While animals have access to sugars as energy source, this option is generally not available to artificial machines and robots. Energy delivery is thus the bottleneck for creating independent robots and machines, especially on micro- and nano- meter length scales. We have found a way to produce polymeric nano-structures with local control over the molecular alignment, which allowed us to solve the above issue. By using a combination of polymers, of which part is optically sensitive, we can create complex functional structures with nanometer accuracy, responsive to light. In particular, this allowed us to realize a structure that can move autonomously over surfaces (it can “walk”) using the environmental light as its energy source. The robot is only 60 μm in total length, thereby smaller than any known terrestrial walking species, and it is capable of random, directional walking and rotating on different dry surfaces.
Time evolution of the laser light intensity from a self-starting Yb:KYW femtosecond laser with passive mode-locking is
presented. One photon and two photon signal transients have been recorded for a few hundred microseconds after
opening the laser cavity, and transition from continuous wave to pulsed operation is observed. The collected data are
divided into two common types of evolution, with different transition phases and their characteristics are discussed.
We report the first demonstration of laser wavelength tuning with a resonant grating in the mid-infrared spectral
domain and with Littrow mounting of the grating. We show for a mid-infrared Cr:ZnSe solid-state laser that this
tuning technique is much more wavelength selective than prism-based tuning, while inducing significantly lower
cavity losses than in the case of a standard metal-coated grating. Furthermore, the resonant grating allows tuning
the Cr:ZnSe laser over as much as 400 nm around a center wavelength of 2.38 μm. This shows the potential of
employing Littrow-mounted resonant diffraction gratings for controlling and tuning the emission wavelength of
lasers emitting in the mid-infrared spectral domain and other wavelength regions.
We present experimental realization of nonlinear and highly birefringent microstructure fiber fabricated from silicate glass. Using full vector FEM mode solver the numerical analysis of reported fiber is performed and its modal, polarization and dispersive properties are investigated. Particularly, the calculations reveals guidance of two orthogonally polarized eigenmodes with the difference of its effective indexes B=0.0025 for wavelength λ=1.55 μm. Additionally, spectral broadening of the 50 fs Ti:Sapphire laser impulses with average power 150mW coupled into 39 cm section of the fiber is observed.
We present an experimental and theoretical study of the nonlinear propagation of 90 fs laser pulses at 800 nm in bulk fused silica. An unexpected behavior of the off-axis emission for pulse energy corresponding to the supercontinuum generation threshold has been discovered. Our model, based on 3D Nonlinear Schrodinger Equation, well explains the observed nonlinear dynamics. For the first time we experimentally confirm that the onset of the supercontinuum generation is inevitably accompanied by the pulse collapse in transverse dimensions.
We present angularly resolved spectra of 65 fs laser pulses at 800 nm after propagation through bulk fused silica. For the first time we report angular dependence of the spectrum after propagation in a solid sample far from resonances. Reproducible spectral and spatial effects have been observed for pulse powers several times above critical power for self-focusing.
We have studied, theoretically and experimentally, nonlinear propagation of 90 fs laser pulses at 800 nm in bulk fused silica samples. For the first time, we present comparisons between numerically simulated and experimentally measured angle-resolved, far-field spectra for such pulses. They are in good agreement for pulse powers up to, approximately, critical power for self focusing.