Distributed Feedback Light Source With Metal Barrier Confinement
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Solution Overview
Problem
The integration of III-V light sources with distributed feedback resonant cavities onto silicon substrates is hindered by significant optical losses due to the higher optical index of silicon, which causes guided modes to couple with the substrate, reducing confinement efficiency.
Innovation Solution
Incorporating a relatively thick lower cladding layer or using a low-index oxide or nitride layer as a barrier between the III-V stack and the silicon substrate, or replacing the oxide/nitride layer with a metal layer, such as gold, silver, or titanium, to improve confinement and reduce substrate coupling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a thick lower cladding layer is used to reduce substrate coupling, then optical losses are reduced, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The patent introduces an intermediary layer with intermediate optical index positioned between the high-index silicon substrate and the low-index lower cladding layer. This intermediate layer acts as a mediator that gradually transitions the optical index, reducing the abrupt index contrast that causes guided mode coupling to the substrate. By using this intermediate layer, the patent achieves effective optical confinement without requiring excessive thickness of the lower cladding layer, thereby reducing device complexity and manufacturing difficulty while maintaining low optical losses.
2Reliability
If the lower cladding layer thickness is increased to compensate for penetration depth, then confinement effectiveness is improved, but integration complexity and raw material cost increase
Solution Approach 1:
The intermediate layer with intermediate optical index serves as a mediator that reduces the required thickness of the lower cladding layer. By gradually transitioning the optical index from the silicon substrate through the intermediate layer to the lower cladding layer, the patent achieves effective confinement with a thinner lower cladding layer, thereby reducing integration complexity and raw material cost while maintaining confinement effectiveness.
Solution Approach 2:
The patent changes the optical index parameter by introducing an intermediate layer with an optical index that is intermediate between the silicon substrate and the lower cladding layer. This parameter change allows for more gradual optical confinement, enabling the use of a thinner lower cladding layer while maintaining effective confinement, thus reducing integration complexity and material cost.
3Loss of energy
If oxide or nitride layers are used as low-index barriers, then substrate coupling is reduced, but spectral range is limited due to high losses at wavelengths greater than 4 μm
Solution Approach 1:
The patent changes the material parameter by selecting an intermediate layer material whose optical properties are wavelength-dependent in a favorable way. The intermediate layer is chosen to have an optical index that provides effective confinement across a broad spectral range, including mid-infrared wavelengths greater than 4 μm. This parameter change allows the system to maintain low substrate coupling losses while extending the operational spectral range beyond the limitations of oxide or nitride layers.
Solution Approach 2:
The patent uses a composite structure consisting of multiple layers with different optical properties: the silicon substrate, the intermediate layer with intermediate optical index, and the lower cladding layer with low optical index. This composite material approach allows the system to combine the benefits of each layer, achieving effective substrate coupling reduction across a broad spectral range while avoiding the high losses associated with oxide or nitride layers at wavelengths greater than 4 μm.
4Reliability
If a metal layer is used to replace oxide/nitride barrier, then confinement is improved and spectral range compatibility is increased, but manufacturing complexity increases
Solution Approach 1:
The metal layer serves as an intermediary between the silicon substrate and the lower cladding layer, providing effective optical confinement through its unique optical properties. The metal layer's high refractive index and ability to support surface plasmon modes enable effective confinement across a broad spectral range. By positioning the metal layer as an intermediate structure, the patent achieves improved confinement while managing manufacturing complexity through systematic integration into the existing layer structure.
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 proposed solutions effectively reduce optical losses and improve the confinement of resonant guided modes, allowing for the integration of III-V light sources on high-index substrates like silicon with reduced overall size and increased spectral range compatibility.
Implementation Method 1
the lower metal layer prohibits transmission of resonant guided modes to the substrate
Implementation Method 2
The lower metal layer enables the source to be integrated onto a substrate with a high optical index, for example of silicon
Implementation Method 3
A diffraction grating is used to apply feedback to the magnetic field to establish the guided modes
Implementation Method 4
configured so that at least one stationary mode of an electromagnetic field, referred to as a 'resonant guided mode', is established in parallel to the substrate
Implementation Method 5
The active region is configured to emit an electromagnetic field by spontaneous and/or stimulated emission
Implementation Method 6
The active region is configured to emit an electromagnetic field by spontaneous and/or stimulated emission
Data Source
AI summary
One aspect of the invention relates to a distributed feedback light source (101) comprising a stack of layers (103) extending in parallel to a substrate (102), the source (101) also comprising a first metal layer (111) extending between the substrate (102) and the stack (103).