Internal Bolometer for Laser Power Monitoring in HAMR
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Solution Overview
Problem
Conventional laser power monitoring in heat-assisted magnetic recording (HAMR) systems is inadequate due to mode hopping caused by temperature variations, which leads to laser output power instability and data errors, and external photodiodes are not feasible in integrated transducers due to space constraints and added complexity.
Innovation Solution
An internal bolometric sensor is integrated within the slider, positioned near the optical waveguide to absorb light and generate a signal indicative of laser output power fluctuations, sharing electrical bond pads with existing components to minimize additional complexity and maintain waveguide efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an external photodiode is used for laser power monitoring, then laser output power can be monitored, but the device complexity increases and space constraints are violated
Solution Approach 1:
The bolometric sensor is integrated within the slider body, merging the laser power monitoring function with the existing transducer structure. This eliminates the need for external photodiodes and reduces device complexity while maintaining monitoring capability
Solution Approach 2:
The internal bolometric sensor serves multiple functions: it monitors laser power fluctuations and also benefits from the same electrical biasing infrastructure already present for the reader, making the monitoring system universal to the existing transducer operations
2Device complexity
If an internal bolometric sensor is integrated within the slider, then device complexity is reduced and space constraints are satisfied, but the sensor may impact waveguide efficiency
Solution Approach 1:
The bolometric sensor is positioned at a specific location within the slider body that allows it to detect laser power fluctuations without being in the direct path of the optical waveguide, thus maintaining waveguide efficiency while enabling monitoring functionality
Solution Approach 2:
The sensor detects laser power fluctuations through thermal effects from scattered or leaked light rather than direct beam interception, acting as an intermediary that monitors power without significantly impacting the main optical path
3Quantity of substance
If the bolometer shares electrical bond pads with the reader, then the quantity of substance (bond pads) is reduced, but the ease of operation may be affected during read operations
Solution Approach 1:
The system operates in periodic cycles where the bolometer is activated during write operations for power monitoring and remains inactive or is electrically isolated during read operations, allowing shared bond pads to serve both functions without interference
Solution Approach 2:
The electrical connection to the shared bond pads is dynamically controlled, being enabled for the bolometer during write operations and disabled or redirected to the reader during read operations, ensuring proper operation in each mode
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
The internal bolometric sensor effectively monitors laser power fluctuations without impacting waveguide efficiency, reducing the risk of mode hopping and ensuring stable laser output, thus enhancing data integrity and reducing the need for additional bond pads.
Implementation Method 1
A bolometer is situated proximal of the write pole at a location within the internal body of the slider that receives at least some of the light communicated along the waveguide
Implementation Method 2
The bolometer is electrically coupled to bond pads, such as the reader bond pads, for biasing the bolometer, and configured to generate a signal indicative of output optical power of the laser source
Data Source
AI summary
An apparatus comprises a slider having an air-bearing surface (ABS), a write pole at or near the ABS, and a reader at or near the ABS and connected to a pair of reader bond pads of the slider. A near-field transducer (NFT) is formed on the slider at or near the ABS, and an optical waveguide is formed in the slider and configured to receive light from a laser source. A sensor is situated proximal of the write pole at a location within the slider that receives at least some of the light communicated along the waveguide. The sensor may be electrically coupled to the reader bond pads in parallel with the reader, and configured to generate a signal indicative of output optical power of the laser source.