An optical memory is a type of computer memory that uses light to store and retrieve data. It is a non-volatile form of storage, meaning it does not need power to maintain the stored information. Optical memories are often used in applications where high capacity and fast access times are required, such as in Blu-ray discs and HD DVDs.
Optical memories work by encoding data onto a reflective surface using an optical beam. The data is retrieved by shining another beam onto the surface and reading the reflected light. The bits are stored as changes in reflectivity, which can be either on or off (binary 1 or 0). By varying the intensity, phase, or polarization of the beams, more than one bit can be stored per reflection.
One advantage of optical memories is that they can store large amounts of data in a small space. For example, a DVD can hold 4.7 GB of data on a disc with an diameter of only 12 cm. Additionally, optical memories are not susceptible to electromagnetic interference (EMI), which means they can be used in environments where electronic devices would be disrupted.
Optical memories have several disadvantages as well. One is that they require special equipment to read and write data, which makes them more expensive than other types of storage such as hard drives. Additionally, optical memories are more fragile than other types of storage and can be damaged if exposed to physical shock or heat extremes. Finally, because data is encoded onto a surface using an optical beam, there is a limit to how densely the bits can be packed together; this limits the maximum capacity of an optical memory device