Coupling-Modulated Ring Resonator for High-Bandwidth Optical Modulation
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Solution Overview
Problem
Conventional ring resonator modulators are limited by photon lifetime, leading to restricted electro-optic bandwidth, and Mach-Zehnder interferometers require large footprints and high energy consumption due to long phase shifter segments and traveling-wave electrodes.
Innovation Solution
A coupling-modulated ring resonator modulator that modulates optical coupling coefficients using a Mach-Zehnder interferometer optical coupler with segmented RF electrodes, reducing the need for long phase shifts and traveling-wave electrodes, thereby overcoming photon lifetime limitations and achieving higher electro-optic bandwidths in a compact footprint.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If intracavity modulation is used in ring resonator modulators, then compact footprint is achieved, but electro-optic bandwidth is limited by photon lifetime
Solution Approach 1:
Instead of modulating the optical field inside the cavity (intracavity modulation), this patent modulates the coupling coefficient between the waveguide and resonator (extracavity modulation). This inversion of the modulation location allows the optical field to build up fully in the cavity while the coupling control happens outside, eliminating the bandwidth limitation imposed by photon lifetime and enabling high-speed operation while maintaining compact footprint.
2Adaptability or versatility
If MZM is integrated into silicon photonic PICs, then coherent modulation is achieved, but footprint and energy consumption increase
Solution Approach 1:
This patent changes the fundamental operating parameter from phase modulation (required for coherent formats in MZMs) to coupling coefficient modulation. By modulating the coupling between waveguide and resonator, the device achieves both amplitude and phase modulation capabilities, enabling coherent formats like QPSK and QAM while maintaining a compact resonator-based footprint.
3Power
If long phase shifter segments are used in MZMs, then low half-wave voltage is achieved, but device length and complexity increase
Solution Approach 1:
The resonator acts as an intermediary that amplifies the modulation effect. Instead of using long phase shifters to achieve sufficient modulation depth, a short phase shifter modulates the coupling coefficient, and the resonator's high Q-factor provides the necessary field enhancement, achieving low half-wave voltage with minimal phase shifter length.
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 chip footprint, suitable for both PAM and coherent applications, by modulating optical coupling rather than optical path length, and utilizing segmented RF electrodes to enhance phase shifts.
Implementation Method 1
Mach-Zehnder interferometer (MZI)-based modulator
Implementation Method 2
phase shift, φ static , applied to one or both of the MZM arms
Implementation Method 3
ring resonator (RR) modulator
Implementation Method 4
feedback optical waveguide
Data Source
Figure 1
Figure 2
Figure 3A
AI summary
An apparatus includes a Mach-Zehnder optical modulator, an optical coupler with more than two optical ports, and an optical phase shifter. The Mach-Zehnder optical modulator includes first and second other optical couplers and first and second optical waveguides. Each of the optical waveguides connects a corresponding optical output of the first other optical coupler to a corresponding optical input of the second other optical coupler. The apparatus also includes an optical feedback waveguide connecting an optical output of the second other optical coupler to an optical input of the first other optical coupler. A first segment of the optical feedback waveguide is optically connected to a second segment of the optical feedback waveguide by the optical coupler with more than two optical ports. The first optical phase shifter is adjacent to at least one of the first and second optical waveguides and includes a plurality of electrode segments.