This PDF file contains the front matter associated with SPIE Proceedings volume 7846, including the Title Page, Copyright information, Table of Contents, Introduction, and the Conference Committee listing.

In this paper, we experimentally study the Rabi splitting in a subwavelength cavity constructed by single-negative (SNG) metamaterials. First, the SNG metamaterials are fabricated by using coplanar waveguide with lumped-element series capacitors and shunt inductors loading. Then, the subwavelength cavity is constructed based on the SNG metamaterials. Finally, Rabi splitting in the subwavelength cavity is experimentally realized.

We report the generation of 1178nm based on cascaded Raman scattering in KTA crystal intracavity pumped by a AO Q-switched Nd:YAG laser. The output power at 1178nm is around 80mW when the diode pump power was 7.6W at 808nm. At the same time, the low-order Stokes waves at 1091nm, 1120nm, 1146nm and visible yellow laser at 573nm (the second harmonic wave of 1146nm) are also detected. The total Stokes output power was 240mW and the yellow laser was 115mW. The power at 1178nm can be increased with output mirrors that are more suitable. The spectra of the generated wavelengths were experimentally analyzed and they accords well with theoretical results.

In the paper, we report experimental results of the effect of UV-light exposure on the profile of thermal poling induced second-order optical nonlinearity (SON) in twin-hole optical fibers. Before UV-exposure, uniform thermal poling at 320°C and 3.5 kV along a 5-7 cm long section of twin-hole fiber produced a uniform SON of 0.263 pm/V in the fiber core. A focused light beam from a frequency-doubled Ar+ laser operating at 244 nm was used to locally erase the induced nonlinearity in the fibers to create a periodic structure for quasi-phase matching applications. The UV-exposed fibers were then observed under a second-harmonic microscope to characterize the distribution profile of any residual nonlinearity after exposure. Effects of scanning speeds of the laser beam on the length of nonlinearity-erased section and amplitude of the residual nonlinearity were investigated. It was found that the required UV-light fluence to fully erase the induced nonlinearity is only ~0.5% of that typically required for fabricating fiber Bragg gratings.

Fast and slow light in optical fibers was a powerful tool for future all-optical networks. We observed fast and slow light based on the stimulated Brillouin scattering using the gain region in optical fibers just adjusting the pump power experimentally. In this paper, the time delay as a function of the pump signal power, Stokes signal power and the fiber length were studied.

We propose a novel of photonic crystal fiber (PCF) with low dispersion high birefringence for four wave mixing. This fiber is composed of a solid silica core and a cladding with squeezed-hexagonal-lattice circular air-holes along the fiber length. Dispersion and birefringence are investigated simultaneously by using the full vectorial finite element method. Numerical results show the proposed fiber possesses the property of low-dispersion and high-birefringence, with the result of the total dispersion being within ±5 ps•nm^-1km^-1 over ultra broad wavelength range from 1360 to 1670 nm and the corresponding high birefringence being about 1.5×10^-2 at 1550 nm. Furthermore, the nonlinear coefficient of the proposed fiber is also numerically analyzed, and present high nonlinear effects. Therefore, high birefringence, low flattened dispersion and high nonlinear effects are combined in the proposed PCF perfectly, which has the great significance for the four-wave mixing.

The molecular chromphores with high first hyperpolarizability values have been reported with the development of conjugated polyene-bridge or thiophene-bridge system and strong tricyano-containing heterocyclic electron acceptors. In this work, we investigated the enhancement of the electro-optic response by introducing various groups, such as OCH3, Ophenel, OTBDMS, etc, as an additional donor part on conventional FTC type donor-π-acceptor molecules. These new type donors exhibited a strong solvatochromic effect, indicating an extra donation to the pi-conjugated bridge, which shifted the charge-transfer absorption of the chromophores to the lower energy region. Furthermore, the simple modification on the donor moiety resulted in a great improvement in the first hyperpolarizability and macroscopic electro-optic coefficient (r₃₃) over the benchmark dialkylamino FTC counterparts. For the real applications, the stronger acceptor was adopted to further increase the r₃₃ and such a chromophore was post-functionalized as side-chain polymer to enhance the temporal stability.

