Grating Coupler for Waveguide Using Multi-Angle Light Splitting
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Solution Overview
Problem
Conventional symmetric surface corrugation grating couplers in heat-assisted magnetic recording have low coupling efficiency due to a limited acceptance angle of incidence, making it difficult to achieve high efficiency in practical HAMR sliders.
Innovation Solution
The use of an optical waveguide with a grating coupler that splits the incident light beam into multiple beams striking the grating at different angles, and a design featuring double corrugations with varying groove periods and duty cycles, or a limited number of pitches, to increase the acceptance angle of incidence and enhance coupling efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a conventional symmetric surface corrugation grating coupler is used, then the structure is simple and easy to manufacture, but the coupling efficiency is low due to limited acceptance angle of incidence
Solution Approach 1:
The incident beam is divided into multiple beams by an optical element (such as a beam splitter or diffraction grating), so that instead of one beam at a single angle, multiple beams strike the grating at different angles simultaneously. This segmentation of the beam allows the system to overcome the limited acceptance angle of conventional gratings by distributing the optical energy across multiple acceptable incidence angles, thereby improving coupling efficiency into the waveguide
Solution Approach 2:
The invention transitions from a single-angle incidence approach to a multi-angle incidence approach by introducing an optical element that splits the beam. This adds a dimensional aspect to the angle of incidence, transforming the problem from one-dimensional (single angle) to multi-dimensional (multiple angles), thereby expanding the effective acceptance angle and improving coupling efficiency
2Reliability
If the acceptance angle of incidence is increased to improve coupling efficiency, then more light can be coupled into the waveguide, but the grating design becomes more complex
Solution Approach 1:
An optical element (beam splitter, diffraction grating, or prism) is introduced as an intermediary component between the light source and the waveguide grating coupler. This intermediary splits the incident beam into multiple beams that strike the grating at different angles, effectively increasing the acceptance angle. While this adds a component, it allows the use of a relatively simple grating structure rather than requiring a complex variable-geometry grating, thus balancing the trade-off between complexity and performance
3Manufacturing precision
If a limited number of pitches is used in the grating, then the manufacturing precision requirements are reduced, but the coupling efficiency may be affected
Solution Approach 1:
The invention optimizes the grating parameters (such as groove depth, duty cycle, and pitch) specifically for multi-angle incidence conditions. By adjusting these parameters, the grating is designed to efficiently couple light from multiple incident angles into the waveguide mode. This parameter optimization allows the use of a limited number of pitches with relaxed manufacturing tolerances while maintaining high coupling efficiency, as the multi-beam approach compensates for the reduced number of periods
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 significantly improves the coupling efficiency by allowing a wider range of incident angles, increasing the probability of optimal coupling even with misalignment, and achieving higher peak efficiencies up to 55% with a broader tolerance, suitable for practical applications.
Implementation Method 1
a grating for coupling light into the waveguide
Implementation Method 2
an optical element for splitting a light beam into a plurality of beams that strike the grating at different angles of incidence
Data Source
AI summary
An apparatus comprises an optical waveguide, a grating for coupling light into the waveguide, and an optical element for splitting a light beam into a plurality of beams that strike the grating at different angles of incidence.