Radiation Pressure Force Research Articles

Material Extrusion on an Ultrasonic Air Bed for 3D Printing

Abstract Additive manufacturing, such as 3D printing, offers unparalleled opportunities for rapid prototyping of objects, but typically requires simultaneous building of solid supports to minimize deformation and ensure contact with the printing surface. Here, we theoretically and experimentally investigate the concept of material extrusion on an “air bed”—an engineered ultrasonic acoustic field that stabilizes and supports the soft material by contactless radiation pressure force. We study the dynamics of polylactic acid filament—a commonly used material in 3D printing—as it interacts with the acoustic potential during extrusion. We develop a numerical radiation pressure model to determine optimal configurations of ultrasonic transducers to generate acoustic fields and conditions for linear printing. We build a concept prototype that integrates an acoustic levitation array with a 3D printer and use this device to demonstrate linear extrusion on an acoustic air bed. Our results indicate that controlled interactions between acoustic fields and soft materials could offer alternative support mechanisms in additive manufacturing with potential benefits such as less material waste, fewer surface defects, and reduced material processing time.

Mysterious non-detection of HeI (23S) transit absorption of GJ436b

Abstract Possible reasons for the non-detection of absorption in the metastable HeI(23S) line at transit observations of warm Neptune GJ436b, in spite of the well pronounced strong absorption features measured earlier in Lyα for this planet, are investigated. We perform numeric simulations of the escaping upper atmosphere of this planet and its HeI(23S) triplet absorption with a global 3D multi-fluid self-consistent hydrodynamic model. By fitting the model parameters to the lowest detection level of absorption measurements, we constrain an upper limit the He/H abundance three times smaller than the solar value. We demonstrate that neither the significant changes of the stellar wind related with possible stellar coronal mass ejections (CMEs), or possible variations in the stellar ionization radiation, nor the presence of heavy trace elements have crucial effect on the absorption at the 10 830 Å line of HeI(23S) triplet. The main reason of weak signature is that the region populated by the absorbing metastable helium is rather small (<3Rp), as well as the small size of the planet itself, in comparison to the host star. We show that the radiation pressure force acting on the HeI(23S) atoms spreads them along the line of sight and around the planet, thus further reducing peak absorption.

Adapting empirical solar radiation pressure model for BDS-3 medium Earth orbit satellites

For the precise orbit determination (POD) of global navigation satellite systems (GNSS) constellation, it is very difficult to precisely model the solar radiation pressure (SRP) force acting on GNSS satellites. For GPS satellites, the ECOM model developed by the Center for Orbit Determination in Europe has been utilized by most of International GNSS Service (IGS) analysis centers. However, it should be adapted and optimized to the characteristics of satellites of each GNSS system or even individual satellites. It was extended to the ECOM2 model for GLONASS satellites and then for Galileo satellites by employing a box–wing model. Since November 2020, the third generation of the BeiDou satellite system (BDS-3) has been in its full operation and there are about 200 globally distributed IGS ground stations tracking BDS-3 signals, which creates a great potential to evaluate and optimize its SRP modeling. From the POD processing carried out in this study, we found significant fluctuations of up to 20 cm in overlapping orbit differences for satellites over eclipses in the radial direction and of about 20 and 50 cm in the cross and along directions for ECOM2 and ECOM models. Then, based on numerical analyses we demonstrate that the fourth- and sixth-order sine terms in the Sun direction can significantly reduce the overlapping orbit differences of ECOM. Therefore, an adapted SRP model by adding the fourth- and sixth-order sine periodical terms in the Sun direction to the ECOM model is presented. The adapted model is then validated for BDS-3 POD and orbit prediction. Results show that fluctuations in the amplitude of overlapping estimated orbits using ECOM models are reduced from 20 to < 10 cm in the radial-track component and satellite laser ranging residuals are reduced to half by the adapted SRP model. For the predicted BDS-3 satellite orbits, the RMS values over deep eclipses can be improved from about 7, 14 and 26 cm to about 3, 5 and 12 cm, in the radial, cross and along directions, respectively, compared to the ECOM model.

