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6 Publications

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    08/01/92 | Polarization contrast in near-field scanning optical microscopy.
    Betzig E, Trautman JK, Weiner JS, Harris TD, Wolfe R
    Applied Optics. 1992 Aug 1;31(22):4563-8. doi: 10.1364/AO.31.004563

    Recent advances in probe design have led to enhanced resolution (currently as significant as   12 nm) in optical microscopes based on near-field imaging. We demonstrate that the polarization of emitted and detected light in such microscopes can be manipulated sensitively to generate contrast. We show that the contrast on certain patterns is consistent with a simple interpretation of the requisite boundary conditions, whereas in other cases a more complicated interaction between the probe and the sample is involved. Finally application of the technique to near-filed magneto-optic imaging is demonstrated.

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    07/10/92 | Near-field optics: microscopy, spectroscopy, and surface modification beyond the diffraction limit. (With commentary)
    Betzig E, Trautman JK
    Science. 1992 Jul 10;257(5067):189-95. doi: 10.1126/science.257.5067.189

    The near-field optical interaction between a sharp probe and a sample of interest can be exploited to image, spectroscopically probe, or modify surfaces at a resolution (down to approximately 12 nm) inaccessible by traditional far-field techniques. Many of the attractive features of conventional optics are retained, including noninvasiveness, reliability, and low cost. In addition, most optical contrast mechanisms can be extended to the near-field regime, resulting in a technique of considerable versatility. This versatility is demonstrated by several examples, such as the imaging of nanometric-scale features in mammalian tissue sections and the creation of ultrasmall, magneto-optic domains having implications for highdensity data storage. Although the technique may find uses in many diverse fields, two of the most exciting possibilities are localized optical spectroscopy of semiconductors and the fluorescence imaging of living cells.

    Commentary: An overview of our work in near-field optics at the time, after our invention of the adiabatically tapered fiber probe and shear force feedback (see below) led to the first practical near-field scanning optical microscope. In this work, superresolution imaging via absorption, reflectivity, fluorescence, spectroscopy, polarization, and refractive index contrast were all demonstrated. Unlike all far-field superresolution fluorescence methods that were to appear a decade later, near-field microscopy remains the only superresolution technique capable of taking advantage of the full panoply of optical contrast mechanisms.

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    06/12/92 | The argos gene encodes a diffusible factor that regulates cell fate decisions in the Drosophila eye.
    Freeman M, Klämbt C, Goodman CS, Rubin GM
    Cell. 1992 Jun 12;69(6):963-75. doi: 10.1186/gb-2007-8-7-r145

    The argos gene encodes a protein that is required for viability and that regulates the determination of cells in the Drosophila eye. A developmental analysis of argos mutant eyes indicates that the mystery cells, which are usually nonneuronal, are transformed into extra photoreceptors, and that supernumerary cone cells and pigment cells are also recruited. Clonal analysis indicates that argos acts nonautonomously and can diffuse over the range of several cell diameters. Conceptual translation of the argos gene suggests that it encodes a secreted protein.

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    03/09/92 | Combined shear force and near-field scanning optical microscopy (With commentary)
    Betzig E, Finn PL, Weiner JS
    Applied Physics Letters. 1002 Mar 9;60:

    A distance regulation method has been developed to enhance the reliability, versatility, and ease of use of near-field scanning optical microscopy (NSOM). The method relies on the detection of shear forces between the end of a near-field probe and the sample of interest. The system can be used solely for distance regulation in NSOM, for simultaneous shear force and near-field imaging, or for shear force microscopy alone. In the latter case, uncoated optical fiber probes are found to yield images with consistently high resolution.

    Commentary: To exploit the evanescent field that is the source of high resolution in near-field microscopy, the probe must be exceptionally close to the sample:  10 nm away for 30-50 nm resolution. Here we introduced a distance regulation mechanism based on transverse shear forces between the end of a dithered near-field probe and the sample, which permitted even samples of modest topography to be imaged. Simple, reliable, noninvasive, and applicable to a wide range of samples from whole fixed cells to semiconductor devices, shear force microscopy was a key enabling technology for near-field optics, and soon widely implemented.

