Helium Laser Lab Report

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4. Basic operation of the Helium-Neon Laser.
4.1. How to Make Helium-Neon Laser. The goal of this experiment is to know how to make a simple Helium & Neon LASER So we will need to three principal elements to make a laser :-
(1) Energy pump.
(2) Optical gain medium.
(3) Optical resonator.
Now we must know the role of every element in this experiment

Energy pump: A 1400-V DC power supply maintains a glow discharge or plasma in a glass tube containing an optimal mixture (typically 5:1 to 7:1) of helium and neon gas, the discharge current is limited to about 5 mA by a 91-kΩ ballast resistor. Energetic electrons accelerating from the cathode to the anode collide with Helium and Neon atoms in the laser tube, producing a large number of neutral Helium
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Even if the laser power is low it can be hazardous to the person 's eyesight, Moderate and high-power lasers also can be hazardous because they can burn the retina of the eye and cause permanent damage in seconds. Lasers can also cause damage in biological tissues, both to the eye and to the skin.

5.1. Laser radiation hazards
Thermal effects laser radiation injury, but photo-chemical effects can also be of concern for specific wavelengths of laser radiation. Some lasers are so powerful that can hazardous the eye.
The coherence and low divergence angle of laser light, aided by focusing from the lens, can cause laser radiation to be concentrated into an extremely small spot on the retina. Powerful lasers in the visible to near infrared range (400 to 1400 nm) will penetrate the eyeball and may cause heating of the retina; whereas exposure to the radiation with wavelengths is less than 400nm and greater than 1400nm are largely absorbed by the cornea and lens.
Infrared lasers are particularly hazardous, since the body 's protective glare aversion response, also referred to as the "blink reflex," is triggered only by visible light.

5.2. Maximum permissible
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