Micropillar Quantum Photon Source With Fine-Structure Splitting Control
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Solution Overview
Problem
Semiconductor quantum boxes used for generating single photons and entangled photon pairs face limitations due to fine structure splitting, which affects brightness and purity, and are sensitive to environmental disturbances, making it difficult to control and maintain indiscernibility of radiative emission paths.
Innovation Solution
A device with a quantum box inserted into a micro-pillar optical cavity featuring three electrical bonding pads around the top face, allowing for adjustable voltage sources to control fine structure splitting and optimize photon emission, including the use of two coupled optical cavities to achieve polarization-degenerate modes for enhanced photon generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If quantum boxes are used as sources of single photons or entangled photon pairs, then the generation of quantum states is achieved, but the brightness and bit rate are limited
Solution Approach 1:
The patent applies parameter changes by using strain fields and electrical fields to dynamically adjust the fine structure splitting of the quantum box. This allows optimization of the quantum box's emission properties to improve brightness and bit rate while maintaining quantum state quality. The strain fields modify the physical parameters of the quantum box structure, while electrical fields adjust the energy levels and transition rates.
2Productivity
If quantum boxes are enclosed in optical cavities to improve brightness and bit rate, then the spontaneous emission rate increases, but the sensitivity to environmental disturbances remains
Solution Approach 1:
The patent introduces strain fields and electrical fields as intermediary control mechanisms between the quantum box and its environment. These fields provide a controlled interface that allows adjustment of the quantum box properties without direct mechanical or thermal contact, thereby reducing sensitivity to environmental disturbances while maintaining enhanced spontaneous emission rate through optical cavity confinement.
3Reliability
If strain fields are applied to control fine structure splitting, then the entanglement is maintained, but the fabrication and alignment become complex
Solution Approach 1:
The patent employs dynamic control of fine structure splitting through adjustable strain fields and electrical fields. Instead of requiring precise static fabrication of the quantum box with predetermined properties, the system allows post-fabrication adjustment of the fine structure splitting by applying controlled strain and electrical fields. This dynamic approach simplifies fabrication by decoupling the manufacturing process from the precise tuning requirements.
4Adaptability or versatility
If electrical fields are used to adjust fine structure splitting, then the orientation and intensity can be controlled, but the device complexity increases
Solution Approach 1:
The patent implements multi-functionality by using electrical bonding pads and voltage sources that serve multiple purposes: they provide electrical contact for applying strain fields, generate electrical fields for direct fine structure splitting control, and enable both static and dynamic adjustment of quantum box properties. This universal approach reduces the need for separate dedicated components for each function.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration enables static or dynamic control of fine structure splitting, improving the brightness and purity of single photons and the generation of entangled photon pairs by minimizing energy deviations and maximizing the probability of single photon emission while reducing the likelihood of multiple photon emissions.
Implementation Method 1
The quantum boxes also allow a reliable interaction of the light with the characteristics of the confined charge carriers. An electron of the valency band of the quantum box can transit the conduction band to form, in association with the hole left in the valency band, an electron-hole pair, also called exciton. The exciton state corresponding to the formation of an exciton is an unstable state and the reestablishment of the neutral state, also called fundamental state, is done by the recombining of the electron with the hole with emission of a photon according to a spontaneous emission process
Implementation Method 2
In order to improve the performance levels of the quantum boxes in terms of brightness and bit rate, it is known practice to insert the quantum box in a resonant optical cavity. Such a configuration makes use of the Purcell effect, also known by the expression 'low light-material coupling system', to increase the spontaneous initial rate of the quantum box in the cavity mode and make it possible to more effectively collect the photons emitted by the quantum box
Implementation Method 3
A device with a quantum box inserted into a micro-pillar optical cavity, featuring three electrically insulated bonding pads and adjustable voltage sources, allows for dynamic control of fine structure splitting by applying electrical fields with specific orientations and intensities, enhancing the generation of single photons and entangled photon pairs
Data Source
AI summary
A device for generating photons includes a quantum box inserted into an optical cavity of micro-pillar type having at least one optical mode, the quantum box having at least one fundamental state and two states with one elementary excitation, the optical cavity having a bottom face and a top face, the bottom face bearing an electrical contact, the photon generation device advantageously comprises at least three electrical bonding pads electrically insulated from one another, arranged around the top face of the cavity.