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    03/06/92 | Perforated patch-clamp analysis of the passive membrane properties of three classes of hippocampal neurons.
    Spruston N, Johnston D
    J Neurophysiol. 1992 Mar;67(3):508-29

    1. Perforated patch-clamp recordings were made from the three major classes of hippocampal neurons in conventional in vitro slices prepared from adult guinea pigs. This technique provided experimental estimates of passive membrane properties (input resistance, RN, and membrane time constant, tau m) determined in the absence of the leak conductance associated with microelectrode impalement or the washout of cytoplasmic constituents associated with conventional whole-cell recordings. 2. To facilitate comparison of our data with previous results and to determine the passive membrane properties under conditions as physiological as possible, recordings were made at the resting potential, in physiological saline, and without any added blockers of voltage-dependent conductances. 3. Membrane-potential responses to current steps were analyzed, and four criteria were used to identify voltage responses that were the least affected by activation of voltage-dependent conductances. tau m was estimated from the slowest component (tau 0) of multiexponential fits of responses deemed passive by these criteria. RN was estimated from the slope of the linear region in the hyperpolarizing direction of the voltage-current relation. 4. It was not possible to measure purely passive membrane properties that were completely independent of membrane potential in any of the three classes of hippocampal neurons. Changing the membrane potential by constant current injection resulted in changes in RN and tau 0; subthreshold depolarization produced an increase, and hyperpolarization a decrease, in both RN and tau 0 for all three classes of hippocampal neurons. 5. Each of the three classes of hippocampal neurons also displayed a depolarizing "sag" during larger hyperpolarizing voltage transients. To evaluate the effect of the conductances underlying this sag on passive membrane properties, 2-5 mM Cs+ was added to the physiological saline. Extracellular Cs+ effectively blocked the sag in all three classes of hippocampal neurons, but the effect of Cs+ on RN, tau 0, and the voltage dependence of these parameters was unique for each class of neurons. 6. CA1 pyramidal neurons had an RN of 104 +/- 10 (SE) M omega and tau 0 of 28 +/- 2 ms at a resting potential of -64 +/- 2 mV (n = 12). RN and tau 0 were larger at more depolarized potentials in these neurons, but the addition of Cs+ to the physiological saline reversed this voltage dependence. 7. CA3 pyramidal neurons had an RN of 135 +/- 8 M omega and tau 0 of 66 +/- 4 ms at a resting potential of -64 +/- 1 mV (n = 14).(ABSTRACT TRUNCATED AT 400 WORDS)

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    01/01/92 | Near-field magneto-optics and high density data storage. (With commentary)
    Betzig E, Trautman JK, Wolfe R, Gyorgy EM, Finn PL, Kryder MH, Chang CH
    Applied Physics Letters.. 1992;61:

    Near-field scanning optical microscopy (NSOM) has been used to image and record domains in thin-film magneto-optic (MO) materials. In the imaging mode, resolution of 30-50 nm has been consistently obtained, whereas in the recording mode, domains down to -60 nm have been written reproducibly. Data densities of -45 Gbits/in.’ have been achieved, well in excess of current magnetic or MO technologies. A brief analysis of speed and other issues indicates that the technique may represent a viable alternative to density data storage needs.

    Commentary: The first demonstration of optical recording and playback beyond the diffraction limit, using magneto-optic multilayer films and polarization contrast near-field microscopy. Bits as small as 60 nm were recorded – beyond estimates at the time of the superparamagnetic limit to bit stability. Bit densities of 45 Gbits/in2 were also achieved, well in excess of optical or magnetic recording technologies of the era. In the years following this work, massive resources were spent on the commercialization of near-field data storage, largely for naught.

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