Mengjie Yu, Rebecca Cheng, Christian Reimer, Lingyan He, Kevin Luke, Eric Puma, Linbo Shao, Amirhassan Shams-Ansari, Hannah R. Grant, Leif Johansson, Mian Zhang, and Marko Lončar. Submitted. “Integrated Electro-Optic Isolator on Thin Film Lithium Niobate.” aeXiv. Publisher's VersionAbstract
Optical isolator is an indispensable component of almost any optical system and is used to protect a laser from unwanted reflections for phase-stable coherent operation. The development of chip-scale optical systems, powered by semiconductor lasers integrated on the same chip, has resulted in a need for a fully integrated optical isolator. However, conventional approaches based on application of magneto-optic materials to break the reciprocity and provide required isolation have significant challenges in terms of material processing and insertion loss. As a result, many magnetic-free approaches have been explored, including acousto-optics, optical nonlinearity, and electro-optics. However, to date, the realization of an integrated isolator with low insertion loss, high isolation ratio, broad bandwidth, and low power consumption on a monolithic material platform is still absent. Here we realize non-reciprocal traveling-wave EO-based isolator on thin-film LN, enabling maximum optical isolation of 48 dB and an on-chip insertion loss of 0.5 dB using a single-frequency microwave drive at 21-dBm RF power. The isolation ratio is verified to be larger than 37 dB across a tunable optical wavelength range from 1510 to 1630 nm. We verify that our hybrid DFB laser - LN isolator module successfully protects the single-mode operation and the linewidth of the DFB laser from reflection. Our result is a significant step towards a practical high-performance optical isolator on chip.
Keshav Kapoor, Si Xie, Joaquin Chung, Raju Valivarthi, Cristián Peña, Lautaro Narváez, Neil Sinclair, Jason P. Allmaras, Andrew D. Beyer, Samantha I. Davis, Gabriel Fabre, George Iskander, Gregory S. Kanter, Rajkumar Kettimuthu, Boris Korzh, Prem Kumar, Nikolai Lauk, Andrew Mueller, Matthew Shaw, Panagiotis Spentzouris, Maria Spiropulu, Jordan M. Thomas, and Emma E. Wollman. Submitted. “Picosecond Synchronization of Photon Pairs through a Fiber Link between Fermilab and Argonne National Laboratories.” arXiv. Publisher's Version
Julian Klein, Zhigang Song, Benjamin Pingault, Florian Dirnberger, Hang Chi, Jonathan B. Curtis, Rami Dana, Rezlind Bushati, Jiamin Quan, Lukas Dekanovsky, Zdenek Sofer, Andrea Alù, Vinod M. Menon, Jagadeesh S. Moodera, Marko Lončar, Prineha Narang, and Frances M. Ross. Submitted. “Sensing the local magnetic environment through optically active defects in a layered magnetic semiconductor.” arXiv:2207.02884. Publisher's VersionAbstract
Atomic-level defects in van der Waals (vdW) materials are essential building blocks for quantum technologies and quantum sensing applications. The layered magnetic semiconductor CrSBr is an outstanding candidate for exploring optically active defects owing to a direct gap in addition to a rich magnetic phase diagram including a recently hypothesized defect-induced magnetic order at low temperature. Here, we show optically active defects in CrSBr that are probes of the local magnetic environment. We observe spectrally narrow (1 meV) defect emission in CrSBr that is correlated with both the bulk magnetic order and an additional low temperature defect-induced magnetic order. We elucidate the origin of this magnetic order in the context of local and non-local exchange coupling effects. Our work establishes vdW magnets like CrSBr as an exceptional platform to optically study defects that are correlated with the magnetic lattice. We anticipate that controlled defect creation allows for tailor-made complex magnetic textures and phases with the unique ingredient of direct optical access.
Marc Jankowski, Carsten Langrock, Boris Desiatov, Marko Loncar, and MM Fejer. Submitted. “Supercontinuum Generation by Saturated Interactions.” arXiv:1912.06642. Publisher's VersionAbstract
We demonstrate a new approach to supercontinuum generation and carrier-envelope-offset detection in dispersion-engineered nanophotonic waveguides based on saturated second-harmonic generation of femtosecond pulses. In contrast with traditional approaches based on self-phase modulation, this technique simultaneously broadens both harmonics by generating rapid amplitude modulations of the field envelopes. The generated supercontinuum produces coherent carrier-envelope-offset beatnotes in the overlap region that remain in phase across 100’s of nanometers of bandwidth while requiring <10 picojoules of pulse energy.
