## 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:

### Paraxiality

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.