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We present theory and simulations for a spectral narrowing scheme for laser diode arrays (LDAs) that employs optical feedback from a diffraction grating. We calculate the effect of the so-called smile of the LDA and show that it is possible to reduce the effect by using a cylindrical lens set at an angle to the beam. The scheme is implemented on a 19-element LDA with smile of 7.6 μm and yields frequency narrowing from a free-running width of 2 to 0.15 nm. The experimental results are in good agreement with the theory.

Report of a case of SESA syndrome: a rare CNS complication of chronic alcoholism, known since 19811and characterized by epileptic seizures, multiple and reversible neurological deficits, as well as PLEDs in the EEG. The MRI showed enhanced occipital signals in the T2-weighted sequence, which resolved together with the clinical findings.

We demonstrate a three-dimensional scanning probe microscope in which the extremely soft spring of an optical tweezers trap is used. Feedback control of the instrument based on backscattered light levels allows three-dimensional imaging of microscopic samples in an aqueous environment. Preliminary results with a 2-µm-diameter spherical probe indicate that features of approximately 200 nm can be resolved, with a sensitivity of 5 nm in the height measurement. The theoretical resolution is limited by the probe dimensions.

In two patients with femoro-popliteal bypass using autogenous saphenous vein, aneurysmatic dilatation of the transplants occurred after a follow-up of 4 and 20 years. In the inner thrombus layer of the aneurysms side-branches could be shown by transfemoral angiography. A special microcorrosion cast technique for SEM-analysis was able to make a vascular network visible, which spread within the inner thrombus layer of the aneurysms. Venules were found predominantly. According to clinical and experimental results the potential of the phylogenetic older venous system is greater than the ability of the arterial system.

A single-beam gradient trap could potentially be used to hold a stylus for scanning force microscopy. With a view to development of this technique, we modeled the optical trap as a harmonic oscillator and therefore characterized it by its force constant. We measured force constants and resonant frequencies for 1–4-μm-diameter polystyrene spheres in a single-beam gradient trap using measurements of backscattered light. Force constants were determined with both Gaussian and doughnut laser modes, with powers of 3 and 1 mW, respectively. Typical values for spring constants were measured to be between 10^−6 and 4 × 10^−6 N/m. The resonant frequencies of trapped particles were measured to be between 1 and 10 kHz, and the rms amplitudes of oscillations were estimated to be around 40 nm. Our results confirm that the use of the doughnut mode for single-beam trapping is more efficient in the axial direction.

We show theoretically and demonstrate experimentally that highly absorbing particles can be trapped and manipulated in a single highly focused Gaussian beam. Our studies of the effects of polarized light on such particles show that they can be set into rotation by elliptically polarized light and that both the sense and the speed of their rotation can be smoothly controlled.

It is shown that multicarrier modulation with low peak-to-average power ratio (PAPR) of the transmitted waveform can be performed. As an example, a 32-carrier OFDM (orthogonal frequency division multiplexing) scheme with a PAPR of <3.3 dB is presented.

Polyphase sequences are finite, complex, time-discrete sequences with constant magnitude and variable phase. A polyphase sequence with elements of magnitude 1 is called a Barker sequence if the maximum magnitude of all sidelobes of their aperiodic autocorrelation function (ACF) is less than or equal to 1. Stochastic optimisation algorithms have been applied to search for polyphase Barker sequences. New sequences meeting the Barker condition up to length 31 have been found.