Method for compensating for phase variations in an interferometric tapered waveguide in a heat assisted magnetic recording head

• US 9,286,920 B1
• Filed: 01/31/2013
• Issued: 03/15/2016
• Est. Priority Date: 01/31/2013
• Status: Active Grant

• Current Assignee: JP Morgan Chase Bank, N.A. (JP Morgan Chase & Co)
• Original Assignee: Western Digital Corporation
• Inventors: Hu, Yufeng, Tran, Ut
• Primary Examiner(s): Pendleton, Dionne H
• Application Number:
  US13/756,379
• Time in Patent Office: 1,139 Days
• US Class Current: 1/1
• CPC Class Codes: G02B 6/122 Basic optical elements, e.g. light-guiding paths
• CPC Class Codes: G02B 6/1228 Tapered waveguides, e.g. integrated spot-size transformers for coupling with fibres G02B6/305
• CPC Class Codes: G02B 6/125 Bends, branchings or intersections
• CPC Class Codes: G11B 2005/0021 Thermally assisted recording using an auxiliary energy source for heating the recording layer locally to assist the magnetization reversal
• CPC Class Codes: G11B 5/314 where the layers are extra layers normally not provided in the transducing structure, e.g. optical layers G11B5/3196 takes precedence
• CPC Class Codes: G11B 5/3163 Fabrication methods or processes specially adapted for a particular head structure, e.g. using base layers for electroplating, using functional layers for masking, using energy or particle beams for shaping the structure or modifying the properties of the basic layers
• CPC Class Codes: G11B 5/6088 Optical waveguide in or on flying head
• CPC Class Codes: G11B 7/1384 Fibre optics

Abstract

A method fabricates an interferometric tapered waveguide (ITWG) for a heat-assisted magnetic recording (HAMR) transducer. The ITWG is defined from at least one waveguide layer. The waveguide layer(s) include an energy sensitive core layer. The energy sensitive core layer has an index of refraction that varies in response to exposure to energy having a particular wavelength range. The step of defining the ITWG includes defining a plurality of arms for the ITWG. At least one phase difference between the arms is determined. At least one of the arms is exposed to the energy such that the index of refraction of the energy sensitive core layer in the arm(s) is changed and such that the phase difference(s) between the arms is changed.

Claims

1. A method for providing an interferometric tapered waveguide (ITWG) for a heat-assisted magnetic recording (HAMR) transducer comprising:

defining the ITWG from at least one waveguide layer, the at least one waveguide layer including an energy sensitive core layer, the energy sensitive core layer having an index of refraction that varies in response to exposure to energy having a particular wavelength range, the step of defining the ITWG including defining a plurality of arms for the ITWG;

determining at least one phase difference between the plurality of arms; and

exposing at least one of the plurality of arms to the energy after the determining step such that the index of refraction of the energy sensitive core layer in the at least one of the plurality of arms is changed and such that the at least one phase difference between the plurality of arms is changed to at least one new phase difference, the at least one new phase difference being substantially constant during operation of the HAMR transducer and in-operation of the HAMR transducer, wherein the HAMR transducer is one of a plurality of HAMR transducers on a wafer and wherein the step of exposing the at least one of the plurality of arms to the energy is performed on a wafer level for the entire wafer.

2. The method of claim 1 further comprising:

providing the at least one waveguide layer.

3. The method of claim 1 further comprising:

providing a mask on the ITWG, the mask being opaque to the energy and including an aperture therein, the aperture exposing a portion of the at least one of the plurality of arms, covering a remaining portion of the at least one of the plurality of arms, and covering any remaining arms of the plurality of arms.

4. The method of claim 3 wherein the at least one waveguide layer includes a top cladding layer, step of providing the mask further including:

providing the mask on the top cladding layer.

5. The method of claim 4 wherein the HAMR transducer further includes an overcoat layer, the mask residing between the overcoat layer and the top cladding layer.

6. The method of claim 4 wherein the HAMR transducer further includes an overcoat layer, the overcoat layer residing between the mask and the top cladding layer.

7. The method of claim 1 wherein the step of exposing the at least one of the plurality of arms is performed on a device level.

8. The method of claim 1 wherein the ITWG has at least one target phase difference, the at least one target phase difference being constant, the at least one new phase difference being closer to the at least one target phase difference than the at least one phase difference.

9. The method of claim 1 wherein the HAMR transducer further includes at least one grating corresponding to at least a portion of the plurality of arms, the at least one grating contributing to the phase difference.

