Highly efficient THG in TiO_2 nanolayers for third-order pulse characterization

Abstract

Third harmonic generation (THG) of femtosecond laser pulses in sputtered nanocrystalline TiO2 thin films is investigated. Using layers of graded thickness, the dependence of THG on the film parameters is studied. The maximum THG signal is observed at a thickness of 180 nm. The corresponding conversion efficiency is 26 times larger compared to THG at the air-glass interface. For a demonstration of the capabilities of such a highly nonlinear material for pulse characterization, third-order autocorrelation and interferometric frequency-resolved optical gating (IFROG) traces are recorded with unamplified nanojoule pulses directly from a broadband femtosecond laser oscillator.

Photochemical activity of TiO2nanotubes

“…These studies were now also extended to TiO 2 . For TiO 2 layers with nanogranular surfaces, a significant enhancement of third harmonic generation was reported [13]. Currently, the specific mechanisms of such surface enhanced nonlinear processes are still not completely understood.…”

Formation of 100-nm periodic structures on a titanium surface by exploiting the oxidation and third harmonic generation induced by femtosecond laser pulses

“…Both LSFLs and HSFLs were observed in the fs laser ablation of Ti [6,22,23]. In particular, the shortest period of HSFLs was found to be only one-tenth of the irradiation laser wavelength and the physical mechanism responsible for the deep subwavelength period is still under investigation [22][23][24][25][26][27]. In fact, sub-100-nm HSFLs have been demonstrated in the ablation of Ti by using 790-nm fs laser pulses and it was suggested that laser-induced oxide (i.e., the formation of TiO 2 on the surface of Ti) might play an important role in the formation of such HSFLs [22].…”

ZnO nanorods for efficient third harmonic UV generation

“…Characterization of such pulses is rendered complex by the ultrashort, broadband, nature of such pulses (> 100 nm) where dispersive effects can be dominant and thus one needs extremely thin nonlinear crystals for faithful pulse characterization [8]. Recently our group has demonstrated the use of TiO 2 nanocrystalline thin films to characterize pulses as short as 20 fs, demonstrating the utility of nanostructured metal oxides for such applications, where the nano length scales allow one to avoid phase-matching constraints associated with traditional bulk nonlinear materials [9].…”