Simplifying tailored generation of complex structured femtosecond pulses with easily fabricated phase plates.

This article presents a novel approach to targeted 4f pulse shaping using phase plates fabricated by single-point diamond turning (SPDT) machining. The manufacturing of the phase plates using SPDT is versatile, cost-effective, fast, robust, and applicable across a wide range of optical materials, spanning from visible to far-infrared spectra (e.g.

Dispersion scan frequency resolved optical gating for consistency check of pulse retrieval.

Many methods commonly used to characterize ultrafast laser pulses, such as the frequency-resolved optical gating (FROG) or the dispersion scan (d-scan), face problems when they are used on pulses with a spectrum or phase varying within the laser beam cross section or the acquisition time. The presence of such pulse shape variation leads to discrepancy between the measured FROG trace and its reconstructed counterparts. Nevertheless, it is difficult to reliably discern this shape variation because even the distorted experimental FROG trace can be reasonably reproduced by a realistic pulse shape.

Spatially encoded hyperspectral compressive microscope for ultrabroadband VIS/NIR hyperspectral imaging.

Hyperspectral imaging (HSI) has become a valuable tool in sample characterization in various scientific fields. While many approaches have been tested, specific applications and technology usually lead to only a narrow part of the spectrum being studied. We demonstrate the use of a broadband HSI setup based on compressed sensing capable of capturing data in visible (VIS), near-infrared (NIR), and short-wave infrared (SWIR) spectral regions.

On-chip digital holographic interferometry for measuring wavefront deformation in transparent samples.

This paper describes on-chip digital holographic interferometry for measuring the wavefront deformation of transparent samples. The interferometer is based on a Mach-Zehnder arrangement with a waveguide in the reference arm, which allows for a compact on-chip arrangement. The method thus exploits the sensitivity of digital holographic interferometry and the advantages of the on-chip approach, which provides high spatial resolution over a large area, simplicity, and compactness of the system.

Optically modified second harmonic generation in silicon oxynitride thin films via local layer heating.

Strong second harmonic generation (SHG) in silicon nitride has been extensively studied-among others, in terms of laser-induced SHG enhancement in SiN waveguides. This enhancement has been ascribed to the all-optical poling induced by the coherent photogalvanic effect. Yet, an analogous process for SiN thin films has not been reported.

Compact lensless Fizeau holographic interferometry for imaging domain patterns in ferroelectric single crystals.

Domain patterns in ferroelectric single crystals are physical systems that are fascinating from a theoretical point of view and essential for many applications. A compact lensless method for imaging domain patterns in ferroelectric single crystals based on a digital holographic Fizeau interferometer has been developed. This approach provides a large field-of-view image while maintaining a high spatial resolution.

Nanosecond compressive fluorescence lifetime microscopy imaging via the RATS method with a direct reconstruction of lifetime maps.

The RAndom Temporal Signals (RATS) method has proven to be a useful and versatile method for measuring photoluminescence (PL) dynamics and fluorescence lifetime imaging (FLIM). Here, we present two fundamental development steps in the method. First, we demonstrate that by using random digital laser modulation in RATS, it is possible to implement the measurement of PL dynamics with temporal resolution in units of nanoseconds.

High-precision FoM measurement setup for Ti:sapphire crystals.

The figure of merit (FoM) of Ti:sapphire (Ti:Sa) crystals is a generally used means to evaluate the quality of the crystals. Despite the importance of Ti:Sa, the question of FoM measurement precision stayed out of focus, while the commercially available spectrometers provide unsatisfactory 3 precision reaching ±60. In this paper, we present a setup for a single-pass high-precision transmission measurement for three different wavelengths (532, 780, and 1560 nm) based on Nd:YAG and Er:YAG lasers.

Beating signals in CdSe quantum dots measured by low-temperature 2D spectroscopy.

Advances in ultrafast spectroscopy can provide access to dynamics involving nontrivial quantum correlations and their evolutions. In coherent 2D spectroscopy, the oscillatory time dependence of a signal is a signature of such quantum dynamics. Here, we study such beating signals in electronic coherent 2D spectroscopy of CdSe quantum dots (CdSe QDs) at 77 K.

Versatile compressive microscope for hyperspectral transmission and fluorescence lifetime imaging.

Increasing demand for multimodal characterization and imaging of new materials entails the combination of various methods in a single microscopic setup. Hyperspectral imaging of transmission spectra or photoluminescence (PL) decay imaging count among the most used methods. Nevertheless, these methods require very different working conditions and instrumentation.

Noise effect on 2D photoluminescence decay analysis using the RATS method in a single-pixel camera configuration.

Using a random temporal signal for sample excitation (RATS method) is a new, capable approach to measuring photoluminescence (PL) dynamics. The method can be used in single-point measurement (0D), but also it can be converted to PL decay imaging (2D) using a single-pixel camera configuration. In both cases, the reconstruction of the PL decay and PL snapshot is affected by ubiquitous noise.

Targeted generation of complex temporal pulse profiles.

A targeted shaping of complex femtosecond pulse waveforms and their characterization is essential for many spectroscopic applications. A 4f pulse shaper combined with an advanced pulse characterization technique should, in the idealized case, serve this purpose for an arbitrary pulse shape. This is, however, violated in the real experiment by many imperfections and limitations.

Excited States and Their Dynamics in CdSe Quantum Dots Studied by Two-Color 2D Spectroscopy.

