Optical Source

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

• a) Optical source

• b) Optical coupler

• c) Optical isolator

• d) Circulator

The frequency of the absorbed or emitted radiation is related to difference in energy E between the higher energy state E2 and the lower energy state E1. State what h stands for in the given equation? E = E2 - E1 = hf

• a) Gravitation constant

• b) Planck’s constant

• c) Permittivity

• d) Attenuation constant

Which process gives the laser its special properties as an optical source?

• a) Dispersion

• b) Stimulated absorption

• c) Spontaneous emission

• d) Stimulated emission

_________________ in the laser occurs when photon colliding with an excited atom causes the stimulated emission of a second photon.

• a) Light amplification

• b) Attenuation

• c) Dispersion

• d) Population inversion

The recombination in indirect band-gap semiconductors is slow.

• a) True

• b) False

The absence of _______________ in LEDs limits the internal quantum efficiency.

• a) Proper semiconductor

• b) Adequate power supply

• c) Optical amplification through stimulated emission

• d) Optical amplification through spontaneous emission

The hole concentration in extrinsic materials is _________ electron concentration.

• a) much greater than

• b) lesser than

• c) equal to

• d) negligible difference with

Determine the total carrier recombination lifetime of a double heterojunction LED where the radioactive and nonradioactive recombination lifetime of minority carriers in active region are 70 ns and 100 ns respectively.

• a) 41.17 ns

• b) 35 ns

• c) 40 ns

• d) 37.5 ns

Determine the internal quantum efficiency generated within a device when it has a radiative recombination lifetime of 80 ns and total carrier recombination lifetime of 40 ns.

• a) 20 %

• b) 80 %

• c) 30 %

• d) 40 %

The Lambertian intensity distribution __________ the external power efficiency by some percent.

• a) Reduces

• b) Does not affects

• c) Increases

• d) Have a negligible effect