Optics & Laser Technology

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

Regenerated fibre Bragg grating fabricated on high germanium concentration photosensitive fibre for sensing at high temperature

Publication year: 2011
Source: Optics & Laser Technology, Available online 30 November 2011
S.S. Chong, W.Y. Chong, S.W. Harun, H. Ahmad
A Regenerated Fibre Bragg Grating (RFBG), with repeatable high temperature response between 400 °C–1200 °C, has been demonstrated using a hydrogen-loaded, highly germanium-doped, photosensitive fibre. A wavelength shifts of as much as 20 nm is attained during temperature calibration up to 1300 °C. A large temperature response of 17 pm/°C is obtained from the RFBG, with very good repeatability.

Highlights

► Regenerated FBG (RFBG) with a repeatable high temperature response between 400 °C–1200 °C. ► The RFBG is developed from a hydrogen-loaded, highly-doped germanium photosensitive fibre. ► The RFBG has a wavelength shift of 20 nm at a maximum calibration temperature of 1300 °C. ► The RFBG has temperature sensitivities of between 17.0 pm/ °C to 17.4 pm/ °C.

Microstructure and properties of borocarburized and laser-modified 17CrNi6-6 steel

Publication year: 2011
Source: Optics & Laser Technology, Available online 30 November 2011
M. Kulka, N. Makuch, A. Pertek, A. Piasecki

Numerical investigation of soliton molecules with changeable separation in passively mode-locked fiber lasers

Publication year: 2011
Source: Optics Communications, Available online 30 November 2011
Xiaohui Li, Yishan Wang, Wei Zhao, Wei Zhang, Xiaohong Hu, ...
Soliton molecules evolution is numerically investigated in a passively mode-locked fiber laser based on the nonlinear polarization rotation (NPR) technique. Peak-to-peak separation of soliton molecules can be controlled by changing either pump strength or cavity linear phase delay appropriately. Moreover, soliton molecules with intensity-independent evolution, separation-independent evolution and large intensity-vibrating evolution are numerically found, respectively. The characteristics of soliton molecules evolution versus linear phase delay or pump strength are given. Periodic stable evolution regimes are found. The separation-controllable soliton molecules can be potentially applied in the optical communication systems.

Geometrical form factor calculation using Monte Carlo integration for lidar

Publication year: 2011
Source: Optics & Laser Technology, Available online 30 November 2011
Feiyue Mao, Wei Gong, Jun Li
We proposed a geometrical form factor (GFF) calculation using Monte Carlo integration (GFF–MC) for lidar that is practical and can be applied to any laser intensity distribution. Theoretical results have been calculated with our method based on the functions of measured, uniform and Gaussian laser intensity distribution. Two experimental GFF traces on clear days are obtained to verify the validity of the theoretical results. The results indicated that the measured distribution function outperformed the Gaussian and uniform functions. That means that the deviation of the measured laser intensity distribution from an ideal one can be too large to neglect. In addition, the theoretical GFF of the uniform distribution had a larger error than that of the Gaussian distribution. Furthermore, the effects of the inclination angle of the laser beam and the central obstruction of the support structure of the second mirror of the telescope are discussed in this study.

Hollow-core photonic crystal fiber Fabry–Perot sensor for magnetic field measurement based on magnetic fluid

Publication year: 2011
Source: Optics & Laser Technology, Available online 29 November 2011
Yong Zhao, Ri-qing Lv, Yu Ying, Qi Wang
Based on the characteristic of magnetic-controlling refractive index, the magnetic fluid filled in hollow-core photonic crystal fiber (HC-PCF) can be used as the sensitive medium in the cavity of a fiber Fabry–Perot (F–P) magnetic field sensor. The structure and the sensor principle are introduced. The theoretical simulations of the mode distribution of the HC-PCF filled with the magnetic fluid and the sensor output spectra are discussed in detail. The sensor multiplexing capability is indicated as well. Magnetic field measurement sensitivity is about 33 pm/Oe based on the proposed sensor.

Highlights

► A magnetic sensor is proposed based on an HC-PCF filled with magnetic fluid (MF). ► The principle is the characteristic of magnetic-controlling refractive index of the MF. ► Magnetic field measurement sensitivity is about 33 pm/Oe.

Inspection of cracks using laser-induced ultrasound with shadow method: Modeling and validation

Publication year: 2011
Source: Optics & Laser Technology, Available online 29 November 2011
Cuixiang Pei, Kazuyuki Demachi, Haitao Zhu, Tetsuo Fukuchi, Kazuyoshi Koyama, ...
A numerical model based on the finite element method (FEM) is developed for crack inspection using laser-induced ultrasonic waves with the shadow method. Before the simulation, the numerical code is verified by comparing the directivity patterns of ultrasonic waves with the experiment. The use of thermo-elastically generated ultrasonic waves for crack detection and evaluation with the shadow method is investigated by simulation. The simulation is validated by comparing with the experiment.

Highlights

► A numerical model is developed for crack inspection with laser ultrasonic. ► The possibility of the “inner” crack inspection with thermo-elastic waves is investigated. ► The crack at the rear side of the specimen was detected and evaluated by shadow method.

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