Lidar is an efficienttool for remote monitoring, but the effective range is often limited by signal-to-noise ratio (SNR). By the power spectralestimation, we find that digital filters are not fit for processing lidar signals buried in noise. In this paper, we present a new method of the lidar signal acquisition based on the wavelet trimmed thresholding technique to increase the effective range of lidar measurements. The performance of our method is investigated by detecting the real signals in noise. Theexperiment results show that our approach is superior to the traditional methods such as Butterworth filter.

We report a laser writing system for fabrication of diffractive optical elements with He-Cd laser. The wavelength of the light source is 441.6 nm. The output beam is collimated into parallel light with uniform intensity distribution after passing through the spatial filter with a pinhole of 25 um and the collimating device. A microscopy objective lens with numerical aperture (NA) of 0.65 is used to focus the beam into a small diffraction spot. Any pattern can be written with this system. Experimental results are presented. The written gratings and the phase patterns were verified with a conventional optical microscopy and the Taylor Hobson equipment.

We experimentally demonstrate a novel multiwavelength continuous wave (CW) optical source with precise 25-GHz spacing based on the longitudinal mode-carving of a supercontinuum (SC) spectrum. The CW light was modulated with a 10-Gb/s non-return zero (NRZ) format. The experimental results show that the multiwavelength CW optical source is promising for dense wavelength division multiplexing (DWDM) systems.

In this paper, a novel structure erbium-doped fiber laser with a linear cavity is demonstrated. The wavelength selective devices are a fiber Bragg grating (FBG) and a high birefringence (HiBi) fiber loop mirror. From 1543.8 to 1555.2 nm, 15 lasering wavelengths with side mode suppresion ratio (SMSR) >54 dB and approximately 0.8-nm spacing have been obtained by using the comb-like reflection spectrum of fiber loop mirror and the intensity reaches about 2.5 dBm on an average. The reflectivity at different wavelengths can be tuned with different settings of polarization controller and the relative laser intensity can be controlled over a dynamic range of 13.5 dB.

The Er-doped concentric-cores dispersion compensating fiber (EDDCF) has been demonstrated. The rare earth has been doped as a ring around the inner core. We have obtained 14-dB gain at 1550 nm (using 100-mW pump power and 980-nm wavelength) with dispersion of about -165 ps/(km.nm). It is useful for the optical fiber network where amplification as well as negative dispersion are necessary.

A new kind of tunable optical filter is proposed for DWDM optical communication application. It is based on cascaded polarization interference filter (PIF). The period and bandpass width of each PIF are decided by its optical path difference between o-ray and e-ray (OPDOE). When their OPDOEs are proportionately designed, the tuning range and bandpass width depend on OPDOE in the first and the last PIF, respectively. The tuning range, bandpass width and crosstalk are independent each other. The crosstalk is related to the OPDOE ratios among PIFs and can be suppressed by designing the PIF's OPDOE. A set of OPDOE is suggested that are l_1, 2* l_1, 2^2* l_1, 2^3* l_1, 2^4* l_1, ..., 2^{N-4}* l_1, 15*2^{N-7}* l_1, 10*2^{N-6}* l_1 and 2^{N-2}* l_1 from the first to the last. This suggested OPDOEs can yield -50-dB crosstalk for any tuning range and bandpass width. The insert loss is less than 1 dB. As its loose alignment requirement, there is no limitation on cascaded PIF number. When 11 PIFs are cascaded, it can achieve 170-nm tuning range, -50-dB crosstalk, bandpass width applicable to 25-GHz channel spacing and 1 dB insert loss.

The analysis of the group delay ripple (GDR) generated by chirped fiber gratings is developed based on the Fabry-Perot (F-P) resonator. It shows clearly how the GDR is generated and why the periods of GDR varies along the chirped fiber gratings. It could also explain why apodization could suppress the GDR and how apodization affects the chirp of the grating. The theory could be used to devise the apodization of fiber gratings.

The performance of the algorithm of the data channel scheduling algorithm of latest available unscheduled channel with void filling (LAUC-VF) under bursty traffic is presented firstly. A bursty traffic model for optical burst switch performance simulation is also introduced.

A method has been developed in this paper to gain effective speckle reduction in medical ultrasound images. To exploit full knowledge of the speckle distribution, here maximum likelihood was used to estimate speckle parameters corresponding to its statistical mode. Then the results were incorporated into the nonlinear anisotropic diffusion to achieve adaptive speckle reduction. Verified with simulated and ultrasound images, we show that this algorithm is capable of enhancing features of clinical interest and reduces speckle noise more efficiently than just applying classical filters. To avoid edge contribution, changes of contrast-to-noise ratio of different regions are also compared to investigate the performance of this approach.

In order to measure spatially and temporarily resolved laser-produced plasma X-ray spectra in 0.2-2 nm region, a novel two-channel elliptically-bent crystal spectrograph has been developed. Dispersive elements are LiF, PET, Mica, and KAP crystals, which cover Bragg angles in the range of 30-67.5 degrees. Eccentricity and focal distance of twin ellipses are 0.9586 and 1350 mm, respectively. Spatially resolved spectrum is photographically recorded with an X-ray film or X-CCD camera in one channel, and temporarily resolved one is photographically recorded with an X-ray streak camera in another channel, thus spatially and temporarily resolved spectra can be simultaneously obtained. Spectral images were acquired with X-CCD and PET in SHENGUANG-II laser facility, and experimental results show that the spectral resolution of the spectrograph is about 0.002 nm.

