Quantum Optoelectronics 05/06/2019 – Posted in: Daily News

QUANTUM OPTOELECTRONICS

 

For: Preliminary

 

News Flash

Materials such as tungsten diselenide (WSe2) and molybdenum diselenide are being studied keenly for their opto-electronic properties – a combination of optics and electronics.

A key property of these materials is photoluminescence, in which the material absorbs light and re-emits it as a spectrum.

Researchers from IIT Madras have found a way of enhancing this property about 30 times in tungsten diselenide.

 

Two-dimensional material

  • Consisting of practically one layer of atoms, these materials are two-dimensional in structure.
  • Photoluminescence properties can be used in various devices such as quantum LEDs which can be used in communication and computation.
  • The most challenging aspect of this study was the controlled photoluminescence measurement of these materials from room temperature to 100 K.
  • Electrons in semiconductors occupy bands of energy known as valence bands.
  • As long as they live in these bands, they do not move and contribute to conduction.
  • If excited by a small energy input, they get kicked into what is called the conduction band where they can actually be delocalised and contribute to the conduction by moving around.

 

Excitons

  • When an electron jumps from the valence to the conduction band, it leaves behind a shadow called a “hole.”
  • The electron in the conduction band and the hole in the valence band can bind together and form a composite object (or pseudoparticle) known as an exciton.
  • There can be two ways in which an exciton can form – when the spins of the component electron and hole are opposite to each other and when they are aligned in teh same direction.
  • The former is called a bright exciton and the latter, a dark exciton.
  • Because their spins are opposite, the electron and hole forming the bright exciton can recombine, giving out a quantum of light in the process.

 

Source: The Hindu

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