Grating Element Extension Regions Scatter Slab Mode Light
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Solution Overview
Problem
In the production of grating devices, the formation of Bragg gratings on channel type optical waveguides results in unnecessary light of the slab mode being emitted, due to irregularities in pitch precision and resin defects during the nanoimprinting process, which affects the emission of light with the desired wavelength.
Innovation Solution
The solution involves forming periodic microstructures in the extension regions outside the channel type optical waveguide, covering 50% or more of the total area, to scatter and prevent the emission of unnecessary light, while maintaining the desired wavelength emission by ensuring the Bragg grating is formed on the channel type optical waveguide region with precise pitch and depth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If Bragg gratings are formed on channel type optical waveguides using nanoimprinting method, then manufacturing cost can be reduced and productivity can be improved, but pitch precision becomes irregular and resin defects occur causing unwanted slab mode light emission
Solution Approach 1:
The optical waveguide structure is segmented into a channel type optical waveguide region where Bragg gratings are formed and extension regions where periodic microstructures are formed. This segmentation allows the Bragg grating region to maintain precise pitch for wavelength selection while the extension regions with periodic microstructures scatter unwanted slab mode light, thus resolving the contradiction between manufacturing efficiency and pitch precision by distributing different functions to different segments.
Solution Approach 2:
Different regions of the optical waveguide are given different local qualities: the channel type optical waveguide region has Bragg gratings with precise pitch for wavelength selection, while the extension regions have periodic microstructures for scattering unwanted light. This local differentiation allows each region to optimize its specific function, maintaining manufacturing efficiency while ensuring optical precision where needed.
2Reliability
If Bragg gratings are formed with larger width to ensure coverage over ridge portion, then grating formation assurance is improved, but unnecessary slab mode light emission increases
Solution Approach 1:
The harmful slab mode light emission is extracted and targeted for separate处理 by introducing periodic microstructures in the extension regions. These microstructures specifically address the unwanted light emission without affecting the Bragg grating's wavelength selection function, allowing the grating to be formed with adequate width for reliability while the extension regions eliminate the harmful slab mode light.
Solution Approach 2:
The extension regions with periodic microstructures convert the potentially harmful wide grating structure that causes slab mode light into a beneficial configuration where the periodic microstructures actively scatter and eliminate the unwanted light, transforming the problem of wide grating formation into a solution that enhances overall device performance.
3Object-generated harmful factors
If periodic microstructures are formed in extension regions covering 50% or more of total area, then scattered light emission is prevented, but device complexity increases
Solution Approach 1:
The periodic microstructures are merged with the extension regions of the optical waveguide in an integrated manner. This merging allows the extension regions to serve dual purposes: as part of the waveguide structure and as scattering regions for unwanted light, thereby preventing light emission control issues without proportionally increasing device complexity.
Solution Approach 2:
The extension regions are designed to serve multiple functions: guiding light as part of the optical waveguide and scattering unwanted slab mode light through periodic microstructures. This multi-functionality allows effective light emission control while minimizing additional device complexity by making the extension regions versatile structural elements.
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 effectively scatters leaked light from the channel type optical waveguide, preventing its emission and ensuring that only the desired wavelength is emitted, thereby improving the precision of the grating pitch and enhancing the productivity and efficiency of the grating device.
Implementation Method 1
a portion of the laser light is returned to the laser by using a mirror having the wavelength selectivity utilizing the Bragg reflection
Implementation Method 2
periodic microstructures provided in the extension regions, respectively... effectively scatters leaked light from the channel type optical waveguide
Implementation Method 3
a resin layer is first formed on a semiconductor layer to form the diffraction grating. Then, a mold possessing the pattern of grooves and bumps corresponding to shape of this diffraction grating is pressed to this resin layer, and the resin layer is cured in that state
Data Source
AI summary
A grating device includes an optical material layer; a channel type optical waveguide region provided in the optical material layer; extension regions provided on the outsides of the channel type optical waveguide region, respectively; a Bragg grating provided in the channel type optical waveguide region; and periodic microstructures provided in the extension regions, respectively. The periodic microstructures are provided in 50 percent or larger of a total of areas of the extension regions.