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The laser-induced white emission of the graphene-based microchip was investigated under near-infrared region laser irradiation. The emission was characterized by an excitation threshold and an exponential dependence on the pump laser power. A decrease in temperature caused an increase in both the number of absorbed photons and the emission threshold. This dependence can be explained by the multiphoton ionization process in ( sp2, sp3) hybridized domains.

The broadband laser induced white emission (LIWE) spectra of NdAlO3 nanocrystals in vacuum, air, and liquid N2 were explored. In particular, their dependence on excitation laser power was investigated. It was found that the LIWE spectra intensity increased exponentially the with laser power above the excitation threshold in all three cases. The process for NdAlO3 nanocrystals was discussed in terms of multiphoton ionization assisted by ejection of hot electrons. Two differences were observed depending on the conditions: the number of photons involved in the emission was higher in liquid N2 due to additional multiphoton ionization contribution of N2. Also, threshold value for LIWE showed an increasing behavior in air and liquid N2, discussed in terms of relative permittivity and thermal dissipation.

The effect of vacuum level on laser induced white emission (LIWE) of graphene foam is investigated. The results are compared with the electric incandescence of tungsten wire. The increase in pressure inside the dynamic vacuum chamber reduces the emission intensity of LIWE and has no effect on the emission of the electrically driven tungsten wire. The same dependency was observed in the case of field emission (FE) of carbon cathodes. The analogy confirms that white emission and FE are coincident processes occurring during laser excitation of graphene foam.