Express 23, 2352623550 (2015). Thin-film lithium niobate (TFLN) based traveling-wave modulators maintain simultaneously excellent performances, including large modulation bandwidth, high extinction ratio, low optical loss, and high modulation efficiency. The photonic-crystal hole structure was patterned with ZEP-520A positive resist via electron-beam lithography, which was then transferred to the LN layer with an Ar+ plasma milling process to etch down the full 300-nm depth. Weigel, P. O. et al. the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Science 358, 630632 (2017). This mode, however, has only negligible perturbation to the dielectric mode due to distinctive spatial symmetry, thus not affecting the quality of the defect cavity mode. Lett. Nature 546, 622626 (2017). https://doi.org/10.1038/s41467-020-17950-7, DOI: https://doi.org/10.1038/s41467-020-17950-7. Laser Photonics Rev. volume11, Articlenumber:4123 (2020) When the modulation frequency is increased to 2.0GHz greater than the cavity linewidth, the cavity is too slow to follow the electro-optic modulation, which results in the frequency conversion of photons into sidebands with frequency separation equal to the modulation frequency. 314, 317 (2014). 101, 151117 (2012). To characterize the performance of high-speed modulation, the majority of the modulated light output was amplified by an erbium-doped fiber amplifier to boost the power, passed through a bandpass filter to remove the amplifier noise, and was then detected by a high-speed detector (New Focus 1024). Google Scholar. In most cases, lasers are stand-alone devices, external to the modulators, making the whole system more expensive and less stable and scalable. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate. InGaAs/InGaAsP MQW electroabsorption modulator integrated with a DFB laser fabricated by band-gap energy control selective area MOCVD. We have applied a voltage of 25V to the device (not shown in the figure) and did not observe any degradation. PSI offers ultra-high-speed lithium niobate phase modulators. Quant. Zhou, B., Li, E., Bo, Y. Electron. Electro-optically (EO) tunable metasurfaces have received considerable attention owing to their capability for dynamic light field control. g Simulated optical mode field profile of the second-order TE-like cavity mode \({\mathrm{{TE}}}_{01}^{1}\). 13, 1800228 (2019). Correspondence to 28, 736739 (2016). 8 shows that there are considerable rooms to further improve the EOM performance. Nguyen, H. C., Hashimoto, S., Shinkawa, M. & Baba, T. Compact and fast photonic crystal silicon optical modulators. To show this phenomenon, we applied a sinusoidal RF signal at a certain frequency to the EOM and monitored the transmission spectrum of the device by scanning laser back and forth across the cavity resonance. 7, 10031013 (2019). To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. 16, 18 (2018). Wooten, E. L. et al. Numerical simulations show that the device exhibits a small capacitance C of C=~22fF, which is more than one order of magnitude smaller than other LN EOMs1,13,14,15,16,17,18,19,20,21,22,23,24,25,26. Liang, H., Luo, R., He, Y., Jiang, H. & Lin, Q. In summary, we have demonstrated high-speed LN EOMs with a broad modulation bandwidth of 17.5GHz, a significant tuning efficiency up to 1.98GHzV1, and an electro-optic modal volume as small as 0.58m3. 8b. 1 Half-wave voltages of devices with different active lengths. Its low operating voltage makes it convenient to use a function generator as the driver. Therefore, the electrodes can be shrunk to 103m2, which would reduce the capacitance considerably to ~0.27fF (~1.0fF if including the integrated wires36), according to our FEM simulations. Laser. Express 27, 1873118739 (2019). The metal electrode layer (10nm Ti/500 nm Au) was deposited by an electron-beam evaporator and the electrode structure was formed by a lift-off process via ZEP-520A. Enhanced electro-optic lithium niobate photonic crystal wire waveguide on a smart-cut thin film. ADS A variety of approaches have been employed for electro-optic modulation, such as carrier plasma dispersion6,7, electro-absorption8,9, and Pockels effect1,10, the latter of which is particularly interesting since the Pockels effect offers an ultrafast and pure refractive-index modulation over an extremely broad optical spectrum while without introducing extra loss. