Mirror Velocity Research Articles

On the electromagnetic wave interaction with subluminal, luminal, and superluminal mirrors

As predicted by A. Einstein [Ann. Phys. (Leipzig) 17, 891 (1905)], the electromagnetic wave reflected at a moving mirror is frequency-upshifted and intensified as high as the mirror velocity is close to the speed of light in vacuum. However, at this limit the mirror reflectivity vanishes, because the higher the wave frequency the more transparent matter is. To resolve this paradox, we analyse the electromagnetic wave propagation in medium where the refractive index modulation moves at the speed of light in vacuum. Although the luminal and superluminal modulations are unconditionally transparent for the incident radiation, they both can reflect. We find the new type of the electromagnetic wave reflection with the increasing in time frequency inside the luminal mirror. If the modulation disappears the high frequency radiation is released as a short wavepacket.

Electromagnetic Doppler effect in non-reciprocal medium

Reflected light from a moving object, such as a mirror, is frequency-shifted via the Doppler effect. This well-known phenomenon is used to determine the speed and direction of an object due to the red or blue shifting of the received electromagnetic radiation frequency. To date, the Doppler theory has focused on the propagation of electromagnetic radiation through reciprocal media where the transiting photons have the same speed, regardless of direction. However, optical birefringence exists in solid-state, liquid, and gas media, which results in spatially dependent, and vector field-dependent, propagation velocities. When combined with the Faraday effect, which is employed routinely in laboratory setups and present at galactic scales, non-reciprocal Doppler effects may occur. A non-reciprocal Doppler effect theory is derived showing frequency shift dependencies on the object velocity and the directional speed of light in the medium. This general Doppler theory is shown to simplify the canonical relations for the Doppler effect in systems without a directional dependence on light. In non-reciprocal systems, when the mirror velocity is much less than the speed of light, the general frequency shift relation simplifies to a dependency on the roundtrip average speed of light. This theory provides a basis for the application of the Doppler effect to estimate the velocity of moving objects in non-reciprocal systems.

Aerodynamic Analysis on Noise Generated from Automotive Side Mirror Using CFD

The geometry of the car's side mirror influences the aerodynamic noise. This study will use computational fluid dynamics (CFD) to investigate the effect of aerodynamic analysis on noise from the side mirror. In this study, we will design two types of side mirrors using the Honda Civic EG9 for sedans and the Range Rover Evoque for SUVs. SolidWorks software was used for geometry modelling and the analysis was completed using the ANSYS software. Three streamline velocity values (80 km/h,100km/h, 120 km/h) were chosen as references. The results of the analysis included the side mirror's drag force, acoustic contour, and velocity streamlines. Design 1, produces a maximum acoustic power level of 77.21 dB when travelling at a high speed of 120 km/h. The maximum acoustic power level for Design 2, which travels at 120 km/h is 75.71dB. In summary, Design 2's side mirror has a higher acoustic power level than Design 1's side mirror. Design 1 produces a drag force of 4.52 N at a high speed of 120 km/h while Design 2 results in a drag force of 6.36 N at a high speed of 120 km/h.

Direct Absorption and Photoacoustic Spectroscopy for Gas Sensing and Analysis: A Critical Review

AbstractOptical spectroscopy has a broad scientific basis in chemistry, physics, and material science, with diverse applications in medicine, pharmaceuticals, agriculture, and environmental monitoring. Fourier transform infrared (FTIR) spectrometers and tunable laser spectrometers (TLS) are key devices for measuring optical spectra. Superior performance in terms of sensitivity, selectivity, accuracy, and resolution is required for applications in gas sensing. This review deals with gas measurement based on either direct optical absorption spectroscopy or photoacoustic spectroscopy. Both approaches are applicable to FTIR spectroscopy or TLS. In photoacoustic spectroscopy, cantilever‐based photoacoustic spectroscopy is focused due its high performance. A literature survey is conducted revealing the recent technological advances. Theoretical fundamental detection limits are derived for TLS and FTIR, considering both direct absorption and photoacoustic spectroscopies. A theoretical comparison reveals which technology performs better. The minimum normalized absorption coefficient and normalized noise equivalent absorption coefficient appear as key parameters for this comparison. For TLS‐based systems, direct absorption spectroscopy is found to be the best for lower laser power and longer path length. For FTIR‐based systems, direct absorption is found to be the best for low temperature sources, higher spectrometer throughput, faster mirror velocity, and longer gas cells.

