Application of lasers in computer engineering
The main example of semiconductor lasers is the magnetic-optical drive.
MO drive is based on a combination of magnetic and optical storage principle. Information is recorded by laser beam and magnetic field, and read by a laser alone.
In the process of writing to the MO disk, the laser beam heats certain points on the disk, and under the influence of temperature, the polarity resistance, for the heated point, drops sharply, which allows the magnetic field to change the polarity of the point. After heating, the resistance increases again but the polarity of the heated point remains in accordance with the magnetic field applied to it at the time of heating. There are currently two cycles, the erasure cycle and the write cycle, in the existing MO storage devices. In the process of erasing, the magnetic field has the same polarity corresponding to binary zeros. The laser beam heats the entire area erased and thus writes a sequence of zeros to the disk. In the recording cycle, the polarity of the magnetic field changes to the opposite, corresponding to the binary unit. In this cycle, the laser beam is switched on only in the areas which should contain binary units and leaving the areas with binary zeros unchanged.
In the process of reading from the MO disk uses the Kerr effect, which is to change the polarization plane of the reflected laser beam, depending on the direction of the magnetic field of the reflecting element. The reflective element in this case is a magnetized point recording on the surface of the disk corresponding to one bit of information. When reading, a laser beam of low intensity is used, which does not lead to the heating of the reading area, thus, when reading stored information is not destroyed.
This method, unlike that used in optical disks, deforms the surface of the disk and allows re-recording without additional equipment. This method also has the advantage over traditional magnetic recording in terms of reliability. Since the magnetization of the disk regions is possible only under the action of high temperature, the probability of accidental magnetization is very low, unlike traditional magnetic recording, which can be caused by accidental magnetic fields.
The scope of MO drives is determined by its high reliability, volume, and variability characteristics. MO disk is required for tasks requiring large disk volume, such tasks as CAD, image processing. However, the slow speed of access to the data makes it impossible to use MO disks for tasks with critical reactivity of systems. Therefore, the use of MO disks in such tasks is to store temporary or backup information on them. For MO disks, it is a very good use to back up your hard drives or databases. Unlike traditionally used streamers for this purpose, storing backup information on the MO disks significantly increases the speed of data recovery after failure. This is because the MO drives are random access devices, allowing only the data to be recovered in the event of a failure. In addition, with this recovery method, there is no need to completely shut down the system until the data is completely restored. These advantages, combined with the high reliability of information storage, make the use of MO disks in backup a cost-effective, albeit more expensive, solution than streamer.