We present a new Optical Parametric Oscillator (OPO) based on collinear, quasi phase-matched interaction in a
periodically poled crystal (PP-crystal) with an integrated extra-cavity prism compressor delivering Signal pulses with
durations as low as 30 fs around 1150 nm center wavelength. The design matching between the Ti:Sapphire pump laser
(Coherent Micra-10 or MiraV10), the PP-crystal and the intra-cavity dispersion compensation of the OPO enables stable
Signal emission covering a spectral region from 1050 nm to 1250 nm with pulse energies exceeding 4.5nJ. Tunability of
the Signal pulses between 1130 nm and 1200 nm is given at reduced bandwidth.
We will present a new flexible laser source for multimodal Multiphoton excitation microscopy including CARS. It
consists of a tuneable femtosecond-Ti:Sapphire laser and an optical parametric oscillator (OPO). The new OPO-design
allows for high flexibility in pump- and output wavelengths giving rise to for instance image EGFP with the Ti:Sapphire
and tdRFP with the OPO simultaneously. This is presented on living mouse brain tissue.
The minimum energy difference between Ti:Sapphire and
OPO-wavelengths achievable is 2500cm<sup>-1</sup>. Thus CARS
imaging of lipids is possible. Due to synchronous pumping of the OPO the pump- and OPO pulses are intrinsically
locked in time to each other thus they can be brought to perfect overlap of pump and stokes pulses. Uncaging
multiphoton microscopy is also possible with this system due to the low minimum OPO pump wavelength of 730nm.
Novel types of thin-film microoptical components have been found very advantageous for beam shaping of high-power and ultrashort-pulse lasers. Measuring techniques, nonlinear optics, materials processing, and further advanced photonic applications, will benefit from specific advantages. Compared to conventional microoptics, low dispersion and absorption as well as added degrees of freedom in structure and functionality are accessible. Single or multilayer designs, spherical and non-spherical profiles, extremely small angles, and flexible substrates enable key components for the tailoring of lasers in spatial, temporal, and spectral domain at extreme parameters. By vacuum deposition and selective etching transfer, a cost-effective fabrication of single or array-shaped refractive, reflective, or hybrid components is possible. During the last decade significant progress in this field could be achieved. Including very recent applications for spatio-temporal shaping and characterization of complex and non-stationary laser fields, the state of the art is presented here. Particular emphasis is put on the generation of localized few-cycle wavepackets from Ti:sapphire laser beams by the aid of broadband microaxicons. Special microoptics are capable of transforming vacuum ultraviolet radiation. Wavefronts of strongly divergent sources can be analyzed by advanced Shack-Hartmann sensors based on microaxicon-arrays. Single-maximum nondiffractive beams are generated by different approaches for self-apodizing systems. Prospects for future developments, like robust multichannel information processing with arrays of self-reconstructing X-pulses, are discussed.
Using near-field scanning optical microscopy and ultrafast laser spectroscopy, we study the linear optical properties of subwavelength nanoslit and nanohole arrays in metal films, which are prototype structures for novel plasmonic crystals. Near-field microscopy provides direct evidence for surface plasmon polariton (SPP) excitation and allows for spatial imaging of the corresponding SPP modes. By employing spectral interferometry with ultrashort 11-fs light pulses, we directly reconstruct the temporal structure of the electric field of these pulses as they are transmitted through the metallic nanostructures. The analysis of these data allows for a quantitative extraction of the plasmonic band structure and the radiative damping of the corresponding SPP modes. Clear evidence for plasmonic band gap formation is given. Our results reveal that the coherent coupling between different SPP modes can result in a pronounced suppression of radiative SPP damping, increasing the SPP lifetime from 30 fs to more than 200 fs. These findings are relevant for optimizing and manipulating the optical properties of novel nano-plasmonic devices.
Ultrashort-pulse single-maximum nondiffracting beams of microscopic radius and large axial depths are interesting for applications in nonlinear optics and spectroscopy, for acceleration and manipulation of particles, measuring techniques, materials treatment or information processing. Here we report on the experimental generation of such beams by self-apodized truncation of Bessel and pseudo-Bessel beams from a Ti:sapphire oscillator. Small angle operation was enabled by thin-film structures. To obtain self-apodization, the diameter of the truncating diaphragm was adapted to the first minima of Bessel distribution. The propagation of (a) Bessel beams of meter-range axial extension shaped by axicon mirrors, and (b) microscopic pseudo-Bessel beams of millimeter-range extension shaped by Gaussian-shaped microaxicon lenses was studied. In case (a), single-maximum beams of > 20 cm depth were produced. To generate comparable focal zones from Gaussian beams, a much larger distance (10x) is necessary, and axial stretching of spectrum destructs the temporal structure. In case (b), the focal zone length was increased by a factor of >5 compared to a Gaussian beam. Arrays of truncated Bessel beams were generated as well. The experimental results indicate that truncated Bessel beams enable more compact setups than corresponding Gaussian beams and are in particular advantageous for ultrashort pulses. Further improvements are possible by combining coherent addition in resonators with truncation outcoupling.