Question

to find energy and momentum of photon of the co2 laser beam of wavelength 10.6nm​

Answer 1

Explanation:

The CO2 laser (carbon dioxide laser) is a molecular gas laser based on a gas mixture as the gain medium, which contains carbon dioxide (CO2), helium (He), nitrogen (N2), and possibly some hydrogen (H2), oxygen (O2), water vapor and/or xenon (Xe). Such a laser is electrically pumped via an electrical gas discharge, which can be operated with DC current, with AC current (e.g. 20–50 kHz) or in the radio frequency (RF) domain.

Although direct excitation of CO2 molecules into the upper laser level is possible, it has proven to be most efficient to use a resonant energy transfer from nitrogen molecules. Here, nitrogen molecules are excited by the electric discharge into a metastable vibrational level and transfer their excitation energy to the CO2 molecules when colliding with them. The exited CO2 molecules then largely participate in the laser transition. Helium serves both to depopulate the lower laser level and to remove the heat. Other constituents such as hydrogen or water vapor can help (particularly in sealed-tube lasers) to reoxidize carbon monoxide (CO, formed in the discharge) to carbon dioxide.

CO2 laser

Figure 1: Schematic setup of a sealed-tube carbon dioxide laser. The gas tube has Brewster windows and is water-cooled.

Spectral Lines

CO2 lasers typically emit at a wavelength of 10.6 μm, but there are dozens of other laser lines in the region of 9–11 μm (particularly at 9.6 μm). This is because two different vibrational states of the CO2 molecules can be used as the lower level, and for each vibrational state, there is a substantial number of rotational states, leading to many sub-levels. Dipole transitions (the only ones with a relatively high strength) are possible with ΔJ = ±1, where ΔJ = 1 (R branch) leads to higher photon energies (shorter wavelengths) and ΔJ = −1 (P branch) to lower energies:

Transitions of the stronger band, involving one of the two possible final vibrational levels, have their P branch around 10.6 μm, with P20 being the dominant transition, and the R branch around 10.2 μm.

Transitions of the other band have the P branch around 9.6 μm and the R branch around 9.3 μm.