Modified weak-value-amplification technique for measuring a mirror's velocity based on the Vernier effect

A modified weak-value-amplification (MWVA) technique to measure a mirror's velocity based on the Vernier effect is proposed. To demonstrate its enhanced sensitivity and higher signal-to-noise ratio (SNR), we use two cascaded Michelson interferometers with similar optical structures. One has a fixed mirror and acts as a fixed part of the Vernier scale, while the other, with a moving mirror, acts as a sliding part of the Vernier scale for velocity sensing. The envelope of the cascaded interferometers shifts much more than a single one with a certain enhancement factor, which is related to the free space range difference between them. In addition, we calculate the SNR based on the Fisher information with both the MWVA and traditional weak-value-amplification (TWVA) techniques. The results show that both the SNR and the sensitivity with our MWVA technique is greater than that of the TWVA technique within the range of our time measurement window. In particular, MWVA can present a viable and effective alternative to the TWVA technique out of the limit of resolution. Furthermore, by using the principles of the Vernier effect, it is applicable and convenient to improve the sensitivity and SNR in measuring other quantities with the TWVA technique.

Relativistic bands in the discrete spectrum of created particles in an oscillating cavity

We investigate the dynamical Casimir effect for a one-dimensional resonant cavity, with one oscillating mirror. Specifically, we study the discrete spectrum of created particles in a region of frequencies above the oscillation frequency $\omega_0$ of the mirror. We focus our investigation on an oscillation time equal to $2L_0/c$, where $L_0$ is the initial and final length of the cavity, and $c$ is the speed of light. For this oscillation duration, a field mode, after perturbed by the moving mirror, never meets this mirror in motion again, which allows us to exclude this effect of re-interaction on the particle creation process. Then, we describe the evolution of the particle creation with frequencies above $\omega_0$ only as a function of the relativistic aspect of the mirror's velocity. In other words, we analyze the formation of relativistic bands in a discrete spectrum of created particles.

Responses of Leaf Cuticles to Rice Blast: Detection and Identification Using Depth-Profiling Fourier Transform Mid-Infrared Photoacoustic Spectroscopy.

Cuticle is the first barrier for rice to resist blast fungus on the surface of the leaf. Studies on how the rice leaf cuticle responds to rice blast and attempts to perform early detection of rice blast are limited, and these two issues were explored in this study via depth-profiling Fourier transform infrared photoacoustic spectroscopy (FTIR-PAS). Rice leaves with four different scales of injury (healthy leaves as CK, asymptomatic leaves from mildly diseased seedlings as S1, infected leaves with fewer than five lesions as S2, and infected leaves with more than 10 lesions as S3) were scanned by three moving mirror velocities 0.32, 0.47, and 0.63 cm/s for the depth profiling of the rice leaf surface. The response patterns were acquired via chemometrics to analyze the variations of the chemical group absorptions in the different layers of a sample and in the same layer between different samples. Results showed that the leaf cuticle tended to be thicker and the relative content of fatty alcohols and cutin, unsaturated compounds, and aromatics in the cuticle increased when rice seedlings were infected by blast fungus. Together with the principal component analysis, the probabilistic neural network was applied to identify the samples in early stages (CK and S1), which reached an accuracy of 90% for the samples in the greenhouse and 82% for the samples in the field. Thus, depth-profiling FTIR-PAS was good at analyzing the variation in cuticle layers and showed great potential in the early detection of rice blast or other diseases in different species.

Emission of photon pairs by mechanical stimulation of the squeezed vacuum

To observe the dynamical Casimir effect (DCE) induced by a moving mirror is a long-standing challenge because the mirror velocity needs to approach the speed of light. Here, we present an experimentally feasible method for observing this mechanical DCE in an optomechanical system. It employs a detuned, parametric driving to squeeze a cavity mode, so that the mechanical mode, with a typical resonance frequency, can parametrically and resonantly couple to the squeezed cavity mode, thus leading to a resonantly amplified DCE in the squeezed frame. The DCE process can be interpreted as {\it mechanically-induced two-photon hyper-Raman scattering} in the laboratory frame. Specifically, {\it a photon pair} of the parametric driving absorbs a single phonon and then is scattered into an anti-Stokes sideband. We also find that the squeezing, which additionally induces and amplifies the DCE, can be extremely small. Our method requires neither an ultra-high mechanical-oscillation frequency (i.e., a mirror moving at nearly the speed of light) nor an ultrastrong single-photon optomechanical coupling and, thus, could be implemented in a wide range of physical systems.

