# Publications

2020
Roy Zektzer, Matthew T Hummon, Liron Stern, Yoel Sebbag, Yefim Barash, Noa Mazurski, John Kitching, and Uriel Levy. 2020. “A Chip-Scale Optical Frequency Reference for the Telecommunication Band Based on Acetylene.” Laser & Photonics Reviews, Pp. 1900414.
Liron Stern, Jordan R. Stone, Songbai Kang, Daniel C. Cole, Myoung-Gyun Suh, Connor Fredrick, Zachary Newman, Kerry Vahala, John Kitching, Scott A. Diddams, and Scott B. Papp. 2020. “Direct Kerr frequency comb atomic spectroscopy and stabilization.” Science Advances, 6, 9, Pp. eaax6230. Abstract
\textlessp\textgreaterMicroresonator-based soliton frequency combs, microcombs, have recently emerged to offer low-noise, photonic-chip sources for applications, spanning from timekeeping to optical-frequency synthesis and ranging. Broad optical bandwidth, brightness, coherence, and frequency stability have made frequency combs important to directly probe atoms and molecules, especially in trace gas detection, multiphoton light-atom interactions, and spectroscopy in the extreme ultraviolet. Here, we explore direct microcomb atomic spectroscopy, using a cascaded, two-photon 1529-nm atomic transition in a rubidium micromachined cell. Fine and simultaneous repetition rate and carrier-envelope offset frequency control of the soliton enables direct sub-Doppler and hyperfine spectroscopy. Moreover, the entire set of microcomb modes are stabilized to this atomic transition, yielding absolute optical-frequency fluctuations at the kilohertz level over a few seconds and \textless1-MHz day-to-day accuracy. Our work demonstrates direct atomic spectroscopy with Kerr microcombs and provides an atomic-stabilized microcomb laser source, operating across the telecom band for sensing, dimensional metrology, and communication.\textless/p\textgreater
Wei Zhang*, Liron Stern*, David Carlson, Douglas Bopp, Zachary Newman, Songbai Kang, John Kitching, and Scott B Papp. 2020. “Ultranarrow Linewidth Photonic-Atomic Laser.” *(Eq. Contrib.) Laser & Photonics Reviews, 14, 4, Pp. 1900293.
Liron Stern, Wei Zhang, Lin Chang, Joel Guo, Chao Xiang, Minh A Tran, Duanni Huang, Jonathan D Peters, David Kinghorn, John E Bowers, and Scott Papp. 2020. “Ultra-precise optical-frequency stabilization with heterogeneous III–V/Si lasers.” Optics Letters, 45, 18, Pp. 5275–5278.
2019
Liron Stern, Douglas G. Bopp, Susan A. Schima, Vincent N. Maurice, and John E. Kitching. 2019. “Chip-scale atomic diffractive optical elements.” Nature Communications, 10, 1, Pp. 3156. Abstract
The efficient light–matter interaction and discrete level structure of atomic vapors made possible numerous seminal scientific achievements including time-keeping, extreme non-linear interactions, and strong coupling to electric and magnetic fields in quantum sensors. As such, atomic systems can be regarded as a highly resourceful quantum material platform. Recently, the field of thin optical elements with miniscule features has been extensively studied demonstrating an unprecedented ability to control photonic degrees of freedom. Hybridization of atoms with such thin optical devices may offer a material system enhancing the functionality of traditional vapor cells. Here, we demonstrate chip-scale, quantum diffractive optical elements which map atomic states to the spatial distribution of diffracted light. Two foundational diffractive elements, lamellar gratings and Fresnel lenses, are hybridized with atomic vapors demonstrating exceptionally strong frequency-dependent, non-linear and magneto-optic behaviors. Providing the design tools for chip-scale atomic diffractive optical elements develops a path for compact thin quantum-optical elements. Quantum coherence and the nonlinear properties of atoms are highly useful in optical devices. Here the authors show quantum-optic hybrid platforms in fully integrated chip-scale atomic diffractive optical elements by embedding hot atomic Rb vapor in microfabricated structures in silicon.
