A carbon dioxide (CO2) laser is a type of gas laser that operates in the infrared region of the electromagnetic spectrum. It is widely used in various medical, industrial, scientific, and military industries. Here is a brief overview of the construction, working principle, and energy diagram of a CO2 laser:
Construction: The CO2 laser consists of a gas-filled discharge tube, two mirrors, and an electrical power supply. The discharge tube is made of glass or metal and is filled with a mixture of CO2, nitrogen, and helium gases. The two mirrors are placed at either end of the tube, with one mirror being fully reflective and the other being partially reflective.
Working Principle: When a high-voltage electric current is applied to the gas mixture inside the tube, it ionizes the gas, causing it to emit light. This light bounces back and forth between the mirrors, causing it to become amplified as it passes through the gas mixture. As the light energy increases, more and more gas molecules become excited until they reach a state of high energy. When these excited molecules return to their lower energy state, they emit photons, which add to the amplified light energy in the tube.
Energy states of CO2 molecules.
A carbon dioxide molecule has a carbon atom at the center with two oxygen atoms attached, one on both sides. Such a molecule exhibits three independent modes of vibrations. They are
a) Symmetric stretching mode.
b) Bending mode
c) Asymmetric stretching mode.
Energy Diagram: The CO2 laser's energy diagram shows how the laser's energy levels work. It is a four-level laser system, meaning that the laser operates by exciting the CO2 molecules to higher energy levels and then causing them to release that energy in the form of photons. The energy levels of the CO2 molecules are shown on a vertical axis, and the corresponding wavelengths of light are shown on a horizontal axis.
The first energy level, the ground state, is the lowest energy level of the CO2 molecule. When an electric current is applied to the gas mixture, it causes electrons to move from the ground state to higher energy levels, creating a population inversion. The second energy level is the excited state, which is higher than the ground state. As the electrons move back to the ground state, they emit photons, which are the laser's output. The third energy level is the metastable state, which is a longer-lived excited state that can produce more photons before returning to the ground state. The fourth energy level is the ionization state, which is the highest energy level of the CO2 molecule.
In summary, a CO2 laser uses a gas mixture of CO2, nitrogen, and helium in a discharge tube to create a population inversion and amplify light energy through the use of mirrors. The energy diagram of the CO2 molecule shows how the laser's energy levels work and how photons are produced as the electrons return to their lower energy states.
