Virtual Journal of Laser

Publication year: 2010
Source: Optics & Laser Technology, In Press, Corrected Proof, Available online 2 March 2010
Haiyan, Wang , Xiangyin, Li
With the help of the tensor method, the cross-spectral density matrix for the stochastic electromagnetic twist anisotropic Gaussian-Schell model (ETAGSM) beam truncated by a slit aperture propagating in turbulent atmosphere are derived. The spectral properties of this kind of beam are investigated in detail. It is shown by numerical results and analysis that the affection of the slit aperture on the spectral properties of the stochastic ETAGSM beam is obvious in the near field; while in the far field, the atmospheric turbulence plays an important role; the source beam's coherence can weaken the affection of the slit aperture and the...

Publication year: 2010
Source: Optics & Laser Technology, In Press, Corrected Proof, Available online 2 March 2010
R. Beau, Lotto , Richard, Clarke , David, Corney , Dale, Purves
Understanding perception of colour is challenging because what we see is not always what is there, which is a phenomenon we call illusions. Here we review the nature of colour vision, and the problems facing most current models and explanations. Focusing on our recent research on humans, bees and computers, we describe a new, more ecologically based explanation that provides a clear framework for why we see what we do.

Publication year: 2010
Source: Optics & Laser Technology, In Press, Corrected Proof, Available online 1 March 2010
Udaibir, Singh , Nisha, Jha , Tikendra, Prakash Singh , Avinashi, Kapoor , Alessio, Perrone
In this paper the structure, morphology and optical properties of Pd thin films deposited on glass substrate by pulse laser deposition technique at two different substrate temperatures have been investigated. The fabricated films were characterized by various methods such as XRD, AFM, and UV–vis-NIR spectroscopy. The influence of surface roughness and angle of incidence with p polarization was investigated experimentally by optical property of palladium (Pd) thin films of two different thicknesses and rms roughness from transmission measurement in the visible spectral range. It has been shown that the experimental transmittance spectra agree well with their theoretical values for absorbing...

Publication year: 2010
Source: Optics & Laser Technology, In Press, Corrected Proof, Available online 21 February 2010
Qu, Wang , Liang, Lei , Bo, Wang , Li, Chen , Jinyun, Zhou
A shift- and scale-invariant version of morphological fringe-adjusted joint transform correlation (MFJTC) is proposed in this paper, which we call shift- and scale-invariant MFJTC (SIMFJTC). SIMFJTC is combination of MFJTC and conventional radial harmonic filter (RHF). Using computer simulation, we compare the output results of SIMFJTC with those of morphological radial harmonic correlation (MRHC) and SDF-based FPFJTC when input scene is corrupted by salt-and-pepper noise and cluttered background. Our results show that SIMFJTC has higher discriminability and displays better stability against salt-and-pepper noise and cluttered background. Moreover, scale-invariance of SIMFJTC is much stricter than MRHC and SDF-based FPFJTC.

Publication year: 2010
Source: Optics & Laser Technology, In Press, Corrected Proof, Available online 21 February 2010
Sisir, Kumar Garai , Sourangshu, Mukhopadhyay
The very fast running optical memory and optical logic gates are the basic building blocks for any optical computing data processing system. Realization of a very fast memory-cell in the optical domain is very challenging. In the last two decades many methods of implementing all-optical flip-flops have been proposed. Most of these suffer from speed limitation because of low switching response of the active devices. In our present communication the authors propose a method of developing a frequency encoded memory unit based on the switching action of semiconductor optical amplifier (SOA). Nonlinear polarization rotation characters of SOA and ‘SOA based...

Publication year: 2010
Source: Optics & Laser Technology, In Press, Corrected Proof, Available online 20 February 2010
Pu, Zhou , Zejin, Liu , Yanxing, Ma , Xiaolin, Wang , Haotong, Ma , ...
We present the numerical analysis and improvement of the bandwidth of the beam phasing of fiber amplifiers using the stochastic parallel gradient descent (SPGD) algorithm. Time-varying phase distortions are incorporated into the dynamic simulation. It is shown by numerical calculation that the bandwidth of the standard SPGD algorithm is dependent on the phase distortions and on the number of lasers. The time-averaged cost function will decrease with an increase in the amplitude and frequency of phase distortions, and in the number of lasers. A cross-grouped SPGD algorithm is proposed, which offers attractive performance due to its robustness to various time-varying...

Publication year: 2010
Source: Optics & Laser Technology, In Press, Corrected Proof, Available online 18 February 2010
A., González-García , O., Pottiez , R., Grajales-Coutiño , B., Ibarra-Escamilla , E.A., Kuzin
We propose and analyse numerically a novel dispersion-imbalanced non-linear optical loop mirror (NOLM) scheme allowing simultaneous compression and amplitude noise reduction of chirped ultrashort-pulsed signals. An all-fibre distributed Gires–Tournois etalon (DGTE) made of two uniform fibre Bragg gratings is inserted asymmetrically in the loop, and is used both to dispersion imbalance the NOLM and to compress the pulses. The results show that the output pulses are accompanied by side lobes, which originate from the no-uniformity of the DGTE dispersion spectrum. We analyse the formation of these side lobes and show that, in the case of highly chirped input pulses, side...

Publication year: 2010
Source: Optics & Laser Technology, In Press, Corrected Proof, Available online 18 February 2010
Pu, Zhou , Xiaolin, Wang , Yanxing, Ma , Haotong, Ma , Xiaojun, Xu , ...
The propagation of phase-locked circular dark hollow beams array in a turbulent atmosphere is studied. An analytical expression for the average intensity distribution at the receiving plane is obtained based on the extended Huygens–Fresnel principle. The effects of turbulence, dark parameter and beam order of the beams array on the intensity pattern are studied and analyzed. It is found that the intensity pattern of the phase-locked circular dark hollow beams array will evolve from a multiple-spot-pattern into a Gaussian beam spot under the isotropic influence of the turbulence. The intensity pattern of beam array with a larger dark parameter and...

Publication year: 2010
Source: Optics & Laser Technology, In Press, Corrected Proof, Available online 18 February 2010
Ling, Ren , Lingling, Chen , Meng, Zhang , Chun, Zhou , Yue, Cai , ...
This paper reports the use of a pair of multi-cavity Gires–Tournois interferometer (GTI) mirrors in a ring cavity Ytterbium-doped fiber laser for dispersion compensation. The optical spectrum was broadened by 6nm due to the large negative group delay dispersion introduced by the light undergoing 10 round trips between the GTI mirrors. The design of the GTI mirrors and the optimisation of the layers are discussed and fabrication results are presented.

Publication year: 2010
Source: Optics & Laser Technology, In Press, Corrected Proof, Available online 16 February 2010
Hongxin, Shi , Xiudong, Sun , Suhua, Luo , Yongyuan, Jiang , Qingxin, Meng
A series of Hf:Fe:LiNbO3 crystals were grown by the Czochralski technique with various doping concentrations of HfO2. Their defect structures were analyzed by the UV–visible absorption spectra and infrared absorption spectra. The optical damage resistance of Hf:Fe:LiNbO3 crystals was measured by the photo-induced birefringence change and the transmitted light spot distortion method. The results show that the optical damage resistance ability of Hf:Fe:LiNbO3 crystals enhances remarkably with the HfO2 concentration increasing when the HfO2 concentration is lower than its threshold concentration (4mol%). However, when the HfO2 concentration exceeds its threshold concentration, the optical damage resistance ability of the crystals returns...