Quantum dots (QDs) form a promising family of nanomaterials for various applications in optoelectronics. Understanding the details of the excited-state dynamics in QDs is vital for optimizing their function. We apply two-color 2D electronic spectroscopy to investigate CdSe QDs at 77 K within a broad spectral range.

Calibration of the pixel crosstalk in spatial light modulators for 4f pulse shaping.

The targeted shaping of femtosecond pulses in 4f pulse shapers is complicated by, among other factors, the crosstalk between adjacent pixels of a spatial light modulator (SLM). Current methods for the crosstalk evaluation require setting up a different experiment, which is highly inconvenient. Here, we propose a simple procedure to extract the pixel crosstalk within the standard SLM calibration used in pulse shaping.

Charge Carrier Diffusion Dynamics in Multisized Quaternary Alkylammonium-Capped CsPbBr Perovskite Nanocrystal Solids.

CsPbBr quantum dots (QDs) are promising candidates for optoelectronic devices. The substitution of oleic acid (OA) and oleylamine (OLA) capping agents with a quaternary alkylammonium such as di-dodecyl dimethyl ammonium bromide (DDAB) has shown an increase in external quantum efficiency (EQE) from 0.19% (OA/OLA) to 13.

Influence of the delay line jitter on the SHG FROG reconstruction.

Frequency-resolved optical gating (FROG) counts among the most used methods to characterize complex femtosecond pulses. The multishot FROG experiment, studied in this work, relies on varying a delay between two replicas of the measured pulse, where the delay accuracy can suffer from delay line imperfections, setup instability, or minimization of the acquisition time. We present a detailed study on the effect of the delay line jitter on the pulse retrieval.

Collection of micromirror-modulated light in the single-pixel broadband hyperspectral microscope.

A digital micromirror device (DMD) serves in a significant part of computational optical setups as a means of encoding an image by the desired pattern. The most prominent is its usage in the so-called single-pixel camera experiment. This experiment often requires an efficient and homogeneous collection of light from a relatively large chip on a small area of an optical fiber or spectrometer slit.

Compressive imaging of transient absorption dynamics on the femtosecond timescale.

Femtosecond spectroscopy is an important tool used for tracking rapid photoinduced processes in a variety of materials. To spatially map the processes in a sample would substantially expand the method's capabilities. This is, however, difficult to achieve, due to the necessity of using low-noise detection and maintaining feasible data acquisition time.

Differential single-pixel camera enabling low-cost microscopy in near-infrared spectral region.

The optical microscope for wavelengths above 1100 nm is a very important tool for characterizing the microstructure of a broad range of samples. The availability of the technique is, however, limited because special detectors with temperature stabilization, which are costly, must be used. We present the construction of a low-cost near-infrared microscope (800-1700 nm) based on the principles of compressed sensing.

Identification and characterization of diverse coherences in the Fenna-Matthews-Olson complex.

The idea that excitonic (electronic) coherences are of fundamental importance to natural photosynthesis gained popularity when slowly dephasing quantum beats (QBs) were observed in the two-dimensional electronic spectra of the Fenna-Matthews-Olson (FMO) complex at 77 K. These were assigned to superpositions of excitonic states, a controversial interpretation, as the strong chromophore-environment interactions in the complex suggest fast dephasing. Although it has been pointed out that vibrational motion produces similar spectral signatures, a concrete assignment of these oscillatory signals to distinct physical processes is still lacking.

Lensless Photoluminescence Hyperspectral Camera Employing Random Speckle Patterns.

We propose and demonstrate a spectrally-resolved photoluminescence imaging setup based on the so-called single pixel camera - a technique of compressive sensing, which enables imaging by using a single-pixel photodetector. The method relies on encoding an image by a series of random patterns. In our approach, the image encoding was maintained via laser speckle patterns generated by an excitation laser beam scattered on a diffusor.

Drastic difference between hole and electron injection through the gradient shell of CdSeZnS quantum dots.

Ultrafast fluorescence spectroscopy was used to investigate the hole injection in CdSeZnS gradient core-shell quantum dot (CSQD) sensitized p-type NiO photocathodes. A series of CSQDs with a wide range of shell thicknesses was studied. Complementary photoelectrochemical cell measurements were carried out to confirm that the hole injection from the active core through the gradient shell to NiO takes place.

Size- and Wavelength-Dependent Two-Photon Absorption Cross-Section of CsPbBr Perovskite Quantum Dots.

All-inorganic colloidal perovskite quantum dots (QDs) based on cesium, lead, and halide have recently emerged as promising light emitting materials. CsPbBr QDs have also been demonstrated as stable two-photon-pumped lasing medium. However, the reported two photon absorption (TPA) cross sections for these QDs differ by an order of magnitude.

Photostability of the Oleic Acid-Encapsulated Water-Soluble Cd Se Zn S Gradient Core-Shell Quantum Dots.

Composite systems where quantum dots (QDs) are combined with other nanomaterials (e.g., gold nanorods) in aqueous solutions have attracted broad attention-both for their potential in applications and for studies of fundamental processes.

Two mechanisms for dissipation of excess light in monomeric and trimeric light-harvesting complexes.

Oxygenic photoautotrophs require mechanisms for rapidly matching the level of chlorophyll excited states from light harvesting with the rate of electron transport from water to carbon dioxide. These photoprotective reactions prevent formation of reactive excited states and photoinhibition. The fastest response to excess illumination is the so-called non-photochemical quenching which, in higher plants, requires the luminal pH sensor PsbS and other yet unidentified components of the photosystem II antenna.