Most readers are well aware of the concept of "laser", formed from the English "laser" (light amplification by stimulated emission of radiation). Lasers invented in the middle of the 20th century have thoroughly entered our life, even though their work in modern technology is often invisible to ordinary people. The main popularizer of the technology has become science fiction books and films, in which lasers have become an integral part of the equipment of the fighters of the future.
In reality, lasers have come a long way, being used mainly as reconnaissance and target designation means, and only now they should take their place as a weapon of the battlefield, possibly radically changing its appearance and the appearance of combat vehicles.
Less well known is the concept of a "maser" - an emitter of coherent electromagnetic waves in the centimeter range (microwaves), whose appearance preceded the creation of lasers. And very few people know that there is another type of sources of coherent radiation - "saser".
"Beam" of sound
The word "saser" is formed similarly to the word "laser" - Sound Amplification by Stimulated Emission of Radiation and denotes a generator of coherent sound waves of a certain frequency - an acoustic laser.
Do not confuse a saser with an "audio spotlight" - a technology for creating directional sound streams, as an example we can recall the development of Joseph Pompey from Massachusetts Institute of Technology "Audio Spotlight". In the audio spotlight "Audio Spotlight", a beam of waves is emitted in the ultrasonic range, which, interacting nonlinearly with air, increase their length to sound. The beam length of an audio projector can be up to 100 meters, however, the sound intensity in it decreases rapidly.
If in lasers there is a generation of light quanta - photons, then in sasers their role is played by phonons. Unlike a photon, a phonon is a quasiparticle introduced by the Soviet scientist Igor Tamm. Technically, a phonon is a quantum of vibrational motion of crystal atoms or a quantum of energy associated with a sound wave.
“In crystalline materials, atoms actively interact with each other, and it is difficult to consider such thermodynamic phenomena as vibrations of individual atoms in them - huge systems of trillions of interconnected linear differential equations are obtained, the analytical solution of which is impossible. The vibrations of the atoms of the crystal are replaced by the propagation of a system of sound waves in the substance, the quanta of which are phonons. The phonon belongs to the number of bosons and is described by the Bose - Einstein statistics. Phonons and their interaction with electrons play a fundamental role in modern concepts of the physics of superconductors, heat conduction processes, and scattering processes in solids."
The first sasers were developed in 2009-2010. Two groups of scientists presented methods of obtaining laser radiation - using a phonon laser on optical cavities and a phonon laser on electronic cascades.
A prototype of an optical resonator saser, designed by physicists from the California Institute of Technology (USA), uses a pair of silicon optical resonators in the form of tori with an outer diameter of about 63 micrometers and an inner diameter of 12, 5 and 8, 7 micrometers, into which a laser beam is fed. By changing the distance between the resonators, it is possible to adjust the frequency difference of these levels so that it corresponds to the acoustic resonance of the system, which results in the formation of laser radiation with a frequency of 21 megahertz. By changing the distance between the resonators, you can change the frequency of sound radiation.
Scientists from the University of Nottingham (Great Britain) have created a prototype of a saser on electronic cascades, in which sound passes through a superlattice containing alternating layers of gallium arsenide and aluminum semiconductors several atoms thick. Phonons accumulate like an avalanche under the influence of additional energy and are reflected many times inside the superlattice layers until they leave the structure in the form of saser radiation with a frequency of about 440 gigahertz.
Sasers are expected to revolutionize microelectronics and nanotechnology, comparable to that of lasers. The possibility of obtaining radiation with a frequency of the terahertz range will make it possible to use sasers for high-precision measurements, obtaining three-dimensional images of macro-, micro- and nanostructures, changing the optical and electrical properties of semiconductors at a high speed.
The applicability of sasers in the military field. Sensors
The format of the combat environment determines the choice of the type of sensors that are most effective in each specific case. In aviation, the main type of reconnaissance equipment is radar stations (radars), using millimeter, centimeter, decimeter and even meter (for ground-based radar) wavelengths. The ground battlefield requires increased resolution for accurate target identification, which can only be achieved by means of reconnaissance in the optical range. Of course, radars are also used in ground technology, as well as optical reconnaissance means are used in aviation, but still, the bias in favor of the priority use of a certain wavelength range, depending on the type of combat environment format, is quite obvious.
