HAMR recording head with external cavity laser using a near-field transducer as a reflector

1. An external cavity laser of a recording head, comprising:

a channel waveguide that delivers light towards a media-facing surface of the recording head;

an externally mounted part comprising an active region having a longitudinal axis corresponding to a light propagation direction of the channel waveguide, the externally mounted part comprising a reflective back facet and anti-reflective front facet; and

a near-field transducer at an end of the channel waveguide proximate the media facing surface, the near-field transducer comprising a plate structure and a peg extending from the plate structure towards the media-facing surface, the reflective back facet and the near-field transducer defining a resonator of the external cavity laser, wherein the near-field transducer reflects no more than 15% of the light back towards the externally mounted part.

2. The external cavity laser of claim 1 , further comprising a Bragg grating within the channel waveguide and having a longitudinal axis defined along the light propagation direction, the Bragg grating located proximate the near-field transducer so that the Bragg grating and near-field transducer function together as a reflector of the resonator of the external cavity laser, the reflector reflecting more than 15% of the light back towards the externally mounted part.

3. The external cavity laser of claim 2 , wherein the Bragg grating is separated from the near-field transducer by 5 μm or less.

4. The external cavity laser of claim 2 , wherein the channel waveguide delivers the light in a transverse electric mode, and wherein the Bragg grating comprises serrations on opposing crosstrack sides of a core of the channel waveguide.

5. The external cavity laser of claim 4 , wherein the serrations are at least one of rectangular and sinusoidal.

6. The external cavity laser of claim 4 , wherein the serrations comprise at least two sets of serrations having different periodicity.

7. The external cavity laser of claim 4 , wherein the serrations comprise at least two sets of serrations separated by a cavity without serrations.

8. The external cavity laser of claim 2 , wherein the channel waveguide delivers the light in a transverse magnetic mode, and wherein the Bragg grating comprises serrations on opposing downtrack sides of a core of the channel waveguide.

9. The external cavity laser of claim 2 , further comprising a heater proximate the Bragg grating, the heater operable to shift a resonance wavelength of the Bragg grating in response to a controller input.

10. An external cavity laser of a recording head, comprising:

a channel waveguide that delivers light towards a media-facing surface of the recording head;

an externally mounted part comprising an active region having a longitudinal axis corresponding to a light propagation direction of the channel waveguide, the externally mounted part comprising a reflective back facet and anti-reflective front facet;

a near-field transducer at an end of the channel waveguide proximate to a media-facing surface; and

a Bragg grating within the channel waveguide and having a longitudinal axis defined along the light propagation direction, the Bragg grating separated from the near-field transducer by 5 μm or less.

11. The external cavity laser of claim 10 , wherein the near-field transducer comprises a plate structure and a peg extending from the plate structure towards the media-facing surface.

12. The external cavity laser of claim 10 , wherein Bragg grating and the near-field transducer function as a reflector, the reflective back facet and the reflector defining a resonator of the external cavity laser.

13. The external cavity laser of claim 10 , wherein the channel waveguide delivers the light in a transverse electric mode, and wherein the Bragg grating comprises serrations on opposing crosstrack sides of a core of the channel waveguide.

14. The external cavity laser of claim 13 , wherein the serrations are rectangular or sinusoidal.

15. The external cavity laser of claim 13 , wherein the serrations comprise at least two sets of serrations having different periodicity.

16. The external cavity laser of claim 13 , wherein the serrations comprise at least two sets of serrations separated by a cavity without serrations.

17. The external cavity laser of claim 10 , wherein the channel waveguide delivers the light in a transverse magnetic mode, and wherein the Bragg grating comprises serrations on opposing downtrack sides of a core of the channel waveguide.

18. The external cavity laser of claim 10 , further comprising a heater proximate the Bragg grating, the heater operable to shift a resonance wavelength of the Bragg grating in response to a controller input.

19. The external cavity laser of claim 10 , wherein the Bragg grating being separated from the near-field transducer by 5 μm or less results in a mode hop spacing of approximately 36 nm or less.