Types of laser

TYPES OF LASERSubmitted to: Submitted
by:
Mrs Yogendra Narayan Jyoti Singh
Research Scholar (EE Dept) ME (
Regular)
NITTTR, Chandigarh I & C 2nd Sem
Roll No: 142511

Types of Laser
(A) By active media
 Solid state laser - crystal, or glass, doped with
impurities, e.g. ruby laser, Ti:sapphire laser,
semiconductor laser.
 Gas laser - e.g. He-Ne laser, Ar+ laser, CO2 laser, N2
laser, HCN laser.
 Dye laser - active medium: dye molecules in liquid
solvent (sometimes in solids also).
(B) By mode of operation
 CW
 Pulsed
(C) By pumping and laser levels
 3-level laser
 4-level laser

Solid State Lasers: General
properties
 Solid state lasers use high density solid media
as active laser materials.
 Ions of transition elements, particularly rare
earth elements (Nd, Yb, Er, Ho etc.) or transition
metals (Cr, Ti etc.) are used most commonly as
dopants.
 Host materials include crystals like sapphire
(Al2O3), YLF (YLiF4), YAG (Y3Al5O12), LISAF
(LiSrAlF6), LICAF (LiCaAlF6), as well as glasses
from silicate (SiO2) and phosphate (P2O5)
classes.

Advantages
 No chance is of wasting material in the active
medium because here material used is in solid
form not in gas form, where this occurs.
 Both continuous and pulsed output is possible
from solid state lasers.
 Solid state lasers have high
 Construction is comparatively simple.
 Output power ranging from very low value of
about 0.04 watts to high value of about 600
watts.
 Cost of solid state lasers is economical.

Disadvantages
 Efficiency of solid state laser is very low as
compared to CO2 lasers.
 Great disadvantage of solid state lasers is the
divergence, which is not constant and ranges
1 milli radian to 20 milli radian.
 Output power is also not very high as in CO2
lasers.
 Due to thermal lasing in solid state lasers, the
power loss occurs when the rod gets too hot.

Applications / Uses of Solid state
Lasers
 Nd: YAG solid state lasers usually used when
drilling holes in metals.
 Nd: YAG pulsed type solid state lasers can be
used in medical applications such as in
endoscopy etc.
 As military application, Nd:YAG is used by
target destination system.

Ruby Laser
 Ruby laser is the first working laser
demonstrated by Ted Maiman.
 Host material is corundum (Al2O3) crystal,
dopants are Cr ions.
 Lasing Wavelength is 694 nm.
 Pumping is done with flash lamps and laser
operates in pulsed regime.

Construction & Working of Ruby
Laser

Advantages of Ruby Lasers
 From cost point of view, the ruby lasers are
economical.
 Beam diameter of the ruby laser is
comparatively less than CO2 gas lasers.
 Output power of Ruby laser is not as less as in
He-Ne gas lasers.
 Since the ruby is in solid form therefore there is
no chance of wasting material of active
medium.

Disadvantages of Ruby Laser
 In ruby lasers no significant stimulated
emission occurs, until at least half of the
ground state electrons have been excited to
the Meta stable state.
 Efficiency of ruby laser is comparatively low.
 Optical cavity of ruby laser is short as
compared to other lasers, which may be
considered a disadvantage.

Applications
 One of the first applications for the ruby laser
was in range finding.
 Due to low output power they are class-I lasers
and so may used as toys for children’s.
 It can be used as decoration piece & artistic
display.

Semiconductor Laser
 The semiconductor laser is very small in size
and appearance.
 It is similar to a transistor and has the
operation like LED but the output beam has
the characteristics of laser light.
 The material which often used in
semiconductor laser is the gallium Arsenide,
therefore semiconductor laser is sometimes
known as Gallium Arsenide Laser.
 It is also called Injection Laser.

Advantages of Semiconductor
Lasers
 Smaller size and appearance make them good
choice for many applications.
 From cost point of view the semiconductor
lasers are economical.
 Semiconductor lasers construction is very
simple.
 No need of mirrors is in semiconductor lasers.
 Semiconductor lasers have high efficiency.
 The low power consumption is also its great
advantage.

Disadvantages of Semiconductor
Lasers
 Semiconductor laser is greatly dependent on
temperature. The temperature affects greatly
the output of the laser.
 The lasing medium of semiconductor lasers is
too short and rectangular so the output beam
profile has an unusual shape.
 Beam divergence is much greater from 125 to
400 milli radians as compared to all other
lasers.
 The cooling system requirement in some
cases may be considered its disadvantage.

