Thermally Tunable Optical Waveguide with Thermal Isolation Gap
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Solution Overview
Problem
Silicon-based optical devices face high power consumption during thermal tuning due to their high thermal conductivity, which offsets their advantages and makes them less suitable for implementing optical communication systems, especially in computing systems with multiple instances of optical devices.
Innovation Solution
An optical device with a thermally tunable semiconductor waveguide is designed, featuring a substrate, an intermediate insulator layer, and a semiconductor layer with vias that create a gap for thermal isolation, reducing thermal coupling and power consumption by increasing thermal impedance between the waveguide and the external environment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If silicon-based optical devices are used, then miniaturization and integration capabilities are improved, but thermal conductivity increases causing excessive power consumption during thermal tuning
Solution Approach 1:
The device is segmented into distinct functional layers: a silicon-based optical waveguide layer for light guidance, a separate heater layer for thermal tuning, and an intermediate sacrificial layer that creates thermal isolation. This segmentation allows the silicon waveguide to maintain its integration benefits while the heater is thermally isolated to reduce power consumption during tuning operations.
Solution Approach 2:
The heating function is extracted from the silicon waveguide structure and placed in a separate heater layer. The sacrificial layer material is removed to create void space, extracting the thermal coupling pathway between the heater and substrate. This extraction reduces thermal conductivity from the heater to the environment, lowering power consumption while preserving the silicon waveguide's integration capabilities.
2Use of energy by moving object
If direct heating technique is used, then energy efficiency is improved, but optical losses increase due to free-carrier absorption
Solution Approach 1:
The device structure is designed with local quality variations: the heater layer is doped to provide localized heating functionality, while the optical waveguide region maintains low doping to minimize free-carrier absorption. The sacrificial layer creates a localized void that provides thermal isolation specifically at the heater position, allowing direct heating to be energy-efficient without the harmful optical losses in the optical path.
Solution Approach 2:
The sacrificial layer acts as an intermediary that is selectively removed to create thermal isolation. This intermediary structure enables the heater to be thermally decoupled from the substrate, reducing the power needed for thermal tuning. Simultaneously, the optical waveguide maintains its low-doping region to minimize free-carrier absorption, resolving the contradiction between energy efficiency and optical losses.
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 significantly reduces power consumption for thermal tuning, enabling efficient operation in high-performance computing systems and DWDM systems with reduced component count and increased reliability.
Implementation Method 1
Thermal tuning is a popular tuning technique because it provides the ability to produce large phase shifts
Implementation Method 2
the operating wavelength of a silicon-based optical device (such as the resonant wavelength of an optical resonator) strongly depends on temperature
Implementation Method 3
a gap corresponds to a removed sacrificial portion of the first intermediate layer... reducing thermal coupling and power consumption by increasing thermal impedance
Data Source
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AI summary
Embodiments of an optical device, an array of optical devices, and a technique for fabricating the optical device or the array are described. This optical device is implemented on a substrate (such as silicon), and includes a thermally tunable optical waveguide that has good thermal isolation from its surroundings. In particular, a portion of a semiconductor in the optical device, which includes the optical waveguide, is free standing above a gap between the semiconductor layer and the substrate. By reducing the thermal coupling between the optical waveguide and the external environment, the optical device can be thermally tuned with significantly less power consumption.