Silicon Thermal-Optic Phase Shifter with P-i-N Diode Structure
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Solution Overview
Problem
Silicon photonic platforms suffer from reduced optical performance due to free-carrier absorption and two-photon absorption effects, leading to inefficient phase tuning in thermo-optic phase shifters, especially in high power applications, where silicon nitride waveguides lack a phase tuning mechanism and have a low thermal-optic coefficient.
Innovation Solution
A thermo-optic phase shifter is designed with a p-i-n diode structure and resistive heating elements, where the p-i-n diode structure is reverse-biased to mitigate two-photon absorption effects and the resistive heating elements are thermally coupled to the optical waveguide to control phase shifts, allowing for efficient phase modulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If silicon photonic platforms are used, then optical devices can be manufactured with good integration, but optical performance is reduced due to free-carrier absorption and two-photon absorption effects
Solution Approach 1:
The waveguide is segmented into distinct regions with different doping types (P-type, N-type, and intrinsic waveguide region). This segmentation allows each region to serve a specific function: the P-type and N-type regions provide carrier management to reduce absorption losses, while the intrinsic waveguide region maintains optical performance.
Solution Approach 2:
The patent employs a composite doped silicon waveguide structure combining P-type and N-type doped regions with an intrinsic silicon waveguide region. This composite structure leverages the electrical properties of doped regions for carrier management while maintaining the optical properties of intrinsic silicon for low-loss light propagation.
2Power
If silicon photonic platforms are used in high power applications, then power handling capability is improved, but optical loss increases due to two-photon absorption effect
Solution Approach 1:
The patent converts the harmful two-photon absorption effect into a beneficial mechanism by using the generated free carriers in the P-type and N-type regions to create a plasma effect that compensates for losses. The high optical power that causes TPA also generates carriers that, when managed through the doped regions, can be utilized to improve overall device performance.
Solution Approach 2:
The patent changes the electrical parameters (carrier concentration, doping levels) in the waveguide regions to optimize the balance between power handling capability and optical loss. By adjusting doping concentrations and creating specific carrier distributions, the device can operate at high power levels while maintaining acceptable optical performance.
3Ease of operation
If thermo-optic phase shifting is implemented in silicon, then phase tuning is achieved, but optical power dependent phase shift causes sensing control problems
Solution Approach 1:
The patent applies local quality by creating regions with different doping characteristics (P-type, N-type, intrinsic) at specific locations within the waveguide. The P-type and N-type regions are positioned to manage carriers locally, while the intrinsic waveguide region maintains stable optical properties for reliable sensing and phase control.
4Reliability
If silicon nitride waveguides are used to mitigate optical loss, then optical performance is improved, but phase tuning efficiency decreases due to low thermal-optic coefficient
Solution Approach 1:
The patent uses composite doped silicon materials that combine the advantages of silicon (high thermal-optic coefficient for efficient phase tuning) with structural designs that mitigate its disadvantages (optical loss). The doped regions manage carriers to reduce absorption, enabling efficient thermal phase tuning without the optical loss problems of undoped silicon.
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 effectively reduces optical loss and enhances phase tuning efficiency by reversing the bias of the p-i-n diode structure and utilizing resistive heating elements to manage thermal effects, improving the performance of thermo-optic phase shifters in high power applications.
Implementation Method 1
silicon photonic platforms suffer reduced optical performance due to free-carrier absorption (FCA) introduced by a two-photon absorption (TPA) effect
Implementation Method 2
in a thermo-optic (TO) phase shifter, the TPA effect also introduces an optical power dependent phase shift
Implementation Method 3
a resistive heating element thermally coupled to the optical waveguide
Data Source
AI summary
A thermo-optic phase shifter comprises an optical waveguide comprising a P-type region comprising a first contact, an N-type region comprising a second contact, and a waveguide region disposed between the P-type region and the N-type region and having a raised portion. The thermo-optic phase shifter further comprises one or more heating elements. The one or more heating elements include one or more discrete resistive heating elements or the P-type and N-type regions driven as resistive heating elements.