The diode-pumped Nd:Y_(x)Gd_(1-x)VO_(4) crystal continuous wave (CW) laser operating at 1.06 um with a simple plane-concave cavity and a "V-shaped" folded cavity for intracavity frequency-doubling have been studied. With the incident pump power of 8 W, an output power (1.06 um) of 3.4 W was achieved, giving an optical conversion efficiency of 42.5%. 884 mW of stable green radiation was generated with the incident pump power of 5.9 W, giving an optical conversion efficiency of 15%.

We reported a passive Q-switched diode laser pumped Yb:YAG microchip laser with an ion-implanted semi-insulating GaAs wafer. The wafer was implanted with 400-keV As^(+) in the concentration of 10^(16) ions/cm^(2). To decrease the non-saturable loss, we annealed the ion-implanted GaAs at 500 oC for 5 minutes and coated both sides of the ion-implanted GaAs with antireflection (AR) and highreflection (HR) films, respectively. Using GaAs wafer as an absorber and an output coupler, we obtained 52-ns pulse duration of single pulse.

High-power and high-efficiency operation of an all-solid-state, quasi-continuous-wave, titanium sapphire laser is obtained with a diode-laser-pumped frequency-doubled Nd:YAG laser as the pump source. A maximum output power of 2.5 W is obtained for 16-W power of 532-nm pump light. A much higher conversion efficiency of 15.7% is obtained when at the maximum output power.

An optical ultra-short pulse train with a duration of 2.9 ps was successfully generated from a passively mode-locked laser diode. The time-bandwidth product was 0.43, and it was very close to the transform-limited value of a Gaussian waveform. The highest peak power of 10 mW in an InP-based passively mode-locked laser has been achieved. The laser is promisng as an optical source for an ultra-high-speed bit rate transmission system, especially for the optical time division multiplexing (OTDM) system.

In this experiment, we used 7-kW continuous wave (CW) CO_(2) low order mode laser and YAG impulse laser to deeply weld high-speed steel (W18Cr4V) and spring steel (65Mn). To welded joint, we analyzed its microstructure, micro hardness and fracture appearance for different welding technology by metallography microscope, scanning electron microscopy and bending strength test, discussed its action of fracture and the relation between its structural transformation and strength. At last, we offered an optimum welding technology having no welding defect by the comparison and analysis of processing property.

Photoluminescent properties of a metal-organic complex, di(8-hydroxyquinolato) zinc, impregnated in nanoporous glass were investigated. In comparison with those in the normal organic fluorescent material, the emission band of the impregnated organic phosphor became wider. Blueshift (14 nm) was observed due to (pi)*-->n emission transition. The excitation band of the embedded organic phosphor had a larger blueshift and was divided into several sub-bands. The intensity in the short wavelength end of the embedded organic fluorescent material became much stronger.

With 4.28-km dispersion-flattened fiber (DFF), more than 254.9-nm 10-dB bandwidth on the right side of zero-dispersion wavelength and a 190.4-nm wide spectral region with the uniformity of within +-0.5 dB are obtained. While on the opposite side, 198.4-nm 10-dB bandwidth and 62.3-nm spectral region with the uniformity of within +-0.5 dB are obtained. More than 88 channels spaced at 2.52 nm on the long wavelength side are generated using Fabry-Perot (F-P) filter. The output supercontinuum (SC) characteristic is also analyzed by spectrum carving.

The third-order susceptibility of In_(x)Ga_(1-x)N/GaN quantum well (QW) has been investigated by taking into account the strain-induced piezoelectric (PZ) field, and the effective-mass Schrodinger equation is solved numerically. It is shown thatthe third-order susceptibility for third harmonic generation (THG) of In_(x)Ga_(1-x)N/GaN QW is related to indium content in QW and the intensity of the PZ field. The characteristics of \chi^(3)_(THG)(-3\omega, \omega, \omega, \omega) as the function of the wavelength of incident beam, well width and indium content, have been analyzed.

We investigated nonlinear optical properties of ZnO-Nb_(2)O_(5)-TeO_(2) glass excited by a femtosecond laser with time-resolved four-wave mixing (FWM) technique. The unusual FWM signals were observed in samples with ZnO dopant. The mechanism for the optical nonlinearities was discussed.

Our study shows that for the copropagating probing and driving fields, the gain without inversion doesn't monotonously decrease or increase with the increasement of Doppler width. When the driving field is resonant, at a suitable Doppler width, we can get a maximum value of the gain without inversion, which is much larger than that obtained when Doppler broadening is absent.

We present two optimal schemes for non-local implementing a single-qubit rotation operation via a maximally entangled quantum channel. We report on the quantitative relations between the quantum action, entangled and classical communication resources required in the implementation. We also put forward two schemes for conclusive implementing the non-local quantum single-qubit rotation via a partially entangled quantum channel. Both these methods can appropriately be referred to as qubit-assisted processes.