FEBRUARY 1998 REPORT FOR

W. CHARLES SYMONS, III

This year, an abstract entitled Electromagnetic Scattering Analysis of Sample Objects Within the Near-Field of a Subwavelength Aperture Utilizing FDTD Methods was submitted to the 1998 IEEE AP-S International Symposium and USNC/URSI National Radio Science Meeting being held in Atlanta, GA June 21-26. This presentation will be based on the previously developed Finite-Difference Time-Domain (FDTD) model of the Near-Field Scanning Optical Microscope (NSOM).

Once the AP-S/URSI abstract was submitted, two preliminary tests of the laser dermatome were performed as seen in Figure 1 below. The first test utilized a CO2 laser source in continuous wave mode. With this source, the dermatome code was refined so as to determine the optimal parameters necessary to produce the best possible skin grafts. The second dermatome test utilized the same CO2 laser primarily in pulsed mode. The pulsed mode setting was utilized to produce the best possible skin grafts while reducing any burning effects as much as possible. During this test, the dermatome program was again modified to determine the best parameter selections for this mode of operation. Both dermatome tests provided valuable insight into the dermatome's operation. In preparation for the next test, several hardware and software changes are being implemented to improve performance. For example, in order to facilitate manual manipulation and to reduce power consumption, the dermatome's stepper motors were left unlocked and free to move. However, upon performing the tests grafts, it was determined that both the drum motor and the horizontal positioning motor must be locked to avoid hysteresis type problems.

Figure 1: Experimental Dermatome Setup (Quicktime Movie).

In addition to the above mentioned abstract submission and the dermatome tests, both the NSOM instrument and the Moment Method NSOM simulation code were further developed. For the NSOM instrument, the Melles Griot Nanoblock-M stage seen in Figure 2 below and its controller hardware finally arrived. In conjunction with this, a new PC with a PCI bus was obtained to replace the older PC being used for control and data acquisition purposes. The newer PC was required to accommodate the PCI bus GPIB card being utilized to control the coarse movement of the Melles Griot Nanoblock-M stage. This PC has now had its hard drive reformatted and has been reinstalled with Windows 95. The new hardware is currently being installed and tested in preparation for new code which is also being developed to drive the instrument. As for the simulation code, the excitation vector has been slightly modified and a new convergence study is in progress with results pending.

Figure 2: Melles Griot Stage.