HEP digital micromirror devices for precision solar spectroscopy

TL;DR

The study evaluates the TI High Efficiency Pixel (HEP) DLP801RE DMD as a reconfigurable spatial light modulator for precision solar spectroscopy and exoplanet transit simulations. Through benchtop photometry, optical modeling, window analyses, and synthetic transit tests, the authors demonstrate measurable optical throughput, diffraction behavior, and contrast (250:1 active; 400:1 unpowered) and validate the ability to recover transit signals down to the tens of ppm. They also show that spatial uniformity can be achieved via fiber scrambling and that a Mars-like 25 ppm transit depth is detectable with extensive phase-folding (≈150 folds), albeit with a discretization-limited effective depth of ≈40 ppm. The work identifies hardware electronic limitations as a key bottleneck and outlines future integration into a prototype solar instrument to enable configurable solar-region masking for simultaneous spectroscopy and imaging, with potential to improve RV precision toward Earth-like planets.

Abstract

We present the motivation and early tests for a novel solar instrument that will harness the new High Efficiency Pixel (HEP) Texas Instruments DLP801RE Digital Micromirror Device (DMD) as a reconfigurable spatial light modulator. This design enables real-time, dynamic configuration of the field of view for targeted spectroscopy of magnetically active regions and full-disk observations. Optical efficiency was validated through simulations and laser testing. Destructive window removal allowed for detailed structural analysis, confirming the elimination of central vias present in previous models. We measured a contrast ratio of 250:1, currently limited by the evaluation board's duty cycle rather than the DMD itself. Furthermore, we successfully simulated artificial planetary transits, recovering depths ranging from gas giants to a 40 ppm rocky planet transit. These results demonstrate the HEP DMD's potential for high-precision solar and exoplanetary science applications.

Figures (11)

• Figure 1: Illustrative graphic showing the high efficiency pixel digital micromirror device from Texas Instruments. (left) Image of DMD with Penn State Logo. (right) SEM of HEP DMD surface showing the removal of the vias leading to a larger fill factor.
• Figure 2: Thorlabs stabilized QTH SLS201L shows high photometric stability over 60 hours.
• Figure 3: Schematic of the DMD optical bench setup. The light from the Thorlabs QTH lamp is coupled into a circular to octagonal optical fiber which is then projected onto the DMD using Lens 1. The DMD directs a portion of light by 29 degrees to Lens 2 where the light is focused into a Thorlabs integrating sphere.
• Figure 4:
• Figure 5: Window transmission curves for common windows on Texas Instruments DMDsTI_window. The Corning Eagle XG VIS is used on the HEP DMDs.