1,720,965 research outputs found
Voltage-tunable near infrared photodetector: a versatile tool for optical communication systems
No full textVoltage-tunable near-infrared photodetector: Versatile component for optical communication systems
No full textWe present a voltage-tunable wavelength-selective photodetector (VWP) for the near-infrared (NIR), realized by engineering the optical properties of Si and Ge. The structure exhibits a wide tunability by varying the applied voltage and weighting the photocurrents generated by two back-to-back diodes. We demonstrate its versatility in deconvolving signals of different wavelengths and a preliminary study on the applications of the VWP as a solid-state spectrum analyzer, The spectrum of NIR light impinging the device can be resolved from a set of photocurrent measurements for different bias voltages. (C) 1998 American Vacuum Society
Photocurrent spectroscopy measurements of Si-Ge alloys and superlattices
No full textWe used photocurrent spectroscopy at 300 K, 77 K and 4.2 K to investigate the optical absorption processes of (001) Si-Ge strained layer superlattices and alloys with an average composition of 50%Si-50%Ge. We observed an evolution toward higher energies of the threshold in the photocurrent spectra as the period of the superlattices decreases, with the spectrum of the shortest period superlattices (2:2) approaching that of the alloy. The energy dependence of absorption in these Si-Gr heterostructures is quite distinct from that measured in elemental silicon
Voltage tunable SiGe photodetector: A novel tool for crypted optical communications through wavelength mixing
No full textA novel tandem SiGe-Si device is demonstrated which, based on different photoresponses in two back-to-back diodes, exhibits a voltage tunable spectral responsivity. This feature, in conjunction with a wavelength dependence in the current direction, allows the efficient decryption of a signal when substantial noise is added to distinct carrier frequencies. Time dependent encryption schemes are also possible via a modulated voltage bias. (C) 1997 American Institute of Physics
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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