Germanium-on-silicon mid-infrared waveguides and Mach-Zehnder interferometers

In this paper we describe Ge-on-Si waveguides and Mach-Zehnder interferometers operating in the 5.2 - 5.4 mu m wavelength range. 3dB/cm waveguide losses and Mach-Zehnder interferometers with 20dB extinction ratio are presented

Germanium-on-silicon planar concave grating wavelength (de)multiplexers in the mid-infrared

Mid-infrared wavelength (de)multiplexers based on planar concave gratings (PCGs) fabricated on a germanium-on-silicon waveguide platform are presented. PCGs with two different types of gratings (flat facet and distributed bragg reflectors) are analyzed for both transverse electric (TE) and transverse magnetic (TM) polarizations. The insertion loss and cross talk for flat facet PCGs are found to be -7.6/-6.4¿dB and 27/21¿dB for TE/TM polarization. For distributed bragg reflector PCGs the insertion loss and cross talk are found to be -4.9/-4.2¿dB and 22/23¿dB for TE/TM polarization

On the interpretation of the multicolour disc model for black hole candidates

We present a critical analysis of the usual interpretation of the multicolour disc model parameters for black hole candidates in terms of the inner radius and temperature of the accretion disc. Using a self-consistent model for the radiative transfer and the vertical temperature structure in a Shakura-Sunyaev disc, we simulate the observed disc spectra, taking into account doppler blurring and gravitational redshift, and fit them with multicolour models. We show not only that such a model systematically underestimates the value of the inner disc radius, but that when the accretion rate and/or the energy dissipated in the corona are allowed to change the inner edge of the disc, as inferred from the multicolour model, appears to move even when it is in fact fixed at the innermost stable orbit.Comment: 4 pages including 2 figures, accepted for publication in MNRA

Singular values of some modular functions

We study the properties of special values of the modular functions obtained from Weierstrass P-function at imaginary quadratic points.Comment: 19 pages,corrected typo

Natural Variability and Warming Signals in Global Ocean Wave Climates

地球全体の波浪特性の変化傾向と自然変動の関係を解明 --地球温暖化の沿岸域への影響を定量化--. 京都大学プレスリリース. 2021-06-15.This paper presents a multivariate classification of the global wave climate into types driven by atmospheric circulation patterns. The primary source of the net long-term variability is evaluated based on historical wave simulations. Results show that the monsoon, extratropical, subtropical, and polar wave climate types of the Pacific and North Atlantic Oceans are dominated by natural variability, whereas the extratropical and subtropical wave climate types in the Indian Ocean, and the tropical wave climate types of the Atlantic and Pacific Oceans exhibit a global warming signal. In the Pacific sector of the Southern Ocean, strong natural variability may mask a global warming signal that is yet to emerge as being statistically significant. In addition, wave climate teleconnections were found across the world that can provide a framework for joint strategies to achieve the goals of climate adaption for resilient coastal communities and environments