Researchers have implemented an ultrafast pump probe spectroscopy setup for stimulated Raman spectroscopy that allows them to correlate energy transfer with vibrations and structural changes.
Experiments like this enhance the understanding of complex biological process, for example this approach will be useful for further developing artificial photosynthesis. The pump probe experiments often use sensitive, high resolution spectroscopy systems that can acquire spectral data at kHz rates.
Researchers from the Netherlands and Rochester (USA) performed measurements of photophysical properties of intrinsic emission centers in boron silicate or quartz glass. Their fluorescence emission shows single photon emission with similar properties as quantum dots or other molecular single photon emitters in the visible.
Different kinds of glasses are often used as substrate to study fluorescence of single photon sources like quantum dots. In particular, for materials that don’t produce strong emission profiles understanding the origin of background radiation is important and the intrinsic emission from the substrates found here could even have been mistaken for the design emitters in previous experiments.
Various techniques are applied to fully characterize the emission properties. Sensitive fluorescence emission spectroscopy is important for quantitative detection of the emission signal from single molecule sources.
Two dimensional materials are heavily researched and useful devices can be built by stacking and combining multiple layers of these materials together.
These measurements require nm precise positioning and resolution ability. The team uses a cryogenic confocal microscope to achieve the required position and light emission is captured in an optical fiber going into a spectrograph for analysis.
This article describes design and observation results of the SEDM spectrograph. The instrument was designed for automated classification of transient astronomical events like supernovae. It has been in operation at the Palomar 60- inch telescope and uses 2 large area PIXIS cameras for photometric and spectroscopic detection.
Zinc oxide is a large bandgap semiconductor that is being studied for uses in nanostructures and thin film optoelectronic devices.
The properties of thin zinc oxide films are sensitive to its different forms of its crystal structure. The properties of the thin films produced by magnetron sputtering can be anlayzed with X-ray, electrical and optical methods such as PL spectroscopy. The PL spectrum shows distinct changes depending on the zinc oxide polarity.
Atmospheric pollution is an area of great concern in all densely populated areas around the world.
The concentration of pollutants can be measured with spectroscopy using differential optical absorption of scattered sunlight in the atmosphere. Researchers from China use this technique (multi-axis differential optical absorption spectroscopy) to monitor and characterize the concentration of several molecule species.
While renewable energy production from photovoltaics is rising, researchers are constantly looking for new materials and improved ways to lower cost and increase efficiency of solar cells. Perovskites have large potential and are heavily investigated, especially to further increase efficiency and lifetime as perovskite devices still degrade quickly when exposed to typical environments.
A team of researchers around Tom Gregorkiewicz from University of Amsterdam published an article discussing their research on all inorganic perovskite nanocrystals. According to the researchers this material shows advanced stability and optical properties compared to typically studied organic perovskites. In general, the team from Amsterdam is trying to use nanotechnology to improve the efficiency of photovoltaic devices. Here they observe for the first-time carrier multiplication in a perovskite nanomaterial.
Carrier multiplication is particularly strong in nanoscale materials and increases the conversion efficiency of photons into charge carriers. When the photon energy is larger than the bandgap energy, the excess energy is used to create additional charge carriers instead of being lost to thermal energy in the material. The researchers use optical spectroscopy to determine the spectral signature and efficiency of the multiplication effect such as photoluminescence excitation, and time resolved PL.
Transient absorption measurements using a pump probe laser scheme reveal the main signature of the carrier multiplication effect. This technique can resolve time scales into down to the picosecond range. In transient measurements CCDs and spectrographs are synchronized to ultrafast laser pulses typically with 100Hz – 1kHz repetition rates (here one of their setups uses a PIXIS camera on a SP-2500 spectrograph). The high time resolution is achieved with a delay stage that increases the relative path travelled between the pump and probe pulses before reaching the sample.
The researchers observe an increase in the absorbance amplitude as well as an additional fast decaying (on the picosecond scale) component of the transient signal that reveal carrier multiplication. In the future devices using perovskites and nanotechnology in this way could further increases the breath-taking speed in which the efficiency of perovskite-based photovoltaics increases.
Due to its ability to identify different materials even over large distances Raman spectroscopy is a valuable tool in planetary science, for example used on Mars Rover missions.
Researchers from the University of Hawaii report on new methods for analysis of data from an interferometric Raman spectrometer that is used for stand-off detection of Raman signals. The two-dimensional interference pattern is collected with an ICCD as it allows detection of signals in daylight by adjusting the gate to collect Raman signal produced by a pulsed laser. Fourier transform of the interference pattern reveals the Raman spectrum.
Researchers from Germany are optimizing a thin film deposition technique that uses Plasmas by using high speed imaging.
The technique called HiPIMS requires precise control of the quality of the plasma in the coating chamber. Specifically, the group uses an ICCD with ns gate width to image regions of very pronounced ionization called spokes. They find that by monitoring the pattern of spokes the deposition process can be optimized.
Raman scattering of burning jets can be used for local temperature and molecular concentration measurements.
An ICCD with short gate time is used to acquire the Raman signal against the dark flame background. Researchers around Vladimir Dulin from Russia use wide field filters to acquire Raman images of burning jets.
