Difference Between Spontaneous and Stimulated Emission

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.

1. What do you mean by stimulated emission?
2. What is meant by spontaneous emission?
3. What is absorption spontaneous emission and stimulated emission?
4. Which is spontaneous emission process?
5. How does stimulated emission occur?
6. Why stimulated emission is used in laser?
7. How is spontaneous emission important for lasing?
8. Why is spontaneous emission incoherent?
9. What is stimulated absorption?
10. What is the unit for the coefficient of stimulated emission?
11. At what temperature are the rates of spontaneous and stimulated emission equal?
12. What is the principle of laser?

What do you mean by 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.

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.

What is absorption spontaneous emission and stimulated emission?

Absorption: An atom in a lower level absorbs a photon of frequency hν and moves to an upper level. Spontaneous emission: An atom in an upper level can decay spontaneously to the lower level and emit a photon of frequency hν if the transition between E2 and E1 is radiative. This photon has a random direction and phase.

Which is spontaneous emission process?

Spontaneous emission is the process in which a quantum mechanical system (such as a molecule, an atom or a subatomic particle) transits from an excited energy state to a lower energy state (e.g., its ground state) and emits a quantized amount of energy in the form of a photon.

How does stimulated emission occur?

If a laser-active atom or ion is in an excited state (quantum-mechanical energy level), it may after some time spontaneously decay into a lower energy level, releasing energy in the form of a photon, emitted in a random spatial direction. This process is called spontaneous emission.

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.

How is spontaneous emission important for lasing?

Spontaneous emission is important during the start-up phase of a laser, e.g. when generating pulses with Q switching. It provides the first “seed” for the build-up of laser radiation in the laser resonator.

Why is spontaneous emission incoherent?

The radiation pattern produced by a large number of electrons is the linear superposition of the fields radiated by individual electrons. ... Because spontaneous radiation of this sort is statistical in nature, the fields do not have a well defined phase and the emission is termed incoherent.

What is stimulated absorption?

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.

What is the unit for the coefficient of stimulated emission?

What is the unit for the coefficient of stimulated emission? Explanation: For stimulated emission, the expression for the rate is B₂₁uN₂ where u stands for the energy density and N is the number of exited atoms. Therefore, the unit of B turns out to be J⁻¹ m³ s^-2.

At what temperature are the rates of spontaneous and stimulated emission equal?

For an emission of wavelength 5000 Angstrom, at what temperatures both spontaneous and stimulated emissions will be same? The spontaneous emission rate is 21 , which is independent of external radiation. 21 is called the Einstein coefficient for stimulated emission.

What is the principle of laser?

made with only two mirrors, one being flat and one being curved. Due to that curvature, a light beam with a suitable beam radius can circulate around the resonator without getting wider and wider each time. However, its optical power will decay, as some energy is lost in every resonator round trip.