A full degree-of-freedom spatiotemporal light modulator

Abstract

Harnessing the full complexity of optical fields requires complete control of all degrees-of-freedom within a region of space and time -an open goal for present-day spatial light modulators (SLMs), active metasurfaces, and optical phased arrays. Here, we solve this challenge with a programmable photonic crystal cavity array enabled by four key advances: (i) near-unity vertical coupling to high-finesse microcavities through inverse design, (ii) scalable fabrication by optimized, 300 mm full-wafer processing, (iii) picometer-precision resonance alignment using automated, closed-loop "holographic trimming", and (iv) out-of-plane cavity control via a high-speed µLED array. Combining each, we demonstrate near-complete spatiotemporal control of a 64-resonator, two-dimensional SLM with nanosecond-and femtojoule-order switching. Simultaneously operating wavelength-scale modes near the space-and time-bandwidth limits, this work opens a new regime of programmability at the fundamental limits of multimode optical control.

Single-shot optical neural network

“…In energy consumption, at ∼10 fJ/MAC, the optimized singleshot ONN can outperform digital electronics by one to two orders of magnitude, including sources, optical efficiency of the DOE, detectors, digital-to-analog converters (DACs), analog-todigital converters (ADCs), SLMs, transimpedance amplifiers (TIAs), and electronic nonlinearities (see Materials and Methods). To further reduce energy consumption, the fan-out and weighting LCoS SLMs could be optimized (39) or, as the DOE and weights are only updated when the model changes, replaced with elements that have zero static power consumption, e.g., with an array of optical phase change material cells (48)(49)(50), a fixed phase mask or microelectromechanical system (MEMS) modulators (51). With an increase in source and detector efficiencies (18), the overall energy consumption could then reach the single-femtojoule-per-MAC regime.…”

“…Experimental setup An LCoS SLM followed by a polarizing beamsplitter (PBS) displays an input image x by pixel-wise amplitude modulation of a collimated 532-nm CW laser diode. In the Fourier plane, a second LCoS phase mask-calculated using the fixed-phase weighted Gerchberg-Saxton algorithm (39,52)-fans out the input. In the image plane, a third LCoS SLM (also followed by a PBS) displays a complete weight matrix for pixel-wise attenuation (multiplication) of the replicated inputs.…”

Coherent VCSEL homodyne neural networks

“…A technically challenging task of this work was to engineer a scalable, coherent source of tunable, phase stable outputs. While resonant modulator arrays have been proposed for this purpose, resonator trimming and locking remain significant challenges [11], digital drive voltages are usually too high for CMOS circuitry, and the guided-wave nature of most devices leaves a moderately large area footprint ( [12]). In contrast, VCSELs stand to be very compact (< 100 μm pitch, with < 10 μm possible in micropillar lasers), compatible with CMOS drivers (low thresholds), and the lasing frequency is subject to efficient current tuning.…”

Genetic and Molecular Scanning, Manipulation and Modification Device

“…As a method beneficial to all of the above, a full degree-of-freedom spatiotemporal light modulator would provide picometre-precision delivery of light from an array of microcavities in a precisely engineered topology. This could be used in both scanning and manipulation of small-molecular scale (Panuski et al 2022;Gruzdev et al 2017).…”