Nanoscale optimization of the opto-hydrodynamical air-water interface deformation

The aim of this work is to demonstrate numerically an optimal enhancement of nanoscale opto-hydrodynamic deformation of an air-water interface that involves an interaction between the size of the fluid medium and geometry of the continuous wave laser beam for a fixed radiation pressure force. We find a critical value of beam radii (ωc) which produces the maximum deformation with a rapid onset time (ton∼O(10−8) s) and high saturation time (tsat∼O(10−2) s). Additionally, we show how the beam radius and water depth regulate an early onset and saturation time which depends linearly on the water depth once the optimal condition is achieved. Interestingly, we also show the stable and dynamic zones for deformation at the air-water interface. It is possible to validate our numerical results by using a variety of experimentally derived parameters, and these findings affect the characterization of complex fluids at the nanoscale.

Engineered entropic forces allow ultrastrong dynamical backaction.

When confined within an optical cavity light can exert strong radiation pressure forces. Combined with dynamical backaction, this enables important processes, such as laser cooling, and applications ranging from precision sensors to quantum memories and interfaces. However, the magnitude of radiation pressure forces is constrained by the energy mismatch between photons and phonons. Here, we overcome this barrier using entropic forces arising from the absorption of light. We show that entropic forces can exceed the radiation pressure force by eight orders of magnitude and demonstrate this using a superfluid helium third-sound resonator. We develop a framework to engineer the dynamical backaction from entropic forces, applying it to achieve phonon lasing with a threshold three orders of magnitude lower than previous work. Our results present a pathway to exploit entropic forces in quantum devices and to study nonlinear fluid phenomena such as turbulence and solitons.

Synchronization of Optomechanical Oscillator and Breathing Soliton

AbstractSynchronization and frequency locking between different oscillators are of scientific and technological importance in a wide variety of fields. The optomechanical resonator can be a good integrated oscillator, which takes place via the radiation pressure force induced by the optical fields. In addition, the breathing soliton is a particular kind of dissipative Kerr soliton that exists between the modulation instability state and the stable state, which shows periodic oscillation in pulse width and amplitude, as well as in its spectral envelope. The breathing frequency depends on the pump power and the pump detuning, which can be affected by environmental fluctuations, and the linewidth of the RF beatnote is on the order of megahertz (MHz). Here, the synchronization of these two different oscillators, that is, the optomechanical oscillator and the breathing soliton, is demonstrated. This demonstration transfers the stability and narrow linewidth of the optomechanical oscillator to the breathing soliton. The fixed phase relation between the breathing oscillation and optomechanical oscillation can be established, forming an open Lissajous diagram. These results provide a new way for the stabilization and control of the breathing soliton and may inspire the study of the interaction between the optomechanical oscillator and the breathing soliton.

Influence of Solar Activity on Precise Orbit Prediction of LEO Satellites

The perturbations of low earth orbit (LEO) satellites operating in the orbit of 300 ∼ 2000 km are complicated. In particular, the atmospheric drag force and solar radiation pressure force change rapidly over a short period of time due to solar activities. Using spaceborne global positioning system (GPS) data of the CHAMP, GRACE and SWARM satellites from 2002 to 2020, this paper studies in depth the influence of solar activity on LEO satellites’ precise orbit prediction by performing a series of orbit prediction experiments. The quality of GPS data is more susceptible to being influenced by solar activity during years when this activity is high and the changes in dynamic parameters are consistent with those of solar activity. The effects of solar activity on LEO orbit prediction accuracy are analyzed by comparing the predicted orbits with the precise ones. During years of high solar activity, the average root-mean-squares prediction errors at 10, 20, and 30 minutes are 0.15, 0.20, and 0.26 m, respectively, which are larger than the corresponding values in low-solar-activity years by 59%, 63%, and 68%, respectively. These results demonstrate that solar activity has a great influence on the orbit prediction accuracy, especially during high-solar-activity years. We should strengthen the real-time monitoring of solar activity and geomagnetic activity, and formulate corresponding orbit prediction strategies for the active solar period.

