Harmonic sensor phase error detection for data storage devices

A method comprising:

• writing, using a head actuated over a non-volatile storage medium of a data storage device, a tone pattern to at least one track on the non-volatile storage medium;
• acquiring, using a harmonic sensor in a read channel configured to receive a read signal from the head, amplitude data from the tone pattern and corresponding to differences between a target frequency of the tone pattern and a read frequency from the read signal;
• determining, based on the amplitude data, a plurality of phase error values;
• and
• determining, based on the plurality of phase error values, an operating condition during the writing.

A data storage device comprising:

• a non-volatile storage medium comprising a plurality of data tracks;
• a head actuated over the non-volatile storage medium, wherein the head comprises a laser configured to heat the non-volatile storage medium while writing data to the non-volatile storage medium;
• means for writing, using the head, a tone pattern to at least one track on the non-volatile storage medium;
• means for acquiring, using a harmonic sensor in a read channel configured to receive a read signal from the head, amplitude data from the tone pattern and corresponding to differences between a target frequency of the tone pattern and a read frequency from the read signal;
• means for determining, based on the amplitude data, a plurality of phase error values;
• and
• means for determining, based on the plurality of phase error values, an operating condition of the laser during the writing.