Crossed-beam two-photon readout system for three-dimensional radiation dosimeters

Three-dimensional optical random access memory (3D ORAM) materials with enormous capacity and fast access speed have shown a great potential in overcoming limitations of access and storage capacity in current memory devices. As another useful development of this 3D ORAM, we have shown the application of 3D ORAM materials as a practical dosimeter. The local heating of the polymer matrix by the deposited energy of ionizing radiation is thought to contribute to the conversion of the fluorescent photochromic dye to a nonfluorescent form. The two-photon readout system is very useful in tracking the interactions of energy of ionizing radiation deposited in a polymer matrix. However, the polymer fracturing that has occurred during two-photon readout has been an obstacle in utilization of 3D ORAM materials as a dosimeter. In this work, we further evaluated the readout system using a high-energy variable attenuator in order to prevent polymer fracturing due to the strong absorption of the 1064 nm beam by the polymer matrix. Through adjustment of the 1064 nm beam intensity using this attenuator, two-photon excited fluorescence of anthracene-doped 3D ORAM materials could be obtained without polymer fracturing. As a result of this improved procedure, a highly spatially resolved fluorescence image of anthracene-doped 3D ORAM material could be observed with the two-photon readout system.