Patent ID: 8780678

Claim:
A thermal-assisted-magnetic-recording head characterized in that the thermal-assisted-magnetic-recording head comprises: a magnetic main pole configured to generate a write magnetic field, a magnetic return pole, a magnetic reproducing element, a shield formed around the magnetic reproducing element, and a spot size converter including a clad and a core configured to emit light from an optical source as a fine light spot from a position adjacent to the magnetic main pole on an air bearing surface side, and at least one side surface of the core is covered with a cover layer having a refractive index lower than those of the core and the clad, wherein thickness of the cover layer is within a range of ±30% of Tc, the TC is expressed in a formula shown below: Tc = A · t 1 Ww where; A is defined by: n 1 ·t 1 +n 3 ·A=n 2 ·( t 1 +A ) n 1 : refractive index of core material n 2 : refractive index of clad material n 3 : refractive index of cover layer t 1 : thickness of core Ww: approximate width or thickness that induces the seeping mode expressed in a formula shown below: Ww = π 2 ⁢ π · n 1 · sin ⁢ ⁢ θ 1 / λ where θ 1 is represents a critical angle of the light at an interface between the core and the clad and can be expressed with a formula shown below: θ 1 = sin - 1 ( n 1 2 - n 2 2 n 1 ) where; λ: wavelength of light in vacuum n 1 : refractive index of core material n 2 : refractive index of clad material.