Conference Agenda

Optical tweezers are designed to trap nano- and micro-scale particles. Once trapped, it is possible to move the particles but this requires complex mechanical adjustments to the optical system. In this paper, an easier way to trap and move multiple particles simultaneously is proposed, that uses a digital mirror-array and freeform micro-lens-array to generate several steerable optical traps inside a light-field.

The first practical step in resolving the turbulence issue in satellite-to-earth laser communications has been the use of conventional adaptive optics systems. The concept of a modal iterative approach is presented in this study, which combines some of the characteristics of the indirect methods outlined. This allows for a significant decrease in the loop bandwidth consumption throughout the iterative process. With the assumption that each speckle may be Fourier linked to a plane wave mode in the pupil plane, this approach employs the individual speckles of a single short-exposure intensity image. The approach is described, together with the general mathematical background. In the end, this work presents a numerical analysis of the approach performance estimate in a turbulent satellite downlink scenario.

At PTB, a multi camera measurement setup is developed for the traceable determination of the modulation transfer function (MTF) of objectives. In recent works the MTF of a reference objective is determined within the image field in an angular range of up to ±20° to the optical axis. For the investigation of angular dependency of the transfer function the MTF for a given spatial frequency is evaluated at a datum point. A common choice of the datum point is the focus point P_f.

There are different methods to obtain the focus point from the measurement data. In this contribution several approaches for the determination of the focus point are investigated and compared. In addition, owing to the temperature depending extension of the measurement setup the position of the focus point strongly depends on the ambient temperature. We present also some results of the investigations on the influence of temperature changes on the position of the focus point.

The FAMU (Fisica degli Atomi MUonici) collaboration aims to measure the proton Zemach radius through muonic hydrogen (µp) spectroscopy. The experimental setup relies on a custom-developed pulsed mid-IR laser source that can be tuned over a specific 6780-6790 nm wavelength range needed to ignite the hyperfine transition of the µp ground state 1S (also known as spin-flip transition). The excitation is observed as a distinctive muonic X-rays emission resulting from the oxygen impurity present in the hydrogen target. The mid-IR emission is produced by Difference Frequency Generation (DFG) in a non-linear crystal, pumped with a fixed wavelength 1064 nm Nd-YAG laser and a tuneable Cr:forsterite laser centred on 1262 nm. This setup produces more than 1.2 mJ at 6780 nm with a linewidth smaller than 30 pm. The experiment requires the laser to run continuously 24/7 in a restricted/radiation-controlled area and for this reason a specifically developed control software permits to remotely act on the laser. The characterization of a series of different non-linear crystals was performed during the development of the laser, resulting in the choice of BaGa4Se7.

Here we present a new light-responsive composite showing reversible anisotropic stretching in response to green laser irradiation with varying polarization. The elongation/compression parameters and the residual strain after deformation reversal are evaluated by means of a Fourier-based analysis, which exploits a periodic 2D pattern imprinted onto the surface. Two illustrative examples of macroscopic actuation driven by light polarization are demonstrated.