Types of Lasers

What is Laser?

LASER is an abbreviation of Light Amplification by Stimulated Emission of Radiation. Lasers are light beams so powerful that they can travel miles into the sky, and they can also cut through the surfaces of metals. Theodore H Maiman at Hughes Research Laboratories was the first person to build a practical laser in 1960. Today lasers find applications in various fields and there are different types of lasers with numerous applications.

List of Laser Types

Lasers are classified into 6 types based on the types of medium used in them, and they are:

• Solid-state lasers
• Gas lasers
• Liquid lasers
• Semiconductor lasers
• Chemical lasers
• Metal-vapour lasers

Solid-State Lasers

The solid-state laser is a type of laser where the medium used is solid. The solid material used in these lasers is either glass or crystalline materials.

Working of Solid-State Laser

Glass or crystalline materials used in a solid-state laser are used as impurities in the form of ions along with the host material. Doping is the term used for describing the process of addition of impurities to the substance.

The dopants that are used in this type of laser are terbium (Tb), erbium (Eu), and cerium (Ce) which are rare earth elements. The host materials are ytterbium-doped glass, neodymium-doped yttrium aluminium garnet, neodymium-doped glass and sapphire. The most commonly used host material is neodymium-doped yttrium aluminium garnet.

Application of Solid-State Laser

• The drilling of holes in the metals becomes easy with these lasers.
• The push-type solid-state lasers are used for medical purposes such as for endoscopy.
• They find application in the military and are used in the target destination system.

Advantages of Solid-State Lasers

• These lasers have casts that are economical.
• The construction of a solid-state laser is simple.
• The output can be both continuous and pulsed.
• There is very less or zero chance of material in active medium going waste.
• The efficiency of these lasers is high.

Disadvantages of Solid-State Lasers

• The output of solid-state lasers is not high.
• The divergence of this laser is not constant and varies between 1 milliradian to 20 milliradians.
• There is a power loss in the laser due to heating of the rod.

Gas Lasers

Gas lasers have an active medium made up of one or more gases or vapours. These lasers are classified as:

• Atomic gas lasers which is He-Ne laser
• Molecular gas lasers which is CO₂ laser
• Ion gas lasers that are Argon laser

Liquid Lasers

Liquid lasers are also known as dye lasers. This is a type of laser in which liquids are used as an active medium. The active material used in the liquid laser is known as a dye and the commonly used dyes are sodium fluorescein, rhodamine B and rhodamine 6G.

Working of Liquid Laser

The active medium in this laser type is organic dye and the solvent used for dissolving the dye is either water, alcohol, or ethylene glycol. The dye is pumped to the capillary tube from the storage tank. This dye leaves the tubes with a flash lamp. The output beam then passes through a Brewster window to the output coupler which is a 50% reflective mirror. The output wavelength can vary to a wide range and the maxim output possible is 618 nm.

Application of Liquid Laser

• These lasers are commonly used for medical purposes as a research tool.

Advantages of Liquid Lasers

• The efficiency is greater by 25%.
• The wavelengths that are produced can be of varied ranges.
• The diameter of the beam is less.
• The beam divergence ranges between 0.8 milliradians and 2 milliradians, which is comparatively lesser than other lasers.

Disadvantages of Liquid Lasers

• These lasers are expensive.
• Tuning a laser to one frequency requires the use of a filter which makes it more expensive than other laser types.
• It is difficult to determine which element is responsible for lases.

Semiconductor Lasers

The semiconductor laser is a type of laser that is small in appearance and size. The operation of this laser is similar to LED but the characteristics of the output beam are of laser light. The manufacturing of semiconductor used in semiconductor diode is done uniquely.

Working of Semiconductor Laser

The active material used in a semiconductor laser is gallium arsenide and therefore, the laser is also known as Gallium Arsenide Laser.

The working of a semiconductor laser is similar to the PN diode in forward biased condition. The PN material is connected to the DC power supply with the help of the metal contacts. The semiconductor laser is also known as the Injection Laser because the current is injected into the junction between P and N material.

Application of Semiconductor Lasers

• This laser is a transmitter of digital data naturally as the laser can be pulsed at different rates and pulse widths.
• These lasers find applications in optic cable communication.

Advantages of Semiconductor Lasers

• They find many applications due to their small size and appearance.
• These lasers are economical.
• There is no use of mirrors.
• The power consumption is low.

Disadvantages of Semiconductor Lasers

• The divergence of the beam is more than 125 to 400 milliradians which is greater than other laser types.
• The output beam has an unusual shape as the medium used is short and rectangular.
• The working of this laser type is dependent on the temperature.

Stay tuned to learn more about other concepts of Physics.