Erratum: Nonlinear dynamics of a self-mixing thin-slice solid-state laser subjected to Doppler-shifted optical feedback [Phys. Rev. E 104, 044203 (2021)].

This corrects the article DOI: 10.1103/PhysRevE.104.044203.

Nonlinear dynamics of a self-mixing thin-slice solid-state laser subjected to Doppler-shifted optical feedback.

Chaotic oscillations of a linearly polarized single longitudinal-mode thin-slice Nd:GdVO_{4} laser placed in a self-mixing laser Doppler velocity scheme were dynamically characterized in terms of the intensity probability distribution, joint time-frequency analysis, and short-term Fourier transformation of temporal evolutions, and the degree of disorder in the amplitude and phase of the long-term temporal evolutions. The transition from chaotic relaxation oscillations (ROs) to chaotic spiking oscillations (SOs) was explored via the chaotic itinerancy (CI) regime by increasing the feedback ratio toward the laser from a rotating scattering object. The intensity probability distribution was found to change from an exponential decay in the RO regime to an inverse power law in the SO regime, which manifests itself in self-organized critical behavior, while stochastic subharmonic frequency locking among the two periodicities of RO and SO takes place in the CI regime featuring quantum-noise (spontaneous-emission)-induced order in the amplitude and phase of the spiking oscillations. All of the experimental results were reproduced by numerical simulations of a model equation of a single-mode self-mixing solid-state laser subjected to Doppler-shifted optical feedback from a rotating scattering object.

Erratum: Nonlinear dynamics of a self-mixing thin-slice solid-state laser subjected to Doppler-shifted optical feedback [Phys. Rev. E 104, 044203 (2021)].

This corrects the article DOI: 10.1103/PhysRevE.104.044203.

Evaluation of resonance phenomena of mechanical oscillator by self-mixing solid-state laser Doppler vibrometry.

We performed self-mixing laser Doppler vibrometry on a vibrating oscillator consisting of a rigid-body laser-light-scattering object attached to a piezoelectric element driven by low-frequency AC voltage to evaluate its motion. The sideband spectrum reflecting the motion of the oscillator is observed in the power spectrum of the modulated wave. The time dependence of the intensity of the sideband spectrum is explained by Newton's second law assuming that the oscillator has a mechanical resonance frequency and undergoes simple vibration under the driving force, which depends on the deformation velocity of the piezoelectric element. Our results indicate that the motion of a slowly moving target with sub-nanometer displacement, which is difficult to measure by general laser Doppler vibrometry, can be evaluated with high spatial and frequency resolutions by detecting the sideband signal, which changes periodically at the driving frequency of the piezoelectric element.

Detection and counting of a submicrometer particle in liquid flow by self-mixing microchip Yb:YAG laser velocimetry.

We observed intermittent modulation by scattered light from a single submicrometer particle moving in the flow channel using a self-mixing microchip Yb:YAG laser Doppler velocimeter (LDV) under lateral beam access. The Doppler-shift frequency chirping (i.e., velocity change) was identified in accordance with a particle passage through the beam focus. Single particle counting, which obeys the Poisson distribution, was performed successfully over a long period of time. The experimental results have been reproduced by a numerical simulation. The LDV signal was increased over 20 dB for a 202-nm particle without chirping by collinear beam access with the laser beam axis aligned along the flow direction.

Johari-Goldstein process of solute in high-water-content aqueous solutions.

For low-water-content aqueous solutions, the primary α process due to the cooperative motion of solute and water molecules and the secondary Johari-Goldstein (JG) process of solute are observed. For high-water-content aqueous solutions, the α process due to the cooperative motion of solute and water molecules and the secondary ß process due to the motion of excess water are observed. However, the JG process of solute has not been observed. To clarify this difference, we measured the dielectric spectra of supercooled triethyleneglycol-water mixtures in a wide temperature range. We discuss the effect of excess water on the molecular dynamics relating to the JG process of solute in high-water-content aqueous solutions.

Analysis of flow within a left ventricle model fully assisted with continuous flow through the aortic valve.

