New standard for high-temperature persistent-hole-burning molecular materials: aluminum phthalocyanine tetrasulphonate in buffered hyperquenched glassy films of water

Applications of persistent spectral hole burning to optical memory and processing technologies currently face a number of hurdles. Not the least important of these are efficient hole burning, high storage density in the frequency domain, resilience against destructive readout, and operation at high temperatures ($⩾77$ K). It is shown that aluminum phthalocyanine tetrasulphonate (APT) in buffered hyperquenched glassy water (HGW) is a material whose hole-burning properties exceed, in every category, those of previously studied molecular systems. Its attributes at 77 K include a frequency storage-density parameter (ratio of the inhomogeneous broadening to the homogeneous width of the zero-phonon line) of 125 ($\sim {10}^5$ at 5 K), a burn fluence as low as 1.5 mJ/cm² for production of a zero-phonon hole with a fractional depth of 0.1, and a quite impressive resilience against destructive readout from hole burning and light-induced hole filling. It was predicted, for APT in deuterated HGW, that $\sim {10}^8$ digital readouts could be executed before refresh was necessary. The mechanism for hole burning of APT in HGW is nonphotochemical, a one-photon process. The results argue against the notion that only two-photon gated hole-burning materials hold promise for memory/processing applications. Although HGW is not a practical host medium for devices, a biomolecular strategy for the design of materials that might be and that retain the exceptional hole-burning properties of APT in HGW is proposed. In this regard, the first demonstration of hole burning in Jello is presented.