Linear and nonlinear processes of transferring optical singularities from anisotropic crystals onto the wavefront of Bessel light beams (BLBs) are investigated. The generation of high-order vortices at the propagation of BLBs along the optical axes of crystals was studied. Particularly, a nonlinear frequency doubling of Bessel vortices in the conditions of new type synchronism (full conical pha...

Tunable 90-ps 15.6-17.6-microm coherent radiation was generated by means of difference-frequency mixing in diffusion-bonded-stacked GaAs. The sample consisted of 24 alternately rotated layers with a total length of 6 mm and with low optical loss to achieve third-order quasi-phase matching. The wavelength-tuning curve was close to the theoretical prediction, demonstrating that the bonding proces...

A novel group velocity mismatch (GVM) absent scheme for nonlinear optical parametric procedure in mid-infrared was developed with type-I quasi phase matching by use of an off-digital nonlinear optical coefficient d31. This was achieved by matching of the group velocities of the pump and the signal waves, while the phase velocities were quasi phase matched. The system employs MgO-doped periodica...

We demonstrate simultaneous phase matching of two different nonlinear processes, using a noncollinear interaction in periodically poled crystal with single grating. The noncollinear scheme provides phase-matching solutions over continuous regions of the optical spectrum and can be used for multiple-harmonic generation as well as all-optical effects. We have demonstrated experimentally third-har...

Applications of subwavelength-diameter optical fibres in nonlinear optics require precise knowledge of the submicrometre fibre waist diameter. We demonstrate a new technique for optical measurement of the diameter based on second- and third-harmonic generation with an accuracy of better than 2%. To generate the harmonic light, inter-modal phase matching must be achieved. We find that the phase-...

We present measurements on terahertz generation by optical rectification, in which both the thickness of the generation crystal and the wavelength of the generating optical pulse are varied. The difference between the group velocity at optical frequencies and the phase velocity at terahertz frequencies affects the time trace and spectrum of the generated terahertz pulse. For the thickest crysta...

All-optical wavelength conversion of a complex (amplitude and phase) optical signal is proposed based on an all-optical implementation of time-domain holography. The temporal holograms are generated through a cross-phase modulation (XPM) process in a highly-nonlinear optical fiber, avoiding the necessity of accomplish the phase matching condition between the involved pump and probe signals, and...

We describe a new optical phase erasure characteristic of periodically poled lithium niobate (PPLN) by using cascaded second-harmonic generation and difference-frequency generation with the signal set at the quasi-phase-matching wavelength. A simple analytical expression is derived clearly explaining the operation principle. It is interesting that the optical phase erasure feature enables an al...

Quasi-phase-matched (QPM) wavelength converters are highly desirable for emerging nonlinear optics applications in photonic integrated circuits, but available waveguide and quasi-phase-matching technologies have so far constrained their realization. In this work, we present a periodically poled lithium niobate (LN) waveguide on a silicon nitride– thin film LN platform. It contains a submicromet...