一种用激光干涉测量光波波长的新方法

提出了一种利用激光干涉仪测量光波波长的方法。通过改变在光的传播路径上垂直放置的透明玻璃与光传播方向的角度,使相干光的光程差发生变化;利用干涉条纹与转过角度、透明玻璃厚度之间的关系,通过激光干涉实验能准确测量出光波的波长。     

用迈克尔逊干涉仪测量He-Ne激光波长的测量不确定度分析

针对迈克尔逊干涉实验中测出的He-Ne激光的波长值总是比真实值偏大的问题,分析了用迈克尔逊干涉仪测量He-Ne激光波长时的实验误差来源,发现实验光路调整的不理想以及仪器读数装置中残留的螺纹空程差是导致λ值偏大的主要原因。在此基础上提出了相应的改进办法,并且对测量不确定度进行了合理的估算。     

Demonstration of two-point velocity measurement using diffraction grating elements for integrated multi-point differential laser Doppler velocimeter

We have proposed a configuration of an integrated multi-point differential laser Doppler velocimeter (LDV) using arrayed waveguide gratings (AWGs) as grating elements. This paper demonstrates two-point velocity measurement using the proposed configuration with diffraction grating elements. An experiment was conducted using a free-space optical setup with bulk diffraction gratings instead of AWGs. The experimental results indicate that velocities at different positions can be measured using the proposed configuration. The measured separation of the two measurement positions was about 20.5 mm, about 11% of the working distance.     

Influence of orifice spacing on twin bubbles formation in shear-thinning fluids: Laser image measurement

A laser image system for investigating the influence of orifice spacing on twin bubbles formation in shear-thinning fluid was established. The bubbles formation process at two orifices could be directly visualized and real-time recorded through computer by means of He–Ne laser as light source using the beam expanding and light amplification technology. The shape and size of bubbles generating in carboxymethylcellulose (CMC) aqueous solutions were studied experimentally at the orifices spacing 1D_o, 2D_o and 3D_o (D_o orifice diameter). The results reveal that the minute bubbles can be imaged clearly and amplified without distortion in the higher concentration solutions, and therefore the shape and size of bubbles are obtained accurately. With the increase of orifice spacing, bubble instantaneous volume in shear-thinning fluid decreases at the radial expansion stage but then increases at vertical elongation period, and the deformation and deviation of bubbles forming goes down due to the reduced interaction of adjacent bubble.     

Laser diode to single-mode circular core dispersion-shifted/dispersion-flattened fiber excitation via hyperbolic microlens on the fiber tip: Prediction of coupling efficiency by ABCD matrix formalism

The formulated ABCD matrix formalism is employed to prescribe analytical expression of coupling efficiency of a laser diode to single-mode circular core dispersion-shifted as well as dispersion-flattened fiber via hyperbolic microlens on the tip of the fiber. We assume that field distribution in case of both the source and the fiber is one parameter Gaussian type. For maximum excitation efficiency, it is required that the lens transmitted spot size of the source should match with the spot size of the fiber. Further, as regards the spot size of the fiber, we use Petermann II spot size in order to take care of non Gaussian nature of field of such fibers and to make the estimations more realistic thereby. The investigations are carried out for two different wavelengths 1.3 and 1.5 μm. Our simple method predicts the concerned coupling optics excellently and the necessary evaluations require little computations. This simple but accurate technique is expected to benefit the system designers who work in the field of optical technology.     

Application of laser ultrasonic technique for non-contact detection of drilling-induced delamination in aeronautical composite components

The detection of drilling-induced delamination in composite components is a vital and challenging task in aviation industry. Numerous key components of aircrafts are made of composite materials, and drilling is often a final operation during assembly. Drilling-induced delamination is a very serious defect that significantly reduces the structural reliability, but it is rather difficult to be detected effectively due to its special location. A novel application of laser ultrasonic technique for the detection of drilling-induced delamination in composites is presented in this paper. A carbon fiber reinforced plastic laminate with drilling holes was made as specimen. A laser ultrasonic system was constructed and experiments were performed to detect the drilling-induced delamination, based on propagation characteristic of ultrasonic waves generated by pulse laser with a wavelength of 1064 nm and pulse duration of 10 ns. A laser interferometer based on two wave mixing is used to measure ultrasonic wave signals, and the morphology features of the delamination are imaged clearly by laser ultrasonic C-scan testing. The results proved that the laser ultrasonic technique is a feasible and effective method for the detection of drilling-induced delamination in composite components.     

Designs of all-optical NOR gates using SOA based MZI

The paper investigates the non-linear behavior of semiconductor optical amplifier with Mach–Zehnder interferometer (SOA-MZI) configuration which makes it to work as a logic gate. The two designs of NOR gate based on SOA-MZI have been verified. The basic principal of both designs are same. The summation of data pulses have been taken and inverted to perform a NOR operation. In the design, the first 3 dB coupler creates a phase difference of π/2 in clock pulse and data pulse while passing through two interferometer arms. The clock and data pulses pass through SOA which attenuates the clock pulse wherever the data pulse is present. After passing through second 3 dB coupler a phase difference of π/2 is again created. Therefore, if the clock pulse is in the same phase will be added and if it is out of phase, will be canceled. The designs have been investigated at different bit-rates to achieve higher extinction ratio (ER), Q-factor and bit-error rate (BER) for different pump currents of SOA.     

Design of fly's-eye lens for LCOS laser display

Design of optical system in laser display has always been an important research topic. From the aspect of decreasing the system volume and improving the light efficiency, it can be found that when the size of fly's-eye lens and the value of f/# are definite, the more fly's-eye arrays there are, the more useful it will be to the decrease of the optical engine size, which means that more honeycombs on fly's-eye lens and better dodging effect can be more beneficial for the decrease of the system size. After the optimal design for the rectangular elements on sub-fly's-eye lens and then doing 4000 ray tracing, the light transmittance turns out to be good with little parasitic light and scattering light.     

Context dependent graph-based method for laser cladding image thresholding

For segmentation method to be useful it must be fast, easy to use, and produce high quality segmentations, but few algorithms can offer this in various conditions and applications. In this paper, we propose a context dependent graph-based method for transition region extraction and thresholding. The graph-based approach is introduced into image thresholding, and context dependent graph is constructed from a given image, which can adaptively extract the pixel context and shape information because of the scalable neighborhood. Then an edge weight function is defined as the measure of possible transition pixels, and a robust fully automatic scheme for the optimal threshold is also presented. The proposed approach is validated both quantitatively and qualitatively. Compared with the traditional state-of-art algorithms on synthetic and real images, as well as laser cladding images, the experimental results suggest that the new proposal is efficient and effective.