In this letter, we propose a method for the numerical calculations of the femtosecond laser pulse passed through a subwavelength aperture. The time-dependent laser pulse is decomposed into a series of monochromatic simple harmonic waves.For the light field of the harmonic wave with a single frequency, the numerical calculation is made based on the solutionof the Green's integral equation set of the electromagnetic waves. Such numerical solution is iterated for all the waves withdifferent frequencies, and all the numerical solutions are transformed into the light fields in the time domain by inverse Fourier transform. The light intensity distributions transmitted the subwavelength aperture are calculated and the results show the propagation of the light field is along the direction of the medium interface.

Rhodamine 6G-doped step-index polymer optical fiber is fabricated. The characteristics of the amplification of rhodamine 6G-doped step-index polymer optical fiber amplifier have been studied. The high-gain optical amplification with a tunable wavelength range from 585 to 613 nm is obtained in a step-index polymer optical fiber doped with rhodamine 6G at 10-ppm level, which can be used for broadband amplifiers and tunable lasers.

A Fabry-Perot (F-P) etalon and a semiconductor optical amplifier (SOA) were combined to preprocess the data signals before clock recovery. With this technology in the 10-Gb/s clock recovery utilizing injection mode-locked laser (IMLL) based on SOA, the amplitude fluctuation and timing jitters caused by the pattern effect in recovered clock pulses were greatly reduced, experimentally. It also demonstrated that clock could be recovered from the very degraded signals.

We present an expression of maximum fiber-link length, at which the output pulses can return to its original rms time width, in an optical fiber link with up to fourth-order dispersion. The fourth order dispersion is compensated by combination of the effects of proper source chirping and negative residual second-order dispersion. The interesting fact is that the optical pulses can restore itself at a longest distance even in case of chirp parameter being positive, as well as being negative traditionally. The validity of the analytical formulas is also confirmed by split-step Fourier numerical stimulation.

The influence on photonic crystal fiber dispersion of the size of air holes in different rings within the cladding is investigated using a semivectorial finite difference method. Numerical results reveal that the photonic crystal fiber dispersion is more sensitive to the variation of the air hole size in the first and second rings, indicating that design of photonic crystal fibers with desirable dispersion properties requires more precise control of the parameters of the air holes in the vicinity of the fiber core.

A novel symbol overlapping optical fast frequency-hop code-division multiple access (FFH-OCDMA) system is proposed, and its bit error rate (BER) performance is investigated under consideration of avalanche photonic diode (APD) noise and thermal noise. An experimental symbol overlapping (SO) FFH-OCDMA testbed is developed and some experimental results are given. The theoretical and experimental results show that the system is apt to implement and has larger throughput.

Due to the limited depth-of-field of optical lenses, it is difficult to get an image with all objects in focus. One way to overcome this problem is to take several images with different focus points and combine them into a single composite which contains all the regions full focused. This paper describesa pixel-clarity-based multifocus image fusion algorithm. The characteristic of this approach is that the pixels of the fused image are selected from the clearest pixels in the input images according to pixel clarity criteria. For each pixel in the source images, the pixel clarity is calculated. The fusion procedure is performed by a selection mode according to the magnitude of pixel clarity. Consistency verification is performed on the selected pixels. Experiments show that the proposed algorithm works well in multifocus image fusion.

In this paper a detailed simulation and theoretical analysis based on model-solid theory and the k.p method are presented to investigate the dependence of the band structure on the strain deformation in a novel type-II quantum well (QW) heterostructure InAs_{1-y}Sb_{y}/Ga_{x}In_{1-x}Sb under the uniaxial approximation, and subsequently the optical transition and the gain in the interband cascade lasers containing it have been evaluated with unchanged injection current densities. The simulation results show that the strain effect on the transition in this heterostructure will not behave as a simple monotonic trend with the lattice mismatch of InAs_{1-y}Sb_{y}/Ga_{x}In_{1-x}Sb interface, but as a function of the complex strain chain including the whole active region. It is important to the subsequent device design and optimization.

A master-oscillator fiber power amplifier (MOPA) system is presented, which consists of a single mode laser as the master oscillator and an Yb^{3+}$-doped large-mode-area double-clad fiber as the power amplifier. The system emits up to 6 W of amplified radiation at a wavelength of 1064 nm. The slope efficiency and extracted pulse energy as a function of pulse repetition rate are analyzed.

An electro-optically Q-switched partial Z-folded RF CO_{2} waveguide laser with an intracavity CdTe modulator has been designed and characterized. The partial Z-fold channel is 3*460 mm in length. In this paper we study the laser output power as a function of gas pressure for partial Z-fold channel without Q-switched crystal inside the cavity. The maximum laser output power is about 21 W. For Q-switch operation, the peak power is 730 W and the pulse width is 150 ns.