Blood compatibility of a ventricular assist device (VAD) depends on the dynamics of blood flow. The focus in most previous studies was on blood flow in the VAD. However, the tip shape and position of the VAD inflow cannula influence the dynamics of intraventricular blood flow and thus thrombus formation in the ventricle. In this study, blood flow in the left ventricle (LV) under support with a catheter-type continuous flow blood pump was investigated. The flow field was analyzed both numerically and experimentally to investigate the effects of catheter tip shape and its insertion depth on intraventricular flow patterns. A computational model of the LV cavity with a simplified shape was constructed using computer-aided design software. Models of catheters with three different tip shapes were constructed and each was integrated to the LV model. In addition, three variations of insertion depth were prepared for all models. The fully supported intraventricular flow field was calculated by computational fluid dynamics (CFD). A transparent LV model made of silicone was also fabricated to analyze the intraventricular flow field by the particle image velocimetry technique. A mock circulation loop was constructed and water containing tracer particles was circulated in the loop. The motion of particles in the LV model was recorded with a digital high-speed video camera and analyzed to reveal the flow field. The results of numerical and experimental analyses indicated the formation of two large vortices in the bisector plane of the mitral and aortic valve planes. The shape and positioning of the catheter tip affected the flow distribution in the LV, and some of these combinations elongated the upper vortex toward the ventricular apex. Assessment based on average wall shear stress on the LV wall indicated that the flow distribution improved the washout effect. The flow patterns obtained from flow visualization coincided with those calculated by CFD analysis. Through these comparisons, the numerical analysis was validated. In conclusion, results of these numerical and experimental analyses of flow field in the LV cavity provide useful information when designing catheter-type VADs.

Analysis of molecular dynamics of colloidal particles in transported dilute samples by self-mixing laser Doppler velocimetry.

Colloidal particles in a liquid medium are transported with constant velocity, and dynamic light scattering experiments are performed on the samples by self-mixing laser Doppler velocimetry. The power spectrum of the modulated wave induced by the motion of the colloidal particles cannot be described by the well-known formula for flowing Brownian motion systems, i.e., a combination of Doppler shift, diffusion, and translation. Rather, the power spectrum was found to be described by the q-Gaussian distribution function. The molecular mechanism resulting in this anomalous line shape of the power spectrum is attributed to the anomalous molecular dynamics of colloidal particles in transported dilute samples, which satisfy a nonlinear Langevin equation.

Molecular dynamics of poly(N-isopropylacrylamide) in protic and aprotic solvents studied by dielectric relaxation spectroscopy.

We report the experimental results of dielectric relaxation spectroscopy for the systems of poly(N-isopropylacrylamide) [PNiPAM] in various solvents in the frequency range of 40 kHz to 20 GHz at the solution temperature of 25.0 °C. The solvents used in this study were protic solvents (water, methanol, ethanol, and 1-propanol) and aprotic solvents (acetone, methyl ethyl ketone, and dimethyl sulfoxide). Two relaxation processes were observed at frequencies of approximately 1 MHz and 10 GHz in all the solutions. The origins of the two relaxation processes are considered to be the reorientation of dipoles of the PNiPAM chains at middle frequencies (m-process) and that of solvent molecules at higher frequencies (h-process). For the PNiPAM solutions composed of protic solvents except for 1-propanol, the relaxation time of the h-process increased with increasing PNiPAM concentration, whereas that of the h-process for the 1-propanol decreased with increasing PNiPAM concentration. In contrast, the relaxation times of the h-process for the aprotic solvents were independent of the density of hydrogen-bonding sites. For the m-process, which is attributed to the local chain motion of PNiPAM, the extrapolated relaxation time to zero polymer concentration τ(m0) was scaled by the solvent viscosity for all the protic solvents, whereas for the aprotic solvents τ(m0) showed no correlation with the solvent viscosity. The dynamics of polymer chains and solvent molecules in their solution state are clarified in terms of cooperative motion, which is associated with the interactions through hydrogen bonding at the molecular level.

Dielectric properties of the free water in hydroxypropyl cellulose.

We performed dielectric measurements of aqueous solutions of hydroxypropyl cellulose (HPC) with various concentrations in the temperature range between 25 °C and -20 °C. A primary relaxation process due to the motion of free water restricted by HPC molecules is observed at GHz region. The relaxation time and shape parameter of the primary process strongly depend on the concentration of HPC. The change of the dielectric relaxation parameters is interpreted by the results of the formation of a cholesteric phase structure of the HPC molecules.

Dynamics of polymer and glass transition in partially crystallized polymer solution studied by dielectric spectroscopy.

The local chain motion of poly(vinyl acetate) (PVAc) in 20 wt% PVAc benzene solution was observed by broadband dielectric spectroscopy in the frequency range of 10 µHz-10 GHz at various temperatures between -20 and +40°C from the partially crystallized state, which is composed of a crystallized benzene phase and non-crystallized PVAc/benzene solution phase, below the melting temperature, T(m), of benzene to the liquid state above T(m). The relaxation time of the local chain motion of PVAc shows extremely strong temperature dependence below T(m). This chain motion of PVAc is the origin of the glass transition observed by differential scanning calorimetry for the partially crystallized state of the PVAc/benzene mixture below T(m).

Structural behavior of alcohol-1,4-dioxane mixtures through dielectric properties using TDR.

The values of complex permittivity for alcohol-1,4-dioxane (DX) mixtures with various concentrations have been determined in the frequency range 10 MHz to 20 GHz using the time domain reflectometry (TDR) method. Numbers of hydrogen bonds between alcohol-alcohol and alcohol-dioxane pairs are estimated from the values of the static dielectric constant by using the Luzar model. The model provides a satisfactory explanation of the experimental results related to the static dielectric constant. The binding energies for alcohol-alcohol (pair 11) and alcohol-DX (pair 12) are estimated to be -13.98 and -16.25 kJ/mol, respectively. The results have also been compared with previous results of the ethyleneglycol-DX system.

Determination of velocity of self-mobile phytoplankton using a self-mixing thin-slice solid-state laser.

We present an analysis of the shoulder-shaped power spectrum observed in the modulated laser output due to feedback light scattered from dynamic changes in self-mobile phytoplankton with flagella in seawater performed using a self-mixing laser Doppler vibrometry system. The power spectrum occasionally has shoulder-shaped broad frequency components superimposed on a Lorentz-type spectrum. This reflects the translational motion of phytoplankton moving across the beam-focus area. The velocity of phytoplankton in the focus area can be obtained by applying a curve fitting procedure to the power spectrum. Moreover, the average velocity and the velocity distribution of phytoplankton can be determined from curve fitting of the long-term power spectrum.

Universality of separation behavior of relaxation processes in supercooled aqueous solutions as revealed by broadband dielectric measurements.

We investigate the universality of the relaxation processes for high-water-content aqueous solutions in a supercooled and glassy state, to clarify the molecular dynamics of water in aqueous solutions. The appearance of the additional process at the crossover temperature is due to structured water arising, and it is a universal feature of aqueous solutions. The normalized relaxation strength of the beta process plotted against reciprocal temperature obeys -3 power law that is due the arrangement region of the water molecules through the tetrahedral hydrogen bond structure.

Three-channel three-dimensional self-mixing thin-slice solid-state laser-Doppler measurements.

We report successful real-time three-channel self-mixing laser-Doppler measurements with extreme optical sensitivity using a laser-diode-pumped thin-slice Nd:GdVO(4) laser in the carrier-frequency-division-multiplexing scheme with three pairs of acoustic optical modulators (i.e., frequency shifters) and a three-channel FM-wave demodulation circuit. We demonstrate (1) simultaneous independent measurement of three different nanometer-vibrating targets, (2) simultaneous measurements of small particles in Brownian motion from three directions, and (3) identification of the velocity vector of small particles moving in water flowing in a small-diameter glass pipe.

Broadband dielectric study on the water-concentration dependence of the primary and secondary processes for triethyleneglycol-water mixtures.

