Photon-echo interference effects are used to manipulate the amplitude and polarization of a single echo generated by the read pulse in a long-lived stimulated echo pulse sequence. Interference is selective in time, frequency, and space, permitting modification of the multiplexed echo code.
The phenomenon of long-lived photon echo (LPE) has attracted much recent attention [1-6]. This interest stems from the possible application of this phenomenon in high-capacity optical memory devices (OMD) [7-8]. At present many fundamental problems crucial to the construction of an operating device are solved. The possibility of multiple information read out without refresh is shown theoretically [9] and experimentally [5,10]. Resonant media with storage times of the order of tens of hours and more have been investigated [4,5].Nevertheless, up to now it has not been clear whether it is possible to selectively erase information in an arbitrary memory cell of OMD. It was pointed out for the first time in Ref. [ 11] that it is in principle possible to erase information with random access using LPE signal suppression. We investigate the effect of LPE signal suppression in this work in more detail, and propose a simple technique for random access information erasing.
We describe a new approach to develop a high-speed, high-density random access cache memory. This new technique is based on a novel approach using, in essence, a hybrid of the time domain stimulated echo (SE) concept and the frequency domain scheme. It has been demonstrated that the rare-earth doped crystals, can at low temperatures store large amounts of information for up to 24 hours using SE. The basic approach we have developed is the partitioning of the absorption frequency domain into smaller bins, so that each frequency bin stores a smaller portion of information independently. The bins are distinguishable by their different absorption frequencies and they are accessed by changing the laser frequency (color). However, information is still stored and retrieved using the time-domain pulse sequency used in SE. Specifically, with the laser frequency set at the particular absorption of a frequency bin, the laser is externally modulated by an acousto-optic modulator to produce amplitude modulated pulses representing the digital data, the write pulse, and the read pulse, during the write and retrieve operation, respectively. The advantages of this approach are that memory can be stored in space, time, and frequency domain, allowing us to tailor a flexible memory architecture to match those of the computational processor.