2001 Fiscal Year Final Research Report Summary
Continous-Wave two-photon transition in photoretractive crystals
| Project/Area Number |
11450026
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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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 |
TOMITA Yasuo The University of Electro-Communications, Faculty of Electro-Communications, Professor, 電気通信学部, 教授 (50242342)
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| Project Period (FY) |
1999 – 2001
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| Keywords | photoretractive effect / holographic memories / two-phton transition / lithium niobate / two-photon recording / small polaron |
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| Research Abstract |
The purpose of this research is to investigate the dynamic properties of photorefractive (PR) gratings via the continuous-wave two-photon transition process in PR media and to demonstrate nonvolatile two-color holography with high figures of merit. The main results are listed below.
1. We have shown that as compared with nondoped lithium niobate (LN) crystals, two-color recording sensitivity S can be increased by two order of magnitude in an Er-doped LN crystal.
2. We have shown that figures of merit S and M/# can be increased up to those of near stoichiometric LN crystals when In ions are doped into congruently melted LN crystals.
3. Broadband UV-induced absorption is observed in Mg-doped near stoichiometric LN crystals. It is found that the cause for such induced absorption is attributed to the formation of O^- intermediate levels resulting from photo-excited holes trapped at O^<2-> sites. We also demonstrate quasi-nonvolatile two-color holographic recording by use of this novel phenomenon.
4. We demonstrate nonvolatile one-photon (near-infrared) holographic recording by use of LN codoped with In and Fe. Exchange of photo-excited electrons between bipolaron and Fe levels are considered to be a main cause for this novel phenomenon. We confirmed such a transport model by measuring near-infrared light-induced absorption changes in the UV and visible spectral regions.
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