Aaron Lewis

Mounting for X-ray capillary

Cantilevered glass structures for nanodelivery of chemicals

Dielectric Properties of the bR Membrane

The Journal of Physical Chemistry B, 2003

The application of dielectric spectroscopy (DS) to the study of bacteriorhodopsin (bR)-containing... more The application of dielectric spectroscopy (DS) to the study of bacteriorhodopsin (bR)-containing purple membrane films is presented in this paper. Two types of bR membrane films, oriented and nonoriented, were investigated in a wide frequency range (10 -2 -3 × 10 9 Hz) and temperature interval (5-70°C). Four relaxation processes were observed in this frequency range and ascribed to different mechanisms, related to the structural units of the system. A large nonreversibility of the dielectric response as a result of heating and cooling has been observed in the slow processes implicating a change in the structure of the membrane stacking depending on the history of cooling and heating of the sample. Significant changes as large as 3 orders of magnitude in the mobility have been observed in this time scale. Comparison of the oriented and nonoriented bR membrane films was performed, and it was found that the oriented purple membrane has a unique liquid crystal-like ferroelectric behavior.

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Second harmonic generation from Langmuir-Blodgett films of retinal and retinal Schiff bases

The Journal of Physical Chemistry, 1988

Several spectroscopic techniques&amp;amp;amp;amp;#x27; have been applied to investigate the p... more

Tunable Laser Resonance Raman Spectroscopy in Biology

Spectroscopy in Biology and Chemistry, 1974

Near-field optical imaging of unstained bacteria: comparison with normal atomic force and far-field optical microscopy in air and aqueous media

Ultramicroscopy, 1998

Simultaneous near-field scanning optical and atomic force imaging of bacteria is presented. The b... more Simultaneous near-field scanning optical and atomic force imaging of bacteria is presented. The bacteria imaged in these studies were unstained. The near-field optical images had excellent signal-to-noise and showed excellent contrast even in these unstained specimens. The images obtained were interpreted in terms of the images that have been obtained by transmission electron microscopy and X-ray imaging. The results show that bacterial near-field optical imaging is going to be a very important tool in the arsenal of the bacteriologist both in terms of understanding the fundamental processes in the life cycle of bacteria with and without cytochemical staining and in terms of clinical diagnostic applications.

Investigating material and functional properties of static random access memories using cantilevered glass multiple-wire force-sensing thermal probes

by E. Khachatryan, Aaron Lewis, and Klony Lieberman

Applied Physics Letters, 2000

A double-wire cantilevered glass probe has been produced for scanned probe microthermal, resistiv... more

The optical near-field: super-resolution imaging with structural and phase correlation

Nanophotonics, 2014

An overview of near-field optics is presented with a focus on the fundamental advances that have ... more An overview of near-field optics is presented with a focus on the fundamental advances that have been made in the field since its inception 30 years ago. A focus is placed on the advancements that have been achieved in instrumentation. These advances have led to a greater generality of use with ultra-low mechanical and optical noise and the ultimate in force sensitivity with near-field optical probes. An emphasis is placed on the importance of fully integrating near-field optics with other imaging and spectroscopic modalities including Raman spectroscopy and electron/ion beam imaging. Important directions in probe design, force feedback methods and scanner flexibility are described. These developing avenues provide considerable optimism for an ever increasing incorporation of near-field optics to help resolve critical problems in fundamental and applied science.

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New design and imaging concepts in NSOM

Ultramicroscopy, 1995

... ELSEVIER Ultramicroscopy 61 (1995) 215220 ultramicroscopy New design and imaging concepts in ... more

Observation of Liquid-Crystal-Like Ferroelectric Behavior in a Biological Membrane

The Journal of Physical Chemistry B, 2001

In this contribution, we report the application of time domain dielectric spectroscopy from 500 k... more In this contribution, we report the application of time domain dielectric spectroscopy from 500 kHz to 1 GHz and differential scanning calorimetry to bacteriorhodopsin containing purple membrane films. The results of these measurements unexpectedly show that the oriented purple membrane has a unique liquid-crystal-like ferroelectric behavior. The dielectric behavior can be considered as soft mode relaxation processes in ferroelectric liquid crystals near smectic-C*-smectic-A phase transition. Such a phenomenon has not been previously observed in biological systems.

