LASER

Introduction

The term "laser" is an acronym for "Light Amplification by Stimulated Emission of Radiation". It is an intense beam of light which can be visible or invisible in case of ultraviolet and infrared radiation.

A laser device emits a beam of light through a process of optical amplification based on the stimulated emission of electromagnetic radiation. This device not only generates the beam of light, but also amplifies or increases the intensity of this beam of light.

Characteristics of Laser

1. Monochromatic: A laser consists of a single wavelength. As a result, the laser beam can be focused onto a smaller area for longer distances without compromising on the intensity of the laser beam.

2. Coherent: This means the wavelengths of the laser beam are in phase in space and time

3. Directionality or Collimation: Unlike ordinary light which spreads in all directions, leaser beams are highly directional and easy to focus without divergence.

4. Intensity: Due to the directionality of laser beams, their intensity is much higher than ordinary light.

Types of Lasers

Some of the common types of lasers are:

1. Gas Lasers

Different gases are used to coherently amplify the light beam. The Helium-Neon laser (HeNe) was the first to be invented. Other types of Gas lasers are CO₂ lasers, Argon-ion lasers, Nitrogen transverse electrical discharge in gas at atmospheric pressure (TEA) laser and many others. Different types of gas lasers are used for different purposes considering cost, intensity of light, coherence and so on.

2. Chemical Lasers

Laser beams are generated through chemical reactions which cause a large amount of energy to be released quickly. This type of laser has military applications

3. Solid-state Lasers

These lasers use a crystalline or glass rod which is "doped" with ions that provide the required energy states to generate the laser beam.

4. Fibre Lasers

Laser amplifiers where the light is guided in a single mode optical fibre are called fibre lasers.

Applications of Laser

Laser technology has found uses in many fields like:

1. Medicine

2. Communications

3. Industries

4. Science and Technology

5. Military

Laser Barcode scanners for Information Collection

A Barcode reader or Barcode scanner is an optical scanner that can read printed barcodes, decode the data contained in the barcode and send the data to a computer.

Figure 5: Barcode Scanner

Laser barcode scanners use a laser beam as the light source along with either a reciprocating mirror or a rotating prism to scan the laser beam back and forth across the barcode. A photo-diode is used to measure the intensity of the light reflected from the barcode. The light emitted by the reader rapidly varies in brightness depending on the data pattern and the photo-diode circuitry is designed to detect only signals with the same modulated pattern.

In shops and business establishments, laser barcode scanners use light to collect information about the prefixed prices of various products from the bar code printed on the product.

Advantages

1. Laser has high information carrying capacity. As a result, it is often used in the domain of communication for fast information transfer.

2. Laser is unaffected by electro-magnetic interference. This is beneficial in the field of optical wireless communication.

3. Lasers have minimal signal leakage, thereby maintaining information integrity.

4. Lasers are less damaging as compared to X-rays. They are, therefore, popular in the medical field.

5. The high intensity and low divergence properties of laser beams are weaponised by the military and defence field.

6. A laser beam can be focussed on areas smaller than 1 micro diameter. This is advantageous when storing large amounts of data.

Disadvantages

1. It is expensive to use and costly to maintain.

2. In some cases, it can burn on contact and is, therefore, harmful to humans.

3. Laser beams are delicate to handle and could cause damage if not focussed correctly. There is scope for human error.

Comparisons

Some differences between ordinary light like sunlight and laser beams like CO₂ lasers are specified in the table below:

Table 1: Comparison of Laser Beams and Ordinary Light

Ordinary Light	Laser Beams
Angular Spread is more	Angular Spread is less
Non- directional	Highly directional
Less intense	Highly intense
Not a coherent beam and not in phase	It is a coherent beam and is in phase
Radiations are polychromatic	Radiations are monochromatic

Conclusion

In conclusion, laser beams have myriad uses over many fields. It is important to understand the properties of various laser beams to apply them correctly and efficiently. However, laser beams can prove hazardous, therefore, care must be taken as incorrect usage of laser can cause great harm.