The goal of this project is to produce a device, which will be able to modulate the polarization of light, such as a laser beam, with a software-defined waveform.
This device will provide a powerful and versatile tool to perform a broad spectrum of measurements (e.g. polarimetry, ellipsometry, etc.) with with much higher precision compared to conventional methods. This enhancement of precision can be achieved, when combining the optical modulator with phase- and frequency-sensitive detectors, such as lock-in amplifiers, which can extract the relevant information even from extremely noisy measurement data.
Since this design will be Open-Source Hardware and Free Software, researchers of various disciplines (e.g. optics, chemistry, biology, etc.) in laboratories all over the world, especially where the research budgets are small, can benefit from this project. Since it can serve as a low-budget solution, laboratories, that do have the people to build things, but not the budget to buy expensive equipment, will get access to this technology.
Furthermore, the nature of Open-Source Hardware enables students, researchers, professionals or makers to innovate on top of this project, and develop customized versions and derivatives, specially adapted to a specific need.
A Wi-Fi connected single-board computer, such as the Raspberry Pi, serves a browser-based graphical user interface for the web app that controls a stack of two TAPAS SDIs, whereas each TAPAS SDIs provides a synchronized software-defined current waveform, which will be fed into two solenoid electromagnet coils, as shown in Figure 1. A crystal with large Verdet constant, such as terbium gallium garnet, is placed in the cores of the solenoid to provide the optical modulation, which corresponds to the current waveform as defined by the user within the GUI.
As a simple example application, the solenoid with the crystal inside is placed inside the optical path of a polarimeter setup, as shown in Figure 2.
However, for the full measurement of the polarization of an unknown light source, such as the light of a star or the light emitted during a physical or chemical process, two solenoids with crystals with 45° rotation with respect to each other are placed before a linear polarizer with polarization direction of 22.5° the crystal is placed inside the optical path of a polarimeter setup, as shown in Figure 3.
This idea submission is among the finalists and will be presented at the CKI Conference in Erlangen.