Showing papers by "Peter Zijlstra published in 2007"

Spectral encoding on Gold Nanorods Doped in a Silica Sol–Gel Matrix and Its Application to High‐Density Optical Data Storage

Abstract: Metallic nanorods exhibit fascinating optical properties due to surface plasmons-collective oscillation of the electron cloud within a particle. They exhibit two principle absorption bands that correspond to surface plasmon resonance (SPR) along the longitudinal and transverse directions of the nanorod. Most importantly, the longitudinal band can be tuned with the aspect ratio of the rod, making it a spectrally tuneable optical material, which can be applied to a variety of devices from bioimaging to high-density optical storage. Here, spectral encoding for high-density optical storage applications is demonstrated on two sizes of gold nanorods (aspect ratios of three and five) doped in a silica sol-gel matrix by femtosecond pulsed laser irradiation. It is widely known that high-power pulsed laser irradiation causes metal nanorods to undergo shape transformations via the process of melting or fragmentation. The process is enhanced if the laser wavelength is tuned at the longitudinal surface plasmon resonance peak of the nanorods, which results in a significant reduction or shift in the surface plasmon resonance peak. As such a shape change occurs only on the subpopulation of rods that have a longitudinal plasmon band matching the laser wavelength, a size- or spectrum-selective shape transition is possible in a rod mixture with varying aspect ratios. The current spectral encoding technology can be incorporated into existing optical disc technology, such as three-dimensional bit-by-bit and holographic, and can increase the capacity limit by utilizing the spectral domain.

Effect of heat accumulation on the dynamic range of a gold nanorod doped polymer nanocomposite for optical laser writing and patterning

Abstract: Even though gold nanorod doped dielectrics have been widely used for optical laser writing and patterning there has been no attempt to study the dynamic range of these nanocomposites, let alone exploring ways to improve this property. Here we study the dynamic range of a gold nanorod doped polyvinyl alcohol film for various laser spot sizes at two different laser pulse repetition rates and show that when a high repetition rate laser source is employed the dynamic range of the nanocomposite is severely limited due to accumulative heating inside the focal volume. This problem could be solved by silica-coating the nanorods inside the polymer matrix. This method does not compromise the high repetition rate of the laser writing source and yet retains the attractive flexible properties of the polymer matrix. The silica-coated gold nanorod doped polymer nanocomposite could be an attractive medium for future high-speed, high repetition rate pulsed laser writing and patterning applications.

Spatial refractive index sensor using whispering gallery modes in an optically trapped microsphere

Abstract: The authors propose the use of an optically trapped, dye doped polystyrene microsphere for spatial probing of the refractive index at any position in a fluid. Using the dye embedded in the microsphere as an internal broadband excitation source the authors eliminated the need for a tunable excitation source. They measured the full width at half maximum and frequency spacing of the transverse electric and transverse magnetic resonances as a function of the refractive index of the immersion fluid. The authors achieved a sensitivity of 5×10−4 in refractive index, even when the exact size of the microsphere was not known.

Wavelength Multiplexed Optical Storage in Plasmonic Gold Nanorods

Abstract: In this paper we propose the use of wavelength as an extra recording dimension by exploiting the plasmonic properties of anisotropic gold nanorods. The wavelength of the longitudinal absorption band can be tuned from the visible to near infrared wavelength region by changing the aspect ratio of the nanorod. Data bits are recorded by femtosecond laser induced reshaping of nanorods in the focal volume. The data can be read out in transmission by monitoring the change in absorption at the recording wavelength.