The researchers created 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, the researchers used the LED (QD), which is driven by the electric excitation to emit the light source of the adjacent diode. They can pass through the quantum confined Stark effect (Stark, effect) quantum dots from adjacent driving diode tunable emission wavelength.

The idea of the researchers is to generate entangled photon pairs for quantum computing applications, which can be easily integrated into the semiconductor chip and the photonic cavity.

In this paper, a method for generating an electrically triggered anti bunching light from an electrically tunable light source is presented. For this purpose, the researchers have designed 16 individually tunable diode structures on a single chip. The device is composed of a planar microcavity LED of 180 x 210 m, which contains a layer of indium arsenide (InAs) quantum dots, 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. P and N, respectively, from the top of the DBR and the bottom of the DBR doped, forming a diode structure suitable for electrical excitation.

The main idea of the researchers is to "use the light generated by the LED to excite the quantum dots of neighboring diodes". The LED operates in a forward bias, and the broadband light emission from the InAs wetting layer is guided by the Prague mirror 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 type doping region (red), intrinsic (transparent) and N doped regions (blue). The LED emission light source, which is strongly driven by the forward bias (left), is shown as a blue light beam to excite the quantum dots (right) in the adjacent elements. Quantum dots emitting anti bunching light (green).

Because the cavity mode of the planar micro cavity matches the emission wavelength of the adjacent quantum dots, the QD emission ratio of the optical components is increased. By changing the bias of the second diodes, the tuning wavelength can be shifted by the Stark effect shift, and 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 exciton fine structure splitting of the second diodes can be tuned as a function of the entire electric field, so that it can be used as a source of entangled photon pairs.

The light emitted from the first diode (1) wetting layer is absorbed by the wetting layer of the adjacent diode, and the charge carrier is generated by the diode, and the quantum light source is emitted through the quantum dot. The wetting layer emission (left) and the quantum dot emission (right) are the actual data, while the wetting layer is shown as a copy of the emission data, and only for the operation of the display element

In the future, the researchers hope to improve the efficiency of the components, and to give more directional emission between different diodes. It is possible to use a unidirectional antenna or LED waveguide to improve the efficiency of cross coupling. In principle, a drive 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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