Two longitudinally multimode Febry-Perot diode lasers have been sideband injection-locked to the +1 and -1 sidebands of a 3.4GHz electro-optical modulator (EOM). Optical heterodyne measurement showed that powers of 99.5% of the slave laser could be injection-locked to the +1 or -1 sidebands, and the unselected master laser carrier was suppressed down to -24dB. Generally, the long-term stability and efficiency of the injection-locking to the +1 sideband was worse than the -1 due to the asymmetry of the injection-locking bandwidth. The microwave signal at 6.8GHz had a measured 3dB linewidth of less than 200Hz, without considering the noise contribution by the driving signal of the additional acousto-optical modulator. The proposed method will be used for driving the stimulated Raman transitions in a Rubidium based atom gyroscope.

An examination of the efficiencies of three commonly used nonlinear crystals (PPKTP, LBO, and BiBO) when generating second harmonic of a Cesium laser is presented. The experiment investigates both the intracavity and single pass second harmonic generation of 895 nm Cs laser light when operating in quasi-CW and in CW modes and pumped by several watts. A degradation of the conversion efficiencies for each crystal was observed when high fundamental powers or a high duty cycle of the pump were used. For a Cs laser operating at 894nm, PPKTP is found to be the optimal crystal for intracavity SHG in both pulsed and CW modes when operating at SHG powers of several watts. At higher powers, however, the increased absorption coefficient of PPKTP at 447nm, compared to that of BiBO or LBO, may become significant to where another crystal will be more appropriate for this application. Maximum blue light power obtained with PPKTP crystal was about 1.5W in CW mode and 2.5W in QCW.

Electromagnetically induced phase grating (EIPG) is investigated in a microwave-coupled four-level atomic system, where the two closely spaced lower levels are driven by a microwave field. In the presence of a microwave field, the diffraction efficiency of grating is improved greatly by phase modulation. For this case, one can properly tune the interaction length of the atomic sample, modulate detuning of the microwave and the probe fields, and obtain the high diffraction efficiency of 32% approximately.

The spectra of cesium 6P_3/2 - 8S_1/2 excited-state transition have been obtained using double resonance optical-pumping (DROP) technique in a room-temperature vapor cell, and have shown a much better signal-to-noise ratio (SNR) compared with that using the traditional optical-optical double resonance (OODR) method. Furthermore, the line-width of DROP spectra is obviously narrowed by electromagnetically-induced transparency (EIT) effect in cesium 6S_1/2 F=4 - 6P_3/2 F'=5 - 8S_1/2 F''=4 transitions. Finally, such DROP spectrum of 6P_3/2 F'=5 - 8S_1/2 F''=4 transition with a high SNR and a narrow line-width is applied into frequency stabilization of a 795 nm external-cavity diode laser, and the residual frequency fluctuation is ~ 600 kHz within 500 s.

Ghost imaging has emerged a decade ago as a new imaging technique. Its feature is the image will appear on the optical path, which never passes through the object actually. In this paper, we will give an overview of quantum imaging, include the experiments with two-photon entanglement state source generated by spontaneous parametric down conversion, as well as with pseudo-thermal light. Then we will show our ghost imaging experiment scheme with the pseudo-thermal light source. We obtain the pseudo-thermal source by using a XY Phase Series Spatial Light Modulator (supplied by BNS company) to modulate the laser light. This spatial light modulator changes the phase of the output light field by controlling the loading element on every pixel.

Dispersion management in single mode fiber (SMF) can be accomplished in many ways, though the most widely used approach employs lengths of transport fiber of opposite dispersion characteristics to the principal fiber in the link, usually standard single mode fiber (SSMF). Typically, a 10 to 20km length of dispersion compensating fiber (DCF) is placed before the regenerators inducing negative dispersion to compensate for the positive dispersion accumulated over the 60 to 80km length of the SMF. Analysis and comparison of the pre-compensation scheme and the post-compensation scheme have been done. Due to the interplay between dispersion, nonlinearity, and signal power, the dispersion affects the pulse evolution.

Relativistic quantum key distribution (QKD) protocol is a kind of modified BB84 QKD protocol based on the principles of not only quantum mechanics but also special relativity. Its advantage compared with BB84 protocol is that all of the qubits could be used for key generation, and Alice and Bob are able to select any measuring bases. We prove its unconditional security against coherent attack via the method based on CSS codes: begin with a modified EPR based protocol which can be proved unconditionally secure, then reduce the protocol to a CSS codes based protocol. Finally, the CSS codes based protocol is demonstrated equivalent to the relativistic QKD protocol, and we arrived at the conclusion of the unconditional security of the final key.

