摘要:

An approximate form of the lucky drift expression for ionisation coefficients is presented. This simplified expression enables analytic calculation of the ionisation coefficients in staircase avalanche photodiode structures using some approximations. The ionisation coefficients in superlattice avalanche photodiodes are calculated in the same manner. The results for both these structures are compared with other theories and with experimental observations.

DOI:10.1049/ip-j.1987.0051

出版商:IEE    

年代:1987

数据来源: IET

摘要:

The paper presents an investigation of deformation in the active region of GaAs laser diodes under operating conditions. Since the properties of bulk material and manufactured diode are not identical, a study of the spectral splitting and polarisation changes caused by mechanical stress in the diode is made. These results are used to calibrate instruments for a study of the deformation due to thermal stress in the diode under operating conditions. This thermal stress can exceed the shear stress required for dislocation motion in the active region of the diode.

DOI:10.1049/ip-j.1987.0052

出版商:IEE    

年代:1987

数据来源: IET

摘要:

This paper describes the development of liquid crystal light valves (LCLVs) using bismuth silicon oxide (BSO) as the photoconductor at the Sowerby Research Centre of British Aerospace. The results of two LCLVs are presented and compared, both of which use a 250 micrometre thick slice of BSO. The variation in time response with liquid crystal viscosity is investigated. A resolution of 27 line pairs/mm (50% MTF point) was obtained for the first device. However, refinements in fabrication and measurement techniques yield a resolution of 31 line pairs/mm for the second light valve.

DOI:10.1049/ip-j.1987.0053

出版商:IEE    

年代:1987

数据来源: IET

摘要:

A silicon-clad planar diffused optical waveguide structure is proposed and propagation characteristics for a wavelength of 0.6328 μm are investigated. The refractive index profile of the substrate is assumed to be a Gaussian profile and a maximum index change of 0.01 is also assumed. Computer modelling studies indicate that silicon-clad diffused optical waveguides exhibit a damped periodic oscillation in the attenuation and mode index curves. The attenuations of these waveguide structures are relatively small compared with those of the four-layer planar homogeneous waveguide structures reported by Batchman and McWright. The attenuation may be reduced with a low-index buffer layer. Furthermore, the attenuation and mode index are significantly altered by the conductivity changes of silicon.

DOI:10.1049/ip-j.1987.0054

出版商:IEE    

年代:1987

数据来源: IET

摘要:

The paper illustrates the results of work carried out towards the development of a computer model for the front end of a 3-dimensional vision sensor based on the optical rangefinder principle. The resultant electro-optical model was found to offer two distinct advantages: first, it helps to design the drive circuit so as to operate the light source within its optimum region in terms of both light output and frequency response and, secondly, it enables the use of a model driven approach during the 3-dimensional data processing stage. This latter, in turn, helps to increase the confidence limit for each set of voxel (or ‘rangepic’) measurements for a given signal-to-noise ratio and, therefore, enables the use of low power light sources such as light emitting diodes in preference to higher power but more expensive laser diodes. The model was developed specifically for a 3-dimensional vision sensor based on the phase measurement rangefinder, but it can be adapted to other 3-dimensional vision sensors which employ light reflectance measurements using light source/detector combinations, such as scanning laser rangefinders.

DOI:10.1049/ip-j.1987.0055

出版商:IEE    

年代:1987

数据来源: IET

摘要:

A graphical method is described where-by the important steady state and dynamic responses of an optical bistable device can be viewed simultaneously. This results in a set of ‘operating curves’ which indicate how well an optical bistable device satisfies the requirements to perform a particular logic function. The operating curves may be used to find the optimum conditions to perform a function and they also show how resilient this point is in the presence of fluctuations in operating conditions.

DOI:10.1049/ip-j.1987.0056

出版商:IEE    

年代:1987

数据来源: IET

摘要:

Measurements are made of the interactions between microwaves and optical fibres. In particular, measurements have been made of the standing wave ratio and admittances which occur when fibres are located in waveguides. Techniques using open resonators have allowed measurement of the extinction widths of fibres when placed in a microwave field. The types of fibres tested are multimode, single-mode and fibres having a conducting secondary coating. These results are applied to the design and evaluation of a microwave power detector in waveguide, in which single-mode optical fibres (with a conducting secondary coating) form the essential elements. This device when operated at frequencies around 10 GHz has enabled microwave power levels down to 5 mW to be detected.

DOI:10.1049/ip-j.1987.0057

出版商:IEE    

年代:1987

数据来源: IET