Recent advances now permit the use of scanning acoustic microscopy for the analysis of subcellular components. By sequential viewing of identified fixed cells with acoustic, light, and electron microscopy, we have established that the acoustic microscope can readily detect such features as nuclei and nucleoli, mitochondria, and actin cables. Under optimal conditions, images can even be obtained of filopodia, slender projections of the cell surface that are approximately 0.1-0.2 Jim in diameter. Small objects separated by as little as 0.5-0.7 jum can successfully be resolved. Three aspects of the acoustic micrographs prepared in this preliminary survey seem especially prominent. These are, first, the extraordinary level of acoustic contrast that can differentiate the various cytoplasmic organelles, even in regions of very thin cytoplasm; second, the reversals in acoustic contrast that occur when altering the plane of focus; and third, the sensitivity of the acoustic response to overall cytoplasmic thickness. The acoustic microscope uses a novel source of contrast that is based on local mechanical properties. In addition, it can provide a degree of resolution that is comparable to that of the light microscope.Much of our current understanding of cellular structure and function has been gained through the application of a variety of microscopic techniques. With light microscopy, advances in the methods of fixation and staining [for example, the recent development of immunofluorescence microscopy (see ref.1)] and in optical systems [for example, phase contrast (2), Nomarski (3), Hoffman modulation (4), and polarized light microscopy (5)] have permitted major increases in knowledge about both living and fixed biological material. The electron microscope, in both the transmission and scanning modes, has of course greatly extended our understanding of the fine structure of nonliving preparations.We now report the application of a novel type of microscopy, acoustic microscopy, to the analysis of subcellular components. We compare images obtained in the acoustic microscope with images of the same cells obtained by light and electron microscopy. This report is an update of an earlier paper (6), in which the visualization of single cells with the scanning acoustic microscope was first described. Since then, advances in acoustic technology have permitted major increases in resolution to a level now comparable to that of light microscopy (7). The impetus toward development of the acoustic microscope rests on the unique method of analysis, the use of high-frequency sound waves. The properties detected by acoustic radiation are different from those detected by either light or electron radiation, and present exciting possibilities for the examination, in a fundamentally new way, of biological material. THE ACOUSTIC MICROSCOPEThe scanning acoustic microscope used in this study was introduced in 1974 by Lemons and Quate (8). The basic functioning of the device as used in the reflection mode can be understood with the aid ...

Recent advances in the field of acoustic microscopy have allowed the instrument to be operated at wavelengths that correspond to the center of the optical band. Experimental results in the form of acoustic micrographs are presented and compared to their optical counterparts. It is apparent that the resolving power of the instrument is similar to that of the optical microscope. Also it is seen that the acoustic micrographs yield information on the subsurface region. This information is not available in the optical images.

There is current interest in developing optical storage materials that can be written with GaAlAs lasers. Dyes which absorb strongly at those wavelengths are potential candidates for this application due to their attractive thermal properties. Through optical and thermal modelling, the properties that are necessary if they are to be writeable at energies of ?1 nJ are examined. A specific class of infrared absorbing dyes, squarylium, is discussed and preliminary data on optical characteristics, writing energy, and stability are presented.

We have modified a transmission acoustic microscope by replacing the input lens with an optical counterpart. The input to this system comes from a mode-locked and Q-switched Nd : YAG laser at 1.06 μm. Acoustic signals arising from thermoelastic coupling are generated in metallic films at frequencies determined by the modulation envelope of the optical beam. The output acoustic lens and transducer responsive to sound waves at 840 MHz detect the acoustic energy which comes from the heated volume (∼2-μm diameter) near the focal region. The sample is mechanically scanned through the focal point in a raster pattern to record the photoacoustic images. We suggest this as a method for collecting new information on microscopic structures.

We demonstrate for the first time that Te87Ge8Sn5 films, which are amorphous as deposited, can be optically switched between the crystalline and amorphous states more than 106 times. The measured reflectivity changed from 40% to 60% and the transmission changed from 3% to 1.5%, respectively, between the amorphous and crystalline states. The crystallization temperature of the cycled spots is ≊75 °C and these spots are observable after >20 weeks. It is found that the crystallization temperature of cycled spots is typically about 20 °C lower than that of the unwritten film. Increasing the Ge concentration leads to increased crystallization temperature and increased minimum crystallization time without affecting reversibility.