In situ detection of rice leaf cuticle responses to nitrogen supplies by depth-profiling Fourier transform photoacoustic spectroscopy

Plant cuticle is an important interface on the outmost region of plant and will make the response to environmental changes. However, research about how the variable nutritional status affect plant cuticle is limited. This was the first report about the manners of rice leaf cuticle in answer to different nutritional circumstances of nitrogen detected by the Fourier transform infrared photoacoustic spectroscopy (FTIR-PAS) which with a main superiority for in situ and depth-profiling in mid-infrared range. Rice leaves from the seedlings treated with three nitrogen levels designed as low (22N1), medium (N2) and high (N3) concentration were scanned by three moving mirror velocities (0.32 cm s-1, 0.47 cm s-1, and 0.63 cm s-1) at 900-4000 cm-1 to acquire the spectra of leaf surfaces. Well-resolved peaks had been detected at 3400, 2800, 1650, 1520 and 1050 cm-1. Combining with the structures and compositions of cuticle, the spectra recorded with 0.63 cm s-1 were identified to be from cuticle, and were used to analyze the responses of cuticle. Through curve-fitting, the absorption ratio of the peaks at (cm-1) 1050/3400, 1050/2800 and 1650/2800 shown regular changes，which were suggested to corresponded with ν(CO)/ν(OH), ν(CO)/ν(CH) and ν(C=C)/ν(CH) mainly. These ratios were supported to reflect the amount or variation of cuticle components, such as cutin, fatty alcohols, acids and unsaturated compounds. It provided insights about how nitrogen affected cuticles and showed great potentials to utilized FTIR-PAS for detecting cuticle variations.

Comparison of photoacoustic and attenuated total reflectance for the qualitative analysis of a bituminous Colombian coal by Fourier transform infrared spectroscopy

A Colombian coal from La Loma, Cesar, Colombia, field was characterized by Fourier transform infrared photoacoustic spectroscopy. Spectral analysis was focused on the mid-infrared, where previous publications have shown remarkable changes in the coal structure. Instrumental parameters of the infrared spectrometer were investigated for optimal spectra acquisition. Optimal parameters are a mirror velocity of 0.16 cm/s, a number of scans of 512, and a resolution of 2 cm−1. Results of Fourier transform infrared photoacoustic spectroscopy were compared with Fourier transform infrared attenuated total reflectance for validation. Both techniques can be implemented with a minimum sample preparation. Finally, vibrational modes of the functional groups were identified.

Agricultural soil characterization by FTIR spectroscopy at micrometer scales: Depth profiling by photoacoustic spectroscopy

In a Fourier transform mid-infrared photoacoustic spectroscopy (FTIR-PAS) mode, the scanning depths vary with the moving mirror velocity at specific wavenumbers, allowing depth profiling of materials. In this paper, we use FTIR-PAS spectroscopy to carry out a depth profiling of three types of agricultural soils (Fluvo-aquic soil, red soil and black soil) at micrometer scales by modulating the moving mirror velocity. The compositional and structural differences in soil organic matters were explored from the surface to a depth of about 4 μm. The results showed that the distribution of potential hydrophobic CH varied among different types of soils. The contribution of the soil organic matter (SOM) to the cation exchange capacity (CEC) also differed for each soil type. The results of the principal component analysis (PCA) indicated that most differences among the selected soil types occurred in the inner layer, and the discriminatory power of the soil spectra decreased with the reduction of scanning depths. Correlations between soil properties and spectral absorbance were carried out to determine the source of water extractable organic carbon (WEOC) of different soil types. For the black soil, WEOC were significantly and positively correlated to the absorbance at ~2920 cm−1, and this correlation increased with the probing depth at micrometer scales. However, the significant and negative correlation between the WEOC of the red soil, and the bond intensity of ~1650 cm−1 decreased with an increasing probing depth. This result demonstrates a selective retention of biotic components in the WEOC of the red soil. The WEOC of the black soil, with comparison to the red soil, has more contributions from the native organic matter. These results can be reasonably ascribed to different pedogenesis and cultivation systems that were practiced in the past.

Rapid and Nondestructive Detection of Pesticide Residues by Depth-Profiling Fourier Transform Infrared Photoacoustic Spectroscopy.

