Non-degenerate fs pump-probe study on InGaN with multi-wavelength second-harmonic generation

Abstract

Non-degenerate fs pump-probe experiments in the UV-visible range for ultrafast carrier dynamics study of InGaN with adjustable pump and probe photon energies are implemented with simultaneously multiwavelength second-harmonic generation (SHG) of a 10 fs Ti:sapphire laser. The multi-wavelength SHG is realized with two beta-barium borate crystals of different cutting angles. The full-widths at half-maximum of the SHG pulses are around 150 fs, which are obtained from the cross-correlation measurement with a reverse-biased 280-nm light-emitting diode as the twophoton absorption photo-detector. Such pulses are used to perform nondegenerate pump-probe experiments on an InGaN thin film, in which indium-rich nano-clusters and compositional fluctuations have been identified. Relaxation of carriers from the pump level to the probe one through the scattering-induced local thermalization (<1 ps) and then the carrier-transport-dominating global thermalization (in several ps) processes is observed.

Dynamics of polarized photoluminescence in m-plane InGaN/GaN quantum wells

“…Previously, a comparable decay time component ͑950 ps͒, observed in similar nonpolar QW structures, was ascribed either to nonlinear nonradiative recombination or to electronhole, as opposed to excitonic, recombination. Intraband relaxation in nitride QWs occurs within a picosecond 16,17 and is not properly resolved in our experiment. 15 The weak temperature dependence indicates that this nonradiative recombination proceeds via another channel that becomes relevant after the fastest traps, responsible for the shortest recombination time component, are filled.…”

“…15 The weak temperature dependence indicates that this nonradiative recombination proceeds via another channel that becomes relevant after the fastest traps, responsible for the shortest recombination time component, are filled. 17 Carrier transfer to the localized states has impact on temporal variation in the PL peak position ͑Fig. Our experiments show that the relevant levels should be deep ͑since the temperature dependence is weak͒ and act as efficient recombination centers ͑as no saturation is observed͒.…”

High power NIR fiber-optic femtosecond Cherenkov radiation and its application on nonlinear light microscopy

“…Due to the fact that the generated femtosecond CR from the output of the wavelength conversion fiber is synchronized with the original pump pulse, besides the applications of multi-photon and multi-harmonic generation microscopy demonstrated in this work, with carefully control the relative spatial and temporal properties of the two synchronized femtosecond pulses, the demonstrated light sources are very useful for future novel biomedical applications, such as coherent Raman scattering (CARS) microscopy [27], stimulated Raman (SRS) microscopy [28,29], stimulated emission depletion (STED) microscopy [30], and multi-color pump-probe microscopy [31].…”

Application of Quasi-Phase Matching Concept for Enhancement of High-Order Harmonics of Ultrashort Laser Pulses in Plasmas

“…In the case of TCP using second harmonic generation, the ratio of the pulse energies of second harmonic and fundamental waves of Ti:sapphire laser was in the range between 0.05 and 0.2 for 800 nm and 1320 nm fundamental waves. TCP of plasmas using conventional scheme (810 nm + 405 nm) has been analyzed for the first time in [29][30][31], where notable enhancement of harmonic yield compared with SCP was achieved. With suitable control of the relative phase between the fundamental and the second harmonic radiation, the latter field enhances the short path contribution, resulting in a clean spectrum of harmonics [19].…”