Surface-Emitting Laser Diode for Thermal-Assisted Magnetic Recording
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Solution Overview
Problem
Conventional thermally-assisted magnetic recording heads face challenges in achieving sufficient light power and precise beam spot size due to the limitations of vertical-cavity surface-emitting lasers, which result in inadequate output power and inefficient beam delivery to the magnetic recording medium.
Innovation Solution
A thermally-assisted magnetic recording head is designed with a surface-emitting type light source, incorporating a first and second diffraction optical element, a waveguide, and an optical-path direction conversion element to efficiently guide a collimated beam to the recording medium, utilizing a photonic-crystal type surface-emitting laser diode with high output power and a plasmon antenna for near-field light generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a VCSEL is used as the light source in a thermally-assisted magnetic recording head, then the device complexity is reduced and ease of manufacture is improved, but the output power is insufficient and beam delivery efficiency is poor
Solution Approach 1:
The patent changes the fundamental parameters of the light source by transitioning from a VCSEL with vertical cavity structure to a surface-emitting laser diode with horizontal cavity structure. This parameter change enables the light source to achieve sufficient output power (several mW to tens of mW) while maintaining ease of integration into the head structure. The surface-emitting configuration allows for better beam coupling with the optical system components.
Solution Approach 2:
The patent transitions from vertical beam emission (VCSEL) to horizontal/surface emission geometry. This dimensional change in beam propagation direction enables more efficient coupling with the diffraction grating and waveguide structures, improving overall beam delivery efficiency while maintaining manufacturing feasibility.
2Device complexity
If a VCSEL is used as the light source, then the device structure is simplified, but the beam spot size control and delivery efficiency to the recording medium deteriorate
Solution Approach 1:
The patent introduces a diffraction grating as an intermediary optical element between the surface-emitting laser diode and the waveguide. This diffraction grating serves as a mediator that shapes and directs the laser beam, enabling precise control of beam spot size at the recording medium while maintaining relatively simple device structure. The grating converts the laser output into the desired beam profile for high-precision recording.
3Stability of the object's composition
If the anisotropic magnetic field of the recording medium is increased to improve thermal stability, then the thermal stability is improved, but the write capability of the head deteriorates
Solution Approach 1:
The patent utilizes thermal phase transition (heating) of the magnetic recording medium to temporarily reduce its anisotropic magnetic field during the writing process. By applying laser heating, the medium transitions from a high-coercivity state (good for stability) to a low-coercivity state (easy to write), enabling data writing even when thermal stability requires high Ku values. This resolves the contradiction by dynamically changing the magnetic properties during operation.
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 enables the efficient delivery of high-powered laser beams with a small spot diameter, improving recording density and thermal stability by effectively reducing the anisotropic magnetic field, thus enabling reliable data writing on the magnetic recording medium.
Implementation Method 1
a magnetic recording medium is irradiated with beam from a plane-emission or surface-emitting type light source, thereby anisotropic magnetic field of the medium is lowered
Implementation Method 2
a magnetic recording medium formed of a magnetic material with a large energy Ku is used so as to stabilize the magnetization, then anisotropic magnetic field of a portion of the medium, where data is to be written, is reduced by heating the portion
Implementation Method 3
a first diffraction optical element for focusing the substantially collimated beam emitted from the surface-emitting type light source
Implementation Method 4
a waveguide integrally formed with the second diffraction optical element and made of the material as that of second diffraction optical element, the light beam collimated by the second diffraction optical element being incident to the waveguide
Implementation Method 5
an optical-path direction conversion element for converting a direction of an optical path of the incident light beam to a propagation direction of the waveguide
Implementation Method 6
utilizing a photonic-crystal type surface-emitting laser diode with high output power and a plasmon antenna for near-field light generation
Data Source
AI summary
A thermally-assisted magnetic recording head includes a surface-emitting type light source for emitting substantially collimated beam, a first diffraction optical element for focusing the substantially collimated beam emitted from the surface-emitting type light source, a second diffraction optical element for collimating the light beam focused by the first diffraction optical element, a waveguide integrally formed with the second diffraction optical element and made of the material as that of second diffraction optical element, the light beam collimated by the second diffraction optical element being incident to the waveguide, an optical-path direction conversion element for converting a direction of an optical path of the incident light beam to a propagation direction of the waveguide, the propagation direction being toward an opposed-to-medium surface, and a magnetic pole for generating write field from its end face on the opposed-to-medium surface side.