RESUMEN
A test station setup devised to measure the emission characteristics and beam propagation parameters of a light detection and ranging (LiDAR) system is presented. The main blocks of the station to measure the accessible emission, wavelength peak and FWHM, pulse duration, pulse repetition rate, horizontal and vertical angular resolution, field of view, beam propagation factor M 2, beam waist size, waist location, and divergence are described. The performance of this test station was demonstrated using a commercial spinning LiDAR, a Velodyne VLP-16, which successfully enables these measurements for a laser beam with a wavelength of 913 nm.
RESUMEN
The potential use of nanostructured dipeptide self-assemblies in materials science for energy harvesting devices is a highly sought-after area of research. Specifically, aromatic cyclo-dipeptides containing tryptophan have garnered attention due to their wide-bandgap semiconductor properties, high mechanical rigidity, photoluminescence, and nonlinear optical behavior. In this study, we present the development of a hybrid system comprising biopolymer electrospun fibers incorporated with the chiral cyclo-dipeptide L-Tryptophan-L-Tyrosine. The resulting nanofibers are wide-bandgap semiconductors (bandgap energy 4.0 eV) consisting of self-assembled nanotubes embedded within a polymer matrix, exhibiting intense blue photoluminescence. Moreover, the cyclo-dipeptide L-Tryptophan-L-Tyrosine incorporated into polycaprolactone nanofibers displays a strong effective second harmonic generation signal of 0.36 pm/V and shows notable piezoelectric properties with a high effective coefficient of 22 pCN-1, a piezoelectric voltage coefficient of geff=1.2 VmN-1 and a peak power density delivered by the nanofiber mat of 0.16µWcm-2. These hybrid systems hold great promise for applications in the field of nanoenergy harvesting and nanophotonics.
RESUMEN
A polymorph of glycyl-L-alanine HI.H2O is synthesized from chiral cyclo-glycyl-L-alanine dipeptide. The dipeptide is known to show molecular flexibility in different environments, which leads to polymorphism. The crystal structure of the glycyl-L-alanine HI.H2O polymorph is determined at room temperature and indicates that the space group is polar (P21), with two molecules per unit cell and unit cell parameters a = 7.747 Å, b = 6.435 Å, c = 10.941 Å, α = 90°, ß = 107.53(3)°, γ = 90° and V = 520.1(7) Å3. Crystallization in the polar point group 2, with one polar axis parallel to the b axis, allows pyroelectricity and optical second harmonic generation. Thermal melting of the glycyl-L-alanine HI.H2O polymorph starts at 533 K, close to the melting temperature reported for cyclo-glycyl-L-alanine (531 K) and 32 K lower than that reported for linear glycyl-L-alanine dipeptide (563 K), suggesting that although the dipeptide, when crystallized in the polymorphic form, is not anymore in its cyclic form, it keeps a memory of its initial closed chain and therefore shows a thermal memory effect. Here, we report a pyroelectric coefficient as high as 45 µC/m2K occurring at 345 K, one order of magnitude smaller than that of semi-organic ferroelectric triglycine sulphate (TGS) crystal. Moreover, the glycyl-L-alanine HI.H2O polymorph displays a nonlinear optical effective coefficient of 0.14 pm/V, around 14 times smaller than the value from a phase-matched inorganic barium borate (BBO) single crystal. The new polymorph displays an effective piezoelectric coefficient equal to deff=280 pCN-1, when embedded into electrospun polymer fibers, indicating its suitability as an active system for energy harvesting.
RESUMEN
Optical frequency conversion via the nonlinear effect of third harmonic generation is shown to be resonantly enhanced in few-layer black phosphorus. This feature is believed to be a consequence of exciton-related resonance, as the enhancement is strongly correlated with the observation of exciton-recombination photoluminescence. Few-layer thicknesses are obtained both via mechanical exfoliation and laser thinning.
