A fast-Fourier-transform method of topography and interferometry is proposed. By computer processing of a noncontour type of fringe pattern, automatic discrimination is achieved between elevation and depression of the object or wave-front form, which has not been possible by the fringe-contour-generation techniques. The method has advantages over moire topography and conventional fringe-contour interferometry in both accuracy and sensitivity. Unlike fringe-scanning techniques, the method is easy to apply because it uses no moving components.

Fourier-transform method of fringe-pattern analysis for computer-based topography and interferometry

Summary form only given. Fundamental processes in atoms, molecules, as well as condensed matter are triggered or mediated by the motion of electrons inside or between atoms. Electronic dynamics on atomic length scales tends to unfold within tens to thousands of attoseconds (1 attosecond [as] = 10-18 s). Recent breakthroughs in laser science are now opening the door to watching and controlling these hitherto inaccessible microscopic dynamics. The key to accessing the attosecond time domain is the control of the electric field of (visible) light, which varies its strength and direction within less than a femtosecond (1 femtosecond = 1000 attoseconds). Atoms exposed to a few oscillations cycles of intense laser light are able to emit a single extreme ultraviolet (XUV) burst lasting less than one femtosecond. Full control of the evolution of the electromagnetic field in laser pulses comprising a few wave cycles have recently allowed the reproducible generation and measurement of isolated sub-femtosecond XUV pulses, demonstrating the control of microscopic processes (electron motion and photon emission) on an attosecond time scale. These tools have enabled us to visualize the oscillating electric field of visible light with an attosecond "oscilloscope", to control single-electron and probe multi-electron dynamics in atoms, molecules and solids. Recent experiments hold promise for the development of an attosecond X-ray source, which may pave the way towards 4D electron imaging with sub-atomic resolution in space and time.

Attosecond Physics

A few-layer MoS2 photodetector driven by poly(vinylidene fluoride-trifluoroethylene) ferroelectrics is achieved. The detectivity and responsitivity are up to 2.2 × 10(12) Jones and 2570 A W(-1), respectively, at 635 nm with ZERO gate bias. E(g) of MoS2 is tuned by the ultrahigh electrostatic field from the ferroelectric polarization. The photoresponse wavelengths of the photodetector are extended into the near-infrared (0.85-1.55 μm).

Ultrasensitive and Broadband MoS2 Photodetector Driven by Ferroelectrics

Organic molecules and semiconductors have been proposed as active part of a large variety of nonvolatile memory devices, including resistors, diodes and transistors. In this review, we focus on electrically reprogrammable nonvolatile memories. We classify several possible devices according to their operation principle and critically review the role of the π-conjugated materials in the device operation. We propose specifications for applications for organic nonvolatile memory and review the state of the art with respect to these target specifications. Conclusions are drawn regarding further work on materials and device architectures.

Polymer and Organic Nonvolatile Memory Devices

Ultrafast optics has undergone a revolution in the past two decades, driven by new
methods of pulse generation, amplification, manipulation, and measurement. We review
the advances made in the latter field over this period, indicating the general
principles involved, how these have been implemented in various experimental
approaches, and how the most popular methods encode the temporal electric field of a
short optical pulse in the measured signal and extract the field from the data.

Characterization of ultrashort electromagnetic pulses

Highly efficient high-harmonic generation was achieved in helium using a two-color laser field that consisted of the fundamental and the second harmonic fields of a femtosecond Ti:sapphire laser. By applying a high intensity second harmonic, the harmonics generated in the orthogonally polarized two-color field were stronger than those obtained in the fundamental field by more than 2 orders of magnitude, and even stronger than those of the parallel polarization case. A conversion efficiency as high as $5\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}5}$ was obtained for the 38th harmonic at 21.6 nm. The physical origin of this enhancement was deduced by analyzing the electron behavior in the two-color field.

Highly Efficient High-Harmonic Generation in an Orthogonally Polarized Two-Color Laser Field

We have achieved very efficient high-harmonic generation in a two-color laser field using a long gas jet of He. With the optimization of laser parameters and target conditions, strong harmonics were produced at 2(2n+1)th orders in an orthogonally polarized two-color field. The strongest harmonic at the 38th order (21.6nm) reached an energy of 0.6μJ with a 6mm gas jet, giving a conversion efficiency as high as 2×10−4.

Generation of submicrojoule high harmonics using a long gas jet in a two-color laser field

Brightness of high-order harmonics is optimized in the space domain by profile flattening and self-guiding of intense femtosecond laser pulse and in the time domain by controlling the laser chirp. The profile flattening and self-guiding of the laser pulse propagating through a long gas jet effectively increased the phase-matched harmonic generation volume, thereby obtaining strong harmonics with low beam divergence, and the laser chirp control allowed the generation of spectrally sharp harmonics. At optimized conditions, the $61\text{st}$ harmonic, obtained at $134\phantom{\rule{0.3em}{0ex}}\mathrm{\AA{}}$ from Ne, had a brightness of about $1\ifmmode\times\else\texttimes\fi{}{10}^{15}\phantom{\rule{0.3em}{0ex}}\mathrm{W}∕{\text{cm}}^{2}∕\text{srad}$ with a beam divergence of 0.5 mrad and a spectral bandwidth of $0.7\phantom{\rule{0.3em}{0ex}}\mathrm{\AA{}}$.

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Optimization of high-order harmonic brightness in the space and time domains

PURPOSE: An apparatus for optically combining visible light images and far-infrared images is provided to remove a fusion process of using a DSP(digital signal processor) CONSTITUTION: An apparatus for optically combining visible light images and far-infrared images comprises the following: an inner light source(207) radiating a light in a wavelength band which can be detected by an image sensor(203); a splitter(201) dividing the light radiated from a subject into visible rays and far infrared rays; and a micro cantilever(206) detecting the far infrared rays divided from the splitter to reflect the light from the inner light source to the image sensor while including a far infrared receptor, a bimetal, and a reflecting plate

Apparatus for combining visible images and far-infrared images optically

Optical pulses with 1.1-mJ energy and 5.5-fs duration have been generated at 1-kHz repetition rate from a chirped pulse amplification Ti:Sapphire laser incorporating a differentially pumped hollow-fiber chirped-mirror compressor. The effects of self-focusing and multi-photon ionization during the beam propagation were minimized by differentially pumping the hollow fiber filled with neon. The spectral broadening at the hollow-fiber compressor was optimized by adjusting gas pressure, laser intensity, and laser chirp, covering from 540 nm to 950 nm.

Yong Soo Lee

Papers

Highly Efficient High-Harmonic Generation in an Orthogonally Polarized Two-Color Laser Field

Generation of submicrojoule high harmonics using a long gas jet in a two-color laser field

Optimization of high-order harmonic brightness in the space and time domains

Apparatus for combining visible images and far-infrared images optically

Generation of 0.2-TW 5.5-fs optical pulses at 1 kHz using a differentially pumped hollow-fiber chirped-mirror compressor