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Laser
Laser: “light amplification by stimulated emission of radiation.
A laser is a device that emits light through a process of optical
amplification based on the stimulated emission of electromagnetic radiation.
The first laser was built in 1960 by Theodore H. Maiman at Hughes Research
Laboratories, based on theoretical work by Charles Hard Townes and Arthur
Leonard Schawlow. A laser differs from other sources of light in that it emits
light coherently. Spatial coherence allows a laser to be focused to a tight
spot, enabling applications such as laser cutting and lithography. Spatial
coherence also allows a laser beam to stay narrow over great distances
(collimation), enabling applications such as laser pointers.
Elements of laser production:
1. Pumping: is the energy source which supply the lasing medium with
energy. Three source of energy:
a. optical pumping.
b. electrical pumping .
c. chemical pumping.
2. Lasing medium: It is the material responsible to generate laser and
possess the ability of population inversion, may be solid, liquid or gases.
3. Resonator or optical cavity: Tube or cavity contain medium and two
parallel mirrors one in front the other.
Components of a typical Laser:
1.
2.
3.
5.
Medium.
Laser pumping energy.
Mirrors (3+4).
Laser beam.
The medium is a material with properties that allow it to amplify light by way of
stimulated emission. Light of a specific wavelength that passes through the medium
is amplified (increases in power). For the medium to amplify light, it needs to be
supplied with energy in a process called pumping. The energy is typically supplied
as an electric current or as light at a different wavelength. Pump light may be
provided by a flash lamp or by another laser.
Characters of Laser:
Lasers are distinguished from other light sources by”:
1. Their coherence. Spatial coherence is typically expressed through
the output being a narrow beam, which is diffraction-limited. Laser
beams can be focused to very tiny spots, achieving a very
high irradiance, or they can have very low divergence in order to
concentrate their power at a great distance.
2. Monochromatic light.
3. High intensity light.
4. Laser in area of Ultraviolet light, visible light, infrared light.
Continuous and pulsed laser:
A laser can be classified as operating in either continuous or pulsed
mode, depending on whether the power output is essentially continuous
over time or whether its output takes the form of pulses of light on one
or another time scale.
Classification of Laser:
First: According to the condition of active medium:
A. Gas lasers: Helium–neon laser (He, Ne), carbon dioxide
(CO ) lasers.
2
B. Liquid lasers:
As
examples,
organic
dye
and
Rhodamine.
C. Solid-state lasers : for example, the first working laser
was a ruby laser.
Second: According to the types of radiation:
A.Continuous laser.
B. Pulsed laser.
Third: According to the nature of activity:
A. Surgical laser.
B. Stimulating laser.
Fourth: According to the nature of pumping:
A. Electrical.
B. Light.
C. Chemical.
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• Properties of laser surgery
1. Short stay in hospital.
2. Rapid operation.
3. Painless.
4. Low blemish.
5. Less hemorrhage and good control of bleeding.
6. Less infection.
7. Ablation of deep lesion.
8. Laser intensity was regulated to performed coagulation,
vaporization and cutting.
Laser therapy is used in many procedures. It may be used to:
• shrink or destroy tumors, polyps, or precancerous growths
• relieve symptoms of cancer
• remove kidney stones
• remove part of the prostate
• repair a detached retina
• improve vision (“laser eye surgery”)
• Lasers can have a cauterizing (sealing) effect.
• They may be used to seal: nerve endings, to reduce pain after
surgery. Blood vessels, to help prevent blood loss. Lymph vessels,
to reduce swelling and limit spread of tumor cells.
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• Laser therapy can be utilized to:
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Reduce inflammation
Increase tendon and wound strength
Reduce pain
Increase lymphatic drainage
Improve healing time
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Relax tight muscles
Increase mobility
Reduce swelling
Reduce scarring
Speed bone repair
Indications of continuous and pulsed modes of operation:
1. Cosmetic surgery (to remove tattoos, scars, stretch marks, sunspots,
wrinkles, birthmarks)
2. Refractive eye surgery (to reshape the cornea in order to correct or
improve vision)
3. Dental procedures (such as endodontic/periodontic procedures,
tooth whitening, and oral surgery)
4. General surgery (such as tumor removal, cataract removal, breast
surgery, plastic surgery and most other surgical procedures)
CONTRAINDICATIONS
1. Pregnancy.
2. Patients with cancer.
3. Patients with pacemakers.
4. Directly looking into the light.
5. Growth plates in children.
6. Over cardiac region & Vagus nerve.
7. Over & around thyroid gland & endocrine glands.
8.Patients who have been pre-treated with one or more
photo- sensitizers.
9. Organ transplantation: There is a possibility that the
laser's positive effects on immune systems could
compromise the immune suppression, which is critical to
successful.