in silica fiber temperature sensors.
基金This work was supported by the National Natural Science Foundation of China under Grant No:60078004 and the Director Foundation of State Key Laboratory of Transient Optics and Technology.
文摘The writing of an internal diffraction grating in optical glass plate is demonstrated using low-density plasma formation excited by a high-intensity femtosecond Ti:sapphire laser. The same diffraction efficiency at ±1,±2, and 0 order is achieved by multiple layers writing. The dependences of diffractive efficiency on the irradiated energy, the speed of writing, the numerical aperture (NA) of the focusing objective, and materials are investigated in detail. The grating is birefringent. It is attributed to residual stress interaction between glass and femtosecond laser pulse.
基金supported by the National "863" Program of Chinathe National Natural Science Foundation of China(Nos.10704079 and 11104295)
文摘The fabricated gratings used for an 800-nm compressed laser pulse have more than 90% di?raction e?ciency in the –1st order for TE polarization within 760–860 nm, and the maximum value is 94.3%. The laserinduced damage threshold(LIDT) of the gratings increases from 0.53 to 0.75 J/cm 2 in the normal beam in a pulse width τ of 40–100 fs. The LIDT of the gratings is observed a τ 0. 25 scaling in the pulse width region. The damage morphologies of the gratings indicate that the initial damage of the gratings locates at the grating lines, a position that coincides with that of the electric field maximum.
