What produces pulses of light in lasers?

Answer 1

Stimulated emission paired with a population inversion is required to produce the pulses of light in lasers.

The procedure: After the gas in the laser's atoms are excited, the electrons naturally release photons and decelerate to lower energy levels.

A population inversion occurs when electrons gather in a state that is relatively slow to drop out of. As a result, there may be a greater number of electrons in this excited state than in the lower states.

Light can induce an electron to release a photon and decelerate from the excited state if its wavelength allows a photon to have an energy equal to the difference between this long-lived excited state and a lower state.

This is called stimulated emission; when an electron is made to fall to a lower state, it releases a photon that is identical to the photon that stimulated it in terms of frequency, phase, polarization, and direction of travel. As a result, two photons are now capable of stimulating other atoms, and when those atoms are stimulated, a large number of in phase photons with the same wavelength are released.

This is how coherent light is produced by lasers.

A photon striking an atom at the correct energy (energy equal to the difference between the excited and lower states) has two possible outcomes: it can either stimulate emission or be absorbed (stimulated absorption), with the likelihood of absorption being equal to that of stimulating emission.

Consequently,

The number of electrons in the excited state determines stimulated emission, while the number of electrons in the lower state determines stimulated absorption.

We would run out of photons if there were more electrons in the lower state, which would cause stimulated absorption to occur more frequently than stimulated emission. Therefore, a population inversion is required.

In case you're wondering, the probability of a spontaneous emission and stimulated emission/absorption are represented by the Einstien A and B coefficients, respectively.

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Answer 2

Pulses of light in lasers are produced through a process called stimulated emission.

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Answer from HIX Tutor

When evaluating a one-sided limit, you need to be careful when a quantity is approaching zero since its sign is different depending on which way it is approaching zero from. Let us look at some examples.

When evaluating a one-sided limit, you need to be careful when a quantity is approaching zero since its sign is different depending on which way it is approaching zero from. Let us look at some examples.

When evaluating a one-sided limit, you need to be careful when a quantity is approaching zero since its sign is different depending on which way it is approaching zero from. Let us look at some examples.

When evaluating a one-sided limit, you need to be careful when a quantity is approaching zero since its sign is different depending on which way it is approaching zero from. Let us look at some examples.

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