Laser optical power monitoring using thermal sensor of a head transducer

Patent metadata

Field	Value
Publication number	US-9454986-B2
Application number	US-201514834140-A
Country	US
Kind code	B2
Filing date	Aug 24, 2015
Priority date	Jul 30, 2013
Publication date	Sep 27, 2016
Grant date	Sep 27, 2016

Abstract

A light source is configured to produce light, a waveguide is optically coupled to the light source and configured to direct the light to an intended focus location, and a slider is configured to use the light as an energy source for heating a region of a magnetic recording medium. A thermal sensor is situated on the slider at a location outside of a light path that includes the intended focus location. The thermal sensor is configured for sensing a short time constant change in temperature resulting from light source heating of the thermal sensor, wherein the sensed change in thermal sensor temperature is representative of optical intensity of the light delivered to the intended focus location.

First claim

What is claimed is:

1. An apparatus, comprising:
a light source configured to produce light;
a slider configured to communicate the light to a near-field transducer that uses the light as an energy source for heating a region of a magnetic recording medium;
a thermal sensor situated on the slider at a location for sensing a change in temperature resulting from direct heating of the thermal sensor by the light and from waste heat communicated from the light source to the thermal sensor, wherein the sensed change in thermal sensor temperature due to direct heating of the thermal sensor is representative of optical intensity of the light delivered by the light source;
a circuit coupled to the thermal sensor and configured to measure a change in resistance of the thermal sensor in response to the sensed change in thermal sensor temperature due to direct heating of the thermal sensor rather than from waste heat generated by the light source; and
a processor coupled to the circuit and configured to:
compare the measured change in resistance to a threshold indicating that desired light intensity is being delivered; and
produce a signal indicating whether or not the threshold has been reached.

2. The apparatus of claim 1 , wherein the change in thermal sensor resistance measured by the circuit is indicative of thermal sensor heating due to absorption of the light rather than by the waste heat.

3. The apparatus of claim 1 , wherein the circuit is configured to measure the change in resistance within about 2 milliseconds after the light source has powered on.

4. The apparatus of claim 1 , wherein the circuit is configured to measure the change in resistance within about 200 microseconds after the light source has powered on.

5. The apparatus of claim 1 , wherein the thermal sensor is situated at a location of the slider that is unexposed to the light.

6. The apparatus of claim 1 , wherein the thermal sensor is situated at a location of the slider that is exposed to the light but outside of an optical path than includes an intended focus location.

7. The apparatus of claim 1 , wherein the thermal sensor is a dedicated sensor of the slider.

8. The apparatus of claim 1 , wherein the thermal sensor is configured to perform a function different from and in addition to serving as a temperature sensor.

9. The apparatus of claim 1 , further comprising a processor coupled to the thermal sensor and configured to monitor optical intensity of the light delivered by the light source using the sensed change in thermal sensor temperature due to direct heating of the thermal sensor rather than from waste heat generated by the light source.

10. The apparatus of claim 1 , wherein:
the slider comprises an air bearing surface; and
the thermal sensor is situated at or near the air bearing surface.

11. An apparatus, comprising:
a light source configured to produce light and to modulate the light at a specified frequency;
a slider configured to communicate the light to a near-field transducer that uses the light as an energy source for heating a region of a magnetic recording medium;
a thermal sensor situated on the slider at a location for sensing a change in temperature resulting from direct heating of the thermal sensor by the light and from waste heat communicated from the light source to the thermal sensor, wherein the sensed change in thermal sensor temperature due to direct heating of the thermal sensor is representative of optical intensity of the light delivered by the light source; and
a circuit coupled to the thermal sensor and configured to measure, at the specified frequency, a change in resistance of the thermal sensor corresponding to the change in thermal sensor temperature due to direct heating of the thermal sensor rather than from waste heat generated by the light source;
wherein the circuit is configured to compare the measured change in thermal sensor resistance to a threshold indicating that desired light intensity is being delivered.

12. The apparatus of claim 11 , wherein the circuit comprises a bandpass filter having a passband that includes the specified frequency, the bandpass filter configured to output a signal representative of the change in thermal sensor resistance at the specified frequency.

13. The apparatus of claim 12 , wherein the circuit is configured to measure a peak of the output signal.

14. The apparatus of claim 11 wherein the circuit is configured to measure the change in resistance within about 2 milliseconds after the light source has powered on.

15. The apparatus of claim 11 , wherein the circuit is configured to measure the change in resistance within about 200 microseconds after the light source has powered on.

16. The apparatus of claim 11 , wherein the thermal sensor is situated at a location of the slider that is unexposed to the light.

17. The apparatus of claim 11 , wherein the thermal sensor is situated at a location of the slider that is exposed to the light but outside of an optical path than includes an intended focus location.

18. A method, comprising:
generating light by a light source situated in, at, or near a slider;
communicating the light from the light source, through the slider, and to an intended focus location of the slider; and
sensing, by a thermal sensor at the slider, a change in temperature resulting from direct heating of the thermal sensor by the light and from waste heat communicated from the light source to the thermal sensor, wherein the sensed change in thermal sensor temperature due to direct heating of the thermal sensor is representative of optical intensity of the light delivered by the light source;
measuring a change in resistance of the thermal sensor in response to the sensed change in thermal sensor temperature due to direct heating of the thermal sensor rather than from waste heat generated by the light source; and
comparing the measured change in thermal sensor resistance to a threshold indicating that desired light intensity is being delivered.

Assignees

• Seagate Technology Llc

Inventors

• Johnson Michael Thomas
• Anaya-Dufresne Manuel Charles
• Jandric Zoran

Classifications

• G11B5/455

  Arrangements for functional testing of heads; Measuring arrangements for heads · CPC title

• G11B13/08

  using near-field interactions or transducing means and at least one other method or means for recording or reproducing · CPC title

• G11B5/02 Primary

  Recording, reproducing, or erasing methods; Read, write or erase circuits therefor · CPC title

• G11B5/40

  Protective measures on heads, e.g. against excessive temperature  (G11B5/31 takes precedence; protection against wear G11B5/255  {; protective structure of the head: see under structures, e.g. G11B5/3106}) · CPC title

• G11B5/3136

  for reducing the pole-tip-protrusion at the head transducing surface, e.g. caused by thermal expansion of dissimilar materials · CPC title