Noise control

When performing an experiment to detect a physical phenomenon, it is very important that the measurement is "as clean as possible", reducing any contributions to the signal coming from external interferences and noise. As discussed in my post about the lock-in system fundamentals, lock-in detection is very effective to isolate even tiny (time-periodic) signal from …

Photonic bandstructure engineering

The Fabry-Perot cavity discussed in my previous post is only a simple example of a much wider class of resonators, which control the way light behaves inside the laser and how its beam propagates outside. Each laser resonator is characterized by a refractive index function n = n(x,y,z) which may vary over space and the boundary conditions, affecting the …

FEM electromagnetic simulations

The finite element method (FEM) is a numerical approach widely used in computational photonics to harness the complexity of Maxwell’s partial differential equations. FEM was originally invented to help civil and aerospace engineers with their structural design, but soon it was adopted in other fields of science and engineering due to its efficiency and versatility. …

Laser light design

Since the invention of laser technology in the late 1950s, laser light has become a crucial element of everyday life for billions of people. High-speed telecommunication, industrial production, healthcare, security and defense are just some of the fields where lasers have had a huge impact in the last decades. Figure 1: Detail of a Michelson interferometer …

Lock-in detection

INTRODUCTION A lock-in amplifier is a widespread detection system, used to extract the amplitude and the phase (R, θ) of a periodic signal even in presence of an intense background noise. Since its invention in the 1930s, the lock-in amplifier has become an indispensable tool in the fields of engineering, experimental and applied science. This …