Characterisation of long M-state lifetime bacteriorhodopsin thin films for optical cache memory

Changhai Wang, Mark Bacon, Ajoy K. Kar, Brian S. Wherrett, Robert L. Baxter

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6 Citations (Scopus)


We report the optical characterisation of bacteriorhodopsin (BR) films of long intermediate-state lifetimes. The M-state lifetime is extended from 10 ms for the native BR protein to ~20 minutes for our BR films, by chemical and physical modifications of the material. Optical cache memory characteristics of thin films are studied in excite-probe experiments in which nanosecond-duration pulses are used to excite a BR film and cw monochromatic light used to monitor the transmission dynamics. The memory read-time is found to vary significantly with the probe wavelength; it is of the order of milliseconds at 633 nm and of the order of 100 µs for probe wavelengths of 600 nm and below. The memory erase-time is ~50µs. Contrast ratios and insertion losses are measured at different probe wavelengths, with a maximum contrast ratio following nanosecond excitation of ~3:1 obtained in the peak absorption region of the B-state (~570 nm), at an excitation fluence of 30 mJcm-2. The implications of these results for the application of BR films as optical cache memory devices are discussed.

Original languageEnglish
Pages (from-to)439-443
Number of pages5
JournalJapanese Journal of Applied Physics, Part 1: Regular Papers and Short Notes and Review Papers
Issue number1 B
Publication statusPublished - 1997


  • Bacteriorhodopsin
  • Nonlinear optics
  • Optical materials
  • Optical memory


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