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  • 1
    Electronic Resource
    Electronic Resource
    Femtosecond pump-probe near-field optical microscopy (1999)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 70 (1999), S. 2758-2764 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We have developed an instrument for optically measuring carrier dynamics in thin-film materials with ∼150 nm lateral resolution, ∼250 fs temporal resolution, and high sensitivity. This is achieved by combining ultrafast pump-probe laser spectroscopic techniques, which measure carrier dynamics with femtosecond-scale temporal resolution, with the nanometer-scale lateral resolution of near-field scanning optical microscopes (NSOMs). We employ a configuration in which carriers are excited by a far-field pump laser pulse and locally measured by a probe pulse sent through a NSOM tip and transmitted through the sample in the near field. A novel detection system allows for either two-color or degenerate pump and probe photon energies, permitting greater measurement flexibility over earlier published work. The capabilities of this instrument are proven through near-field degenerate pump-probe studies of carrier dynamics in GaAs/AlGaAs single quantum well samples locally patterned by focused-ion-beam (FIB) implantation. We find that lateral carrier diffusion across the nanometer-scale FIB pattern plays a significant role in the decay time of the excited carriers within ∼1 μm of the implanted stripes, an effect which could not have been resolved with a far-field system. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1149841
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  • 2
    Electronic Resource
    Electronic Resource
    Optical nonlinearity in low-temperature-grown GaAs: Microscopic limitations and optimization strategies (1999)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 74 (1999), S. 3134-3136 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have quantitatively measured the linear and the nonsaturable absorption as well as the absorption modulation and its recovery time in as-grown and annealed low-temperature (LT) GaAs. Correlation of the optical data with As antisite (AsGa) defect densities yields the absorption cross section and the saturation parameter of the dominant AsGa to the conduction-band defect transition. We show that this defect transition is mainly responsible for the large nonsaturable absorption in as-grown LT GaAs with fast recovery times. Reducing the AsGa density by annealing yields an optimized material with small nonsaturable absorption, high absorption modulation, and fast recovery times. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.124086
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  • 3
    Electronic Resource
    Electronic Resource
    Eyesafe pulsed microchip laser using semiconductor saturable absorber mirrors (1998)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 72 (1998), S. 3273-3275 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We passively Q-switched a diode-pumped Er/Yb:glass microchip laser at a 1.535 μm wavelength using semiconductor saturable absorber mirrors and demonstrated pulses as short as 1.2 ns. By varying the design parameters of the saturable absorber, the pump power, and the pump spot size, we achieved repetition rates from 300 Hz to 100 kHz with pulse energies up to 4 μJ. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.121621
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  • 4
    Electronic Resource
    Electronic Resource
    Ultrafast high-intensity nonlinear absorption dynamics in low-temperature grown gallium arsenide (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 69 (1996), S. 2566-2568 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We study carrier dynamics in GaAs thin films grown by molecular beam epitaxy at 250, 300, and 350 °C by differential transmission experiments at various carrier excitation densities. The differential transmission shows that carrier trapping in point defects is much faster than the recombination of the trapped carriers. As a consequence, the defect states can be saturated at high carrier densities. If the growth temperature is decreased, the initial trapping becomes faster while the subsequent recombination of the trapped carriers becomes slower. We show that this is due to the growth temperature dependent defect densities. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.117701
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  • 5
    Electronic Resource
    Electronic Resource
    Chirp-controlled ultrafast optical nonlinearities in semiconductors (1998)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 73 (1998), S. 3025-3027 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We experimentally demonstrate that the differential transmission (DT) response of bulk semiconductors excited well above the band edge can be manipulated by chirping of the broadband excitation and readout pulses. In particular, the maximum transmission change in spectrally integrated DT experiments can be modified on the 20 fs time scale. Spectrally resolved DT studies explain this chirp dependence. Depending on the sign of the chirp, positive or negative DT contributions at low or high photon energies are probed with varying efficiency around zero time delay. These results demonstrate that chirp can become an additional degree of freedom for the optimization of device performance in ultrafast all-optical switching. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.122660
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  • 6
    Electronic Resource
    Electronic Resource