The quantum bit error rate (QBER) based on the weak coherent pulse's quantum key distribution is analyzed. It is indicate that the coefficient of QBER is not a constant but is increased exponentially with the transmission distance. Based on the three groups' experimental data, the function fitting for the coefficient of QBER has been done respectively. We discovered that these fitting functions have the same function form. Subsequently we use fitting function to optimize the mean photon number for the BB84 quantum key distribution with decoy states. The result shown that the optimized mean photon number depend on the transmission distance. Using these results and the GYS's experimental parameters we compared the key generation rates proposed by Lo et al with the modified one. We find that the latter is superior to the former within a certain distance.

An overview of quadrature-based quantum key distribution is provided. Beginning from the comparison between single-photon schema and continuous variable schema, the article focuses on the classical and state-of-art protocols. Protocols' main procedures and security analysis are introduced, which includes the methods under individual attack and collective attack. Then recent development of unconditional security proof is introduced including the optimality of Gaussian attack and de Finetti theorem. Introduction towards discrete modulated schemas' security proof is also made. At last, the article discusses experimental realization of various protocols and the main trend in this field.

We propose an efficient scheme to prepare multipartite entanglement of atomic ensembles trapped in separate cavities. Our scheme has high fidelity even with realistic noise based on the repeat-until-success strategy. By employing the quantum memory of the atomic internal state, the scaling efficiency decreases only with the number of atomic ensembles by a slow polynomial law. Moreover, the atomic ensembles also can function as quantum repeaters, which enable our system to compatible with the current experimental technique for quantum communication using atomic ensembles.

It is shown that, when two femtosecond chirped Gaussian pulses with equal pulse area and same size but opposite sign of the chirp coefficient, which will be simply called as double pulses, overlap and propagate in the three-level Λ-type atomic medium, both coherence between the double pulses and interaction between the double pulses and the atomic medium arise. Adjusting size of the chirp coefficient can change shape, i.e. field distribution, of the composite pulse of the double pulses, at the same time affect the interaction between the composite pulse field and atoms, and thereby control oscillation process and value of the atomic population. By selecting suitable size of the chirp coefficient, we can make the atoms at the lowest level exciting completely to the higher level; moreover the new population distribution is stationary. It is also show that, for the double pulses with any area, efficient and stable population transfer always can be realized by adjusting size of the chirp coefficient. And this conclusion doesn't vary with the pulse width or the medium density varying.

The full-width half maximum (FWHM) is one of important parameters that can exhibit the micro-cavity effect. An approximate analytic expression of spontaneous emission for GaAs micro-cavity in our previous work can be instead of the numerical integral, but it is so complex that it cannot give the analytic expression of FWHM. This paper will set up another approximation to give a new analytic expression of spontaneous emission, which can give the same results with the numerical integral in the vertical direction, in which Fermi-Dirac distribution functions of electrons in the conduction band and the valence band are considered. Although the new approximate analytic expression is simpler than that in our previous work, it can be used to study the spontaneous emission spectra FWHM with a small angle in the vertical direction of planar micro-cavity. The two approximate expressions of FWHM for enhancement spontaneous emission spectrum into the small angle are obtained by the new analytic expression of spontaneous emission, in which the triangular function relation and the first order series of sine and cosine are used respectively. The curves for the FHWM versus the reflectivity by the two expressions of FWHM in the GaAs micro-cavity are also compared.

It is known that parabolic pulses can be generated by use of a normal dispersion-decreasing fiber in a "passive" manner. However, it is more practicable and significant for the dispersion-decreasing-linearly profile to be considered than for any other profiles once actual fiber manufacture were taken into account. In this work, we investigate the process of parabolic pulse generation (PPG) in a normal dispersion-decreasing-linearly fiber (NDDLF). Based on the principle of virtual "equivalent" gain, we transform the nonlinear Schrodinger equation (NLSE) with linearly decreasing dispersion into one of the form with "hyperbolic" gain and uniform dispersion. By numerically solving the two forms of NLSE, we demonstrate that wave breaking (WB) can still take place during the evolution and the WB point is the threshold that FWM begins to take effect. The distance where WB happens can be determined by the chirp oscillations appeared in the pulse edges. Furthermore, by introducing two dimensionless structural functionals to characterize the pulse temporal and spectral shape respectively, we also illustrate that these results are in consistent with that obtained from a dispersion-decreasing-hyperbolically fiber (NDDHF) except that WB occurs much ahead and both functional values are less close to the standard "parabolic shape" value 0.0720 for comparison.

