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We report on the experimental realization of zigzag waveguide lattices, where second-order coupling influences linear and nonlinear light evolution. Band structure deformation and changes in soliton thresholds are analyzed depending on higher-order coupling.
Fiber gratings allow in-line spectral control of the guided light and can be used as narrow-band reflectors or for the selective coupling of light into other fiber modes. However, fibers used in "state of the art"- fiber lasers possess material properties and geometries that make it difficult or impossible to inscribe gratings with standard cw-UV-Laser processing. These difficulties can...
This study presents a binary superlattice system, which consists of two quantum wells in the unit cell. The analogy of quantum mechanics and optics is utilized to map the time coordinate onto space, which enables convenient access to the spatial evolution. This binary waveguide array displays the Bloch-Zener dynamics and tunneling between the subbbands of the system. These structures are fabricated...
In this paper, we report on the experimental observation of discrete X-waves in a two-dimensional waveguide array fabricated by femtosecond laser direct writing technique in fused silica. This type of optical wave spontaneously emerges from a compact pulse injected into a single site due to the interplay of the lattice's discrete diffraction as well as normal dispersion and focusing Kerr nonlinearity.
The generation of picosecond electromagnetic pulses in the frequency range of 100 GHz to above 10 THz using ultrashort laser pulses is a well established technique by now. Over the past years, several different attempts have been made to increase the THz efficiency and output power, respectively. Especially, tomographic applications and spatial resolved spectroscopy require powerful THz radiation...
For THz ultrashort pulse imaging a high scan speed in combination with a high signal/noise ratio is required. Several methods have been presented to accelerate the classical one channel THz pulse detection. For example 2D electrooptic sampling provides a short scan time, but the signal/noise ratio is low and there is a need for an expensive low repetition fs-laser amplifier system to generate high...
We review the basic principles of the femtosecond laser direct writing approach. This technology opens the possibility to specifically tune the light evolution in the linear as well as in the nonlinear regime.
We present multichannel THz ultrashort pulse detection by a photoconductive antenna array consisting of 16 photoconductive antennas. The efficient excitation of the photoconductive antennas has been realized by a microlens array which creates 16 single spots from the exciting fs-laser beam. The detected THz signal/noise ratio has been improved by an order of magnitude in comparison to an excitation...
Powerful THz emission based on a finger electrode photoconductive switch attached to a micro lens array is presented. A hexagonal packed lens array directs the incident pump light into specified electrode gaps, yielding only constructive interference in the THz far-field. Using a Ti:Sapphire system operating at 80 MHz with 150 fs pulses and 3 W maximum optical excitation, 0.28 mW THz average power...
We investigate the propagation of ultrashort pulses in 2D fibre arrays both numerically and experimentally. The nonlinearity suppresses discrete diffraction and dispersion, leading to spatiotemporal contraction, as well as pulse breaking and supercontinuum (SC) generation.
We will discuss the status of high repetition rate high energy femtosecond fiber laser systems, review their scaling potential in terms of average power, pulse energy and peak power. First micro-machining applications demonstrate the potential of this laser technology.
We report on the first experimental observation of self-collimation of white-light beams in specially designed fs laser-written curved waveguide arrays, where discrete diffraction was suppressed over the spectral range extending from blue to infrared wavelengths.
We present the first experimental evidence of two-dimensional surface solitons at the interface between femtosecond laser-written square and hexagonal waveguide arrays in fused silica.
We present the first experimental observation of nonlinear beam diffusion and formation of diffraction-managed solitons in periodically-curved arrays of coupled optical waveguides created using femtosecond laser writing in silica glass, and titanium indiffusion in LiNbO3 crystals.
This paper demonstrates a quasi-incoherent evolution of fully coherent light in femtosecond laser written waveguide arrays. This effect is in strong contrast to the well-known spatial coherence for homogeneous media which describes a decreasing degree of coherence for an increasing distance between two sources.
Femtosecond inscription of fiber gratings into polarization maintaining (PM) fibers and large mode area (LMA) fibers is studied. Transmission spectra for a Bragg grating written in a panda PM fiber is obtained where the polarization orientation with respect to the index modification of the grating is of particular interest. Transmission spectrum of a grating written in a LMA fiber with large core...
Two types of waveguiding have been observed in LiNbO3. Both types of waveguides can be understood based on an analysis of the structural changes of the crystal. Here, waveguiding has been observed at the sides of the modification similar to structures in crystalline quartz. This can be explained by a volume change of the irradiated region and subsequent stress-induced birefringence in the surrounding...
Ultrashort-laser irradiation of silica-silicon interfaces is presented as new means for 'all solid- phase' formation of high-purity silicon-nanoparticles in a silica host. Compressive stress measured in the silicon substrate is associated with positive refractive index modification.
Electrooptical sampling (EOS) of ultrashort THz pulses with the help of fs-pulses at a wavelength of 1060 nm and (by second harmonic generation, SHG) of 530 nm is reported.
We report on the realization of FBGs in a standard Er-doped fiber written into the non-photosensitive core by femtosecond laser pulses. Efficient laser operation is demonstrated using this technique.
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