Publications

June 15, 2025June 15, 2025

Unveiling the evolution of light within photonic integrated circuits.

Fourier-space imaging and extraction of the wave vector components.

Optica Vol. 11, Issue 1, pp. 42-47 (2024)

Matan Iluz, Kobi Cohen, Jacob Kheireddine, Yoav Hazan, Amir Rosenthal, Shai Tsesses, and Guy Bartal

Abstract:

Silicon photonics leverages mature semiconductor technology to produce cost-effective and high-performance components for various applications in data centers, artificial intelligence, and quantum computing. While the geometry of photonic integrated circuits can be characterized by existing means, their optimal and accurate performance requires detailed characterization of the light propagating within them. Here we demonstrate the first, to our knowledge, direct visualization of the light as it travels inside photonic integrated circuits. We employ the natural nonlinear optical properties of silicon to directly map the electric field of the waves guided inside the integrated circuits, characterizing waveguides and multimode splitters while extracting various parameters of the device—all in real-time and in a noninvasive manner. Our approach for visualizing light inside photonic circuits is the only solution directly providing such information without any overhead or penalty, potentially making it a crucial component for the characterization of photonic circuitry, toward their improved design, fabrication, and optimization.

Imaging light within the MMI splitter. (a) Optical imaging of the MMI device. (b) Direct mapping of the light evolution inside an MMI device. The figure comprises exposures of seven different locations along the device, stitched together to track the evolution in the MMI. The rightmost exposure is at the single-waveguide input while the leftmost is of the two waveguides. (c) Zoom-in of (b). (d) Simulation results on a similar scale to (c). (b)–(d) show the intensity of the transverse electric field. Evidently, the experimental results are in excellent agreement with the simulation of light evolution in such a system.
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Optica Vol. 11, Issue 1, pp. 42-47 (2024)

Matan Iluz, Kobi Cohen, Jacob Kheireddine, Yoav Hazan, Amir Rosenthal, Shai Tsesses, and Guy Bartal

June 12, 2025June 12, 2025

Large-field-of-view optical-resolution optoacoustic microscopy using a stationary silicon-photonics acoustic detector.

Journal of Biomedical Optics, Vol. 29, Issue S1

Tamar Harary, Michael Nagli, Nathan Suleymanov, Ilya Goykhman, Amir Rosenthal

Abstract:

Significance
Optical-resolution optoacoustic microscopy (OR-OAM) enables label-free imaging of the microvasculature by using optical pulse excitation and acoustic detection, commonly performed by a focused optical beam and an ultrasound transducer. One of the main challenges of OR-OAM is the need to combine the excitation and detection in a coaxial configuration, often leading to a bulky setup that requires physically scanning the ultrasound transducer to achieve a large field of view.

Aim
The aim of this work is to develop an OR-OAM configuration that does not require physically scanning the ultrasound transducer or the acoustic beam path.

Approach
Our OR-OAM system is based on a non-coaxial configuration in which the detection is performed by a silicon-photonics acoustic detector (SPADE) with a semi-isotropic sensitivity. The system is demonstrated in both epi- and trans-illumination configurations, where in both configurations SPADE remains stationary during the imaging procedure and only the optical excitation beam is scanned.

Results
The system is showcased for imaging resolution targets and for the in vivo visualization of the microvasculature in a mouse ear. Optoacoustic imaging with focal spots down to 1.3μm, lateral resolution of 4μm, and a field of view higher than 4 mm in both lateral dimensions were demonstrated.

Conclusions
We showcase a new OR-OAM design, compatible with epi-illumination configuration. This setup enables relatively large fields of view without scanning the acoustic detector or acoustic beam path. Furthermore, it offers the potential for high-speed imaging within compact, miniature probe and could potentially facilitate the clinical translation of OR-OAM technology.