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate. Nature 528, 534538 (2015). ADS Laser Photonics Rev. To show the electro-optic tuning property, we applied a DC voltage to the chip and monitored the cavity transmission spectrum of the \({\mathrm{{TE}}}_{01}^{0}\) mode. Nature 562, 101104 (2018). Our scalable modulator devices could provide cost-effective, low-power and ultra-high-speed solutions for next-generation optical communication networks and microwave photonic systems. Recently, there have been significant advance in high-Q LN photonic-crystal nanoresonators43,44,45,46, which led to the demonstration of intriguing phenomena and functionalities such as photorefraction quenching43, harmonic generation44, piezo-optomechanics45, and all-optical resonance tuning46. Appl. You are using a browser version with limited support for CSS. Single-chip microprocessor that communicates directly using light. The detector output was recorded either by a microwave network analyzer (Keysight N5235B) for characterizing the modulation bandwidth or by a sampling oscilloscope module (Keysight 54754A) to record the eye diagram of the switching signal. Reference [18] has recently emerged as a promising approach to realize integrated EO modulators with stronger optical connement and high EO efciencies while occupying a smaller footprint [4], [19]-[22]. Jin, S., Xu, L., Zhang, H. & Li, Y. LiNbO3 thin-film modulators using silicon nitride surface ridge waveguides. Optica 6, 860863 (2019). Photon. Opt. The device exhibits a resonance at 1554.47nm, which corresponds to the fundamental TE-like cavity mode \({\mathrm{{TE}}}_{01}^{0}\) (Fig. We expect that these optimization would significantly improve the energy efficiency of the LN photonic-crystal EOM, further decreasing the switching energy down to sub-femtoJoule level. Lithium Niobate Nonlinear Thermal Waveguide MODE Automation API Nonlinear Optics Photonic Integrated Circuits - Active Computing Second-harmonic generation (SHG) in a Lithium Niobite - LiNbO3 (LNO) nanophotonic waveguide is studied using temperature modulation to achieve efficient phase matching. b Zoom-in image of the photonic-crystal resonator and electrodes, corresponding to the dashed rectangular region in a. c Further zoom-in image showing the detailed structure of the photonic-crystal defects cavity, corresponding to the dashed rectangular region in b. We thank J. Khan for discussions on the LN platform, H. Majedi for help with the equipment, and C. Reimer, S. Bogdanovi, L. Shao and B. Desiatov for feedback on the manuscript. 3, e173 (2014). conceived the experiment. ADS 1f). High-Q lithium niobate microdisk resonators on a chip for efficient electro-optic modulation. 6a). Laser Photon. Sign up for the Nature Briefing newsletter what matters in science, free to your inbox daily. The energy efficiency of the LN photonic-crystal EOM can be further improved since our current devices are not optimized. Internet Explorer). In this research, we used all the nano-fabrication tricks and techniques learned from previous developments in integrated lithium niobate photonics to overcome those challenges and achieve the goal of integrating a high-powered laser on a thin-film lithium niobate platform., Harvards Office of Technology Development. Silicon optical modulators. increased the EO modulation efficiency to a voltage-length product of 1.75 Vcm using a shallowly etched lithium niobate waveguide. Lithium niobate photonic-crystal electro-optic modulator, https://doi.org/10.1038/s41467-020-17950-7. C.W., M.Z., X.C. Such a supercell of metasurface is constructed by two kinds of finite-sized arrays possessing different topological properties via the generalized two-dimensional (2D . For all the recent advances in integrated lithium niobate photonic circuits from frequency combs to frequency converters and modulators one big component has remained frustratingly difficult to integrate: lasers. Here, we present a heterogeneously integrated EOM based on the lithium niobate-on-insulator (LNOI) platform. Rep. 7, 46313 (2017). Tzuang, L. D., Fang, K., Nussenzveig, P., Fan, S. & Lipson, M. Non-reciprocal phase shift induced by an effective magnetic flux for light. https://doi.org/10.1038/s41586-018-0551-y, Complementary Metal Oxide Semiconductor (CMOS). 