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  • 1
    Digitale Medien
    Digitale Medien
    A simple chemical etching technique for reproducible fabrication of robust scanning near-field fiber probes (1998)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 437-439 
    Details
    ISSN: 1089-7623
    Quelle: AIP Digital Archive
    Thema: Physik , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: A two-step chemical etching procedure has been developed for fabricating probes used by scanning near-field optical microscopy. These probes have two tapered regions which can be reproducibly constructed with a wide range of cone angles. The shape of the probe allows it to be used over sample surfaces with deep and narrow regions. Furthermore, our method can be applied to silica glass fibers which are commercially available. To demonstrate, we used these tips to acquire the near-field optical image of a thin layer of polystyrene spheres. Intensity interference patterns were observed. The demonstrated in-plane resolution was estimated to be about 250 nm. This is mainly limited by the diameter of the metal-coated tip. The transmission efficiency of the tip is better than 10−4. © 1998 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1148678
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  • 2
    Digitale Medien
    Digitale Medien
    Subpicosecond carrier lifetimes in arsenic-ion-implanted GaAs (1995)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 67 (1995), S. 3465-3467 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We have investigated photoexcited carrier lifetimes in arsenic-ion-implanted semi-insulating GaAs by time-resolved reflectivity measurements. Subpicosecond carrier lifetimes (220 to 550 fs) which do not exhibit apparent dosage dependence for samples bombarded with 200 keV arsenic ions at increasing dosages in the range of 1012 and 1016 ions/cm2 are reported. The shortest carrier lifetime was observed for the sample irradiated at 1013 ions/cm−2. These are the shortest lifetimes ever observed for ion-damaged GaAs and comparable to those of low-temperature molecular beam epitaxially grown GaAs, which is also nonstoichiometric with excess-arsenic-related, deep-level defects. © 1995 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.115248
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  • 3
    Digitale Medien
    Digitale Medien
    A thermal phase-locked loop for frequency stabilization of internal-mirror He-Ne lasers (λ=0.633 μm) (1991)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 62 (1991), S. 933-935 
    Details
    ISSN: 1089-7623
    Quelle: AIP Digital Archive
    Thema: Physik , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: A new servo circuit based on the thermal phase-locked loop (TPLL) has been developed for frequency stabilization of internal-mirror He-Ne laser. A feedback signal proportional to the fluctuation in the frequency of the laser is down-converted through a voltage-controlled oscillator (VCO) and compared in a phase/frequency circuit with that of a frequency reference. The detected phase difference then drives a heater wrapped around the laser tube for tuning the laser cavity length. The frequency stability achieved is ±1.0×10−9 over a period of several hours.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1142031
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  • 4
    Digitale Medien
    Digitale Medien
    Nonoptical tip–sample distance control for scanning near-field optical microscopy (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 69 (1996), S. 3312-3314 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We propose and demonstrate a novel nonoptical technique for regulation of tip–sample distance in a scanning near-field optical microscope (SNOM). The fiber tip for the SNOM is attached to one prong of a quartz tuning fork. The fork is dithered with a gated sinusoidal signal. The vibration of the freely oscillating fiber tip, which manifests as the induced piezoelectric voltage on the fork electrodes, is monitored during the half-period of the gated sinusoid for which the fork is not driven. The time-multiplexing scheme, thus, allows the tuning fork to serve as a dither and a sensor with high Q factor, simultaneously. The gating technique could also potentially allow the SNOM to be used for the investigation of surface relaxation dynamics with high spatial resolution and submillisecond time resolution. © 1996 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.117290
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  • 5
    Digitale Medien
    Digitale Medien
    Picosecond responses of low-dosage arsenic-ion-implanted GaAs photoconductors (1997)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 71 (1997), S. 2901-2903 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Ultrafast optoelectronic characteristics of GaAs implanted with 200 keV arsenic ions at dosage as low as 1013 ions/cm2 are reported. Ultrashort photoexcited carrier lifetimes of 0.23±0.02, 0.87±0.02, and 3±0.2 ps were determined for as-implanted, rapid thermal annealing (RTA) (600 °C for 30 s) and furnace-annealed (600 °C for 30 min) arsenic-ion-implanted GaAs or GaAs:As+, respectively. The switching response of photoconductive switches (PCSs) fabricated on the latter two materials were ∼3 and 8 ps, respectively. The leakage current of the PCS fabricated on furnace-annealed sample was as low as 30 nA. The breakdown fields exceeded 150 (instrument-limited) and 90 kV/cm for furnace- and RTA-annealed samples, respectively. The optical responsivity of low-dosage arsenic-implanted GaAs photoconductive switch can be as high as 0.01 A/W. This also compared favorably with the same device made on state-of-the-art photoconductor such as molecular-beam epitaxy grown GaAs at low temperatures. © 1997 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.120210