Detection of pesticide residues is important for ensuring food safety, and it has assumed increased significance. Traditional analytical methods are known for being destructive and cost- and time-intensive. In this study, depth-profiling Fourier transform infrared photoacoustic spectroscopy (FTIR-PAS) was successfully used as an in situ, nondestructive, and rapid method for detecting tricyclazole residues on three metal surfaces (copper, aluminum, and iron) and subsequently, on the surfaces of fresh rice leaves and ripe husks. Four moving mirror velocities, that is, 0.32, 0.63, 0.95, and 1.90 cm s–1 were used for recording the spectra. The results indicated that the moving mirror velocity of 0.95 cm s–1 was optimal for depth profiling, and the obtained spectra showed a strong absorption band at around 1200 cm–1, corresponding to the C–N bond in tricyclazole. This band could be used for monitoring tricyclazole residues on plant surfaces. Principal component analysis confirmed the detection of tricyclazole on the basis of its spectral information. Considering the scanning depth and the thickness of the plant cuticle, FTIR-PAS can be an effective means for detecting and monitoring similar organonitrogen pesticide residues.

Identification of Chinese medicinal fungus Cordyceps sinensis by depth-profiling mid-infrared photoacoustic spectroscopy

With increased demand for Cordyceps sinensis it needs rapid methods to meet the challenge of identification raised in quality control. In this study Cordyceps sinensis from four typical natural habitats in China was characterized by depth-profiling Fourier transform infrared photoacoustic spectroscopy. Results demonstrated that Cordyceps sinensis samples resulted in typical photoacoustic spectral appearance, but heterogeneity was sensed in the whole sample; due to the heterogeneity Cordyceps sinensis was represented by spectra of four groups including head, body, tail and leaf under a moving mirror velocity of 0.30cms−1. The spectra of the four groups were used as input of a probabilistic neural network (PNN) to identify the source of Cordyceps sinensis, and all the samples were correctly identified by the PNN model. Therefore, depth-profiling Fourier transform infrared photoacoustic spectroscopy provides novel and unique technique to identify Cordyceps sinensis, which shows great potential in quality control of Cordyceps sinensis.

Light reversing and folding based on a superluminal flying mirror in a plasma with increasing density

A superluminal flying mirror (SFM) is proposed using the electron density spike in the tail of a wake-field excited in a plasma with an increasing density profile. The wavelength of the wake-field is shrunk in the direction of the increasing plasma density, which increases the phase velocity of the wake wave—namely the flying mirror velocity—in excess of the speed of light. The SFM exhibits some novel characteristics. When it up-shifts the light frequency, just as with a normal flying mirror, because the velocity of the SFM is quicker than light, the reflected light penetrates the electron density spike and propagates behind it. The transmitted light can gain extra energy from the wake wave so that the transmission coefficient is higher than one. Most interestingly, the reflected light may be reversed or folded in time during the reflection, if the SFM velocity gradually decreases and goes through the speed of light. The proposed SFM mechanism can provide potential applications in the production of high-frequency ultrashort pulses.

Comparative study of photodegradation of wood by a UV laser and a xenon light source

A detailed study of photodegradation of wood surfaces by xenon light source and a UV laser has been carried out. Silver birch, rubberwood, Scots pine and chir pine wood veneers were irradiated with a xenon light source or a 244 nm argon ion laser. The changes in chemical structure of wood surfaces were monitored by UV resonance Raman (UVRR), photoacoustic Fourier transform infrared (FTIR-PAS) and UV–vis reflectance spectroscopies. The depth profile of xenon lamp irradiated wood surfaces was carried out by measuring FTIR-PAS spectra at different moving mirror velocities. The UVRR and FTIR-PAS spectra of irradiated wood surfaces showed degradation of aromatic structure in lignin combined with strong formation of carbonyl structures. The FTIR-PAS spectra measured from xenon irradiated wood surfaces indicate that hardwood lignin degrades at a faster rate than softwood lignin. The UVRR spectra of xenon irradiated wood show a significant decrease in the intensities of aromatic structures at 1602 cm −1. This is accompanied by a significant band broadening and notable shift towards longer wavenumbers, which has been attributed to the formation of o- and p-quinone structures as degradation products. The formation of quinone structures was also supported by the generation of a broad absorption band between 350 and 600 nm in UV–vis reflectance spectra of irradiated wood surfaces. There was a significant broadening in the region of 1500–1000 cm −1 in UVRR spectra due to the formation of unsaturated structures as a result of lignin degradation. The UVRR spectra of laser irradiated wood showed similar behaviour i.e., overall broadening and a rapid reduction in the intensity of lignin aromatic structure. The rate of degradation by laser was very high. However, the extent of band broadening was higher in xenon irradiated wood indicating the generation of several different types of structures as compared to laser irradiation, which produces only particular type of structures. UVRR spectra of laser irradiated Whatman paper showed significant photodegradation of cellulose by UV laser. The UV degradation rate of lignin was much higher than cellulose.

