Performed Spectroscopy Measurements Research Articles

Electric field–induced magnetochiral dichroism in a ferroaxial crystal

In a chiral medium, any mirror symmetries are broken, which induces unique physical properties represented by natural optical rotation. When electromagnetic waves propagate through a chiral medium placed in a magnetic field, the refractive index, or equivalently, the absorption encountered by the electromagnetic waves differs depending on whether it travels parallel or antiparallel to the magnetic field. Such a phenomenon is known as magnetochiral dichroism (MChD), which is the characteristic interplay between chirality and magnetism. Similar to chirality, the so-called ferroaxial order, an emergent ferroic state of crystalline materials, is also characterized by mirror symmetry breaking. In contrast to chiral materials, however, the mirror symmetry perpendicular to the crystalline principal axis is allowed in ferroaxial materials. In other words, chirality and thus phenomena unique to chirality can be induced by breaking the remaining mirror symmetry by applying an electric field. Here, we show electric control of chirality and resulting electric field-induced MChD (E-MChD) of the short-wavelength infrared region in a ferroaxial crystal, NiTiO3. We performed spectroscopy measurements of E-MChD by taking a difference of absorption coefficients obtained with and without electric and magnetic fields. As a result, E-MChD was observed around the excitation energy corresponding to Ni2+ d-d magnetic-dipole transitions. The result is nicely explained by adopting the theory of MChD concerning the pseudo-Stark splitting of the energy state. Ferroaxial materials therefore provide platforms to achieve electric control of chirality-related phenomena.

Temperature dependent activation energies of exciton states on a single GaAs laterally coupled-quantum-dot molecule and quantum dot

The objective of this study was to perform spectroscopy measurements of a single GaAs laterally coupled quantum dot molecule and quantum dot. Compared to photoluminescence spectra between a single GaAs laterally coupled quantum dot molecule and a single quantum dot, the presence of optical coupling was confirmed through dipole-dipole interactions in a single coupled quantum dot molecule. Based on temperature dependence measurements, weak exciton-phonon interactions (25 meV) were observed from the ground exciton state of a single GaAs laterally coupled quantum dot molecule in comparison with a strong exciton-phonon interaction (49 meV) from the ground exciton state of a single GaAs QD. Such weak interactions were due to reduced confinement at exciton states in a single laterally coupled quantum dot molecule. In addition, weaker activation energy (∼15 meV) was observed in terms of confined electrons in a single laterally coupled quantum dot molecule, where a confinement effect became reduced due to enlarged dimensional area in one direction along [1 1‾ 0].

Nuclear analysis of the DEMO divertor survey visible high-resolution spectrometer

Spectroscopic measurements have been recently proposed in DEMO for divertor detachment control. In its current design, the DEMO Divertor Survey Visible High-Resolution Spectrometer is foreseen to perform spectroscopy measurements by integrating three optical subsystems into an equatorial port (EP). Behind the first wall, light travels through a set of metallic mirrors and ducts before it reaches the closure plate of the EP. This paper presents a nuclear analysis performed with the Monte Carlo simulation program MCNP6 for two alternative configurations of the system. The results show that the configuration with 5 mirrors per transmission line is very effective to reduce the neutron streaming through the port. However, it will not be possible, with the current design, to introduce standard electronics along the spectroscopy ducts, as the dose rate limits for non-critical electronic components are exceeded in both configurations. In the plasma-facing mirrors, the heat loads are below 2 mW/cm3, which shows that the strategy of recessing the first mirrors and placing them behind small-diameter openings is effective to decrease the loads in the mirrors. FISPACT simulations for different materials show that material transmutation in the mirrors will be negligible throughout the DEMO reactor lifetime.

Development of a low–cost γ–ray spectrometry PMT adapter

A crucial part of any scintillator–based spectroscopy experiment is the photomultiplier tube (PMT) and its associate electronics, typically coming in the form of a PMT adapter responsible for amplifying and digitizing the record pulses. Commercial adapters are typically expensive, therefore a more practical and costless solution is in dire need. In the present work, a light–weight, portable electronic circuit was constructed from scratch based on the open–access Theremino design [1] to play the role of a PMT adapter responsible for the processing of the PMT output signal. The adapter is universally compatible with PMTs and with any computer with a built–in sound card. The PC sound card acts as the digitizer of the signal, which is subsequently analyzed by the Theremino MCA analysis software [1]. The construction of this handmade, easily reproducible circuit, increases drastically the ability to perform spectroscopy measurements with the currently available scintillators in our lab.

