Spin-Injected Quantum Dot Source for Circularly Polarized Photons
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Solution Overview
Problem
Existing single-photon source devices struggle to emit single-photons with a determined polarization direction efficiently, leading to reduced emission efficiency due to the need for polarizers that block photons with different polarization directions.
Innovation Solution
A single-photon source device is designed with a semiconductor substrate and a spin injection layer to inject spin-polarized carriers into a semiconductor quantum-dot structure, using pulsed voltage and magnetic or electrical controls to determine the circular polarization direction of emitted photons, and optionally incorporating a spin filtering layer and distributed Bragg reflectors for enhanced efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a polarizer is used to filter single-photons with different polarization directions, then the polarization direction of emitted photons is determined, but the emission efficiency of single-photons is reduced by half due to photons being blocked
Solution Approach 1:
The invention extracts and removes the polarizer component from the system by implementing spin-polarized carrier injection directly into the quantum dot. This eliminates the need for post-emission polarization filtering, allowing all emitted photons to be utilized without being blocked by a polarizer, thereby resolving the contradiction between polarization control and emission efficiency
Solution Approach 2:
The invention performs preliminary spin polarization of carriers before they recombine with the quantum dot to emit photons. By injecting spin-polarized carriers (electrons or holes) with specific spin directions into the quantum dot, the polarization state is determined in advance during the carrier injection process, rather than filtering after emission occurs. This preliminary action ensures that all emitted photons have the desired polarization direction, maintaining high emission efficiency while achieving precise polarization control
2Quantity of substance
If multiple single-photon sources are used to increase photon output, then the quantity of photons is increased, but maintaining identical polarization direction across all sources becomes complex and reduces overall efficiency
Solution Approach 1:
The invention makes each quantum dot source universal by enabling independent control of spin-polarized carrier injection for each source. Each quantum dot can be independently configured to emit photons with identical or different polarization directions by controlling the spin direction of injected carriers, eliminating the need for complex external polarization synchronization mechanisms while maintaining the ability to produce multiple identical photons
Solution Approach 2:
The invention segments the polarization control function to the individual quantum dot level through independent spin injection control. Each quantum dot source can independently generate spin-polarized carriers with controlled spin directions, allowing multiple sources to operate autonomously while producing photons with identical polarization characteristics. This segmentation simplifies the overall system by distributing the polarization control function across independent units rather than requiring centralized synchronization
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
The device achieves high-efficiency emission of single-photons with controlled circular polarization, enabling synchronized emission of multiple indistinguishable photons with identical polarization, suitable for quantum optical communication and computation.
Implementation Method 1
a spin injection layer located above the pillar structure and configured to inject a spin-polarized carrier into the semiconductor single-quantum-dot structure
Implementation Method 2
In response to the injected spin-polarized single-carrier, a single-photon is emitted from the single-quantum-dot in the semiconductor single-quantum-dot structure
Implementation Method 3
optionally incorporating a spin filtering layer and distributed Bragg reflectors for enhanced efficiency
Data Source
AI summary
Disclosed is a single-photon source emitting light with controllable circular polarization direction. A pillar structure above a semiconductor substrate includes a semiconductor single-quantum-dot structure. A spin injection layer is arranged above the pillar structure. A pulsed voltage is applied between the spin injection layer and the semiconductor substrate to inject a spin-polarized single-carrier from the spin injection layer into the semiconductor single-quantum-dot structure. In response to the injected single-carrier, a single-quantum-dot emits a single-photon with a circular polarization direction corresponding to the spin direction of the injected single-carrier. The polarization controllable single-photon source allows to use magnetic or electrical means to modulate the circular polarization direction of single-photon. The modulation speed by electrical mean can reach up to GHz range.