| 2. |
- Hanstorp, Dag, 1960, et al.
(författare)
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A versatile system for optical manipulation experiments
- 2017
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Ingår i: Proceedings of SPIE - The International Society for Optical Engineering. SPIE Nanoscience + Engineering, 2017, San Diego, California, United States. - : SPIE. - 0277-786X .- 1996-756X. - 9781510611528
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Konferensbidrag (refereegranskat)abstract
- Downloading of the abstract is permitted for personal use only. In this paper a versatile experimental system for optical levitation is presented. Microscopic liquid droplets are produced on demand from piezo-electrically driven dispensers. The charge of the droplets is controlled by applying an electric field on the piezo-dispenser head. The dispenser releases droplets into a vertically focused laser beam. The size and position in 3 dimensions of trapped droplets are measured using two orthogonally placed high speed cameras. Alternatively, the vertical position is determined by imaging scattered light onto a position sensitive detector. The charge of a trapped droplets is determined by recording its motion when an electric field is applied, and the charge can be altered by exposing the droplet to a radioactive source or UV light. Further, spectroscopic information of the trapped droplet is obtained by imaging the droplet on the entrance slit of a spectrometer. Finally, the trapping cell can be evacuated, allowing investigations of droplet dynamics in vacuum. The system is utilized to study a variety of physical phenomena, and three pilot experiments are given in this paper. First, a system used to control and measure the charge of the droplet is presented. Second, it is demonstrated how particles can be made to rotate and spin by trapping them using optical vortices. Finally, the Raman spectra of trapped glycerol droplets are obtained and analyzed. The long term goal of this work is to create a system where interactions of droplets with the surrounding medium or with other droplets can be studied with full control of all physical variables.
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| 3. |
- Muralidhar, Shreyas, et al.
(författare)
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Sustained coherent spin wave emission using frequency combs
- 2020
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Ingår i: Physical Review B. - 2469-9950. ; 101:22
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Tidskriftsartikel (refereegranskat)abstract
- We demonstrate sustained coherent emission of spin waves in NiFe films using rapid demagnetization from high repetition rate femtosecond laser pulse trains. As the pulse separation is shorter than the magnon decay time, magnons having a frequency equal to a multiple of the 1 GHz repetition rate are coherently amplified. Using scanning Brillouin light scattering (BLS) microscopy, we observe this coherent amplification as strong peaks spaced 1 GHz apart. The BLS counts vs laser power exhibit a stronger than parabolic dependence consistent with counts being proportional to the square of the magnetodynamic amplitude, and the demagnetization pulse strength being described by a Bloch law. Spatial spin wave mapping demonstrates how both localized and propagating spin waves can be excited, and how the propagation direction can be directly controlled. Our results demonstrate the versatility of frequency combs and BLS spectroscopy for rapid demagnetization studies, and enable a platform for photomagnonics where sustained coherent spin waves can be utilized.
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