Quantum matter-wave dynamics with moving mirrors

When a stationary reflecting wall acting as a perfect mirror for an atomic beam with well-defined incident velocity is suddenly removed, the density profile develops during the time evolution an oscillatory pattern known as diffraction in time. The interference fringes are suppressed or their visibility is diminished by several effects such as averaging over a distribution of incident velocities, apodization of the aperture function, atom-atom interactions, imperfect reflection, or environmental noise. However, when the mirror moves with finite velocity along the direction of propagation of the beam, the visibility of the fringes is enhanced. For mirror velocities below beam velocity, as used for slowing down the beam, the matter wave splits into three regions separated by space-time points with classical analogs. For mirror velocities above beam velocity a visibility enhancement occurs without a classical counterpart. When the velocity of the beam approaches that of the mirror the density oscillations rise by a factor 1.8 over the stationary value.

Determination of lignin content in high-yield kraft pulps using photoacoustic rapid scan Fourier transform infrared spectroscopy

The spectra of a number of kraft pulps from Pinus radiata with varying lignin content (Kappa number) were obtained using a rapid scan photoacoustic Fourier transform infrared (PAS-FTIR) spectrometer and a method was developed for the determination of lignin content. A partial-least-squares (PLS) model was established based on spectral data collected at different mirror velocities. The robustness of the model was statistically evaluated. The outcomes indicate that the PLS model can be used to predict Kappa number of kraft pulps with a high degree of accuracy provided that the moving mirror velocity is ⩽0.5 cm/s.

Optimization of transmission near infrared spectrometry procedures for quality control of pesticide formulations

The use of different response functions to be optimized in the frame of the use of near infrared spectrometry for quality control of active principles in agrochemical formulations has been evaluated. Both, simple functions, based on parameters like sensitivity, repeatability, accuracy, signal to noise ratio, limit of detection or sample throughput, and a complex function, considering all the aforementioned aspects, were employed in the development of a new method for Iprodione determination in agrochemicals. Optimization strategies were based on the previous screening of the most important instrumental factors like number of cumulated scans, nominal resolution, mirror velocity and zero filling factor, based on a two-level full factorial design and on the search for the optimum conditions using central composite designs. Data found evidenced the influence of the response function on the optimum values of experimental conditions and could be employed as a general guide to evaluate the experimental factors in routine use of near infrared spectrometry. Finally the optimized method for Iprodione has been applied to the determination of Diuron and results found compared with those obtained by a conventional approach.

Fluctuations of quantum radiation pressure in dissipative fluid

Using the generalized Langevin equations involving the stress tensor approach, we study the dynamics of a perfectly reflecting mirror which is exposed to the electromagnetic radiation pressure by a laser beam in a fluid at finite temperature. Based on the fluctuation–dissipation theorem, the minimum uncertainty of the mirror's position measurement from both quantum and thermal noises effects including the photon counting error in the laser interferometer is obtained in the small time limit as compared with the “standard quantum limit”. The result of the large time behavior of fluctuations of the mirror's velocity in a dissipative environment can be applied to the laser interferometer of the ground-based gravitational wave detector.

Quantum radiation pressure on a moving mirror at finite temperature

We compute the radiation pressure force on a moving mirror, in the nonrelativistic approximation, assuming the field to be at temperature $T.$ At high temperature, the force has a dissipative component proportional to the mirror velocity, which results from Doppler shift of the reflected thermal photons. In the case of a scalar field, the force has also a dispersive component associated to a mass correction. In the electromagnetic case, the separate contributions to the mass correction from the two polarizations cancel. We also derive explicit results in the low temperature regime, and present numerical results for the general case. As an application, we compute the dissipation and decoherence rates for a mirror in a harmonic potential well.