A distributed-feedback (DFB) diode laser emits a Lorentzian spectral line of full…

PHYSICS · Multi-part · Fermi University Physics · Optics & Photonics · Coherence and statistical optics · Coherence and statistical optics

What an Instrument Can See, Ch Temporal coherence: correlation, spectrum and the interferometer

Problem

A distributed-feedback (DFB) diode laser emits a Lorentzian spectral line of full width at half maximum

\Delta\nu = 2.0

MHz. Using the integral definition of coherence time applied to a Lorentzian lineshape, find ((a)) the coherence time

\tau_c

; ((b)) the coherence length

\ell_c

in vacuum, taking

c = 3.00\times10^8\ \mathrm{m\,s^{-1}}