Sub-optical-resolution kerr signal detection for perpendicular write-head characterization

An apparatus for determining a property of a write pole of a write head, the apparatus comprising:

• a light source that produces a light beam;
• a polarizer in a path of the light beam and generates a polarized light beam;
• optical elements that cause the polarized light beam to be incident on and reflected by the write pole, the optical elements having an optical resolution limit, the write pole being smaller than the optical resolution limit;
• an electrical energy source that is configured to be coupled to the write head to produce a magnetization of the write pole while the polarized light beam is incident on and reflected by the write pole;
• a polarization state analyzer in a path of reflected light from the write pole;
• at least one light detector in the path of the reflected light with the polarization state analyzer between the at least one light detector and the write head and produces optically detected data in response to the magnetization of the write pole;
• and
• a processor coupled to receive the optically detected data from the at least one light detector, the processor configured to determine the property of the write pole based on the optically detected data from the at least one light detector.

A method comprising:

• applying a first current to a write head;
• applying a second current to the write head, the second current being different than the first current;
• optically detecting a first magnetization of the write head while applying the second current;
• using the first magnetization to determine a property of the write head;
• and
• storing the property of the write head.

An apparatus comprising:

• an optical metrology device capable of optically detecting magnetization of a write head;
• an electrical energy source that is configured to be coupled to the write head to produce a magnetization of the write pole;
• and
• a processor coupled to the optical metrology device and the electrical energy source, the processor configured to cause the electrical energy source to apply a first current to the write head;
• to cause the electrical energy source to apply a second current to the write head, the second current being different than the first current, to cause the optical metrology device to optically detect a first magnetization of the write head while the second current is applied;
• to use the first magnetization to determine a property of the write head;
• and to store the property of the write head in a memory.