VCSEL Array for HAMR Write Head

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Solution Overview

Problem

Current heat-assisted magnetic recording (HAMR) technologies face challenges with edge emitting laser diodes (EELDs), including high costs, mode-hops, limited alignment tolerance, reliability issues, and increased disk-to-disk spacing, which hinder the achievement of high recording densities.

Innovation Solution

The use of a vertical cavity surface emitting laser (VCSEL) mounted on a slider, emitting phase-coherent laser beams through waveguide structures and a multimode interference (MMI) device to focus on a near-field transducer (NFT), eliminating the need for a sub-mount and reducing the overall size and height of the HAMR write head.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If edge emitting laser diode (EELD) is used as light source, then laser heating function is achieved, but cost increases and reliability decreases

Engineering Contradiction:

Improvelaser source reliabilityVSAvoidmanufacturing cost

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent replaces expensive EELD with VCSEL which eliminates the need for sub-mount assembly and burn-in testing, reducing manufacturing cost and improving reliability through simpler integration

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

Solution Approach 2:

The patent extracts and eliminates the sub-mount component from the laser assembly, directly mounting the VCSEL to the slider to reduce cost and improve reliability

Inventive Principle:

Principle #2Taking out (Extraction)

2Productivity

If EELD is used as light source, then laser heating function is achieved, but mode-hops occur reducing HAMR HDD capacity

Engineering Contradiction:

ImproveHAMR HDD capacityVSAvoidlaser mode stability

Core Design Contradiction:

ProductivityVSStability of the object's composition

Solution Approach 1:

The patent changes the laser operating parameters by using VCSEL which operates at a single longitudinal mode without mode-hops, ensuring stable laser power and frequency for consistent HAMR performance

Inventive Principle:

Principle #35Parameter changes

3Ease of operation

If EELD is used as light source, then laser heating function is achieved, but alignment tolerance is reduced

Engineering Contradiction:

Improvealignment toleranceVSAvoidbeam diameter

Core Design Contradiction:

Ease of operationVSLength of moving object

Solution Approach 1:

The patent transitions from edge-emitting to surface-emitting laser geometry, changing the emission dimension from lateral to vertical, which provides larger beam diameter and improved alignment tolerance

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

4Ease of operation

If VCSEL is mounted on slider, then alignment tolerance is improved, but device structure becomes more complex

Engineering Contradiction:

Improvealignment toleranceVSAvoidwaveguide structure

Core Design Contradiction:

Ease of operationVSDevice complexity

Solution Approach 1:

The patent introduces waveguide structures as intermediaries to channel and focus the laser light from VCSEL to the NFT, managing the complexity through structured optical pathways

Inventive Principle:

Principle #24Intermediary (Mediator)

5Ease of manufacture

If sub-mount is used for EELD, then laser mounting is achieved, but cost increases and profile increases

Engineering Contradiction:

Improvelaser mountingVSAvoidassembly structure

Core Design Contradiction:

Ease of manufactureVSDevice complexity

Solution Approach 1:

The patent extracts and eliminates the sub-mount component from the assembly, directly mounting the VCSEL to the slider, thereby reducing cost, profile height, and structural complexity

Inventive Principle:

Principle #2Taking out (Extraction)

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 solution reduces costs, enhances alignment tolerance, improves reliability, and increases HDD capacity by providing stable, high-power single-mode laser output for efficient heat concentration, thereby improving recording density.

Implementation Method 1

A vertical cavity surface emitting laser (VCSEL) is mounted to a top surface of a slider. A plurality of laser beams are emitted from a bottom surface of the VCSEL

Methodology Applied

Scientific EffectLaser: Laser

Implementation Method 2

The waveguide structures feed into a multimode interference (MMI) device that then directs the laser into a single waveguide for focusing on a near field transducer (NFT)

Methodology Applied

Scientific EffectOptical focusing: Focusing

Implementation Method 3

a laser source exciting a near-field transducer (NFT) to produce heat at a write location of a magnetic recording medium

Methodology Applied

Scientific EffectNear-field transducer heat generation:

Data Source

PatentUS11651786B2VCSEL array for HAMR

Publication Date: 2023.05.16 WESTERN DIGITAL TECHNOLOGIES INC

AI summary

The present disclosure relates to pretreating a magnetic recording head for magnetic media drive. For a heat assisted magnetic recording (HAMR) head, a light source provides the necessary heat for the drive to operation. A vertical cavity surface emitting laser (VCSEL) is mounted to a top surface of a slider. A plurality of laser beams are emitted from the bottom surface of the VCSEL and directed to a corresponding number of waveguide structures within the HAMR head. The waveguide structures feed into a multimode interference (MMI) device that then directs the laser into a single waveguide for focusing on a near field transducer (NFT). The VCSEL lasers are phase coherent and have no mode hopping.