The effect of the relative phase (φ) between the probe and driving fields on the gain without inversion (GWI) is studied in a Doppler broadened quasi Λ-type four-level atomic system with vacuum induced coherence (VIC). It is shown that: The probe detuning region in which GWI exists and size of GWI are very sensitive to variation of the relative phase, the Doppler width ( D ) also has dramatically modulation role on the phase-dependent GWI. The GWI maximum value ( G_max ) varies periodically with the relative phase varying, the period is 2π; but the concrete varying rule is closely related to the value of the Doppler width. In the case of D = 0 (i.e. without Doppler broadening) , when 0 < φ < π, G_max increases monotonously with φ increasing; when π <φ < 2π, G_max decreases monotonously with φ increasing; when φ =π, G_maxhas the largest value. Under the condition of D ≠ 0 (i.e. Doppler broadening presents), in both regions 0 < φ < π and π < φ < 2π, G_max does not monotonically increase or decrease with φ increasing; the value of φ, which corresponds to the largest value of G_max, decreases gradually from π with D increasing, when value of D is large enough, the value of φ, which corresponds to the largest value of G_max, is about π/2. In general speaking, G_max decreases with D increasing; but G_max larger than that in the corresponding static atomic system ( D = 0 ) can be gotten by choosing suitable values of φ and D.

It is shown that, variation of the sign and size of the chirp coefficient (C) of the pulse has considerable effect on spectral properties of the pulse and the effect is closely relative to size of the pulse area. When the pulse with smaller area, 2π pulse, propagates in the medium, pulse splitting doesn't occur and the pulse evolves gradually to an approximate normal Gaussian pulse (C=0); new high frequency component doesn't basically appear; with increasing value of C, oscillation amplitude of blue shift and red shift components increases and blue shift component oscillates more severely; moreover, the strength of the spectral component near the central frequency decreases considerably but the strength of blue shift component increases obviously. When the 4π pulse propagates in the medium, the pulse will split into sub-pulses with different numbers and shapes, new high frequency component can be produced, but the strength of the high frequency component is smaller; similar to the case of 2π pulse, blue shift component oscillates more severely; in addition, the strength of the spectral component with higher frequency decreases evidently with increasing value of C. When the pulse with larger area, 8π pulse, propagates in the medium, the pulse splitting is similar to that in the 4π pulse case, but supercontinuum spectrum with larger strength, higher frequency and wider frequency range than that in the 4π pulse case can be obtained; varying the sign and size of C can not produce new high frequency component, but can change strength of different frequency components in the spectrum, thus can get high frequency components with higher strength

Based on the theoretical analysis on the phase-matching relations, effective nonlinear coefficients, walk-off and acceptance angles, the generation of tunable and coherent nanosecond mid-infrared radiation covering the 8-12μm range is realized by use of difference frequency generation (DFG) in a GaSe and a ZnGeP2 (ZGP) crystal. Using an 8-mm-long GaSe crystal, we achieve the mid-infrared generation that is continuously tunable from 8.28μm to 18.365μm. The maximum pulse energy is 31μJ at 8.76μm, corresponding to the conversion efficiency of 0.9% and the maximum midinfrared peak power of about 7kW. In the case of using an 8-mm-long ZGP crystal, the tuning range is from 7.2μm to 12.2μm. The maximum pulse energy is about 10μJ at 9.22μm, corresponding to the conversion efficiency of 0.45% and the peak power of 2.2kW.

We have investigated the dispersion and the nonlinearity properties of the subwavelength-diameter optical fiber (SDOF) with high-index-contrast dielectric thin films. The dispersion length and the nonlinearity length have been calculated to discuss the propagation properties of pulse in SDOF. The waveguide dispersion and nonlinearity analysis is used to guide the waveguide dimension design for possible applications. The high nonlinearity of SDOF makes it especially suitable for nonlinearity devices.

We observed experimentally one-dimensional even-number sequence of dark photovoltaic solitons in LiNbO₃:Fe crystal without additional background illumination with spatially incoherent beam that contains a dark stripe generated from an amplitude jump in the center of the incoherent beam. In experiment, we found that the initial stripe width at the entrance face of the crystal is a key parameter for generating an even-number sequence of dark incoherent photovoltaic solitons. If the initial width of the dark stripe was small, only a Y-junction soliton pair was generated. As the initial width of the dark stripe was creased to 20.1μm, the stripe can split into an even-number sequence of soliton structure. The soliton pairs far away from the center had smaller width and less visibility. In addition, the separations between adjacent dark stripes became slightly smaller than that of the Y-junction dark solitons. In particular, when the input width in the entrance face of the crystal was 30.8μm, the diffractive beam in the output face of the crystal was no longer expanding its outer boundary, but shrank its width.

