Abstract
Inter-band photoexcitation in bulk natural and synthetic diamonds by tightly focused near-IR (1030 nm) ultrashort laser pulses of variable duration (0.3–6.3 ps) promotes characteristic UV photoluminescence A-band and phonon-mediated free-exciton recombination bands, respectively, with distinct phonon progressions. The photoluminescence yield in these diamonds is very similar and highly-nonlinear versus laser intensity with the power slopes, gradually decreasing at higher intensities for all the laser pulsewidths to indicate varying contributions of multi-photon photoexcitation, free-carrier impact ionization and Auger recombination processes in electron-hole plasma (EHP). The peak position of the main free-excitonic photoluminescence band in the synthetic diamond demonstrates universal, pulsewidth-independent “red” spectral shift as a function of laser intensity, representing the electronic bandgap renormalization at the increasing plasma density. The related phonon progression indicates the predominating interaction of free carriers with near-center-zone optical phonons, exerting distinct dynamic increase in phonon energy at the increasing plasma density. Dynamic photoluminescence micro-spectroscopy appears as a simple, but informative experimental tool, paving the way to clarification and modeling of ultrafast electronic and lattice dynamics, as well as laser energy deposition, in different types of diamonds for their micromarking and tracing.
Published Version
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