2005 Fiscal Year Final Research Report Summary
Control of coherence length of a single photon emitted from a microcavity
| Project/Area Number |
16560032
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Applied optics/Quantum optical engineering
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| Research Institution | The University of Electro-Communications |
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Principal Investigator |
UJIHARA Kikuo The University of Electro-Communications, Faculty of Electro-Communications, Professor, 電気通信学部, 教授 (90017351)
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| Project Period (FY) |
2004 – 2005
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| Keywords | single photons / coherence length / Mach-Zhender interferometer / high Q microcavity / dye-microcavity system |
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| Research Abstract |
1.In order to obtain a single photon with a Fourier transform limit character, we have investigated a method wherein a planar microcavity with a high quality factor is employed so as to make the spectrum of the emitted photon is mostly determined by the narrow path band of the cavity. For this purpose, we have designed a planar microcavity with two high reflectivity mirrors of power reflectivity R=0.99999, which should yield a single photons of coherence length in the order of a cm. Actually fabricated mirrors had a power reflectivity R=0.99992, for which the expected photon coherence length was about 4mm.
2.With the above mirrors, we have constructed two planar microcavities : one contained a ethanol solution of dye Rhodamine6G with a concentration of 5×10^<-3> mol/L. Another contained a solution of concentration 5×10^<-4> mol/L For comparison we have also constructed a low Q planar microcavity utilizing mirrors of power reflectivity R=0.995 which contained a solution of 5×10^<-3> mol/
… More
L. We have examined the intensity of the fluorescence of these three microcavities under pulsed excitation by second harmonic light of a YAG laser. The intensities of the three microcavities lowered successively by about 1.5 order of magnitude in the above order. The characteristics were fairly reproduced by a four level laser model with ample number of emitting molecules. The excitation intensity range to obtain a single photon was determined.
3.In order to measure the coherence length of the single photon, we have constructed a Mach-Zhender interferometer containing a corner cube that could be scanned by a stepping motor with resolution about 40nm. The overall size of the interferometer was about 50cm×40cm. Because the coherence length of the emitted photon was expected in the range of mms, it was needed that the path lengths in the interferometer should coincide within a mm. Thus, we have used a modulated semiconductor laser that had a coherence length in the order of a few cm and, by a repeated measurement of the interference visibility, could determined the zero-path difference position of the corner cube with an accuracy in the range of a mm.
4.We have given a theoretical photon number distribution for the fluorescence in the above experiments.
5. We are at the stage where we can examine the coherence length of the emitted single photons. There we will need to construct a photon counting system that allows the measurement of the single photon wavefunction by use of the Mach-Zhender interferometer. Less
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Research Products
(4 results)
