PR21_Integrated_Photonic_Spectrometer_STTR_16

The goal of this project was to design silicon photonic components for a microchip-scale spectrometer. Future earth science and space missions may benefit from spectroscopic measurements made using compact, energy efficient and inexpensive instruments.

Exploring the Retinal Binding Cavity of Archaerhodopsin-3 by Replacing the Retinal Chromophore With a Dimethyl Phenylated Derivative

Rhodopsins act as photoreceptors with their chromophore retinal (vitamin-A aldehyde) and they regulate light-dependent biological functions. Archaerhodopsin-3 (AR3) is an outward proton pump that has been widely utilized as a tool for optogenetics, a method for controlling cellular activity by light. To characterize the retinal binding cavity of AR3, we synthesized a dimethyl phenylated retinal derivative, (2E,4E,6E,8E)-9-(2,6-Dimethylphenyl)-3,7-dimethylnona-2,4,6,8-tetraenal (DMP-retinal). QM/MM calculations suggested that DMP-retinal can be incorporated into the opsin of AR3 (archaeopsin-3, AO3). Thus, we introduced DMP-retinal into AO3 to obtain the non-natural holoprotein (AO3-DMP) and compared some molecular properties with those of AO3 with the natural A1-retinal (AO3-A1) or AR3. Light-induced pH change measurements revealed that AO3-DMP maintained slow outward proton pumping. Noteworthy, AO3-DMP had several significant changes in its molecular properties compared with AO3-A1 as follows; 1) spectroscopic measurements revealed that the absorption maximum was shifted from 556 to 508 nm and QM/MM calculations showed that the blue-shift was due to the significant increase in the HOMO-LUMO energy gap of the chromophore with the contribution of some residues around the chromophore, 2) time-resolved spectroscopic measurements revealed the photocycling rate was significantly decreased, and 3) kinetical spectroscopic measurements revealed the sensitivity of the chromophore binding Schiff base to attack by hydroxylamine was significantly increased. The QM/MM calculations show that a cavity space is present at the aromatic ring moiety in the AO3-DMP structure whereas it is absent at the corresponding β-ionone ring moiety in the AO3-A1 structure. We discuss these alterations of the difference in interaction between the natural A1-retinal and the DMP-retinal with binding cavity residues.

Simple device for spectroscopy laboratory exercises

Undergraduate physics laboratory exercises are very important in shaping students’ attitude to science, especially for future teachers. Recently, it is necessary to look for ways to easily create large quantities of experimental sets, not only for institutional use, but also for sets that can be produced in large quantities and distributed for use in distance learning. In this paper, we briefly describe the various ways to support the teaching of wave optics, and then describe one of the possible methods for performing undergraduate spectroscopic measurements using a 3D printed spectroscope and light source.

Up-Conversion Luminescence Processes in NaLaF4 Doped with Tm3+ and Yb3+ and Dependence on Tm3+ Concentration and Temperature

In this work, luminescence processes in polycrystalline NaLaF4:Tm3+ and NaLaF4:Tm3+,Yb3+ materials were studied. Luminescence spectra and decay kinetics measurements were performed for NaLaF4 doped with various Tm3+ concentrations (0.01, 0.1, 0.5, 1, and 2 mol%) under direct excitation to 3P0, 1D2, 1G4, and 3H4 states. It was found that some of the Tm3+ excited states are more affected by Tm3+ concentration than other states. Under infrared excitation of Yb3+, energy transfer to Tm3+ occurred and intensive ultraviolet and blue up-conversion luminescence was observed. Possible up-conversion mechanisms are discussed. Spectroscopic measurements show that long-duration excitation radiation reduces ultraviolet up-conversion luminescence intensity, and this intensity reduction is related to sample heating due to high excitation radiation density and a poor heat sink from samples. It was found that sample configuration for spectroscopic measurements is crucial to correctly describe measured up-conversion luminescence spectra.

Current status and prospects of muonium spectroscopy at PSI

Recent and ongoing developments of low energy muon beamlines are heralding a new era of precision Muonium spectroscopy. While past spectroscopic measurements of Muonium were performed at pulsed muon facilities and were statistically limited, the advent of continuous low energy muon beams, such as at the LEM beamline at PSI, paired with the development of efficient muon-muonium converters and laser advancements, will overcome these limitations. Current experiments presently underway at the LEM facility and in the near future at the muCool beamline, which is under development at PSI, aim to improve the precision of both the 1S-2S transition determination and Lamb shift by several orders of magnitude. In this Chapter we give an overview of the current status and future prospects of these activities at PSI, highlighting how their projected significance fits into a broader context of other ongoing efforts worldwide.