Broadband optical ultrafast reflectivity of Si, Ge and GaAs

Abstract

Ultrafast optical reflectivity measurements of silicon, germanium, and gallium arsenide have been carried out using an advanced set-up providing intense subpicosecond pulses (35 fs FWHM, $$\lambda $$ λ = 400 nm) as a pump and broadband 340–780 nm ultrafast pulses as a white supercontinuum probe. Measurements have been performed for selected pump fluence conditions below the damage thresholds, that were carefully characterized. The obtained fluence damage thresholds are 30, 20.8, 9.6 mJ/$$\hbox {cm}^2$$ cm 2 for Si, Ge and GaAs respectively. Ultrafast reflectivity patterns show clear differences in the Si, Ge, and GaAs trends both for the wavelength and time dependences. Important changes were observed near the wavelength regions corresponding to the $$E_1$$ E 1 , $$E_1+\Delta $$ E 1 + Δ singularities in the joint density of states, so related to the peculiar band structure of the three systems. For Ge, ultrafast reflectivity spectra were also collected at low temperature (down to 80 K) showing a shift of the characteristic doublet peak around 2.23 eV and a reduction of the recovery times.

Giant photoinduced reflectivity modulation of nonlocal resonances in silicon metasurfaces

“…We underline that this value is much lower than in other studies with comparable, or even smaller, variations of the reflectivity in Si-based platforms. 23,25,28,36 The ΔR∕Rðλ; ΔtÞ signal is mainly characterized by two long-living components: a negative dip at λ ≃ 1370 nm and a positive peak at λ ≃ 1375 nm; these correspond to the spectral regions below and above the minimum of the Fano resonance [see Fig. 1(b)].…”

Pressure-dependent bandgap characteristics in photonic crystals with sensing applications

“…These properties make Ge excellent for photodetectors in on-chip data distribution [32,33] and valuable for emitters [34], lasers [35], and solar cells. Additionally, existing literature shows that ultrafast optical reflectivity measurements of Si, Ge and GaAs have been carried out using sub-picosecond pulses as pump and broadband 340-780 nm ultrafast pulses as probe [36]. Such intriguing results open avenues for cutting-edge research on photonic devices based on these semiconductors.…”

Progress and Perspectives of Spectroscopic Studies on Carbon K-Edge Using Novel Soft X-ray Pulsed Sources

“…X-ray spectroscopy is one of the fundamental spectroscopic techniques in material science due to its element and site selectivity in providing information on local structural and electronic configurations and properties [1][2][3][4][5][6][7]. For instance, the large binding energy difference of the carbon (C), nitrogen (N), and oxygen (O) core level electrons (about 100 eV) can be easily resolved with existing spectrometers, allowing for the investigation of structural and/or electronic dynamics of the materials containing these elements.…”