Second harmonic generation (SHG) in nonlinear optical crystal is well-established technique for the measurement of the pulse-width of ultrafast femtosecond laser pulses. However, only selected nonlinear crystalline materials are suited for this purpose due to the limitations in transparency cut-off, limited phase-matching wavelength range, and large difference between the group velocities of th...

Chiral spectroscopic study: The intensities of second harmonic generation chiral spectroscopy are obtained from the dispersion of the nonlinear optical susceptibility components, as a function of wavelength for helicenbisquinone thin films (see figure). A single formalism fits all the data simultaneously, and the findings constitute an important milestone towards the development of a new experi...

Non-linear optics encompasses a range of optical phenomena, including two- and three-photon fluorescence, second harmonic generation (SHG), sum frequency generation (SFG), difference frequency generation (DFG), third harmonic generation (THG), coherent anti-Stokes Raman scattering (CARS), and stimulated Raman scattering (SRS). The combined advantages of using these phenomena for imaging complex...

We analyze two-component spatial optical vortex solitons supported by parametric wave mixing processes in a nonlinear bulk medium. We study two distinct cases of such localized waves, namely, parametric vortex solitons due to phase-matched second-harmonic generation in an optical medium with competing quadratic and cubic nonlinear response, and vortex solitons in the presence of third-harmonic ...

We present studies of the optical properties of the new nonlinear material BiB3O6 for second harmonic generation from the visible to infrared. We have determined the phase-matching conditions and effective nonlinear coefficients in the three principal optical planes, acceptance bandwidths, spatial and temporal walkoff, group velocity dispersion and double phase-matching behaviour. We also repor...

We observe enhanced third-harmonic generation from silicon nanodisks exhibiting both electric and magnetic dipolar resonances. Experimental characterization of the nonlinear optical response through third-harmonic microscopy and spectroscopy reveals that the third-harmonic generation is significantly enhanced in the vicinity of the magnetic dipole resonances. The field localization at the magne...

We investigate laser high-order harmonic generation in the presence of interfering light. A relatively weak interfering pulse intersects the primary harmonic-generating laser pulse at the focus. The influence on the harmonic-generation process is studied at near-counterpropagating and at perpendicular angles. The interfering beam creates a standing intensity and phase modulation, which disrupts...

Using a surface integral equation approach based on the tangential Poggio–Miller–Chang–Harrington–Wu–Tsai formulation, we present a full wave analysis of the resonant modes of 3D plasmonic nanostructures. This method, combined with the evaluation of second-harmonic generation, is then used to obtain a better understanding of their nonlinear response. The second-harmonic generation associated wi...

Advancing the practical utility of nonlinear optical microscopy requires continued improvement in imaging depth and contrast. We evaluated second-harmonic generation (SHG) and third-harmonic generation images from ex vivo human skin and showed that a sub-40 fs, 1060-nm Yb-fiber laser can enhance SHG penetration depth by up to 80% compared to a >100 fs, 800 nm Ti:sapphire source. These results d...

We demonstrate a new time-domain surface phonon spectroscopy. We excite coherent surface optical phonons with an ultrashort laser pulse and probe the free-induction decay with time-resolved surface second-harmonic generation. For both clean GaAs (110) and (100) surfaces, the signals are remarkably large due to the highly localized electron-phonon interaction at the surface and the intrinsic sur...