NMI TR 10.doc - NMI TR 10 A 650 nm Diode Laser-based...

This preview shows 1 out of 6 pages.

NMI TR 10 A 650 nm Diode Laser-based Integrating Sphere System for Absolute Radiometry Dr Philip B. Lukins First edition — August 2006 Bradfield Road, Lindfield, NSW 2070 PO Box 264, Lindfield, NSW 2070 Telephone: (61 2) 8467 3600 Facsimile: (61 2) 8467 3610 Web page:
Image of page 1

Subscribe to view the full document.

© Commonwealth of Australia 2006
Image of page 2
CONTENTS 1 Introduction ............................................................................................................ 1 2 The Integrating Sphere ........................................................................................... 1 3 Diode Laser System ............................................................................................... 4 4 Monitor Photodiode and Preamplifier .................................................................... 9 5 Data Acquisition System ...................................................................................... 10 6 Calibration of the Responsivity of the External Photodiode Detector ................. 11 7 Preliminary Experimental Results using this Laser-sphere System ..................... 11 8 Conclusions .......................................................................................................... 14 9 Acknowledgements .............................................................................................. 15 10 References ............................................................................................................ 15 iii
Image of page 3

Subscribe to view the full document.

iv
Image of page 4
1 INTRODUCTION Traditionally, radiometric sources have been based on lamps of various types or on blackbodies. This has certainly be so for diffuse sources and sources that have used diffusing devices such as integrating spheres or diffusing plates. However, more recently, there has been increasing interest in using lasers as components in diffuse sources. While there are many types of lasers with different optical characteristics (in the time, frequency, spatial and spatial frequency domains), it is continuous-wave single-frequency visible and near infrared lasers that would be of greatest interest in radiometry. In particular, the use of a CW single-frequency laser together with an integrating sphere should allow generation of optical beams that are highly temporally-coherent but have almost no spatial coherence. Such sources would have many applications including, for example, the simulation of blackbodies or molten- metal sources at a fixed wavelength, and in the calibration of photometric equipment at particular wavelengths. In the future, radiometric source standards based on other laser types and characteristics together with traditional passive devices, such as integrating spheres, will be developed. A major metrological application of such laser-sphere systems is likely to be in the development of thermodynamic temperature scales [1–4]. In this report, a 650 nm monochromatic diffuse source is described. This source serves both as a demonstration of the principles involved as well as acting as a source in two specific applications in the work of the temperature and radiometry groups, that is, in (a) absolute radiometry and in (b) radiation thermometry and thermodynamic temperature scales. 2 THE INTEGRATING SPHERE When a flux,  illuminates a diffusing surface of reflectance, r, over an illuminated area, A, the radiance, R, seen within a total projected solid angle, , is: R = r / A (1) Inside the sphere, the radiation undergoes multiple reflections so that the total flux incident over the entire sphere can be obtained by a power series expansion in r(1 – f), where f is the port fraction, which leads to the result that: R = [ / A ] { r / [ 1 – r (1 – f)]} (2) which implies that the sphere multiplier is: M = r / [ 1 – r (1 – f)] (3) Therefore, from a knowledge of the port fraction and the effective sphere reflectance, the sphere efficiency and output radiance can be calculated. If r = 0.98 and f = 0.015,
Image of page 5

Subscribe to view the full document.

Image of page 6
You've reached the end of this preview.
  • Spring '12
  • Islam
  • ........., Diode Laser System

{[ snackBarMessage ]}

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern