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

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 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 have been able to be explained qualitatively by Hammett's substituent constant and the Taft's 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.