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Content

• Introduction
• Uses
• Lasers in India
• LIDAR

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Introduction

A laser is a device that generates an intense beam of coherent monochromatic light (or other electromagnetic radiation) by stimulating of photons from excited atoms or molecules.

How does laser differ from normal light?

• Monochromatic: Same Wavelength/frequency (whereas normal light contains multiple wavelength)
• Coherent (ordinary light is not coherent): It means that all light waves are in phase with one another.
• Very narrow, highly directional and doesn’t diverge:
• The laser beam is extremely intense.

Uses: Lasers are used in

• Precision tools to cut through diamonds or thick metal.
• Laser surgery
• Skin treatment
• Optical disk drive
• Laser printers
• Barcode scanners
• Fiber optics
• Free space optical communication
• Drilling, cutting and welding materials
• Military and law enforcement devices
• Laser light display in entertainment
• Remote sensing

Lasers in India

• India currently has two lasers that produce 100 Terawatt (10 to the power 12) beams.
• The Raja Ramanna Centre for Advanced Technology in Indore is in the process of installing two petawatt systems, while another is likely to be installed in Hyderabad.

Nobel Prize in Physics, 2018 for LASER Physics Work

• Arthur Ashkin received the prize for the optical tweezers and their applications to biological system.
  • These optical tweezers are able to grab particles, atoms, viruses, and other livings cells with laser beam fingers.

• • These optical tweezers are widely used for isolating and examining very small particles, such as individual atoms, DNA strands, or biological cells.
  • This helped scientists understand the behavior of single atom or cells, instead of studying the average behavior of an aggregation of such particles.
  • The tweezers can capture living bacteria without harming them, a breakthrough he achieved back in 1987.
• Gerard Mourou and Donna Strickland were jointly awarded for their method of generating high-intensity, ultra-short optical pulses.

What was the problem earlier?

• Within a few years of the invention of laser, laboratory tabletop lasers had started achieving very high power of about a gigawatt. But after this state of peak power was reached, more intense pulses of power could not be produced without damaging the amplifying material.

How the problem was solved?

• The two scientists increased the duration of the pulses before the light was amplified so that the intensity comes down.
• The light could then be amplified normally.
• This amplified pulse could then be compressed back to its original time duration, and thus increasing its intensity by several order of magnitude.
• Their innovative technique, known as ‘chirped pulse amplification’ (CPA), has now become standard for high intensity lasers, including the ultra-sharp beam used in corrective eye surgeries. It allows to cut and drill very precisely in various matter.

How shorter high-intensity laser pulse can be beneficial?

A) LIDAR

• It stands for Light Detection and Ranging. It is a remote sensing method that uses light in the form of a pulsed laser to measure ranges (variable distance) to the Earth.
• These light pulses – combined with other data recorded by the airborne system – generate precise, three-dimensional information about the shape of the earth and its surface characteristics.
• LiDAR instrument principally consists of a laser, a scanner, and a specialized GPS receiver.

Two types of LIDAR are topographic and bathymetric.

• Topographic LIDAR typically uses a near-infrared laser to map the land, while
• Bathymetric Lidar uses water-penetrating green light to also measure seafloor and riverbed elevations.

Applications

• Used in projects related to roads, canals, surface transport, city planning, landslides, irrigation etc.
• The system can be brought to use for engineering designs, conservative planning, floodplain mapping, surface feature extraction (trees, shrubs, roads and building) and vegetation mapping (height and density).

Example Question

What is Chirped pulse amplification? Discuss its various applications. [10 marks, 200 words]