The physical properties of water significantly limit the propagation range of most electromagnetic waves in the optical and radar ranges, while water provides significantly better conditions for the passage of sound waves, which led to their use for reconnaissance and guidance of weapons of submarines (PL) and surface ships (NK) in the case of if the latter are fighting an underwater enemy. Accordingly, hydroacoustic complexes (SAC) became the main means of reconnaissance of submarines.
SACs can be used in both active and passive modes. In active mode, the SAC emits a modulated sound signal, and receives a signal reflected from an enemy submarine. The problem is that the enemy is able to detect the signal from the SAC much further than the SAC itself will catch the reflected signal.
In the passive mode, the SAC "listens" to the noises emanating from the mechanisms of an enemy submarine or ship, and detects and classifies targets based on their analysis. The disadvantage of the passive mode is that the noise of the latest submarines is constantly decreasing, and becomes comparable to the background noise of the sea. As a result, the detection range of enemy submarines is significantly reduced.
SAC antennas are phased discrete arrays of complex shape, consisting of several thousand piezoceramic or fiber-optic transducers that provide acoustic signals.
Figuratively speaking, modern SACs can be compared with radars with passive phased antenna arrays (PFAR) used in military aviation.
It can be assumed that the appearance of sasers will make it possible to create promising SACs, which can conditionally be compared with radars with active phased antenna arrays (AFAR), which have become a hallmark of the latest combat aircraft
In this case, the algorithm for the operation of promising SACs based on Saser emitters in the active mode can be compared with the operation of aviation radars with AFAR: it will be possible to generate a signal with a narrow directivity pattern, ensure a dip in the directivity pattern to the jammer and self-jamming.
Perhaps, the construction of three-dimensional acoustic holograms of objects will be realized, which can be transformed to obtain an image and even the internal structure of the object under study, which is extremely important for its identification. The possibility of the formation of directional radiation will make it difficult for the enemy to detect a sound source when the SAC is in active mode to detect natural and artificial obstacles when a submarine moves in shallow water, detecting sea mines.
It must be understood that the aquatic environment will significantly more influence the "sound beam" compared to the way the atmosphere affects laser radiation, which will require the development of high-performance laser guidance and correction systems, and in any case it will not be like a "laser beam" - the divergence of the laser radiation will be much greater.
The applicability of sasers in the military field. Weapon
Despite the fact that lasers appeared in the middle of the last century, their use as weapons providing physical destruction of targets is becoming a reality only now. It can be assumed that the same fate awaits the sasers. At least, "sound cannons" similar to those depicted in the computer game "Command & Conquer" will have to wait for a very, very long time (if the creation of such is at all possible).
Drawing an analogy with lasers, it can be assumed that on the basis of sasers, in the future, self-defense complexes can be created, similar in concept to the Russian airborne defense system L-370 "Vitebsk" ("President-S"), designed to counter missiles aimed at an aircraft with infrared homing heads using an optical-electronic suppression station (OECS), which includes laser emitters that blind the missile homing head.
In turn, the onboard self-defense system of submarines based on Saser emitters can be used to counter enemy torpedo and mine weapons with acoustic guidance.
conclusions
The use of sasers as means of reconnaissance and armament of promising submarines is most likely at least a medium-term, or even a distant prospect. Nevertheless, the foundations of this perspective need to be formed now, creating a groundwork for future developers of promising military equipment.
In the 20th century, lasers have become an integral part of modern reconnaissance and target designation systems. At the turn of the 20th and 21st centuries, a fighter without an AFAR radar can no longer be considered the pinnacle of technological progress and will be inferior to its competitors with an AFAR radar.
In the next decade, combat lasers will radically change the face of the battlefield on land, water and in the air. It is possible that sasers will have no less influence on the appearance of the underwater battlefield in the middle - end of the 21st century.