Alexa Herter, Amirhassan Shams-Ansari, Francesca Fabiana Settembrini, Hana K. Warner, Jérôme Faist, Marko Lončar, and Ileana-Cristina Benea-Chelmus. Submitted. “Terahertz waveform synthesis from integrated lithium niobate circuits.” arxiv, 2204.11725. Publisher's VersionAbstract
Bridging the "terahertz (THz) gap" relies upon synthesizing arbitrary waveforms in the THz domain enabling applications that require both narrow band sources for sensing and few-cycle drives for classical and quantum objects. However, realization of custom-tailored waveforms needed for these applications is currently hindered due to limited flexibility for optical rectification of femtosecond pulses in bulk crystals. Here, we experimentally demonstrate that thin-film lithium niobate (TFLN) circuits provide a versatile solution for such waveform synthesis through combining the merits of complex integrated architectures, low-loss distribution of pump pulses on-chip, and an efficient optical rectification. Our distributed pulse phase-matching scheme grants shaping the temporal, spectral, phase, amplitude, and farfield characteristics of the emitted THz field through designer on-chip components. This strictly circumvents prior limitations caused by the phase-delay mismatch in conventional systems and relaxes the requirement for cumbersome spectral pre-engineering of the pumping light. We provide a toolbox of basic blocks that produce broadband emission up to 680 GHz with adaptable phase and coherence properties by using near-infrared pump pulse energies below 100 pJ.
Julian Klein, Benjamin Pingault, Matthias Florian, Marie-Christin Heißenbüttel, Alexander Steinhoff, Zhigang Song, Kierstin Torres, Florian Dirnberger, Jonathan B. Curtis, Thorsten Deilmann, Rami Dana, Rezlind Bushati, Jiamin Quan, Jan Luxa, Zdenek Sofer, Andrea Alù, Vinod M. Menon, Ursula Wurstbauer, Michael Rohlfing, Prineha Narang, Marko Lončar, and Frances M. Ross. Submitted. “The bulk van der Waals layered magnet CrSBr is a quasi-1D quantum material.” arxiv, 2205.13456. Publisher's VersionAbstract
Correlated quantum phenomena in one-dimensional (1D) systems that exhibit competing electronic and magnetic orders are of fundamental interest. Interaction effects in low-dimensional systems can lead to fundamental excitations which are completely different from the quasi-particles one would expect in a higher-dimensional counterpart, such as Tomonaga-Luttinger liquids and topological orders and defects. However, clean 1D electronic systems are difficult to realize experimentally, particularly magnetically ordered systems. Here, we show that the van der Waals layered magnetic semiconductor CrSBr behaves like a quasi-1D electronic material embedded in a magnetically ordered environment. The strong 1D electronic character is due to the unique combination of weak interlayer hybridization and anisotropy in effective mass and dielectric screening. The band structure and quasi-particle excitations are dominated by the Cr-S chains and a shallow 1D quantum confinement normal to these chains, manifesting in an anisotropic band with an effective electron mass ratio of meX/meY∼50. Strong quasi-particle interactions and 1D electronic character are indicated by Fano resonances from a van Hove singularity of similar strength as in metallic carbon nanotubes. The spectrally narrow excitons (1 meV) inherit the 1D character and show pronounced exciton-phonon coupling effects. Overall, CrSBr appears to be an experimentally clean candidate for the study of 1D correlated many-body physics in the presence of magnetic order.
