Data can be transmitted and represented by signal gaps in a transmission, the gaps having various attributes. In various examples, data points are encoded and represented by the attributes of said signal gaps. Various attributes of such gaps, including duration, pattern, quantity, time, and/or coordination with a gap in another signal can represent data.

A method and apparatus for optical metrology is disclosed. There is disclosed, for example, a method involving a radiation intensity distribution for a target measured using an optical component at a gap from the target, the method including calculating a correction factor for the variation of radiation intensity of the radiation intensity distribution as a function of variation of the distance of the gap.

A TAMR (thermal assisted magnetic recording) write head has a metal blocker formed against a distal end of a waveguide. The waveguide focuses optical radiation on an adjacent plasmon generator where it excites plasmon modes that heat the recording medium. Although the plasmon generator typically heats the recording medium using the plasmon near field to supply the required Joule heating, an unblocked waveguide would also send optical radiation to the medium and surrounding structures producing unwanted heating and device unreliability. The role of the blocker is to block the unwanted optical radiation and, thereby, to limit the heating to that supplied by the plasmon near field.

A set of consecutive user data wedges are each located between consecutive servo wedges of a heat-assisted recording medium. Test data is written at least every other one of the consecutive data wedges using different laser power values. Based on reading the test data, a nominal laser power is selected for use by the read/write head.

An apparatus determines that phase errors have exceeded a threshold when reading data previously recorded to a heat-assisted recording medium. In response to the phase errors exceeding the threshold, remedial action is taken to prevent loss of data due changes in power applied to heat the heat-assisted recording medium when recording.

Data is written to a magnetic recording medium of a drive using a read/write head. The read/write head has an energy source that applies a hotspot to the magnetic recording medium while recording. During the writing, a steady-state current applied to the energy source is changed by a step value. A timing error induced by the change in the steady-state current is measured based on reading back the data. A thermal gradient of the hotspot is determined based on the step value and the timing error.

First and second nominal head-to-media spacings of a magnetic recording head are determined that result in tracks being written to a magnetic recording medium at respective narrower and wider tracks widths. Three or more adjacent tracks of user data are written to the magnetic recording medium using one of the first and second nominal head-to-media spacings so that the adjacent tracks alternate between the narrower and wider track widths.

First and second different write precompensation values are associated with different first and second non-return-to-zero, inverted (NRZI) data patterns. The first and second different write precompensation values cause a predetermined phase shift to be written into test data that comprises the first and second NRZI data patterns. The test data is mitten to a recording medium of a storage device using the first and second write precompensation value. The test data is used to determine a response of the storage device to the predetermined phase shift.

A lumped-parameter function δ is determined that represents an average power dissipated by a write transducer when writing a signal to a magnetic recording medium. Temperatures of the write transducer are measured while varying the parameters to determine constants of the function δ. The function δ is used to adjust power applied to a clearance control heater when writing to the magnetic recording medium.

A near field transducer includes gold and at least one dopant. The dopant can include at least one of: Cu, Rh, Ru, Ag, Ta, Cr, Al, Zr, V, Pd, Ir, Co, W, Ti, Mg, Fe, or Mo. The dopant concentration may be in a range from 0.5% and 30%. The dopant can be a nanoparticle oxide of V, Zr, Mg, Ca, Al, Ti, Si, Ce, Y, Ta, W, or Th, or a nitride of Ta, Al, Ti, Si, In, Fe, Zr, Cu, W or B.