The significant variation of the laser output can be caused by feedback of a small part of laser beam, which is reflected or backscattered by a target at a long distance from laser source, into the laser cavity. This paper describes and analyzes theoretically and experimentally the influence of atmospheric turbulence on interference caused by laser feedback. The influence depends upon both the energy of feedback into the laser cavity and the strength of turbulence over a laser propagation path in the atmosphere. In the case of stronger energy of feedback and weak turbulence variance of fluctuation of the laser output can be enhanced by hundreds to thousands times. From our measurements and theoretical analysis it shows thatthese significant enhancements can result from the change of laser-cavity-modes which can be stimulated simultaneously and from beat oscillations between a variety of frequencies of laser modes. This also can result from optical chaos inside the laser resonator because a non-separable distorted external cavity can become a prerequisite for optical chaos.

Stimulated-Raman-adiabatic-passage (STIRAP) process provides an effective technique to transfer electron population from an initial state (e.g. ground state) to excited final state for both atoms and molecules. In this paper, we present the results of the study on electron population transfer in three level system. We have analyzed the effects of various conditions on the transfer process, such as the time delay of the two laser beams, two-photon off-resonance, one-photon off-resonance and the change of relative laser intensity. The numerical result is compared with experiment, and the reasons for the effects are also given.

Heat treatment with the presence of hydrogen (H_(2)) that react with GeE0 centers (·Ge ≡) at high temperature will weaken the refractive index modulation of grating fabricated in hydrogen-loaded normal germanosilicate fiber. Pre-annealing treatment of the above fiber was demonstrated to be able to enhance the grating’s thermal stability effectively. 0.37-nm blue-shift of the reflected Bragg wavelength was observed.

Virtual topology of WDM optical networks is often designed for some specific traffic matrix to get the best network performance. When traffic demand imposed on WDM optical networks changes, the network performance may degrade and even become unacceptable. So virtual topology need to be reconfigured. In previous works, virtual topology is reconfigured to achieve the best network performance, in which a large number of lightpaths need to be set up or torn down. In this paper, we try to get a tradeoff between the network performance and traffic disruption (or implementing cost). The problem of virtual topologyreconfiguration for changing traffic patterns is formulated as an optimization problem and a mixed integer linear programming (MILP) algorithm is presented. Numerical results show that a large cost reduction of reconfiguration can be achieved at the expense of network performance.

In dense wavelength division multiplexing (DWDM) optical transmission systems, cross-phase modulation (XPM) due to Kerr effect causes phase shift on each channel, which will ultimately be transformed to amplitude noise that leads to power penalties. In this letter, the XPM-induced penalty in multi-channel DWDM systems is investigated theoretically and an applied algorithm that can be practically used in engineering design is proposed.

This letter proposes a new burst assembly technique for supporting QoS in optical burst switching (OBS) networks. It consists of the adaptive-threshold burst assembly mechanism and QoS-based random offsettime scheme. The assembly mechanism, which is fit well to multi-class burst assembly, not only matches with IP QoS mechanism based on packet classification, and also utilizes fairly and efficiently assembly capacity. Based on token-bucket model and burst segment selective discard (BSSD), the offset-time scheme can smooth the traffic to support OBS QoS. The simulation results show that the technique can improvethe performance in terms of packet loss probability (PLP).

This paper proposes a novel scheme based on minimum delay at the edges (MDE) for optical burst switching (OBS) networks. This scheme is designed to overcome the long delay at the edge nodes of OBS networks. The MDE scheme features simultaneous burst assembly, channel scheduling, and pre-transmission of control packet. It also features estimated setup and explicit release (ESXR) signaling protocol. The MDE scheme can minimize the delay at the edge nodes for data packets, and improve the end-to-end latency performance for OBS networks. In addition, comparing with the conventional scheme, the performances of the MDE scheme are analyzed in this paper.

In this paper, the morphological filter based on parametric edge detection is presented and applied to imaging ladar image with speckle noise. This algorithm and Laplacian of Gaussian (LOG) operator are compared on edge detection. The experimental results indicate the superior performance of this kind of the edge detection.

Many approaches for high-resolution image reconstruction have been proposed in some literatures. One of the most commonly ways is to reconstruct a high-resolution image from a number of rotated and translated images with low resolution. In this process, the exposure difference among original images will decrease the quality of the reconstructed image. In order to remove the influence of the exposure difference, a light energy matching method is proposed in this paper. The theoretical analysis is illustrated in details. Experimental results show that the theoretical analysis is correct and the proposed method is valid.

Based on total reflection principle, a compact liquid-refractive index measuring equipment was designed and fabricated, in which a diode laser was used as light source and a charge-coupled device (CCD) as photodetector. The influence on measurement accuracy of the wavelength shift and intensity fluctuation of the diode laser were surmounted by an effective feedback method. It is crucial whether the diode laser could be used in such a system.

A liquid-nitrogen-cooled Tm, Ho:YLF laser is constructed with a 10-mm-long Tm(6%) and Ho(0.5%) codoped yttrium lithium fluoride crystal pumped by a laser diode operating at 792 nm. The laser output power is improved by cooling the Tm, Ho:YLF crystal from 300 to 77 K. When the crystal is kept at 77 K, the laser threshold pump power is 230 mW, the slope efficiency is 27.4%, and the maximum optical-tooptical efficiency is 19.9%. At the same time, the relation between the input power and the output power at different temperatures is obtained.

