Why metastable state is necessary for laser action?

In a three-level laser, the material is first excited to a short-lived high-energy state that spontaneously drops to a somewhat lower-energy state with an unusually long lifetime, called a metastable state. The metastable state is important because it traps and holds the excitation energy, building up a…

What is the time for electrons to stay in metastable state in laser?

The average lifetime before spontaneous emission occurs for a metastable state is on the order of a microsecond to a millisecond, quite a lengthy period of time on the atomic timescale. With lifetimes this long, excited atoms and molecules can produce significant amounts of stimulated emission.

Why do electrons go back down to the ground state?

The electron absorbs the energy and jumps to a higher energy level. In the reverse process, emission, the electron returns to the ground state by releasing the extra energy it absorbed. The result of this absorption was an atom in an excited state. The excited state atom eventually returns to the ground state.

Why does metastable state exist?

In a triplet, the unpaired excited electron has the same spin orientation as the unpaired ground electron, so it has to spin flip to get back down. This has a very low probability of occurring which makes the triplet state of let’s say neon, for instance, metastable.

What are metastable states in laser?

Metastable state is an excited state of an atom or other system with a longer lifetime than the other excited states. However, it has a shorter lifetime than the stable ground state. Atoms in the metastable state remain excited for a considerable time in the order of 10-6 to 10-3.

Why do electrons want to go to the ground?

Grounding: In Your Home Each of the electrical fixtures in your home is grounded as a safety measure. The ground wire in an electric outlet is a safety valve; any undesired electricity (positively charged energy) flows to the negatively charged ground, where it wants to go.

What is metastable electron state?

metastable state, in physics and chemistry, particular excited state of an atom, nucleus, or other system that has a longer lifetime than the ordinary excited states and that generally has a shorter lifetime than the lowest, often stable, energy state, called the ground state.

Where do electrons go in grounding?

Electrons do not “go to ground” necessarily. Electrons are negative and so they go to the positive charge of the supply. And they usually do this first passing through the load, or device doing the work. Most devices by convention have positive power supplies, so the ground is connected to the negative side.

What is the metastable state of a laser?

1. “Metastable” state just means a state where the electron is going to stay for a long time. By far the easiest way to make a laser is to use a metastable state for the upper laser level. Here’s why.

What is a metastable state?

“Metastable” state just means a state where the electron is going to stay for a long time. By far the easiest way to make a laser is to use a metastable state for the upper laser level. Here’s why. To make a laser you need a massive population in your excited state–more than half the atoms (say it’s atoms)…

What is the energy level structure of a metastable system?

The energy level structure is similar to that in the three-level system, except that after the atoms drop from the highest level to the metastable upper state, they do not drop all the way to the ground state in a single step.

Why does laser light weaken as it approaches the ground state?

If more than half of the atoms are in the ground state, the photon is more likely to encounter an atom that will absorb it, and less likely to encounter an atom that it can trigger to emit. With absorption being more likely, the laser light weakens, or doesn’t start to begin with.