A Closer Look at Photons and Atom Population in Lasers
What is the number of photons per second emitted by a thermal source of light and a small gas laser at a wavelength of 500 nm? How can we calculate the fraction of atoms in the upper state of a He-Ne laser at 300 K?
Number of Photons per Second Calculation:
Fraction of Atoms in the Upper State Calculation:
In the He-Ne laser at 300 K, approximately 2.23 × 10^-31 fraction of atoms is in the upper state. This can be calculated using the Boltzmann distribution formula:
N2/N1 = exp(-ΔE / (k * T)), where N2/N1 is the ratio of atoms in the upper state to the lower state, ΔE is the energy difference between the states, k is the Boltzmann constant, and T is the temperature in Kelvin.
Given the energy difference ΔE between the two states at 633 nm as 3.141 × 10^-19 J, the calculation results in a fraction of atoms in the upper state in the He-Ne laser at 300 K as approximately 2.23 × 10^-31.