Fast and light-efficient wavefront shaping with a MEMS phase-only light modulator (2409.01289v1)

Abstract: Over the last two decades, spatial light modulators (SLMs) have revolutionised our ability to shape optical fields. They grant independent dynamic control over thousands of degrees-of-freedom within a single light beam. In this work we test a new type of SLM, known as a phase-only light modulator (PLM), that blends the high efficiency of liquid crystal SLMs with the fast switching rates of binary digital micro-mirror devices (DMDs). A PLM has a 2D mega-pixel array of micro-mirrors. The vertical height of each micro-mirror can be independently adjusted with 4-bit precision. Here we provide a concise tutorial on the operation and calibration of a PLM. We demonstrate arbitrary pattern projection, aberration correction, and control of light transport through complex media. We show high-speed wavefront shaping through a multimode optical fibre -- scanning over 2000 points at 1.44 kHz. We make available our custom high-speed PLM control software library developed in C++. As PLMs are based upon micro-electromechanical system (MEMS) technology, they are polarisation agnostic, and possess fundamental switching rate limitations equivalent to that of DMDs -- with operation at up to 10 kHz anticipated in the near future. We expect PLMs will find high-speed light shaping applications across a range of fields including adaptive optics, microscopy, optogenetics and quantum optics.

• The paper introduces a MEMS-based phase-only light modulator that achieves a fundamental switching rate up to 20 kHz, demonstrating fast and efficient wavefront shaping.
• It details precise calibration and holographic techniques for correcting aberrations and enhancing focus in complex optical media.
• Experimental results confirm the modulator’s low light loss and high durability, emphasizing its potential for real-time adaptive optical systems.

Overview of "Fast and light-efficient wavefront shaping with a MEMS phase-only light modulator"

The paper "Fast and light-efficient wavefront shaping with a MEMS phase-only light modulator" presents a detailed paper of a novel spatial light modulator called the Phase-only Light Modulator (PLM). This research article is authored by José C. A. Rocha, Terry Wright, Un.e G. B=utait.e, Joel Carpenter, George S. D. Gordon, and David B. Phillips. It provides a comprehensive tutorial on the operation, calibration, and application of PLMs in various light shaping tasks, accompanied by empirical assessments that demonstrate its capabilities.

Technological Context and Motivation

Spatial light modulators (SLMs) have become invaluable tools in various optical applications due to their ability to dynamically control light fields over multiple degrees of freedom. Existing technologies largely include liquid crystal devices, deformable mirrors, and digital micromirror devices (DMDs). Each has inherent trade-offs between efficiency, speed, bit depth, and cost. The PLM, based on MEMS technology, aims to bridge the critical performance gap by offering high efficiency and rapid switching rates, essential in fields such as adaptive optics, microscopy, and quantum optics.

Design and Operation

The PLM features a two-dimensional mega-pixel array of micro-mirrors with electrostatically driven pistons, each capable of vertical displacement measured with 4-bit precision. This structure allows the PLM to achieve a fundamental switching rate of up to 20 kHz, although current devices operate at a maximum of 1.44 kHz due to electronics limitations. The authors provide detailed methodologies for setting up and calibrating the PLM, including phase delay and mirror bias voltage adjustments to optimize performance for a given wavelength.

Experimental Validation and Applications

The paper includes a series of experimental results showcasing the PLM's effectiveness in various applications:

• Arbitrary Pattern Projection and Aberration Correction: The PLM successfully demonstrates the correction of optical aberrations in in-situ measurements by integrating holographic techniques with real-time phase adaptations.
• Complex Media Light Transport: The authors address light propagation control through a multimode optical fiber by employing transmission matrix methods, achieving high-fidelity focusing with a power ratio improvement and the capacity for fast focused spot scanning.
• Diffraction Efficiency: The paper characterizes the PLM's diffraction efficiency, affirming low light loss compared to its predecessors while maintaining high control over the first diffraction order.

Implications and Future Directions

The introduction of the PLM is significant for applications requiring rapid and precise beam shaping. It particularly excels in environments demanding high-speed operations not feasible with traditional liquid crystal SLMs. Given that PLMs eliminate polarization sensitivity and have high durability, while offering MEMS-based precision, they are well-suited for integration into complex optical systems requiring adaptive corrections in real-time.

As developments continue, reaching switching rates above the current limitations could catalyze new applications, particularly in dynamic optical systems such as communications and adaptive imaging. Real-time operation improvements and enhanced memory for hologram storage could further extend the scope of this technology.

In conclusion, the paper provides a robust exploration of the PLM's capabilities and applications, validating its potential to fill existing gaps in spatial light modulation technology. This structured approach to phase-only modulation through MEMs technology could become a benchmark for future advancements in optical modulation tools.