It is important to obtain strong nonlinearities under the conditions of weak-light through electromagnetically induced transparency (EIT), which opens up a new field about optical nonlinearities, named as weak-light nonlinearity. Kerr nonlinearities and four-wave mixing based on electromagnetically induced transparency are introduced. Kerr nonlinearities may be used on the all-optical switches and all-optical logical arithmetic and optical quantum logical gate and so on. Four-wave mixing effects also have many applications. The most important application is that it can expand the frequency of coherent light to infrared and ultraviolet spectrum. In the case of degeneration, four-wave mixing effects are useful for wavefront reconstruction in the adaptive optics. Besides, in material research, the resonant four-wave mixing technique is a vigorous spectrum analyzing tool.

The new method for isotope analysis based on degenerate four wave mixing (DFWM) is proposed for superfine structure researches and the quantum optics theoretical calculation is also introduced to get the percentage of isotopes. The self-oscillation frequency can be determined from the experimental phenomenon. Then, based on three order nonlinear polarizability, with quantum optics calculation of three ladder level system, the relationship of three order nonlinear polarizability and atomic density can be measured.

The reaction mechanism and dynamics of the laser induced excited triplet of 1,4-naphthoquinone (NQ) quenched by TEMPO and biological antioxidant vitamin C (VC) were investigated by means of time resolution electron spin resonance (TR-ESR) method. During the photolysis of NQ/EG (ethylene glycol) solution, NQ abstracts hydrogen atom from solvent molecule EG and the neutral radical NQH and EG ketyl radical CHH(OH) were generated. When TEMPO was added into NQ/EG solution, TEMPO is an effective quencher of NQ and the quenching rate constant is Lmols. For NQ/VC/EG-HO solution, NQ abstracts hydrogen atom not only from solvent EG but also from VC. VC is also an effective quencher of NQ and the quenching rate constant is Lmols. The quenching reactions of NQ by TEMPO and VC are both controlled by diffusion.

Invariant eigen-operator method was applied to derive energy-level gap of charged harmonic oscillator in a uniform electric field. The integral transform method was employed to derive ground state energy and wave function. The quantization spectra of charged harmonic oscillator in a uniform electric field are obtained by simple analysis.

Conventional semiconductor laser threshold extraction method can be affected by noise, poor reproducibility. Under the principle of singularity detection of wavelet transform, it is proposed that wavelet transform is adopted for threshold current extraction, which uses third-order spline function as a double expansion smooth , taking its second derivative for the wavelet function , and multi-scale integration. Experimental results show that compared with several traditional methods, such as the two-segment line fitting method, first derivative method and second derivative method, the method based on wavelet extraction is not susceptible to noise and can truly and accurately obtain the threshold current of semiconductor lasers.

A widely tunable mid-infrared difference frequency generation (DFG) laser source is reported which uses ytterbium doped fiber lasers (YDFL) and an erbium doped fiber laser (EDFL) as the fundamental lights respectively. By using an electronically controlled optical switch to choose one of different tuning bands respectively supplied by four tunable YDFLs and to quickly switch among them, the whole tuning range of the pump light is broadened to be between 1040nm and 1110nm. Two electronically controlled polarization controllers (ECPC) respectively operating in 1060nm and 1550nm waveband are also used to precisely adjust polarizations of the pump and signal lights, so as to improve the conversion efficiency of the DFG system. The PID algorithm and feedback technique are used to control the temperature and driving current of the pump LDs, the controlled conditions are displayed with an LCD. The measurement results show that the mid-infrared laser system may be continuously tuned within the range of 3.04~3.72 μm.

The coherent combination of one-dimensional fiber laser array is studied experimentally by self-imaging confocal resonator. The phase locking output of Yb doped double-cladding fiber laser array was obtained, and the intensity distribution of the far field pattern based on one-dimensional fiber laser array by self-imaging confocal resonator was also realized. Based on the theoretical calculations of the self-imaging confocal resonator, a proper width metal wire is chosen as the spatial filter and steady interference fringes are experimentally obtained when the filter is placed at the plane of output mirror. The experiment results verify the loss functions of the spatial filter for different mode patterns with different filter place and confirm the spatial filter’s mechanism of mode selection.

