Electro-optic Effect Of Lithium Niobate Research Articles

Reconfigurable AWGR based on LNOI with a tunable central wavelength and bandwidth used in elastic optical networking.

Elastic optical networking introduces elasticity and adaptation into the optical domain, which highly depends on reconfigurable optical devices. In this paper, a tunable 4×4 arrayed waveguide grating router based on lithium niobate on insulator is designed. By using the electro-optic effect of lithium niobate, we design electrode regions with specific shapes in the array waveguide region to realize the tuning of the routing wavelength and bandwidth of the third output channel. The designed arrayed waveguide grating router (AWGR) has a dense channel spacing of 0.8nm, and the minimum insertion loss is 2.3dB. Experiments show that the tuning range of the central wavelength can reach 3.2nm, and the 3dB bandwidth can be expanded from 0.2 to 0.6nm.

Tunable Ultranarrowband Grating Filters in Thin-Film Lithium Niobate

Several applications in modern photonics require compact on-chip optical filters with a tailored spectral response. However, achieving subnanometric bandwidths and high extinction ratios is particularly challenging, especially in low-footprint device formats. Phase-shifted Bragg gratings implemented by the sidewall modulation of photonic nanowire waveguides are a good solution for on-chip narrowband operation with reasonable requirements in fabrication and scalability. In this work we report on their implementation and optimization in thin film lithium niobate, a photonic platform that affords reconfigurability by exploiting electro-optic effects. The phase-shifted Bragg grating filters have a footprint smaller than 1 μm × 1 mm and operate at telecom wavelengths, featuring extinction ratios up to 25 dB. We demonstrate transmission bandwidths as narrow as 14.4 pm (Q = 1.1 × 105) and 8.8 pm (Q = 1.76 × 105) in critically coupled structures and multiwavelength Fabry–Perot configurations, respectively, in full agreement with theoretical predictions. Moreover, by taking advantage of the strong electro-optic effect in lithium niobate, in combination with the tight light confinement of nanophotonic wires and the ultranarrow spectral resonances of optimized grating structures, we demonstrate an electric tunability in peak wavelength and transmission of 25.1 pm/V and 2.1 dB/V, respectively, and a 10.5 dB contrast at CMOS voltages. The results pave the way for reconfigurable narrowband photonic filters with a small footprint and low consumption, to be exploited toward on-chip quantum and nonlinear optics, as well as optical sensing and microwave photonics.

Tunable dual-channel ultra-narrowband Bragg grating filter on thin-film lithium niobate.

We demonstrate dual-channel phase-shifted Bragg grating filters in the telecom band on thin-film lithium niobate. These integrated tunable ultra-narrow linewidth filters are crucial components for optical communication and sensing systems, as well as future quantum-photonic applications. Thin-film lithium niobate is an emerging platform suitable for these applications and has been exploited in this Letter. The demonstrated device has an extinction ratio of 27 dB and two channels with close linewidths of about 19 pm (quality factor of ${8} \times {{10}^4}$), separated by 19 GHz. The central wavelength could be efficiently tuned using the high electro-optic effect in lithium niobate with a tuning factor of 3.83 pm/V. This demonstration can be extended to tunable filters with multiple channels, along with desired frequency separations and optimized tunability, which would be useful for a variety of complex photonic integrated circuits.

LNOI waveguide grating based true time delay line for tunable bandpass microwave photonic filter

A precisely tunable true time delay line (TTDL) based on lithium niobate on insulator waveguide grating is proposed. Utilizing the electro-optic effect of lithium niobate, active tuning of reflected wavelength and time delay can be realized. The numerical simulation results show that, with the optimized grating structure and flexible electrode distribution, wide tuning range and high tuning accuracy of time delay can be achieved by simply controlling the charging position of the electrodes. This TTDL is applied to a tunable bandpass microwave photonic filter (TBMPF), which using PM-IM conversion to suppressed dc signal to achieve bandpass. In the TBMPF, the TTDL plays the role of introducing the dispersion for PM-IM conversion, time delay between the taps and tuning of central frequency. This TTDL can reduce the system complexity and cost of microwave photonic filter.