The nonlinear optical loop mirror (NOLM) is used as a saturable absorbed to reshape pulses. Experimentally, an actively mode-locked erbium-doped fiber ring laser with figure-eight structure is set up. 2 ─ 4 order harmonic pulse train with stable amplitude has been obtained when the RF modulation frequency is about 2.5 GHz.

We present a 10-GHz hybrid actively and passively mode-locked fiber ring laser with a dispersion imbalanced nonlinear loop mirror (DI-NOLM), whose nonlinear switching characteristic can make the laser operate at additive pulse modelocking (APM) mode or additive pulse limiting (APL) mode. When the laser operated at APM, 5.45 ps of transform-limited pulse series were obtained. When the laser was biased at APL region, supermode noise was suppressed and the laser output was more stable.

A quasi-continuous-wave intracavity frequency-doubled Nd:YAG laser which operates at 660 nm is studied. By using a flat-flat laser cavity, 2 Kr-lamps, KTP crystal and an acousto-optically Q-switch, 2-W output power at 660 nm is obtained. The relationship between laser cavity length and output power is analyzed.

Development of nuclear pumped lasers (NPL) in the CFBR-II reactor is briefly reviewed. The results of the two NPL experiments in CFBR-II reactor are described. The first one focused on the principle of nuclear pumped laser, and 4-mW laser output power achieved. The second NPL experiment focused on the small signal gain and the efficiency of the nuclear pumped He-Ar-Xe gas mixture at 1.73 μm. The maximum laser power measured to be 45 mW when thermal neutron flux rate is 6.9 * 1014 cm^(-2)·s^(-1). The small signal gain at 1.73 μm by the Rigrod analysis method is to be 0.24%·cm^(-1), and the saturation intensity is fitted to be 36 W/cm^(2).

Er^(3+)-doped heavy metal borosilicate glasses were prepared using conventional melting and quenching method. The emission spectra of (4)^I_(13/2) → (4)^I_(15/2) transition were observed upon excitation at 974 nm and the lifetime of (4)^I_(13/2) level of Er^(3+) was measured. Based on these data, the fluorescence properties of Er^(3+) are investigated on the emission and gain characteristics at the 1.5 μm bands. In particular, the effect of relative heavy metal content on fluorescence properties is discussed.

P_(2)O_(5).BaO.Na_(2)O.K_(2)O glasses doped with various content of Eu_(2)O_(3) were prepared using high temperature melting method, and the Eu^(2+) ions in the phosphate glasses were obtained with the aid of the reductive action of silicon powder. The fabricating conditions, fluorescence, excitation spectra of the glasses were then studied. The glasses containing europium show a broad emission band at 450 nm and sharp bands from 580 to 650 nm, and the co-existence of Eu^(2+) and Eu^(3+) is identified. Also, a good glass with a dominant proportion and large quantity of Eu^(2+) ions can be obtained by the reductive action of silicon powder and proper processing.

Direct calculations of absorption spectra for multi-quantum well structures by extracting field distributions at well positions are performed. Results demonstrate the previously reported Bragg suppression, and agree exactly with the indirect calculation by linear dispersion theory. This reveals that Bragg suppression effect in fact originates from the remarkably decreased intensities at well positions by Bragg interference condition, rather than from the formation of supperradiant modes.

The off-plane propagation of electromagnetic (EM) waves in a two-dimensional (2D) graphite photonic crystal structure was studied using transfer matrix method. Transmission spectra calculations indicate that such a 2D structure has a common band gap from 0.202 to 0.2035 c/a for both H and E polarizations and for all off-plane angles form 0° up to 90°. The presence of such an absolute band gap implies that 2D graphite photonic crystal, which is much easier and more feasible to fabricate, can exhibit some properties of a three-dimensional (3D) photonic crystal.

Ag-MgF_(2) cermet films with different Ag fractions were prepared by vacuum evaporation. The microstructure of the films was examined by Raman scattering technique. The surface-enhanced Raman spectrum for MgF_(2) molecules in the cermet film strongly suggests the existence of Ag nanoparticles dispersed in MgF_(2) matrix. The intensities of the Raman spectra of Ag-MgF_(2) cermet films increase with Ag fraction. The enhancement of Raman scattering disappears when Ag content reaches wt.20%. The analyses with the transmission electron microscopy showed that Ag-MgF_(2) cermet films are mainly composed of amorphous MgF_(2) matrix with embedded faced-center-cubic Ag nanoparticles. It suggests that the percolation threshold should be around wt.20% of Ag content.

We observe enhanced terahertz (THz) radiation generated from a Si_(3)N_(4) film-coated GaAs photoconductive dipole antenna. Compared to an uncoated antenna with identical electrode geometry and optical excitation power, the Si_(3)N_(4) film-coated antenna has a higher effective DC resistance and larger breakdown voltage. As a result, the peak amplitude of generated THz radiation is significantly enhanced due to the Si_(3)N_(4) film-coated layer.