Using Cr:YAG and acousto-optic mode-locker jointly, the fiber coupling LD pumping Nd: YAG laser was actively-passively mode-locked. The output average power of passively mode-locked by Cr:YAG only, actively mode-locked by acousto-optic mode-locker only and mode-locked by Cr:YAG and acousto-optic jointly are compared and analyzed. The result shows good resolution to the low output energy and stability, and the mode-lock amplitude and energy fluctuation is less than , with the depth of mode locking of 100%, pulse width less than 410ps and output average power near 290mW.

The slab photonic crystal liquid crystal micro-cavity is formed by introducing liquid crystal defect whose thickness equalizs to the light wavelength into the center air hollow of planar photonic crystal. The temperature properties of liquid crystal micro-cavity are investigated using the finite difference time domain (FDTD), and calculated by Matlab. The results show that the resonant wavelength moves into long wavelength, defect mode width decreases, quality factor increases as temperature increases, the change curve of resonant wavelength and quality factor with filling factor and slab thickness move into large. The temperature properties change rapidly near the liquid crystal clear point. Temperature properties of slab photonic crystal liquid crystal micro-cavity provide a theoretical basis for design of tunable photonic crystal device.

The interaction Hamiltonian of a two-level atom and a single-mode radiation field with time-varying frequency is analysed. The special attention is paid on the relationship between the atom-field coupling and frequency of cavity field or volume of cavity. By using vibration mechanism of cavity mirror, the impact induced by vibration of cavity mirror on the optical mode inside the cavity and volume of cavity is studied, and the exact relationship between the time-varying frequency of cavity field and atom-field coupling constant is found.

The interference pattern between two freely expanding Bose-condensed gas with quantum vortex was studied and compared with the situation without vortex. The results show the interference fringes in vortex state tilt and merge at the location of vortex core. So the direction of vortex can be judged by the tilt direction of interference fringe, and the vortex quantum of circulation can be established by the number of merged fringes at the location of vortex core. This special interference pattern offers effective method in proving the existence of vortex experimentally.

Taking the spin-orbit coupling (SOC) into account, the lateral displacements (Goos-Hnchen shift, or GH shift) of ballistic electrons in a two-dimensional electron gas system modulated by ferromagnetic stripe and external voltage is investigated. Spin separation is realized by the GH shift, which provide theoretical foundation for designing spin separation devices. The conclusions are as follows. These anomalous lateral displacements can be tuned effectively by adjusting the incidence angles, magnetic strength of ferromagnetic stripe and Rashba SOC coefficient. It is shown that the lateral displacements can be negative as well as positive. The displacements are related to the spin polarization, which can be used to separate the different spin-polarization electrons. Based on these phenomena, a kind of spatial spin beam splitting of ballistic electrons by the displacements is proposed. The results are beneficial in designing some spintronics devices.

A light synchronization scheme to solve the key problem of signal synchronization in quantum key distribution (QKD) system is proposed. At side of the transmitter, the field-programmable gate array (FPGA) chip produces a synchronization pulse sequence of certain pattern. The pulse sequence drives laser to transmit sync light through one fiber along with signal light to the receiver. The sync light reverts to sync pulse sequence through fast discrimination at side of the receiver, and the pulses are provided to the single-photon detector as gate after high-precision delay adjustment. Simultaneously, the receiver uses a high-frequency clock to sample the sync pulse sequence in FPGA for encoding, synchronizing the transmitter and receiver. The scheme has a high-precision, low-cost, high fault tolerance feature, and was successfully applied to metro quantum communication network.

Taking Dzyaloshinskii-Moriya (DM) effect interaction into account, the entanglement of two-qubit Ising model in an inhomogeneous magnetic field is investigated by means of Negativity theory. It is shown that the existence of DM interaction can obviously enhance the entanglement and put it into a maximum while the magnetic field reduces the entanglement. In addition, low temperature also plays a positive role in entanglement. Moreover, the influence of inhomogeneous magnetic field is also investigated. These effects indicate that one can control the thermal entanglement by manipulation of DM interaction, the homogeneous and inhomogeneous magnetic field and temperature.

In quantum cryptography, it is commonly established that quantum key distribution and quantum secure direct communication work in a single direction, namely one direction communication schemes. However, quantum dialog protocol can enable two legal users exchange messages simultaneously, namely two direction communication. Most existed proposals of quantum dialog protocol are based on discrete variables, which are much more difficult to implement with today’s technology, thus they are less practical than its counterpart. Based on squeezed states, a new quantum dialog scheme is proposed, information-theoretical analysis is then followed and it shows that our scheme is not only secure, but also has larger channel capacity than that of its counterpart.