Laboratory-based high pressure X-ray photoelectron spectroscopy: A novel and flexible reaction cell approach.

The last 10-15 years have witnessed a resurgence in the application of high pressure X-ray photoelectron spectroscopy, mainly through the development of new electron energy analyser designs and the utilization of high-brilliance synchrotron radiation sources. To continue this expansion of the technique, it is crucial that instruments are developed for the home-laboratory, considering that this is where the vast majority of traditional ultra-high vacuum (UHV) X-ray photoelectron spectroscopy is performed. The research presented here introduces a new addition to the field, an instrument capable of performing spectroscopy measurements from UHV to high pressure (25 mbar), achieved using a retractable and modular reaction cell design. The ease of use, stability (of analyser, X-ray source, and gas delivery, etc.), and overall capability of the instrument will be demonstrated.

Functional Nanomaterials: Energy and Sensing

Sponsored by the Nanomaterials Committee, this special topic has a unique combination of short review papers and research papers on some recent advances for using functional nanomaterials for energy conversion/storage and optical/electric/magnetic signal sensing. The invited paper from Zhu’s group is an extension of their talk ‘‘One-Dimensional Nanostructures for Wearable Devices’’ presented at the TMS 2015 Annual Meeting & Exhibition (TMS2015). The paper reviews nanomaterial-enabled dry electrodes for electrophysiological sensing, particularly on electrocardiography (ECG). It starts with an overview of two different commercial electrodes (i.e., pre-gelled wet electrode and dry electrode), their electrode–skin interface models and the source of noise. The overview shows that dry electrodes have certain advantages over the wet ones, such as the elimination of signal degradation caused by dehydration of the gel. The overview also points out that (1) flexible dry electrodes are needed to form intimate contact with skin surface so that the movement of electrodes and motion artifacts can be suppressed and reduced, and (2) the nanomaterials-based electrode could be the solution. The paper then presents a comprehensive review on recent developments of dry ECG electrodes made of various nanomaterials, including metallic nanowires, metallic nanoparticles, carbon nanotubes and graphene. Their fabrication processes and performances are discussed. The paper concludes that nanomaterials-enabled dry ECG electrodes are attractive candidates for long-term ECG sensing, and calls for more studies in this field. The invited paper from Zhao’s team is a recap of their talk ‘‘Detecting Bacteria by Surface Enhanced Raman Spectroscopy’’ at TMS2015. This paper reports how surface-enhanced Raman spectroscopy (SERS) contributes to food safety by detecting the low levels of pathogenic microorganisms that may exist in foods. In particular, vegetables and fruits are vulnerable to contamination by pathogenic microorganisms since they are natural vehicles of pathogens from cultivation to delivery. Therefore, to detect a small amount of harmful microorganisms is a very important, but challenging task for food safety. Compared with traditional Raman spectroscopy, SERS exploits novel metal nanostructures to enhance the sensitivity. In this study, the authors demonstrate that the limit of detection (LOD) of Salmonella Poona from cantaloupe cubes can be as low as 100 CFU/ml in less than 4 h by performing SERS measurements on vancomycin-coated silver nanorod (VAN AgNR) substrates. It is claimed that such a small LOD has not previously been reported for label-free, intrinsic SERS detection using real food samples. This result suggests that the SERS detection technique based on AgNR is a powerful platform for a rapid, simple, and inexpensive means of pathogenic bacteria detection, which will be very useful in securing the safety of fresh foods.

The AEgIS experiment

The AEgIS experiment is presently almost completely installed at CERN. It is currently taking data with antiprotons, electrons and positrons. The apparatus is designed to form a cold, pulsed beam of antihydrogen to measure the Earth’s gravitational acceleration g on antimatter and to perform spectroscopy measurements. This paper describes the main features of the apparatus and shows a selected review of some achieved results.

Miniature multioctave light source based on a monolithic microcavity

Optical microresonators are ideal tools for the reduction of the threshold of optical parametric oscillation based on four-wave mixing. Usually, the efficiency and bandwidth of the resonant process are interdependent due to stringent phase matching requirements leading to limitation of the bandwidth of the spectrum generated for a given pump power. We demonstrate a continuous-wave low-threshold resonant optical parametric oscillator with optical spectral span ranging from 0.36 to 1.6 μm. Harmonic generation is observed when a MgF2 microresonator characterized by quality factor approaching 1010 is pumped either at 780 nm, with a standard distributed-feedback semiconductor laser, or at 698 nm, with a reflective amplifier. Pump power does not exceed 25 mW. The nonlinear process is phase matched due to χ(3)-facilitated interaction of different mode families of the resonator. The optical harmonics generated can be used to seed high-power visible lasers, generate correlated photon pairs, and perform spectroscopy measurements.

