186
8 Terahertz Spintronics
Fig. 8.1 The electromagnetic spectrum. The THz frequency range lies between ‘radar’ and ‘people’
and is indicated in blue. Diagram from the LBL Advanced Light Source website (https://www.lbl.
gov/MicroWorlds/ALSTool/EMSpec/EMSpec2.html)
Time Period (T = 1/ ν): 1 picosecond.
Wavelength (λ = c/ν): 300 micrometre [Where, c is the velocity of light].
Photon energy (E = h ν): 4.14 meV [h is the Plank’s constant].
Temperature (T = h ν /K B ): 48 K [K B is Boltzmann’s constant].
Due to unavailability of efficient and reliable terahertz source and detector, this
portion of E–M spectrum remains underutilized that leads to so-called THz Gap.
This gap exists between 0.3THz and 30THz and is being filled up very rapidly.
Photonics technologies are advancing from the high-frequency side, while microwave
technologies are moving from the low-frequency side.
8.3 Why Terahertz Radiation Is so Important?
Terahertz radiation is very important and significant from both scientific and application point of view. Many fundamental and exciting phenomena are observed
in physics, chemistry, material science and biology that occur in picoseconds
scales. Some examples of scientific phenomena observed in picosecond scale (THz
frequency range) are given below.
• Spin–orbit interaction of electron.
• Rotation of some small molecules.
• Vibration of biologically significant collective modes of proteins.
• Existence of characteristic absorption spectra of many organic substances.
• Absorption by bimolecular water or hydration water.
• In semiconductors, resonance of electrons and their nanostructures.
8 Terahertz Spintronics
Fig. 8.1 The electromagnetic spectrum. The THz frequency range lies between ‘radar’ and ‘people’
and is indicated in blue. Diagram from the LBL Advanced Light Source website (https://www.lbl.
gov/MicroWorlds/ALSTool/EMSpec/EMSpec2.html)
Time Period (T = 1/ ν): 1 picosecond.
Wavelength (λ = c/ν): 300 micrometre [Where, c is the velocity of light].
Photon energy (E = h ν): 4.14 meV [h is the Plank’s constant].
Temperature (T = h ν /K B ): 48 K [K B is Boltzmann’s constant].
Due to unavailability of efficient and reliable terahertz source and detector, this
portion of E–M spectrum remains underutilized that leads to so-called THz Gap.
This gap exists between 0.3THz and 30THz and is being filled up very rapidly.
Photonics technologies are advancing from the high-frequency side, while microwave
technologies are moving from the low-frequency side.
8.3 Why Terahertz Radiation Is so Important?
Terahertz radiation is very important and significant from both scientific and application point of view. Many fundamental and exciting phenomena are observed
in physics, chemistry, material science and biology that occur in picoseconds
scales. Some examples of scientific phenomena observed in picosecond scale (THz
frequency range) are given below.
• Spin–orbit interaction of electron.
• Rotation of some small molecules.
• Vibration of biologically significant collective modes of proteins.
• Existence of characteristic absorption spectra of many organic substances.
• Absorption by bimolecular water or hydration water.
• In semiconductors, resonance of electrons and their nanostructures.