Limitation of a wedged etalon for high-resolution linewidth measurements.

The finesse of a wedged etalon is calculated numerically and is found to be approximately half that of a Fabry–Perot etalon. The calculated finesse agrees well with the experimental values obtained by using pulsed and cw CO2 lasers. It is also concluded that the wedged etalons may not be used for high-resolution linewidth measurements.