Heat-assisted magnetic recording head with an integrated photodiode
A heat-assisted magnetic recording head includes a laser, a near-field transducer, a primary waveguide, a secondary waveguide, and a photodiode. The laser is configured to emit electromagnetic radiation. The near-field transducer is configured to focus and emit an optical near-field. The primary waveguide configured to receive the electromagnetic radiation and propagate the electromagnetic radiation toward and proximal to the near-field transducer. The secondary waveguide configured to receive a portion of the electromagnetic radiation from the primary waveguide. The photodiode configured to receive the portion of the electromagnetic radiation from the secondary waveguide and emit a signal that represents a magnitude of the electromagnetic radiation that the laser emits.
1. A heat-assisted magnetic recording head comprising:
a first waveguide configured to propagate light from a laser to a near-field transducer; and
a second waveguide having a middle segment disposed between a first end segment and a second end segment, the second waveguide configured such that (a) the middle segment is substantially parallel with and in close proximity to a portion of the first waveguide to thereby couple a portion of the light propagating in the first waveguide into the middle segment of the second waveguide, (b) the first end segment propagates light coupled into the second waveguide to a photodiode located near a termination point of the first end segment, and (c) the second end segment has a hooked shape that mitigates reflections of light propagating in the second end segment from reaching the photodiode.
2. The heat-assisted magnetic recording head of claim 1 , wherein the middle segment of the second waveguide is separated from the portion of the first waveguide by a gap having a width of about 50 nanometers to about 1 micrometer.
3. The heat-assisted magnetic recording head of claim 1 , wherein the middle segment of the second waveguide and the portion of the first waveguide are substantially parallel to each other over a length of about 30 micrometers or less.
4. The heat-assisted magnetic recording head of claim 1 , wherein the photodiode is adjacent to a grating structure that is configured to direct light from the second waveguide into the photodiode.
5. The heat-assisted magnetic recording head of claim 1 , wherein the first waveguide is coupled to a coupler that is configured to direct light emitted by the laser into the primary waveguide.
6. The heat-assisted magnetic recording head of claim 5 , wherein the coupler includes a hooked shape that is configured mitigate light reflections.
7. The heat-assisted magnetic recording head of claim 5 , wherein the coupler includes an escape slab that is configured to disperse stray light.
8. The heat-assisted magnetic recording head of claim 1 , wherein the first end segment of the second waveguide is coupled to a coupler that is configured to direct light into the photodiode.