In application of ultra-short laser pulses the pulse parameters have to be controlled accurately. Hence the manipulation of the propagation behavior of ultra-short pulses requires for specially designed optics. We have developed a tool for the simulation of ultra-short laser pulse propagation through complex real optical systems based on a combination of ray-tracing and wave optical propagation methods. For the practical implementation of the approach two commercially available software packages have been linked together, which are ZEMAX and Virtual Optics Lab. The focussing properties of different lenses will be analyzed and the results are demonstrated.
The uneven illumination of a Gaussian profile makes quantitative analysis highly challenging in laser-based wide-field fluorescence microscopy. Here we present flat-field illumination (FFI) where the Gaussian beam is reshaped into a uniform flat-top profile using a high-precision refractive optical component. The long working distance and high spatial coherence of FFI allows us to accomplish uniform epi and TIRF illumination for multi-color single-molecule imaging. In addition, high-throughput borderless imaging is demonstrated with minimal image overlap.
We demonstrate a powerful and practical spectral interferometer with near-field scanning microscopy (NSOM) probes for measuring the spatiotemporal electric field of tightly focused ultrashort pulses with high spatial and spectral resolution. Our measurements involved numerical apertures as high as 0.44 and yielded the spatiotemporal field at and around the foci produced by two microscope objectives and several different lenses. For the first time, we measure the spatiotemporal field of the Bessel-like X-shaped pulse caused by spherical aberrations and a "fore-runner pulse" due to chromatic aberrations. We observed spatial features smaller than 1 microm and verified these results with non-paraxial simulations.
We report on the fabrication of highly efficient fiber Bragg gratings (FBG) in non-photosensitive fibers based on nonlinear absorption of fs laser light. Up to 40 mm long gratings with a transmission of T = -25 dB at the Bragg reflection wavelength were obtained and their coupling constant determined by spectral analysis. Therefore, a phase mask scanning technique with appropriate control of the focus was established
We report the inscription of fiber Bragg gratings (FBGs) into a nonphotosensitive Er-doped fiber by using a phase-mask scanning technique with near IR femtosecond laser pulses. A grating of 40 mm length with a period of 1.075 microm was realized. We measured transmission losses of -18.9 dB at lambda=1554.5 nm with a FWHM bandwidth of 0.15 nm. By pumping the fiber containing the fabricated FBG, it was possible to realize a fiber laser with an output power of 38 mW, a slope efficiency of 21.1%, and low noise (SNR=60 dB).
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