We report a temperature measurement method based on fixed wavelength transmission intensity of long-period fiber grating. Relative to wavelength or edge filtering, this method has obvious advantages in measurement accuracy and cost. The relationship between the transmission intensity and temperature at a fixed wavelength is simulated based on the theory of long-period fiber grating coupling mode. The results show that the transmission intensity of the fixed wavelength is linearly related to the temperature with the appropriate parameters. In the experiment, the transmission spectrum shows two resonant peaks at 1485 and 1538 nm. Two fixed wavelengths at 1480.4 and 1549.7 nm were selected, and the results show a linear relationship between transmission intensity and temperature. The temperature sensitivity of the transmission intensity at 1480.4 nm is about 0.0544 dB / ° C, which means the value of I1480.4 nm / I0 changes by 1.3% for every 1°C. To eliminate the influence of light source and enhance the measurement sensitivity, the ratio of the transmission intensity of two fixed wavelengths was selected to carry out the temperature measurement. The temperature sensitivity of the ratio of I1480.4 nm / I1549.7 nm was 0.0729 dB / ° C, that is, the light intensity ratio changed by 1.7% when the temperature changed by 1°C. A more reasonable design of long-period fiber grating and a more appropriate selection of fixed wavelength should be able to obtain higher temperature sensitivity.
Helically twisted long-period fiber gratings (H-LPFG) of the single-mode fiber provided by Yofc inc is spiral processed by commercial welding machine. There is an obvious second-order resonant dip near 1526 nm coupling between the fundamental mode and the LP15 cladding mode when the pitch length is about 757 μm. The half peak width is about 15 nm, and the resonant dip is about -28 dB. The transmission intensity ratio of 10lg(I1523.4nm/I1537nm) and 10lg(I1523.4nm/I1551.1nm) versus temperature are measured, which show linearly with temperature. The radio sensitivity of I1523.4nm/I1537nm is about 0.023/C° compared with the wavelength sensitivity of about 45 pm/C°. This can be applied in temperature sensor.
A 9.8 W, continuous wave (CW) operation of a a-cut Tm,Ho:YAlO3 (Tm,Ho:YAP) laser at 2119.2 nm is reported in this paper. The Tm,Ho:YAP crystal, which was cooled at the temperature of 77 K, was double end-pumped by two 14.0- W fiber-coupled laser diodes at 793.5 nm. An optical-optical conversion efficiency of 35% was acquired, corresponding to a slope efficiency of 37.8%.
Infrared-to-visible upconversion emission intensities are investigated in Li+/Er3+, Li+/Ho3+/Yb3+ and Li+/Tm3+/Yb3+
codoped oxide nanocrystals. By introducing Li+ ion, the upconversion emission intensity of rare-earth ions are
significantly enhanced comparing with that without the Li+ ion. The local structure around Er3+ and Ho3+ ions are studied
by the extended X-ray absorption fine structure spectroscopy. After doping Li+ ion, both the average bond lengths of
Er-O and Ho-O are decreased.
Proc. SPIE. 9142, Selected Papers from Conferences of the Photoelectronic Technology Committee of the Chinese Society of Astronautics: Optical Imaging, Remote Sensing, and Laser-Matter Interaction 2013
Polarization measurement approaches only using polarizer and grating is present. The combination polarizers consists of two polarizers: one is γ degree with the X axis; the other is along the Y axis. Binary grating is covered by the combination polarizers, and based on Fraunhofer diffraction, the diffraction intensity formula is deduced. The polarization state of incident light can be gotten by fitting the diffraction pattern with the deduced formula. Compared with the traditional polarization measurement method, this measurement only uses polarizer and grating, therefore, it can be applied to measure a wide wavelength range without replacing device in theory.
Er3+ and Li+ codoped Y2O3 nanocrystals has been prepared by sol-gel method. Upconversion spectrum
and properties of Er3+ has been studied under excitation at 976 nm. Fluorescence intensity ratio of
2H11/2 and 4S3/2 subband levels in the Er3+ and Li+ codoped Y2O 3 nanocrystals have been studied as a
function of temperature. In the temperature range of 295-723 K, the I525nm/I561nm has the highest
thermal sensitivity the maximum sensitivity is approximately 0.016 K-1. The Y2O3: Er3+/Li+nanocrystals with high fluorescence efficiency and the higher temperature revolution, indicated that it is
promising for applications in optical high temperature sensor.