Bolometric sensor for a heat-assisted magnetic recording device
An apparatus comprises a slider configured for heat-assisted magnetic recording comprising an air bearing surface (ABS). The slider comprises a write pole at or near the ABS, and a near-field transducer (NFT) at or near the ABS and proximate the write pole. A main waveguide is configured to receive light from a laser source and communicate the light to the NFT. An optical power sensor comprises a tap waveguide optically coupled to the main waveguide and comprising a first end and an opposing second end. The optical power sensor also comprises a bolometer optically coupled to the tap waveguide and configured to receive a portion of the light extracted from the main waveguide by the tap waveguide.
1. An apparatus, comprising:
a slider configured for heat-assisted magnetic recording comprising an air bearing surface (ABS), the slider comprising:
a write pole at or near the ABS;
a near-field transducer (NFT) at or near the ABS and proximate the write pole;
a main waveguide configured to receive light from a laser source and communicate the light to the NFT; and
an optical power sensor comprising:
a tap waveguide optically coupled to the main waveguide and comprising a first end and an opposing second end; and
a bolometer optically coupled to the tap waveguide and configured to receive a portion of the light extracted from the main waveguide by the tap waveguide;
wherein the bolometer is offset from the main waveguide at a location such that the bolometer does not directly sense an optical field of the main waveguide at the location.
2. The apparatus of claim 1 , wherein the tap waveguide is situated lateral of the main waveguide along a longitudinal section of the main waveguide.
3. The apparatus of claim 1 , wherein tap waveguide has an arcuate shape such that the first and second ends are spaced further away from the main waveguide relative to a middle section of the tap waveguide.
4. The apparatus of claim 1 , wherein:
the bolometer is situated at or proximate the first end of the tap waveguide; and
a light absorbing or anti-reflection feature is situated at or proximate the second end of the tap waveguide.
5. The apparatus of claim 4 , wherein the bolometer and the light absorbing or anti-reflection feature are configured to provide 100% or nearly 100% light absorption.
6. The apparatus of claim 1 , wherein the bolometer is situated at or proximate the first end of the tap waveguide such that the bolometer detects only a forward propagating mode that excites the NFT.
7. The apparatus of claim 1 , wherein the bolometer is situated at or proximate to the first end of the tap waveguide such that:
the bolometer is configured to detect only a forward propagating mode that excites the NFT; and
a back reflection enters the bolometer only from a reflection of the second end of the tap waveguide.
8. The apparatus of claim 1 , wherein the tap waveguide and the bolometer are configured to reduce an impact of back reflection on mode hopping detection by at least a factor of 5 relative to a bolometer situated directly above the main waveguide.
9. The apparatus of claim 1 , wherein the main waveguide and the tap waveguide are configured to provide adiabatic coupling therebetween.
10. The apparatus of claim 1 , wherein:
the bolometer is situated at or proximate to the first end of the tap waveguide; and
the second end of the tap waveguide comprises an angled end termination.
11. The apparatus of claim 1 , wherein:
the bolometer is situated at or proximate to the first end of the tap waveguide; and
the second end of the tap waveguide comprises a dipole nano-rod array.
12. The apparatus of claim 1 , wherein:
the bolometer is situated at or proximate to the first end of the tap waveguide; and
the second end of the tap waveguide comprises a dielectric grating.
13. The apparatus of claim 1 , wherein:
the bolometer is situated at or proximate to the first end of the tap waveguide; and
the second end of the tap waveguide comprises an escape slab.
14. The apparatus of claim 1 , wherein:
the bolometer is situated at or proximate to the first end of the tap waveguide;
a first light absorbing or anti-reflection feature is situated at or proximate the first end of the tap waveguide; and
a second light absorbing or anti-reflection feature is situated at or proximate the second end of the tap waveguide.
15. An apparatus, comprising:
a slider configured for heat-assisted magnetic recording comprising an air bearing surface (ABS), the slider comprising:
a write pole at or near the ABS;
a near-field transducer (NFT) at or near the ABS and proximate the write pole;
a main waveguide configured to receive light from a laser source and communicate the light to the NFT;
a tap waveguide optically coupled to the main waveguide and comprising a first end and a second end;
a light absorbing or anti-reflection feature situated at or proximate the second end of the tap waveguide; and
a bolometer optically coupled to the first end of the tap waveguide and configured to receive a portion of the light extracted from the main waveguide by the tap waveguide, wherein:
the bolometer is configured detect only a forward propagating mode that excites the NFT and a back reflection enters the bolometer only from a reflection of the second end of the tap waveguide; and
the bolometer is offset from the main waveguide at a location such that the bolometer does not directly sense an optical field of the main waveguide at the location.
16. The apparatus of claim 15 , wherein tap waveguide has an arcuate shape such that the first and second ends are spaced further away from the main waveguide relative to a middle section of the tap waveguide.
17. The apparatus of claim 15 , wherein:
the bolometer is situated at or proximate to the first end of the tap waveguide; and
the second end of the tap waveguide comprises an angled end termination.
18. The apparatus of claim 15 , wherein:
the bolometer is situated at or proximate to the first end of the tap waveguide; and
the second end of the tap waveguide comprises a dipole nano-rod array.
19. The apparatus of claim 15 , wherein:
the bolometer is situated at or proximate to the first end of the tap waveguide; and
the second end of the tap waveguide comprises a dielectric grating.
20. The apparatus of claim 15 , wherein:
the bolometer is situated at or proximate to the first end of the tap waveguide; and
the second end of the tap waveguide comprises an escape slab.
21. A method comprising:
communicating light from a laser source to a near-field transducer of a slider configured for heat-assisted magnetic recording via a main waveguide of the slider;
extracting a portion of the light from the main waveguide by a tap waveguide comprising a first end and an opposing second end; and
detecting, by a bolometer situated at or proximate the first end of the tap waveguide and offset from the main waveguide at a location such that the bolometer does not directly sense an optical field of the main waveguide at the location, only a forward propagating mode that excites the NFT such that a back reflection enters the bolometer only from a reflection of the second end of the tap waveguide.
22. The method of claim 21 , comprising determining output optical power of the light source using a signal generated by the bolometer.