Optics & Laser Technology

Simulation and optimization of deep violet InGaN double quantum well laser

Publication year: 2011
Source: Optics Communications, Available online 2 December 2011
Gh. Alahyarizadeh, A.J. Ghazai, R. Rahmani, H. Mahmodi, Z. Hassan

Enhanced red-shifted radiation by pulse trapping in photonic crystal fibers with two zero-dispersion wavelengths

Publication year: 2011
Source: Optics & Laser Technology, Available online 3 December 2011
Chunfu Cheng, Youqing Wang, Yiwen Ou, Qinghua lv
A theoretical investigation on the two pulses copropagation and the red-shifted radiation generation in a photonic crystal fiber with two zero-dispersion wavelengths are presented. It is found the intensity of the red-shifted radiation components can be enhanced when the fiber is pumped with two pulses and the pulse trapping occurs. As the input peak power of the pump pulse is increased under the phenomenon of pulse trapping, the intensity of the red-shift radiation can be further enhanced. The above effects can be explained by the energy transfer from the Raman soliton to the red-shifted radiation components due to the effect of pulse trapping and the effect of higher-order dispersion.

Fiber-based chromatic confocal microscope with Gaussian fitting method

Publication year: 2011
Source: Optics & Laser Technology, Available online 3 December 2011
Ding Luo, Cuifang Kuang, Xu Liu
The chromatic confocal microscopy is an effective method for displacement measurement. However, with relatively low detection efficiency, chromatic confocal systems from previous studies suffer from either a limited measuring range or an unsatisfying resolution. In this paper, a novel chromatic confocal system is proposed based on optical fiber with large diameter that is specifically chosen to allow more light to be detected, thus greatly improving the detection efficiency of the system. To accurately locate the peak wavelength of the recorded spectrum, four data processing methods are proposed and compared, within which the Gaussian fitting model is considered best for the system. A series of experiments are done to verify the feasibility, resolution and stability of the system. An applicable measuring range of 600 μm is discovered with a highly linear range of 400 μm. The system has a high resolution close to 0.10 μm with satisfying stability shown by a long-term displacement standard deviation of 0.16 μm.

Stimulated Brillouin scattering of elliptical laser beam in collisionless plasma

Publication year: 2011
Source: Optics & Laser Technology, Available online 3 December 2011
Arvinder Singh, Keshav Walia
This paper presents an investigation of self-focusing of elliptical laser beam in collisionless plasma and its effect on stimulated Brillouin scattering. The pump beam interacts with a pre-excited ion-acoustic wave leading to Brillouin back-scattered process. The transverse intensity gradient of a pump beam generates a ponderomotive force, which modifies the background plasma density profile in a direction transverse to pump beam axis. This modification in density effects the incident laser beam, ion-acoustic wave and back-scattered beam. Non-linear differential equations for the beam width parameters of pump laser beam, ion-acoustic wave and back-scattered beam are set up and solved numerically. It is observed from the analysis that the focusing of waves enhances the SBS back-reflectivity.

Designing of an efficient multi-aperture, edge pumped thin-disk laser

Publication year: 2011
Source: Optics & Laser Technology, Available online 3 December 2011
M.J. Dashcasan, E. Barati, R. Aghbolaghi
In this article the operation of a composite Yb:YAG/YAG asymmetric hexagonal thin disk laser is optimized. This structure consists an Yb:YAG thin sheet as laser material and a diffusion bonded undoped material on top of thin sheet. Three diodes are placed outside the asymmetric hexagonal shape disk, and the emitting light is coupled via three lens ducts through its three edges and propagates through the disk along the zigzag path and repeatedly passes the gain medium, thus pump uniformity and absorption efficiency are improved. A Monte Carlo ray tracing code and Finite Element Analysis is utilized for calculation of absorbed pump density and volume temperature distribution and also thermal and mechanical stresses, respectively. Finally the output power is calculated. The triplet designing parameters, namely absorbed power efficiency, absorption uniformity and temperature distribution are optimized. Results show this edge-facet pumped geometry is a high efficient configuration for thin gain lasers.

Gaussian laser beam tailoring using acoustooptic cell

Publication year: 2011
Source: Optics & Laser Technology, Available online 3 December 2011
Abdelhalim Bencheikh, Kouider Ferria
Profile shaping of a Gaussian laser beam by an acoustic wave is well described using Collins integral and ABCD matrix formalism. It is shown by a numerical simulation that the relative width of the laser beam to the ultrasonic wavelength and the acoustic pressure inside the acoustooptic cell act on the light intensity diffraction pattern.Obtained results show that the output intensity profile differs from the incident Gaussian beam shape, and it is more broadened with an increase in the acoustic pressure. The intensity of a focused laser beam is transformed in a flat form in the central region if the acoustic pressure is proprely controlled.On the other hand the intensity longitudinal range (ILR) of the flat shape is discussed along the propagation axes, we have found the ILR is about 2 mm for a focal length distancef=100 mm.

Investigation of different surface morphologies formed on AISI 304 stainless steel via millisecond Nd:YAG pulsed laser oxidation

Publication year: 2011
Source: Optics & Laser Technology, Available online 3 December 2011
C.Y. Cui, X.G. Cui, Q. Zhao, J.D. Hu, Y.H. Liu, ...

The further investigation of the true time delay unit based on discrete fiber Bragg gratings

Publication year: 2011
Source: Optics & Laser Technology, Available online 3 December 2011
Shanguo Huang, Jie Li, Yingbo Ye, Peiming Shi, Jing Zhou, ...
A true time delay (TTD) unit based on discrete fiber Bragg gratings (FBGs) for the phased array antenna (PAA) beamforming system is further investigated using the wave interference theory. The theoretical analysis shows that a PAA system using the TTD unit based on discrete FBGs can work at high frequency as long as the FBGs can be manufactured in high precision.

Highlights

► Phased array antenna (PAA) system based on true time delay (TTD) unit is studied. ► The TTD unit is constructed by discrete fiber Bragg gratings (FBGs). ► Far field pattern of such a PAA system is analyzed by interference theory. ► Pattern is independent of the neighboring grating distance in the first fiber. ► The TTD unit based on discrete FBGs can provide high resolution time delay.

Theoretical analysis of the TE mode Cerenkov type second harmonic generation in ion-implantedX-cut lithium niobate channel waveguides

Publication year: 2011
Source: Optics & Laser Technology, Available online 2 December 2011
Guolong Du, Guiqiu Li, Shengzhi Zhao, Xin Li, Zhiyuan Yu
Optical second harmonic generation (SHG) in the form of Cerenkov radiation from ion-implanted lithium niobate (LiNbO3) channel waveguides is analyzed by directly resolving the wave equations. Useful formula of the SHG efficiency is derived and expressed in terms of waveguide parameters. Numerical examples are plotted for LiNbO3crystals. The results enable the optimization of waveguide design for efficient second harmonic generation in the Cerenkov configuration.

Highlights

► We develop a model to calculate the conversion efficiency (CE) of the Cerenkov SHG. ► The CE changes periodically with the pump wavelength and the waveguide depth. ► The model allows us to determine the optimum waveguide parameters.

Study on the feasibility of double stack high reflector coating at 355 nm

Publication year: 2011
Source: Optics & Laser Technology, Available online 2 December 2011
Hua Yu, Longqi Wu, Caifeng Liu, Jianda Shao, Zhengxiu Fan

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