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1. MEMS Actuators for Optical Microendoscopy

   https://doi.org/10.3390/mi10020085  

   Qiu, Zhen; Piyawattanametha, Wibool (February 2019, Micromachines)

   Growing demands for affordable, portable, and reliable optical microendoscopic imaging devices are attracting research institutes and industries to find new manufacturing methods. However, the integration of microscopic components into these subsystems is one of today’s challenges in manufacturing and packaging. Together with this kind of miniaturization more and more functional parts have to be accommodated in ever smaller spaces. Therefore, solving this challenge with the use of microelectromechanical systems (MEMS) fabrication technology has opened the promising opportunities in enabling a wide variety of novel optical microendoscopy to be miniaturized. MEMS fabrication technology enables abilities to apply batch fabrication methods with high-precision and to include a wide variety of optical functionalities to the optical components. As a result, MEMS technology has enabled greater accessibility to advance optical microendoscopy technology to provide high-resolution and high-performance imaging matching with traditional table-top microscopy. In this review the latest advancements of MEMS actuators for optical microendoscopy will be discussed in detail. 

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2. High-speed 3D integral imaging for sensing and visualization of dynamic underwater events

   https://doi.org/10.1364/OPTCON.530264  

   Joshi, Rakesh; Lee, Jiheon; Javidi, Bahram (August 2024, Optics Continuum)

   The study of high-speed phenomena in underwater environments is pivotal across diverse scientific and engineering domains. This paper introduces a high-speed (3D) integral imaging (InIm) based system to 1) visualize high-speed dynamic underwater events, and 2) detect modulated signals for potential optical communication applications. The proposed system is composed of a high-speed camera with a lenslet array-based integral imaging setup to capture and reconstruct 3D images of underwater scenes and detect temporally modulated optical signals. For 3D visualization, we present experiments to capture the elemental images of high-speed underwater events with passive integral imaging, which were then computationally reconstructed to visualize 3D dynamic underwater scenes. We present experiments for 3D imaging and reconstruct the depth map of high-speed underwater dynamic jets of air bubbles, offering depth information and visualizing the 3D movement of these jets. To detect temporally modulated optical signals, we present experiments to demonstrate the ability to capture and reconstruct high-speed underwater modulated optical signals in turbidity. To the best of our knowledge, this is the first report on high-speed underwater 3D integral imaging for 3D visualization and optical signal communication. The findings illustrate the potential of high-speed integral imaging in the visualization and detection of underwater dynamic events, which can be useful in underwater exploration and monitoring. 

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3. Measuring complex refractive index through deep-learning-enabled optical reflectometry

   https://doi.org/10.1088/2053-1583/acc59b  

   Wang, Ziyang; Lin, Yuxuan Cosmi; Zhang, Kunyan; Wu, Wenjing; Huang, Shengxi (March 2023, 2D Materials)

   Abstract Optical spectroscopy is indispensable for research and development in nanoscience and nanotechnology, microelectronics, energy, and advanced manufacturing. Advanced optical spectroscopy tools often require both specifically designed high-end instrumentation and intricate data analysis techniques. Beyond the common analytical tools, deep learning methods are well suited for interpreting high-dimensional and complicated spectroscopy data. They offer great opportunities to extract subtle and deep information about optical properties of materials with simpler optical setups, which would otherwise require sophisticated instrumentation. In this work, we propose a computational approach based on a conventional tabletop optical microscope and a deep learning model called ReflectoNet . Without any prior knowledge about the multilayer substrates, ReflectoNet can predict the complex refractive indices of thin films and 2D materials on top of these nontrivial substrates from experimentally measured optical reflectance spectra with high accuracies. This task was not feasible previously with traditional reflectometry or ellipsometry methods. Fundamental physical principles, such as the Kramers–Kronig relations, are spontaneously learned by the model without any further training. This approach enables in-operando optical characterization of functional materials and 2D materials within complex photonic structures or optoelectronic devices. 

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4. A Hybrid Optical-Electrical Analog Deep Learning Accelerator Using Incoherent Optical Signals

   https://doi.org/10.1145/3453688.3461531  

   Yang, Mingdai; Jokar, Mohammad Reza; Qiu, Junyi; Lou, Qiuwen; Liu, Yuming; Udupa, Aditi; Chong, Frederic T.; Dallesasse, John M.; Feng, Milton; Goddard, Lynford L.; et al (July 2021, GLSVLSI '21: Proceedings of the 2021 on Great Lakes Symposium on VLSI)

   null (Ed.)

   We present a hybrid optical-electrical analog deep learning (DL) accelerator, the first work to use incoherent optical signals for DL workloads. Incoherent optical designs are more attractive than coherent ones as the former can be more easily realized in practice. However, a significant challenge in analog DL accelerators, where multiply-accumulate operations are dominant, is that there is no known solution to perform accumulation using incoherent optical signals. We overcome this challenge by devising a hybrid approach: accumulation is done in the electrical domain, while multiplication is performed in the optical domain. The key technology enabler of our design is the transistor laser, which performs electrical-to-optical and optical-to-electrical conversions efficiently to tightly integrate electrical and optical devices into compact circuits. As such, our design fully realizes the ultra high-speed and high-energy-efficiency advantages of analog and optical computing. Our evaluation results using the MNIST benchmark show that our design achieves 2214× and 65× improvements in latency and energy, respectively, compared to a state-of-the-art memristor-based analog design. 

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5. Seconds-scale coherence on an optical clock transition in a tweezer array

   https://doi.org/10.1126/science.aay0644  

   Norcia, Matthew A.; Young, Aaron W.; Eckner, William J.; Oelker, Eric; Ye, Jun; Kaufman, Adam M. (October 2019, Science)

   Coherent control of high–quality factor optical transitions in atoms has revolutionized precision frequency metrology. Leading optical atomic clocks rely on the interrogation of such transitions in either single ions or ensembles of neutral atoms to stabilize a laser frequency at high precision and accuracy. We demonstrate a platform that combines the key strengths of these two approaches, based on arrays of individual strontium atoms held within optical tweezers. We report coherence times of 3.4 seconds, single-ensemble duty cycles up to 96% through repeated interrogation, and frequency stability of 4.7 × 10 −16 (τ/s) –1/2 . These results establish optical tweezer arrays as a powerful tool for coherent control of optical transitions for metrology and quantum information science. 

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