2018
Roy Zektzer, Liron Stern, Noa Mazurski, and Uriel Levy. 2018. “Enhanced light–matter interactions in plasmonic–molecular gas hybrid system.” Optica, 5, 4, Pp. 486.
Liron Stern, Meir Grajower, Noa Mazurski, and Uriel Levy. 2018. “Magnetically Controlled Atomic-Plasmonic Fano Resonances.” Nano Letters. Abstract
Following the efforts of size reduction and the integration of light and vapor systems, great promise is held in the integration of vapor and confined electromagnetic waves. By confining light to nanoscale dimensions, fundamental properties of light-vapor interactions may vary significantly. For example, the state of polarization may be modified as compared with weakly focused beams. Specifically, in transverse magnetic modes, the existence of a longitudinal field component, which is in quadrature to the transverse field, generates a "circular-like" polarized light. Here, by taking advantage of this very property, we study the interaction of confined light and vapor in a coupled system of plasmons and atomic vapors in the presence of magnetic fields. Our results show that the spectroscopic nature and Fano resonances of the hybrid plasmonic-atomic system are greatly altered. In parallel, we also exploit the existence of the atoms in proximity to the plasmonic mode to probe the polarization state of the electromagnetic field and reveal the longitudinal-to-transverse ratio between the plasmonic modes components in the near field. Interestingly, our system maps the amplitude and phase information of the electromagnetic modes to the spectral domain. As such, combining magnetic fields with the coupled plasmonic-atomic system has the potential for future applications in high spatial resolution magnetometry, near-field vectorial imaging, and magnetically induced switching and tuning.
Alex Naiman, Liron Stern, and Uriel Levy. 2018. “On-chip beam positioning sensor via frequency locked cascaded ring resonators.” Applied Physics Letters. Abstract
We demonstrate an approach for on-chip beam positioning with a position accuracy of up to 100 nm. This approach is based on tracking the resonance of two adjacent microring resonators that are implemented on a silicon on insulator chip. We demonstrate the functionality of our approach by illuminating the chip through a Near Field Scanning Optical Microscope tip and monitoring the shift of the microring resonances due to the thermo-optic effect. We also discuss the contribution of different effects such as free carrier absorption and dispersion to the resonance shift.
Eliran Talker, Pankaj Arora, Yefim Barash, Liron Stern, and Uriel Levy. 2018. “Plasmonic Enhanced EIT and Velocity Selective Optical Pumping Measurements with Atomic Vapor.” ACS Photonics, 5, 7, Pp. 2609–2616. Abstract
In this work, we experimentally observe for the first time nanoscale plasmonic enhanced Electromagnetically Induced Transparency (EIT) and Velocity Selective Optical Pumping (VSOP) effects in miniaturized Integrated Quantum Plasmonic Device (IQPD) for D2 transitions in rubidium (Rb). Our device consists of a vapor cell integrated on top of a prism coated with a thin layer of metal. This configuration is known to allow efficient excitation of Surface Plasmon Resonance (SPR). The evanescent field of the surface plasmon mode interacts with the atomic media in close vicinity to the metal. In spite of the limited interaction length between SPR and Rb atoms, the signature of EIT along with VSOP signals could be clearly observed in our miniaturized IQPD under proper conditions of pump and probe intensities. A gradual decrease in the contrast of the plasmonic enhanced EIT and VSOP signals was observed as the excitation was detuned from the SPR critical angle, due to reduction in electromagnetic field enhancement, leading to a reduced interaction of the evanescent field with the atomic vapor media. Following the demonstration of these effects, we also present a detailed model revealing the mechanisms and the origin of plasmonic enhanced EIT and VSOP effects in our system. The model, which is based on the Bloch equations, is in good agreement with the observed experimental results. The obtained results are regarded as an important step in the quest for the realization of nanoscale quantum plasmonic effects and devices.