34, 29412951 (2016). A variety of approaches have been explored for this purpose, including plasmonic structures29,30, slotted dielectric waveguides10, photonic micro-/nanoresonators6,31, etc. Provided by the Springer Nature SharedIt content-sharing initiative. Article The modulators enable efficient electro-optic driving of high-Q photonic cavity modes in both adiabatic and non-adiabatic regimes, and allow us to achieve electro-optic switching at 11 Gb s1 with a bit-switching energy as low as 22 fJ. It, however, degrades considerably the optical Q of the cavity (Fig. Hybrid silicon photonic-lithium niobate electro-optic MachZehnder modulator beyond 100 GHz. The researchers combined the laser with a 50 gigahertz electro-optic modulator in lithium niobate to build a high-power transmitter. The research is published in the journal Optica. & Capmany, J. Optical modulators, using acousto-optic, magneto-optic or electro-optic effects, as the principal components for external modulation of lightwaves, have presently played the important role in modern long-haul ultra-high speed optical communications and photonic signal processing systems. Fortier, T. M. et al. Now, researchers from the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) in collaboration with industry partners at Freedom Photonics and HyperLight Corporation, have developed the first fully integrated high-power laser on a lithium niobate chip, paving the way for high-powered telecommunication systems, fully integrated spectrometers, optical remote sensing, and efficient frequency conversion for quantum networks, among other applications. Poberaj, G., Hu, H., Sohler, W. & Gnter, P. Lithium niobate on insulator (LNOI) for micro-photonic devices. 4, 518526 (2010). LiNbO. Loncar is a cofounder of HyperLight Corporation, a startup which was launched to commercialize integrated photonic chips based on certain innovations developed in his lab. Qiang Lin. Top. Rao, A. et al. The device also exhibits a second-order TE-like cavity mode \({\mathrm{{TE}}}_{01}^{1}\) (Fig. 100GHz siliconorganic hybrid modulator. 1f), so as to take the advantage of the largest electro-optic component r33 of LN. A 10-Gbit/s lithium niobate intensity module provides chirp-free modulation at 1550 nm. Lett. Appl. Advanced optical modulation formats. Express 26, 2372823739 (2018). The flexible electro-optic modulation shown here may offer a convenient method for controlling the spectrotemporal properties of photons inside the cavity and for creating exotic quantum states48 that are crucial for quantum photonic applications. Ozaki, J., Ogiso, Y. Sun, C. et al. 1a), where an injector section (Fig. Winzer, P. J. 1f. volume562,pages 101104 (2018)Cite this article. Therefore, we expect our devices to have much higher energy efficiency, as will be shown in the following sections. Lithium niobate (LiNbO3) modulator can be regarded as a technology platform that can add values to optical networks and is suitable for addressing many issues. http://www.fujitsu.com/jp/group/foc/en/products/optical-devices/100gln/, Eospace 2017 Advanced Products. Miller, D. A. Here we report high-speed and energy-efficient LN photonic-crystal EOMs, which exhibits a tiny electro-optic modal volume of only ~0.58m3, the smallest among all high-speed LN EOMs ever reported1,13,14,15,16,17,18,19,20,21,22,23,24,25,26, to the best of our knowledge. Nature 556, 483486 (2018). Long haul telecommunication networks, data center optical interconnects, and microwave photonic systems all rely on lasers to generate an optical carrier used in data transmission. Single-chip microprocessor that communicates directly using light. Phys. When the EOM is driven at a modulation frequency of 600MHz much smaller than the cavity linewidth of 1.4GHz, increasing the driving power simply broadens the transmission spectrum into one with two shallow side lobes, as shown in Fig. 8b), which, however, might sacrifice the optical Q due to metallic losses. Chen, X. et al. Nat. Quantum Electron. In the meantime, to ensure continued support, we are displaying the site without styles Open Access Velocity matching can be achieved with an oxide thickness of about 4,700nm. In the meantime, to ensure continued support, we are displaying the site without styles Appl. For example, the capacitance of our device can be significantly decreased since the majority of the metallic parts in the current devices are used for coupling the RF driving signal, which can be removed in a future on-chip integration design. Li, M. et al. Express 26, 220232 (2018). Light Sci. The cavity mode exhibits an extremely small electro-optic modal volume of 1.52(/n)3~0.58m3 (where n is the refractive index of LN). Photon. As an example application, we demonstrate electro-optic switching of non-return-to-zero (NRZ) signal at a rate of 11Gbs1, with a switching energy as low as 22fJ per bit that is more than one order of magnitude smaller than other LN EOMs1,13,14,15,16,17,18,19,20,21,22,23,24,25,26. 