Fully-digital low-frequency lock-in amplifier for photoluminescence measurements

Abstract

Lock-in amplifiers, used in several experimental physics applications, are instruments performing quadrature demodulation, which is useful when signals are affected by much noise. Generally, commercially-available lock-in amplifiers are very accurate, but expensive, especially if their operating range includes radiofrequencies. In many applications, high precision is not necessary for the measurements, but it is preferable to have low-cost, low-weight, compactness and a user-friendly graphical unit interface. In this paper, we describe a new fully-digital low-frequency lock-in amplifier developed at ENEA C.R. Frascati Laboratories for photoluminescence experiments based on an innovative low-cost architecture and processing algorithms. The hardware, firmware and software developed for the whole photoluminescence measurement set-up is presented. The present lock-in was first characterized with synthetic electrical sine wave signals and white noise. A dynamic reserve of 43 dB and a noise figure in the range of 25–44 dB were estimated. These results show compatibility with several measurement applications, such as photoluminescence, and the adequacy of the resolutions with respect to the hardware costs. Finally, preliminary results of photoluminescence measurements are presented.

OLIA: An open-source digital lock-in amplifier

“…In this paper we report a simple, yet versatile, digital lock-in amplifier (LIA) based on a microcontroller development board and a small number of inexpensive, analogue components. While there have been a few previous reports of microcontroller-based LIAs (Bengtsson, 2012;Hofmann et al, 2012;Kim, 2014;Wang et al, 2017;Harvie et al, 2021;Pollastrone et al, 2023), only a small number have been released on a fully open basis (with complete design files, build instructions and source-code), and few have sought to replicate the full range of functionality offered by highend commercial instruments. Our goal in releasing OLIA is to provide an inexpensive, easily upgraded, intermediate performance digital lock-in amplifier that is suitable for a wide range of physical measurements.…”