Category Archives: coherent optics

the Fabry-Pérot resonator

Cal­cu­late the trans­mit­ted or reflect­ed inten­si­ty and phase for a Fab­ry-Pérot cav­i­ty. Both reflec­tiv­i­ties and res­onator loss­es are account­ed for. aver­age pho­ton life­time: round-trips res­onator finesse:


The pre­vi­ous post on the Gauss­ian beam not­ed that this beam is a solu­tion to the parax­i­al wave equa­tion and thus only accu­rate for small diver­gence angles. The lim­it giv­en in [1] was $w_0 \gt 2\lambda/\pi$ or $\theta \lt 0.5\mathrm{rad}$ or $\approx 29^\circ$. The Gauss­ian beam mod­el is of course not exact up to that […]

the Gaussian beam (interactive)

The Gauss­ian beam “is a con­ve­nient, wide­spread mod­el in laser optics.” [1] It is indeed con­ve­nient that such a math­e­mat­i­cal­ly rel­a­tive­ly sim­ple mod­el can describe the evo­lu­tion of laser light in free space so well. Giv­en the wave­length of the laser, it can be described by a sin­gle para­me­ter. This can be either the beam […]

homodyne versus heterodyne

The mer­its of homo­dyne ver­sus het­ero­dyne detec­tion is some­what of a crossover top­ic since it applies to both opti­cal com­mu­ni­ca­tion and inter­fer­om­e­try. In this post we will start by deriv­ing the detect­ed sig­nals for homo­dyne, het­ero­dyne and intra­dyne detec­tion.