2017
Jonathan Bar-David, Liron Stern, and Uriel Levy. 2017. “Dynamic Control over the Optical Transmission of Nanoscale Dielectric Metasurface by Alkali Vapors.” Nano Letters, 17, 2, Pp. 1127–1131. Abstract
In recent years, dielectric and metallic nanoscale metasurfaces are attracting growing attention and are being used for variety of applications. Resulting from the ability to introduce abrupt changes in optical properties at nanoscale dimensions, metasurfaces enable unprecedented control over light's different degrees of freedom, in an essentially two-dimensional configuration. Yet, the dynamic control over metasurface properties still remains one of the ultimate goals of this field. Here, we demonstrate the optical resonant interaction between a form birefringent dielectric metasurface made of silicon and alkali atomic vapor to control and effectively tune the optical transmission pattern initially generated by the nanoscale dielectric metasurface. By doing so, we present a controllable metasurface system, the output of which may be altered by applying magnetic fields, changing input polarization, or shifting the optical frequency. Furthermore, we also demonstrate the nonlinear behavior of our system tak...
Eliran Talker, Liron Stern, Alex Naiman, Yefim Barash, and Uriel Levy. 2017. “Fluorescence double resonance optical pumping spectrum and its application for frequency stabilization in millimeter scale vapor cells.” Journal of Physics Communications. Abstract
In recent years, we are observing substantial efforts towards the miniaturization of atomic cells to a millimeter scale and below, with the ultimate goal of enabling efficient and compact light vapor interactions. However, such miniaturization results in a reduction in optical path, effectively reducing the contrast of the optical signal. In order to overcome this obstacle, we have introduced and demonstrated a new approach of fluorescence double resonance optical pumping (FDROP) in the ladder-type atomic system. We have developed a theoretical model to predict the FDROP spectrum and validated this model using experimental results in a millimeter-size cell. We show that the contrast of fluorescence signal of the FDROP approach is higher than the transmission signal in the double resonance optical pumping approach. Taking advantage of this desired property, we have used the FDROP for the purpose of stabilizing the frequency of a laser operating at the telecom waveband with the hyperfine structure of the 5P3/2–4D5/2 transition in a millimeter-size cell. By beating the stabilized laser to another stabilized laser, we obtained frequency instability floor of 9×10−10 at around 1000 s in terms of Allan deviation. Such sources which are stabilized to miniaturized cells may play an important building block in diverse fields ranging e.g. from communication to metrology.
Liron Stern, Boris Desiatov, Noa Mazurski, and Uriel Levy. 2017. “Strong coupling and high-contrast all-optical modulation in atomic cladding waveguides.” Nature Communications, 8, Pp. 14461. Abstract
© 2017 The Author(s). In recent years, there has been marked increase in research aimed to introduce alkali vapours into guided-wave configurations. Owing to the significant reduction in device dimensions, the increase in density of states, the interaction with surfaces and primarily the high intensities carried along the structure, a plethora of light-vapour interactions can be studied. Moreover, such platform may exhibit new functionalities such as low-power nonlinear light-matter interactions. One immense challenge is to study the effects of quantum coherence and shifts in nanoscale waveguides, characterized by ultra-small mode areas and fast dynamics. Here, we construct a highly compact 17 mm long serpentine silicon-nitride atomic vapour cladding waveguide. Fascinating and important phenomena such as van-der-Waals shifts, dynamical stark shifts and coherent effects such as strong coupling (in the form of Autler-Townes splitting) are observed. Some of these effects may play an important role in applications such as all-optical switching, frequency referencing and magnetometry.
Liron Stern, Alex Naiman, Gal Keinan, Noa Mazurski, Meir Grajower, and Uriel Levy. 2017. “Ultra-precise optical to radio frequency based chip-scale refractive index and temperature sensor.” Optica. Abstract
© 2017 Optical Society of America. Chip-scale high-precision measurements of physical quantities such as temperature, pressure, refractive index, and analytes have become common with nanophotonics and nanoplasmonics resonance cavities. Despite several important accomplishments, such optical sensors are still limited in their performances in the short and, in particular, long time regimes. Two major limitations are environmental fluctuations, which are imprinted on the measured signal, and the lack of miniaturized, scalable robust and precise methods of measuring optical frequencies directly. Here, by utilizing a frequency-locked loop combined with a reference resonator, we overcome these limitations and convert the measured signal from the optical domain to the radio-frequency domain. By doing so, we realize a highly precise on-chip sensing device with sensing precision approaching 10 −8 in effective refractive index units, and 90 $μ$K in temperature. Such an approach paves the way for single particle detection and high-precision chip-scale thermometry.
