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Optical signatures of the coupled spin-mechanics of a levitated magnetic microparticle

Vanessa Wachter, Victor A. S. V. Bittencourt, Shangran Xie, Sanchar Sharma, Nicolas Joly, Philip Russell, Florian Marquardt, Silvia Viola-Kusminskiy

We propose a platform that combines the fields of cavity optomagnonics and levitated optome- chanics in order to control and probe the coupled spin-mechanics of magnetic dielectric particles. We theoretically study the dynamics of a levitated Faraday-active dielectric microsphere serving as an optomagnonic cavity, placed in an external magnetic field and driven by an external laser. We find that the optically driven magnetization dynamics induces angular oscillations of the particle with low associated damping. Further, we show that the magnetization and angular motion dynamics can be probed via the power spectrum of the outgoing light. Namely, the characteristic frequencies attributed to the angular oscillations and the spin dynamics are imprinted in the light spectrum by two main resonance peaks. Additionally, we demonstrate that a ferromagnetic resonance setup with an oscillatory perpendicular magnetic field can enhance the resonance peak corresponding to the spin oscillations and induce fast rotations of the particle around its anisotropy axis.

Pulsating iron spectral features in the emission of X-ray pulsar V 0332+53

D. S. Bykov, E. V. Filippova, M. R. Gilfanov, S. S. Tsygankov, A. A. Lutovinov, S. V. Molkov

We present results of phase- and time-resolved study of iron spectral features in the emission of the Be/X-ray transient pulsar V 0332+53 during its type II outburst in 2004 using archival RXTE/PCA data. Coherent pulsations of both fluorescent iron line at ≈6.4 keV and neutral iron K-edge at ≈7.1 keV have been detected throughout the entire outburst. The pulsating iron K-edge is reported for the first time for this object. Near the peak of the outburst, the 3–12 keV pulse profile shows two deep, F_max/F_min ∼ 2, and narrow dips of nearly identical shape, separated by exactly Δϕ = 0.5 in phase. The dip spectra are nearly identical to each other and very similar in shape to the spectra outside the dips. The iron K-edge peaks at the phase intervals corresponding to the dips, although its optical depth τ_K ∼ 0.05 is by far insufficient to explain the dips. The iron line shows pulsations with a complex pulse profile without any obvious correlation with the total flux or optical depth of the K-edge. Accounting for the component associated with reprocessing of the pulsar emission by the surface of the donor star and circumstellar material, we find a very high pulsation amplitude of the iron line flux, F_max/F_min ∼ 10. We demonstrate that these properties of V 0332+53 cannot be explained by contemporary emission models for accreting X-ray pulsars and speculate about the origin of the observed iron spectral features.

Specialty Photonic Crystal Fibers and Their Applications

David Novoa, Nicolas Joly

This year not only commemorates the 60th anniversary of nonlinear optics with the seminal experiment of second harmonic generation, but it is also the 30th anniversary of the invention of the photonic crystal fiber (PCF). Following their first practical demonstration in 1996, PCFs have rapidly evolved into an established platform for applications in both academic and industrial environments. Their unique ability to confine light in a far more versatile way than possible with conventional optical fibers facilitated the expansion of the multifaceted world of PCF to cover not only nonlinear optics, but also many other disparate fields such as interferometry, beam delivery, laser science, telecommunications, quantum optics, sensing, microscopy, and many others.