Optoelectronics

  • Emitters : measure the characteristics of LEDs of different colors: spectroscopic study, emission wavelength, spectral width, comparison with a laser diode. Use of a red-green-blue LED to create different hues up to "white": principle of additive color mixing.
  • Receivers : study of different photoreceivers (photodiode, phototransistor, photoresistor, photomultiplier, etc.): sensitivity, quantum efficiency, linearity range, response time, spectral response, spatial resolution (CCD), etc. Study of photovoltaic energy conversion (solar cell): suitable load, optimum efficiency.
  • Optocouplers : study of characteristics, application as a motion sensor.
  • Light guides.
  • Observation, at the wavelength of a He-Ne laser, of the transverse electric (TE) and transverse magnetic (TM) propagation modes of a planar index-gap optical waveguide. The modes are excited by coupling with a total reflection prism.
  • Measure the mode propagation constants of a graded-index optical waveguide using a goniometer, and obtain the waveguide's index profile using the inverse WKB method.
  • Optical fibers.
  • Coupling laser sources (He-Ne, diode) with multimode and singlemode optical fibers: use of microscope objective or graded-index lens. Manipulate and estimate coupling rates.
  • Observation of the spatial distribution of propagated modes in a weak multimode fiber. Particular attention is paid to the emitting laser diode and the causes ofattenuation of transmitted light power (coupling, connection and propagation losses, etc.). Fiber length and refractive index are determined using a backscattering method.
  • Optical telecommunication: A He-Ne laser beam is amplitude-modulated by means of an acousto-optic modulator placed at the Bragg angle and driven by an audio signal (output from an amplified cassette player). The modulated beam is injected into an optical fiber, transmitted, detected and played back on a remote loudspeaker. Variant: electro-optical modulation using the Kerr and Pockels effect (study of polarization, characterization of electro-optical coefficients, non-linear effects, signal distortions) or use of a laser diode modulated directly by an electrical signal.
  • Interferometric pressure and temperature sensor using single-mode optical fibers: creation of a 2-wave interferometer using a directional optical fiber coupler, observation of interference rings after recombination and effect induced by the application of a pressure or temperature variation on one of the fibers.
  • CD recording: visualizing the grating and estimating the size of a pixel on a CD using laser beam diffraction. CD/DVD comparison.
  • Visualization of the digital signal sent by an infrared remote control: signal reception by a photodiode, recording on PC.
Published on March 13, 2017
Updated on March 13, 2017