Junko Ishi

Resonant third-order optical nonlinearity in the layered perovskite-type material (C6H13NH3)2PbI4

Abstract The third-order nonlinear optical susceptibility, χ (3) (− ω ; ω , − ω , ω ), of the layered perovskite-type material (C 6 H 13 NH 3 ) 2 PbI 4 is measured by a transient four-wave mixing technique using a 200-fs-pulse laser source. The maximum … χ (3) … value is 1.6 × 10 −6 esu at the lowest-exciton resonance at 8 K. Longitudinal and transverse relaxation times of the excitons are 7 ps and 0.2 ps, respectively.

Time-to-space conversion of Tbits/s optical pulses using a self-organized quantum-well material

We report a time-to-space conversion technique using a material which has a large χ(3)(≃10−6 esu) and a fast response time (<7 ps) at room temperature. The material is a self-organized quantum-well system consisting of inorganic well layers and organic barrier layers. We achieve a high conversion sensitivity even for nJ-order optical pulses. We demonstrate serial-to-parallel conversion of nJ-order Tbits/s signals at room temperature with conversion rates of 140 GHz.

All-optical serial-to-parallel conversion of T-bits/s signals using a four-wave-mixing process

We report a simple method of a serial-to-parallel conversion that does not use a Fourier-transform system. The method is based on directly picking up a narrow temporal range of the skewed input signal by using a nonlinear wave mixing with the reference pulse. We show theoretically that the pick-up method is less influenced by the relaxation times of the nonlinear material. We demonstrate our method experimentally using a self-organized quantum-well material, and confirm that T-bits/s pulses are clearly converted into spatial patterns with conversion rates of 140 GHz.

Third-Order Optical Nonlinearity Due to Excitons and Biexcitons in a Self-Organized Quantum-Well Material (C6H13NH3)2PbI4

Third-order optical nonlinearity around the exciton resonance in (C6H13NH3)2PbI4 was measured using time-integrated and spectrally-resolved four-wave-mixing (FWM) techniques. For excitation below the exciton resonance, biexciton contribution to the FWM signals was observed. The dephasing energy of the biexcitons was estimated to be larger than 10 meV.

Ultrafast spin relaxation of excitons in a self-organized quantum-well material

Summary form only given. Time-resolved photoluminescence and pump-probe spectroscopies have been employed to study the spin relaxation processes of excitons in bulk semiconductors and semiconductor quantum wells (QWs). Extensive studies have shown that the spin dynamics in QWs differs from that in the bulk. In spite of many studies on excitons with large Bohr-radius such as in GaAs-based QWs, studies on excitons with small Bohr-radius are lacking. Since spin relaxation greatly depends on the exchange interaction between electron and hole in the exciton, the spin dynamics is expected to change with the coupling strength between the electron and hole. Therefore, experiments for excitons with small Bohr-radius are desired for full understanding of spin phenomena in QWs.

Biexcitonic contribution to four-wave mixing in a self-organized quantum-well material

Coherent exciton-exciton interactions have been recognized to be very important in nonlinear optical responses of semiconductor nanostructures. Polarization dependent four-wave-mixing (FWM) techniques have been widely used to study exciton-exciton interactions and dephasing processes of excitons. In this paper, we have investigated the polarization dependence of degenerate and nondegenerate FWM signals and discussed the two-exciton states in (C/sub 6/H/sub 13/NH/sub 3/)/sub 2/PbI/sub 4/. This material is a self-organized quantum-well system, in which a two-dimensional network of corner-sharing octahedra is sandwiched between organic barrier layers of alkylammonium chains.

All-optical temporal-spatial conversion using a four-wave-mixing process in a self-organized quantum well material

Summary form only given.All optical temporal-spatial conversion techniques using a four-wave-mixing (FWM) process have been developed in the 1990s. The performance of these techniques is determined by the FWM mechanism. The authors demonstrated the serial-to-parallel conversion with large efficiency and fast response time using the excitonic /spl chi//sup (3)/ nonlinearity in ZnSe film. However, the performance was achieved only in low temperature (10 K), because the excitonic nonlinearity of the ZnSe film smears out in room temperature Here we report on serial-to-parallel conversion using a material that has large third order nonlinearity and fast response time in room temperature. The material is a self-organized quantum-well system consisting of inorganic well layers and organic barrier layers. We demonstrate serial-to-parallel conversion of Tbits/s signals with conversion rate of 100 GHz.