2, red box) is used primarily for impedance matching to the large metal pad for probe contact, which can be decreased to 3m for a fully on-chip operation36. Thank you for visiting nature.com. Photon. After the residue removal, we used diluted hydrofluoric acid to undercut the buried oxide layer to form a suspended photonic-crystal membrane structure (Fig. Google Scholar. For the application of high-speed electro-optic switching, our simulations show that the electrode-waveguide spacing can be decreased to 1.5m for an optical Q of ~5000 (corresponding to a modulation bandwidth of ~45GHz), which will improve the modulation efficiency to 2.38GHzV1 (simulation details in Methods). For direct CMOS driving, the RF amplifier is bypassed. The blue column shows another design with broader bandwidth and enhanced electro-optic coupling. Lu, H. et al. Chen, X. et al. These authors contributed equally: Cheng Wang, Mian Zhang, John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, USA, Cheng Wang,Mian Zhang,Maxime Bertrand,Amirhassan Shams-Ansari&Marko Lonar, Department of Electronic Engineering, City University of Hong Kong, Kowloon, Hong Kong, China, Xi Chen,Sethumadhavan Chandrasekhar&Peter Winzer, LP2N, Institut dOptique Graduate School, CNRS, University of Bordeaux, Talence, France, Department of Electrical Engineering and Computer Science, Howard University, Washington, DC, USA, You can also search for this author in Integrating high-performance plug-and-play lasers would significantly reduce the cost, complexity, and power consumption of future communication systems, said Amirhassan Shams-Ansari, a graduate student at SEAS and first author of the study. carried out the device characterization. supervised the project. High-performance hybrid silicon and lithium niobate Mach Zehnder modulators for 100 Gbit s1 and beyond. Lithium niobate photonic-crystal electro-optic modulator. Integrated lithium niobate photonics is a promising platform for the development of high-performance chip-scale optical systems, but getting a laser onto a lithium niobate chip has proved to be one of the biggest design challenges, said, , the Tiantsai Lin Professor of Electrical Engineering and Applied Physics at SEAS and senior author of the study. Nat. We realize an intensity modulator of 12.5 mm long modulation section, which exhibits a low half-wave voltage of 1.7 V and a large 3 dB modulation bandwidth of >70 GHz. Xinlun Cai, of Sun Yat -sen University, led a team that designed and fabricated a thin-film lithium niobate (TFLN) dual polarization in-phase and quadrature (DP-IQ) modulator, which sets new world . B. Attojoule optoelectronics for low-energy information processing and communications. Google Scholar. npj Quantum Information Zhang, X. et al. Boes, A., Corcoran, B., Chang, L., Bowers, J. Res. 1e) to achieve a critical coupling. Streshinsky, M. et al. High-quality lithium niobate photonic crystal nanocavities. Wood, M. G. et al. Rouvalis, E. Indium phosphide based IQ-modulators for coherent pluggable optical transceivers. Sun, C. et al. In this research, we used all the nano-fabrication tricks and techniques learned from previous developments in integrated lithium niobate photonics to overcome those challenges and achieve the goal of integrating a high-powered laser on a thin-film lithium niobate platform.. Further increase of the modulation frequency shifts apart the two side lobes accordingly, with amplitude decreased, while the position of the center lobe remains unchanged, as expected from the non-adiabatic driving. and M.L. Integrated microwave photonics. IEEE Photonics Technol. Opt. a, Set-up for measuring the modulator electro-optic responses from 35GHz to 100GHz. On chip, the lasers sit in small wells or trenches etched into the lithium niobate and deliver up to 60 milliwatts of optical power in the waveguides fabricated in the same platform. ac, Normalized optical transmission of the 20-mm (a), 10-mm (b) and 5-mm (c) device as a function of the applied voltage, showing half-wave voltages of 1.4V, 2.3V and 4.4V, respectively. As shown in Fig. We achieve this by engineering the microwave and photonic circuits to achieve high electro-optical efficiencies, ultra-low optical losses and group-velocity matching simultaneously. supervised the project. Extended Data Fig. Optica 6, 845853 (2019). 