A laser diode of power 5.0 mW is focused in air to a circular spot of diameter 0.80 mm.

PHYSICS · Multi-part · Fermi University Physics · Optics & Photonics · Wave propagation and light in media · Wave propagation and light in media

Optics and Photonics, Ch Light as an electromagnetic wave in matter

Problem

A laser diode of power 5.0 mW is focused in air to a circular spot of diameter 0.80 mm. ((a)) Find the irradiance

I

, then

E_0

and

B_0

. ((b)) Light of vacuum wavelength 480 nm from the same diode enters a sapphire window of refractive index

n = 1.77

. Find its wavelength, speed and wavenumber inside the sapphire. ((c)) A dye cell has absorption coefficient

\alpha = 2.3

^{-1}

at 480 nm. What fraction of the irradiance is transmitted through 5.0 mm of the dye? ((d)) Fused silica follows

n = 1.4508 + 3465\ \mathrm{nm}^2/\lambda^2

. Find its group index at

\lambda = 589

nm.