Optics (physics.optics)

Abstract: Signal processing based on stimulated Brillouin scattering (SBS) is limited by the narrow linewidth of the optoacoustic response, which confines many Brillouin applications to continuous wave signals or optical pulses longer than several nanoseconds. In this work, we experimentally demonstrate Brillouin interactions at the 150 ps time scale and a delay for a record 15 ns which corresponds to a delay of 100 pulse widths. This breakthrough experimental result was enabled by the high local gain of the chalcogenide waveguides as the optoacoustic interaction length reduces with pulse width. We successfully transfer 150ps-long pulses to traveling acoustic waves within a Brillouin-based memory setup. The information encoded in the optical pulses is stored for 15 ns in the acoustic field. We show the retrieval of eight amplitude levels, multiple consecutive pulses and low distortion in pulse shape. The extension of Brillouin-based storage to the ultra-short pulse regime is an important step for the realisation of practical Brillouin-based delay lines and other optical processing applications.

Abstract: Introducing a spatial chirp into a pulse with a longitudinal vortex, such as a standard pulsed Laguerre-Gauss beam, results in a vortex pulse with an arbitrary orientation of the line phase singularity between longitudinal and transverse, depending on the amount of chirp. Analytical expressions are given for such pulses with arbitrary topological charge valid at any propagation distance.

Abstract: SCAPS-1D software ignores optical losses and recombination junction (RJ) layer in studying tandem solar cells (TSCs). This paper presents an optoelectronic study of a perovskite/Silicon TSC, comparing the effects of using two different methods of calculating filtered spectra on the photovoltaic performance parameters of tandem device. It is shown that integrating transfer matrix (TM) method into SCAPS-1D addresses per-layer optical losses and provides a platform for optimizing the RJ layer in TSCs. Using Beer-Lambert (BL) method for calculating the filtered spectra transmitted from the perovskite top sub-cell is revealed to overestimate the cell efficiency by ~4%, due to its inability to fully address optical losses. Also, the BL method fails to tackle any issues regarding optical improvement through ITO ad-layer on the RJ. Using TM formalism, the efficiency of the proposed perovskite/Silicon TSC is shown to be increased from 19.81% to 23.10%, by introducing the ITO ad-layer on the RJ. It is the first time that the effect of filtered spectrum calculation method is clearly investigated in simulating TSCs with SCAPS-1D. The results pave the way to introduce the optical loss effects in SCAPS-1D and demonstrate that the BL method that has been used before needs to be revised.

Abstract: Ultraviolet (UV) imaging enables a diverse array of applications, such as material composition analysis, biological fluorescence imaging, and detecting defects in semiconductor manufacturing. However, scientific-grade UV cameras with high quantum efficiency are expensive and include a complex thermoelectric cooling system. Here, we demonstrate a UV computational ghost imaging (UV-CGI) method to provide a cost-effective UV imaging and detection strategy. By applying spatial-temporal illumination patterns and using a 325 nm laser source, a single-pixel detector is enough to reconstruct the images of objects. To demonstrate its capability for quantitative detection, we use UV-CGI to distinguish four UV-sensitive sunscreen areas with different densities on a sample. Furthermore, we demonstrate dark field UV-CGI in both transmission and reflection schemes. By only collecting the scattered light from objects, we can detect the edges of pure phase objects and small scratches on a compact disc. Our results showcase a feasible low-cost solution for non-destructive UV imaging and detection. By combining it with other imaging techniques, such as hyperspectral imaging or time-resolved imaging, a compact and versatile UV computational imaging platform may be realized for future applications.