1e), with the lattice constant varying from 450 to 550nm, is designed and placed in front of the left mirror to reduce the coupling loss. Recently, heterogeneously integrated silicon and lithium niobate (Si/LN) optical modulators have demonstrated attractive overall performance in terms of optical loss, drive voltage, and modulation bandwidth. This is a typical signature of resonance modulation in the sideband-unresolved regime, where the cavity resonance follows adiabatically the electric driving signal in a sinusoidal fashion, resulting in a broadened average transmission spectrum (Fig. & Smith, B. J. Bandwidth manipulation of quantum light by an electro-optic time lens. Optica 6, 14981505 (2019). Figure4a shows the transmission spectrum of an EOM when the laser is scanned in the telecom band. Ogiso, Y. et al. Topics: 6, 488503 (2012). Azadeh, S. S. et al. Nature Communications (Nat Commun) Integrated lithium niobate photonics is a promising platform for the development of high-performance chip-scale optical systems, but getting a laser onto a lithium niobate chip has proved to be one of the biggest design challenges, saidMarko Loncar, the Tiantsai Lin Professor of Electrical Engineering and Applied Physics at SEAS and senior author of the study. Jian, J. et al. The bit-switching energy for NRZ signal is given by \(\frac{1}{4}C{V}_{{\rm{pp}}}^{2}\) (ref. Here, we make an important step towards miniaturizing functional components on this platform, reporting high-speed LN electro-optic modulators, based upon photonic crystal nanobeam resonators. 35, 411417 (2017). Express 21, 3035030357 (2013). B 97, 104105 (2018). IEEE J. Quantum Electron. 6, 6982 (2000). The gray regions represents the 3-dB bandwidth limit for two devices, respectively, and the dashed line indicates the 3-dB limit of S21. Loncar and his team used small but powerful distributed feedback lasers for their integrated chip. The extinction ratio can be significantly improved by further optimization of the photonic-crystal mirrors (Fig. Lithium niobate piezo-optomechanical crystals. NTT Tech. Wang, C., Zhang, M., Stern, B., Lipson, M. & Loncr, M. Nanophotonic lithium niobate electro-optic modulators. Here, we fabricate a multimode microring resonator with an intrinsic Q of 6 106, which exhibits a propagation loss 50 times lower than that of a single-mode LN microring fabricated under the same process. In 2015 Optical Fiber Communications Conference and Exhibition 13 (2015); https://doi.org/10.1364/OFC.2015.Th4E.3. On the other hand, the full-swing extinction ratio of the EOMs is primarily determined by the external coupling of light to the modulator cavity. The measured electrical BER is 3.6105, limited by the signal distortion from the electronic circuit. Reed, G. T., Mashanovich, G., Gardes, F. Y. Opt. 1541959. and JavaScript. In the past decade, photonic-crystal EOMs have been developed on various material platforms such as silicon32,33,34, GaAs35, InP36, polymers37,38, ITO39, etc. In 2015 IEEE Compound Semiconductor Integrated Circuit Symposium 14 (2015); https://doi.org/10.1109/CSICS.2015.7314513, Letal, G. et al. Shen, Y. et al. Express 26, 1481014816 (2018). Its a building block that can be integrated into larger optical systems for a range of applications, in sensing, lidar, and data telecommunications.. 1 Ultra-high-linearity integrated lithium niobate electro-optic modulators Hanke Feng1, Ke 1Zhang1, Wenzhao Sun , Yangming Ren2,3, Yiwen Zhang1, Wenfu Zhang2,3 & Cheng Wang1* 1Department ofElectricalEngineering&StateKeyLaboratory TerahertzandMillimeterWaves, City University of Hong Kong, Kowloon, Hong Kong, China 2Institute of Optics and Precision Mechanics, Chinese Academy of Sciences . They are also expected to be building blocks for emerging applications such as quantum photonics5,6 and non-reciprocal optics7,8. The modulators enable efficient electro-optic driving of high-Q photonic cavity modes in both adiabatic and non-adiabatic regimes, and allow us to achieve electro . Photon. b Same as a but with a modulation frequency of 2.0GHz. Proc. To obtain Opt. Photon. The elliptical hole has dimensions of hx=270nm and hy=490nm, and a fully etched depth of 300nm. Figure7a shows the electro-optic modulation response of the device (blue curve), which exhibits a 3-dB modulation bandwidth up to around 17.5GHz. Harvards Office of Technology Developmenthas protected the intellectual property arising from the Loncar Labs innovations in lithium niobate systems. b, c Electro-optic tuning efficiency and optical quality