Waveguide having mode converter for heat-assisted magnetic recording device

1. A write head comprising:

a waveguide core configured to receive light emitted in a crosstrack direction from a light source at a fundamental transverse electric (TE 00 ) mode, the waveguide core comprising:

a first turn that receives the light in the crosstrack direction from the light source and redirects the light to an opposite crosstrack direction;

a second turn, positioned closer to a media-facing surface than the first turn, that redirects the light from the opposite crosstrack direction to a direction normal to the media-facing surface of the write head;

a straight section coupling the first and second turns; and

a branched portion extending from the straight section and configured to convert the light to a higher-order (TE 10 ) mode; and

a near-field transducer at the media-facing surface, the near-field transducer receiving the light at the TE 10 mode from the waveguide and directing surface plasmons to a recording medium in response thereto, the second turn configured to deliver the light to the near-field transducer at the direction normal to the media-facing surface.

2. The write head of claim 1 , wherein the first turn comprises first and second mirror image Euler spiral sections.

3. The write head of claim 2 , wherein the second turn comprises third and fourth Euler spiral sections.

4. The write head of claim 1 , wherein the straight section tapers from a first cross-sectional width at the first turn to a second cross-sectional width at the second turn, the first cross-sectional width being less than the second cross-sectional width.

5. The write head of claim 1 , wherein the branched portion is separated from at least part of the straight section via a gap having a constant cross-sectional width for a predetermined length.

6. The write head of claim 5 , wherein the predetermined length is in a range of about 5 μm to about 6 μm.

7. The write head of claim 5 , wherein the gap has a variable cross-sectional width.

8. The write head of claim 5 , wherein at least a portion of the gap has a linear taper.

9. The write head of claim 5 , wherein the straight section and the branched portion combine to form a combined width of about 1.14 μm.

10. The write head of claim 9 , wherein one or both of the straight section and the branched portion has a taper to accommodate the difference in the combined width.

11. The write head of claim 10 , wherein the taper has a length of about 23 μm.

12. The write head of claim 1 , wherein the branched portion has an offset from a centerline of about −0.3 μm.

13. The write head of claim 1 , wherein the branched portion tapers from a narrower width proximate the middle section to a wider width away from the straight section.

14. The write head of claim 1 , wherein the light source comprises an active region formed of a non-self supporting, crystalline layer transfer printed to a substrate of the write head.

15. A system, comprising:

a light source comprising an active region formed of a non-self supporting, crystalline layer transfer printed to a substrate;

an input coupler configured to receive light excited by the light source;

a waveguide core extending along a light-propagation direction and configured to receive light from the light source at a fundamental transverse electric (TE 00 ) mode, the waveguide core comprising:

a main portion having a curvature that changes linearly with curve length and configured to receive light at an input, and

a branched portion extending from a middle region of the main portion; and

a near-field transducer at a media-facing surface of the write head, the near-field transducer receiving the light at a TE 10 mode from the waveguide and directing surface plasmons to a recording medium in response thereto, the main portion configured to deliver the light to the near-field transducer at a direction normal to the media-facing surface.

16. The system of claim 15 , further comprising a mode converter that converts the light to the TE 10 mode.

17. The system of claim 15 , wherein the middle region tapers from a first cross-sectional width to a second cross-sectional width along the light propagation direction, the first cross-sectional width being greater than the second cross-sectional width.

18. The system of claim 15 , wherein the branch of the waveguide is separated from the waveguide via a gap.

19. The system of claim 18 , wherein the gap has a constant cross-sectional width for a predetermined length.

20. A method comprising:

receiving light emitted in a crosstrack direction from a light source at a fundamental transverse electric (TE 00 ) mode;

redirecting the light to an opposite crosstrack direction into a straight section of a waveguide via a first turn of the waveguide;

converting light to a higher-order (TE 10 ) mode via a branched portion that extends from the straight section of the waveguide;

redirecting the light to a direction normal to a media-facing surface of the write head via a second turn of the waveguide, the second turn coupled to the straight section;

coupling the light in the TE 10 mode to a near-field transducer at the media-facing surface, the near-field transducer directing surface plasmons to a recording medium in response thereto; and

delivering the light to the near-field transducer at the direction normal to the media-facing surface.