Novel Nondestructive Readout Methods For Near-field Optical Recording with Large Refractive Index Modulation in Amorphous Diarylethene Layer

Abstract

Novel nondestructive readout methods for near-field optical recording has been demonstrated with an amorphous photochromic film. Large refractive index change of an amorphous photochromic layer of 1,2-bis(5-(2,4-diphenylphenyl)-2,4-dimethyl-3-thienyl) perfluorocyclopentene induced by the photochromic reactions is detected by the use of a guided-wave mode and a substrate radiation mode with near-IR laser light. The modulation amplitude in the reflected light intensity before and after the photo-bleaching reaction was as high as 20%.

Photochromism of Diarylethene Molecules and Crystals: Memories, Switches, and Actuators

“…Near-field optical recording with nondestructive readout capability was demonstrated using the amorphous films. 414 …”

“…3D recording, hologram recording, and waveguide-type switching devices based on refractive index changes of diaryl­ethenes have been reported. ,− The refractive index changes can be used for nondestructive readout, because the changes can be detected by light longer than the absorption region of the closed-ring isomers (see section ). The refractive index changes of diarylethene-dispersed polymer films are, however, relatively small.…”

“…Upon alternate irradiation with UV and visible light, the refractive index of the amorphous films of compound 138 was modulated between 1.617 and 1.645 at 817 nm, where both isomers have no absorption. Near-field optical recording with nondestructive readout capability was demonstrated using the amorphous films …”

Photoreversible refractive index change of [2.2]metacyclophan-1-ene in PMMA film

“…The Dn value of the Schiff base of dithienylethene in a PMMA film was reported to be 0.016 at 800 nm [10]. To increase the Dn values of the films, amorphous films of diarylethene have been prepared because these films [14][15][16][17]. For example, the Dn value of an amorphous film of diarylethene containing 2,4-diphenylphenyl substituents was found to be 0.08 at 817 nm [17].…”

“…To increase the Dn values of the films, amorphous films of diarylethene have been prepared because these films [14][15][16][17]. For example, the Dn value of an amorphous film of diarylethene containing 2,4-diphenylphenyl substituents was found to be 0.08 at 817 nm [17]. The use of an amorphous film of the photochromic dye is effective in increasing the Dn value; however, it should be noted that a considerable amount of this expensive dye is required for this purpose.…”