A general strategy for fabricating thick, optically flat photopolymer recording media with high dynamic range (M/#) that exhibit low levels of recording-induced Bragg detuning for holographic data storage is presented. In particular, media with M/# values as high as 42 in 1-mm-thick formats are obtained. We believe that these results are the first demonstration of a holographic storage medium with a dynamic range of this magnitude. In addition, we report the holographic recording and recovery of high-capacity (480-kbit) digital data pages in these media, further illustrating their data-storage capabilities.
Single and multiple-pulse impulsive stimulated Raman-scattering (ISRS) experiments are used to investigate the anomalously high damping rates of the lowest frequency Al polariton in LiTa03. The wave-vector dependence of the response reveals coupling of the polariton to a weakly Raman-active, low-frequency relaxational mode as well as to two underdamped modes of a different symmetry. Inclusion of the coupled modes yields quantitative agreement between the results and the predictions of a previously developed theory for light scattering from polaritons.
A laser light source for high-resolution near-field optics applications with an output power exceeding 1 mW (104 times the power from previous sources) and small (300 nm square to less than 50 nm square) output beam size is demonstrated. The very-small-aperture laser (VSAL) tremendously expands the range of applications possible with near-field optics and increases the signal-to-noise ratios and data rates obtained in existing applications. As an example, 250-nm-diam marks corresponding to 7.5 Gb/in.2 storage density have been recorded and read back in reflection and transmission on a rewritable phase-change disk at 24 Mb/s with a 250-nm-square aperture VSAL. VSALs potentially enable data storage densities of over 500 Gb/in.2 (up to 100 times today’s magnetic or optical storage densities).
The lifetime of the first excited level of the symmetric C-H stretching mode of CH3S chemisorbed on a Ag(lll) surface was measured by picosecond vibrational spectroscopy. A biexponential decay (--3and 63-ps lifetimes at 300 K) was observed, with a substantial temperature dependence of the slow component. Both decay processes are assigned to intramolecular vibrational relaxation. The decay rates are 2 orders of magnitude too fast to be explained by electron-hole-pair damping by the metal substrate.PACS numbers: 82.20. Rp, 34.30.+h, 78.47.+p Despite the fundamental importance of vibrational energy transfer to chemical processes at metal surfaces, there have been no time-domain measurements of vibrational lifetimes for adsorbates on single-crystal surfaces. ] This Letter reports such measurements for the first excited level of the symmetric C-H stretching mode of methyl thiolate, CH3S, chemisorbed on a Ag(l 11) surface. Previous indirect measurements based on linewidth have assigned the vibrational relaxation of this mode in similar adsorbates [CH 3 O/Cu(100) and CH 3 C/Pt(l 11)] to electron-hole-pair excitation in the metal. 2 The present results show that the vibrational linewidth is not determined in CH3S by vibrational energy relaxation. In addition, the relaxation itself is assigned to intramolecular energy transfer. The previous assignments must be reconsidered. The results demonstrate the importance of intramolecular energy transfer for small polyatomic molecules even where electron-hole-pair damping has previously been assigned dominance.To measure vibrational relaxation times, a resonant infrared pulse populates the first excited state of the symmetric C-H stretching mode at 2918 cm -1 . The subsequent population relaxation is monitored by transient sum-frequency-generation (SFG) spectroscopy. 3 In this method, an SFG signal is generated by mixing a visible probe pulse with a vibrationally resonant infrared probe pulse at the surface. The vibrationally resonant SFG signal is proportional to the square of the population difference between the lower and upper levels of the transition probed. 3 Its square root is therefore a measure of the population difference on the vibrational transition. If So is the SFG signal with no pump and S(r^) is the signal at delay r after the pump, 1 -[Sir^)] ,/2 /v^o is then analogous to a transient absorption probe at resonance; 4 this normalized difference of square roots is proportional to the pump-induced change in the population difference, which is dependent on the probe delay. This description assumes the excited-level absorption is shifted by anharmonicity, so that it does not interfere with the ground-state probe. In the present case, the shift of the excited-state absorption of the symmetric C-H stretching mode is 50-100 cm" 1 , well outside the probe-pulse bandwidth.Visible pulses with 4-ps duration (5-cm -1 bandwidth) and infrared pulses of 3-ps duration (6-cm -1 bandwidth) are generated in a picosecond laser system, as previously described. 3 The infrared pulses...
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