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Journal ArticleDOI

Picosecond optoelectronic switching and gating in silicon

01 Feb 1975-Applied Physics Letters (American Institute of Physics)-Vol. 26, Iss: 3, pp 101-103
TL;DR: In this paper, the authors measured the switching speed of two transmission gates in tandem, each having an aperture time of 15 psec, by correlating the response of two transceivers in tandem.
Abstract: Quasimetallic photoconductivity produced by the absorption of picosecond optical pulses in silicon transmission line structures has been used to devise electronic switches and gates which can be turned on and off in a few picoseconds. Electrical signals as large as 100 V can be switched by a few microjoules of optical energy. The switching speed was measured by correlating the response of two transmission gates in tandem, each having an aperture time of 15 psec.
Citations
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Journal ArticleDOI
TL;DR: In this paper, the development of terahertz (THz) technology and a typical system used in biomedical applications is described, considering applications ranging from THz spectroscopy of crystalline drugs to THz imaging of skin cancer.
Abstract: We review the development of terahertz (THz) technology and describe a typical system used in biomedical applications. By considering where the THz regime lies in the electromagnetic spectrum, we see that THz radiation predominantly excites vibrational modes that are present in water. Thus, water absorption dominates spectroscopy and imaging of soft tissues. However, there are advantages of THz methods that make it attractive for pharmaceutical and clinical applications. In this review, we consider applications ranging from THz spectroscopy of crystalline drugs to THz imaging of skin cancer.

724 citations

Journal ArticleDOI
03 Jan 2013-Nature
TL;DR: The feasibility of electric signal manipulation in a dielectric is reported, opening the way to extending electronic signal processing and high-speed metrology into the petahertz (1015 hertz) domain.
Abstract: Exposing a fused silica sample to a strong, waveform-controlled, few-cycle optical field increases the dielectric’s optical conductivity by more than 18 orders of magnitude in less than 1 femtosecond, allowing electric currents to be driven, directed and switched by the instantaneous light field. Two studies published in this issue highlight the potential for ultrafast signal manipulation in dielectrics using optical fields. When it comes to electrical signal processing, semiconductors have become the materials of choice. However, insulators such as dielectrics could be attractive alternatives: they have a fast response in principle, but usually have extremely low conductivity at low electric fields and break down in large fields. The electronic properties of dielectrics can be controlled with few-cycle laser pulses that permit damage-free exposure of dielectrics to high electric fields. Agustin Schiffrin et al. demonstrate that strong optical laser fields with controlled few-cycle waveforms can reversibly transform a dielectric insulator into a conductor within the optical period (within one femtosecond). Martin Schultze et al. address the crucial issue of ultrafast reversibility, demonstrating that the dielectric can be repeatedly switched 'on' and 'off' with light fields, without degradation. The time it takes to switch on and off electric current determines the rate at which signals can be processed and sampled in modern information technology1,2,3,4. Field-effect transistors1,2,3,5,6 are able to control currents at frequencies of the order of or higher than 100 gigahertz, but electric interconnects may hamper progress towards reaching the terahertz (1012 hertz) range. All-optical injection of currents through interfering photoexcitation pathways7,8,9,10 or photoconductive switching of terahertz transients11,12,13,14,15,16 has made it possible to control electric current on a subpicosecond timescale in semiconductors. Insulators have been deemed unsuitable for both methods, because of the need for either ultraviolet light or strong fields, which induce slow damage or ultrafast breakdown17,18,19,20, respectively. Here we report the feasibility of electric signal manipulation in a dielectric. A few-cycle optical waveform reversibly increases—free from breakdown—the a.c. conductivity of amorphous silicon dioxide (fused silica) by more than 18 orders of magnitude within 1 femtosecond, allowing electric currents to be driven, directed and switched by the instantaneous light field. Our work opens the way to extending electronic signal processing and high-speed metrology into the petahertz (1015 hertz) domain.

615 citations

Journal ArticleDOI
TL;DR: The observation of a light-induced anomalous Hall effect in monolayer graphene driven by a femtosecond pulse of circularly polarized light reveals multiple features that reflect a Floquet-engineered topological band structure similar to the band structure originally proposed by Haldane 10 .
Abstract: Many non-equilibrium phenomena have been discovered or predicted in optically driven quantum solids1. Examples include light-induced superconductivity2,3 and Floquet-engineered topological phases4–8. These are short-lived effects that should lead to measurable changes in electrical transport, which can be characterized using an ultrafast device architecture based on photoconductive switches9. Here, we report the observation of a light-induced anomalous Hall effect in monolayer graphene driven by a femtosecond pulse of circularly polarized light. The dependence of the effect on a gate potential used to tune the Fermi level reveals multiple features that reflect a Floquet-engineered topological band structure4,5, similar to the band structure originally proposed by Haldane10. This includes an approximately 60 meV wide conductance plateau centred at the Dirac point, where a gap of equal magnitude is predicted to open. We find that when the Fermi level lies within this plateau the estimated anomalous Hall conductance saturates around 1.8 ± 0.4 e2/h. A transient topological response in graphene is driven by a short pulse of light. When the Fermi energy is in the predicted band gap the Hall conductance is around two conductance quanta. An ultrafast detection technique enables the measurement.

