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Novel light sources using exciton-polariton condensates
Light, as we are familiar from everyday experience, can have very different properties depending on how it is created. For example, sunlight has a different distribution of wavelengths to artificial light, such as from fluorescent or LED lighting. Laser light, is also special in that it is monochromatic, i.e. it has only one wavelength in its output. Even monochromatic light such as lasers can have different states depending on how it is created. Light that comes from lasers are very close to an ideal sine wave. For this reason, laser light is thought to be “classical” in the sense that no peculiar quantum mechanical features such as entanglement are present.
However, it is known that there are special states of light that are completely “quantum” in their nature. In the field of quantum optics, the state of light is characterized by the Wigner function. If the Wigner function is positive everywhere, it is called “classical” light. If the Wigner function has any region that is negative, it has quantum properties, or more precisely, it is called non-Gaussian. The figure below has a plot of the light that is produced from the proposed device. It can be seen that there is a negative region to the Wigner function, which signals its quantum nature.
The light is produced in a semiconductor structure as shown in the below figure. The structure shown, called a microcavity quantum well, allows for particles called “exciton-polaritons” to be excited within the regions marked as red. When a sufficient number of the exciton-polaritons are created, a phenomenon called Bose-Einstein condensation can be made to occur. In Bose-Einstein condensation, the particles spontaneously form coherence, which means that their underlying wavefunction all become phase coherent. Once the exciton-polaritons become phase coherent, they leave the semiconductor by emanating through the top of the structure.
The light that escapes from the structure has a peculiar nature: they are all phase coherent because due to the Bose-Einstein condensation, but they simultaneously repel each other, because of the interactions between the exciton-polaritons. This is quite different to laser light, which are completely non-interacting, so that the photons do not feel each other’s presence. This makes for very different light characteristics between the new device and a standard laser.
Previous methods of producing such non-classical light relied on probabilistic methods: they would only work part of the time, and fail with some probability. In this invention, the light emerges continuously, just as in a laser where it is switched on and light emerges. This should help future quantum technologies, which rely on the use of such non-classical light.
1) Tim Byrnes, Yoshihisa Yamamoto, Peter van Loock, “Unconditional generation of bright coherent non-Gaussian light from exciton-polariton condensates“, Physical Review B 87 201301(R) May 2013
- Prof. Tim Byrnes Sharing His Idea on Quanta Magazine July 26, 2018
- Professor Byrnes on Money Morning May 14, 2018
- USTC-LSU-Calgary-NYU Collaboration April 22, 2018
- Our work featured in ScienceDaily April 8, 2018
- Professor Byrnes Was Interviewed by Xinhua News March 26, 2018
- Our work featured in Kaleidoscope March 9, 2018
- Our work featured in Physics February 19, 2018
- APS TV interviewed Tim February 15, 2018
- Generalized Grover algorithm paper in PRL February 15, 2018
- Chandra and Ebube win BOCO Global Scholar January 15, 2018
- Chandra wins prize in outstanding paper competition! December 22, 2017
- NYU Shanghai Gazette features our interview September 10, 2017
- News article in Financial Times August 18, 2017
- Another news article in Financial Times July 18, 2017
- NYU-ECNU Institute of Physics at NYU Shanghai featured in Physics World July 10, 2017
- News article in Financial Times China March 28, 2017
- News article in Sina Finance March 28, 2017
- News article in Valor Economico March 28, 2017
- News article in Financial Times about China as a tech superpower March 21, 2017
- Tim interviewed by Pudong TV for 1000 talents award July 26, 2016