HAMR read-write head with coupler and waveguide

A method of recording data using a heat assisted magnetic recording head, the magnetic recording head comprising:

• a light source,
• an optical coupler that receives light from the light source at a coupler input facet, the optical coupler having a length extending from the input facet in a direction of light propagation through the coupler,
• a waveguide coupled to the optical coupler at a coupler-waveguide interface,
• a diffractive cavity coupled to the optical coupler between the input facet and the coupler-waveguide interface, wherein the diffractive cavity has a focusing structure that produces a lensing effect,
• a near-field transducer coupled to the waveguide, that provides electromagnetic heating for a heat assisted magnetic recording write head,
• the method comprising:
• activating the light source to direct light into the coupler input facet,
• allowing the light to propagate through the coupler and into the waveguide, to be received by the near-field transducer.