Application/Uses of Semiconductor
Lasers
 The semiconductor laser can be pulsed at
varying rate and pulse widths. Therefore this
laser is a natural transmitter of digital data.
 Semiconductor laser is well suited for interface
with fiber optic cables used in communication.

Gas Laser
 Gas lasers are widely available in almost all
power (milli watts to megawatts) and
wavelengths (UV-IR) and can be operated in
pulsed and continuous modes.
 Gas lasers use low density gaseous materials
as active media.
 Electrical pumping (continuous, RF or pulsed)
is used.
 The gas lasers can be made from neutral
atoms (He-Ne, metal vapor etc), ions (e.g. Ar+)
or molecules (e.g. CO2).

He-Ne Laser
 The He-Ne laser active medium consists of
two gases which do not interact form a
molecule. Therefore He-Ne laser is one type of
atomic gas lasers.
 The gain medium consists of a mixture of
helium and neon (10:1) inside of a small bore
capillary tube, usually excited by a DC
electrical discharge.

Advantages of He-Ne Laser
 He-Ne laser has very good coherence property.
 He-Ne laser can produce three wavelengths that
are 1.152µm, 3.391 µm and 632.8nm, in which
the 632.8nm is most common because it is visible
usually in red color.
 He-Ne laser tube has very small length
approximately from 10 to 100cm and best life time
of 20.000 hours.
 Cost of He-Ne laser is less from most of other
lasers.
 Construction of He-Ne laser is also not very
complex.
 He-Ne laser provide inherent safety due to low

Disadvantages of He-Ne
Laser
 It is relatively low power device means its output
power is low.
 He-Ne laser is low gain system/ device.
 To obtain single wavelength laser light, the other
two wavelengths of laser need suppression, which
is done by many techniques and devices. So it
requires extra technical skill and increases the
cast also.
 High voltage requirement can be considered its
disadvantage.
 Escaping of gas from laser plasma tube is also its
disadvantage.

Applications / Uses of He-Ne
Laser
 The Helium-Neon gas laser is one of the most
commonly used laser today because of the
following applications.
 He-Ne lasers are produced in large quantities
from many years.
 He-Ne lasers also used in super market checkout
counters to read bar codes and QR codes.
 The He-Ne lasers also used by newspapers for
reproducing transmitted photographs.
 He-Ne lasers can be use as an alignment tool.
 It is also used in Guns for targeting.

Ion Laser: Argon Ion Laser
 All ion lasers (such as argon, Krypton and mix
gas) produce several different wavelengths so
they are designed to produce these
wavelengths either simultaneously or
individually.
 Argon lasers are generally operated in
continuous wave mode.
 For argon lasers the output power can ranges
from few mill watts up to 20 watts.

Advantages of Argon Laser
 Production of multiple wave lengths is the
main advantage plus characteristic of argon as
well as other ion lasers.
 Argon lasers produce high power output as
compared to He-Ne laser.
 Argon laser is a higher gain system.
 Argon laser like He-Ne has very less
divergence, typically about 1 milli radian

Disadvantages of Argon laser
 The overall efficiency of argon laser is very
less usually lies between 0.01% and 0.1%.
 Large amount of power requirement is also its
disadvantage.
 Construction is very difficult.
 Cost of argon laser is not as low as He-Ne
laser.
 Power supply of high voltages required,
because due to solenoid there is extra burden
on it.

Applications of Argon Laser
 Argon lasers used in scientific research.
 Argon lasers used in medical application.
 An artistic displays and light shows also the
argon lasers are used.

Molecular Laser
 Unlike isolated atoms and ions in atomic and ionic
lasers, molecules have wide energy bands instead of
discrete energy levels.
 They have electronic, vibrational, and rotational
energy levels.
 Energy separation between electronic energy levels
lies in the UV and visible spectral ranges, while those
of vibrational–rotational (separations between two
rotational levels of the same vibrational level or a
rotational level of one vibrational level to a rotational
level from other lower vibrational level) levels, in the
NIR and far-IR regions.
 Therefore, most of the molecular lasers operate in the
NIR or far-IR regions.

Carbon Dioxide (CO2) Laser
 Therefore CO2 gas laser is considered the type of
molecular gas laser.
 Importantly note that CO2 lasers use carbon
dioxide as well as Helium & Nitrogen as its active
medium.
 The role of N2 is to facilitate the CO2 pumping &
population inversion process by providing
molecule collision with the CO2 gas.
 The role of He is to facilitate the removal of
decayed molecules from their lower energy level
to ground level after lasing process, in order to
maintain the population inversion.

