Spectroscopy

  • Realization and study of a slit spectroscope model (prism or grating), projected on a screen: dispersion (calibration using a spectral lamp whose emission lines are assumed to be known), resolution (geometric limitation, influence of diffraction), special case of the grating (free spectral zone of overlapping orders, Blaze effect). Comparison of prism and grating properties.
  • Use a prism or grating goniometer to measure the wavelengths of spectral lamp lines.
  • Set up a grating spectroscope with projection onto the Caliens CCD array. Intensity spectrum visualization on oscilloscope, recording and wavelength calibration on PC.
  • Use of the Jobin Yvon motorized monochromator: principle, choice of grating (600 lines/mm or 1200 lines/mm), measurement of resolution in nm/mm of slit using PC recording via photomultiplier and acquisition card (recording of the intensity profile of an emission line from a laser or spectral lamp, for different slit widths), monochromator fitting function (white light).
  • Use of a miniature professional CCD spectrometer (Oceanoptics) with fiber optics, equipped with an integrated CCD array and spectroscopy software: characterization of instrument performance (precision and accuracy), detectivity (signal/noise), measurement of resolution for different fiber optic sizes, visualization of the 2nd-order spectrum.
  • Use of the Ulice CCD spectrometer: same principle as above, but this larger spectrometer can be opened to explain its operation. The software normalizes the measured spectrum with a reference spectrum containing the response of the device (fiber, grating, CCD). A spectrum display in "color" mode associates a color with each wavelength. The "absorption" module comprises a white source and a cell holder in a closed housing to which the fiber is attached. This makes it very easy to carry out absorption measurements while eliminating stray light.
  • Applications : Use one of the above setups to study emission spectra (spectral lamp, incandescent lamp emission as a function of filament temperature, fluorescent tube, compact fluorescent lamp, LED, fluorescein, computer screen phosphors, etc.) or absorption spectra (colored glass, interference filter, ZnTe semiconductor sample, fluorescein, KMnO4, etc.). The screen projection set-up has the advantage of being highly demonstrative, and enables colors to be visualized. Projection on the Caliens CCD array shows how the commercial spectrometer Ocean Optics or Ulice works. The latter enables rapid, high-resolution recording of an intensity spectrum, with normalization by a reference spectrum if required. This can also be achieved, albeit less rapidly, with the motorized monochromator.
  • Photometric characterization of a photodetector: using a white source, interference filters and a calibrated power meter, we study the spectral response of a photodetector (photodiode, photomultiplier, CCD, etc.).
  • Photometric characterization of a spectrometer: the spectral response of a spectrometer is determined by recording the emission spectrum of a calibrated white lamp. Production of a secondary standard.
  • Application to the determination of their colorimetric indices and principles of color characterization and reproduction. Link between color and spectrum: record the spectrum emitted by a light source (fluorescent tube, computer screen) and convolve it with the eye's response. Determination of colorimetric coordinates and comparison with a filtered white spectrum. Application to the prediction of the apparent color of bodies as a function of the characteristics of the lighting used.
  • Interferential spectroscopy. Michelson interferometer in air gap configuration.
    1. Screen projection (measurements: wavelength of a spectral lamp emission line, Na doublet deviation, estimation of spectral lamp line widths, bandwidth of an interference filter or colored glass).
    2. Interferogram recording: using a motorized Michelson, a photomultiplier connected to a computer interface and data processing software for Fourier transform calculations. Various simulation programs are used to understand the influence of the various parameters associated with the equipment and the choice of measurement zones. To put it simply, a CCD array is equipped with a computer interface and data processing software(Caliens), enabling the signal received by the array's central pixel to be recorded over time and analyzed (by FFT) to deduce the source's spectral distribution.
  • Comparison of Michelson and Fabry-Pérot interference spectrometers: application to characterization of the mode spectrum of a multimode laser diode.
  • Single-mode fiber optic interferometric sensor: see optoelectronics, photoreceptors, optical fibers.
Published on March 13, 2017
Updated on March 13, 2017