Photoexcitation

About: Photoexcitation is a research topic. Over the lifetime, 5874 publications have been published within this topic receiving 134733 citations.

Picosecond response of gallium-nitride metal-semiconductor-metal photodetectors

Abstract: Metal–semiconductor–metal ultraviolet photodiodes fabricated on GaN were tested in the picosecond regime with an electro-optic sampling system. A device with a feature size of 1 μm showed a response with 1.4 ps rise time and 3.5 ps full width at half maximum. The derived electron velocity, 1.43×107 cm/s, is in good agreement with independent photoexcitation measurements. A slower impulse response was observed in a device with smaller feature size of 0.5 μm.

Ultrafast excited state dynamics and dispersion studies of nonlinear optical properties in dinaphthoporphycenes

Abstract: Ultrafast excited state dynamics of dinaphthoporphycenes were investigated using femtosecond and picosecond degenerate pump-probe techniques at 600 nm and 800 nm, respectively. Femtosecond pump-probe data indicated photo-induced absorption at 600 nm resulting from two-photon/single photon excitation, whereas picosecond pump-probe data demonstrated photo-bleaching which was a consequence of three-photon absorption. The fastest lifetimes (100–120 fs) observed are attributed to the intramolecular vibrational relaxation, the slower ones (1–3 ps) to internal conversion, and the slowest components (7–10 ps) to non-radiative decay back to ground state. Z-scan studies in the 560–600 nm range were also carried out.

Optical Absorption Characteristics of GaAs–AlGaAs Multi-Quantum-Well Heterostructure Waveguides

Abstract: Optical waveguide absorption characteristics of MBE grown GaAs–AlGaAs MQW doubleheterostructure wafers are studied by measuring edge luminescence under photoexcitation, and are compared with those of conventional GaAs DH wafers. The edge luminescence spectra show a double peak structure which is well explained by waveguide self-absorption, rather than by L0-phonon participation as has been suggested by other workers. The optical absorption loss of the unexcited MQW waveguide at its lasing wavelength is found to be much smaller than that for the conventional DH waveguide.

Sub-10 fs Time-Resolved Vibronic Optical Microscopy

Abstract: We introduce femtosecond wide-field transient absorption microscopy combining sub-10 fs pump and probe pulses covering the complete visible (500–650 nm) and near-infrared (650–950 nm) spectrum with diffraction-limited optical resolution. We demonstrate the capabilities of our system by reporting the spatially- and spectrally-resolved transient electronic response of MAPbI3–xClx perovskite films and reveal significant quenching of the transient bleach signal at grain boundaries. The unprecedented temporal resolution enables us to directly observe the formation of band-gap renormalization, completed in 25 fs after photoexcitation. In addition, we acquire hyperspectral Raman maps of TIPS pentacene films with sub-400 nm spatial and sub-15 cm–1 spectral resolution covering the 100–2000 cm–1 window. Our approach opens up the possibility of studying ultrafast dynamics on nanometer length and femtosecond time scales in a variety of two-dimensional and nanoscopic systems.

Vibrational relaxation dynamics of trans-stilbene in the lowest excited singlet state. Pump and probe wavelength dependencies of the picosecond time-resolved anti-Stokes Raman spectrum

Abstract: The vibrational relaxation process of trans-stilbene in the lowest electronically excited singlet state after photoexcitation has been studied by picosecond time-resolved anti-Stokes Raman spectros...