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Type: article × Publisher: Bristol : IOP Publ. × Subject: Nanostructures ×

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Now showing 1 - 5 of 5
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    Terahertz emission from lithium doped silicon under continuous wave interband optical excitation
    (Bristol : IOP Publ., 2015) Andrianov, A.V.; Zakhar'in, A.O.; Zhukavin, R.K.; Shastin, V.N.; Abrosimov, N.V.
    We report on experimental observation and study of terahertz emission from lithium doped silicon crystals under continuous wave band-to-band optical excitation. It is shown that radiative transitions of electrons from 2P excited states of lithium donor to the 1S(A1) donor ground state prevail in the emission spectrum. The terahertz emission occurs due to capture of nonequilibrium electrons to charged donors, which in turn are generated in the crystal as a result of impurity assisted electron-hole recombination. Besides the intracentre radiative transitions the terahertz emission spectrum exhibits also features at about 12.7 and 15.27 meV, which could be related to intraexciton transitions and transitions from the continuum to the free exciton ground state.
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    The new ultra high-speed all-optical coherent streak-camera
    (Bristol : IOP Publ., 2015) Arkhipov, R.M.; Arkhipov, M.V.; Egorov, V.S.; Chekhonin, I.A.; Chekhonin, M.A.; Bagayev, S.N.
    In the present paper a new type of ultra high-speed all-optical coherent streak-camera was developed. It was shown that a thin resonant film (quantum dots or molecules) could radiate the angular sequence of delayed ultra-short pulses if a transverse spatial periodic distribution of the laser pump field amplitude has a triangle shape.
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    Process flow to integrate nanostructures on silicon grass in surface micromachined systems
    (Bristol : IOP Publ., 2016) Mehner, H.; Müller, L.; Biermann, S.; Hänschke, F.; Hoffmann, M.
    The process flow to integrate metallic nanostructures in surface micromachining processes is presented. The nanostructures are generated by evaporation of microstructured silicon grass with metal. The process flow is based on the lift-off of a thin amorphous silicon layer deposited using a CVD process. All steps feature a low temperature load beneath 120 °C and high compatibility with many materials as only well-established chemicals are used. As a result metallic nanostructures usable for optical applications can be generated as part of multilayered microsystems fabricated in surface micromachining.
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    Subwavelength population density gratings in resonant medium created by few-cycle pulses
    (Bristol : IOP Publ., 2017) Arkhipov, R.M.; Arkhipov, M.V.; Pakhomov, A.V.; Babushkin, I.; Demircan, A.; Morgner, U.; Rosanov, N.N.
    We consider theoretically recently proposed a new possibility of creation, erasing and ultrafast control of population density grating. Such grating can be created in resonant medium when ultrashort pulses with duration smaller than relaxation times in the resonant medium (coherent light matter interactions) propagate without overlapping in this medium. Possible applications in the ultrafast optics such as optical switcher and laser beam deflector are discussed.
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    Towards a life-time-limited 8-octave-infrared photoconductive germanium detector
    (Bristol : IOP Publ., 2015) Pavlov, S.G.; Deßmann, N.; Pohl, A.; Abrosimov, N.V.; Mittendorff, M.; Winnerl, S.; Zhukavin, R.K; Tsyplenkov, V.V.; Shengurov, D.V.; Shastin, V.N.; Hübers, H.-W.
    Ultrafast, ultra-broad-band photoconductive detector based on heavily doped and highly compensated germanium has been demonstrated. Such a material demonstrates optical sensitivity in the more than 8 octaves, in the infrared, from about 2 mm to about 8 μm. The spectral sensitivity peaks up between 2 THz and 2.5 THz and is slowly reduced towards lower and higher frequencies. The life times of free electrons/holes measured by a pump-probe technique approach a few tenths of picoseconds and remain almost independent on the optical input intensity and on the temperature of a detector in the operation range. During operation, a detector is cooled down to liquid helium temperature but has been approved to detect, with a reduced sensitivity, up to liquid nitrogen temperature. The response time is shorter than 200 ps that is significantly faster than previously reported times.