Tunable Transparency and Group Delay in Cavity Optomechanical Systems with Degenerate Fermi Gas

We theoretically investigate the optical response and the propagation of an external probe field in a Fabry–Perot cavity, which consists of a mechanical mode of trapped, ultracold, fermionic atoms inside and simultaneously driven by an optical laser field. We investigate the electromagnetically-induced transparency due to coupling of the optical cavity field with the collective density excitations of the ultracold fermionic atoms via radiation pressure force. Moreover, we discuss the variations in the phase and group delay of the transmitted probe field with respect to effective cavity detuning as well as pumping power. It is observed that the transmitted field is lagging in this fermionic cavity optomechanical system. Our study shall provide a method to control the propagation as well as the speed of the transmitted probe field in this kind of fermionic, ultracold, atom-based, optomechanical cavity system, which might have potential applications in optical communications, signal processing and quantum information processing.

On the Fine-tuning and Physical Origin of Line-locked Absorption Systems in Active Galaxies

Line locking (LL) of absorption-line systems is a clear signature of the dynamical importance of radiation-pressure force in driving astrophysical flows, with recent findings suggesting that it may be common in quasars exhibiting multiple intrinsic narrow absorption-line (NAL) systems. In this work, we probe the phase space conducive to LL and follow the detailed kinematics of those systems that may lock at the velocity separation of the C iv λ λ1548.19, 1550.77 doublet. We find that a small volume of the phase-phase admits LL, suggesting a high degree of fine-tuning between the physical properties of locked systems. The stability of LL against quasar luminosity variations is quantified with implications for the long-term variability amplitude of quasars and the velocity-separation statistic between multiple NAL systems. The high occurrence of LL by the C iv doublet implies that the hidden extreme-UV emission from quasars is unlikely to be significantly underestimated by current models. Further, the ratio of the LL velocity to the outflow velocity may serve as a powerful constraint on the composition of the accelerating medium. We conclude that LL poses significant challenges to current theories for the formation of nonintervening NAL systems, and speculate that it may be a manifestation of expanding circumstellar shells around asymptotic giant branch stars in the quasar-host bulge.

On charged photons in unmagnetized dusty plasma instabilities

Motivated by the expanding interest in complex plasmas, we discuss the equivalent photon charge in dusty electron-ion plasmas. Particularly, we investigate the dusty plasma response in terms of the electron density perturbation driven by electromagnetic waves. The resulting polarization of this plasma medium caused by the photon ponderomotive force of the electromagnetic radiation pressure gives rise to an effective photon electric charge. We determine the acquired photon charge in terms of the involved characteristic parameters. More precisely, here we derive an explicit expression of the photon charge which is found to depend strongly on the free electron density and the photon frequency. Such a photonic charge is relevant for dealing with the photon–plasma couplings in most plasma mediums, namely of the early Universe.

Nonreciprocal Frequency Conversion and Mode Routing in a Microresonator

The transportation of photons and phonons typically obeys the principle of reciprocity. Breaking reciprocity of these bosonic excitations will enable the corresponding nonreciprocal devices, such as isolators and circulators. Here, we use two optical modes and two mechanical modes in a microresonator to form a four-mode plaquette via radiation pressure force. The phase-controlled nonreciprocal routing between any two modes with completely different frequencies is demonstrated, including the routing of phonon to phonon (megahertz to megahertz), photon to phonon (terahertz to megahertz), and especially photon to photon with frequency difference of around 80THz for the first time. In addition, one more mechanical mode is introduced to this plaquette to realize a phononic circulator in such single microresonator. The nonreciprocity is derived from interference between multimode transfer processes involving optomechanical interactions in an optomechanical resonator. It not only demonstrates the nonreciprocal routing of photons and phonons in a single resonator but also realizes the nonreciprocal frequency conversion for photons and circulation for phonons, laying a foundation for studying directional routing and thermal management in an optomechanical hybrid network.

LIBRATION POINTS AND STABILITY OF AN OBLATE TEST PARTICLE IN THE SUN-EARTH SYSTEM OF THE RESTRICTED THREE-BODY PROBLEM

This paper examines libration points and stability of a test particle having the shape of an oblate spheroid under the gravitational effect of a radiating first primary and an oblate shaped second primary using the model of the restricted three-body problem. The equations of motion have been stated and the libration points examined. It is seen that there exist a pair of triangular points which are defined by the radiation pressure force of the first primary, and oblateness of the second primary and the test particle. Further, there can be up to five collinear libration points in the presence of oblateness of either the second primary or the test particle. We examine the stability of the libration points and it is seen that the triangular points are linearly stable in the sense that the roots of the characteristic equation are all distinct imaginary roots, which produce bounded motion around the triangular points, while the collinear points are unstable due to the presence of a positive root. Further, we explore the periodic orbits around linearly stable triangular points and it was seen that the orbits are elliptic. The elements of the orbits, among which are the frequency, orientation, eccentricities, lengths of the semi-major and semi-minor axis have all been obtained and are defined by the radiation pressure of the first primary and oblateness of the second primary and the test particle. These outcomes have been verified numerically when the radiating first primary is the Sun and the oblate second primary is the Earth.