Dylan Renaud, Daniel Rimoli Assumpcao, Graham Joe, Amirhassan Shams-Ansari, Di Zhu, Yaowen Hu, Neil Sinclair, and Marko Loncar. Submitted. “Sub-1 Volt and High-Bandwidth Visible to Near-Infrared Electro-Optic Modulators.” arXiv. Publisher's Version 2210.13521.pdf
Samantha I. Davis, Andrew Mueller, Raju Valivarthi, Nikolai Lauk, Lautaro Narváez, Boris Korzh, Andrew D. Beyer, Olmo Cerri, Marco Colangelo, Karl K. Berggren, Matthew D. Shaw, Si Xie, Neil Sinclair, and Maria Spiropulu. 12/2/2022. “Improved heralded single-photon source with a photon-number-resolving superconducting nanowire detector.” Physical Review Applied, 18, Pp. 064007. Publisher's Version
Linbo Shao, Sophie W. Ding, Yunwei Ma, Yuhao Zhang, Neil Sinclair, and Marko Loncar. 11/23/2022. “Thermal Modulation of Gigahertz Surface Acoustic Waves on Lithium Niobate.” Physical Review Applied, 18. Publisher's VersionAbstract
Surface-acoustic-wave (SAW) devices have a wide range of applications in microwave signal processing. Microwave SAW components benefit from higher quality factors and much smaller crosstalk when compared to their electromagnetic counterparts. Efficient routing and modulation of SAWs are essential for building large-scale and versatile acoustic wave circuits. Here, we demonstrate integrated thermoacoustic modulators using two SAW platforms: bulk lithium niobate and thin-film lithium niobate on sapphire. In both approaches, the gigahertz-frequency SAWs are routed by integrated acoustic waveguides, while on-chip microheaters are used to locally change the temperature, and thus, control the phase of the SAW. Using this approach, we achieve phase changes of over 720° with the responsibility of 2.6°/mW for bulk lithium niobate and 0.52°/mW for lithium niobate on sapphire. Furthermore, we demonstrate amplitude modulation of SAWs using acoustic Mach-Zehnder interferometers. Our thermoacoustic modulators can enable reconfigurable acoustic signal processing for next-generation wireless communications and microwave systems.
Di Zhu, Changchen Chen, Mengjie Yu, Linbo Shao, Yaowen Hu, C. J. Xin, Matthew Yeh, Soumya Ghosh, Lingyan He, Christian Reimer, Neil Sinclair, Franco N. C. Wong, Mian Zhang, and Marko Loncar. 11/17/2022. “Spectral control of nonclassical light using an integrated thin-film lithium niobate modulator.” Nature, Light: science & applications , 11, Pp. 327. Publisher's VersionAbstract
Manipulating the frequency and bandwidth of nonclassical light is essential for implementing frequency-encoded/multiplexed quantum computation, communication, and networking protocols, and for bridging spectral mismatch among various quantum systems. However, quantum spectral control requires a strong nonlinearity mediated by light, microwave, or acoustics, which is challenging to realize with high efficiency, low noise, and on an integrated chip. Here, we demonstrate both frequency shifting and bandwidth compression of heralded single-photon pulses using an integrated thin-film lithium niobate (TFLN) phase modulator. We achieve record-high electro-optic frequency shearing of telecom single photons over terahertz range (±641 GHz or ±5.2 nm), enabling high visibility quantum interference between frequency-nondegenerate photon pairs. We further operate the modulator as a time lens and demonstrate over eighteen-fold (6.55 nm to 0.35 nm) bandwidth compression of single photons. Our results showcase the viability and promise of on-chip quantum spectral control for scalable photonic quantum information processing.
Mengjie Yu, David Barton, Rebecca Cheng, Christian Reimer, Prashanta Kharel, Lingyan He, Linbo Shao, Di Zhu, Yaowen Hu, Hannah R. Grant, Leif Johansson, Yoshitomo Okawachi, Alexander L. Gaeta, Mian Zhang, and Marko Lončar. 11/16/2022. “Femtosecond Pulse Generation via an Integrated Electro-Optic Time Lens.” Nature. Publisher's VersionAbstract
Integrated femtosecond pulse and frequency comb sources are critical components for a wide range of applications, including optical atomic clocks1, microwave photonics2, spectroscopy3, optical wave synthesis4, frequency conversion5, communications6, lidar7, optical computing8 and astronomy9. The leading approaches for on-chip pulse generation rely on mode-locking inside microresonators with either third-order nonlinearity10 or with semiconductor gain11,12. These approaches, however, are limited in noise performance, wavelength and repetition rate tunability 10,13. Alternatively, subpicosecond pulses can be synthesized without mode-locking, by modulating a continuous-wave single-frequency laser using electro-optic modulators1,14,15,16,17. Here we demonstrate a chip-scale femtosecond pulse source implemented on an integrated lithium niobate photonic platform18, using cascaded low-loss electro-optic amplitude and phase modulators and chirped Bragg grating, forming a time-lens system19. The device is driven by a continuous-wave distributed feedback laser chip and controlled by a single continuous-wave microwave source without the need for any stabilization or locking. We measure femtosecond pulse trains (520-femtosecond duration) with a 30-gigahertz repetition rate, flat-top optical spectra with a 10-decibel optical bandwidth of 12.6 nanometres, individual comb-line powers above 0.1 milliwatts, and pulse energies of 0.54 picojoules. Our results represent a tunable, robust and low-cost integrated pulsed light source with continuous-wave-to-pulse conversion efficiencies an order of magnitude higher than those achieved with previous integrated sources. Our pulse generator may find applications in fields such as ultrafast optical measurement19,20 or networks of distributed quantum computers21,22.