Proxy blind signature was applied to the electronic paying system, electronic voting system, mobile agent system, security of internet, et al. A quantum proxy weak blind signature scheme is presented based on the correlation of Einstein-Padolsky-Rosen (EPR) pairs and controlled teleportation. Comparing the traditional proxy blind signature schemes based on computing complexity, the scheme uses the physical characteristics of quantum mechanics to implement message blinding, signature and verification, so it could guarantee not only the unconditionally security of the scheme but also anonymity of the message owner.

A scheme for teleporting an unknown single-qubit photonic state in a nearly deterministic and controlled manner is proposed via the weak cross-Kerr nonlinearities. The functions of the complicated CNOT operations and Bell-state analysis can be realized easily with the help of quantum nondemolition measurement technique. This improvement makes the present scheme more efficient than the schemes using nonunitary projective measurements. Discussions about this scheme show that it is feasible with the current experimental technology in optics.

Based on nonlinear Schrdinger equation in optical fiber, the factor of distortion of pulse (DIS) is defined to evaluate the distortion of the pulse. The relation among the DIS, critical length of propagation, critical power and initial chirp of the pulse are numerically simulated and analyzed when only dispersion and self-phase modulation are considered. The results show that the distortion of positive chirped pulse is less than that of negative chirped pulse for given peak power. For given initial chirp, the critical length of pulse decreases with increasing of peak power of input pulse, and critical length of different initial chirp pulses coincides along with increasing of peak power of input pulse. When the length of propagation is fixed, critical power is linear with initial chirp, meanwhile the fluctuation of chirp have more effect on the positive chirped pulse.

Plane strain finite element method was employed to simulate the generation of acoustic surface wave by the line focused pulsed laser irradiation on the aluminates plate. The temporal displacemental signals on the plate surface were calculated and compared with the waveforms obtained in the numerical model with a surface micro cracks introduced in the near field of laser source. The numerical results demonstrate that the monopolar displacement signals of surface skimming longitudinal wave (sP) and Rayleigh wave (R) become the obvious bipolar signals, as there exists a surface micro defect in the immediate vicinity of laser line source. In addition, the peak-to-peak value of bipolar Rayleigh wave signal is enhanced about two times compared with the initial monopolar one. This dramatic transition can be the basis for the scanning laser line source inspection technique for shallow cracks.

A compact Bragg grating filter with a widely tuning range was demonstrated. The filter may be continuously tuned in spectral range of 25nm by applying the axial compression on the fiber Bragg grating (FBG) which is guided with two special ferrules. Experimental results show that, the Bragg wavelength of the FBG changes linearly with the axial compression displacement. Variations of the reflectivity and 3dB bandwidth of the FBG are respectively less than 0.59dB and 0.1nm during the tuning process. The tunable filter is stable and the Bragg wavelength shift in 30min is less than 0.07nm.

By using Runge-Kutta algorithm, the differential equations that describe the evolution of super-Gaussian pulse in optical fibers were calculated. The numerical result indicates that width of pulse and chirp of frequency are oscillating with the increasing of distance if normalized coefficient of the second-order dispersion is appropriate and initial chirp is small enough, and increasing jitter of frequency and phase resulted in the increase of distance. The normalized coefficient of the second-order dispersion and initial chirp () were obtained that can guarantee the conformal transmission of the pulse under circumstance of given set of values of the factor () of sharpness of super-Gaussian pulse. The important parameters of super-Gaussian pulse deviated widely from initial values in the process of transmission in optical fibers if coefficient of the second-order dispersion is too big or too small, or initial chirp is too big.

An optical switching model was established based on the transmission characteristics of electromagnetic wave in the photonic-crystal coupling waveguides. The coupling length was calculated when the refractive index of the coupling dielectric rods is in different values by using the coupling mode theory and plane wave expansion method. Using finite-difference time-domain method, the light wave output condition was analyzed as refractive index of dielectric rods equals to 3 and 3.4, and the effect of position of heterostructure to the optical switching functions was also analyzed. The result shows that the function of optical switching changes when the dielectric rods refractive index is 3.4, but the position of heterostructure doesn’t change the optical switch function. These properties can be used in the design of optical switches more flexibility in practice.