The glass samples of SiO2-Al2O3-CdO-Li2O-K2O-Na2O with different Nd3+-doped concentration are prepared by high-temperature
solid-state reaction method, and test the absorption spectrums as well as emission spectrum excited at 488
nm, 532 nm and 808 nm. The third-order optical nonlinear properties of glasses samples are investigated by the z-scan
technique. With the increment of doping concentration of Nd3+, the third-order nonlinear refractive index and the
absorption index increase, so it belongs to the self-focusing and reverse saturated absorption medium. The glass samples
open a outlook of application for nonlinear optical medium and excellent luminescence materials.
Using an improved borosilicate glass with small third-order optical nonlinearities, i.e., nonlinear refractive index (NLRI)
and nonlinear absorption coefficient (NLAC), as the matrix and comparative glass, two types of Ho3+-doped glass are
prepared with a solid-phase smelting process at a relatively low temperature, and their third-order optical nonlinearities
are measured by the closed-aperture Z-scan technique using nanosecond laser pulses at 532nm wavelength. It is found
that the matrix glass possesses a positive third-order NLRI and a positive third-order NLAC, and both the third-order
NLRI and NLAC of Ho3+-doped glasses are one order larger than those of the matrix glass, respectively. Also, an open-aperture
Z-scan experiment and an optical limiting experiment further demonstrate that the Ho3+-doped glasses have a
high third-order NLAC. All the experimental results show that this Ho3+-doped glasses have good protection
performance for the 532nm-laser.
The cadmium silicate glass samples of 40SiO2-14Al2O3-(40-x) CdO-2Li2O-2K2O-2Na2O-xEr2O3 (x=0.15, 0.20, 0.25,
0.30, 0.35, 0.40 mol) was prepared by high-temperature solid-state reaction method, and it is pumped at 488 nm, 532 nm
and 800 nm respectively. The results indicate that the main peak wavelengths are at 547 nm, 731 nm and 1534 nm
excited at 488 nm. The relationship of the intensity between the emission light of 731 nm and Er3+-doped concentration
is nonlinear. Near-infrared light nearby 1534 nm is excited at 532 nm and 800 nm, but it is weaker at 800 nm. The glass
samples open a outlook of application for conversion luminescence materials.
We report a new fiber-optical solution concentration sensor based on an etched long-period fiber grating with one opening head coated with a silver film, which is written symmetrically by three beams of focused high-frequency CO2 laser pulses in a standard single-mode fiber (Corning SMF-28). This sensor is tested with two kinds of solution, i.e. sugar and CaCl2, and the experimental results show that this etched fiber-optical sensor with one opening head is flexible to operate and has very high resolution. The resolution of this sensor increases with approximate linearity, as the concentration of solution increases, and the resolutions for sugar solution at low and high concentrations are 1.65 (g/l) and 1.36 (g/l), respectively. Its average resolution has been improved above 28% after the cladding radius of this sensor is reduced to 61μm by etching with HF acid. The method of etching with HF acid can also be used to tune the resonant wavelengths of a long-period fiber grating.
In this paper, we propose and demonstrate a novel torsion sensor based on a long-period fiber grating (LPFG) induced symmetrically by three beams of focused high-frequency CO2 laser pulses (20~24 kHz). Experimental results show, when the LPFG is twisted clockwise, the resonant wavelength shifts toward shorter wavelengths, and the peak loss decreases. When the LPFG is twisted anticlockwise, the resonant wavelength shifts toward longer wavelengths, and the peak loss increases. The resonant wavelength and the peak loss are all similarly proportional to the twist angle applied. Based on this LPFG, a new kind of fiber-optic torsion sensors can be made, which can not only directly measure the torsion angle, but also determine the torsion direction simultaneously by means of measuring the shift of the resonant wavelength and/or the peak loss of the LPFG.