Bolometric Sensor Pad Sharing for HAMR Laser Monitoring
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Solution Overview
Problem
Conventional laser power monitoring in heat-assisted magnetic recording (HAMR) systems is inadequate for integrated transducers due to the need for external photodiodes, which are not feasible in reduced submount dimensions, leading to mode hopping and instability issues.
Innovation Solution
A bolometric sensor arrangement within the slider, comprising a bolometer and a reference thermal sensor, shares electrical bond pads with contact sensors to monitor laser output optical power without additional bond pads, compensating for thermal background noise and providing improved signal-to-noise ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If external photodiodes are used for laser power monitoring, then laser output power can be monitored, but additional electrical bond pads are required which are not feasible in reduced submount dimensions
Solution Approach 1:
The patent combines the laser power monitoring function with existing electrical bond pads by integrating a bolometric sensor arrangement that shares the same bond pads as contact sensors. This merging eliminates the need for additional bond pads while maintaining monitoring capability.
Solution Approach 2:
The electrical bond pads are designed to serve multiple functions: they provide electrical connections for contact sensors and simultaneously serve as connection points for the bolometric sensor arrangement, enabling laser power monitoring without requiring dedicated additional pads.
2Reliability
If conventional laser power monitoring is used, then external photodiodes can monitor power, but mode hopping and instability issues occur in integrated transducers
Solution Approach 1:
The patent introduces a bolometric sensor arrangement as an intermediary element within the slider that indirectly monitors laser power by detecting thermal effects, avoiding the direct optical detection that causes mode hopping while maintaining monitoring precision through temperature-based measurement.
Solution Approach 2:
The patent replaces the optical detection mechanism (external photodiodes) with a thermal detection mechanism (bolometric sensor), substituting the optical system with a thermal system that does not induce mode hopping while providing stable and precise laser power monitoring.
3Adaptability or versatility
If additional electrical bond pads are added for sensor connections, then more sensors can be connected, but the submount dimensions become too large
Solution Approach 1:
The patent merges the electrical connection functions by having the bolometric sensor arrangement share the same bond pads as the contact sensors, thereby maintaining full sensor connectivity without increasing the number of bond pads or submount area.
4Measurement precision
If thermal background noise is present, then measurement accuracy decreases, but signal-to-noise ratio can be improved with proper sensor arrangement
Solution Approach 1:
The patent extracts the thermal background noise component from the measurement by using a differential configuration where the bolometric sensor measures total temperature (laser heating + background) and this background component is separated out through circuit arrangement, leaving only the laser-induced signal.
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 internal sensor arrangement effectively monitors laser output power fluctuations, reducing mode hopping and ensuring stable operation by eliminating the need for extra electrical bond pads, thus enhancing the reliability of HAMR systems.
Implementation Method 1
A bolometer is situated at a location within the slider that receives at least some of the light communicated along the waveguide
Implementation Method 2
The reference thermal sensor is situated at a location within the slider unexposed to the light communicated along the waveguide
Implementation Method 3
A contact sensor at or near the air bearing surface is coupled between a first bond pad and a second bond pad
Data Source
AI summary
A slider of a heat-assisted recording head comprises electrical bond pads coupled to bias sources and a ground pad, an air bearing surface, and a waveguide configured to receive light from a laser source. A contact sensor proximate the air bearing surface is coupled between a first bond pad and a second bond pad. A bolometer is coupled to a reference thermal sensor. The bolometer is situated at a slider location that receives at least some of the light communicated along the waveguide. The reference thermal sensor is situated at a slider location unexposed to the light communicated along the waveguide. The bolometer and reference thermal sensor are coupled between the first and second bond pads and in parallel with the contact sensor. A ground connection is coupled to the ground pad and at a connection between the bolometer and the reference thermal sensor.