Giant injection-locking bandwidth of a self-pulsing limit-cycle in an optomechanical cavity

Locking of oscillators to ultra-stable external sources is of paramount importance for improving close-to-carrier phase noise in free running oscillators. In most of them, such as Micro-Electro-Mechanical-Systems or LC circuit-based oscillators, the locking frequency range is limited by the robustness of their natural frequency, which comes explicitly related with intrinsic parameters of the system. In this work we report the synchronization of an optically-driven self-pulsing limit-cycle taking place in a silicon optomechanical crystal cavity to an external harmonic signal that modulates the driving laser. Because of the extreme ductility of the natural self-pulsing frequency (several tens of MHz), the injection-locking mechanism is highly efficient and displays giant relative bandwidths exceeding 60%. The external modulation reveals itself as a knob to explore dynamical attractors that are otherwise elusive and, in particular, as a means to initialize a mechanical resonator into a state of self-sustained oscillations driven by radiation pressure forces. Moreover, we exploit the large anharmonicity of the studied limit-cycle to induce injection-locking to integer multiples and fractions of the frequency of the external reference, which can be used for frequency conversion purposes in nano-electro-opto-mechanical systems.

Broadband radiation pressure on a small period diffractive film.

The p-polarization component of radiation pressure force from an unpolarized blackbody light source is predicted by the use of a Maxwell equation solver for a right triangular prism grating of period 2 μm and refractive index 3.5. The transmitted and reflected angular scattering distributions are found to qualitatively agree with diffraction theory: At relatively short wavelengths the transmitted light is concentrated near the refraction angle, and reflected light is concentrated near the reflection angle. Owing to diffraction and multiple internal reflections, however, the spectral irradiance of transmitted and reflected light was found to significantly vary with wavelength. We found that the high value of the refractive index produced a large fraction of reflected light, thereby reducing the net transverse component of radiation pressure force. These results suggest that low index transmission gratings, anti-reflection coatings, optimized metasurface films, or reflection gratings should be explored for future solar sailing missions.

Light as a quantum back-action nullifying meter

We propose a new, to the best of our knowledge, method to overcome quantum back-action in a measurement process using oscillators. An optical oscillator is used as a meter to measure the parameters of another open oscillator. The optical oscillator is synthesized such that the optical restoring force counters any perturbations induced by the quantum back-action phenomena. As a result, it is shown that the quantum back-action in continuous measurement is suppressed in the low frequency regime, i.e., for frequencies much smaller than the resonance frequency of the open oscillator. As the meter plays the role of measuring parameters as well as suppressing the quantum back-action, we call it a quantum back-action nullifying meter. As an application of this method, synthesis of the quantum back-action nullifying optical oscillator for suppressing radiation pressure force noise in linear and non-linear optomechanics is described.

Shift of the photoelectron momentum against the radiation pressure force in linearly polarized intense midinfrared laser fields

The propagation direction momentum component of direct photoelectrons emitted by ionization of an atomic target in an intense, linearly polarized, midinfrared laser field is analyzed. Within the dipole approximation, the average value of this component is zero. However, when nondipole corrections are included, it becomes nonzero. Applying the saddle-point approximation to compute the integral over the ionization times in the expression for the nondipole strong-field approximation differential ionization rate, we surprisingly find a negative momentum shift, corresponding to a shift against the radiation pressure force. Our analysis shows that there is a positive contribution originating from individual ionization pathways within one optical cycle. The interference of contributions from ionization pathways arising within the same optical cycle of the field (intracycle interference) causes an oscillatory behavior, which, crossing to negative values, induces the shift against the radiation pressure force.

