Absorption (electromagnetic radiation)

About: Absorption (electromagnetic radiation) is a research topic. Over the lifetime, 76674 publications have been published within this topic receiving 1381221 citations.

Beyond the Rayleigh scattering limit in high-Q silicon microdisks: theory and experiment.

Abstract: Using a combination of resist reflow to form a highly circular etch mask pattern and a low-damage plasma dry etch, high-quality-factor silicon optical microdisk resonators are fabricated out of silicon-on-insulator (SOI) wafers. Quality factors as high as Q = 5×10^6 are measured in these microresonators, corresponding to a propagation loss coefficient as small as α ~ 0.1 dB/cm. The different optical loss mechanisms are identified through a study of the total optical loss, mode coupling, and thermally-induced optical bistability as a function of microdisk radius (5-30 µm). These measurements indicate that optical loss in these high-Q microresonators is limited not by surface roughness, but rather by surface state absorption and bulk free-carrier absorption.

Theory of Line-Shapes of the Exciton Absorption Bands

Abstract: A general theory of line-shapes of the exciton absorption bands is developed with the help of generating function. method. When the exciton-lattice coupling is weak, and the exciton effective mass .. is ~all, the absorption band is of a Lorentzian shape, provided that the temperature T is not too high. The half-value width H is given by the level broadening of the optically produced K=O ex· citon due to lattice scattering, so that it is proportional to T except at low .temperatures. If the coupling is strong, or the exciton efFective mass is large, or the temperature is very high, the absorp­ tion band is expected to be of a Gaussian shape, and H is proportional to VT. The mutual influence of adjacent absorption bands is also discussed ; it causes the asymmetry and repulsion of the compo­ nents as temperature rises. If we replace T by the density of lattice imperfections, the ·above statements are valid, without substantial modifications, as regards the dependence on the degree of imperfections. These conclusions are in qualitative agreement with experimental data. The comparison further provides us with information on the strength of the exciton-lattice coupling and the energy band structure of the exciton.

The absorption and excretion of water and salts by marine teleosts

Abstract: It is a peculiar and interesting fact that marine teleosts excrete urine which is isotonic or hypotonic with respect to the blood, and therefore of considerably lower osmotic pressure than sea water (Rodier, 1899; Bottazzi, 1906; Dekhuyzen, 1905; Burian, 1908, 1910). From this, it appears that these animals are faced with the task of concentrating the surrounding ocean in order to obtain water for the formation of urine, a task which can only be performed at the expenditure of energy in osmotic work.’ This circumstance might be expected to result in profound differences in the water economy of marine fish as compared with fresh water and terrestial animals to which water is available ad k&turn. The answer to the question of what tissue or tissues actually do the work of separating from the sea water the osmotically dilute solution destined to be excreted as urine appears to rest in the determination of whether the renally excreted water is initially absorbed from the intestine or enters the body through the gills. The work to be reported here leads us to the conclusion that water absorption occurs by way of the intestine; but, surprisingly, it is not in the intestine that the osmotic work is done, for the residue formed there as absorption proceeds is actually more dilute than the ingested sea water, and tends to approach the blood in tonicity. This osmotic dilution results from the fact that Na, K and Cl are absorbed from the intestine, along with a considerable fraction of the water, leaving behind only the poorly absorbed Mg and SO4 in highly concentrated state. During this process of concentration some Mg and SO4 are abosrbed, to be subsequently excreted in the urine. The bulk of the Na, K and Cl, together with the bulk of the water absorbed from the intestine, never appear in the urine, however; they are excreted by routes other than the kidneys-

Surface plasmon resonance enhanced light absorption and photothermal therapy in the second near-infrared window.

Abstract: Enhanced near-field at noble metal nanoparticle surfaces due to localized surface plasmon resonance (LSPR) has been researched in fields ranging from biomedical to photoelectrical applications. However, it is rarely explored on nonmetallic nanomaterials discovered in recent years, which can also support LSPR by doping-induced free charge carriers, let alone the investigation of an intricate system involving both. Here we construct a dual plasmonic hybrid nanosystem Au–Cu9S5 with well controlled interfaces to study the coupling effect of LSPR originating from the collective electron and hole oscillations. Cu9S5 LSPR is enhanced by 50% in the presence of Au, and the simulation results confirm the coupling effect and the enhanced local field as well as the optical power absorption on Cu9S5 surface. This enhanced optical absorption cross section, high photothermal transduction efficiency (37%), large light penetration depth at 1064 nm, excellent X-ray attenuation ability, and low cytotoxicity enable Au–Cu9S5 ...