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d -Glucose-Induced Second Harmonic Generation Response in Human Erythrocytes

The Journal of Physical Chemistry B, 2009

The first experimental results of the nonresonant second harmonic generation (SHG) studies of hum... more The first experimental results of the nonresonant second harmonic generation (SHG) studies of human erythrocytes membrane exposed to various glucose concentrations in phosphate buffered saline (PBS solution) are presented in this article. It is shown that the SHG signal from the membrane can be altered as a function of glucose concentration. The link between the variation of the SHG intensity and the membrane dielectric permittivity with glucose is established both theoretically and experimentally by comparison with time domain dielectric spectroscopy (TDDS) measurement data.

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NSOM the fourth dimension: Integrating nanometric spatial and femtosecond time resolution

Scanning, 2006

... One emulation of this technology for producing a near-field optical element is a metal-coated... more

A micropipette force probe suitable for near-field scanning optical microscopy

Review of Scientific Instruments, 1992

Abstract In this paper it is demonstrated that glass micropipettes have unique applicability as f... more

Tunable Laser Resonance Raman Spectroscopy of Bacteriorhodopsin

Proceedings of the National Academy of Sciences, 1974

Bacteriorhodopsin is a rhodopsin-like protein found in the cell membrane of Halobacterium halobiu... more Bacteriorhodopsin is a rhodopsin-like protein found in the cell membrane of Halobacterium halobium. It shows an absorption maximum at 570 nm and, in the light, undergoes cyclic spectral changes which include a relatively long-lived complex absorbing maximally at 412 nm. Excitation profiles have been obtained with several laser frequencies for two vibrations in the resonance Raman spectrum of bacteriorhodopsin. The results show that the Schiff base retinylidene lysine linkage is protonated in the 570 nm complex and that in the 412 nm complex it is unprotonated. The 412 nm complex must be present at appreciable concentrations when bacteriorhodopsin is exposed to high-energy argon ion laser light of the Raman spectrophotometer at room temperature. We conclude that the observed C=N stretch at 1622 cm(-1) in the room temperature spectra, which in an earlier study by Mendelsohn was interpreted as evidence for an unprotonated linkage in bacteriorhodopsin, results from the presence of the 412 nm complex.

Saturable absorption, wave mixing, and phase conjugation with bacteriorhodopsin

Optics Letters, 1990

Bacteriorhodopsin exhibits strong nonlinear and saturation behavior with very low light intensiti... more

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Strong self-defocusing effect and four-wave mixing in bacteriorhodopsin films

by Aaron Lewis and B. Fischer

Optics Letters, 1992

We find strong self-defocusing in bacteriorhodopsin films in the near IR with powers in the tens ... more We find strong self-defocusing in bacteriorhodopsin films in the near IR with powers in the tens of milliwatts. The defocused beam acquires a ring pattern because of spatial self-phase modulation. We also demonstrate efficient four-wave mixing with phase-conjugate reflectivities of 26%. We discuss the origin of this high nonlinearity.

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Direct measurement of the voltage sensitivity of second-harmonic generation from a membrane dye in patch-clamped cells

Optics Letters, 2003

We report what is to our knowledge the first optical imaging of voltage-clamped cells by second-h... more We report what is to our knowledge the first optical imaging of voltage-clamped cells by second-harmonic generation. For the membrane-staining styryl dye di-4-ANEPPS, we determined the sensitivity of second-harmonic generation to be 18%/100 mV at an excitation wavelength of 850 ns. This sensitivity is significantly better than the optimal 10%/100 mV under fluorescence and further establishes the importance of second-harmonic generation for the functional imaging of membrane potential in living cells.

Near-field characterization of extraordinary optical transmission in sub-wavelength aperture arrays

Optics Express, 2007

Extra ordinary transmission through arrays of subwavelength apertures has been investigated using... more Extra ordinary transmission through arrays of subwavelength apertures has been investigated using near-field scanning optical microscopy. For such studies arrays were fabricated to give maximum resonance enhancement of light transmission at the wavelength of illumination that was used (532 nm). To define this enhancement a design was employed that allowed in one field of view of a near-field image the investigation of single apertures of dimension that was similar to what was incorporated into the sub-wavelength hole array. Significant asymmetry in the transmission and the propagation of the light along the aperture array was detected. This non-uniformity could be explained by polarization of the incident light, edge effects and the geometry of the array. The results support a hypothesis of both enhanced transmission due to surface plasmons and a non-diffracting beaming as a function of distance effect in the propagation of the light from the array.

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Forward phase conjugation by three-wave mixing with bacteriorhodopsin

Optics Communications, 1992

... Electrical Engineering, Advanced Opto-Electronics Center, The Technion-Israel Institute of Te... more

Submicron concentration and confinement of hard X-rays

Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 1992

High-intensity hard X-ray beams of submicron diameters were generated using a tapered glass capil... more

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