Two-dimensional coherent electronic spectrometer with switchable multi-color configurations.

Broadband implementation of two-dimensional electronic spectroscopy (2DES) is a desirable goal for numerous research groups, yet achieving it presents considerable challenges. An effective strategy to mitigate these challenges is the utilization of two-color approaches, effectively broadening the spectral bandwidth accessible with 2DES. Here, we present a simple approach to include multi-color configurations based on adjustable mirror mounts. This enables seamless toggling between single-color, two-color, and transient 2DES within the same spectroscopic apparatus, which is benchmarked on two common laser dyes, Rhodamine 6G and Nile blue. Upon mixing the dyes, single-color 2DES shows overlapping signals, whereas a high selectivity toward Nile blue responses is maintained in two-color and transient 2DES, owing to the fully resonant excitation that is spectrally shifted relative to the detection window. This method is readily implemented in other setups with similar experimental layouts and can be used as a simple solution to overcome existing bandwidth limitations. With the inclusion of transient 2DES, additional insights into excited-state processes can be gained due to its increased sensitivity toward excited-state coherences.

Neural-network-powered pulse reconstruction from one-dimensional interferometric correlation traces.

Any ultrafast optical spectroscopy experiment is usually accompanied by the necessary routine of ultrashort-pulse characterization. The majority of pulse characterization approaches solve either a one-dimensional (e.g., via interferometry) or a two-dimensional (e.g., via frequency-resolved measurements) problem. Solution of the two-dimensional pulse-retrieval problem is generally more consistent due to the problem's over-determined nature. In contrast, the one-dimensional pulse-retrieval problem, unless constraints are added, is impossible to solve unambiguously as ultimately imposed by the fundamental theorem of algebra. In cases where additional constraints are involved, the one-dimensional problem may be possible to solve, however, existing iterative algorithms lack generality, and often stagnate for complicated pulse shapes. Here we use a deep neural network to unambiguously solve a constrained one-dimensional pulse-retrieval problem and show the potential of fast, reliable and complete pulse characterization using interferometric correlation time traces determined by the pulses with partial spectral overlap.

Generation and compression of 10-fs deep ultraviolet pulses at high repetition rate using standard optics: erratum.

We present an erratum regarding the calculated phase matching bandwidths for achromatic second harmonic generation presented in our paper [Opt. Express29, 25593 (2021)10.1364/OE.425053].

Generation and compression of 10-fs deep ultraviolet pulses at high repetition rate using standard optics.

The generation and characterization of ultrashort laser pulses in the deep ultraviolet spectral region is challenging, especially at high pulse repetition rates and low pulse energies. Here, we combine achromatic second harmonic generation and adaptive pulse compression for the efficient generation of sub-10 fs deep ultraviolet laser pulses at a laser repetition rate of 200 kHz. Furthermore, we simplify the pulse compression scheme and reach pulse durations of ≈10 fs without the use of adaptive optics. We demonstrate straight-forward tuning from 250 to 320 nm, broad pulse spectra of up to 63 nm width, excellent stability and a high robustness against misalignment. These features make the approach appealing for numerous spectroscopy and imaging applications.

Cerebroprotective Effects of 2-Ethyl-6-methyl-3-hydroxypyridine-2,6-dichlorophenyl(amino)phenylethanoic Acid in the Treatment of Purulent Meningitis.

Purulent meningitis (PM) is a severe disease, characterized by high mortality and a formation of a residual neurological deficit. Loss of treatment of PM leads to the lethal outcome in 100% of cases. In addition, death and the development of residual neurological complications are possible despite adequate therapy. The aim of the study was to evaluate the cerebroprotective effects of a new pharmacological compound 2-ethyl-6-methyl-3-hydroxypyridine-2,6-dichlorophenyl(amino)phenylethanoic acid (EMHDPA) on the bacterial purulent meningitis in a model of experimental pneumococcal meningitis. Meningitis was simulated by intrathecal injection of the suspension containing Streptococcus pneumoniae at the concentration of 5 × 109 CFU/mL. The cerebroprotective effect was evaluated by survival rates, the severity of neurological deficit, investigatory behaviors, and results of short-term and long-term memory tests. The group administered with EMHDPA showed high survival rates, 80%. Animals treated with the studied compound showed a higher clinical assessment of the rat health status and specific force, and a lesser intensity of neurological deficit compared to the control group (p < 0.05). Locomotor activity of the animals treated with EMHDPA was significantly higher compared to the control group (p < 0.05). There is a decrease in the activity of all estimated indicators of oxidative stress in the group administered with 2-ethyl-6-methyl-3-hydroxypyridine-2,6-dichlorophenyl(amino)phenylethanoic acid relative to the control group: a decrease in the activity of catalase-17%, superoxide dismutase-34%, malondialdehyde and acetylhydroperoxides-50%, and nitric oxide-85% (p < 0.05). Analysis of the data obtained during the experiment leads to the conclusion about the effectiveness of 2-ethyl-6-methyl-3-hydroxypyridine-2,6-dichlorophenyl(amino)phenylethanoic acid in the treatment of the experimental PM.

Fully symmetric dispersionless stable transmission-grating Michelson interferometer.

Michelson interferometers have been routinely used in various applications ranging from testing optical components to interferometric time-resolved spectroscopy measurements. Traditionally, plate beamsplitters are employed to redistribute radiation between the two arms of an interferometer. However, such an interferometer is susceptible to relative phase fluctuations between the two arms resulting from vibrations of the beamsplitter. This drawback is circumvented in diffraction-grating-based interferometers, which are especially beneficial in applications where highly stable delays between the replica beams are required. In the vast majority of grating-based interferometers, reflective diffraction gratings are used as beamsplitters. Their diffraction efficiency, however, is strongly wavelength dependent. Therefore transmission-grating interferometers can be advantageous for spectroscopy methods, since they can provide high diffraction efficiency over a wide spectral range. Here, we present and characterize a transmission grating-based Michelson interferometer, which is practically dispersion-free, has intrinsically high symmetry and stability and moderate throughput efficiency, and is promising for a wide range of applications.