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The theory of voltage-tunable liquid crystal filter is elaborated,and the change of transmission of BL-009 nematic liquid crystal in visible light band is detailedly analyzed by testing the transmission of liquid crystal using Shimadzu UV-23101 spectrophotometer.Relation curve of transmission with voltage is gained in the wavelength range from 400 nm to 800 nm.The spectral lines at 488 nm wavelength and at 514.5 nm wavelength of argon ion laser are separated.

Based on the developed optically pumped graphene multilayer terahertz surface plasma structures, this paper calculates the real part of propagation index and amplification coefficient in optically pumped graphene multilayer structures, discusses the inluences of momentum relaxation time, temperature, numbers of grapheme layers, and the quasi-Fermi energy in the topmost grapheme layer on the real part of propagation index and amplification coefficient. It is shown that when the real part of dynamic conductivity becomes negative in the terahertz range of frequencies in the optically pumped graphene multilayer structures, the surface plasma of graphene layers can achieve gain. By comparing the peeling-graphene-structure with the graphene structure that has a high conducting bottom graphene layer in optically pumped scheme, it can be said that the surface plasma of the peeling-graphene-structure can get a high efficient amplification. Meanwhile, the structure having properly numbers of graphene layers can get a larger amplification than the simple graphene structure in an optically pumped scheme at low temperatures.

The distribution of pump light and signal light power of Nd3+-doped fiber amplifier along the fiber is numerically simulated. The Nd3 +-doped polarization-maintaining fiber amplifier is experimentally studied, which is pumped by 808nm semiconductor laser. The enlargement factor of small-signal is 300（the gain is 25dB）, and the steady 5W amplificatory pulse is obtained by using the self-made Nd:YAG passive mode-locking laser as seed source. The 86142B-type spectrograph and TDS5104 oscillograph are employed to detect the output laser, and the output power is measured by power meter.

The Nd3+-doped pulse polarization-maintaining fiber laser pumped by 808nm semiconductor laser is investigated experimentally and theoretically. The wave form of output pulse was detected by a TDS5104 oscillograph，and the spectrogram of the output pulse was obtained by using a spectrum analysis apparatus. Originally，the single pulse energy of 2.3mJ with average power of 2.55W was generated at the repetition rate of 1kHz. By changing the resonance cavity and making other modificantions of the laser, we obtained the highest single pulse energy of 3.3mJ with peak power of 17.9kW at the repetition rate of 1kHz，and the pulse width was 184ns and the average power of the output pulse was 3.5W.

By means of numerical analysis，the distribution of pump light and the output laser power along the fiber with different fiber length has been investigated. The experimental research of the Nd3+-doped polarization-maintaining fiber laser is reported，which is pumped by 808nm semiconductor laser. The influence of different fiber winding radius on output power and polarization characteristic of the laser are studied. Double wavelength peaks at 1060nm and 1092nm are obtained. The maximum output power of the laser is 7.35W at 1060nm，the slope efficiency is 58.3%.

The matrix method is employed to analyze the optical activity of liquid crystal, and the matrix presentation of optical rotation is given. The magneto-optical rotation angle of BL-009 nematic liquid crystal is measured using JG-3 type continuous tunable magnetism device and infrared 1350 nm laser. The effect of magnetic field on optical rotation capability of liquid crystal is analyzed in detailed. The threshold of liquid crystal is discussed through experimental testing, and we reached at the conclusion that the rotation direction in liquid crystal is independent of the direction of magnetic field. The obtained result is useful for the design and manufacturing of liquid crystal device.