Comparison of incidental findings on cone beam computed tomographic and 2-dimensional images.

Cone beam computed tomography (CBCT) provides a 3-dimensional (3D) view of the patient and has a high frequency of incidental findings (IFs) that do not relate to the area of interest. Many of these IFs are not always visible on 2-dimensional (2D) intraoral or panoramic radiographs. Thus, the aim of the present study was to assess the IFs that did or did not appear on 3D vs 2D images. Significant IFs were recorded from a review of 510 CBCT reports by board-certified oral and maxillofacial radiologists. The IFs on CBCTs with 5-, 8-, and 11-cm fields of view (n = 170 per group) were recorded. A subset of these significant IFs was also viewed on intra-oral and panoramic radiographs to determine whether they were or were not visible in 2D imaging. A total of 677 significant IFs were discovered on 302 (59.2%) of the 510 reports. When a subset of 293 IFs was reviewed on intraoral and panoramic imaging, 112 (38.2%) were not visible on 2D radiographs, while 50 (17.1%) could not be confirmed with certainty. The frequency of significant IFs on CBCT imaging is high and increases with larger fields of view. A substantial number of these findings could not be seen on 2D radiographs, implying that many IFs are visible only on 3D images. Clinicians who order CBCT scans need to carefully review the volume in its entirety, regardless of previous imaging, so as not to miss any significant and relevant findings.

Broadly tunable and ultra-highly selective detection of radio frequency signals enabled by a silicon photonic chip.

Precise and agile detection of radio frequency (RF) signals over an ultra-wide frequency range is a key functionality in modern communication, radar, and surveillance systems, as well as for radio astronomy and laboratory testing. However, current microwave solutions are inadequate for achieving the needed high performance in a chip-scale format, with the desired reduced cost, size, weight, and power. Photonics-based technologies have been identified as a potential solution but the need to compensate for the inherent noise of the involved laser sources have prevented on-chip realization of wideband RF signal detection systems. Here, we report an approach for ultra-wide range, highly-accurate detection of RF signals using a conceptually novel feed-forward laser's noise cancelling architecture integrated on chip. The technique is applied to realization of an RF scanning receiver as well as a complete radar transceiver integrated on a CMOS-compatible silicon-photonics chip, offering an unprecedented selectivity > 80 dB, spectral resolution < 1 kHz, and tunability in the full 0.5-35 GHz range. The reported work represents a significant step towards the development of integrated system-on-chip platforms for signal detection, analysis and processing in cognitive communication and radar network applications.

Full recovery of ultrafast waveforms lost under noise.

The ability to detect ultrafast waveforms arising from randomly occurring events is essential to such diverse fields as bioimaging, spectroscopy, radio-astronomy, sensing and telecommunications. However, noise remains a significant challenge to recover the information carried by such waveforms, which are often too weak for detection. The key issue is that most of the undesired noise is contained within the broad frequency band of the ultrafast waveform, such that it cannot be alleviated through conventional methods. In spite of intensive research efforts, no technique can retrieve the complete description of a noise-dominated ultrafast waveform of unknown parameters. Here, we propose a signal denoising concept involving passive enhancement of the coherent content of the signal frequency spectrum, which enables the full recovery of arbitrary ultrafast waveforms buried under noise, in a real-time and single-shot fashion. We experimentally demonstrate the retrieval of picosecond-resolution waveforms that are over an order of magnitude weaker than the in-band noise. By granting access to previously undetectable information, this concept shows promise for advancing various fields dealing with weak or noise-dominated broadband waveforms.

Nonlinear time-lens with improved power efficiency through a discrete multilevel pump.

We report a novel, to the best of our knowledge, all-optical discrete multilevel time-lens (DM-TL) design based on cross-phase modulation (XPM). In this approach, the pump is synthesized such as the quadratic phase modulation is applied to the probe in constant-level time-bins with a maximum phase excursion of 2π. As a result, a considerable reduction in the required pump power is achieved in comparison to the conventional approach based on a parabolic pump. To illustrate the concept, the proposed DM-TL is here applied to the energy-preserving conversion of a continuous-wave (CW) signal into a train of pulses according to the theory of temporal Talbot array illuminators. We demonstrate CW-to-pulse conversion gains up to 12 at repetition rates exceeding 16 GHz, with a power saving with respect to the conventional parabolic TL that is more significant for increasing conversion gains.

Nonlinear time-lens with improved power efficiency through a discrete multilevel pump: publisher's note.

This publisher's note contains corrections to Opt. Lett.45, 3557 (2020).OPLEDP0146-959210.1364/OL.396342.