Ulrike Fuchs

Erbium fiber laser based on intracore femtosecond-written fiber Bragg grating

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).

Ultra-short pulse propagation in complex optical systems.

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.

Hybrid optics for focusing ultrashort laser pulses

We present a specially designed hybrid optics comprising refraction and diffraction effects for tight spatial and temporal focusing of ultrashort laser pulses. Both aims can be put into practice by having a high numerical aperture (NA=0.45) and low internal dispersion at the same time. We are presenting what we believe is the first experimental realization of such a hybrid short plus focusing optics. The focusing properties are compared with a commonly used microscope objective (20 X, NA = 0.45) in theory and experimentally.

Flexible and robust beam shaping concepts with aspherical surfaces

The potpourri of aspherical surfaces offers many possibilities in optical design, even the chance for flexible beam shaping setups. Since these are refractive optical elements the beam shaping is robust with respect to wavelength changes.

Measuring the spatio-temporal electric field of tightly focused ultrashort pulses

We demonstrate a spectral interferometer with NSOM probes for measuring focusing ultrashort pulses with high spatial and temporal resolution. We measure a 0.26 NA focus and, for the first time, we observe the forerunner pulse.

Flat-field illumination for quantitative fluorescence imaging

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.

Enhanced measuring range with aspheric transmission spheres

The demands on optical metrology such as Fizeau interferometers increase steadily. Typically, a Fizeau lens design consists exclusively of several spheres. Since there is a growing need for larger measuring ranges as well as higher NA of Fizeau lenses, classical spherical Fizeau lenses increasingly reaching their limits. In this paper, a prototype of an innovative transmission sphere comprising aspheric surfaces is introduced and some results and new findings of the manufacturing and testing are presented.

Control your Freeform Surface Form Deviation and Centration - It is only a Matter of Balance

Freeform surfaces enable numerous new applications. However, they imply new challenges as well. Due to lots of degrees of freedom, it is possible to compensate some tolerances for each other.

High NA Aspheric Fizeau Lens with Large Aperture Diameter

An aspheric design of a high NA Fizeau lens is introduced, which has many advantages in comparison to a common spherical design. Additionally, measurement results of the lenses and the objectives are presented.

Tolerancing aspheres based on manufacturing statistics

After years of robust manufacturing of aspheric lenses, a comprehensive statistical analysis was carried out. The results obtained are extremely valuable and can be used to increase the efficiency of optical tolerancing processes.