1,721,025 research outputs found
Ultra-high spatial and temporal resolution using Scanning Near-field Optical Microscopy
No full textScanning near-field optical microscopy (SNOM) is a system that can image beyond the conventional diffraction limit. It does this by collecting the information contained within evanescent fields. This unique ability to image using evanescent fields also enables SNOM to directly measure the electric field distribution in waveguides, where light is guided by total internal reflection.When SNOM is used with a spectrally resolving detector, local temporal phenomena can be detected by analysing spectral interference in the spectra collected by the probe. This spectrally resolving configuration was used to directly measure inter-modal group velocity difference in a multimode ridge waveguide and, using the modes’ spatial profiles to experimentally determine the mode amplitude coefficient ratio. Such an ability to provide measurements on the local dispersion characteristics and relative modal amplitudes of guided light establishes SNOM as a route for investigating the conversion of current single mode photonic devices into multimode devices.The spectrally resolving SNOM system was also used to investigate the sources of temporal delays created by a quasi disordered scattering sample, which was based on John H. Conway’s pinwheel tiling. Whilst the measurements do not create a complete picture of the scattering phenomena in this work, suggestions for improvement are offered with the aim establishing spectrally resolving SNOM systems as tools for mapping localised temporal phenomena in disordered scattering systems
Zinc indiffused PPLN ridge waveguides
No full textWe demonstrate zinc-indiffused PPLN ridge waveguides with insertion losses of 1.8 dB in 3.4 cm long devices with standard telecommunication fiber butt coupling. Low insertion losses are critical for enabling compact, high-efficiency 780 nm wavelength converted laser sources for space-based Rubidium atom cooling systems. Our low insertion losses are attributed to sub-nanometer waveguide sidewall surface roughness produced by ultra precision ductile mode dicing. Surface roughnesses of 0.29 nm have been measured, demonstrating an order of magnitude reduction compared to prior art. We will present our latest work on zinc-indiffused PPLN ridge waveguides and report on ultra precision ductile mode dicing for PPLN ridge waveguide fabrication
Dataset for Temperature dependent polarity inversion in double-metal terahertz emitters
No full textData, code and plots used in the paper, "Temperature dependent polarity inversion in double-metal terahertz emitters "
Submitted to be published in Electronics Letters.
The temperature dependent polarity inversion in double-metal THz emitters was investigated. Double-metal emitters utilising different metal pairings and single edge metal emitters were cooled in a helium flow cryostat and their THz emission was measured over a range of temperatures. Most emitters, including those with insulating layers between the metal and semiconductor, exhibit a flip in polarity of their THz emission between 50 and 100 K. This shows the inversion is a trait intrinsic to the semiconductor and not influenced by the metallic contact on the surface.</span
A radial double-metal bias-free THz emitter for coaxial cable transmission
No full textWe present a method for tailoring emission field profiles through engineering of double-metal (DM) THz emitters. A device with a circular DM pattern is characterized and shown to emit a radial electric field profile, ideal for coupling towire-based waveguides
Advances in Ductile Mode Dicing of PPLN Devices
No full textWe demonstrate ductile mode dicing in periodically poled lithium niobate (PPLN) with sub-nanometer surface roughness. This represents an order of magnitude improvement in the average surface roughness (Sa) and RMS surface roughness (Sq) than previously reported in this material
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
Direct spatial-temporal discrimination of modes in a photonic lightwave circuit using photon scanning tunnelling microscopy
No full textMulti-mode photonic lightwave circuits (PLCs) provide new avenues for extending the performance of single mode systems. As an example, they can potentially provide increased bandwidth by multiplexing information into different waveguide modes[1]. For practical applications of multi-mode PLCs to be developed, a measurement technique is required to investigate detailed mode profiles and propagation constants in complex circuits. Photon scanning tunnelling microscopy (PSTM) provides a means of experimentally tracking the femtosecond inter-modal delays observed in PLCs with the ability to discriminate modes by their spatial profiles inside the waveguide
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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