    Double-chirped semiconductor mirror for dispersion compensation in femtosecond lasers (1999)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 75 (1999), S. 2166-2168 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A double-chirped mirror structure with broadband negative dispersion was realized with semiconductor technology. The necessary high precision of the fabrication was achieved by using special calibration structures. A single reflection on the obtained low-loss mirror produces sufficient negative dispersion for dispersion compensation in a femtosecond laser cavity. In this way we demonstrate 200 fs pulses from a compact Nd:glass laser without any additional dispersion compensation. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.124953
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  • 7
    Electronic Resource
    Electronic Resource
    Femtosecond near-field optical spectroscopy of implantation patterned semiconductors (1999)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 74 (1999), S. 61-63 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have developed a femtosecond-resolved near-field scanning optical microscope, using a diffraction-limited pump and near-field probe configuration, which allows us to measure carrier dynamics with a spatial resolution of ∼150 nm and a time resolution of ∼250 fs. This instrument is used for near-field degenerate pump–probe studies of carrier dynamics in GaAs/AlGaAs single quantum well samples locally patterned by focused-ion-beam (FIB) implantation. We find that lateral carrier diffusion across the nanometer-scale FIB pattern plays a significant role in the decay of the excited carriers. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.123133
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  • 8
    Electronic Resource
    Electronic Resource
    Wide bandwidth (100) GaAs/fluorides quarter-wavelength Bragg reflectors grown by molecular beam epitaxy (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 69 (1996), S. 3474-3476 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Broadband quarter-wavelength Bragg reflectors that consist of periodic stacks of fluorides (CaF2–BaF2–CaF2) and GaAs, centered at 1.4 μm, were grown by molecular beam epitaxy. Despite a total fluoride thickness as high as 720 nm, crack-free surface morphology was obtained. In this letter, we report a crack-free standard quarter-wavelength III–V semiconductor-fluoride Bragg reflector. With only three stacks, the bandwidth with reflectance above 95% is about 650 nm (1.15–1.80 μm), while, near the center wavelength, the reflectivity is as high as 99%. Both important wavelengths of 1.3 and 1.55 μm for optical communication are included in the very wide high reflectance plateau. These mirrors are expected to have wide applications for optical and optoelectronic devices. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.117256
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  • 9
    Electronic Resource
    Electronic Resource
    Femtosecond response times and high optical nonlinearity in beryllium-doped low-temperature grown GaAs (1999)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 74 (1999), S. 1269-1271 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have investigated the effect of beryllium doping on the optical nonlinearity and on the carrier dynamics in low-temperature (LT) grown GaAs for various growth temperatures and doping levels. Pump–probe experiments with 20 fs pulses and quantitative measurements of the nonlinear absorption show that in undoped LT GaAs, ultrafast response times are only obtained at the expense of low absorption modulation. In contrast, in Be-doped LT GaAs, high absorption modulation is maintained for response times as short as 100 fs. These results are qualitatively explained accounting for the point-defect-related optical transitions in LT-GaAs. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.123521
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  • 10
    Electronic Resource
    Electronic Resource
    Continuous-wave mode-locked solid-state lasers with enhanced spatial hole burning (1995)
    Springer
    Applied physics 61 (1995), S. 429-437 
    Details
    ISSN: 1432-0649
    Keywords: 42.60 ; 42.55 ; 42.65
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We systematically investigate the difference between both actively and passively mode-locked lasers with Gain-at-the-End (GE) and Gain-in-the-Middle (GM) at the example of Nd:YLF lasers. The GE laser generates pulse widths approximately three times shorter than a comparable GM cavity. This is due to enhanced Spatial Hole Burning (SHB) which effectively flattens the saturated gain and allows for a larger lasing bandwidth compared to a GM cavity. We first investigate enhanced SHB by measuring the cw mode spectrum, where we have observed that the mode spacing in GE cavities depends primarily on the crystal length. This was also confirmed for a Nd:LSB crystal, where the pump absorption length was significantly shorter than the crystal length. In mode-locked operation, pulse widths of 4 ps for passive mode locking and 5 ps for active mode locking are demonstrated with GE cavities, compared to 11 ps for passive and 17 ps for active mode locking with GM cavities. Additionally, the time-bandwidth product for the GE cavity is approximately twice the ideal product for a sech2 pulse shape and cannot be improved by dispersion compensation alone, while the GM cavity has nearly ideal time-bandwidth-limited performance. The results for the GM cavity compare well to existing theories taking into account the added effect of pump-power-dependent gain bandwidth which increases the bandwidth of Nd: YLF from 360 to 〉 500 GHz. In a following paper [1] (called Part II) a rigorous theoretical treatment of the effects due to SHB will be presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01081271
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