The researchers built an electrically tunable quantum light source on a single chip

The University of Cambridge (Cambridge University) researchers in the recent "Applied Physics Letters" (Applied Physics Letters) in the journal published on "electrical driven and electrically tunable quantum light source" (Electrically driven and electrically tuneable quantum light sources) the results of the study show, two quantum dots in a single chip closely adjacent light emitting diode body (LED), can play a tunable electrical light source, quantum effect.

In this experiment, researchers used light sources emitted by electrically excited LED to excite adjacent diode quantum dots (QD). They can pass through the quantum confined Stark effect (Stark, effect) quantum dots from adjacent driving diode tunable emission wavelength.

The idea is to generate entangled photon pairs for quantum computing applications by means of a chip plane structure that is easily integrated into semiconductor devices and photonic cavities.

In this paper, the researchers demonstrated a method for generating electrically triggered anti bunching light from an electrically tunable light source. To this end, researchers have designed 16 tunable diode structures on a single chip. The element consists of 180 * 210 m planar microcavity LED, which consists of an indium arsenide (InAs) quantum dot layer embedded in a 10nm arsenide (GaAs) quantum well with a Al0.75Ga0.25As barrier layer.

In many distributed Prague reflector InAs quantum dot quantum well layer and the upper and lower growth (DBR), for the formation of half wavelength cavity, so as to increase the QD light source part of vertical launch, at the same time as the level of light from the waveguide layer emitting InAs wetting layer. The P and N are doped from the top DBR and the bottom DBR to form a diode structure suitable for electrical excitation.

The main idea of the researchers is to "use the light produced by LED to excite the quantum dots of adjacent diodes". The LED operates at a positive bias, and its broadband light emission from the InAs wetting layer is guided horizontally by the Prague reflector above and below the wetting layer. When a part of the light emitted at nearby LED, part of the light source is the wetting layer absorption, exciton by adjacent diode quantum dots capture, resulting in optical emission.

The element has a p doped region (red), an intrinsic region (transparent), and a n doped region (blue). A LED emitting light (represented by blue light) driven by a forward bias (left) strongly excited the quantum dots in the adjacent element (right). Quantum dots emit anti bunching light (green).

Since the cavity modes of the planar microcavity match the emission wavelengths of adjacent quantum dots, the QD emission ratio is increased to enter the collection optics. By changing the bias of the second diodes, the tunable wavelength can be shifted by the Stark effect, while the light intensity emitted by the adjacent diode can be controlled by changing the voltage of the first diode.

The researchers also confirmed that the fine structure splitting of the excitons in the second diodes can be tuned as a function of their entire electric field, allowing them to be used as the source of the entangled photon pairs.

Light emitted from the first diode (1) wetting layer is absorbed by the wetting layer of the adjacent diode, and a quantum light source is emitted after the diode generates a charge carrier and is retrieved by quantum dots. The wetting layer emission (left) and the quantum dot emission (right) are actual data, while the displayed wetting layer absorption is a copy of the emission data and is only used for the operation principle of the display element

In the future, the researchers hope to improve the efficiency of components and to give more emissive directivity between different diodes. It is possible to adopt unidirectional antennas or LED waveguides, thus improving cross coupling efficiency. In principle, a driving LED can excite many tunable LED. The combination of fast electronic components and low RC constant element, you can through the change of diode (1) bias to adjust the "pump", or through changing the diode (2) bias to adjust the wavelength, thus according to requirements issued entangled photons.

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