2016
Liron Stern, Anat Szapiro, Eliran Talker, and Uriel Levy. 2016. “Controlling the interactions of space-variant polarization beams with rubidium vapor using external magnetic fields.” Optics Express. Abstract
Space variant beams are of great importance for a variety of applications that have emerged in recent years. As such, manipulation of their degrees of freedom is highly desired. Here, we study the general interaction of space variant beams with a magnetically influenced Rb medium exploiting the atoms versatile properties in terms of frequency and intensity dependent circular dichroism and circular birefringence. We present the particular cases of radially polarized and hybrid polarized beams where the control of the polarization states is demonstrated experimentally. Moreover, we show that such an atomic system can be used as a tunable analyzer for space variant beams. Finally, exploiting the non-linear properties of Rb vapor, we show that we can control the circular birefringence all optically, and thus modulate the polarization of the radial polarized beam.
Liron Stern, Roy Zektzer, Noa Mazurski, and Uriel Levy. 2016. “Enhanced light-vapor interactions and all optical switching in a chip scale micro-ring resonator coupled with atomic vapor.” Laser & Photonics Reviews, 10, 6, Pp. 1016–1022.
Roy Zektzer, Liron Stern, Noa Mazurski, and Uriel Levy. 2016. “On-chip multi spectral frequency standard replication by stabilizing a microring resonator to a molecular line.” Applied Physics Letters. Abstract
Stabilized laser lines are highly desired for myriad of applications ranging from precise measurements to optical communications. While stabilization can be obtained by using molecular or atomic absorption references, these are limited to specific frequencies. On the other hand, resonators can be used as wide band frequency references. Unfortunately, such resonators are unstable and inaccurate. Here, we propose and experimentally demonstrate a chip-scale multispectral frequency standard replication operating in the spectral range of the near IR. This is obtained by frequency locking a microring resonator (MRR) to an acetylene absorption line. The MRR consists of a Si3N4 waveguides with microheater on top of it. The thermo-optic effect is utilized to lock one of the MRR resonances to an acetylene line. This locked MRR is then used to stabilize other laser sources at 980 nm and 1550 nm wavelength. By beating the stabilized laser to another stabilized laser, we obtained frequency instability floor of 4×10-9 at around 100 s in terms of Allan deviation. Such stable and accurate chip scale sources are expected to serve as important building block in diverse fields such as communication and metrology.
2015
Meir Grajower, Boris Desiatov, Ilya Goykhman, Liron Stern, Noa Mazurski, and Uriel Levy. 2015. “Direct observation of optical near field in nanophotonics devices at the nanoscale using Scanning Thermal Microscopy.” Optics Express. Abstract
© 2015 Optical Society of America.In recent years, following the miniaturization and integration of passive and active nanophotonic devices, thermal characterization of such devices at the nanoscale is becoming a task of crucial importance. The Scanning Thermal Microscopy (SThM) is a natural candidate for performing this task. However, it turns out that the SThM capability to precisely map the temperature of a photonic sample in the presence of light interacting with the sample is limited. This is because of the significant absorption of light by the SThM probe. As a result, the temperature of the SThM probe increases and a significant electrical signal which is directly proportional to the light intensity is obtained. As such, instead of measuring the temperature of the sample, one may directly measure the light intensity profile. While this is certainly a limitation in the context of thermal characterization of nanophotonic devices, this very property provides a new opportunity for optical near field characterization. In this paper we demonstrate numerically and experimentally the optical near field measurements of nanophotonic devices using a SThM probe. The system is characterized using several sets of samples with different properties and various wavelengths of operation. Our measurements indicate that the light absorption by the probe can be even larger than the light induced heat generation in the sample. The frequency response of the SThM system is characterized and the 3 dB frequency response was found to be ∼1.5 kHz. The simplicity of the SThM system which eliminates the need for complex optical measurement setups together with its broadband wavelength of operation makes this approach an attractive alternative to the more conventional aperture and apertureless NSOM approaches. Finally, referring to its original role in characterizing thermal effects at the nanoscale, we propose an approach for characterizing the temperature profile of nanophotonic devices which are heated by light absorption within the device. This is achieved by spatially separating between the optical near field distribution and the SThM probe, taking advantage of the broader temperature profile as compared to the more localized light profile.