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  • 6
    Digitale Medien
    Digitale Medien
    Microstructure and subpicosecond photoresponse in GaAs grown by molecular beam epitaxy at very low temperatures (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 69 (1996), S. 397-399 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Cross-sectional transmission electron microscopy (TEM) and femtosecond (fs) reflectivity are used to study (Ga,As) compound grown at low temperatures from 160 to 70 °C. A columnar polycrystalline GaAs is observed for samples grown at 160 °C while it appears amorphous for samples grown at temperatures below 120 °C. The successful growth of amorphous (Ga,As) at 70 °C, instead of a mixture of metallic Ga droplets and As solids, suggests that the decomposition of As4 molecules may be catalyzed by the surface Ga. Upon annealing, all samples become polycrystalline before epitaxial solid state regrowth eventually dominates and the whole sample becomes single crystal for long enough annealing. Carrier lifetime of 230 fs is measured for the as-grown amorphous sample. For the annealed sample, the photoresponse exhibits a fast initial decay of 120 fs and a much slower secondary decay of 33 ps. The initial decay is attributed to the formation of fine polycrystalline grains (∼500 A(ring) in size) whose grain boundaries provide effective carrier traps and recombination centers. © 1996 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.118073
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  • 7
    Digitale Medien
    Digitale Medien
    Effect of rapid thermal annealing on carrier lifetimes of arsenic-ion-implanted GaAs (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 69 (1996), S. 996-998 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Femtosecond time-resolved reflectivity measurements, structural, and electrical analyses have been performed to investigate the effect of rapid thermal annealing (RTA) on GaAs implanted with 200 keV arsenic ions at 1016 ions/cm2. Ultrashort carrier lifetimes from 0.48 fs to 2.3 ps were observed for samples annealed at temperatures between 600 and 800 °C. The time constants are somewhat shorter than those of RTA-annealed low-temperature molecular-beam epitaxy grown material, while following the same trend of longer time constants and recovery of resistance at higher annealing temperatures. Arsenic precipitates were not observed. © 1996 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.117107
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  • 8
    Digitale Medien
    Digitale Medien
    Electrical characterization of arsenic-ion-implanted semi-insulating GaAs by current-voltage measurement (1994)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 65 (1994), S. 3272-3274 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The characteristics of an amorphous GaAs film by implanting dense arsenic ions into semi-insulating GaAs substrate have been studied. The specific contact resistance of the sample at room temperature is found to be 1.1×10−1 Ω cm2. This indicates that the conduction-band electron concentration is less than 1013 cm−3. The activation energy at temperature above 360 K and the density of states are, respectively, 0.6 eV and 1027 m−3 eV−1 as estimated from the slope of Arrhenius plot. Fitting of the Arrhenius plot also suggests that the carrier transport at metal/semiconductor junction of this material below 360 K is dominated by the variable-range hopping conduction mechanism which depends on deep level defects. © 1994 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.112434
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  • 9
    Digitale Medien
    Digitale Medien
    Tunable dual-wavelength operation of a diode array with an external grating-loaded cavity (1994)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 64 (1994), S. 3089-3091 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: A novel grazing-incidence grating cavity has been developed for simultaneous generation of laser output at two wavelengths. The gain section is a commercial laser diode array. By moving vertically with respect to the optical axis V-shaped double slit at the end mirror, we demonstrate tuning of the spectral separation of the dual-wavelength laser output from 3.52 to 11.29 nm. The side-mode suppression ratio is 10–20 dB. Examination of the far-field patterns reveal that the laser mode at the two wavelengths corresponds to a different order of the array modes.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.111356
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  • 10
    Digitale Medien
    Digitale Medien
    Demonstration of a novel wide-band optical signal generator by deep phase modulation in a fiber coupler (1991)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 62 (1991), S. 1408-1410 
    Details
    ISSN: 1089-7623
    Quelle: AIP Digital Archive
    Thema: Physik , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: A simple method for wide bandwidth optical signal generation has been realized by applying a deep phase modulation signal in a fiber coupler which acts as an all-fiber Michelson interferometer. The output of the interferometer displays a discrete spectrum with a nearly leveled output and frequency bandwidth up to a hundred times that of the frequency of the modulation signal. In this first demonstration, we have generated frequency components up to 4 MHz (with external modulation) and 50 MHz (by direct modulation of the laser diode) respectively. Multigigahertz operation is possible in the future with wideband integrated-optic phase modulators.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1142458
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