Motomu Yoshimura

Photochemical hole burning of anthraquinone derivatives in acrylic polymers

Abstract We have investigated the photochemical hole-burning (PHB) reactions of anthraquinone derivatives such as 1,4-dihydroxyanthraquinone (DAQ) and 4-amino-2,6-bis(4-butylphenoxy)-1,3-dihydroxyanthraquinone (ABDAQ) in acrylic polymers such as poly-2-hydroxyethyl methacrylate (PHEMA) and polymethyl methacrylate (PMMA). In the DAQ/PHEMA system, more than 100 holes were produced over an 8 nm wavelength region. On the other hand, in the ABDAQ/PMMA system holes were observed for the first time but produced at a density of only 2 or 3 holes/nm. Side holes appeared at both higher and lower energy sides of the resonant hole in the ABDAQ/PMMA system. There are two requirements for dense multiple hole formation: (i) that adjacent holes can lie independently as close together as possible; (ii) the hole width should be as narrow as possible. The electronic absorption spectra of DAQ is shifted to the red by nearly 100 nm in PHEMA compared to PMMA.

Ultra-High Density Optical Memory by Photochemical Hole Burning (PHB) and Multi-Layered PHB System

We have shown a possibility to store data at more than 600x10 8 bits/cm 2, by forming a double-layered PHB system. This memory density is the highest one reported so far.

Electric field effect on the persistent hole burning of quinone derivatives

The capacity of optical memories can be enhanced by using extra dimensions to store the signals besides the spatial dimension. We have investigated the photochemical persistent hole burning (PHB) reaction in a series of quinone derivatives as the guest molecules. In wavelength dimension, we showed that 600 ultra-high multiple spectral holes can be recorded in a double layered system. To increase the multiplicity of spectral holes, we intended to use electric field as another dimension. We have investigated the influence of electric field effect (Stark effect) in the PHB reaction characteristics. We observed for the first time with the quinone derivative systems that the burnt holes were broadened and then diminished when the applied electric field was changed, and that they reappeared when the applied electric field was changed again to the initial value. Multiple hole formation in the electric field dimension and optical modulation by electric field were also achieved.

Photochemical Hole Burning of the Quinone Derivatives in Polymer Matrices

We have investigated the PHB reactions of a series of the quinone derivatives dispersed in the acrylic polymers. In this report, we will show the results about the guest concentration effect and the substituent effect of the guest and host molecules on the PHB quantum efficiency and the temperature feature of the hole in the each guest-host system.

Stark effect on persistent spectral hole burning and dipole moment characteristics of anthraquinone derivatives doped in polymers

Abstract We have investigated the Stark effect on the spectral hole characteristics in the photochemical hole burning reaction in systems of anthraquinone derivatives, such as 1,4-dihydroxyanthraquinone (DAQ) and 4-amino-2,6-bis(4-butylphenoxy)1,5-dihydroxyanthraquinone (ABDAQ) as guest molecules embedded in host polymers such as 2-hydroxyethyl methacrylate (PHEMA) or poly(vinyl butyral) (PVB). The hole broadening and refilling were observed by applying an external electric field to the samples. Thus, the dipole moment differences |Δ \ gm| of the guest molecules between the ground state and the excited state were estimated as follows: 0.38, 0.51 and 0.26 D in the DAQ/PHEMA, ABDAQ/PHEMA and ABDAQ/PVB systems, respectively. These material dependent characteristics of |Δ \ gm| have been able to be explained qualitatively by Hammetts substituent constant and the Tafts polar substituent constant. Furthermore, from the application view point, 5 × 5 multiple spectral holes could be formed in both the wavelength and the electric field dimensions at 4.2 K in the ABDAQ/PVB system. This result indicates that high-density data multiplexing can be achieved in both the wavelength and the electric field dimensions using the Stark effect on the spectral holes.

Hole multiplexing in quinone-derivative photochemical hole-burning systems

We have investigated hole-burning reactions of quinone derivatives in order to elucidate the substituent effects on hole multiplexing, the hole-formation wavelength range, and the electric-field effect. For dense multiple-hole formation, our investigation has proved that selecting the proper substituents and the proper combination of guest and host molecules is important. Consequently, in quinone-derivative systems, multiple-hole formations in wavelengths and in electric fields were achieved at 4.2 K.

Photochemical Hole Burning of Quinone Derivatives

Photochemical Hole Burning (PHB) has a potential storage density of more than 1011 bits/cm2 using the wavelength dimension. We have investigated increasing the number of holes by additional using the electric field. The holes were measured with high resolution double beam laser spectroscopy. Furthermore, we have demonstrated multiple hole formation using both dimensions, which shows the possibility of the formation of thousands of multiple hole.