Optical Sources : Laser Basics MCQ

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• Considering the values given below, calculate the mode separation in terms of free space wavelength for a laser. (Frequency separation = 2GHz, Wavelength = 0.5 μm)
  ক

  1.4×10-11

  খ

  1.6×10-12

  গ

  1×10-12

  ঘ

  6×10-11
• Longitudinal modes contribute only a single spot of light to the laser output.
  ক

  True

  খ

  False
• An injection laser has active cavity losses of 25 cm-1 and the reflectivity of each laser facet is 30%. Determine the laser gain coefficient for the cavity it has a length of 500μm.
  ক

  46 cm-1

  খ

  51 cm-1

  গ

  50 cm-1

  ঘ

  49.07 cm-1
• Doppler broadening is a homogeneous broadening mechanism.
  ক

  True

  খ

  False
• A semiconductor laser crystal of length 5 cm, refractive index 1.8 is used as an optical source. Determine the frequency separation of the modes.
  ক

  2.8 GHz

  খ

  1.2 GHz

  গ

  1.6 GHz

  ঘ

  2 GHz
• A ruby laser has a crystal of length 3 cm with a refractive index of 1.60, wavelength 0.43 μm. Determine the number of longitudinal modes.
  ক

  1×102

  খ

  3×106

  গ

  2.9×105

  ঘ

  2.2×105
• __________________ in the laser occurs when photon colliding with an excited atom causes the stimulated emission of a second photon.
  ক

  Light amplification

  খ

  Attenuation

  গ

  Dispersion

  ঘ

  Population inversion
• The lower energy level contains more atoms than upper level under the conditions of ________________
  ক

  Isothermal packaging

  খ

  Population inversion

  গ

  Thermal equilibrium

  ঘ

  Pumping
• An incandescent lamp is operating at a temperature of 1000K at an operating frequency of 5.2×1014 Hz. Calculate the ratio of stimulated emission rate to spontaneous emission rate.
  ক

  3×10-13

  খ

  1.47×10-11

  গ

  2×10-12

  ঘ

  1.5×10-13
• Which process gives the laser its special properties as an optical source?
  ক

  Dispersion

  খ

  Stimulated absorption

  গ

  Spontaneous emission

  ঘ

  Stimulated emission
• The radiation emission process (emission of a proton at frequency) can occur in __________ ways.
  ক

  Two

  খ

  Three

  গ

  Four

  ঘ

  One
• How many types of sources of optical light are available?
  ক

  One

  খ

  Two

  গ

  Three

  ঘ

  Four
• A device which converts electrical energy in the form of a current into optical energy is called as ___________
  ক

  Optical source

  খ

  Optical coupler

  গ

  Optical isolator

  ঘ

  Circulator