WorksheetsIntroduction to LASER
Total questions: 15
Worksheet time: 8mins
Photons of
Spontaneous emission are coherent
Stimulated emission are not coherent
Stimulated emission are in phase with stimulating photons
Stimulated emission have no phase relationship
Spontaneous emission
is proportional to the number of atoms per unit volume of excited state
is proportional to the number of atoms per unit volume of ground state
takes place when pumping is done
results in photons of same phase
The rate of stimulated radiation
does not depend on the number of atoms in excited state
depends on number of atoms in ground state
is responsible for production of population inversion
depends on intensity of external radiation
The working of Laser is based on the principle of
induced absorption
spontaneous emission
ionization
stimulated emission
The lifetime of an atom in a metastable state is of the order of
10 -10 sec
10 -8 sec
10 -3 sec
None of these
Rate of induced absorption depends on
number of atoms in the lower energy state
the energy density of incident radiation
number of atoms in the higher energy state
both number of atoms in the lower energy state and the energy density of incident radiation
LASER is a short form of
Light Amplification by Spontaneous Emission Radiation
Light Amplification by Stimulated Emission of Radiation
Light Absorption by Stimulated Emission of Radiation
Light Absorption by Spontaneous Emission of Radiation
Example of solid state laser is
He-Ne Laser
CO2 Laser
Nd:YAG Laser
Dye Laser
What requirement needs to be met before a medium can begin to ‘laser’?
100% slope efficiency
threshold voltage
Population inversion
Equal density of states
Usually, population inversion in gas laser is achieved by
electric discharge
heating
optical pumping
direct conversion
A laser beam is monochromatic. It means it has
single frequency
narrow width
wide width
several colors
The material in which the population inversion is achieve is called as
Active medium
metastable state
passive medium
stable states
The method of achieving population inversion in Ruby Laser is
Optical pumping
inelastic Scattering
forward biasing
chemical reaction
Which scientist first came up with the idea of stimulated emission ?
Alexander Graham Bell
Isaac Newton
Arthur Schalow
Albert Einstein
Optical resonators
act as pumping mechanism
provided positive feedback and amplification
provide feedback only
Provide amplification only
