Ridge Waveguide Coupler for Longitudinal Near Field Transducer Mode Matching
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Solution Overview
Problem
Heat assisted magnetic recording technologies face challenges in efficiently delivering confined optical energy to metallic data storage media due to incompatibility between channel waveguide modes and longitudinal near field transducers, which limits the scalability of recording density.
Innovation Solution
The use of a ridge waveguide with a coupler that includes a lightning rod structure, where the coupler has segments of varying widths and a protrusion extending beyond the waveguide's bottom surface, facilitates efficient mode matching between the channel waveguide and ridge waveguide, enhancing the longitudinal electric field and enabling the concentration of optical energy into a small spot.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a channel waveguide is used to deliver optical energy, then the device structure is simple, but the dominant electric field component is transverse to the direction of propagation which is incompatible with longitudinal near field transducers
Solution Approach 1:
An intermediary structure (the coupler with opening and protrusion) is introduced between the channel waveguide and the longitudinal NFT. This intermediary transforms the transverse electric field of the channel waveguide into a longitudinal electric field that can excite the longitudinal NFT, thereby resolving the incompatibility while keeping both original components relatively simple.
2Quantity of substance
If the area of the confined region is scaled down to increase recording density, then areal density increases, but the efficiency of optical energy confinement and delivery becomes more difficult to maintain
Solution Approach 1:
The invention changes the geometric parameters of the waveguide structure (introducing a coupler with specific opening dimensions and a protrusion) to transform the field distribution. This allows efficient optical energy confinement to be maintained even as the confined region area is scaled down, enabling high areal density recording while preserving optical delivery efficiency.
3Adaptability or versatility
If a coupler with varying width segments and protrusion is introduced to enable mode matching, then compatibility between waveguide modes and longitudinal NFT is achieved, but device complexity increases
Solution Approach 1:
The coupler is segmented into different width sections (first segment with first width, second segment with second width) plus a protrusion. This segmentation allows progressive mode transformation from the channel waveguide mode to the longitudinal NFT mode, achieving effective coupling while keeping each individual segment relatively simple in structure.
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 for the generation of a high-efficiency confined optical spot on a recording medium, improving the scalability of data storage devices and enhancing thermal stability of recorded information.
Implementation Method 1
a coupler between the channel waveguide and the ridge waveguide, the coupler including an opening configured to transmit light from the channel waveguide to the ridge waveguide
Implementation Method 2
the near field transducers can be broadly classified as longitudinal (i.e., polarization normal to the medium) or transverse type (i.e., polarization transverse to the medium). Longitudinal NFT's show promise in terms of efficiently scaling down the area of the confined region
Implementation Method 3
a protrusion extending from the ridge beyond the plane of the bottom surface
Data Source
AI summary
An apparatus includes a channel waveguide, a ridge waveguide including a ridge and having a bottom surface, a coupler between the channel waveguide and the ridge waveguide, the coupler including an opening configured to transmit light from the channel waveguide to the ridge waveguide, wherein the opening has a first segment having a first width and a second segment having a second width different from the first width, and a protrusion extending from the ridge beyond the plane of the bottom surface.