The traditional measurement for Verdet constant of magneto-optic glass is to measure the Faraday rotation angle indirectly by using optical power meter, which is based on the Faraday rotation effect. There is a relatively large measurement error, because the method neglects the influence of the extinction ratio of polarizer and the axis angle. In our research, a method based on Jones matrix and simulation is studied and used to improve the measurement accuracy. The extinction ratio of polarizer and the axis angle are discussed during the measurement. The experiment system is built for measuring the Verdet constants of ZF7 glass and Ce3+/Tb3+ co-doped glass, by using the He-Ne laser light source, and different polarizers. The results show that the changes of the polarizer’s extinction ratio mainly affected the Verdet constant measurement. The lower extinction ratio, the larger measurement error. The extinction ratio more than 1:1000 for the polarizer is necessary for an accurate measurement, which has important value in terms of reference and guidance for the accurate measurement of Verdet constant of magneto optic glass.
In this paper, we have fabricated the tellurite glass (70TeO2-20ZnO-5Al2O3-5La2O3, mol%, TZAL) by using high temperature melting method. Considering the material dispersion, the dispersion properties of TZAL glass photonic crystal fiber (PCFs) for various structures are analyzed and precisely described based on the vector finite element method (FEM). A novel structure with three-ring TZAL Glass PCF is proposed by introducing large elliptical holes in the inner ring. The simulation results show that ZDW decreases from 1.586μm to1.485μm when the numbers of elliptical holes increases from two to six. ZDW of horizontally disposed ellipses of PCF is a litter lower than that of vertically positioned ellipses. Furthermore, with optimizing parameters of pitch period and diameter of air hole, ZDW is reduced to 1.396μm. The dispersion characteristics can be flexibly designed and adjusted. The approach and results can be guidance for design, manufacture the photonic crystal fibers.
Aiming to the rectangle beam shape in most high power laser, the influences of the several kinds of geometrical aberrations
in slit spatial filtering system have been simulated based on the diffraction theory of aberration. The aberration tolerances
of all kinds of geometrical aberrations in the lenses and incident beam are obtained.
Angular filtering with volume Bragg gratings in photothermorefractive glass was described. The coupled-wave theory was used to discuss the angular filtering based on Transmission Volume Bragg Gratings (TBGs). The results showed that the cutoff frequency was improved, the refractive index modulation had a greater impact on the output beam and the deviation from Bragg condition for incident beam should be less than 0.1mrad. The influence on output beam quality with TBGs parameters was analyzed. Experimental results showed that the near-field distribution of output beam through the angular filtering is better than that of the incident laser beam, and the low-frequency loss of near-field angular filtering is less than 1.8%.
Two-dimensional coupled wave theory is used to calculate spatial dispersion of the diffraction pulse through volume
Bragg grating (VBG). Results indicate that the spatial dispersion, which describes the spatial chirp and reflects globally
how far different frequency components separate, is influenced by the grating parameters, wavelength and the
propagation distance. To two ultrashort pulses with different durations (100fs, 20fs), the degree of spatial broadening
through the VBG and the propagation process is both presented. The approach provides a theoretical foundation to
design proper volume Bragg gratings for redressing the spatial chirp in the ultrashort-pulse laser system.
A novel structure of single-polarization single-mode photonic crystal fiber (SPSM-PCF) is proposed by introducing two large semicircular holes on both sides of the core region. The characteristics of SPSM fibers are numerically analyzed using the finite-element method. The SPSM operating range can be adjusted with the parameters of the elliptical ratio γ and the spacing Λ 1 between the semicircular hole and the adjacent circular hole. The SPSM bandwidth of about 0.7 μm and operating range from 1.0 to 1.7 μm for the PCF have been obtained with the silica–air holes structure. An all-solid PCF structure is proposed, and the SPSM bandwidth of about 0.30 μm is predicted. With the increase in refractive index difference between the substrate and filling materials the SPSM operating range is blue-shifted, and with the decrease in the refractive index difference the bandwidth of the SPSM is reduced.