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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.


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Journal ArticleDOI
TL;DR: In this paper, the authors explored the use of several methods for carrying out absorption spectroscopy with mid-infrared quantum cascade sources, which include multipass absorption spectrography, cavity ring down spectrograms (CRDS), ICOS, and quartz-enhanced photoacoustic spectrogram (QEPAS).
Abstract: Quantum cascade (QC) lasers are virtually ideal mid-infrared sources for trace gas monitoring. They can be fabricated to operate at any of a very wide range of wavelengths from ∼ 3 μm to ∼ 24 μm. Seizing the opportunity presented by mid-infrared QC lasers, several groups world-wide are actively applying them to trace gas sensing. Real world applications include environmental monitoring, industrial process control and biomedical diagnostics. In our laboratory we have explored the use of several methods for carrying out absorption spectroscopy with these sources, which include multipass absorption spectroscopy, cavity ring down spectroscopy (CRDS), integrated cavity output spectroscopy (ICOS), and quartz-enhanced photoacoustic spectroscopy (QEPAS).

346 citations

Journal ArticleDOI
TL;DR: A quantitative method is presented for identification of the dynamic range of the detectable absorption coefficient in the analysis of transmission terahertz time-domain spectroscopy data, which indicates the largest detectable absorption coefficients are determined by the scan-to-scan reproducibility of the signal.
Abstract: We present a quantitative method for identification of the dynamic range of the detectable absorption coefficient in the analysis of transmission terahertz (THz) time-domain spectroscopy data. In transmission measurements the largest detectable absorption coefficient is determined by the dynamic range of the THz signals, whereas in reflection measurements the largest detectable absorption coefficient is determined by the scan-to-scan reproducibility of the signal.

346 citations

Journal ArticleDOI
TL;DR: A simple experiment demonstrates that room-temperature thermal transport in Si significantly deviates from the diffusion model already at micron distances, indicating a transition from the diffusive to the ballistic transport regime for the low-frequency part of the phonon spectrum.
Abstract: The "textbook" phonon mean free path of heat carrying phonons in silicon at room temperature is ∼40 nm. However, a large contribution to the thermal conductivity comes from low-frequency phonons with much longer mean free paths. We present a simple experiment demonstrating that room-temperature thermal transport in Si significantly deviates from the diffusion model already at micron distances. Absorption of crossed laser pulses in a freestanding silicon membrane sets up a sinusoidal temperature profile that is monitored via diffraction of a probe laser beam. By changing the period of the thermal grating we vary the heat transport distance within the range ∼1-10 μm. At small distances, we observe a reduction in the effective thermal conductivity indicating a transition from the diffusive to the ballistic transport regime for the low-frequency part of the phonon spectrum.

346 citations

Journal ArticleDOI
TL;DR: Electrochemical studies indicate desirable HOMO/LUMO levels that enable a high open circuit voltage while blending them with fullerene derivatives as electron acceptors and both materials show sufficient hole mobility allowing efficient charge extraction and a good fill-factor for PSC application.
Abstract: Two low-bandgap (LGB) conjugated polymers (P1 and P2) based on thiophene-phenylene-thiophene (TPT) with adequate energy levels have been designed and synthesized for application in bulk-heterojunction polymer solar cells (PSCs). The absorption spectral, electrochemical, field effect hole mobility and photovoltaic properties of LGB TPT derivatives are investigated and compared with poly(3-hexylthiophene) (P3HT). Photophysical studies reveal bandgaps of 1.76 eV for P1 and 1.70 eV for P2, which could effectively harvest broader solar spectrum. In addition, the thin film absorption coefficients of P1 and P2 are 1.6 × 105 cm−1 (λ ≈ 520 nm) and 1.4 × 105 cm−1 (λ ≈ 590 nm), respectively. Electrochemical studies indicate desirable HOMO/LUMO levels that enable a high open circuit voltage while blending them with fullerene derivatives as electron acceptors. Furthermore, both materials show sufficient hole mobility (3.4 × 10−3 cm2/Vs for P2) allowing efficient charge extraction and a good fill-factor for PSC applica...

346 citations

Journal ArticleDOI
TL;DR: Amplification of SPs by stimulated emission is demonstrated, which can be considered analogous to photon amplification in a laser, thereby suggesting novel approaches in the field of nano-optics.
Abstract: Surface plasmons (SPs) are surface-bound electromagnetic waves supported by metals, offering the possibility of strong spatial confinement of electromagnetic fields on the micro- and nanoscales. They suffer, however, from strong damping caused by internal absorption and radiation losses. Here we demonstrate amplification of SPs by stimulated emission, which marks a possible solution to this problem. We use an attenuated-total-reflection setup to detect stimulated emission of SPs at the interface between a silver film and an optically pumped dye solution acting as the amplifying medium. Clear evidence of stimulated emission is provided by an excellent agreement of the experimental observations with a theoretical analysis. Amplification of SPs can be considered analogous to photon amplification in a laser, thereby suggesting novel approaches in the field of nano-optics.

346 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
2022185
20213,106
20202,866
20192,953
20182,876
20172,679