Extended Cavity VCSEL for TAR Head Laser Power
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Solution Overview
Problem
Current thermally-assisted recording (TAR) disk drives face challenges in integrating a laser with the head carrier to effectively direct laser light to the optical waveguide, with typical vertical-cavity surface-emitting lasers (VCSELs) not providing adequate power output.
Innovation Solution
The integration of an extended cavity VCSEL with the head carrier, where the semiconductor substrate serves as the extended cavity, allowing for higher single mode power output, and the TAR head is fabricated on the outer surface of the VCSEL with a grating coupler and near-field transducer to direct laser radiation to the optical waveguide.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a typical VCSEL is used for TAR, then the device complexity is reduced and cost is lowered, but the power output is insufficient for effective heating
Solution Approach 1:
The VCSEL structure is segmented into multiple functional layers including the semiconductor substrate, distributed Bragg reflectors (DBR), and extended cavity region. This segmentation allows each layer to be optimized independently for its specific function while collectively achieving the desired high power output
Solution Approach 2:
The invention transitions from a standard two-mirror VCSEL configuration to an extended cavity design that utilizes the third dimension (vertical depth) by extending the cavity through the semiconductor substrate. This dimensional extension enables higher power output by allowing more round trips of photons within the cavity
2Power
If the semiconductor substrate thickness is increased to form an extended cavity, then the laser power output increases, but the manufacturing precision requirements increase
Solution Approach 1:
The invention changes the critical parameter from precise thickness control to controlled etching depth. By using etching processes to define the extended cavity depth rather than relying solely on substrate thickness variations, the manufacturing process becomes more controllable and repeatable
Solution Approach 2:
The invention replaces mechanical thickness control methods with chemical etching processes to define the extended cavity depth. This substitution allows for more precise and consistent depth control through chemical means rather than mechanical machining or bonding
3Device complexity
If the VCSEL is integrated directly with the head carrier, then the device complexity is reduced, but the alignment precision of laser light to the optical waveguide becomes more difficult
Solution Approach 1:
The VCSEL is merged directly with the head carrier by forming the extended cavity within the head carrier substrate itself. This integration eliminates separate mounting steps and reduces the number of components, while the grating coupler provides built-in alignment functionality
Solution Approach 2:
The grating coupler acts as an intermediary element that mediates the coupling between the VCSEL output and the optical waveguide. It provides a robust alignment mechanism that is less sensitive to manufacturing variations, effectively bridging the gap between the laser source and the waveguide input
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 enhances the power output of the laser radiation, enabling more effective heating of the magnetic recording layer for writing data, while maintaining the integration of a magnetoresistive read head and write head, thus improving data recording capabilities.
Implementation Method 1
A VCSEL is formed on the semiconductor substrate front surface... The laser radiation is output through a partially reflecting output mirror through the front surface
Implementation Method 2
the grating coupler, which turns the incoming laser radiation 90 degrees and directs it into the waveguide
Implementation Method 3
an optical waveguide with a grating coupler and a NFT located at the ABS... from where it is directed to the NFT at the ABS
Implementation Method 4
an optical waveguide with a near-field transducer (NFT) directs radiation from a laser to heat localized regions of the magnetic recording layer on the disk. The radiation heats the magnetic material locally to near or above its Curie temperature
Implementation Method 5
The recorded data is read back by a conventional magnetoresistive read head
Data Source
AI summary
A thermally-assisted recording (TAR) head structure has a semiconductor substrate as the head carrier with a vertical-cavity surface-emitting laser (VCSEL) on its front surface, a TAR head formed directly on the VCSEL, and a highly reflecting third mirror on its back surface. The semiconductor substrate serves as an extended cavity for the VCSEL. The TAR head is fabricated on the outer surface of the VCSEL in the same manner as proposed for fabrication of a TAR head on a conventional slider. The TAR head includes a conventional read head and write head, and an optical waveguide with a grating coupler and a near-field transducer (NFT). The laser radiation is output through a partially reflecting output mirror of the VCSEL through the front surface to the grating coupler, which turns the incoming laser radiation 90 degrees and directs it into the waveguide from where it is directed to the NFT.