1987 Fiscal Year Final Research Report Summary
Femtosecond Photon Echose by using Incoherent Light
| Project/Area Number |
61460039
|
|---|
| Research Category |
Grant-in-Aid for General Scientific Research (B)
|
| Allocation Type | Single-year Grants |
|---|
| Research Field |
物理学一般
|
|---|
| Research Institution | University of Tsukuba |
|---|
Principal Investigator |
NAKATSUKA Hiroki Institute of Applied Physics Associate Professor, 物理工学系, 助教授 (10111915)
|
|---|
| Co-Investigator(Kenkyū-buntansha) |
INOUE Masahiro Institute of Applied Physics Associate Professor, 物理工学系, 助教授 (00013532)
ONARI Seinosuke Institute of Applied Physics Associate Professor, 物理工学系, 助教授 (70015824)
|
|---|
| Project Period (FY) |
1986 – 1987
|
| Keywords | Ultrafast relaxation / Phase relaxation / Photon echo / Incoherent light Homogeneous broadening / Inhomogeneous broadening / 不均一拡がり / パーシステントホールバーニング |
|---|
| Research Abstract |
Photon echoes are the optical analogue of spin echoes and are usually described by a model of two-level atomic system. Many experiments so far have been explained in this framework. The phase relaxation times T_2 of condensed matter like solid and liquid are generally very short even at very low temperatures and often fall in the picosecond or femtosecond region. By the recent progress in the technology of ultra-short pulse lasers, the photon echo experiments in a material with su ch a short T_2 have become possible. Even without ultra-short pulses, picosecond or femtosecond photon echo experiments are now available by using temporally-incoherent excitation light.
We made a photon echo experiment in cresyl violet in polyvinyl alcohol by using temporally- incoherent nanosecond laser pulses, and found that the echo decay curve at 10 K is made of two components, one is a sharp peak which decays very rapidly, and the other is a slowly decaying wing at the tail. This double structure agrees with the shape of the well-known (non)photo- chemical persistent hole in this material. We believe that the sharp peak in the echo decay curve is due to the phonon-sideband transition and the wing at the tail originates from the zero-phonon transition. The appearance of the phonon-sideband in the hole implies that the guest molecule (cresyl violet) cannot be considered as a simple two-level system, and the phonon-dressed molecule should rather be taken as a multi-ievel system. We applied a multi-level system model to photon echoes, and verified that both the photon echo decay-curve and the persistent hole spectrum can be explained by using this model.
|
