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  • 1
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 74 (1999), S. 179-181 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We demonstrate the operation of an apparatus which we call the depolarization near-field scanning optical microscope. It delivers subwavelength resolution with uncoated optical fiber tips without the need for additional modulation techniques. We show that—in the near field—the edges perpendicular to the incident optical polarization are imaged. This dependence on the orientation of the linear polarization as well as the influence of small ellipticities of the polarization state on the imaging process are measured on a well-defined test sample. The transition from near- to far-field imaging as a function of the tip height is demonstrated. The results are in good agreement with recent theoretical predictions. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 73 (1998), S. 569-571 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The interplay of carrier heating effects and transverse variations of the carrier distribution functions has a significant influence on the ultrafast emission dynamics of semiconductor vertical cavity surface emitting lasers. This interplay can lead to dynamic overshooting and oscillations (here at 200 GHz) even for lasing on a single transverse and single longitudinal mode. A simple equivalent model is a cavity containing the gain medium and a saturable absorber. The numerical results can directly be compared with recently published experiments. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 74 (1999), S. 920-922 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A stationary electrically pumped semiconductor vertical cavity surface emitting laser held at T=300 K is perturbed by a femtosecond optical pulse, which is resonant with its cavity mode. For low to moderate intensities, the semiconductor laser reacts with a switch-off. Surprisingly, for yet higher pulse energies, this behavior disappears and a direct recovery of the original emission level is observed. Such behavior cannot be understood within standard or extended rate equations. We speculate that Rabi flops are important under these conditions. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 73 (1998), S. 1170-1172 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Recent experiments claim that subwavelength resolution can be obtained with an optical scanning microscope using uncoated optical fiber probes. In these experiments, linearly polarized light is sent down the fiber which is reflected and depolarized in the tip-sample region. The internally reflected signal in the orthogonal polarization is detected. Here, numerical solutions of the vector Maxwell equations for a model are discussed. In this model, subwavelength resolution can indeed be obtained in the above mode, while this is not possible without polarization sensitivity. The influence of parameters such as polarization, different scanning modes and tip-sample distance is discussed. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 70 (1997), S. 853-855 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Recently it has been shown that perturbation of an already operating semiconductor laser with an additional pump pulse may lead to an unusual ultrafast switch-off. This effect is due to transient carrier heating. Subsequent carrier cooling allows for switch-on after about two picoseconds. In vertical cavity lasers containing only a few quantum wells as the active medium, the recovery, however, is limited by the comparatively low gain in the cavity. Here we demonstrate experimentally that both switch-off and switch-on can exhibit subpicosecond time constants if a bulk semiconductor is used as the active medium. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1432-2218
    Keywords: Key words: Laparoscopic ultrasound—Intraoperative cholangiogram—Digital fluorocholangiogram—Laparoscopic cholecystectomy—Choledocholithiasis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Background: Laparoscopic ultrasound is an alternative to operative cholangiogram for evaluation of the common bile duct (CBD) during laparoscopic cholecystectomy. It is a safe, fast, and reliable method for detecting choledocholithiasis. Methods: We prospectively evaluated the sensitivity and specificity of laparoscopic ultrasound (LUS) and digital fluorocholangiogram (DFCG) in a three-phase study of 360 consecutive patients. Results: In phase I, 140 patients undergoing laparoscopic cholecystectomy had LUS performed first, followed by DFCG. Thirteen patients had CBD calculi identified on LUS. Four patients with confirmed (two cases) or presumed (two cases) CBD calculi on DFCG were not identified on LUS. Thus, the specificity of LUS was 100%, whereas the sensitivity was 76.5%. DFCG had four false positives, for a sensitivity of 100% with a specificity of 96.7%. LUS was performed, on average, in 6.6 min, whereas DFCG required 10.9 min to perform. In phase II, the infusion of saline through a cystic duct catheter was performed in instances where the distal CBD could not be well seen. This maneuver distended the intrapancreatic portion of the CBD, allowing better visualization. Nine stones were identified on LUS in 78 patients, increasing the sensitivity to 100%. One false positive DCFG was encountered, resulting in a sensitivity of 100% and a specificity of 98.6%. In phase III, we performed routine LUS and used DFCG only in select cases. The sensitivity and specificity for LUS were 95.7% and 100%, respectively, whereas DFCG had a sensitivity of 95.2% and a specificity of 100%. One patient in phase III has returned 11 months post-op with a CBD stone. This was initially missed on LUS, DFCG, and postoperative ERCP. The sensitivity and specificity in all 360 patients were 90% and 100% for LUS and 98.1% and 98.1% for DFCG, respectively. A total of five CBD stones were missed by LUS, four early in the study (phase I). One missed on LUS in phase III was also missed by DFCG and ERCP. Conclusions: LUS is a reliable alternative to DFCG during laparoscopic cholecystectomy (LC). With experience, it is as sensitive as DFCG and more specific. It is more rapidly performed than cholangiography.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Applied physics 66 (1998), S. S939 
    ISSN: 1432-0630
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Type of Medium: Electronic Resource
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