The first lasers appeared several decades ago, and to this day this segment is being promoted by the largest companies. Developers are getting new features of the equipment, allowing users to use it more effectively in practice.
The solid-state ruby laser is not considered one of the most promising devices of this type, but for all its shortcomings, it still finds niches in operation.
General information
Ruby lasers belong to the category of solid-state devices. Compared to chemical and gas counterparts, they have a lower power. This is explained by the difference in the characteristics of the elements, due to which radiation is provided. For example, the same chemical lasers are capable of generating light fluxes with a power of hundreds of kilowatts. Among the features that distinguish the ruby laser are a high degree of monochromaticity, as well as coherence of radiation. In addition, some models provide an increased concentration of light energy in space, which is enough for thermonuclear fusion by heating the plasma with a beam.
As the name implies, inthe active medium of the laser is a ruby crystal, presented in the form of a cylinder. In this case, the ends of the rod are polished in a special way. In order for the ruby laser to provide the maximum possible radiation energy for it, the sides of the crystal are processed until a plane-parallel position is reached relative to each other. At the same time, the ends must be perpendicular to the axis of the element. In some cases, the ends, which act as mirrors in some way, are additionally covered with a dielectric film or a layer of silver.
Ruby laser device
The device includes a chamber with a resonator, as well as an energy source that excites the atoms of the crystal. A xenon flash lamp can be used as a flash activator. The light source is located along one axis of the resonator having a cylindrical shape. On the other axis is the ruby element. As a rule, rods with a length of 2-25 cm are used.
The resonator directs almost all the light from the lamp to the crystal. It should be noted that not all xenon lamps are able to operate at elevated temperatures, which are required for optical pumping of the crystal. For this reason, the ruby laser device, which includes xenon light sources, is designed for continuous operation, which is also called pulsed. As for the rod, it is usually made of artificial sapphire, which can be modified accordingly to meet the performance requirements forlaser.
Laser principle
When the device is activated by turning on the lamp, an inversion effect occurs with an increase in the level of chromium ions in the crystal, as a result of which an avalanche increase in the number of emitted photons begins. In this case, feedback is observed on the resonator, which is provided by mirror surfaces at the ends of the solid rod. This is how a narrowly directed flow is generated.
The pulse duration, as a rule, does not exceed 0.0001 s, which is shorter compared to the duration of a neon flash. The pulse energy of a ruby laser is 1 J. As in the case of gas devices, the principle of operation of a ruby laser is also based on the feedback effect. This means that the intensity of the light flux begins to be maintained by the mirrors interacting with the optical resonator.
Laser Modes
Most often, a laser with a ruby rod is used in the mode of formation of the mentioned pulses with a millisecond value. To achieve longer active times, the technologies increase the optical pumping energy. This is done through the use of powerful flash lamps. Since the pulse growth field, due to the time of formation of an electric charge in a flash lamp, is characterized by a flatness, the operation of the ruby laser starts with some delay at the moments when the number of active elements exceeds the threshold values.
Sometimes there are alsodisruption of impulse generation. Such phenomena are observed at certain intervals after a decrease in power indicators, that is, when the power potential drops below the threshold value. The ruby laser can theoretically operate in a continuous mode, but such operation requires the use of more powerful lamps in the design. Actually, in this case, developers are faced with the same problems as when creating gas lasers - the inexpediency of using an element base with enhanced characteristics and, as a result, limiting the capabilities of the device.
Views
The benefits of the feedback effect are most pronounced in lasers with non-resonant coupling. In such designs, a scattering element is additionally used, which makes it possible to radiate a continuous frequency spectrum. A Q-switched ruby laser is also used - its design includes two rods, cooled and uncooled. The temperature difference allows the formation of two laser beams, which are separated by wavelength into angstroms. These beams shine through a pulsed discharge, and the angle formed by their vectors differs by a small value.
Where is the ruby laser used?
Such lasers are characterized by a low efficiency, but they are thermally stable. These qualities determine the directions of practical use of lasers. Today they are used in the creation of holography, as well as in industries where it is required to perform operationspunching holes. Such devices are also used in welding operations. For example, in the manufacture of electronic systems for the technical support of satellite communications. The ruby laser has also found its place in medicine. The application of technology in this industry is again due to the possibility of high-precision processing. Such lasers are used as a replacement for sterile scalpels, allowing microsurgical operations.
Conclusion
A laser with a ruby active medium at one time became the first operating system of this type. But with the development of alternative devices with gas and chemical fillers, it became obvious that its performance has many disadvantages. And this is not to mention the fact that the ruby laser is one of the most difficult in terms of manufacturing. As its working properties increase, the requirements for the elements that make up the structure also increase. Accordingly, the cost of the device also increases. However, the development of ruby-crystal laser models has its own reasons, related, among other things, to the unique qualities of a solid-state active medium.
