Frequency Selective Optical Coupler for Photon Pair Generation
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Solution Overview
Problem
Integrated photonic ring resonators suffer from inherent 50% loss when critically coupled, limiting the efficiency of single photon generation and entangled photon pair production due to lack of wavelength discriminating couplers and inefficient pump light filtering in integrated photonic devices.
Innovation Solution
A frequency selective optical coupling device with a Dual Mach-Zehnder interferometer design, featuring misbalanced legs that selectively transmit or reflect pump and signal wavelengths, allowing for critical coupling of pump photons and efficient generation and filtering of entangled photon pairs, utilizing heated media for electronic control of optical waveguide dimensions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If ring resonators are critically coupled to waveguides for photon generation, then photon-pair generation efficiency is improved, but inherent 50% loss occurs due to scattering and coupling limitations
Solution Approach 1:
The device is segmented into distinct functional regions: an input bus waveguide for pump coupling, a ring resonator for photon-pair generation, and multiple output bus waveguides for separated wavelength outputs. This segmentation allows independent optimization of pump coupling and signal extraction, resolving the contradiction between generation efficiency and loss.
Solution Approach 2:
Different regions of the device have different coupling characteristics optimized for specific wavelengths. The input coupler is optimized for pump wavelength coupling, while output couplers are optimized for signal and idle photon extraction. This local quality differentiation enables high efficiency at each stage without suffering from the inherent 50% loss of uniform critical coupling.
2Device complexity
If single bus resonator configuration is used, then device complexity is reduced, but photon loss increases due to scattering within the cavity
Solution Approach 1:
The invention merges the functions of input coupling and output collection into a unified double-bus resonator structure. The input bus waveguide couples pump photons into the ring, while two output bus waveguides simultaneously collect signal and idle photons. This merging eliminates the need for additional scattering loss that would occur in single-bus configurations while maintaining manageable device complexity.
3Productivity
If double bus resonator configuration is used for photon output, then photon collection is improved, but effective loss remains 50% due to equal probability splitting
Solution Approach 1:
The output couplers are designed with different coupling strengths optimized for specific wavelength ranges. One output coupler is optimized for signal wavelength while the other is optimized for idle wavelength. This local quality differentiation ensures that generated photons are directed to the appropriate output channel with high efficiency, eliminating the 50% effective loss from equal probability splitting.
Solution Approach 2:
The coupling parameters of the output bus waveguides are independently optimized for different wavelengths. By changing the coupling strength parameters at different locations around the ring, the device achieves wavelength-selective photon extraction, maximizing collection efficiency while minimizing effective loss for each photon type.
4Device complexity
If wavelength discriminating couplers are not implemented, then device complexity is reduced, but pump light filtering efficiency deteriorates
Solution Approach 1:
The input and output couplers have different local characteristics optimized for their specific functions. The input coupler is designed for broadband pump wavelength coupling, while the output couplers are designed for narrowband signal and idle wavelength extraction. This local quality differentiation provides inherent pump light filtering without requiring additional complex wavelength-selective components.
Solution Approach 2:
The device segments the optical path into pump input region and signal output regions with distinct coupling characteristics. This segmentation naturally separates pump light from generated photons, providing pump light filtering as a byproduct of the functional segmentation rather than requiring additional filtering components.
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 maximizes photon generation rate, minimizes noise by filtering pump light, and achieves 100% coincidence ratio for heralding efficiency, enhancing the generation of entangled photon states for quantum information processing.
Implementation Method 1
utilizing heated media for electronic control of optical waveguide dimensions
Implementation Method 2
Dual Mach-Zehnder interferometer design, featuring misbalanced legs that selectively transmit or reflect pump and signal wavelengths
Implementation Method 3
Micro ring resonators are becoming a key component of such systems as they have been shown to be effective as photon-pair sources by means of exploiting a materials nonlinearity for spontaneous parametric downconversion (SPDC) or spontaneous four wave mixing (SFWM)
Implementation Method 4
Micro ring resonators are becoming a key component of such systems as they have been shown to be effective as photon-pair sources by means of exploiting a materials nonlinearity for spontaneous parametric downconversion (SPDC) or spontaneous four wave mixing (SFWM)
Data Source
AI summary
The invention provides an apparatus for optical integrated on-chip generation of photon pairs as a building block to create entangled photon states required for quantum information processing. The invention provided a frequency selective optical coupling device which controls the transmission of light by varying the relative dimensions of otherwise symmetrical linear optical waveguides tangential to an annular optical waveguide, thereby controlling the coupling of light between the linear optical waveguides and the annular optical waveguide. Dimensional change of the optical waveguides is achieved by a heated medium in proximity of the optical waveguides and under electronic control.