Rib Waveguide Optical Modulator with Segmented Slab Areas
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Solution Overview
Problem
Existing optical modulation elements face a trade-off between increasing performance speed and optical loss, with methods to reduce series resistance leading to increased optical absorption and power consumption.
Innovation Solution
The optical modulation element incorporates a rib type optical waveguide with a P-N junction and thin films made of materials with different electron affinities, forming two-dimensional hole and electron systems to reduce series resistance while maintaining low optical loss, using Si for the waveguide and Ge for the thin films to facilitate integration on a CMOS platform.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If doping concentration in slab areas is increased to reduce series resistance, then performance speed is improved, but optical absorption increases causing higher optical loss
Solution Approach 1:
The invention divides the slab area into two distinct regions: a first slab area with high doping concentration for low series resistance, and a second slab area with low doping concentration for low optical absorption. This segmentation allows each region to optimize for its specific function, resolving the contradiction between speed and optical loss.
Solution Approach 2:
Different doping concentrations are applied to different spatial regions of the slab area. The first slab area (near the P-N junction) has high doping for electrical performance, while the second slab area (away from the junction) has low doping for optical transparency. This local differentiation resolves the global contradiction by making properties location-dependent.
2Productivity
If doping concentration is increased four times to reduce series resistance, then carrier density increases improving speed, but optical absorption increases by 30% increasing power consumption
Solution Approach 1:
The slab area is segmented into a first region with high doping (4x concentration) for low series resistance and fast response, and a second region with low doping for minimal optical absorption. This segmentation enables high productivity in the first region without the penalty of high power consumption in the second region.
Solution Approach 2:
High doping concentration is localized only where needed for electrical performance (first slab area near the P-N junction), while the second slab area maintains low doping for optical efficiency. This local quality differentiation resolves the contradiction between productivity and energy use.
3Loss of time
If series resistance is reduced by increasing carrier density, then response time constant decreases improving speed, but optical loss increases
Solution Approach 1:
The invention segments the slab area to provide high carrier density only in the first slab area near the P-N junction, which is sufficient to reduce the response time constant. The second slab area maintains low carrier density to minimize optical loss, thus resolving the contradiction between time loss and energy loss.
Solution Approach 2:
High carrier density is concentrated locally in the first slab area where it is most effective for reducing response time, while the second slab area has low carrier density for optical efficiency. This local quality approach resolves the global trade-off between speed and optical loss.
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 configuration significantly increases performance speed up to 100 GHz while preventing an increase in optical loss, improving beam confinement and frequency characteristics compared to previous technologies.
Implementation Method 1
a two-dimensional hall system, that is, a thin electron hole layer, is formed on a first thin film that is in contact with the P-type slab area
Implementation Method 2
a rib type optical waveguide that includes a rib portion that has a P-N junction
Data Source
AI summary
An optical modulation element 100 includes a rib type optical waveguide that includes a rib portion 112 that has a P-N junction, a P-type slab area 114 that continuously extends from a P type area of the rib portion 112, and an N-type slab area 116 that continuously extends from an N type area of the rib portion 112. A first thin film 130 is formed on the P-type slab area 114 and is made of a material having an electron affinity that is different from that of the P-type slab area 114.