High efficiency grating coupling for light delivery in EAMR

An energy-assisted magnetic recording head comprising:

• a dual-grating waveguide coupler for coupling incident electromagnetic (EM) radiation into a waveguide, the waveguide coupler comprising:
• a bottom clad layer;
• a waveguide core layer formed above the bottom clad layer, wherein an interface between the bottom clad layer and the waveguide core layer comprises a first grating having a first period and a first etch depth, the first period and the first etch depth being configured to couple a first portion of the incident EM radiation into the waveguide core layer;
• a top clad layer formed above the waveguide core layer, wherein an interface between the waveguide core layer and the top clad layer comprises a second grating having a second period and a second etch depth, the second period and the second etch depth being configured to couple a second portion of the incident EM radiation into the waveguide core layer;
• and
• a near field transducer (NFT) disposed at a distal end of the waveguide coupler and configured to receive a coupled EM radiation from the distal end the waveguide coupler, the coupled EM radiation comprising the first coupled portion and the second coupled portion of the incident EM radiation, and to concentrate the coupled EM radiation onto a spot on a magnetic recording medium,
• wherein the first portion of the incident EM radiation has a first polarization, and wherein the second portion of the incident EM radiation has a second polarization, and
• further wherein one of the first and second polarizations is a transverse-electric (TE) polarization or a left circular polarization, and the other of the first and second polarizations is a transverse-magnetic (TM) polarization or a right circular polarization, respectively.