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Quiz

Useful formulas:
    l (mm) = 1.24 / E(eV)
   als see the Math page.

  1. Direct band gap AlGaAs is an efficient light emitter.  Calculate the wavelength range of light that can be emitted by an AlGaAs layer. [Hint: calculate the range of  energy bandgap for the  direct gap and convert to the wavelength using the formula above.]
  2. For the short distance, local area network (LAN), AlGaAs is used as the active light emitting layer in a Laser diode.  Find the AlGaAs active layer composition for the wavelength l = 0.85 mm.  Do the same for l = 0.92 mm.
  3. Due to the low absorption coefficient in the optical fiber glass, wavelengths l = 1.3 mm and l=1.55 mm are used for long distance communication, or wide area network (WAN).  Find the  energy bandgap corresponding to these wavelengths.  Can the AlGaAs material be used as the light source for these wavelengths ?  Why or why not ? [Note: GaInAsP is the active layer for these wavelengths.]