Radio-frequency (RF) signal processing is largely based on various components built on single crystal materials generally patterned and structured using planar technologies on wafers for the manufacturing of acousto-electrical devices (surface or bulk acoustic wave devices), optical wave-guides or electro-optical components (modulators, interferometers). One can therefore achieve a large number of functions but some of the corresponding devices are submitted to functionnal flaws independant of the material properties and characteristics (these materials - quartz, lithium niobate or tantalate - exhibit a high level of maturity from an industrial point of view) but related to the usual machining or patterning limits for manufacturing guiding or excitation/detection structures, which prevents to overcome the corresponding functionnal limitations. The CHARADES project then is devoted to the development of technologies capable to upset the corresponding scientific domains and to allow for major evolutions of the manufacturing of new components exploiting the most advantages of single crystal materials required for achieving the targetted functions. Particularly, a new method based on simultaneous sawing/polishing techniques is implemented for the fabrication of high aspect ratio structures (ridges, aspect ratio in excess of 100) providing devices exhibiting unique guiding and trapping capabilites. New functionnalities hence are accessible and the demonstration of the corresponding innovative potential is achieved for acousto-electrical resonators used as sources, filters and sensors and in optics for waveguides, sensors and electro-optical modulators for telecommunication purposes. In parallel, technologies based on deep reactive ion etching are implemented to allow first for batch fabrication of devices on large diameter wafers and second to push ahead the operation limits of the considered devices (frequencies, compactness). Finally, a significant part of the project is dedicated to the theoretical analysis and the experimental investigation of cross-coupled physical phenomena, favored by the ultimate machining capabilities and the specific configuration of the structures developped in the CHARADES project.

The project goal is to develop extremely sensitive electric field (E-field) sensor with flat response in a very large frequency range based on electro-optic photonic crystal devices fabricated on suspended micrometric size membranes of lithium niobate. We aim at nanooptical electric field sensors that will have for 10 dB total optical losses, microV/m sensitivity, ~ 10x10microns2 active area, and large frequency bandwidth [DC, GHz]. The detection will be purely optical which implies the following advantages: • The sensor provides improved measurement accuracy by reducing susceptibility to electrical noise because the sensor is made of dielectric material. • The sensor provides a non-perturbative measurement of electric field in comparison to antennas. • The sensor may be placed in hostile or remote areas because optical fibers are capable of transmitting signals with high fidelity in noisy environments and over long distances. • The sensor is electrically isolated, thus providing operator instrument safety. • The sensor is small enough to be used where space is a constraint. Because the electric field sensor is an all-optical and an all-dielectric device, it offers minimal disturbance to the electric field to be measured and opens the way to near field measurements. It also operates without a battery, so measurements can be conducted over a long period. Its sensing part does not contain any electronic devices or circuits, so it can easily be miniaturized. The optical device will be a photonic crystal that brings the following advantages with respect to classical electro-optical devices already reported in literature: - Small size, this is very useful for applications like in f-MRI, EEG or ECG because one can envision hundreds of electrodes (for exemple integrated in a cap for EEG). - In lithium niobate photonic crystals, electro-optic effect can be enhanced enormously thanks to slow light configurations; Sensitivities of microV/M can be expected which is 1000 times higher than in state of the art electro-optic sensors based in Mach-Zehnder configurations. The key feature on reaching unprecedented performances on electric field sensitivities never obtained before come from the fact that the optical detector is an active photonic crystal in which light-matter interaction can be enormously enhanced if a suitable dielectric material is chosen. In ESENCYAL, the detector is going to be a photonic crystal fabricated in lithium niobate. This nano-device in lithium niobate will have the unique property of being able to exacerbate the electro-optic effect with respect to bulk devices. Indeed, Photonic crystals (PhCs) are periodic arrangements of dielectric media that exhibit a photonic band structure that is analogous to the electronic band structure in crystalline solids [JJ08]. Because of their potential to offer unprecedented control over the flow of light in extremely small structures, PhCs have been viewed as having some revolutionary impact on photonics as the planar transistor did in electronics. In particular, the possible existence of a photonic band gap -a range of optical wavelengths that cannot propagate through the structure unless line or point defects are incorporated– provides opportunities for device engineering analogous to semiconductors junctions or heterostructures. The present project falls entirely within the scientific guidelines of the DGA for 2013 and beyond. It fits completely the Nanotechnology axe in applications such as threaten detection, and miniaturized devices to be used in hazardous environments. In addition, our proposal can be used also in applications that are directly related with the axes Waves and Photonics since it could be used in the following cases: Electronic war and electromagnetic aggressions, electromagnetic compatibility and biosignal sensing.

Most of optical transmission systems now deployed use 10Gb/s signals associated with wavelength division multiplexing (WDM) technology. In 2005, Infinera introduced photonic integrated circuits (PIC) on InP and designed a device with 10 wavelengths at 10Gb/s on a single chip. A promising alternative to push integration of photonic circuits even further is to rely on silicon photonics. Silicon photonics will later allow the joint integration of high speed electronics with photonics on the same chip. ULTIMATE proposes to demonstrate a 4x100Gb/s PIC transmitter based on this technology, integrating 4 transmitters at 100Gb/s, namely 4 tunable lasers, 8 QPSK modulators and semiconductor optical amplifiers (SOA). This PIC will leverage the lessons learned from Alcatel-Lucent’s coherent solution at 100Gb/s using PDM QPSK modulation format and coherent detection, the first of its kind on the market since mid 2010, and from pioneer work on Silicon Photonics achieved by the consortium. A first technical challenge concerns the optical laser sources. Compared to first demonstration done by III-Vlab and CEA within HELIOS FP7 project, the objectives are to increase output power and to demonstrate tunability over 30nm while achieving narrow linewidth for compatibility with coherent detection. A second challenge deals with high speed optical modulator. Modulator bandwidth should be increased compared to first demonstration done by IEF within HELIOS FP7 project, structure should be more complex (QPSK modulator) and modulator should be compatible with low output voltage coming from CMOS chip. Several iterations will be required to fully achieve these ambitious objectives. The project will be split in three phases. Phase one will demonstrate tunable laser on one hand and high bandwidth BPSK modulator as well as QPSK modulator on the other one. Phase two will demonstrate the integration of one tunable laser with two QPSK modulators and SOAs to demonstrate a first 100Gb/s transmitter. Optimized packaging will be realized as well as system validation in a WDM test bed. Phase three will integrate four transmitters (but only one transmitter packaged with RF lines) and will benefit from lessons learned in phase 1 and 2. Transmitter and high speed CMOS FPGA will be soldered on a printed circuit board for system tests. Indeed, a longer term challenge, not within the frame of this project, will be to integrate on a single chip a high speed CMOS circuit generating several 25Gb/s streams and the photonic part including laser, modulator and SOA. An optimized packaging is also required to fully exploit silicon photonic chip performance in a system test bed. The objective here is to demonstrate optical transmission over distances larger than 1000 km in wavelength division multiplexing (WDM) context. Photonic integration is a key method to reduce cost, footprint and power consumption of optical transmission systems. It will bring an extremely valuable differentiator to WDM system vendors having access to such technologies. Integration of several 100Gb/s wavelengths on a single chip appears today’s as one of the most promising direction to answer future market requirements for 400Gb/s or 1Tb/s. While MICROS project (ANR 2009) intends to realize the coherent receiver part on silicon photonic, ULTIMATE focus on the transmitter side. ULTIMATE project will bring a competitive advantage to the partners of this project and especially Alcatel-Lucent in a highly competitive market where technological differentiators are required.