Matan Galanty, Shira Yochelis, Liron Stern, Irene Dujovne, Uriel Levy, and Yossi Paltiel. 2015. “Extinction Enhancement from a Self-Assembled Quantum Dots Monolayer Using a Simple Thin Films Process.” The Journal of Physical Chemistry C, 119, 44, Pp. 24991–24995. Abstract
Hybrid nanostructures are attractive for future use in a variety of optoelectronic devices. Self-assembled hybrid organic/quantum dots can couple quantum properties to semiconductor devices and modify their functionality. These devices are simple to fabricate and control; however, they usually demonstrate low quantum efficiency. In this work we present experimental results of large extinction enhancement from a monolayer of colloidal quantum dots using a thin gold film evaporation forming random gold nanoparticles that act as plasmonic antennas. The random structures guarantee no sensitivity to polarization changes. The fabrication process of the plasmonic gold nanoparticles is simple and cheap and can be easily integrated with existing semiconductor devices. By matching the plasmonic resonance and the colloidal quantum dots bandgap we achieve up to 16% light extinction, which is 13-fold enhancement, compared to the reference. These results may pave the way toward realizing more efficient and sensitive photon detectors. Hybrid nanostructures are attractive for future use in a variety of optoelectronic devices. Self-assembled hybrid organic/quantum dots can couple quantum properties to semiconductor devices and modify their functionality. These devices are simple to fabricate and control; however, they usually demonstrate low quantum efficiency. In this work we present experimental results of large extinction enhancement from a monolayer of colloidal quantum dots using a thin gold film evaporation forming random gold nanoparticles that act as plasmonic antennas. The random structures guarantee no sensitivity to polarization changes. The fabrication process of the plasmonic gold nanoparticles is simple and cheap and can be easily integrated with existing semiconductor devices. By matching the plasmonic resonance and the colloidal quantum dots bandgap we achieve up to 16% light extinction, which is 13-fold enhancement, compared to the reference. These results may pave the way toward realizing more efficient and sensitive photon detectors.
Alex Naiman, Boris Desiatov, Liron Stern, Noa Mazurski, Joseph Shappir, and Uriel Levy. 2015. “Ultrahigh-Q silicon resonators in a planarized local oxidation of silicon platform.” Optics Letters. Abstract
© 2015 Optical Society of America. We describe a platform for the fabrication of smooth waveguides and ultrahigh-quality-factor (Q factor) silicon resonators using a modified local oxidation of silicon (LOCOS) technique. Unlike the conventional LOCOS process, our approach allows the fabrication of nearly planarized structures, supporting a multilayer silicon photonics configuration. Using this approach we demonstrate the fabrication and the characterization of a microdisk resonator with an intrinsic Q factor that is one of the highest Q factors achieved with a compact silicon-on-insulator platform.
2014
Liron Stern, Avraham Bakal, Mor Tzur, Maya Veinguer, Noa Mazurski, Nadav Cohen, and Uriel Levy. 2014. “Doppler-Based Flow Rate Sensing in Microfluidic Channels.” Sensors, 14, 9, Pp. 16799–16807. Abstract
We design, fabricate and experimentally demonstrate a novel generic method to detect flow rates and precise changes of flow velocity in microfluidic devices. Using our method we can measure flow rates of \~2 mm/s with a resolution of 0.08 mm/s. The operation principle is based on the Doppler shifting of light diffracted from a self-generated periodic array of bubbles within the channel and using self-heterodyne detection to analyze the diffracted light. As such, the device is appealing for variety of “lab on chip” bio-applications where a simple and accurate speed measurement is needed, e.g., for flow-cytometry and cell sorting.