In vivo MIP images of a portion of a mouse ear. (a) Region of interest of 4.2×3mm2 is highlighted in orange frame. (b) An MIP image corresponding to the FOV marked in orange obtained using trans-illumination configuration. (c) Region of interest of 2.5×5mm2 marked in green. (d) An MIP image corresponds to the FOV marked in green obtained using trans-illumination setup. A small part of the capillary network is enlarged on the right of the full image. (e) Magnified view of a 1D scan of two capillaries, indicated by a white dashed line is demonstrated to showcase the system resolution capabilities. (f) Region of interest of2×3mm2 marked in blue. (g) An MIP image corresponds to the FOV marked in blue obtained using epi-illumination setup.

Tamar Harary, Michael Nagli, Nathan Suleymanov, Ilya Goykhman, Amir Rosenthal

June 11, 2025

Silicon photonic acoustic detector (SPADE) using a silicon nitride microring resonator.

Photoacoustics Volume 32, August 2023, 100527

Michael Nagli, Ron Moisseev, Nathan Suleymanov, Eitan Kaminski, Yoav Hazan, Gil Gelbert, Ilya Goykhman, Amir Rosenthal Abstract: Silicon photonics is an emerging platform for acoustic sensing, offering exceptional miniaturization and sensitivity. While efforts have focused on silicon-based resonators, silicon nitride resonators can potentially achieve higher Q-factors, further enhancing sensitivity. In this work, a 30 µm silicon nitride microring resonator was fabricated and coated with an elastomer to optimize acoustic sensitivity and signal fidelity. The resonator was characterized acoustically, and its capability for optoacoustic tomography was demonstrated. An acoustic bandwidth of 120 MHz and a noise-equivalent pressure of ∼ 7 mPa/Hz^1/2 were demonstrated. The spatially dependent impulse response agreed with theoretical predictions, and spurious acoustic signals, such as reverberations and surface acoustic waves, had a marginal impact. High image fidelity optoacoustic tomography of a 20 µm knot was achieved, confirming the detector’s imaging capabilities. The results show that silicon nitride offers low signal distortion and high-resolution optoacoustic imaging, proving its versatility for acoustic imaging applications.

Fig. 3D optoacoustic reconstruction of a surgical suture. (a) 2D maximum amplitude projection image of the suture. (b) Photograph of the suture showing the similarity between the reconstruction and the imaged object. (a) and (b) are the same scale. (c) 2D slice along the white dashed line shown in (a); shows the cross-section of the suture and demonstrates the lateral and axial resolutions. Read more –Photoacoustics Volume 32, August 2023, 100527 Michael Nagli, Ron Moisseev, Nathan Suleymanov, Eitan Kaminski, Yoav Hazan, Gil Gelbert, Ilya Goykhman, Amir Rosenthal

June 12, 2023June 13, 2023

Hybrid optical parametrically-oscillating emitter at 1930 nm for volumetric photoacoustic imaging of water content

Schematic diagram of the hybrid optical parametrically-oscillating emitter (HOPE) at 1930 nm.

eLight 2, 6 (2022) Jiawei Shi, Mingsheng Li, Huajun Tang, Jiqiang Kang, Najia Sharmin, Amir Rosenthal & Kenneth K. Y. Wong Abstract: Water plays a vital role in biological metabolism and it would be essential to trace the water content non-invasively, such as leveraging the vibrational absorption peak of the O–H bond. However, due to the lack of an efficient laser source, it was challenging to image the water content in the deep tissue with micron-level spatial resolution. To address this problem, we develop a high-power hybrid optical parametrically-oscillating emitter (HOPE) at 1930 nm, at which the vibrational absorption peak of the O–H bond locates. The maximum pulse energy is over 1.74 μJ with a pulse repetition rate of 50 kHz and a pulse width of 15 ns. We employ this laser source in the optical-resolution photoacoustic microscopy (OR-PAM) system to image the water content in the phantom and the biological tissue in vitro. Our 1930-nm OR-PAM could map the water content in the complex tissue environment at high spatial resolution, deep penetration depth, improved sensitivity, and suppressed artifact signal of the lipid.

