Abstract
Nanostructures that have dimensions commensurate with the wavelength of the
electromagnetic radiation exhibit near-field effects1,2 and, as optical antennas, can
couple laser radiation to the local environment3. Laser-induced silicon microcolumn
arrays behave as nanophotonic ion sources that can be modulated by rotating the
plane of light polarization4,5. Here we demonstrate that nanopost arrays (NAPA)
can be tailored to exhibit resonant ion production. Ion yields from posts with
subwavelength diameter show sharp resonances at high aspect ratios. The resonant
enhancement in ion intensities can be modulated by adjusting the periodicity. In
addition to strong molecular ion formation, the presence of high energy
fragmentation channels is observed. Ion yields from NAPA exhibit dramatic
differences for p- and s-polarized laser beams, indicating that energy coupling is
similar to antenna arrays. These nanophotonic ion sources can control the degree of
ion fragmentation and could eventually be integrated with micromachined mass
spectrometers and microfluidic devices.
