Question

The length of a laser tube is 150 mm and the gain factor of the laser material is 0.0005/cm. If one of the cavity mirrors reflects 100% light that is incident on it, what is the reflectance of other cavity mirror?
90%
95%
97 %
98.5%​

Answer 1

Hope you get a correct answer.

Answer 2

Given:

The length of the laser tube$=150\ mm$

gain factor$=0.0005 \ cm$

one cavity mirror reflects $100\%$ light

To Find:

The Reflectance of the other cavity mirror

Solution:

The relation is given by

$\gamma \geq \dfrac{1}{2L} ln\dfrac{1}{r_{1}r_{2} }\\r_{2}=\dfrac{1}{r_{1}e^{2L\gamma} }\\=\dfrac{1}{1\times e^{2\times15\times0.0005} }\\=0.985$

This means the other mirror should have a reflectance of $98.5\%$