Optical arbitrary waveform generation based on an array of tunable apodized waveguide Bragg gratings

A structure of optical arbitrary waveform generation (OAWG) based on an array of tunable apodized waveguide Bragg gratings (WBGs) is proposed. The WBGs array on lithium niobate (LN) consists of several apodized gratings, waveguides and electrodes deposited on both sides of gratings and waveguides. The properties of OAWG are analyzed using transfer matrix method. Due to the electro-optic effect of LN, the amplitude and phase of incident light source are controlled via adjusting the voltages on electrodes. Consequently, the optical pulses with different waveforms are obtained and the amplitude is linearly tuned. In addition, voltages compensating amplitude and phase distortion are demonstrated.

AWG optical filter with tunable central wavelength and bandwidth based on LNOI and electro-optic effect

In this paper, an Arrayed-Waveguide Grating (AWG) filter based on Lithium Niobate on Insulator (LNOI) is designed to achieve tunable optical filtering by adjusting the refractive index of the waveguide area. By using the electro-optic effect of Lithium Niobate (LN), two triangular model electrode areas are designed to tune the central wavelength and bandwidth of the filter respectively. The adjustment in refractive index of two areas are relatively independent. By optimizing the structural parameters of the AWG, better tuning capability of bandwidth is achieved while maintaining the tuning range of central wavelength. Simulated by beam propagation method, excellent tuning capability of central wavelength and bandwidth can be obtained by applying a low voltage to the two electrode areas we designed.

Polarization mode converters in ZnO-diffused LiNbO3 waveguides

The linear electro-optic effect in lithium niobate is capable of realizing a variety of polarization transformations, including TE-to-TM and left-to-right circular polarization conversion. Several types of devices have been demonstrated in Ti-diffused waveguides. LiNbO3 devices have historically been based on either Ti-diffused or proton-exchanged waveguides. The proton-exchanged waveguides only guide light polarized along the optic axis, and therefore, are not applicable to polarization transforming devices. Zinc oxide diffusion is an alternative waveguide fabrication technology that guides both e- and o-waves with much higher power-handling capability than Ti : LiNbO3 waveguides. ZnO : LiNbO3 waveguides exhibit a highly circular mode field with lower anisotropy than Ti-diffused waveguides. We report the design, fabrication, and testing of ZnO : LiNbO3 devices for polarization mode conversion.

The reconfigurable dispersion compensator based on LNOI waveguide grating

In this paper, we propose a novel reconfigurable optical dispersion compensator achieved by waveguide grating and electro-optic effect of lithium niobate on insulator. Reconfigurable compensation is attained by controlling the voltage of the electrodes on waveguide grating. The measured bit error rate in the system is below 10−10 in a 40 Gbit/s quadrature phase shift keying transmission system.

Tunable arrayed waveguide grating optical filter based on lithium niobate-on-insulator and electro-optic effect

A flexible optical filter based on tunable arrayed waveguide grating (AWG) with triangular-like model electrodes is designed on lithium niobate-on-insulator. Using the electro-optic effect of lithium niobate, the 10 − 3 increase of the waveguides refractive index could be achieved with a 4.348-V effective external voltage. The tunable range of the central wavelength of AWG can reach 3.8 nm and the 3-dB bandwidth is about 0.43 nm.

Design of multi-wavelength tunable filter based on Lithium Niobate

A multi-wavelength tunable filter is designed. It consists of multiple waveguides among multiple waveguide gratings. A pair of electrodes were placed on both sides of each waveguide. The tunable filter uses the electro-optic effect of Lithium Niobate to tune the phase caused by each waveguide. Consequently, the wavelength and wavelength spacing of the filter are tuned by changing external voltages added on the electrode pairs. The tunable property of the filter is analyzed by phase matching condition and transfer-matrix method. Numerical results show that not only multiple wavelengths with narrow bandwidth are tuned with nearly equal spacing by synchronously changing the voltages added on all electrode pairs, but also the number of wavelengths is determined by the number of phase shifts caused by electrode pairs. Furthermore, due to the electro-optic effect of Lithium Niobate, the tuning speed of the filter can reach the order of ns.