Fig. PA image of (a) water acquired by 1930-nm OR-PAM and b lipid acquired by 1750-nm OR-PAM; c Overlaid PA image of (a) and (b). d Photography of the adipose tissue. e–f Three-dimensional rendering view of (a, b). Scale bars, 500 µm Read more – eLight 2, 6 (2022) Jiawei Shi, Mingsheng Li, Huajun Tang, Jiqiang Kang, Najia Sharmin, Amir Rosenthal & Kenneth K. Y. Wong

March 29, 2022March 29, 2022

Silicon-photonics acoustic detector for optoacoustic micro-tomography.

© 2022 Nature Communications Technology developed at the Andrew and Erna Viterbi Faculty of Electrical and Computer Engineering will allow the miniaturization of ultrasound transducers, thereby improving their resolution New technology that allows for very high-resolution medical imaging (close to 10 µm) is expected to lead to the development of tiny and effective ultrasound systems and other medical applications. The innovative technology, SPADE, is based on research led by Professor Amir Rosenthal and Ph.D. student Yoav Hazan of the Andrew and Erna Viterbi Faculty of Electrical and Computer Engineering at the Technion-Israel Institute of Technology. Their findings were published in Nature Communications.

Prof. Amir Rosenthal (left) and Ph.D. student Yoav Hazan of the Andrew and Erna Viterbi Faculty of Electrical and Computer Engineering

Medical ultrasound is an accepted and common tool for monitoring various physiological conditions in internal tissues. Its great advantage is that unlike CT scans and x-rays, it is not based on ionizing radiation, which is considered dangerous in high doses. The main component of ultrasound systems is the transducer – an electro-mechanical device that transmits and receives ultrasound waves. One of the technological challenges in the world of ultrasound is the development of endoscopic transducers – miniature transducers inserted through a tiny hole in the skin, or from one of the body’s natural orifices in a minimally invasive procedure. Such transducers are essential because the scan of deep tissue regions often requires a small transducer that comes close to the target tissue. The challenge in developing these transducers stems in part from the fact that miniaturization impairs their sensitivity, making it difficult to create high-quality images. The SPADE (Silicon-Photonics Acoustic Detector) technology developed by the Technion researchers is based on optical components instead of electrical components that literally alter the image. It provides the possibility to perform ultrasound tests in resolutions not previously achieved. The researchers stress that the new technology could dramatically improve the resolution of additional diagnostic methods such as vascular imaging using optoacoustics. In this regard, the article in Nature Communications presents mapping of blood vessels in a mouse’s ear at an unprecedented resolution (about 10 microns).

The study was supported by the Russell Berrie Nanotechnology Institute (RBNI), the National Science Foundation, the Polak Foundation, the Israel Innovation Authority, the Israel Science Foundation and the Ollendorf Minerva Center. Read more – © 2022 Nature Comunication -Silicon-photonics acoustic detector for optoacoustic micro-tomography.

June 18, 2023

High-resolution silicon photonics focused ultrasound transducer with a sub-millimeter aperture.

Schematic illustration of the developed transducer

2023 Optics Letters Vol. 48, Issue 10, pp. 2668-2671 Michael Nagli, Jürgen Koch, Yoav Hazan, Ahiad Levi, Orna Ternyak, Ludger Overmeyer, and Amir Rosenthal Abstract We present an all-optical focused ultrasound transducer with a sub-millimeter aperture and demonstrate its capability for high-resolution imaging of tissue ex vivo. The transducer is composed of a wideband silicon photonics ultrasound detector and a miniature acoustic lens coated with a thin optically absorbing metallic layer used to produce laser-generated ultrasound. The demonstrated device achieves axial resolution and lateral resolutions of 12 μm and 60 μm, respectively, well below typical values achieved by conventional piezoelectric intravascular ultrasound. The size and resolution of the developed transducer may enable its use for intravascular imaging of thin fibrous cap atheroma. [Read more…]

Fig. Imaging experiments. (a),(c) Optical images of acoustic targets. (b),(d) Ultrasound images of the targets shown in panels (a),(c). (a),(b) Images of 50-µm tungsten wires. (c),(d) Images of lamb meat and fat tissue; (d) is a 1D line scan image along the dotted line shown in panel (c); on the right side are three 0.5 mm × 0.5 mm close-up images. The image in panel (d) is “rolled” and shown in the polar coordinate system.

