Low-Energy Electro-Optic Modulator With Tunable Coupler
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Solution Overview
Problem
Existing electro-optic modulators (EOMs) face a trade-off between low energy consumption and high bandwidth operation, making it difficult to achieve ultra-low energy-per-bit (EPB) modulation at frequencies greater than 10 GHz due to the optical linewidth of Bragg resonator EOMs.
Innovation Solution
The introduction of an ultra-high quality-factor (high-Q) optical cavity coupled to a resonant EOM with a tunable coupler, allowing for low EPB operation and high bandwidth by modulating optical coupling with small electro-optic perturbations, and broadening the linewidth to achieve greater than 100 GHz modulation bandwidth without compromising signal size and noise ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional Mach-Zehnder interferometer configuration is used, then sufficient phase shift is achieved, but device size becomes large and energy consumption increases
Solution Approach 1:
The patent changes the fundamental operating principle from phase-shift-based Mach-Zehnder interferometry to resonance-based coupling modulation. By utilizing a high-Q resonator with quality factor Q>10000, the system achieves modulation through resonant frequency coupling between the resonator and waveguide, eliminating the need for long propagation paths and large device footprints while maintaining sufficient modulation depth
Solution Approach 2:
The patent replaces the mechanical/optical path-based phase modulation mechanism with an electromagnetic resonance-based coupling mechanism. The electro-optic effect is applied to modulate the resonant frequency of the cavity, which then modulates the coupling strength between the resonator and the waveguide, achieving modulation without requiring physical path length changes or large interferometer structures
2Measurement precision
If traditional EOM with long propagation path is used, then sufficient modulation depth is achieved, but energy consumption increases
Solution Approach 1:
The patent changes the modulation mechanism from direct phase modulation requiring long propagation paths to resonance frequency modulation. The high-Q resonator amplifies the electro-optic effect by confining light for multiple round trips, achieving sufficient modulation depth with much shorter interaction lengths and lower energy consumption per bit
Solution Approach 2:
The patent utilizes optical resonance, which can be understood as a form of electromagnetic vibration, where light oscillates at resonant frequencies within the cavity. This resonant oscillation enhances the interaction between light and the electro-optic material, amplifying the modulation effect and reducing the energy required to achieve a given modulation depth
3Reliability
If low temperature operation is implemented, then superconducting circuit performance is improved, but heat dissipation from EOM detrimentally affects circuit performance
Solution Approach 1:
The patent changes the modulation approach to resonance-based coupling, which requires smaller electro-optic perturbations compared to traditional phase modulation. This reduces the power consumption of the EOM and consequently the heat dissipation, protecting the sensitive superconducting circuits from thermal damage while maintaining modulation functionality
4Use of energy by moving object
If Bragg resonator EOM is used, then low EPB is achieved, but bandwidth is limited to less than 10 GHz
Solution Approach 1:
The patent introduces a tunable coupler that dynamically adjusts the coupling strength between the high-Q resonator and the waveguide. By controlling the coupling rate, the system can optimize the trade-off between energy efficiency (stronger coupling for lower EPB) and bandwidth (weaker coupling for broader linewidth), enabling adaptive operation across different bandwidth requirements including frequencies greater than 10 GHz
Solution Approach 2:
The patent uses the tunable coupler to pre-establish the optimal coupling conditions before modulation occurs. The coupler is configured to provide the appropriate coupling strength for the desired operating bandwidth, allowing the high-Q resonator to achieve both low energy-per-bit and high bandwidth performance simultaneously through proper coupling management
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 solution enables low EPB operation at 100 GHz bandwidth with improved signal-to-noise ratio and reduced energy consumption, overcoming the energy-bandwidth trade-off in EOMs.
Implementation Method 1
the strength of the electro-optic effect requires light to propagate many millimeters such that the magnitude of the phase shift is sufficient
Implementation Method 2
it is based on a high-Q (quality-factor greater than 10,000) optical cavity that is coupled to a resonant EOM
Implementation Method 3
with an electro-optic tunable coupler... a tunable coupler... modulating optical coupling with small electro-optic perturbations
Data Source
AI summary
An electro-optic modulator comprises a resonator comprising a first waveguide having a first end and second end; a first grating at the first end; and a second grating at the second end. An input channel is in communication with the resonator, and comprises a second waveguide having a first end and second end; an input port at the first end; a third grating at the second end; and a first coupler configured to couple light between the second waveguide and the first waveguide. An output channel is in communication with the resonator, and comprises a third waveguide having a first end and second end; an all-pass filter at the first end; a readout port at the second end; and a second coupler configured to couple light between the first and third waveguides. The all-pass filter is configured to adjust a coupling strength between the second coupler and the readout port.