Linear Optical Phase Modulators for Silicon Photonics
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Solution Overview
Problem
Silicon photonic devices face nonlinearity issues in phase modulation due to the inherent nonlinear relationship between depletion region width and applied voltage, limiting the linearity of phase modulation and Spurious-Free Dynamic Range (SFDR) in Radio over Fiber (RoF) systems.
Innovation Solution
The development of linear optical phase modulators using a PN junction-based depletion of carriers, where the optical field spatial distribution is tailored to offset nonlinearity by engineering an overlap between the depletion width and optical mode, achieving a linear or substantially linear phase modulation response.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a PN junction-based depletion of carriers is used to cause optical phase modulation, then the phase modulation can be achieved in silicon photonic devices, but the inherent nonlinear relationship between depletion region width and applied voltage degrades the linearity of phase modulation
Solution Approach 1:
The patent applies parameter changes by modifying the optical field spatial distribution parameters (mode shape, field intensity profile) to compensate for the nonlinear depletion width-voltage relationship. By engineering the optical mode parameters to have specific spatial distributions, the system achieves linear phase modulation despite the inherent nonlinearity in the PN junction depletion region.
Solution Approach 2:
The patent introduces the optical field spatial distribution as an intermediary element that mediates between the nonlinear electrical input (applied voltage) and the optical output (phase modulation). By carefully designing the optical mode profile, this intermediary function transforms the nonlinear voltage-depletion relationship into a linear phase modulation response.
2Reliability
If the optical field spatial distribution is tailored to offset nonlinearity, then the phase modulation linearity is improved, but the device design and manufacturing complexity increases
Solution Approach 1:
The patent applies local quality by creating specific spatial distributions of the optical field at different locations within the waveguide structure. By engineering the local optical mode properties (field intensity, mode shape) in specific regions, the system achieves the desired nonlinearity compensation while maintaining compatibility with standard fabrication processes.
Solution Approach 2:
The patent utilizes the dynamic response of the optical mode to voltage changes, engineering the mode structure to provide a linearizing effect. The optical field distribution is designed to dynamically compensate for the nonlinear depletion region expansion with applied voltage, achieving linear phase modulation through the interplay of optical and electrical fields.
3Ease of manufacture
If standard optical modes are used in the waveguide, then the manufacturing process is simpler, but the phase modulation linearity is degraded due to the nonlinear depletion width-voltage relationship
Solution Approach 1:
The patent modifies the optical mode parameters (spatial distribution, field intensity profile) while maintaining compatibility with standard waveguide fabrication. By changing the mode parameters through careful waveguide design, the system achieves linear phase modulation without requiring complex manufacturing processes.
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 approach enables high linearity and improved Spurious-Free Dynamic Range (SFDR) in silicon photonics and semiconductor-based photonics platforms, enhancing the performance of photonic devices for analog applications by linearizing the voltage to phase transfer function.
Implementation Method 1
using depletion width modulation and/or free carrier dispersion in combination of a tailoring the spatial distribution of the guided light
Implementation Method 2
a PN junction-based depletion of carriers to cause optical phase modulation
Implementation Method 3
an optical waveguide formed on the substrate and structured to guide light in one or more optical modes
Data Source
AI summary
Methods, systems, and devices are disclosed for linear optical phase modulators. In some aspects, a linear optical phase modulator device is provided to include a substrate; a PN junction formed on the substrate to include a P region, a N region and a depletion region formed by the P and N regions; and an optical waveguide formed on the substrate and structured to guide light in one or more optical modes to have a spatial optical intensity distribution based on a free carrier density spatial distribution in the PN junction in such that the depletion region exhibits a substantially linear response with regard to a voltage applied to the PN junction to modulate a phase of the light guided by the optical waveguide.