Ray-based simulation of the propagation of light with different degrees of coherence through complex optical systems.

We show the functional extension of a standard ray tracer to be capable of tracing light fields of different degrees of coherence through complex optical systems. The light fields are represented by spherical waves. An approximate reconstruction of the optical field is possible at arbitrary positions in an optical system under investigation.

Method to determine the speckle characteristics of front projection screens.

We present a method to determine the speckle properties of front projection screens. Seven different screens are investigated in a backscattering geometry for 808 nm light. The speckle contrast reduction that results from polarization scrambling and reduced temporal coherence is modeled for the case of volume scattering in the screens.

Nanostructuring of organic-inorganic hybrid materials for distributed feedback laser resonators by two-photon polymerization.

With two-photon absorption induced polymerization arbitrary three dimensional nano- and microstructures can be patterned directly into photoresists. We report on the fabrication of a low threshold organic semiconductor distributed feedback laser using the technique of two-photon absorption induced polymerization. A surface grating with 400 nm periodicity and 40 nm height modulation was fabricated by two-photon absorption induced polymerization in the organic-inorganic hybrid material ORMOCER.

Low-speckle laser projection with a broad-area vertical-cavity surface-emitting laser in the nonmodal emission regime.

We demonstrate low-speckle laser projection using a broad-area vertical-cavity surface-emitting laser (VCSEL) emitting at 840 nm wavelength as the illumination source. By driving the source in a nonmodal emission regime, we were able to achieve speckle contrast values as low as 3.5% in a realistic projection setup.

Optical characterization of photonic crystal slabs using orthogonally oriented polarization filters.

We present an experimental method for direct analysis of guided-mode resonances in photonic crystal slab structures using transmission measurements. By positioning the photonic crystal slab between orthogonally oriented polarization filters light transmission is suppressed except for the guided-mode resonances. Angle resolved transmission measurements with crossed polarizers are performed to obtain the band structure around the Gamma-point.

High-repetition-rate white-light pump-probe spectroscopy with a tapered fiber.

We have realized a 76 MHz white-light differential transmission spectroscopy system. The technique employs a Ti:sapphire laser oscillator and a tapered fiber to generate a white-light continuum spanning almost the full visible to near-infrared spectral range. Using acousto-optical modulation and subsequent lock-in detection, transient relative transmission changes as small as 10(-5) are detected.