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APL Photonics
Number of Followers: 1

This is an Open Access Journal

Open Access journal
ISSN (Online) 2378-0967
Published by AIP

[28 journals]

A surface-normal photodetector as nonlinear activation function in
diffractive optical neural networks
- First page: 121301
  Abstract: Optical neural networks (ONNs) enable high speed, parallel, and energy efficient processing compared to their conventional digital electronic counterparts. However, realizing large scale ONN systems is an open problem. Among various integrated and non-integrated ONNs, free-space diffractive ONNs benefit from a large number of pixels of spatial light modulators to realize millions of neurons. However, a significant fraction of computation time and energy is consumed by the nonlinear activation function that is typically implemented using a camera sensor. Here, we propose a novel surface-normal photodetector (SNPD) with an optical-in–electrical-out (O–E) nonlinear response to replace the camera sensor that enables about three orders of magnitude faster (5.7 µs response time) and more energy efficient (less than 10 nW/pixel) response. Direct efficient vertical optical coupling, polarization insensitivity, inherent nonlinearity with no control electronics, low optical power requirements, and the possibility of implementing large scale arrays make the SNPD a promising O–E nonlinear activation function for diffractive ONNs. To show the applicability of the proposed neural nonlinearity, successful classification simulations of the MNIST and Fashion MNIST datasets using the measured response of SNPD with accuracy comparable to that of an ideal ReLU function are demonstrated.
  PubDate: Fri, 01 Dec 2023 00:00:00 GMT
  DOI: 10.1063/5.0168959
  Issue No: Vol. 8, No. 12 (2023)
Fiber-based broadband detection of a rotational object with superposed
vortices
- First page: 126101
  Abstract: Recently, the rotational Doppler effect has attracted broad attention in detecting rotational motion. However, the presently proposed detection techniques based on the rotational Doppler effect are generally configured relying on discrete components in free space, resulting in cumbersome and inflexible systems, which brings challenges to practical applications. In this paper, we demonstrate a fiber-based configuration on rotational Doppler measurements for the detection of a rotational object using an ultra-broadband mode-selective coupler to convert the superposed vortices. Remarkably, the results show the broadband operating range of the fiber-based measurement system intuitively through wavelength scanning. The refinement of rotational Doppler detection techniques is of great significance for lowering the cost, reducing system complexity, improving system integration, and industrial manufacturing. This fiber-based scheme might be a promising candidate for facilitating the rotational Doppler effect applied as novel motion monitoring and sensing equipment in engineering and industry.
  PubDate: Fri, 01 Dec 2023 00:00:00 GMT
  DOI: 10.1063/5.0167478
  Issue No: Vol. 8, No. 12 (2023)
Complete chiroptical signal detection using weak measurement with
intensity-contrast-ratio pointers
- First page: 126102
  Abstract: Chiroptical signals, including optical rotation (OR) and circular dichroism (CD), are widely utilized as potent probes for investigating the structure and properties of chiral molecules. However, acquiring both coexisting weak OR and CD signals simultaneously in a single measurement process with a high precision remains a challenge for conventional setups. In this article, a high-precision yet easy-to-set-up method for simultaneous detection of OR and CD signals based on weak measurement is theoretically and experimentally demonstrated. In addition, the chiroptical signals are detected using two new intensity-contrast-ratio pointers, which provide an expanded measurement range compared with the shift of the mean value pointer. The proposed method has been validated through a spin Hall effect light based experiment, with precision reaching the order of 10−7 and 10−6 rad for the detection of OR and CD, respectively. These results may serve as a catalyst for further studies of fast, multi-parameter biosensing technologies with ultra-precision.
  PubDate: Mon, 04 Dec 2023 00:00:00 GMT
  DOI: 10.1063/5.0164781
  Issue No: Vol. 8, No. 12 (2023)
Hong–Ou–Mandel interference of spin–orbit hybrid
entangled photons
- First page: 126103
  Abstract: Structured photons are a crucial resource in both classical and quantum technologies, particularly in spin–orbit hybrid photons, enabling various practical applications ranging from ultra-sensitive metrology techniques to quantum-enhanced information processing tasks. However, the two-photon interference of spin–orbit hybrid photons, which combines polarization modes and complex transverse spatial structures across the beam profile, remains unexplored. Here, we present an experimental observation of Hong–Ou–Mandel (HOM) interference of spin–orbit hybrid photons. The tunable q-plates that work as spin–orbit coupler devices are used to prepare various forms of spin–orbit hybrid entangled photons. By harnessing the match degree in the temporal domain, the coalescence and anti-coalescence effects resulting from the symmetric and anti-symmetric properties of the incident quantum states are observed. Moreover, we demonstrated the feasibility of quantum-enhanced photon polarization gears through HOM interference and theoretically analyze the noise-resilient advantages based on coherent HOM measurements. These results provide an alternative route toward quantum experiments with structured photons that allows for controlling their quantum interference in a compact, stable, and efficient way.
  PubDate: Mon, 04 Dec 2023 00:00:00 GMT
  DOI: 10.1063/5.0167016
  Issue No: Vol. 8, No. 12 (2023)

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