arXiv subjects

Mohammad Ali Abbassi

Publications and source records attributed to Mohammad Ali Abbassi.

5 recordsLinked to original sources

arXiv2024

Recoil heating of a dielectric particle illuminated by a linearly polarized plane wave within the Rayleigh regime

We investigate the recoil heating phenomenon experienced by a dielectric spherical particle when it interacts with a linearly polarized plane wave within the Rayleigh regime. We derive the fluctuating force acted upon the particle arising from the fluctuations of the electromagnetic fields. Our derivations reveal that the spectral density of the fluctuating force along the propagation direction is $7\hbar ω_0 P_{\mathrm{scat}}/5c^2$. Meanwhile, along the direction of the electric and magnetic fields, it is $\hbar ω_0 P_{\mathrm{scat}}/5c^2$ and $2\hbar ω_0 P_{\mathrm{scat}}/5c^2$, respectively. Here, $P_{\mathrm{scat}}$ denotes the power scattered by the particle, $\hbarω_0$ represents the energy of a photon, and $c$ is the speed of light. Recoil heating imposes fundamental limitations in levitated optomechanics, constraining the minimum temperatures achievable in cooling processes, the coherence time of the system, and the sensitivity of force measurements.

physics.optics↗

arXiv2024

Radiation damping of a Rayleigh scatterer illuminated by a plane wave

We investigate the radiation damping experienced by a dielectric spherical particle when it is illuminated by an electromagnetic plane wave within the Rayleigh regime. We derive the equivalent electric dipole of the moving particle and subsequently calculate the electromagnetic force acting on it from two different approaches. In the first approach, we calculate the force from the integration of stress tensor and field momentum. In the second one, we calculate the force directly from the integration of the force density. Our derivations reveal that the damping coefficient is equal to $6P_{scat}/mc^2$ along the propagation direction, whereas it is $P_{scat}/mc^2$ along perpendicular directions. Here, $P_{scat}$ denotes the power scattered by the particle, and $mc^2$ represents the particle's mass energy. The radiation damping derived in this study sets upper limits on the quality factor of optically levitated objects and ensures the existence of a steady-state solution of the particle's dynamics.

physics.optics↗

arXiv2019

Wide-Band/Angle Blazed Dual Mode Metallic Groove Gratings

We introduce a new and simple approach to acquire wide-band/angle blazing operation in one-dimensional metallic gratings supported by equivalent circuit analysis. The gratings that are investigated here are single-groove gratings that support two propagating guided modes. It is shown that under such operating conditions, one can achieve blazing over a wide range of frequencies and angles. Parameters of the proposed equivalent circuit model for the case of the transverse magnetic (TM) polarization are analytically derived. The accuracy of the models is verified through comparison against results of full-wave simulations. The procedure to achieve wide-band/angle blazing performance is delineated and the design parameters are explicitly given. It is shown that this structure is able to strongly transfer the power of the transverse magnetic (TM) polarized incident wave to the -1-th diffraction order with a fractional bandwidth of 50 % at working frequency f_0 equal to 10 GHz and for -10 dB specular reflection loss, thus realizing a broadband structure. From the circuit model, an insightful discussion is presented at various mechanisms at play, when Bragg and off-Bragg blazing occurs and fully justifies the behavior of the device. The proposed technique opens up new vistas in a wide range of applications such as spectroscopy, Littrow cavities, beam splitters, and frequency scanned antenna reflectors.

physics.class-ph↗

arXiv2018

Inclusion of the backaction term in the total optical force exerted upon Rayleigh particles in nonresonant structures

In this paper, we investigate the impact of the electromagnetic scattering caused by other objects in nonfree space on the time averaged force exerted upon a Rayleigh particle, which is conventionally referred to as the backaction effect. We show that backaction modifies the gradient force, radiation pressure, and spin curl force exerted upon Rayleigh particles, and gives rise to an additional force term which stems from the gradient of the backaction field in nonfree space. As a numerical example, we look into the trapping of a dielectric nanoparticle at the center of curvature of a spherical mirror, and study how it is affected by the backaction effect. We show that backaction can enhance the force exerted upon the particle, reshape the trapping potential, and shift the equilibrium position of the particle.

physics.optics↗

arXiv2018

Employing coupled cavities to increase the cooling rate of a levitated nanosphere in the resolved sideband regime

In this paper we investigate cooling of a levitated nanosphere in a system of coupled cavities in the resolved sideband regime. Thanks to the presence of an extra resonance in the coupled cavity cooling system, the coupling strength can be maximized at the optimum detuning. In this fashion, the intra-cavity photon number is increased and thereby the cooling rate is enhanced and the strong coupling regime is achieved without resorting to increased driving laser power. The underlying physics of the increased cooling efficiency in the here-proposed system of coupled cavities in the resolved sideband regime and that of the already reported system of coupled cavities in the unresolved sideband regime are significantly different from each other. Since the spectral density of the displacement of the particle can no longer be accurately approximated by the conventional Lorentzian lineshape in the strong coupling regime, a double Lorentzian lineshape is employed to accurately approximate the spectral density of the displacement of the particle and to provide analytical formulations for the cooling rate. The analytical expression given for the cooling rate is validated by numerical simulations.

quant-ph↗