Pulse compression of initial negative frequency chirp pulses in silicon photonic nanowire has been analyzed numerically. The effects of the initial negative frequency chirp and core diameter variation on pulse compression have been numerically investigated. By analyzing the interaction of SPM, positive group-velocity dispersion and the initial negative frequency chirp, we find that the compression factor increases but the quality factor and the optimum fiber length decrease with the increasing initial negative chirp when the core diameter is specified. A compression factor of 8.02 can be achieved by a pulse with initial negative frequency chirp of -20 and initial FWHM duration of 30 fs in a 4.35 μm long silicon nanowire.

The effect of the relative phase on the spectral linewidth of electromagnetically induced transparency is studied in a Λ-type three-level configuration coupled by double coupling fields and the result is presented in this paper. We show that the relative phase between the double coupling fields has a great degree of influence on the spectral width of electromagnetically induced transparency window. The linewidth can be controlled by changing the relative phase. Particularly, as the double coupling fields have opposite phases, the linewidth of EIT window can be extremely narrow distinctly.

Nonlinear upconversion emission properties in Tm and Yb codoped yttria nanocrystal have been studied under 973 nm laser excitation. Intrinsic bistability and hysteresis have been observed for the bright blue upconversion luminescence of Tm³⁺ ions at room temperature. The mechanism of the Tm³⁺ bistable emission is mainly related to laser-induced local thermal effects which cause the enhancement of sequential multi-photon energy transfer upconversion of Yb³⁺-Tm³⁺ pairs.

We present a theoretical study on the frequency position and the linetype of Electromagnetically Induced Transparency (EIT) in a four-level atomic system with a coupling field, two microwave fields and a probe field. The absorption spectrum which is characterized by two EIT windows is obtained by a weak probe field scanning corresponding transition. It can be found that the frequency position and the linetype of EIT change with the relative phase of the two microwave fields. The frequnecy interval reaches the minimum when the relative phase is reverse. If two microwave fields have the same strength and reverse phase, the absorption spectrum will exhibit an EIT. This proposes a way to controlling frequency position of EIT by modulating the relative phase between two fields.

N-Butyl-3,6-diformylcarbazole (abbreviated as b) was synthesized by the reaction of N-alkylation and the product yield was 45%. The structure was characterized by Nuclear Magnetic Resonance. Its optical properties were studied. The compound had strong fluorescence emission, and the fluorescence quantum yield was 0.40. Utilized experiment,we surveyed the effect of temperature on steady state fluorescence intensity, at 278K, 288K, 298K, 308K and 313K in DMF respectively. The measurement of the three-photon absorption (3PA) induced optical limiting effect was done in a 10-mm-long transparent quartz cell, using a Q-switched Nd: YAG laser with pulse duration of 38 ps, repetition rate of 10 Hz at 1064nm. In the case of low incident intensity, the transmittance varied linearly with incident intensity. However, the transmittance increased slowly under the condition of high incident intensity. The calculated results based on 3PA theory agreed well with the experimental results and it was inferred that the optical limiting of the compound resulted from its 3PA. The 3PA coefficient value was 6.1×10^-23 cm⁶/w² and its corresponding absorption section was 8.7×10^-79 cm⁶s².

We analyze the entanglement condition of a new kind of non-Gaussian quantum state, which is prepared by photon number subtraction from a two mode Gaussian state. Fock space criterion and Shchukin-Vogel criterion are applied and the results are compared. Two kinds of the original Gaussian states are utilized. Their photon subtracted states have different entanglement properties.

We address the issue of quantifying the non-Gaussian character of a bosonic quantum state and introduce cumulants of quantum states as the measure of non-Gaussianity. The cumulants are calculated for Fock state, cat state, non-Gaussian state prepared by photon subtraction and phase damped state. The time evolution of non-Gaussianity is also studied. The third-order cumulant is a vector of length 4 and the fourth-order cumulant is a vector of length 5 for single mode quantum state.

Phase damping is the main decoherence in the evolution of quantum states. In most of the known quantum computing and quantum information processing, devices have amplitude damping times that are around 1-2 orders of magnitude larger than the corresponding dephasing times. For lossy optical fibre as a quantum channel, the quantum capacity is well known. The channel is degradable. We know that dephasing channel is also degradable, thus it can be anticipate that the channel capacity is available. We calculate the capacity with various methods in this paper.

