Surface-enhanced infrared absorption spectroscopy has attracted increased attention for direct access to molecular vibrational fingerprints in the mid-infrared. Perfect-absorber metamaterials (PAMs) with multi-band spectral responses and significant enhancement of the local near-field intensity were developed to improve the intrinsic absorption cross sections of absorption spectrum to identify ...

Thin metallic films have several potential applications in MEMS field, and one of them is used as infrared absorber. In this paper, we first build a model of metallic infrared absorption and then discuss the transmission characteristics of infrared through metal and dielectric film. For a thin film material, the maximum absorption will occur when its sheet resistance equals to the impedance of ...

Absorbing infrared radiation efficiently is important for critical applications such as thermal imaging and infrared spectroscopy. Common infrared absorbing materials are not standard in Si VLSI technology. We demonstrate ultra-broadband mid-infrared absorbers based purely on silicon. Broadband absorption is achieved by the combined effects of free carrier absorption, and vibrational and plasmo...

We propose the use of thin Ag film deposition to remedy the degradation of near-infrared (NIR) absorption of black Si caused by high-temperature thermal annealing. A large amount of random and irregular Ag nanoparticles are formed on the microstructural surface of black Si after Ag film deposition, which compensates the degradation of NIR absorption of black Si caused by thermal annealing. The ...

The near-infrared (NIR) spectral region (700-2500 nm) is a fertile source of chemical information in the form of overtone and combination bands of the fundamental infrared absorptions and low-energy electronic transitions. This region was initially perceived as being too complex for interpretation and consequently was poorly utilized. Advances in chemometric techniques that can extract massive ...

Visible upconversion luminescence was observed in Cr3+: Al2O3 crystal under focused femtosecond laser irradiation. The luminescence spectra show that the upconversion luminescence originates from the 2E-4A2 transition of Cr3+. The dependence of the fluorescence intensity of Cr3+ on the pump power reveals that a two-photon absorption process dominates in the conversion of infrared radiation to t...

Photonic crystal coupled with plasmonic nanoparticle arrays to form a periodic plasmonic architecture was prepared by loading Au nanoparticles inside the inverse opal TiO(2) film. The visible and near infrared light absorption was increased by 62% and the overall light-to-electricity conversion yield was thus increased by 41% compared with the control test.

Modern ab initio and multiscale methods enable the simulation of vibrational properties of very large molecules. Within the harmonic approximation, the traditional generation of the spectra based on the force field diagonalization can become inefficient due to the excessive demands on computer time and memory. The present study proposes to avoid completely the matrix diagonalization with a dire...

We report mid-infrared (MIR) nonlinear absorption in As2S3 glasses which results from two-photon excitation of valence electron to the Urbach extension followed by strong linear absorption of excited states. The measured MIR nonlinear absorption can be 3 to 4 orders of magnitude stronger than the two-photon absorption in the near-infrared for similar laser intensities and does not result from c...

We report a study of the effect of optical absorption on generation of coherent infrared radiation from mid-IR to THz region from GaSe crystal. The infrared-active modes of epsilon-GaSe crystal at 236 cm(-1) and 214 cm(-1) were found to be responsible for the observed optical dispersion and infrared absorption edge. Based upon phase matching characteristics of GaSe for difference-frequency gene...