Transmittance

Summary

Transmittance of the surface of a material is its effectiveness in transmitting radiant energy. It is the fraction of incident electromagnetic power that is transmitted through a sample, in contrast to the transmission coefficient, which is the ratio of the transmitted to incident electric field. Internal transmittance refers to energy loss by absorption, whereas (total) transmittance is that due to absorption, scattering, reflection, etc. Mathematical definitions Hemispherical transmittance Hemispherical transmittance of a surface, denoted T, is defined as :T = \frac{\Phi_\mathrm{e}^\mathrm{t}}{\Phi_\mathrm{e}^\mathrm{i}}, where *Φet is the radiant flux transmitted by that surface; *Φei is the radiant flux received by that surface. Spectral hemispherical transmittance Spectral hemispherical transmittance in frequency and spectral hemispherical transmittance in wavelength of a surface, denoted Tν and Tλ respectively, are defined as

Official source

https://en.wikipedia.org/wiki/Transmittance

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Micro-reflectance and transmittance spectroscopy: a versatile and powerful tool to characterize 2D materials

Dumitru Dumcenco, Andras Kis, Yue Niu

Optical spectroscopy techniques such as differential reflectance and transmittance have proven to be very powerful techniques for studying 2D materials. However, a thorough description of the experimental setups needed to carry out these measurements is lacking in the literature. We describe a versatile optical microscope setup for carrying out differential reflectance and transmittance spectroscopy in 2D materials with a lateral resolution of similar to 1 mu m in the visible and near-infrared part of the spectrum. We demonstrate the potential of the presented setup to determine the number of layers of 2D materials and characterize their fundamental optical properties, such as excitonic resonances. We illustrate its performance by studying mechanically exfoliated and chemical vapor-deposited transition metal dichalcogenide samples.

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