Helium Neon Laser Video Lecture - Civil Engineering (CE)

let us see the construction of helium
neon laser a continuous and intense
laser beam can be produced with the help
of gas lasers a simplified diagram
showing basic features of a helium neon
gas laser is shown in the animation
helium neon laser system consists of a
quartz discharge tube containing helium
and neon in the ratio of 1 is to 4 at a
total pressure of about 1 millimeter of
mercury one end of the tube is fitted
with a perfectly reflecting mirror and
the other end with partially reflecting
mirror now carefully observe how a
helium neon laser works working of
helium neon laser a powerful radio
frequency generator is used to produce a
discharge in the gas so that the helium
atoms are excited to a higher energy
level the energy level diagram for
helium and neon atoms are shown in the
animation when an electric discharge
passes through the gas the electron in
the discharge tube collide with the
helium and neon atoms and excite them to
metastable states of energy twenty point
six one electron volts and twenty point
six six electron volts respectively
about the ground state some of the
excited helium atoms transfer the energy
to unexcited neon atoms by collision
thus the helium atom help in achieving a
population inversion in neon atoms when
an excited neon atom drops down
spontaneously from the metastable state
at twenty point six six electron volts
to lower
State at eighteen point seven zero
electron volts
it emits a 6-3 to 8 angstrom photon in
the visible region this photon traveling
through the mixture of the gas is
reflected back and forth by the
reflector ends until it stimulates an
excited neon atom and causes it to emit
a fresh 6 3 to 8 angstrom photon in
phase with the simulating photon this
stimulated transition from twenty point
six six electron volts level to eighteen
point seven zero electron volts level is
the laser transition the output
radiations escape from the partially
reflecting mirror the neon atoms drop
down from the eighteen point seven zero
electron volts level to know what a
state II through spontaneous emission
emitting in coherent light from this
level II the neon atoms are brought to
the ground state through collision with
the walls of the tube hence the final
transition is radiation less
you