Michael Nagli, Jürgen Koch, Yoav Hazan, Ahiad Levi, Orna Ternyak, Ludger Overmeyer, and Amir Rosenthal

2023 Optics Letters Vol. 48, Issue 10, pp. 2668-2671 https://doi.org/10.1364/OL.486567

June 13, 2023June 13, 2023

All-optical optoacoustic micro-tomography in reflection mode.

2023 Biomedical Engineering Letters Tamar Harary, Yoav Hazan & Amir Rosenthal Abstract High-resolution optoacoustic imaging at depths beyond the optical diffusion limit is conventionally performed using a microscopy setup where a strongly focused ultrasound transducer samples the image object point-by-point. Although recent advancements in miniaturized ultrasound detectors enables one to achieve microscopic resolution with an unfocused detector in a tomographic configuration, such an approach requires illuminating the entire object, leading to an inefficient use of the optical power, and imposing a trans-illumination configuration that is limited to thin objects. We developed an optoacoustic micro-tomography system in an epi-illumination configuration, in which the illumination is scanned with the detector. The system is demonstrated in phantoms for imaging depths of up to 5 mm and in vivo for imaging the vasculature of a mouse ear. Although image-formation in optoacoustic tomography generally requires static illumination, our numerical simulations and experimental measurements show that this requirement is relaxed in practice due to light diffusion, which homogenizes the fluence in deep tissue layers. [Read more…]

Fig. In-vivo Tomographic imaging. Figure 8-a: Microscope images of mouse ear (left) and corresponding MIP of the optoacoustic image (right). Figure 8-b: Montage of four different tomographic depth. The depth difference between each consecutive slice was 50 μm. Figure 8-c. Typical raw OA signals from a mouse ear. Scale bar: 1 mm

Tamar Harary, Yoav Hazan & Amir Rosenthal

2023 Biomedical Engineering Letters https://doi.org/10.1007/s13534-023-00278-8

June 13, 2023June 13, 2023

Homodyne time-of-flight acousto-optic imaging for low-gain photodetector.

2023 Biomedical Engineering Letters volume 13, pages49–56 Ahiad R.Levi, Yoav Hazan, Aner Lev, Bruno G. Sfez & Amir Rosenthal Abstract Acousto-optics imaging (AOI) is a hybrid imaging modality that is capable of mapping the light fluence rate in deep tissue by local ultrasound modulation of the diffused photons. Since the intensity of the modulated photons is relatively low, AOI systems often rely on high-gain photodetectors, e.g. photomultiplier tubes (PMTs), which limit scalability due to size and cost and may significantly increase the relative shot-noise in the detected signal due to low quantum yields or gain noise. In this work, we have developed a homodyne AOI scheme in which the modulated photons are amplified by interference with a reference beam, enabling their detection with a single low-gain photodetector in reflection-mode configuration. We experimentally demonstrate our approach with a silicon photodiode, achieving over a 4-fold improvement in SNR in comparison to a PMT-based setup. The increased SNR manifested in lower background noise level thus enabling deeper imaging depths. The use of a fiber-based configuration enables the integration of our scheme in a hand-held AOI probe. [Read more…]

Figure – Normalized power spectrum measured in the spatial position in which the AOI was maximal using conventional ToF-AOI with a PMT (blue) and our homodyne approach with a PD (red). A consistent decrease in noise level measured in both cases in favour of PD. The 2nd and 3rd harmonics of the US signal are visible for both techniques. (Color figure online).

Ahiad R.Levi, Yoav Hazan, Aner Lev, Bruno G. Sfez & Amir Rosenthal

2023 Biomedical Engineering Letters volume 13, pages49–56 https://doi.org/10.1007/s13534-022-00252-w

June 13, 2023

Hand-Held Optoacoustic System for the Localization of Mid-Depth Blood Vessels.

A photograph of the assembled optoacoustic probe.

