Coupling Modulated Micro-Ring Resonator for Compact Silicon Photonic Modulation
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Solution Overview
Problem
Mach-Zehnder interferometer (MZI)-based modulators have large footprints and high energy consumption due to the need for long phase shifter segments and traveling-wave electrodes, limiting their integration in silicon photonic-based integrated circuits and their application in coherent modulation formats.
Innovation Solution
A micro-ring resonator modulator with a shorter optical feedback waveguide and bent optical waveguide arms, incorporating tunable phase shifters and optical ring resonators, which reduces the physical and optical length of the modulator, allowing for higher electro-optic bandwidths in a compact footprint.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If MZI-based modulators use long phase shifter segments to achieve sufficient phase shift, then the phase modulation capability is improved, but the device footprint and energy consumption increase significantly
Solution Approach 1:
The patent changes the operating principle from direct phase shifting in MZI to resonance condition control in MRR. By tuning the resonance condition of the micro-ring resonator through carrier depletion, the device achieves strong light-matter interaction with much shorter interaction lengths, dramatically reducing the footprint while maintaining phase modulation capability
Solution Approach 2:
The patent replaces the MZI interference-based modulation mechanism with MRR resonance-based modulation. This substitution enables achieving the same modulation function with a compact structure by utilizing the high Q-factor resonance enhancement in the micro-ring cavity, which concentrates the optical field and strengthens the electro-optic effect
2Speed
If MZI-based modulators use traveling-wave electrodes to achieve high electro-optic bandwidth, then the bandwidth is improved, but the device complexity and footprint increase
Solution Approach 1:
The patent replaces the traveling-wave electrode structure with a lumped-element carrier depletion approach in the MRR. The resonant enhancement in the MRR allows sufficient interaction strength with shorter electrodes, enabling high bandwidth without the complexity of traveling-wave design while maintaining compact integration
Solution Approach 2:
The MRR structure serves multiple functions simultaneously: it provides resonance enhancement for strong interaction, defines the modulation mechanism through carrier depletion, and enables both intensity and phase modulation capabilities in a single compact device, eliminating the need for separate long phase shifter segments
3Area of stationary object
If MRR modulators use intracavity optical modulation, then the device footprint is reduced, but the electro-optic bandwidth is limited by cavity photon lifetime
Solution Approach 1:
The patent introduces an optical feedback mechanism where the modulated light from the MRR is fed back through a feedback waveguide to the MZI input. This feedback loop enables the system to overcome the bandwidth limitation imposed by the cavity photon lifetime, allowing the electro-optic bandwidth to exceed the resonance linewidth while maintaining the compact MRR structure
4Area of stationary object
If MRR modulators use intracavity modulation, then the footprint is compact, but the phase response becomes nonlinear limiting coherent modulation
Solution Approach 1:
The patent segments the modulation function into two parts: the MRR provides compact resonance enhancement and the MZI provides linear phase combination. By separating these functions and combining them through feedback, the system achieves both compact footprint and linear phase response suitable for coherent modulation formats
Solution Approach 2:
The MZI acts as an intermediary that linearizes the phase response. The feedback mechanism transfers the MRR output through the MZI, which combines the optical fields with linear interference, thereby correcting the nonlinear phase characteristics of the intracavity MRR modulation
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 higher electro-optic bandwidths with reduced power consumption and smaller on-chip footprint, facilitating the integration of micro-ring resonator modulators in silicon photonic-based circuits and improving their performance in both PAM and coherent modulation formats.
Implementation Method 1
an optical feedback waveguide connecting an optical output of the second optical coupler to an optical input of the first optical coupler
Implementation Method 2
The Mach-Zehnder interferometer (MZI)-based modulator (MZM) is one of the most prominent modulator types used in commercial optical communication systems
Implementation Method 3
the first optical waveguide comprises a first bent optical waveguide arm; and wherein the second optical waveguide comprises a second bent optical waveguide arm
Data Source
AI summary
An optical resonant modulator based on coupling modulation, comprising a resonant structure with an embedded Mach-Zehnder interferometer that is differentially driven to induced amplitude modulation at the output port. The principle of coupling modulation enables high data/baud rates to be achieved in a photonic integrated circuit, e.g. silicon, footprint that is considerably smaller than that of a conventional traveling-wave Mach-Zehnder modulator, in particular by utilizing space saving features, such as ring resonator phase shifters and bend waveguide arms.