ترغب بنشر مسار تعليمي؟ اضغط هنا

Angular momentum exchange between coherent light and matter fields

170   0   0.0 ( 0 )
 نشر من قبل Tapio Simula
 تاريخ النشر 2007
  مجال البحث فيزياء
والبحث باللغة English




اسأل ChatGPT حول البحث

Full, three dimensional, time-dependent simulations are presented demonstrating the quantized transfer of angular momentum to a Bose-Einstein condensate from a laser carrying orbital angular momentum in a Laguerre-Gaussian mode. The process is described in terms of coherent Bragg scattering of atoms from a chiral optical lattice. The transfer efficiency and the angular momentum content of the output coupled vortex state are analyzed and compared with a recent experiment.



قيم البحث

اقرأ أيضاً

109 - Simon Streib 2020
In condensed matter systems it is necessary to distinguish between the momentum of the constituents of the system and the pseudomomentum of quasiparticles. The same distinction is also valid for angular momentum and pseudoangular momentum. Based on N oethers theorem, we demonstrate that the recently discussed orbital angular momenta of phonons and magnons are pseudoangular momenta. This conceptual difference is important for a proper understanding of the transfer of angular momentum in condensed matter systems, especially in spintronics applications.
We consider the forces exerted by a pulse of plane-wave light on a single atom. The leading edge of the pulse exerts a dispersive force on the atom, and this modifies the atomic momentum while the atom is enveloped in the light. The standard view of the optical dipole force indicates that red-detuned light should attract the atom towards high intensity. This should increase the average momentum per photon to $textbf{p}_{0} n$, where $textbf{p}_{0}$ is the photon momentum in free space and $n$ is the average refractive index due to the presence of the atom in the light. We show, however, that this is the wrong conclusion and that the atom is in fact repelled from the light by the dispersive forces, giving the photons a momentum $textbf{p}_{0} /n$. This leads us to identify Abrahams optical momentum with the kinetic momentum transfer. The form due to Minkowski is similarly associated with the canonical momentum. We consider the possibility of demonstrating this in the laboratory, and we note an unexpected connection with the Aharonov-Casher effect.
We report ferromagnetic resonance in the normal configuration of an electrically insulating magnetic bilayer consisting of two yttrium iron garnet (YIG) films epitaxially grown on both sides of a 0.5-mm-thick nonmagnetic gadolinium gallium garnet (GG G) slab. An interference pattern is observed and it is explained as the strong coupling of the magnetization dynamics of the two YIG layers either in phase or out of phase by the standing transverse sound waves, which are excited through a magnetoelastic interaction. This coherent mediation of angular momentum by circularly polarized phonons through a nonmagnetic material over macroscopic distances can be useful for future information technologies.
We propose a procedure to achieve a complete energy conversion between laser pulses carrying orbital angular momentum (OAM) in a cloud of cold atoms characterized by a double-Lambda atom-light coupling scheme. A pair of resonant spatially dependent c ontrol fields prepare atoms in a position-dependent coherent population trapping state, while a pair of much weaker vortex probe beams propagate in the coherently driven atomic medium. Using the adiabatic approximation we derive the propagation equations for the probe beams. We consider a situation where the second control field is absent at the entrance to the atomic cloud and the first control field goes to zero at the end of the atomic medium. In that case the incident vortex probe beam can transfer its OAM to a generated probe beam. We show that the efficiency of such an energy conversion approaches the unity under the adiabatic condition. On the other hand, by using spatially independent profiles of the control fields, the maximum conversion efficiency is only 1/2.
Fundamental and applied concepts concerning the ability of light beams to carry a certain mechanical angular momentum with respect to the propagation axis are reviewed and discussed. Following issues are included: Historical reference; Angular mo mentum of a paraxial beam and its constituents; Spin angular momentum and paradoxes associated with it; Orbital angular momentum; Circularly-spiral beams: examples and methods of generation; Orbital angular momentum and the intensity moments; Symmetry breakdown and decomposition of the orbital angular momentum; Mechanical models of the vortex light beams; Mechanical action of the beam angular momentum; Rotational Doppler effect, its manifestation in the image rotation; Spectrum of helical harmonics and associated problems; Non-collinear rotational Doppler effect; Properties of a beam forcedly rotating around its own axis. Research prospects and ways of practical utilization of optical beams with angular momentum.
التعليقات
جاري جلب التعليقات جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
mircosoft-partner

هل ترغب بارسال اشعارات عن اخر التحديثات في شمرا-اكاديميا