1,721,247 research outputs found
Optical black hole lasers
Full text linkUsing numerical simulations we show how to realize an optical black hole laser, i.e. an amplifier formed by travelling refractive index perturbations arranged so as to trap light between a white and a black hole horizons. The simulations highlight the main features of these lasers: the growth inside the cavity of positive and negative frequency modes accompanied by a weaker emission of modes that occurs in periodic bursts corresponding to the cavity round trips of the trapped modes. We then highlight a new regime in which the trapped mode spectra broaden until the zero-frequency points on the dispersion curve are reached. Amplification at the horizon is highest for zero-frequencies, therefore leading to a strong modification of the structure of the trapped light. For sufficiently long propagation times, lasing ensues only at the zero-frequency modes
Experimental quantum cosmology in time-dependent optical media
Full text linkIt is possible to construct artificial spacetime geometries for light by using intense laser pulses that modify the spatiotemporal properties of an optical medium. Here we theoretically investigate experimental possibilities for studying spacetime metrics of the form . By tailoring the laser pulse shape and medium properties, it is possible to create a refractive index variation that can be identified with . Starting from a perturbative solution to a generalized Hopfield model for the medium described by an , we provide estimates for the number of photons generated by the time-dependent spacetime. The simplest example is that of a uniformly varying that therefore describes the Robertson–Walker metric, i.e. a cosmological expansion. The number of photon pairs generated in experimentally feasible conditions appears to be extremely small. However, large photon production can be obtained by periodically modulating the medium and thus resorting to a resonant enhancement similar to that observed in the dynamical Casimir effect. Curiously, the spacetime metric in this case closely resembles that of a gravitational wave. Motivated by this analogy, we show that a periodic gravitational wave can indeed act as an amplifier for photons. The emission for an actual gravitational wave will be very weak but should be readily observable in the laboratory analogue
Two-beam noncollinear Makers fringe technique
No full textA new technique to characterize second-order nonlinear films with sub-micron depth resolution is proposed. The potential of this method has been demonstrated in thermally-poled silica layers
Revisiting the 1888 Hertz experiment
No full textWe revisit the original experiment performed by Hertz in 1888 and use a simple setup to produce electromagnetic waves with a frequency in the range of 3 MHz. By doing a Fourier analysis of the signal captured by. a resonant antenna, we can study the behavior of the RLC series circuit, frequency splitting of coupled resonances, and the characteristics of the near-field emitted by the loop antenna. (c) 2006 American Association of Physics Teachers. RI Clerici, Matteo/F-6416-201
Frontiers in Modern Optics
No full textThe year 2015 was designated by the United Nations General Assembly as the Year of Light and Light-based Technologies, and also marks the anniversaries of a number of significant historical events related to light. In 1015, Ibn Al-Haytham published his book of optics; in 1815, Fresnel first proposed the notion that light is actually a wave; James Clerk Maxwell then firmly established this concept with his electromagnetic theory of light propagation; and Einstein announced his discovery of the photoelectric effect, demonstrating that light is made of photons in 1905, followed in 1915 by his general theory of relativity, in which light plays a central role. This book presents lectures from the International School of Physics Enrico Fermi summer school: Frontiers in Modern Optics, held in Varenna, Italy, in June and July 2014. The school attempted to give a broad and modern overview of the field of optics in a series of lectures addressing ongoing topics of research. Subject areas include: nonlinear optics; light as an investigation tool in modern physics; and detection and imaging. A unique feature of the book is that each chapter has been prepared as a collaborative effort between students at the school and lecturers. This approach has proved very successful and may well provide a model for the future
Optical Bloch-mode-induced quasi phase matching of quadratic interactions in one-dimensional photonic crystals
No full textWe examine in detail the quasi-phase-matching process obtained as a stationary modulation of the fundamental field at the band edge of a finite one-dimensional photonic crystal. The treatment is carried out in terms of the structure Bloch waves and fully explains the behavior of second-harmonic generation in the grating. An integrated microstructured AlGaAs mesa waveguide is proposed that gives efficient second-harmonic and difference-frequency generation in virtue of the combined presence of a periodic modulation of the fundamental-field amplitude and of the photonic bandgap edge
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
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