oi The principle of a laser
(1) atomic basics.
There are only about 100 different atoms in the universe.Everything we see is a combination of these 100 or so atoms in a very finite way.The arrangement of these atoms determines the composition of a glass of water, a metal or a bubble in a soda bottle!An atom is a perpetual motion.They vibrate, move and rotate, and even the atoms that make up our seats are constantly moving.Solid is actually moving!Atoms have several different excitation states, in other words, they have different energies.If the atom is endowed with sufficient energy, it can ascend from the ground state energy level to the excited state energy level.The energy levels of the excited states depend on how much energy is given to atoms through heat energy, light energy, and electricity.
(2) the core principle of atoms forming lasers.
Think about the structure of the atom.Even with modern technology, we can't see the discrete orbitals of electrons, but it's helpful to think of these orbitals as atoms in different energy levels.In other words, if we heated the atoms, some of the electrons in the low-energy orbitals could be excited and jump to a higher energy orbit farther from the nucleus.Although this description is simple, it does reveal the core principle of atoms forming lasers.After the electron jumps to a higher energy orbit, it still has to go back to the ground state.In the process, electrons release energy in the form of photons (a light particle).You will find that atoms constantly release energy in the form of photons.For example, the heating element in the oven turns bright red, and the red one is the red photon emitted by the heat of the atoms.When you look at the images on the TV screen, you see that the phosphorus atoms are exposed to the different colors of light emitted by high-speed electrons.Any light-emitting object, including fluorescent lights, gas lamps and incandescent bulbs, is emitted by changing electron orbitals and releasing photons.
(3) the relationship between the laser and the atom.
A laser is a device that controls the release of photons emitted by excited atoms."Laser" is short for light amplification by stimulated emission of radiation (stimulated radiation light amplification).This name briefly describes how the laser works.Although there are many kinds of lasers, they have some basic characteristics.In the laser, the laser medium must be pumped to excite the atoms.Generally speaking, high intensity flashes or discharge can pump excited media, which can produce a large number of excited states (including high-energy electron atoms).The laser has to have a large number of excited atoms to operate efficiently.In general, atoms must be stimulated to rise to two or three energy levels above the ground state.This increases the degree of the inversion of the number of particles.The number inversion of a particle is the number of atoms in an excited state and the number of atoms in the ground state.When the laser medium is pumped, it includes a batch of atoms with excited electrons.Excited electrons have higher energy than low-grade electrons.Just like electrons can absorb a certain amount of energy to the excited state, electrons can release this energy.As shown in the figure below, electrons can release some of their energy as long as they transition to a lower level.The energy released is transformed into a photon (light energy) form.The emitted photon has a specific wavelength (color), which depends on the energy state of the electron when the photon is released.Two atoms with the same electron state release photons of the same wavelength.
(4) laser laser is very different from ordinary light.
It has the following characteristics: the emission of the laser is monochromatic.A laser contains light that has a specific wavelength (that is, a particular color).The wavelength of light is determined by the energy released by the electron back to the low energy orbit.The emitted laser has good coherence.The laser has a better structure, and each photon follows other photon movements.In other words, the waves of all photons are exactly the same.Laser has good directivity.The laser beam is compact, concentrated and highly energetic.Instead, the light from the flashlight scatters in multiple directions, with weak energy and low concentration.To achieve these three characteristics, you need to go through a process called stimulated emission.This phenomenon is unlikely to occur in a normal flashlight because its atoms are randomly emitted photons.When fired, the atom is an organized emission of photons.A photon emitted by an atom has a specific wavelength, which depends on the difference in energy between the excited state and the ground state.If the photon (with a certain energy and phase) encounters another atom, and the atom has an electron in the same excited state, it can trigger the excitation.The first photon can either excite or lead the atom to emit photons, and then emit photons (the photons emitted by the second atom) that vibrate at the same frequency and direction as the photon enters the photon.Another key component of the laser is a pair of mirror, located at opposite ends of the laser medium.The photon of a particular wavelength and phase is reflected back and forth between the laser medium through the reflection of the mirror at both ends.In the process, they will stimulate more electrons by high-energy orbit to low-energy track jumping, which emit more of the same wavelength and phase of photons, which will then have a "waterfall" effect, and then quickly gathered a large number of the same wavelength in laser and phase of the photons.A mirror on one side of the laser USES a "semi-reflective" coating, which means that it only reflects part of the light, while the other light can penetrate.The penetrating light is the laser.
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