Design of transmission gate using electro-optic effect of lithium niobate based Mach–Zehnder interferometers

Optical integrated circuits for computing and information processing could overcome the speed limitations of semiconductor electronics. However, in photonics, very few fundamental building blocks equivalent to those used in multi-functional electronic circuits exist. In this paper, transmission gate based on electro-optic effect inside lithium niobate based Mach–Zehnder interferometers (MZI) is described. Transmission gates are typically used as building blocks for logic circuitry in integrated circuit design. It is a combination of NMOS and PMOS transistors. Lithium niobate based MZI has a phenomenal competence to switching optical signal to a desired output port. Here, proposed device is elucidated with the help of mathematical description and thereafter simulation using MATLAB. 2 \(\times \) 1 multiplexer is also designed using proposed transmission gate. The study is verified using beam propagation method.

Design of optical reversible logic gates using electro-optic effect of lithium niobate based Mach-Zehnder interferometers.

In recent years reversible logic has come as a promising solution in the optical computing domain. In reversible gates, there is one-to-one mapping between input and output, causing no loss of information. Reversible gates are useful for application in low power complementary metal-oxide semiconductors, with less dissipation, and in quantum computing. These benefits can be utilized by implementing reversible gate structures in the optical domain. In this paper, basic reversible Feynman and Fredkin logic gates using a lithium niobate based Mach-Zehnder interferometer are proposed. The different applications utilizing the proposed structures are also explained in this study.

High speed optical 4-bit twisted ring counter using electro-optic effect of Mach-Zehnder interferometer

A 4-bit twisted ring counter is demonstrated utilizing the electro-optic effect of lithium niobate based Mach-Zehnder Interferometer (MZI). The MZI structures working on the principle of electro-optic effect show the powerful ability to switch the optical signal from one output port to the other. The theoretical description along with appropriate mathematical formulation is provided and the proposed device is analysed using beam propagation method. The proposed scheme will be helpful in optical signal processing and packet switching networks.

Intense transient electric field sensor based on the electro-optic effect of LiNbO3

Intense transient electric field measurements are widely applied in various research areas. An optical intense E-field sensor for time-domain measurements, based on the electro-optic effect of lithium niobate, has been studied in detail. Principles and key issues in the design of the sensor are presented. The sensor is insulated, small in size (65 mm × 15 mm × 15 mm), and suitable for high-intensity (<801 kV/m) electric field measurements over a wide frequency band (10 Hz–10 MHz). The input/output characteristics of the sensor were obtained and the sensor calibrated. Finally, an application using this sensor in testing laboratory lightning impulses and in measuring transient electric fields during switch-on of a disconnector confirmed that the sensor is expected to find widespread use in transient intense electric field measurement applications.

An optical synchronous up counter based on electro-optic effect of lithium niobate based Mach–Zehnder interferometers

Sequential circuits have the ability to store, retain and then retrieve information when needed at a later time. They act as storage elements and have memory. However, due to ever increasing demand of data rate, already existing electronic signal processing devices have become obsolete due to their large latency. To overcome the existing bottleneck, a 4-bit synchronous up counter using electro-optic effect of Mach–Zehnder interferometer has been proposed. The study is carried out by simulating the proposed device with beam propagation method.

Design of universal shift register based on electro-optic effect of LiNbO3 in Mach–Zehnder interferometer for high speed communication

An optical universal shift register has been demonstrated based on the electro-optic effect of lithium niobate (LiNbO3) in Mach–Zehnder interferometer (MZI), which can be used as a building block for optical computing and optical signal processing systems. The proposed device comprises of two serially connected optical D flip-flops and two multiplexers. Each optical D flip-flop consists out of three MZIs sharing a single clock pulse. The two cascaded multiplexers are controlled by the electric pulses in order to perform the bidirectional shifting and parallel loading operation of optical pulses. The pulse shifting behavior is analyzed using Beam propagation method and verified with the help of MATLAB simulations and function table.

