We show that the coupling efficiency of an optical system to a waveguide can be related to an apodized and normalized point spread function. Adapting the problem to the use of optical design software, we analyze and optimize systems that contain a fair amount of aberration. We compare theoretical predictions with experimental results and obtain good agreement.
Properties of P(VDF-TrFE) copolymer have been studied. A characterisation for thermal detection has been done on various copolymer samples with thicknesses ranging from 1 jim to 1 mm. A pyroelectric coefficient of 4 nC/cm2/°C has been measured on samples polarized by the corona discharge method. Optical, dielectric and thermal properties have also been measured. The possibility of polarizing the copolymer directly on an integrated circuit by corona thscharge has been demonstrated and a monolithic detector array of 32 elements has been realized Fabrication procedure, results of characterisation and performance of the detectors are presented.
The European Space Agency (ESA) X-Ray Mirror Modile (XMM) telescope is a set of three multiple shell grazing incidence Wolter Type I telescopes that will study astronomical x-ray sources from Earth orbit. There are a total of 58nested mirror shells within each telescope. Each shell consists of a paraboloid primary and hyperboloid secondary that together focus x-rays that are incident at grazing incidence onto a detector, known as the EPIC. Two ofthe telescopes also have grazing incidence diffraction gratings that disperse a portion ofthe focused x-rays across a second detector, known as the RFC.The complex geometry ofXMM makes stray light design and analysis ofthis telescope a unique and difficult challenge. The fundamental problem is that the detectors collecting the x-rays are also sensitive to visible and near-infrared radiation from outside sources such as the Sun and the Earth. This paper is an overview ofthe approach used to perform a stray light analysis ofthis visible radiation, and a presentation of four ofthe stray light problems that are unique to XMM and related grazing incidence telescopes. For each problem, a summary ofthe technique that was used to calculate the magnitude of the stray light is given.While the geometry ofthe XMM telescope is both unusual and complex, the approach for performing the stray light analysis was entirely standard. First, a computer model ofthe telescope was constructed with ASAP, a commercially available nonsequential ray trace program'. A profile ofthis model, including labeling ofthe major components is shown in Figure (1). Second, rays were traced backward from the detector to identify all objects that were visible from the detector. These are called "critical objects", because 1 00% of the stray light comes from these objects. If an object cannot be seen (either directly, or in reflection or refraction), then it cannot scatter light to the detector. Third, rays were traced forward through the XMM system to identify directly illuminated objects. Fourth, first order (single scatter) stray light paths were identified by objects that are both critical and illuminated, and second order paths were identified by finding ways that light could propagate from the directly illuminated objects to the critical objects. Finally, ASAP was used to make quantitative calculations of the amount of light scattered to the detector. Ray traces were performed in which rays incident on the XMM surfaces were split into scattered rays that propagated to the detector. The accumulated flux on the detector was then used to calculate the detector irradiance, expressed as a point source transmittance (PSI, defined as stray light irradiance at the detector divided by the source irradiance at the entrance to the telescope). In practice, the long and complex ray traces were performed over several months, and required many thousands of CPU hours on Pentium® class computers. SPIE Vol. 3113 • 0277-786X/971$lo.oo 321 Downloaded From: http://proceedings.spiedigitallibrary.org/ on 06/21/2016 Terms of Use: h...
This manuscript summarizes the work presented at the meeting. A more complete paper has already been submitted to a journal [1]. In effort to adapt the analysis of coupling lenses to the use of optical design software, we demonstrate that the coupling efficiency of a system can be related to an apodized and normalized point spread function.This approach allows the evaluation, optimization and tolerancing of systems which contain a fair amount of aberration. Comparison of theoretical predictions with experimental results shows good agreement. KEY WORDSLens coupling, design optimization, coupling efficiency. LENS DESIGN AND OVERLAP INTEGRALThe use of optical elements to affect laser-to-waveguide coupling is interesting since it provides beam magnification or mode matching. However, this raises the cost of the coupling system considerably; that is why it is important to be able to evaluate theoretical coupling performance. Since the numerical aperture of the beam emitted by a laser diode is usually in the range 0.4-0.6, the control of the coupling system's aberrations becomes critical. Our goal is to present a practical, engineering way to treat the problem that employs available lens design software and simple performance criteria such as the apodized point spread function and Strehl ratio.It is well established that the evaluation of the coupling efficiency (i) of a system is done using the overlap integral [2], 12
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