Optical Waveguide Grating for Perpendicular Laser Coupling
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Solution Overview
Problem
Current thermally-assisted magnetic recording methods face challenges in efficiently coupling laser light with optical waveguides, leading to suboptimal propagation directions and installation complexities due to the use of dual gratings and non-perpendicular light incidence, which affects the coupling efficiency with surface plasmons.
Innovation Solution
An optical waveguide design featuring a core with a wide base, taper, and narrow front end, where a grating with concave grooves is engraved on the wide base part for perpendicular light incidence, ensuring efficient coupling by matching the groove depth and pitch to the wavelength, and a reflective film is used to facilitate targeted light propagation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a dual grating configuration with non-perpendicular light incidence is used, then light coupling with the waveguide is achieved, but coupling efficiency with surface plasmons deteriorates and installation complexity increases
Solution Approach 1:
The patent inverts the conventional approach by using a single grating with perpendicular light incidence instead of dual gratings with non-perpendicular incidence. This inversion simplifies the installation by positioning the laser light generating device directly opposite the grating, while maintaining effective coupling with surface plasmons through the optimized grating geometry and perpendicular incidence angle.
Solution Approach 2:
The patent changes the critical parameter of light incidence angle from non-perpendicular to perpendicular, and adjusts the grating parameters (pitch and groove depth) to optimize coupling efficiency. This parameter optimization enables reliable coupling with surface plasmons while simplifying the overall device installation and alignment requirements.
2Reliability
If non-perpendicular light incidence is used, then light coupling with the waveguide is achieved, but coupling efficiency with surface plasmons deteriorates
Solution Approach 1:
The patent optimizes the light incidence angle parameter to perpendicular incidence, which maximizes the coupling efficiency with surface plasmons. Additionally, the grating pitch and groove depth parameters are carefully selected to match the wavelength and material properties, ensuring efficient energy transfer from the laser light to the surface plasmons while maintaining reliable waveguide coupling.
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 allows reliable optical coupling of laser light with the waveguide, simplifying the installation of the laser light generating device and ensuring targeted light propagation, enhancing the efficiency of thermally-assisted magnetic recording by improving light coupling and propagation.
Implementation Method 1
a grating is provided on one of planar surfaces of the wide core base part, the grating is formed by engraving a number of concave grooves having a rectangular cross section on the planar surface along a width direction thereof, the grating is formed to be optically coupled with laser light that is incident perpendicularly onto the grating formation surface
Implementation Method 2
a core that is a waveguide through which light propagates; and a cladding that surrounds the core
Implementation Method 3
a reflective film is used to facilitate targeted light propagation
Implementation Method 4
for performing the thermally-assisted recording by the irradiation of the near-field light with a magnetic recording head
Data Source
AI summary
An optical waveguide of the invention includes a core that is a waveguide through which light propagates; and a cladding that surrounds the core. The core has a plate shape and includes a wide core base part onto which the light is incident, a taper part that is connected to the core base part and of which a width is gradually tapered along a propagation direction, and a narrow front end core part that is connected to the taper part and that extends along the propagation direction. A grating is provided on one of planar surfaces of the wide core base part, the grating is formed by engraving a number of concave grooves having a rectangular cross section on the planar surface along a width direction thereof, the grating is formed to be optically coupled with laser light that is incident perpendicularly onto the grating formation surface, a frequency (grating pitch: pitch of the concave grooves) of the grating is smaller than a wavelength (defined as a wavelength in the cladding) of the perpendicularly incident laser light, and a groove depth H1 of the grating is formed with respect to a thickness H2 of the core base part so that a relationship H1=(0.33 to 0.67)×H2 is satisfied.