In order to supply a theoretical guide for digital chaotic telecommunication, the technique of Optical injection locking (OIL) of semiconductor lasers on the chaotic communication have been investigated based on the theoretical models used to describe the dynamics of solitary VCSEL subjected to the external optical injection and signal transmission in fiber. The numerical simulation results show that, the frequency chirp and time-resolved chirp are reduced in magnitude, using a VCSEL laser as master and another VCSEL as slave, it leads to a no-penalty transmission over 50 km of uncompensated in SSMF at 10Gb/s, and it could be higher rate and more remote if there were appropriate compensation.

Light speed control had been an interesting issue in recent years. In this work, the authors experimentally observed the backward propagation of light pulse in Phthalocyanin Gallium polymethyl methacrylate (PMMA) at room temperature, firstly. Taking use of the modulation technique, we got the time advancement of 260 μs when the sample length was 2 mm long and the modulation frequency was 50 Hz, the corresponding group velocity was -7.69m/s. The phenomenon of backward propagation was a direct result of negative group velocity. And the energy flow still traveled in the forward direction in the sample although the light propagated with a negative group velocity.

In this paper we present a theoretical study of the nonlinear effect in the quasi-lambda type four-level system. The system consists of an excited state level and three ground state hyperfine levels. Probing and coupling field are coupled to between the excited state and two higher ground states, and the microwave field drives the two lower ground states which are associated with probing field. By solving the precision solutions of the equations of motion of density matrix, the absorption properties as a function of Rabi frequencies of the probing field and microwave field are given. As a result, the switch from double EIT to single EIA is found due to the power broadening of probing field. However, the splitting frequency of double EIT has some connection with the Rabi frequency of microwave field.

We demonstrate the spectra of ⁸⁷Rb 5S_1/2 - 5P_3/2 - 4D_3/2 transitions by utilizing the double-resonance optical-pumping (DROP) and optical-optical double-resonance (OODR) techniques, respectively. The DROP spectrum, compared with the traditional OODR spectrum, show a much better signal-to-noise ratio (SNR). Paying special attention to the influence of alignment of lasers where the coupling and probe beams are counter-propagation and co-propagation on DROP spectrum, so as to further narrow the spectral width by means of electromagnetically induced transparency (EIT). When -the frequency of 1.5μm fiber-pigtailed butterfly-type distributed-feedback (DFB) diode laser is stabilized to the DROP spectrum of ⁸⁷Rb 5P_3/2 - 4D_3/2 transition, the preliminary result of residual frequency jitter after stabilization is ~ ±1.3 MHz within 60 s.

In our experiment, a polarization-maintaining (PM) fiber-pigtailed butterfly-sealed 1560nm distributed-feedback (DFB) laser diode is amplified by a 5-Watt EDFA, then a multiple-period PPLN crystal (1mm×10mm×20mm) and a single-period PPKTP crystal (1mm×2mm×30mm) are utilized to perform SHG via single pass configuration. The second harmonic power of ~ 239 mW@780 nm for PPLN and ~ 210 mW@780 nm for PPKTP are obtained with ~5W@1560 nm laser input, corresponding to SHG efficiency of ~ 5.2% for PPLN and ~ 4.4% for PPKTP, respectively. Finally the 1560 nm laser diode's frequency is locked to rubidium absorption line via SHG and rubidium absorption spectroscopy, the laser frequency drift for free-running case is ~ 56 MHz in 30 s, the residual frequency after being locked drift is ~ ± 3.5 MHz.

Three-wave coupled equations of optically-controlled group velocity of light based on stimulated Brillouin scattering (SBS), together with their boundary and initial conditions, are solved using finite difference method. Relations of system time delay, pulse broadening factor and changes of pulse shape with gain parameter are obtained, further more, circumstance with different stokes power, pulse width, fiber length are discussed.

We propose a method to control the polarization and magnitude of light by introducing another pump wave (control-light) in periodically poled lithium niobate (PPLN). Cascaded polarization coupling and second harmonic generation (SHG) in a single PPLN are described by the wave-coupling equations. The numerical simulations show that the control-light wave breaks the original energy coupling behavior among three waves. The results indicate that the output can be fine tuned by the phase and intensity of the control-light.

We presented an advanced design of receiver in free space quantum key distribution (QKD) system based on BB84 protocol. In this system, a novel four polarization beam splitter is used in the receiver. It simplifies the receiver fabrication process, and the reflection loss is reduced too. Then we built the transmitter and the receiver for QKD system. The outdoor 200m free space QKD experiment was carried out, the bit error rate is 0.91% when the average photon number in each optical pulse was about 0.1. This result indicates that our design for the QKD system is feasible.