Acousto-optic Light Pulse Shaper for Measuring the Parameters of Photo-detectors

The paper emphasizes that intensive utilization of the optical range increases the need for the development of new optoelectronic devices. Accordingly, there is a growth in the need for effective methods and tools to study photoelectric properties of semiconductor materials, including photo-detectors.In the paper we have analyzed the well-known methods and tools for measuring the photo-detector parameters, defined the restrictions in their applications, and proved that it is relevant to create a measuring system, the parameters of which are easily adapted to the study of photoelectric characteristics of a wide range of semiconductor materials, including photo-detectors.The scheme and principle of operation of the acousto-optic processor and the features of the photo-elastic effect are discussed, and it is proved that they can be used to form a light pulse of required duration and power. The expressions obtained for calculating the response at the acousto-optic processor output enable us to estimate separately the effects of time of crossing the optical beam by the elastic wave packet and the photo-detector inertia.The capability to determine the time of crossing the optical beam by the elastic wave packet and taking it into account as a device error has been substantiated. The proposed formulas have been tested and by numerical analysis based on the datasheet specifications of the FD-24K photodiode, the effectiveness of the obtained expressions has been convincingly proven.The inertia parameters of a particular sample of the FD-24K photodiode are experimentally studied. The emphasis is upon measuring the rise time of the transient response of the object under study. The exact rise time value of the transient response of the experimental FD-24K sample was approximately 7 μs, which is less than that indicated (≤10 μs) in the product certificate. In real life, such a measurement is necessary when selecting the photodiode pairs with identical parameters.By comparing the results of numerical analysis and experimental studies, it has been convincingly proven that the features of the photo-elastic effect can be used to construct a light pulse shaper with the required parameters.

Download Full-text

Photo-elastic Effect Features Used for Measuring Laser Radiation Parameters

Radio Engineering ◽

10.36027/rdeng.0420.0000159 ◽

2020 ◽

pp. 17-29

Author(s):

A. R. Hasanov ◽

R. A. Hasanov ◽

A. Q. Huseynov ◽

E. A. Agayev ◽

R. A. Ahmadov

Keyword(s):

Wave Packet ◽

Elastic Wave ◽

Pulse Duration ◽

Direct Detection ◽

Input Pulse ◽

Experimental Studies ◽

Elastic Interaction ◽

Optical Beam ◽

Practical Applications ◽

Elastic Effect

The article discusses the photo-elastic effect features in acousto-optic processors for processing pulse signals on the time axis. The photo-elastic interaction in these devices is divided into two areas. In the first area, the input pulse duration is longer than the time of intersecting the optical beam by the elastic wave packet. This particular area is widely used in the practical applications of these processors, where it is a priori assumed that the input pulse duration is longer than the time for the elastic wave packet to intersect the optical beam.In the second area, the input pulse duration is less than the time for the optical beam to be intersected by the elastic wave packet. The objective of this work is to study the photo-elastic effect features in this area. It was established that in this area the pulse duration at the processor output is equal to the time for the optical beam to be intersected by the elastic wave packet and does not depend on the input pulse duration, which is permissible in some cases (for example, in radar pulse existence rather than its duration is recorded). It is shown that in the second area, the output pulse is formed as the sum of three terms. The first term corresponds to the elastic wave packet entering the optical beam. The second term corresponds to the elastic wave packet advancement in the optical beam aperture, and the third one keeps with the elastic wave packet leaving the aperture of the optical beam. The corresponding equations for calculating the pulse at the device output are obtained. The numerical calculations have proved the provisions and patterns established. The numerical modeling results were tested experimentally using a prototype of an acousto-optic processor with direct detection. The analysed results of theoretical and experimental studies unequivocally confirmed that the obtained formulas, formulated statements, and established provisions can be used to expand the functionality of acousto-optic processors, both with direct detection and of heterodyne type. It is shown that with a significant decrease in the input pulse duration relative to the time during which the optical beam is intersected by the elastic wave packet, the latter is converted into a scanning line and can be used to measure the geometric and energy characteristics of the quasi-coherent light.