Pieter-Jan Stas, Yan Qi Huan, Bartholomeus Machielse, Erik N. Knall, Aziza Suleymanzade, Benjamin Pingault, Madison Sutula, Sophie W. Ding, Can M. Knaut, Daniel R. Assumpcao, Yan-Cheng Wei, Mihir K. Bhaskar, Ralf Riedinger, Denis D. Sukachev, Hongkun Park, Marko Lončar, David S. Levonian, and Mikhail D. Lukin. 11/4/2022. “Robust multi-qubit quantum network node with integrated error detection.” Science, 378, 6619, Pp. 557-560. Publisher's VersionAbstract
Long-distance quantum communication and networking require quantum memory nodes with efficient optical interfaces and long memory times. We report the realization of an integrated two-qubit network node based on silicon-vacancy centers (SiVs) in diamond nanophotonic cavities. Our qubit register consists of the SiV electron spin acting as a communication qubit and the strongly coupled silicon-29 nuclear spin acting as a memory qubit with a quantum memory time exceeding 2 seconds. By using a highly strained SiV, we realize electron-photon entangling gates at temperatures up to 1.5 kelvin and nucleus-photon entangling gates up to 4.3 kelvin. We also demonstrate efficient error detection in nuclear spin–photon gates by using the electron spin as a flag qubit, making this platform a promising candidate for scalable quantum repeaters.
Yaowen Hu, Mengjie Yu, Neil Sinclair, Di Zhu, Rebecca Cheng, Cheng Wang, and Marko Loncar. 10/22/2022. “Mirror-induced reflection in the frequency domain.” Nature Communications, 13, Pp. 6293. Publisher's Version
Keith Powell, Jianfu Wang, Amirhassan Shams-Ansari, Bin-Kai Liao, Debin Meng, Neil Sinclair, Liwei Li, Jiangdong Deng, Marko Lončar, and Xiaoke Yi. 9/12/2022. “Optical bi-stability in cubic silicon carbide microring resonators.” Optics Express, 30, 19, Pp. 34149-34158. Publisher's VersionAbstract
We measure the photothermal nonlinear response in suspended cubic silicon carbide (3C-SiC) and 3C-SiC-on-insulator (SiCOI) microring resonators. Bi-stability and thermo-optic hysteresis is observed in both types of resonators, with the suspended resonators showing a stronger response. A photothermal nonlinear index of 4.02×10−15 m2/W is determined for the suspended resonators, while the SiCOI resonators demonstrate one order of magnitude lower photothermal nonlinear index of 4.32×10−16 m2/W. Cavity absorption and temperature analysis suggest that the differences in thermal bi-stability are due to variations in waveguide absorption, likely from crystal defect density differences throughout the epitaxially grown layers. Furthermore, coupled mode theory model shows that the strength of the optical bi-stability, in suspended and SiCOI resonators can be engineered for high power or nonlinear applications.
Yaowen Hu, Mengjie Yu, Brandon Buscaino, Neil Sinclair, Di Zhu, Rebecca Cheng, Amirhassan Shams-Ansari, Linbo Shao, Mian Zhang, Joseph M. Kahn, and Marko Loncar. 8/29/2022. “High-efficiency and broadband on-chip electro-optic frequency combs generators.” Nature Photonics, 16, Pp. 679. Publisher's VersionAbstract
Developments in integrated photonics have led to stable, compact and broadband comb generators that support a wide range of applications including communications1, ranging2, spectroscopy3, frequency metrology4, optical computing5,6 and quantum information7,8. Broadband optical frequency combs can be generated in electro-optical cavities, where light passes through a phase modulator multiple times while circulating in an optical resonator9,10,11,12. However, broadband electro-optic frequency combs are currently limited by low conversion efficiencies. Here we demonstrate an integrated electro-optic frequency comb with a conversion efficiency of 30% and an optical span of 132 nm, based on a coupled-resonator platform on thin-film lithium niobate13. We further show that, enabled by the high efficiency, the device acts as an on-chip femtosecond pulse source (336 fs pulse duration), which is important for applications in nonlinear optics, sensing and computing. As an example, in the ultrafast and high-power regime, we demonstrate a frequency comb with simultaneous electro-optic and third-order nonlinearity effects. Our device paves the way for practical optical frequency comb generators and provides a platform to investigate new regimes of optical physics that simultaneously involve multiple nonlinearities.