Control of the electro-optic effect in lithium niobate using polarization-reversed structures

Control of the electro-optic effect in lithium niobate using polarization-reversed structures

Electro-optic fringe locking and photometric tuning using a two-stage Mach–Zehnder lithium niobate waveguide for high-contrast mid-infrared interferometry

b Universite de Franche-Comte, FEMTO-ST, Besancon 25030, France Abstract. We present an optimization process to improve the rejection ratio in integrated beam combiners by locking the dark fringe and then monitoring its intensity. The method proposed here uses the electro-optic effect of lithium niobate in order to lock the dark fringe and to real-time balance the photometric flux by means of a two- stage Mach-Zehnder interferometer waveguide. By applying a control voltage on the output Y-junction, we are able to lock the phase and stay in the dark fringe, while an independent second voltage is applied on the first- stage intensity modulator, to finely balance the photometries. We have obtained a rejection ratio of 4600 (36.6 dB) at 3.39 μm in transverse electric polarization, corresponding to 99.98% fringe contrast, and shown that the system can compensate external phase perturbations (a piston variation of 100 nm) up to around 1 kHz. We also show the preliminary results of this process on wide-band modulation, where a contrast of 38% in 3.25- to 3.65-μm spectral range is obtained. These preliminary results on wide-band need to be opti- mized, in particular, for reducing scattered light of the device at the Y-junction. We expect this active method to be useful in high-contrast interferometry, in particular, for astronomical spatial projects actually under study.

The superprism effect in lithium niobate photonic crystals for ultra-fast, ultra-compact electro-optical switching

We numerically analyze ultra-refraction and slow-light in lithium niobate photonic crystals in order to investigate and then optimize the efficiency of a tunable photonic crystal superprism. In contrast to a passive superprism 1-to-N demultiplexer, we describe a tunable bandpass filter with only three output ports. The electro-optic effect in lithium niobate is used to achieve tunability, with the filter bandwidth shifting in wavelength as the refractive index of the superprism is modified by an externally applied electric field. Such a device could be used to realize a compact and fast wavelength multiplexer/demultiplexer for telecommunications or optical interconnect applications. We calculate constant frequency dispersion contours (plane-wave expansion) to identify initial configurations that show significant ultra-refraction, and verify the expected behavior of light propagation inside the structure using 2D FDTD (finite difference time domain) simulations. We show that the voltage requirements of such an electro-optically tunable superprism could potentially be relaxed by exploiting the enhancement of the electro-optic effect recently discovered by our group [M. Roussey, M.-P. Bernal, N. Courjal, D. Van Labeke, F.I. Baida, Electro-optic effect exaltation on lithium niobate photonic crystals due to slow photons. Appl. Phys. Lett. 89 (24) (2006) 241110], which we believe to be due to the presence of slow-light in the nanostructure. We present a methodology that readily identifies superprism design points showing both strong ultra-refraction as well as low group velocity. However, we find that this improved voltage efficiency comes at the cost of reduced operating bandwidth and increased insertion losses due to proximity to the band-edge.

Lumped‐constant‐type optical modulator in the microwave band for digital terrestrial TV broadcasting

AbstractBased on an optical modulator using the electrooptic effect of lithium niobate (LiNbO3) developed and productized in the UHF band (470 to 770 MHz), a lumped‐constant optical modulator with highly sensitive operation at microwave frequencies has been fabricated and tested and the possibility of realizability has been studied with a view to its application to digital terrestrial television broadcasting. The frequency ranges assigned for program transmission links for the digital terrestrial television broadcasting are 6 to 7 GHz and 10 GHz. Since a broad bandwidth (6 to 9 MHz) is available, various technological challenges must be overcome to assure a high C/N. Therefore, the system of the LN optical modulator and the modulation electrode structures have been fundamentally reconsidered, attaining a C/N of about 25 dB as the target at 6 GHz. When the C/N of the input signal is sufficiently high, the C/N of the present system is determined by the input signal voltage to the LN optical modulator, or the optical modulation index. In a real system, a head amplifier with a gain of 20 dB or greater is inserted. Hence, it is considered sufficiently possible to assure a C/N greater than 45 dB (target value) as a system. © 2007 Wiley Periodicals, Inc. Electron Comm Jpn Pt 2, 90(6): 1–9, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecjb.20341