By measuring the absorption and fluorescence spectra and the fluorescence lifetime of ^{4}F_{3/2} state of Nd^{3+} ions in YVO_{4} (2 at.-{\%}) crystal at different temperature, the effects of temperature on the spectra and the lifetime of ^{4}F_{3/2} state have been investigated. As the temperature is increased, the line width of the ^{4}F_{3/2}--&gt^4I_{11/2} transitions is found to increase and the spectral line toward the longer wavelength, which are duo to the ion-phonon interaction. The variation fluorescence lifetime of the ^{4}F_{3/2} state of Nd:YVO_{4} is found to be anomalous in the measured range 8-300 K. It is about 81 us at room temperature and decreases to 30 us at 8 K. The experimental results are explained by ascribing to the thermal mixing between the two Stark levels of ^{4}F_{3/2} state with different lifetime.

Erbium-doped glass showing the wider 1.5-um emission band is reported in a novel oxide system TeO_{2}-WO_{3}-Nb_{2}O_{5} and their thermal stability and optical properties such as absorption, emission spectra, cross-sections and fluorescence lifetime were investigated. Compared with other glass hosts, the gain bandwidth properties of Er^{3+} in TWN glass is close to that of bismuth glasses, and larger than those of tellurite, germanate, silicate and phosphate glasses. The broad and flat ^{4}I_{13/2}--&gt^{4}I_{15/2} emission and the large stimulated emission cross-section of Er$^{3 + }$ ions around 1.5um can be used as host material for potential broadband optical amplifier in the wavelength-division-multiplexing (WDM) network system.

We have performed time-resolved degenerate four-wave mixing (DFWM) experiments in 75Nb_{2}O_{5 }-20TeO_{2}-5ZnO glasses dopedby Er_{2}O_{3} at different excitation intensities and lattice temperatures. DFWM signal exhibits three peaks at high excitation intensities, where a main peak appears at zero time delay and two rather weak side peaks locate symmetrically at the negative and positive time delay, respectively. The main peak is attributed to local-field effect and two side peaks areattributed to Coulomb interaction (CI).

Diamond films were deposited in microwave plasma chemical vapor deposition (MPCVD) method on plain silicon substrates with (100) orientation. And the pinhole defects on them were investigated by optical microscopy and scanning electron microscopy (SEM). X-ray masks were fabricated with the films deposited by us. We found the pinhole defects in the film destroyed the gold absorber. The corrosion-resistance tests conducted in 30% KOH solution under 80 oC showed that the diamond films with pinhole defects have lower corrosion-resistance. In addition, the possible mechanism of the formation of pinhole defects in diamond films was discussed. And we deduced that the defects on substrates, competitive growth of multi-phase in diamond films, lattice dislocation between substrates and diamond films could be associated with the defect formation.

A design and testing of a cost-effective distributed optical remote sensing methane system, which will help one to detect gas leaks from multi-coal face in mines simultaneously, is presented. The fundamentals of the remote detection are based on frequency-modulation spectroscopy (FMS) and harmonic detection. By utilizing fiber-optic splitting technique and reference-signal restoring circuit, the remote sensing system is feasible to employ single laser source to get multi-spot measurement in the near infrared region so that the system described here shows sufficient sensibility, considerably increased reliability and marketability over the presently available system. The minimum measurable path-integrated concentration is estimated to be about 423 ppb-m by experimentation.

A novel design of a transverse magnetic (TM)-pass waveguide polarizer based on Si on an X-cut, Y-propagation Ti:LiNbO3 planar waveguide is presented. The eigenvalue functions of such structure have been obtained by using Wenzel-Kramers-Brillouin (WKB) method with modified Airy functions. The intervals of the silicon thickness have been found which result in transverse electric (TE) light suffering strong attenuation while TM wave propagating with fairly low loss. A planar waveguide polarizer is fabricated and its polarization-dependent measurements lead to the best polarization extinction ratio ~34 dB and the insertion loss <0.4 dB.

In this paper, the Raman spectrum signal de-noising based on stationary wavelet transform is discussed. Haar wavelet is selected to decompose the Raman spectrum signal for several levels based on stationary wavelet transform. The noise mean square {sigma}_j is estimated by the wavelet details at every level, and the wavelet details toward 0 by a threshold {sigma}_j (2\ln n)^{1/2} , where n is length of the detail, then recovery signal is reconstructed. Experimental results show this method not only suppresses noise effectively, but also preserves as many target characteristics of original signal as possible. This de-noising method offers a very attractive alternative to Raman spectrum signal noise suppress.

The writing of an internal diffraction grating in optical glass plate is demonstrated using low-density plasma formation excited by a high-intensity femtosecond Ti:sapphire laser. The same diffraction efficiency at +-1, +-2, and 0 order isachieved by multiple layers writing. The dependences of diffractive efficiency on the irradiated energy, the speed of writing, the numerical aperture (NA) of the focusing objective, and materials are investigated in detail. The grating isbirefringent. It is attributed to residual stress interaction between glass and femtosecond laser pulse.

We demonstrate the generation of supercontinuum (SC) of over 1350 nm by injecting 790-nm, 15-fs, 74-MHz optical pulses into a 183-mm-long microstructured fiber with combination core and random cladding. The maximum total power of SC is 73 mW with 290-mW pump power from 40* microscope objective. The wavelength and power ranging in SC as well as the polarization states and waveguide modes of the visible light can be tuned by adjusting the input end of MF. In particular, white light has been observed. To our knowledge, this is the first report of tunable properties in SC generation process using microstructured fiber with combination core and random cladding.