2017 Fiscal Year Research-status Report
Storage of photon with orbital angular momentum based on an all-fiber system
| Project/Area Number |
17K14127
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| Research Institution | Okinawa Institute of Science and Technology Graduate University |
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Principal Investigator |
Du Jinjin 沖縄科学技術大学院大学, 光・物質相互作用ユニット, 研究員 (70795301)
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| Project Period (FY) |
2017-04-01 – 2019-03-31
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| Keywords | quantum optics |
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| Outline of Annual Research Achievements |
We have fabricated high-order modes(HOM) optical nanofibers with the highest possible transmission and taking ~ 100 mW in the vacuum chamber, which is a significant step towards atom trapping near fibre surface. HOM nanofibers have been installed into the vacuum system and fluorescence photons from cold atoms in the MOT were directly collected by the fibre output ports. Each eigenmodes of the LP11 group of this nanofiber have been excited and separated by injecting the vector beams in free space. In order to increase the duration time of atoms in the evanescent field of fibre, we have realized effective temperature of atoms in the MOT down to tens of uK by using polarization gradient cooling. We have developed LabVIEW programmes to control the whole experiment processing.
The interaction strength for different modes have been obtained by measuring the atomic absorption spectra of the guided resonant beam. This make a first step towards the transfer of orbital angular momentum (OAM) in atom-fibre system based on four wave mixing(FWM). We have built the laser systems which will be used as pumping beams in four wave mixing process. The wavelength of lasers has been locked to atomic transition line by using saturated absorption spectroscopy or two photon absorption spectroscopy. The signal of FWM have been obtained in free space but we have not implemented in atom-fibre system.
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| Current Status of Research Progress |
Current Status of Research Progress
3: Progress in research has been slightly delayed.
Reason
We have gotten the interaction strength of different modes by measuring the atomic absorption spectra of the guided resonant beam. The modes have been defined from the fibre output port and we assume that the modes at fibre output port giving the same modes at the waist of nanofiber. Due to the space limitation of the vacuum chamber, the modes at the waist of nanofiber cannot be directly defined by using conventional methods which have been used in free space experiments such as Rayleigh scattering and imaging. To fix this problem, we are trying to find a new way to determine the modes at the waist of fibre by measuring the absorption spectrum of guiding modes. Different modes at the waist can give the different absorption strengths. Recently, we have built a theoretical model to simulate the absorption spectrums for pure modes or mixed modes of the fibre. By combining with the experiment results, we could determine the mode conditions at the waist of nanofiber.
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| Strategy for Future Research Activity |
The research plan for FY2018 are as follows.
1)Implement four wave mixing(FWM) in the cold atom-fibre system. For further increasing optical depth, the atoms need to be trapped near the nanofiber surface by using two-colour dipole trap.
2)After obtaining FWM in the cold atom-fibre system, the orbital angular momentum (OAM) will be transferred between guiding modes and atom by means of the momentum conversion.
3)Measure the correlation function of production photons during FWM process to obtain the narrowband photon pair based on the atom-fibre system.
4)The photons with OAM will be stored to the cold atomic ensemble via electromagnetically induced transparency(EIT) process.
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| Causes of Carryover |
Consumables cost less than estimated.
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