Excitation and localization of surface plasmon polariton modes in metal-dielectric structures can be utilized to construct
unique nanophotonic materials and devices with tuneable optical transmission. We present selective polariton generator
(SPG) designs that demonstrate selective light transmission based on surface plasmon antennae principles. These
polarisation-sensitive structures can selectively generate and transport polaritons of a desired wavelength through
subwavelength apertures. By specifying geometry and orientation we can control the operational characteristics of these
elements. By varying SPG designs around a central nanohole we are able to achieve operation of nanophotonic devices
where optical transmission peak wavelengths are controlled via the polarisation state of the incident photons. The design
considerations of grating periods, corrugation fan angles, transmission due to inner ring variations, and spectral
separation of paired SPGs were investigated along with the potential of flanking the structures with Bragg reflector
corrugations. The simulations were compared with the experimental results for agreement of the models, which could
lead to experimental investigations of more complex structure.
Lab on chip (LOC) systems often require the controlled movement of individual biological cells. Automated operation
of these systems usually requires detectors to track individual cells. Electrical methods involving measurement of the
conductivity or permittivity of regions between two electrodes are capable of providing this information. However, these
detection systems can interfere with other dielectrophoretic LOC cell handling systems. Conversely optical systems are
immune to electrical interference. Many LOC devices are fabricated with only the top surface of the device being
transparent to light, precluding the use of transmitted optical detection. This is often due to the use of silicon, a favoured
substrate. Here we present a low cost optical system suitable for detecting biological cells in microfluidic channels.
A flow cell with a fluid microlayer approximately 105±10μm deep was fabricated having a 100±10μm thick glass
window, and a reflective base layer. The reflective base was formed by thermal evaporation of gold onto a substrate.
Particles within a microfluidic layer were epi-illuminated by a standard (red) laser DVD pickup unit. The flow cell
permitted the laser beam to be focussed onto the gold reflector, and back through a beamsplitter onto a photodiode. This
system was tested using polystyrene beads that were representative of biological cells. The position of the focal point significantly affected the base line reflected signal, but this micron scale position sensitivity could be overcome using the magnetic focussing coil of the DVD pickup. In this system, polystyrene beads down to 3μm in diameter were successfully detected.
Surface plasmon resonance (SPR) has been used for some time in chemical and biological sensors. Some of the schemes
for exciting surface plasmons include prisms and gratings. Grating-based optical SPR sensors have been demonstrated,
which use light intensity variations at resonance or wavelength interrogation. Recently, a gold grating made from a
commercial recordable compact disk was used for excitation of surface plasmons and SPR imaging. In this paper, we
present a new grating configuration that combines the benefits of multi-angle interrogation with interferometric
measurement techniques. This gives array sensing capability over a wide refractive index range. The set-up is based on
the gold grating of commercially available recordable compact disks, which are mass produced by injection-moulding,
resulting in low cost and disposable grating substrates. The potential of using this system for large sample number
analysis is demonstrated.
The orthogonal axes of illumination, flow, and detection in conventional sorting flow cytometers can limit accuracy or throughput when making fluorescence measurements on a spherical cells. A new radially symmetric optical configuration has been designed to overcome these problems. Both illumination and fluorescence collection are performed by a single optical element which encircles the sample stream flow axis. Unlike existing epi-illumination flow cytometer designs, these optics are compatible with electrostatic sorting. The resolution of this system is currently being evaluated for DNA chromosome content measurement with an ultimate goal of separation of X- and Y- chromosome-bearing mammalian spermatozoa. We describe the new optical configuration and present preliminary results of instrument performance. Comparison with a conventional orthogonal optical geometry is made using fluorescent microspheres, chicken red blood cells and chinchilla sperm.
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