a tamr write head uses the energy of optical - laser generated plasmons in a plasmon generator to locally heat a magnetic recording medium and reduce its coercivity and magnetic anisotropy . to enable the tamr head to operate most effectively , the antenna is formed in three portions , a wide portion of uniform horizontal area , a tapered portion tapering towards the abs of the write head and a narrow tip extending from the tapered portion to the abs . the wide portion enhances coupling of optical radiation from a waveguide to surface plasmons generated within the generator , the tapered portion condenses and focuses the plasmons as they propagate towards the abs and the narrow tip further focuses the surface plasmon field at the medium surface .