factor of the device as a function of Gap and tw, simulated by the FEM method. Opt. To date, it remains an open challenge in realizing a high-speed and energy-efficient modulator at the wavelength scale on the monolithic LN platform. PubMedGoogle Scholar. HR00112090012. CAS Boyd, R. W. Nonlinear Optics (Academic, Cambridge, 2003). Lee, M. et al. Express 23, 2274622752 (2015). Nature (Nature) Increasing the electrical driving power now does not perturb the positions of the resonance dips, but rather changes their relative magnitudes since the magnitudes of the created sidebands depends on the driving amplitude48. That highlighted in blue indicates the large metal pad used for contacting the RF probe. Nat. Nat. PubMed Google Scholar. Li, M., Liang, H., Luo, R., He, Y. The modulator is designed to be used in externally modulated fiberoptic transmitters for supertrunking of digitized cable-TV signals as well as for long-haul transmission of OC-192 data. & Fathpour, S. Compact lithium niobate electrooptic modulators. e Lattice constant a as a function of position, which is optimized for low insertion loss together with high radiation-limited optical Q. f Top view of the FEM-simulated optical mode field profile of the fundamental TE-like cavity mode \({\mathrm{{TE}}}_{01}^{0}\). Wooten, E. L. et al. This value primarily reaches the photon-lifetime limit of the EOM cavity (~11ps), as the electrode circuit has much broader spectral response as indicated by the flat S11 reflection spectrum shown in the inset of Fig. Appl. With these devices, we are able to realize efficient driving of the optical mode in both adiabatic sideband-unresolved and non-adiabatic sideband-resolved regimes, and to observe the transition in between. Lu, H. et al. 42.70.a. C.W. The individual column at the left of each plot indicates the case when tw=0m and gap=2.5m, for a device with full surrounding air cladding. Express 22, 2862328634 (2014). 4, e255 (2015). In this contribution, we simulate, design, and experimentally demonstrate an integrated optical isolator based on spatiotemporal modulation in the thin-film lithium niobate on an insulator waveguide platform. Thorlabs free-space electro-optic (EO) amplitude and phase lithium niobate modulators combine our experience with crystal growth and electro-optic materials. CAS This work was performed in part at the Cornell NanoScale Facility, a member of the National Nanotechnology Coordinated Infrastructure (National Science Foundation, ECCS-1542081). The left inset shows the orientation of the LN crystal where the optical axis is along the z direction. https://www.thorlabs.com/newgrouppage9.cfm?objectgroup_id=3948. Wang, C. et al. The electrodes are designed to have a length of 30m to ensure a full coverage of the applied electric field over the entire photonic-crystal structure. Express 21, 2700327010 (2013). Photonics 4, 518526 (2010). 100G/400G LN Modulator. a Recorded scattering parameter S21 for two devices with optical Q of ~14,000 (blue curve) and ~20,000 (orange curve), respectively. Waveguide-integrated, ultralow-energy GeSi electro-absorption modulators. Status and potential of lithium niobate on insulator (LNOI) for photonic integrated circuits. Here we overcome these limitations and demonstrate monolithically integrated lithium niobate electro-optic modulators that feature a CMOS-compatible drive voltage, support data rates up to 210. a is the lattice constant. This can be changed simply by engineering the photonic-crystal mirror on the other side to function as the output port. 8b, c. However, Fig. Witmer, J. D. et al. We believe this is the first LN EOM ever reported with such combined device characteristics and modulation performance. c Detailed spectrum (blue) with RF driving signal at 2.0GHz with a power of 16mW. Technol. Scaling an EOM down to a small footprint would reduce the device capacitance and thus decrease the switching energy27,28, which is indispensable for all practical applications. The sum of all gray curves is showed in red, which is fitted by the theory. It has a bias control section that integrates with a tap monitor for stable operation. Wang, C., Zhang, M., Chen, X. et al. Power efficiency is crucial for the application of electro-optic modulator (EOM), which depends sensitively on the physical size of the device27. A review of lithium niobate modulators for fiber-optic communications systems. Rao, A. M.L. J. Lightwave Technol. 6a, with a broadened spectral linewidth dependent on the driving power.