KEYWORDS: Optical storage, Sensors, 3D optical data storage, Luminescence, Servomechanisms, Data storage, Magnetism, Absorption, Signal processing, Signal to noise ratio
Three-dimensional parallel readout of 2-photon multilayer optical disks can simultaneously offer high capacities (greater than 100 GB/disk) and high data transfer rates (greater than 1 Gb/s). The robust system tolerances should enable cost effective storage systems with capacities and transfer rates that are scaleable to match various application requirements.
KEYWORDS: Optical storage, Data storage, Absorption, Polymers, Luminescence, Signal to noise ratio, Virtual reality, Video, Digital video discs, Digital recording
The generation and application of information is rapidly evolving from text and graphics based to multimedia based, and it will shortly continue to evolve to virtual reality. The evolution between these stages introduces dramatic increases in the amount of data associated with the applications. For example, where text-based meeting notes have given way to emailed copies of vugraphs, future meeting documentation may require storing and communicating an entire collaborative virtual reality session. Even in the near term, the need to store, search for, and edit large numbers of images and digital video clips will drive data storage requirements forward in home, office, and network arenas, as shown in Fre 1 .
Highly focused pulsed laser microbeams can be used to precisely dissect, inactivate, or perturb cells and subcellular targets. Here we introduce a new technique which employs pulsed microbeams to transiently permeabilize the plasma cell membrane and affect the delivery of molecules from the extracellular environment into the cell. This optically produced cell permeabilization can be applied using non- specific or specific modalities. In the non-specific modality, which we term 'optoporation,' the pulsed microbeam is focused onto the glass coverslip on which the cells are plated. The generation of mechanical transients in connection with irradiation of the glass achieves molecular delivery to a number of cells proximal to the irradiation site. In the specific modality, termed 'optoinjection,' the microbeam is focused directly onto the plasma cell membrane and achieves molecular delivery into that cell alone. To quantify the irradiation geometry involved in these and other microbeam processes, as well as examine the possibility of certain non- linear effects, we have developed a system using photochromic polymer films to characterize microbeam propagation and its effects within microirradiated targets. These photochromic polymers confirm that the laser microbeam are indeed focused to submicron dimensions within the targets in our systems. In addition the behavior of such polymers at higher pulse energies and irradiances indicate that multiphoton absorption and/or plasma formation may mediate some laser microirradiation processes.
Microthermometric measurements on optically-trapped Chinese Hamster Ovary (CHO) cells and sperms cells re reported, using a noninvasive microfluorometric detection technique. Within an optical tweezer system that has been outfitted with a spectral fluorescence excitation and detection capability, the changes in temperature induced by the process of sample confinement by a focused laser beam has been quantified over micron-sized spatial regions of both motile and immotile cells. Our measurement technique is based on the use of environmentally sensitive fluorophores that can be incorporated into the cell membrane and used to sense local changes in temperature when the cell membrane is perturbed optically or via other environmental stress factors. Using a cw 1.064 micrometers Nd:YAG laser for trapping CHO and human sperm cells, a temperature increase of approximately equals 1°C per 100 mW laser power was observed. At this infrared wavelength, cellular heating as result of laser confinement appears to be mainly due to radiation absorption by water.
A free-electron laser (FEL) microscope has been constructed to perform spatially and spectrally resolved pump/probe experiments in single living cells. Picosecond infrared FEL pulses are absorbed by the sample and rapidly converted to heat. Excitation of localized fluorescent reporter molecules using a UV/VIS probe beam leads to thermally induced alterations in the radiative signal. Fluorescence-detected infrared (FDIR) spectra are generated from regions proximal to reporter molecules by varying the FEL pump wavelength. Sub- wavelength spatial resolution is a composite function of media thermal properties and probe selectivity.
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