Spectroscopy and coherent manipulation of single and coupled flux qubits

Measurements of three-junction flux qubits, both single flux qubits and coupled flux qubits, using a coupled direct current superconducting quantum interference device (dc-SQUID) for readout are reported. The measurement procedure is described in detail. We performed spectroscopy measurements and coherent manipulations of the qubit states on a single flux qubit, demonstrating quantum energy levels and Rabi oscillations, with Rabi oscillation decay time TRabi = 78 ns and energy relaxation time T1 = 315 ns. We found that the value of TRabi depends strongly on the mutual inductance between the qubit and the magnetic coil. We also performed spectroscopy measurements on inductively coupled flux qubits.

Fabrication of Flux Qubit with a Mechanical Degree of Freedom

We report on the fabrication and characterization of superconducting flux qubit coupled to nanomechanical resonator vibration modes. Anisotropic and isotropic etching processes parameters of plasma created by a reactive ion etching of a CF4 gas, were optimized to suspend one arm of the qubit. One of the beams was characterized using a magnetomotive detection scheme in the transmission regime. And suspended beams with different length coupled to a superconducting flux qubits were characterized at base temperature by performing spectroscopy measurements.

AD5933-based spectrometer for electrical bioimpedance applications

To build an Electrical Bioimpedance (EBI) spectrometer using the Impedance Measurement System-On-Chip AD5933 together with a 4-Electrode Analog Front End (4E-AFE) has been proven practicable. Such small measurement devices can make possible several new applications of EBI technology, especially when combined with functional textiles, which can enable wearable applications for personal health and home monitoring. After the implementation and functional validation of the 4E-AFE-enabled spectrometer, the next natural step is to validate for which EBI applications the 4E-AFE-enabled system is suitable. To test the applicability of this novel spectrometer on several EBI applications, 2R1C equivalent models have been experimentally obtained and impedance spectroscopy measurements have been performed with the system under study and with the SFB7 EBI spectrometer manufactured by ImpediMed. The 2R1C circuit parameters have been estimated with the BioImp software from the spectra obtained with both EBI spectrometers and the estimated values have been compared with the original values used in each circuit model implementation. The obtained results indicated that the 4E-AFE-enabled system cannot beat the performance of the SFB7 in accuracy but it performs better in preciseness. In any case the overall performance indicates that the 4E-AFE-enabled system can perform spectroscopy measurements in the frequency range from 5 to 100 kHz.

Backaction Effects of a SSET Measuring a Qubit Spectroscopy and Ground State Measurement

We investigate the backaction of superconducting single-electron transistor (SSET) continuously measuring a Cooper-pair box. Due to the minimized backaction of the SSET, we observe a 2e periodic Coulomb staircase according to the two-level system Hamiltonian of the Cooper-pair box. We demonstrate that we can control the quantum broadening of the ground state in-situ. We perform spectroscopy measurements and demonstrate that we have full control over the Cooper-pair box Hamiltonian. The ability to reduce the backaction is a necessary condition to use the SSET as a quantum state readout for the CPB as a qubit.

Spectroscopy on Two Coupled Superconducting Flux Qubits

We have performed spectroscopy measurements on two coupled flux qubits. The qubits are coupled inductively, which results in a sigma(z)(1)sigma(z)(2) interaction. By applying microwave radiation, we observe resonances due to transitions from the ground state to the first two excited states. From the position of these resonances as a function of the applied magnetic field, we observe the coupling of the qubits. The coupling strength agrees with calculations of the mutual inductance.

Free evolution of superposition states in a single Cooper pair box

We have fabricated a single Cooper-pair box (SCB) in close proximity to a single electron transistor (SET) operated in the radio-frequency mode (RF-SET) with an inductor and capacitor lithographed directly on chip. The RF-SET was used to measure the charge state of the SCB revealing a $2e$ periodic charge quantization. We performed spectroscopy measurements to extract the charging energy ${(E}_{C})$ and the Josephson coupling energy ${(E}_{J}).$ Control of the temporal evolution of the quantum charge state was achieved by applying fast dc pulses to the SCB gate. The dephasing and relaxation times were extracted from these measurements.