 CO2 Gas Laser is a high power laser generating device .
 The laser light takes place within the molecules of carbon
dioxide
Construction and working of CO2 Gas
Laser

 The CO2 Gas Laser consist of mixture of gases like O2-N2,
He and
CO2.
Laser

Laser
 The CO2 Gas Laser consist of mixture of gases like O2-N2,
He and
CO2.

 Since heat is an undesired byproduct for lasing action in this
type of
lasers, so it always contains a heat exchange system to
remove the
Laser

 The CO2 Gas Laser consists a separate Gas supply system
and the
Blower motor.
Laser

 The Vacuum pump is used to maintain proper Torr level
within the
cavity in order to operate in the state of controlled vacuum.
Laser

 The CO2 Laser contains s series of mirrors in the optical
cavity.
 The Rear and Folding mirrors are 100% reflective whereas
Output
Laser

 The folding mirrors are used to lengthen the resonator beam
path to
increase gain/power without physically lengthening the entire
Laser

 The CO2 operates in continuous mode so a shutter devices is
used to
control the output from a CO2 Gas Laser.
Laser

 The CO2 Gas Laser consists of more than one anode for the
purpose of maintain even discharge between the anode and
cathode.
 By spreading the electrical discharge over a wide area a
Laser

Laser

Advantages of CO2 Laser
 In CO2 The CO2 laser offers the lowest cost
per watt along with good beam quality, The
high power levels are obtained ranges from
few watts to 15000 watts.
 The efficiency of CO2 gas lasers (i.e. 10% or
higher) is beat than He-Ne and argon lasers.
 Long sealed-off lifetime of greater than 20,000
hours.
 Small size per watt of output power.

Disadvantages of CO2 Laser
 Divergence of CO2 lasers approximately in all
cases is greater than He-Ne and Argon laser.
Usually the divergence is ranges from 1 to 10
milli radians.
 Beam width varies from 3mm to 100mm.
 Some CO2 lasers have the disadvantage of a
short and thick optical cavity.
 Cooling system requirement in some
configurations also a disadvantage.
 Its cost is comparatively high.

Application/Uses of CO2
Lasers
 The CO2 gas laser can be used in industry
usually for welding and cutting purposes.
 The CO2 laser acts as a surgical tool in the
operating room.
 In both energy and weapons research, there is
good field of application of CO2 lasers.
 Fractonal C02 Laser Skin Resurfacing

Dye Laser (A Liquid Laser)
 Liquid lasers are those lasers which uses
liquid as an active medium.
 In dye laser the liquid material called dye (for
example rhodamine B, sodium fluoresein and
rhodamie 6G) uses as an active medium,
which causes to produce laser light.
 The dye lasers produce output whose
wavelengths are in the visible, ultra violet and
near infrared spectrum.

Advantages of Dye Lasers
 It is available in visible form (also in non-visible)
 Range of wavelengths can be produced by the
using dye lasers.
 Beam diameter is very less.
 Its beam divergence (0.8 milli radians to 2 milli
radians) is also less from many lasers beam
divergence.
 Construction of dye laser is not so complex.
 Having the greater efficiency 25%.
 High output power is also possible with dye lasers

Disadvantages of Dye Lasers
 Cost of dye lasers is very high..
 To tune at one frequency, the laser uses
birefringent element or filter making it more
costly.
 In dye lasers it is very difficult to determine the
element that actually lases because dye has
complex chemical formula.

Application of Dye Lasers
 Dye lasers are mostly used as a research tool
in medical applications

CW and Pulsed Laser
 Laser Output as a function of time
 From design point of view we can say that
output of all lasers is not constant. Different
types of applications require different types of
lasers. Therefore the output from the laser can
be altered by changing its magnitude over a
period of time

Continuous Wave Laser
 A laser that are designed to produce a beam of constant
amplitude are called continuous wave or CW lasers. The CW
lasers are rated in power units of watts, milli & kilo watts.
 A graph of the power output from the laser as function of time
is shown as:
 Since Power = energy / time
or Energy = power X time
 Therefore the area below the line in graph represents the
energy transmitted by laser.

Pulsed Laser
 In normal pulsed laser, the excitation
mechanism is pulsed and the laser is
produced for short time while the pumping
energy is great enough to keep the active
medium above the gain threshold. By diagram
normal pulsed laser can be shown as:

Pulsed Laser
 Energy curve for normal pulse laser is as
The pulse width for normal
pulsed laser varies from 0.1 to
10 milli seconds.
PRT
 The PRT represent the time
for one complete ON-OFF
cycle. This is also referred to
as the period of the pulse
PRT = 1 / PRR

Types of laser

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