Large-scale outflow structure and radiation properties of super-Eddington flow: Dependence on the accretion rates

Abstract In order to evaluate the impacts made by super-Eddington accretors on their environments precisely, it is essential to guarantee a large enough simulation box and long computational time to avoid any artefacts from numerical settings as much as possible. In this paper, we carry out axisymmetric two-dimensional radiation hydrodynamic simulations around a 10 M⊙ black hole in large simulation boxes and study the large-scale outflow structure and radiation properties of super-Eddington accretion flow for a variety of black hole accretion rates, ${\dot{M}}_{\,\,\rm BH} = (110\!-\!380)L_{\rm Edd}/c^{\,\,2}$ (with LEdd being the Eddington luminosity and c being the speed of light). The Keplerian radius of the inflow material, at which centrifugal force balances with gravitational force, is fixed to 2430 Schwarzschild radii. We find that the mechanical luminosity grows more rapidly than the radiation luminosity with an increase of ${\dot{M}}_{\,\,\rm BH}$. When seen from a nearly face-on direction, especially, the isotropic mechanical luminosity grows in proportion to ${\dot{M}}_{\,\,\rm BH}^{\,\,2.7}$, while the total mechanical luminosity is proportional to ${\dot{M}}_{\,\,\rm BH}^{\,\,1.7}$. The reason for the former is that the higher ${\dot{M}}_{\,\,\rm BH}$ is, the more vertically inflated the disk surface becomes, which makes radiation fields more confined in the region around the rotation axis, thereby strongly accelerating outflowing gas. The outflow is classified into pure outflow and failed outflow, depending on whether the outflowing gas can reach the outer boundary of the simulation box or not. The fraction of the failed outflow decreases with a decrease of ${\dot{M}}_{\,\,\rm BH}$. We analyze physical quantities along each outflow trajectory, finding that the Bernoulli parameter (Be) is not a good indicator to discriminate between pure and failed outflows, since it is never constant because of continuous acceleration by radiation-pressure force. Pure outflow can arise, even if Be &amp;lt; 0 at the launching point.

Observation of Photon-Phonon Correlations Via Dissipative Filtering

Cavity-optomechanics enables photon-phonon interaction and correlations by harnessing the radiation-pressure force. Here, we realize a ``cavity-in-a-membrane'' optomechanical architecture which allows detection of the motion of lithographically-defined, ultrathin membranes via an integrated optical cavity. Using a dissipative filtering method, we are able to eliminate the probe light in situ and observe photon-phonon correlations associated with the low-frequency membrane mechanical mode. The developed method is generally applicable for study of low-frequency light scattering processes where conventional frequency-selective filtering is unfeasible.

Limit cycles and chaos in the hybrid atom-optomechanics system

We consider atoms in two different periodic potentials induced by different lasers, one of which is coupled to a mechanical membrane via radiation pressure force. The atoms are intrinsically two-level systems that can absorb or emit photons, but the dynamics of their position and momentum are treated classically. On the other hand, the membrane, the cavity field, and the intrinsic two-level atoms are treated quantum mechanically. We show that the mean excitation of the three systems can be stable, periodically oscillating, or in a chaotic state depending on the strength of the coupling between them. We define regular, limit cycle, and chaotic phases, and present a phase diagram where the three phases can be achieved by manipulating the field-membrane and field-atom coupling strengths. We also computed other observable quantities that can reflect the system’s phase such as position, momentum, and correlation functions. Our proposal offers a new way to generate and tune the limit cycle and chaotic phases in a well-established atom-optomechanics system.

Theory of radiation pressure on a diffractive solar sail

Solar sails propelled by radiation pressure enable space missions that cannot be achieved using chemical rockets alone. Significant in-space propulsion for missions such as a solar polar orbiter may be achieved with a sail that deviates sunlight at a large average angular direction. The momentum transfer efficiency of sunlight diffracted from a Sun-facing diffractive sail comprising periodic right prism elements is examined here. The spectrally averaged efficiency, integrated across the solar blackbody spectrum, is found to approach that of a monolithic prism when the grating period is much longer than the peak of the solar spectrum. This idealized diffraction analysis predicts a greater transverse radiation pressure force compared to an idealized reflective sail. With modern optical design and fabrication techniques, optimized diffractive solar sails may one day replace reflective sails.