Download Full-text

Inducing Frictional Force to Enhance the Transient Response in Beams

Al-Nahrain Journal for Engineering Sciences ◽

10.29194/njes.22020088 ◽

2019 ◽

Vol 22 (2) ◽

pp. 88-93

Author(s):

Hamed Khanger Mina ◽

Waleed K. Al-Ashtrai

Keyword(s):

Numerical Analysis ◽

Transient Response ◽

Frictional Force ◽

Damping Ratio ◽

Experimental Results ◽

Damping Capacity ◽

Tightening Force ◽

Contact Areas ◽

Good Agreement ◽

Ansys Workbench

This paper studies the effect of contact areas on the transient response of mechanical structures. Precisely, it investigates replacing the ordinary beam of a structure by two beams of half the thickness, which are joined by bolts. The response of these beams is controlled by adjusting the tightening of the connecting bolts and hence changing the magnitude of the induced frictional force between the two beams which affect the beams damping capacity. A cantilever of two beams joined together by bolts has been investigated numerically and experimentally. The numerical analysis was performed using ANSYS-Workbench version 17.2. A good agreement between the numerical and experimental results has been obtained. In general, results showed that the two beams vibrate independently when the bolts were loosed and the structure stiffness is about 20 N/m and the damping ratio is about 0.008. With increasing the bolts tightening, the stiffness and the damping ratio of the structure were also increased till they reach their maximum values when the tightening force equals to 8330 N, where the structure now has stiffness equals to 88 N/m and the damping ratio is about 0.062. Beyond this force value, increasing the bolts tightening has no effect on stiffness of the structure while the damping ratio is decreased until it returned to 0.008 when the bolts tightening becomes immense and the beams behave as one beam of double thickness.

Download Full-text

Pulsed High-Voltage Sensor with Nanosecond Transient Response Rise Time

Measurement Techniques ◽

10.1007/s11018-018-1529-8 ◽

2018 ◽

Vol 61 (9) ◽

pp. 941-943

Author(s):

K. Yu. Sakharov ◽

M. Yu. Denisov ◽

V. L. Ugolev ◽

R. A. Rodin

Keyword(s):

Transient Response ◽

High Voltage ◽

Rise Time ◽

Voltage Sensor

Download Full-text

The Button Head Bullet Effects on the Incident Pulse of Split Hopkinson Press Bar

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.782.311 ◽

2015 ◽

Vol 782 ◽

pp. 311-315

Author(s):

Jia Qu ◽

Geng Chen ◽

Guang Ping Zou

Keyword(s):

Elastic Wave ◽

Wave Length ◽

Constant Strain Rate ◽

Peak Stress ◽

Wave Theory ◽

Pulse Shaper ◽

Lagrange Method ◽

Stress Increase ◽

Split Hopkinson ◽

Peak Value

In order to make the specimen deformed under a constant strain rate and the stress in the specimen kept homogeneous, the wave shaper technology was adopted to modify the incidence waves of the normal Split Hopkinson Press Bar. A method of changing the shape of the bullet was suggested to be applied on the SHPB. Bullets with different length and different curvature have been researched in this paper. And the effection of the button head bullet about incidence pulse was simulated with Lagrange method by ANSYS/LS-DYNA. It is shown in the results that changing the curvature of the bullet impact the rising edge of incidence waves, and the peak stress increase with the speed of the bullet increase, the peak stress and length of incidence waves increased with the length of the button head bullet, when the peak stress reached a certain strength, increasing the bullet length could make the stress peak value lasted longer. Due to the reason that the button head bullet was based on the elastic wave theory, the wave length and the max stress of the shaped wave would be controlled conveniently and avoid the shortcoming that the analogue specimens could not be recycled in the normal pulse shaper technology.

Download Full-text

Effect of chain scission on flow characteristics of wormlike micellar solutions past a confined microfluidic cylinder: a numerical analysis

Soft Matter ◽

10.1039/d0sm00407c ◽

2020 ◽

Vol 16 (22) ◽

pp. 5261-5272 ◽

Cited By ~ 1

Author(s):

Mohd Bilal Khan ◽

C. Sasmal

Keyword(s):

Numerical Analysis ◽

Elastic Wave ◽

Micellar Solution ◽

Flow Characteristics ◽

Chain Scission ◽

Critical Value ◽

Weissenberg Number ◽

Elastic Instability ◽

Micellar Solutions ◽

Wave Phenomena

Elastic instability and elastic wave phenomena can be seen for the flow of a wormlike micellar solution past a confined microfluidic cylinder once the Weissenberg number exceeds a critical value.

Download Full-text