Yiwen Zhang, Linbo Shao, Jingwei Yang, Zhaoxi Chen, Ke Zhang, Kam-Man Shum, Di Zhu, Chi Hou Chan, Marko Loncar, and Cheng Wang. 8/23/2022. “Systematic Investigation of Millimeter-Wave Optic Modulation Performance in Thin-Film Lithium Niobate.” Photonics Research, 10, 10, Pp. 2380-2387. Publisher's VersionAbstract
Millimeter-wave (mmWave) band (30 - 300 GHz) is an emerging spectrum range for wireless communication, short-range radar and sensor applications. mmWave-optic modulators that could efficiently convert mmWave signals into optical domain are crucial components for long-haul transmission of mmWave signals through optical networks. At these ultrahigh frequencies, however, the modulation performances are highly sensitive to the transmission line loss as well as the velocity- and impedance-matching conditions, while precise measurements and modeling of these parameters are often non-trivial. Here we present a systematic investigation of the mmWave-optic modulation performances of thin-film lithium niobate modulators through theoretical modeling, electrical verifications and electro-optic measurements at frequencies up to 325 GHz. Based on our experimentally verified model, we demonstrate thin-film lithium niobate mmWave-optic modulators with a measured 3-dB electro-optic bandwidth of 170 GHz and a 6-dB bandwidth of 295 GHz. The device also shows a low RF half-wave voltage of 7.3 V measured at an ultrahigh modulation frequency of 250 GHz. This work provides a comprehensive guideline for the design and characterization of mmWave-optic modulators and paves the way toward future integrated mmWave photonic systems for beyond-5G communication and radar applications.
Raju Valivarthi, Lautaro Narváez, Samantha I. Davis, Nikolai Lauk, Cristián Peña, Si Xie, Jason P. Allmaras, Andrew D. Beyer, Boris Korzh, Andrew Mueller, Mandy Rominsky, Matthew D. Shaw, Emma E. Wollman, Panagiotis Spentzouris, Daniel Oblak, Neil Sinclair, and Maria Spiropulu. 8/15/2022. “Picosecond synchronization system for quantum networks.” Journal of Lightwave Technology, Pp. 1-7. Publisher's Version
Erik N. Knall, Can M. Knaut, Rivka Bekenstein, Daniel R. Assumpcao, Pavel L. Stroganov, Wenjie Gong, Yan Qi Huan, Pieter-Jan Stas, Bartholomeus Machielse, Michelle Chalupnik, David Levonian, Aziza Suleymanzade, Ralf Riedinger, Hongkun Park, Marko Lončar, Mihir K. Bhaskar, and Mikhail D. Lukin. 7/26/2022. “Efficient Source of Shaped Single Photons Based on an Integrated Diamond Nanophotonic System.” Physical Review Letters , 129, Pp. 053603. Publisher's Version [PDF]
Amirhassan Shams-Ansari, Guanhao Huang, Lingyan He, Zihan Li, Jeffrey Holzgrafe, Marc Jankowski, Mikhail Churaev, Prashanta Kharel, Rebecca Cheng, Di Zhu, Neil Sinclair, Boris Desiatov, Mian Zhang, Tobias J. Kippenberg, and Marko Lončar. 6/29/2022. “Reduced Material Loss in Thin-film Lithium Niobate Waveguides.” APL Photonics. Publisher's VersionAbstract
Thin-film lithium niobate has shown promise for scalable applications ranging from single-photon sources to high-bandwidth data communication systems.
Realization of the next generation high-performance classical and quantum devices, however, requires much lower optical losses than the current state of the art (~10 million). Unfortunately, material limitations of ion-sliced thin film lithium niobate have not been explored, and therefore it is unclear how high quality factor  can be achieved in this platform. Here we evaluate the material limited quality factor of thin film lithium niobate photonic platform can be as high as Q~108 at telecommunication wavelengths, corresponding to a propagation loss of 0.2 dB/m.
Linbo Shao, Di Zhu, Marco Colangelo, Dae Hun Lee, Neil Sinclair, Yaowen Hu, Peter T. Rakich, Keji Lai, Karl K. Berggren, and Marko Loncar. 6/6/2022. “Electrical Control of Surface Acoustic Waves.” Nature Electronics. Publisher's Version