454 citations

Journal ArticleDOI
26 Sep 2005
TL;DR: The main goal of this paper is to consider some of the most promising THz S&I applications within the specific context of their particular science and technology challenges in an attempt to credibly judge (or speculate on) their future potential.
Abstract: In recent years, the field of terahertz (THz) science and technology has entered a completely new phase of unprecedented expansion that is generating ever growing levels of broad-based international attention. In particular,there have been important advances in state-of-the-art THz technology and very enthusiastic growth in research activities associated with related scientific and industrial applications. One can legitimately argue that the potential payoffs of THz sensing and imaging (THz S&I) to application areas such as defense, security, biology and medicine are the major drivers of this new phenomenon. However, there remain major science and technology "gaps" in the THz regime that must be reconciled before many of the perceived payoffs ever become realizable. Therefore, it is natural to ask the question "Is now the time for THz?" or rather, are these recent events just a repeat of previous cycles in THz overenthusiasm that have been witnessed during the last century? The main goal of this paper is to consider some of the most promising THz S&I applications within the specific context of their particular science and technology challenges in an attempt to credibly judge (or speculate on) their future potential.

437 citations


Cites background from "Picosecond optoelectronic switching..."

  • ...Recent technology development efforts have started to address the previous lack of coherent sources and detectors in the THz range [13], [100], [101], [102] and this is opening up new application areas where the improved THz S&I capabilities now allow for practical advantages....

    [...]

Journal ArticleDOI
TL;DR: A review of pioneering and recent studies of the conductivity of solid state systems at terahertz frequencies can be found in this article, where a variety of theoretical formalisms that describe the tera-hertz conductivities of bulk, mesoscopic and nanoscale materials are outlined, and their validity and limitations are given.
Abstract: We review pioneering and recent studies of the conductivity of solid state systems at terahertz frequencies. A variety of theoretical formalisms that describe the terahertz conductivity of bulk, mesoscopic and nanoscale materials are outlined, and their validity and limitations are given. Experimental highlights are discussed from studies of inorganic semiconductors, organic materials (such as graphene, carbon nanotubes and polymers), metallic films and strongly correlated electron systems including superconductors.

400 citations

References
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Journal ArticleDOI
TL;DR: In this article, the authors report the impedance and attenuation measurements performed on microstrips, which are useful for the microwave and millimeter wave hybrid integrated circuits required for solid-state radio systems because of their simplicity and planar structure.
Abstract: Microstrips, transmission lines of metallic layers deposited on a dielectric substrate, are very useful for the microwave and millimeter wave hybrid integrated circuits required for solid-state radio systems because of their simplicity and planar structure. To design hybrid integrated circuits with microstrips requires computation or measurement of the impedance, the attenuation, the guide wavelength, and the unloaded Q of the line. These parameters can be obtained from the effective dielectric constant and the characteristic impedance of the corresponding air line. This paper gives the exact design data for all line parameters for the most important cases. We report the impedance and attenuation measurements performed on microstrips. Satisfactory agreement is obtained with theoretical results based on conformal mapping with logarithmic derivatives of theta functions and expressions involving the partial derivatives of the impedance with respect to independent line parameters.

520 citations

Journal ArticleDOI
D. H. Auston1, C. V. Shank1
TL;DR: In this article, an ellipsometer was used with picosecond pulses to measure the time evolution of optically generated plasmas in intrinsic Ge. The authors measured the change in optical ellipticity of a weak probe beam following the absorption of an intense excitation pulse, which can be determined with a precision of a few seconds.
Abstract: An ellipsometer has been used with picosecond pulses to measure the time evolution of optically generated plasmas in intrinsic Ge. By measuring the change in optical ellipticity of a weak probe beam following the absorption of an intense excitation pulse, the time evolution of the plasma density can be determined with a precision of a few picoseconds. At a density of 1.7 \ifmmode\times\else\texttimes\fi{} ${10}^{20}$ ${\mathrm{cm}}^{\ensuremath{-}3}$, the ambipolar diffusivity of the plasma was observed to be a factor of 3 greater than the low-density value, consistent with a simple theoretical model of diffusion in the degenerate regime.

137 citations

Journal ArticleDOI
01 Jan 1962
TL;DR: In this paper, the design theory for a new range of p-n junction applications is presented, including pulse generation, wave shaping, and harmonic generation, where the diodes are characterized by a very abrupt interruption of reverse current in the turn-off transient.
Abstract: The design theory for a new range of p-n junction applications is presented. The applications include pulse generation, wave shaping, and harmonic generation. The diodes are characterized by a very abrupt interruption of reverse current in the turn-off transient and are approximately ideal nonlinear capacitors. The abrupt interruption of current in the reverse transient is related to the impurity profile in the junction. An estimate is given of the duration of the abrupt phase. In addition, the role of parasitic elements such as inductance, capacitance, and series resistance is discussed in relation to a particular representative circuit. In typical cases, the abrupt turn-off phase lasts for a time of the order of 10-9 sec. Transitions in excess of 100 v or an ampere are readily obtained.

106 citations