What is spontaneous and stimulated emission process?
Spontaneous emission takes place without interaction with other photons, and the direction and phase are random. Stimulated emission takes place when the excited electron interacts with another photon.
What is stimulated emission and absorption?
Stimulated emission (absorption) is a process, in which an incident electromagnetic field, comprising the energy of one photon, forces an atom in its excited (ground) state to oscillate and emit a second electromagnetic field, comprising the energy of one photon, that is in phase (anti-phase) with the incident field.
What is the relationship between b21 and b12?
What is the relationship between B21 and B12? Explanation: B21 is the coefficient for the stimulated emission while B12 is the coefficient for stimulated absorption. Both the processes are mutually reverse processes and their probabilities are equal. Therefore, B12 = B21.
What is meant by spontaneous emission?
If an atom is in an excited state, it may spontaneously decay into a lower energy level after some time, releasing energy in the form of a photon, which is emitted in a random direction. This process is called spontaneous emission.
How does stimulated emission occur?
Stimulated emission occurs when an atom or molecule in an energy level above the ground state interacts with a photon that has energy equal to that between the atom or molecule’s current energy level and a lower energy level.
What causes stimulated emission?
Stimulated emission is the process by which an incoming photon of a specific frequency can interact with an excited atomic electron (or other excited molecular state), causing it to drop to a lower energy level.
Why is stimulated emission used?
Stimulated emission can provide a physical mechanism for optical amplification. If an external source of energy stimulates more than 50% of the atoms in the ground state to transition into the excited state, then what is called a population inversion is created.
What are the important features of stimulated emission?
Stimulated emission of radiation generates monochromatic and coherent light with a determined wavelength. Absorption: When an atom of the active medium absorbs a photon, an electron jumps to an excited state. This process competes with the stimulated emission process.
What is stimulated absorption formula?
Stimulated Absorption is the starting point to achieve laser. It happens when a photon of light having energy E2 – E1 = hυ (as shown in the figure) is incident on an atom in the ground state, the atom in the ground state E1 may absorb the photon and jump to a higher energy state E2.
How is stimulated emission calculated?
The rate of stimulated emission processes for an excited atom can be calculated as the product of the so-called emission cross section and the photon flux density (number of photons per unit area and time).
Why stimulated emission is used in laser?
In laser action the stimulating emission triggers a chain reaction in which the radiation from one atom stimulates another in succession until all the excited atoms in the system have returned to normalcy. In doing so, coherent monochromatic light (light of a single wavelength) is emitted.
What happens stimulated absorption?
ii. Stimulated absorption occurs when a photon strikes an atom with just exactly the proper energy to induce an electronic transition between two energy states.
How is stimulated emission different from spontaneous emission?
The stimulated emission is not a natural process it is an artificial process. In stimulated emission, the electrons in the excited state need not wait for natural spontaneous emission to occur. An alternative method is used to stimulate excited electron to emit photons and fall back to ground state.
How is stimulated emission related to radiation absorption?
Stimulated emission.—If radiation passes through matter, the matter can be stimulated to emit radiation of the same frequency and direction as the initial radiation. This is the principle behind lasers, and it, too, adds to the intensity. Absorption.—Radiation can be absorbed by the matter.
Where does the spontaneous emission of photons occur?
In spontaneous emission, the electrons changing from one state (higher energy state) to another state (lower energy state) occurs naturally. So the photon emission also occurs naturally or spontaneously.
Which is a mechanism by which stimulated emission can dominate?
The mechanism by which stimulated emission can be made to dominate is to have more atoms in the excited state than in the lower energy state, so that emitted photons are more likely to stimulate emission than to be absorbed. Because this condition is the inverse of the normal equilibrium situation, it is termed a population inversion.