= Solution
A high-<finesse> <Fabry–Pérot etalon> obtains very narrow transmission peaks by summing many coherent round trips, allowing high resolving <power> with a compact optical path. It can transmit a substantial fraction of resonant <light> when coating absorption is small, and works well for precise relative line separations and narrow-line measurements. A <diffraction grating> may require many illuminated grooves to achieve the same resolving <power>.
The etalon's <free spectral range> is limited, and repeated orders cause ambiguity across a broad <optical spectrum>. It commonly needs scanning and an order-selecting <optical filter> or another dispersive element. Mirror alignment, flatness and illumination angle strongly affect peak positions and widths, and absorption lowers throughput. A <diffraction grating> instead separates a broad range of <wavelengths> spatially for simultaneous detection, although grating orders can also overlap. The preferred instrument depends on whether narrow-band precision or broad spectral coverage is the priority.
Back to article page
