Peg height of near-field transducers

1. A method comprising:

providing excitation radiation to a plurality of near-field transducer devices, each of the near-field transducer devices comprising:

an enlarged region; and

a peg region at least partially in contact with the enlarged region;

filtering output radiation from the near-field transducer devices, the filtering comprising passing a portion of photoluminescent radiation emitted by the near-field transducer devices in response to the excitation radiation and substantially blocking the excitation radiation transmitted by the near-field transducer devices;

detecting the portion of photoluminescent radiation; and

characterizing the peg regions of the near field transducer devices using the detected portion of photoluminescent radiation.

2. A method according to claim 1 , further comprising determining if the peg regions meet a predetermined height.

3. A method according to claim 1 , wherein:

the near field transducer devices comprise pegs having various peg heights;

further comprising identifying a peg height that provides acceptable near field transducer performance based on characterization of the peg regions; and

forming a guide for lapping slider bars based on the identified peg height.

4. The method of claim 3 , wherein the identified peg height is an optimal peg height that provides a maximum amount of the detected photoluminescent radiation.

5. A method according to claim 1 , wherein filtering the output radiation comprising filtering using a shortwave pass optical filter.

6. A method according to claim 1 , wherein providing excitation radiation to the near-field transducers comprises providing laser pulses at a repetition rate.

7. A method according to claim 6 , wherein blocking the excitation radiation comprises attenuating the excitation radiation by a factor of about 10 −4 or better.

8. A method according to claim 1 , further comprising signal processing the output signal including amplifying the output signal using circuitry that locks into a repetition rate of the excitation radiation.

9. A system comprising:

an excitation light source configured to provide excitation radiation to a wafer bar, the wafer bar comprising a plurality of near-field transducers each of which includes:

an enlarged region; and

a peg region having a peg height, the peg region at least partially in contact with the enlarged region and the plurality of near-field transducers having at least two different peg heights;

an optical filter configured to substantially pass a portion of photoluminescent radiation emitted by the near-field transducer in response to the excitation radiation and to substantially block the excitation radiation; and

a detector configured to detect the portion of photoluminescent radiation and to output an output signal in response to detection of the portion of photoluminescent radiation.

10. A system according to claim 9 , further comprising

a focusing lens configured to focus the excitation radiation onto an input coupler of the near-field transducer; and

an objective lens configured to collect the photoluminescent radiation emitted by the enlarged disk region toward the optical filter.

11. A system according to claim 9 , wherein the excitation radiation comprises femto-second or pico-second laser pulses.

12. A system according to claim 9 , wherein the optical filter is configured to substantially pass radiation having wavelengths shorter than the excitation light.

13. A system according to claim 9 , further comprising a monitoring subsystem configured to monitor the excitation radiation.

14. A system according to claim 13 , wherein the monitoring subsystem comprises an output side photodetector configured to generate a signal in response to output radiation transmitted through the near-field transducers, the output radiation dominated by the excitation radiation.

15. A system according to claim 9 , further comprising an amplifier coupled to receive the detector signal, wherein the amplifier is configured be locked-in to a repetition frequency of the excitation radiation.