Nonlinear Pitch Optical Grating for Divergent Beam Coupling
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Solution Overview
Problem
Conventional optical gratings face inefficiencies in light coupling due to divergence of laser beams, leading to varying angles of incidence and suboptimal coupling efficiency, which limits their performance in applications like energy-assisted magnetic recording (EAMR).
Innovation Solution
The design of an optical grating with a nonlinear pitch that varies based on the angle of incidence, combined with a reflective mirror for recirculating light, enhances coupling efficiency by matching the pitch to different angles of incidence and optimizing light alignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a conventional grating with fixed pitch is used, then the manufacturing is simple, but the coupling efficiency degrades due to beam divergence causing varying angles of incidence
Solution Approach 1:
The patent applies the dynamics principle by transitioning from a static, uniform pitch grating to a dynamic, nonlinear pitch grating where the pitch varies continuously across the grating surface. This allows the grating to adapt to different angles of incidence caused by beam divergence, maintaining high coupling efficiency across the entire beam profile rather than optimizing for a single angle.
Solution Approach 2:
The patent implements local quality by making each local region of the grating have a specific pitch value tailored to the local angle of incidence. Different portions of the grating surface have different pitch characteristics - regions receiving light at steeper angles have different pitch than regions receiving light at shallower angles, thereby optimizing coupling efficiency locally across the entire beam cross-section.
2Manufacturing precision
If the pitch is optimized for a principal angle of incidence, then the coupling efficiency is maximized for that angle, but the efficiency degrades for other angles due to beam divergence
Solution Approach 1:
The patent applies universality by designing the grating to perform multiple functions simultaneously - it couples light effectively across a wide range of incidence angles rather than optimizing for a single principal angle. The nonlinear pitch distribution enables the grating to handle divergent beams with various angles, making it universally effective for the entire beam profile.
Solution Approach 2:
The patent implements parameter changes by varying the pitch parameter continuously across the grating surface according to a nonlinear function. This spatial variation of the pitch parameter allows the grating to accommodate different angles of incidence, effectively changing the grating's coupling characteristics at different locations to match the local incident light angles.
3Manufacturing precision
If the grating geometry is closely controlled to achieve high coupling efficiency, then the manufacturing precision is improved, but the fabrication complexity increases
Solution Approach 1:
The patent applies preliminary action by pre-calculating and pre-defining the nonlinear pitch distribution pattern before fabrication. The pitch values at each location are determined in advance based on the desired angle compensation, allowing the complex geometry to be manufactured using standard photolithography and etching processes with a pre-planned pattern rather than requiring complex real-time adjustments.
Solution Approach 2:
The patent implements curvature by using a smooth, continuous nonlinear function to define the pitch variation across the grating surface. This curved, continuous pitch profile is more amenable to standard semiconductor fabrication processes compared to abrupt or discontinuous pitch changes, as it can be realized through conventional lithographic patterning and etching with appropriate mask design.
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 improves the coupling efficiency and angle of alignment tolerance, leading to enhanced performance in devices such as EAMR heads by ensuring that light is effectively coupled across a range of angles and wavelengths.
Implementation Method 1
The conventional grating couples light of the particular wavelength from the laser to a waveguide
Implementation Method 2
The design of an optical grating with a nonlinear pitch that varies based on the angle of incidence, combined with a reflective mirror for recirculating light
Data Source
AI summary
A method and system for providing an optical grating are described. The optical grating is configured for light of a wavelength. The optical grating includes a top cladding, a core, and bottom cladding. The core resides between the bottom cladding and the top cladding. The core includes a plurality of discrete ridges spaced apart by a nonlinear pitch. The light traverses the top cladding before the core and has a plurality of angles of incidence with the core. The nonlinear pitch of the core is larger for a larger angle of incidence of the plurality of angles of incidence.