New Kind of On-Chip Single-Photon Extraction

Broadband enhancement of the on-chip single photon extraction via tilted hyperbolic metamaterials. A quantum emitter is positioned very close to a hyperbolic metamaterial, whose optical axis is tilted with respect to the end facet of nanofiber. (Source: L. Shen)

Quantum photonics involves a new type of technology that relies on photons. These photons can poten­tially carry quantum bits of infor­mation over large distances. If the photon source could be placed on a single chip and made to produce photons at a high rate, this could enable high-speed quantum communi­cation or infor­mation processing, which would be a major advance in infor­mation techno­logies. Now, a simple on-chip photon source using a type of a hyperbolic metamaterial is proposed. The inves­tigators from the Zhejiang University, Hangzhou, carried out calcu­lations to show that a prototype using the hyper­bolic meta­material arranged in a precise way can overcome problems of low effi­ciency and allow for high repetition rates for on-chip photon sources.

Until recently, single-photon sources have usually been made from self-as­sembled quantum dots in semi­conductors or from materials, like diamonds, with structural defects. It is difficult, however, to produce single photons at high rates from such materials. Some approaches to remedy this problem have been tried, but so far, the results suffer from a narrow bandwidth and low effi­ciency. Another way to approach these problems is to use special materials, such as meta­materials, for the photon source. Meta­materials are stacks of metallic and dielec­tric layers, structured at a level much smaller than the wavelength of light in use. They exhibit unusual optical pro­perties when formed into shapes, such as nanowires. Electrons flowing through the material set up a collective oscil­lation known as a surface plasmon, generating localized electro­magnetic fields.

Hyperbolic meta­materials are highly aniso­tropic versions of these meta­materials. They manipulate light in a variety of ways. For example, they can shrink the wavelength of light and allow it to travel freely in one direction while stopping it in another. The inves­tigators propose a geometry for their on-chip photon source where a hyperbolic meta­material is tilted at a precise angle with respect to the end facet of the nearby nano­fiber used to transmit the emitted photons. By choosing the tilt angle carefully, light reflections are suppressed at the interface with the fiber.

Calcu­lations by the group showed that this simple geometrical arrange­ment should overcome previous limi­tations with these materials. Researcher Lian Shen said, “Our work represents a vital step toward the imple­mentation of spectrally broad single photon sources with high repe­tition rates for on-chip quantum networks.” (Source: AIP)

Reference: L. Shen et al.: Broadband enhancement of on-chip single-photon extraction via tilted hyperbolic metamaterials, Appl. Phys. Rev. 7, 021403 (2020); DOI: 10.1063/1.5141275

Link: Interdisciplinary Center for Quantum Information, State Key Laboratory of Modern Optical Instrumentation, College of Information Science and Electronic Engineering, Zhejiang University, Hangzhou, China

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