10. The method of claim 9 wherein the step of exposing the at least one of the plurality of arms further includes:

exposing at least a portion of the least one grating to the energy.

11. The method of claim 1 wherein the HAMR transducer further includes at least one trench corresponding to at least a portion of the plurality of arms, the at least one trench contributing to the phase difference.

12. The method of claim 11 wherein the step of exposing the at least one of the plurality of arms further includes:

exposing at least a portion of the at least one trench to the energy.

13. A method for providing an interferometric tapered waveguide (ITWG) for a heat-assisted magnetic recording (HAMR) transducer comprising:

defining the ITWG from at least one waveguide layer, the at least one waveguide layer including an energy sensitive core layer, the energy sensitive core layer having an index of refraction that varies in response to exposure to energy having a particular wavelength range, the step of defining the ITWG including defining a plurality of arms for the ITWG;

determining at least one phase difference between the plurality of arms; and

exposing at least one of the plurality of arms to the energy after the determining step such that the index of refraction of the energy sensitive core layer in the at least one of the plurality of arms is changed and such that the at least one phase difference between the plurality of arms is changed to at least one new phase difference, the at least one new phase difference being substantially constant during operation of the HAMR transducer and in-operation of the HAMR transducer;

wherein the plurality of arms have a target phase difference, the target phase difference corresponding to a target optical length for one of the plurality of arms, and wherein the step of defining the ITWG further includes;

defining the one of the plurality of arms to have an optical length greater than the target optical length such that the at least one phase difference is greater than the target phase difference; and

wherein the index of refraction of the energy sensitive core layer is reduced by exposure to the energy.

14. A method for providing an interferometric tapered waveguide (ITWG) for a heat-assisted magnetic recording (HAMR) transducer comprising:

defining the ITWG from at least one waveguide layer, the at least one waveguide layer including an enemy sensitive core layer, the energy sensitive core layer having an index of refraction that varies in response to exposure to energy having a particular wavelength range, the step of defining the ITWG including defining a plurality of arms for the ITWG;

determining at least one phase difference between the plurality of arms; and

exposing at least one of the plurality of arms to the enemy after the determining step such that the index of refraction of the energy sensitive core layer in the at least one of the plurality of arms is changed and such that the at least one phase difference between the plurality of arms is changed to at least one new phase difference, the at least one new phase difference being substantially constant during operation of the HAMR transducer and in-operation of the HAMR transducer;

wherein the plurality of arms have a target phase difference, the target phase difference corresponding to a target optical length for one of the plurality of arms, and wherein the step of defining the ITWG further includes;

defining the one of the plurality of arms to have an optical length less than the target optical length such that the at least one phase difference is less than the target phase difference; and

wherein the index of refraction of the energy sensitive core layer is increased by exposure to the energy.

15. A method for providing an interferometric tapered waveguide (ITWG) for an energy-assisted magnetic recording (HAMR) transducer, the method comprising:

providing a bottom cladding layer;

providing an energy sensitive core layer on the bottom cladding layer, the energy sensitive core layer having an index of refraction that decreases in response to exposure to energy having a particular wavelength range;

providing a top cladding layer on the energy sensitive core layer;

defining the ITWG including defining a plurality of arms for the ITWG, the ITWG having a target phase difference, the target phase difference corresponding to a target optical length for an arm of the plurality of arms, the arm of the plurality of arms having a longer optical length greater than the optical length such that the phase difference is greater than the target phase difference;

providing a mask on the plurality of arms, the mask being opaque to the energy and including an aperture therein, the aperture exposing a portion of the arm, covering a remaining portion of the arm, and covering any remaining arms of the plurality of arms;

determining at least one phase difference between the arm and the any remaining arms; and

exposing the portion of the arm to the energy after the determining step such that the index of refraction of the energy sensitive core layer in the portion of the arm is reduced and such that the least one phase difference between the arm and the any remaining arms is changed to at least one new phase difference, the at least one new phase difference being substantially constant during operation of the HAMR transducer and in-operation of the HAMR transducer.

16. The method of claim 15 wherein the HAMR transducer further includes an overcoat layer, the mask residing between the overcoat layer and the top cladding layer.

17. The method of claim 15 wherein the HAMR transducer further includes an overcoat layer, the overcoat layer residing between the mask and the top cladding layer.

18. The method of claim 15 wherein the ITWG has at least one target phase difference, the at least one target phase difference being constant, the at least one new phase difference being closer to the at least one target phase difference than the at least one phase difference.