2021, Nayak, Abani Shankar, Labadie, Lucas, Sharma, Tarun Kumar, Piacentini, Simone, Corrielli, Giacomo, Osellame, Roberto, Gendron, Éric, Buey, Jean-Tristan M., Chemla, Fanny, Cohen, Mathieu, Bharmal, Nazim A., Bardou, Lisa F., Staykov, Lazar, Osborn, James, Morris, Timothy J., Pedretti, Ettore, Dinkelaker, Aline N., Madhav, Kalaga V., Roth, Martin M.

We present the first on-sky results of a four-telescope integrated optics discrete beam combiner (DBC) tested at the 4.2mWilliamHerschel Telescope. The device consists of a four-input pupil remapper followed by a DBC and a 23-output reformatter. The whole device was written monolithically in a single alumino-borosilicate substrate using ultrafast laser inscription. The device was operated at astronomical H-band (1.6 μm), and a deformable mirror along with a microlens array was used to inject stellar photons into the device. We report the measured visibility amplitudes and closure phases obtained on Vega and Altair that are retrieved using the calibrated transfer matrix of the device. While the coherence function can be reconstructed, the on-sky results show significant dispersion from the expected values. Based on the analysis of comparable simulations, we find that such dispersion is largely caused by the limited signal-to-noise ratio of our observations. This constitutes a first step toward an improved validation of theDBCas a possible beam combination scheme for long-baseline interferometry. © 2021 Optical Society of America.

2021, Alber, Lukas, Scalera, Valentino, Unikandanunni, Vivek, Schick, Daniel, Stefano Bonetti

The NTMpy code package allows for simulating the one-dimensional thermal response of multilayer samples after optical excitation, as in a typical pump-probe experiment. Several Python routines are combined and optimized to solve coupled heat diffusion equations in one dimension, on arbitrary piecewise homogeneous material stacks, in the framework of the so-called three-temperature model. The energy source deposited in the material is modelled as a light pulse of arbitrary cross-section and temporal profile. A transfer matrix method enables the calculation of realistic light absorption in presence of scattering interfaces as in multilayer samples. The open source code is fully object-oriented to enable a user-friendly and intuitive interface for adjusting the physically relevant input parameters. Here, we describe the mathematical background of the code, we lay out the workflow, and we validate the functionality of our package by comparing it to commercial software, as well as to experimental transient reflectivity data recorded in a pump-probe experiment with femtosecond light pulses.