Double-Pass Entangled Photon Source Without Walk-Off Compensation
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Solution Overview
Problem
Existing entangled photon sources are complex, difficult to adjust, and require temporal compensation for the walk-off effect, leading to reduced quality or unsuitable mass production.
Innovation Solution
A simplified entangled photon source design using a laser, nonlinear element, dichroic element, and reflective elements to generate polarization entangled photon pairs with a double-pass configuration through a periodically poled Lithium Niobate or potassium titanyl phosphate crystal, eliminating the need for additional compensation crystals and maintaining equal pump power for high-quality entanglement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a Sagnac-source configuration or linear source with multiple crystals is used, then entangled photon pairs can be generated, but the device complexity increases and alignment becomes difficult
Solution Approach 1:
The patent merges the functions of multiple crystals into a single periodically poled nonlinear crystal. The crystal is designed with multiple poling periods along its length, allowing different sections to generate entangled pairs with different polarizations. This consolidation eliminates the need for separate crystals and reduces alignment complexity while maintaining high entanglement quality.
Solution Approach 2:
The single periodically poled nonlinear crystal performs multiple functions: it generates both horizontally and vertically polarized entangled photon pairs through different poling sections, replaces what would traditionally require multiple separate crystals, and maintains interferometric stability without requiring complex Sagnac loop configurations.
2Reliability
If temporal compensation of the walk-off effect is implemented, then entanglement quality is maintained, but the device complexity and difficulty of mass production increase
Solution Approach 1:
The patent changes the temporal parameters by using a short interaction length crystal and broad spectral bandwidth. This approach inherently minimizes the walk-off effect without requiring additional compensation crystals or complex temporal alignment mechanisms, making the system easier to manufacture and maintain while preserving entanglement quality.
3Reliability
If multiple optical components are used in a Sagnac configuration, then entangled photon pairs can be generated, but the alignment task becomes crucial and difficult
Solution Approach 1:
The patent combines multiple optical functions into a single periodically poled nonlinear crystal, eliminating the need for separate crystals, wave plates, and complex Sagnac loop configurations. This single-component approach drastically simplifies alignment while maintaining reliable entangled photon pair generation.
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 source achieves high-efficiency, stable generation of high-quality entangled photon pairs with reduced complexity and maintenance, enabling easier alignment and operation, suitable for mass production.
Implementation Method 1
a laser configured to generate a polarized laser beam in the range of 630 nm to 790 nm
Implementation Method 2
a nonlinear element configured to generate photon pairs by the transmission of the laser beam
Data Source
Figure 1
Figure 2
AI summary
It is provided an entangled photon source (1) for the generation of polarization entangled photon pairs (9) comprising a laser (2) configured to generate a polarized laser beam (3) in the range of 630 nm to 790 nm, and a nonlinear element (4) configured to generate photon pairs (5) by the transmission of the laser beam (3), and a dichroic element (8) configured to separate the entangled photon pairs (9) and the laser beam (3). Essential is, that the source (1) comprises in addition a polarization rotation element (6) and a reflection element (7) configured to reflect the laser beam (3) after the first transmission through the nonlinear element (4) for a second transmission through the nonlinear element (4).