Photonics 2022, 9(12), 907 Zohar Or, Ahiad R.Levi, Yoav Hazan and Amir Rosenthal Abstract The ability to rapidly locate blood vessels in patients is important in many clinical applications, e.g., in catheterization procedures. Optical techniques, including visual inspection, generally suffer from a reduced performance at depths below 1 mm, while ultrasound and optoacoustic tomography are better suited to a typical depth on the scale of 1 cm and require an additional spacer between the tissue and transducer in order to image the superficial structures at the focus plane. For this work, we developed a hand-held optoacoustic probe, designed for localizing blood vessels from the contact point down to a depth of 1 cm, without the use of a spacer. The probe employs a flat lens-free ultrasound array, enabling a largely depth-independent response down to a depth of 1 cm, at the expense of low elevational resolution. Specifically, while in lens-based probes, the acoustic signals from outside the focal region suffer from distortion, in our probe, only the amplitude of the signal varies with depth, thus leading to an imaging quality that is largely depth-independent in the imaged region. To facilitate miniaturization, dark-field illumination is used, whereby light scattering from the tissue is exploited to homogenize the sensitivity field. [Read more…]

Figure-Optoacoustic images of the blood vessels in a human wrist, at different depths and orientations. A cross-section of the radial artery can be seen clearly in real time at depths up to 7 mm, as in (a,c). A deep vein can be seen in (b) at a depth of 8 mm. In (d), we can see a vein diving from 3 to 7 mm in a longitudinal cross-section. The scale bar in subfigure (a) applies to all subfigures.

Zohar Or, Ahiad R.Levi, Yoav Hazan and Amir Rosenthal

Photonics 2022, 9(12), 907; https://doi.org/10.3390/photonics9120907

June 13, 2023

Silicon-photonics focused ultrasound detector for minimally invasive optoacoustic imaging.

ptoacoustic image of a double-loop-shaped

Biomedical Optics Express Vol. 13, Issue 12, pp. 6229-6244 (2022) © 2022 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement Michael Nagli, Jürgen Koch, Yoav Hazan, Oleg Volodarsky, Resmi Ravi Kumar, Ahiad Levi, Evgeny Hahamovich, Orna Ternyak, Ludger Overmeyer, and Amir Rosenthal Abstract One of the main challenges in miniaturizing optoacoustic technology is the low sensitivity of sub-millimeter piezoelectric ultrasound transducers, which is often insufficient for detecting weak optoacoustic signals. Optical detectors of ultrasound can achieve significantly higher sensitivities than their piezoelectric counterparts for a given sensing area but generally lack acoustic focusing, which is essential in many minimally invasive imaging configurations. In this work, we develop a focused sub-millimeter ultrasound detector composed of a silicon-photonics optical resonator and a micro-machined acoustic lens. The acoustic lens provides acoustic focusing, which, in addition to increasing the lateral resolution, also enhances the signal. The developed detector has a wide bandwidth of 84 MHz, a focal width smaller than 50 µm, and noise-equivalent pressure of 37 mPa/Hz1/2 – an order of magnitude improvement over conventional intravascular ultrasound. We show the feasibility of the approach and the detector’s imaging capabilities by performing high-resolution optoacoustic microscopy of optical phantoms with complex geometries. [Read more…]

Fig. The detector’s fabrication process. (a) Schematic description of the bonding and the substrate etching steps. (b) A waveguide array fabricated on top of an SOI die (left), an acoustic lens within a quartz substrate (center), and an etched waveguide array bonded to the acoustic lens (right). (c) Fiber bonding setup. The detector is placed under a microscope and between two rotating fiber holders, each connected to a 5-degree of freedom manipulator (x, y, z, pitch, yaw). (d) The assembled detector mounted on the scanning system (3D stage) inside a water tank.

Michael Nagli, Jürgen Koch, Yoav Hazan, Oleg Volodarsky, Resmi Ravi Kumar, Ahiad Levi, Evgeny Hahamovich, Orna Ternyak, Ludger Overmeyer, and Amir Rosenthal.