One embodiment generally relates to a magnetic recording head. The magnetic recording head has a body having an upper surface and a media bearing surface, a spot size converter disposed in the body and extending from the upper surface to the media bearing surface. The spot size converter has a core, comprising a first portion having a rectangular wall extending below the upper surface; and a second portion having a trapezoidal wall extending below the first portion. The magnetic recording head additionally has a first cladding adjacent to the spot size converter in an in-surface direction of the spot size converter, wherein the first cladding has a first refractive index lower than a refractive index of the spot size converter.