The signal-to-noise ratio (SNR) on the fluorescence readout of a near-field photochromic memory was theoretically studied. Under various conditions the shot-noise-limited SNR was analyzed. SNR by bright spot recording (BSR) that was better than that by dark spot recording (DSR) was obtained under the condition of low writing power or wide bandwidth. Under the condition of bandwidth W = 1 MHz and P_(write) = 10~(-8) W only BSR can attain sufficiently high SNR, and the SNR was greater by as much as 30 dB than that of DSR. It was concluded that BSR is a premising method for high-density near-field photochromic memory with a fluorescence readout.
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