**Diffraction efficiency**

Since the grating component can diffract only a limited spectral component, the diffraction efficiency, which is defined here as the ratio of the diffracted power by one grating component to the total power of the input probe beam, is much smaller than in the conventional monochromatic readout. This may be an unavoidable drawback of the PCR method.

#### **Intra- and Inter-page crosstalk noise**

Due to the wide spectral width of the probe beam, the hologram dimension *Lx* does not influence the intra-page crosstalk noise, and thus the input image area suffering from the intrapage crosstalk noise is slightly enlarged. On the other hand, the inter-page crosstalk noise is a crucial problem in the PCR method. The angular Bragg selectivity is greatly degraded, and thus, the storage capacity decreases by more than two orders of magnitude. However, this problem can be solved by using the selective detection method mentioned below.

#### **Selective detection method and the achievable storage capacity**

Taking advantage of the wavelength difference after the crystal rotation, we can detect the signal image alone, even if the noise images overlap with the target signal image. The storage capacity when employing the selective detection method reached 40 percent of the theoretical limit for the monochromatic case.

PCR is a unique and useful method for holographic memory systems. While other nondestructive readout methods have failed to achieve a high storage capacity, we theoretically proved that PCR, when used in combination with the selective detection method, enables us to achieve both nondestructive readout and a high storage capacity, simultaneously.
