2 ms·

Pulsed THz radiation under ultrafast optical discharge of vacuum photodiode

2 points by westurner 2y ago

westurner 2y ago
"Pulsed THz radiation under ultrafast optical discharge of vacuum photodiode" (2024) https://link.springer.com/article/10.1007/s12200-024-00123-5 https://link.springer.com/article/10.1007/s12200-024-00123-5 : > Abstract: In this paper, we first present an experimental demonstration of terahertz radiation pulse generation with energy up to 5 pJ under the electron emission during ultrafast optical discharge of a vacuum photodiode. We use a femtosecond optical excitation of metallic copper photocathode for the generation of ultrashort electron bunch and up to 45 kV/cm external electric field for the photo-emitted electron acceleration. Measurements of terahertz pulses energy as a function of emitted charge density, incidence angle of optical radiation and applied electric field have been provided. Spectral and polarization characteristics of generated terahertz pulses have also been studied. The proposed semi-analytical model and simulations in COMSOL Multiphysics prove the experimental data and allow for the optimization of experimental conditions aimed at flexible control of radiation parameters. - "When ultrashort electron bunch accelerates and drastically stops, it can generate terahertz radiation" (2024) https://phys.org/news/2024-07-ultrashort-electron-bunch-drastically-generate.html https://phys.org/news/2024-07-ultrashort-electron-bunch-dras...
- westurner 2y ago
  Photocathode, > Photocathode materials doesn't list Cu (Copper) https://en.wikipedia.org/wiki/Photocathode https://en.wikipedia.org/wiki/Photocathode "Earth-abundant Cu-based metal oxide photocathodes for photoelectrochemical water splitting" (2020) https://pubs.rsc.org/en/content/articlelanding/2020/ee/d0ee02397c https://pubs.rsc.org/en/content/articlelanding/2020/ee/d0ee0... LightSlinger antennae are FTL within the dielectric, but the EMR is not FTL; from https://news.ycombinator.com/item?id=37342016 https://news.ycombinator.com/item?id=37342016 : > "Smaller, more versatile antenna could be a communications game-changer" (2022) https://news.ycombinator.com/item?id=37337628 https://news.ycombinator.com/item?id=37337628 : > LightSlingers use volume-distributed polarization currents, animated within a dielectric to faster-than-light [FTL] speeds, to emit electromagnetic waves. (By contrast, traditional antennas employ surface currents of subluminally moving massive particles on localized metallic elements such as dipoles.) Owing to the superluminal motion of the radiation source, LightSlingers are capable of “slinging” tightly focused wave packets with high precision toward a location of choice. This gives them potential advantages over phased arrays in secure communications such as 4G and 5G local networks
  - westurner 2y ago
    From https://news.ycombinator.com/item?id=39365579 https://news.ycombinator.com/item?id=39365579 : > "Coherent interaction of a-few-electron quantum dot with a terahertz optical resonator" (2023) https://arxiv.org/abs/2204.10522 https://arxiv.org/abs/2204.10522 ; "Researchers solve a foundational problem in transmitting quantum information" (2024) [w/ AlGaAs/GaAs] Though the [qubit wave function transmission range] on that is only tens to a hundred micrometers. With 5pJ microwave like OT, what is the range?
    - westurner 2y ago
      Ancient lingams had Copper (Cu) and Gold (Au), and crystal FWIU. From "Can you pump water without any electricity?" https://news.ycombinator.com/item?id=40619745 https://news.ycombinator.com/item?id=40619745 : > - /? praveen mohan lingam: https://www.youtube.com/results?search_query=praveen+mohan+lingam https://www.youtube.com/results?search_query=praveen+mohan+l...
    - westurner 2y ago
      - "High-sensitivity terahertz detection by 2D plasmons in transistors" (2024) https://news.ycombinator.com/item?id=38800406 https://news.ycombinator.com/item?id=38800406

2 points by westurner 2y ago

"Pulsed THz radiation under ultrafast optical discharge of vacuum photodiode" (2024) https://link.springer.com/article/10.1007/s12200-024-00123-5 https://link.springer.com/article/10.1007/s12200-024-00123-5 : > Abstract: In this paper, we first present an experimental demonstration of terahertz radiation pulse generation with energy up to 5 pJ under the electron emission during ultrafast optical discharge of a vacuum photodiode. We use a femtosecond optical excitation of metallic copper photocathode for the generation of ultrashort electron bunch and up to 45 kV/cm external electric field for the photo-emitted electron acceleration. Measurements of terahertz pulses energy as a function of emitted charge density, incidence angle of optical radiation and applied electric field have been provided. Spectral and polarization characteristics of generated terahertz pulses have also been studied. The proposed semi-analytical model and simulations in COMSOL Multiphysics prove the experimental data and allow for the optimization of experimental conditions aimed at flexible control of radiation parameters. - "When ultrashort electron bunch accelerates and drastically stops, it can generate terahertz radiation" (2024) https://phys.org/news/2024-07-ultrashort-electron-bunch-drastically-generate.html https://phys.org/news/2024-07-ultrashort-electron-bunch-dras...

westurner 2y ago
Photocathode, > Photocathode materials doesn't list Cu (Copper) https://en.wikipedia.org/wiki/Photocathode https://en.wikipedia.org/wiki/Photocathode "Earth-abundant Cu-based metal oxide photocathodes for photoelectrochemical water splitting" (2020) https://pubs.rsc.org/en/content/articlelanding/2020/ee/d0ee02397c https://pubs.rsc.org/en/content/articlelanding/2020/ee/d0ee0... LightSlinger antennae are FTL within the dielectric, but the EMR is not FTL; from https://news.ycombinator.com/item?id=37342016 https://news.ycombinator.com/item?id=37342016 : > "Smaller, more versatile antenna could be a communications game-changer" (2022) https://news.ycombinator.com/item?id=37337628 https://news.ycombinator.com/item?id=37337628 : > LightSlingers use volume-distributed polarization currents, animated within a dielectric to faster-than-light [FTL] speeds, to emit electromagnetic waves. (By contrast, traditional antennas employ surface currents of subluminally moving massive particles on localized metallic elements such as dipoles.) Owing to the superluminal motion of the radiation source, LightSlingers are capable of “slinging” tightly focused wave packets with high precision toward a location of choice. This gives them potential advantages over phased arrays in secure communications such as 4G and 5G local networks
- westurner 2y ago
  From https://news.ycombinator.com/item?id=39365579 https://news.ycombinator.com/item?id=39365579 : > "Coherent interaction of a-few-electron quantum dot with a terahertz optical resonator" (2023) https://arxiv.org/abs/2204.10522 https://arxiv.org/abs/2204.10522 ; "Researchers solve a foundational problem in transmitting quantum information" (2024) [w/ AlGaAs/GaAs] Though the [qubit wave function transmission range] on that is only tens to a hundred micrometers. With 5pJ microwave like OT, what is the range?
  - westurner 2y ago
    Ancient lingams had Copper (Cu) and Gold (Au), and crystal FWIU. From "Can you pump water without any electricity?" https://news.ycombinator.com/item?id=40619745 https://news.ycombinator.com/item?id=40619745 : > - /? praveen mohan lingam: https://www.youtube.com/results?search_query=praveen+mohan+lingam https://www.youtube.com/results?search_query=praveen+mohan+l...
  - westurner 2y ago
    - "High-sensitivity terahertz detection by 2D plasmons in transistors" (2024) https://news.ycombinator.com/item?id=38800406 https://news.ycombinator.com/item?id=38800406