We report on a direct experimental observation of dynamic localization (DL) of light in sinusoidally-curved lithium-niobate waveguide arrays which provides the optical analog of DL for electrons in periodic potentials subjected to ac electric fields as originally proposed by Dunlap and Kenkre [ Phys. Rev. B 34, 3625 (1986)]. The theoretical condition for DL in a sinusoidal field is experimentally demonstrated.

We describe a novel approach for the fabrication of optical waveguides by focused low-repetition-rate femtosecond laser pulses. This approach overcomes the main limitation of the technique, i.e., the strong asymmetry of the waveguide profile. By use of an astigmatic beam and suitably controlling both beam waist and focal position in tangential and sagittal planes, it is possible to shape the focal volume in such a way as to obtain waveguides with a circular transverse profile and of the desired size. This technique is applied to the fabrication of active waveguides in Er:Yb-doped glass substrates. The waveguides are single mode at 1.5 μm and exhibit propagation losses of ∼0.25 dB/cm and an internal gain of 1.4 dB at 1534 nm.

Phase-locked single-cycle transients with frequency components between 1 and $60\mathrm{THz}$ and peak fields of up to $12\mathrm{MV}/\mathrm{cm}$ are generated as the idler wave of a parametric amplifier. To achieve broadband conversion in GaSe nonlinear crystals, we match the group velocities of signal and idler components. The influence of group-velocity dispersion is minimized by long-wavelength pumping at $1.18\mathrm{\mu m}$. Free-space electro-optic sampling monitors the multiterahertz waveforms with direct field resolution.

Spontaneous Raman (SR) microscopy allows label‐free chemically specific imaging based on the vibrational response of molecules; however, due to the low Raman scattering cross section, it is intrinsically slow. Coherent Raman scattering (CRS) techniques, by coherently exciting vibrational oscillators in the focal volume, increase signal levels by several orders of magnitude under appropriate conditions. In its single‐frequency version, CRS microscopy has reached very high imaging speeds, up to the video rate; however, it provides information which is not sufficient to distinguish spectrally overlapped chemical species within complex heterogeneous systems, such as cells and tissues. Broadband CRS combines the acquisition speed of CRS with the information content of SR, but it is technically very demanding. In this Review, the current state of the art in broadband CRS microscopy, both in the coherent anti‐Stokes Raman scattering (CARS) and the stimulated Raman scattering (SRS) versions are reviewed. Different technical solutions for broadband CARS and SRS, working both in the frequency and in the time domains, are compared and their merits and drawbacks assessed.

We report on a new spatial beam-shaping approach for fabrication of waveguides with a circular transverse profile by femtosecond laser pulses, using an astigmatic beam and controlling both beam waist and focal position in the tangential and sagittal planes. We apply this technique to write single-mode active waveguides at $1.5 \mathit{\mu }\mathrm{m}$ in Er:Yb-doped glass substrates. The experimental results are well described by a simple nonlinear absorption model.