Broadband dielectric measurements for triethyleneglycol (3EG)-water mixtures with various concentrations were performed in the frequency range of 10 muHz-10 GHz and in the temperature range of 130-298 K . For each mixture, the separation of the primary (alpha) and secondary processes is observed below the crossover temperature, TC. In the case of 80-100 wt% 3EG-water mixtures, the Kohlrausch-Williams-Watts-type primary process above TC continues to the alpha process below TC, and an additional secondary process is observed in the frequency range higher than that of the alpha process below TC. On the other hand, the primary process for 65 and 70 wt% 3EG-water mixtures above TC continues to the higher-frequency secondary process below TC, and an additional alpha process appears at a frequency lower than that of the secondary process. The contribution of water to relaxation processes is discussed, to clarify the molecular mechanism of the separation behavior. The characteristic separation behavior of the relaxation processes for high-water-content 3EG-water mixtures is due to the existence of excess water, which cannot move cooperatively with solute 3EG molecules below TC.

Dielectric properties of ethyleneglycol-1,4-dioxane mixtures using TDR method.

Complex permittivity has been determined for mixtures of ethyleneglycol-1,4-dioxane (EG-DX) with various concentrations in the frequency range from 100 MHz to 30 GHz at 25 degrees C by time domain reflectometry (TDR). A primary process with an asymmetric shape and a Debye-type small-amplitude high-frequency process are observed for each mixture. The deviation of the relaxation time for the primary process from that of the ideal mixture shows a maximum value at a mole fraction of 1,4-dioxane, xDX approximately =0.8. The static permittivity for the mixtures can be explained using the Luzar model by assuming the formation of two types of hydrogen-bonded dimers, one between EG-EG (pair 1) and the other between EG-DX (pair 2). The number of these pairs is also estimated as a function of concentration. These results of the relaxation time and static permittivity are interpreted on the basis of a model of two kinds of cooperative domains coexisting in the mixtures.

Two-channel self-mixing laser Doppler measurement with carrier-frequency-division multiplexing.

We demonstrate real-time two-channel self-mixing laser-Doppler measurement with extreme optical sensitivity using a laser-diode-pumped thin-slice LiNdP4O12 laser. Successful carrier-frequency-division-multiplexed two-channel operations are realized by using one laser, two sets of optical frequency shifters, and a two-channel frequency-modulated-wave demodulation circuit. Simultaneous independent measurements of vibrations of speakers and averaged motions of small Brownian particles in different scattering cells are demonstrated. Self-mixing photon correlation spectroscopy of particle size distributions is also discussed.

Dielectric study of the alpha and beta processes in supercooled ethylene glycol oligomer-water mixtures.

Broadband dielectric measurements for 65 wt % ethylene glycol oligomer (EGO)-water mixtures with one to six repeat units of EGO molecules were performed in the frequency range of 10 microHz-10 GHz and the temperature range of 128-298 K. In the case of the water-EGO mixtures with one and two repeat units of the EGO molecule (small EGO), the shape of the dielectric loss peak of the primary process is asymmetrical about the logarithm of the frequency of maximum loss above the crossover temperature, T(C). The asymmetric process continues to the alpha process at a low frequency, and an additional beta process appears in the frequency range higher than that of the alpha process below T(C). In contrast, the water-EGO mixtures with three or more repeat units of the EGO molecule (large EGO) show a broad and symmetrical loss peak of the primary process above T(C). The symmetric process continues to the beta process, and an additional alpha process appears in the frequency range lower than that of the beta process below T(C). These different scenarios of the alpha-beta separation related to the shape of the loss peak above T(C) are a result of the difference in the cooperative motion of water and solute molecules. The solute and water molecules move cooperatively in the small EGO-water mixtures above T(C), and this cooperative motion leads to the asymmetric loss peak above T(C) and the alpha process below T(C). For the large EGO-water mixtures, the spatially restricted motion of water confined by solute molecules leads to the symmetric loss peak above T(C) and the beta process below T(C).