[HDR] Collective matter excitations at THz frequencies and their applications for innovative THz photonic devices
Collective matter excitations at THz frequencies and their applications for innovative THz photonic devices
Résumé
This Habilitation memoir gives a complete overview of my research activities since my PhD diploma in May 2005. During these 18 years of research (of which 16 as tenured CNRS researcher), I have been conducting my research in two different research laboratories: from 2005 until 2012 in the IEF laboratory at the Universite Paris-Sud (now C2N Paris-Saclay) and since October 2012 in the IEMN laboratory at Université de Lille. Even though this geographic mobility was accompanied by an important thematic reorientation, I have managed to maintain and even to enrich and strengthen a consistent research strategy. The thematic mobility from near-infrared (integrated telecom) optics (with a focus on magnetooptics and -plasmonics) towards the THz field, has resulted not only in deepening my expertise in electromagnetic nonreciprocity by extending it also to these longer wavelengths, but has also added two very active research lines to my scientific activities: integrated THz photonics and novel solid-state THz sources. By now, I have therefore established three fully developed research axes, for which I have proven to lead them in an independent way. I have developed a strong national and international collaborative network that has allowed me to secure funding and attract (post-)doctoral researchers on a regular basis for all three research axes. This memoir is organised thematically in three chapters in line with these axes. In each of them I highlight the key scientific achievements, placing them in the context of the challenges the domain was/is facing, explaining the developed strategy, underlining the contribution of the students and collaborators involved and indicating the project funding that supported the activities. The first (and biggest) chapter focusses on my research in the field of electromagnetic nonreciprocity. As this is also the research specialty on which I conducted my doctoral research, it has logically occupied a central place in my research preferences. It constitutes the lion's share of my research output, of my contractual activities, and of the number of PhD students. In this domain I have demonstrated both numerically and experimentally entirely novel concepts to achieve efficient isolation from the near-infrared down to THz frequencies both in guided and free-space configurations. I consider the work on magnetoplasmonic enhancement of MO effects (both at IR and THz fequencies) and in particular the demonstration of one-way mirroring to be one of my major research achievements. The theoretical insights gathered on the use of magnetic symmetry groups to design novel nonreciprocal structures has also been an intellectually satisfying exercise. All of these research activities have been supported by the development of a fully anisotropic and gyrotropic, full 3D modeling framework. The second research axis on integrated photonics for THz sensing (and potentially signal processing) has initially been developed along the research goals defined in the TERAFOOD EU research project that I have coordinated. The demonstrated integrated platform based on ultralow loss suspended HR-Si waveguides has achieved record performances both for compact low loss guiding and ultra high-Q resonant confinement at sub-mm wave frequencies. While the TERAFOOD project has used this platform to demonstrate a novel concept for integrated THz trace gas sensing, the availability of a low-cost integrated low-loss building block for mm- and submm-waves is an sich a very important realization. It opens the way towards a general-purpose (hybrid) integration platform that includes all active and passive functionalities for signal processing of high-volume short-range wireless links besides on-chip sensing and spectroscopy applications. The specific demonstration within TERAFOOD of integrated photoacoustic trace gas sensing is just a first example. Despite several setbacks, very promising first results on H$_2$S sensing have been achieved. For a first generation device, the measured and projected future performance already places this new research axis in the lab among the best photoacoustic sensing devices that have been reported. My final research axis focuses on the investigation of disruptive novel approaches for THz generation in solid-state media. With this activity, I specifically seek to place myself on a complementary and more blue-sky path compared to the research on THz generation that is already extensively covered by my group colleagues. This thematic has evolved in less than 4 years to become presently the center of my research funding activity. By luck and serendipity, I have become heavily involved in the very trending topic of ultrafast sub-ps spin dynamics in magnetic nanostructures. Supported by FET funding, I have managed to establish within the group a solid expertise on spintronic based THz sources. Together with IEMN colleagues, we have demonstrated original results on engineered magnetically anisotropic inverse spin Hall THz emitters (for scalar field controlled ultrafast dynamic polarization rotation) and spintronic photomixing. On these two research axes within the THz spintronic community, we can claim to occupy a leading and original position. The expertise I have developed is underlined by the increasing contractual activity I have recently obtained in this field. In a final chapter, I have sketched how I see my research activity developing in the coming years. These future activities are both developed on a short term timeframe in line with my ongoing research contracts (or solving some of the unfinished businesses on the finished ones), and on a longer more prospective timescale. While this is principally presented per each of the three well established research axes, I have tried to underline where possible how these activities can overlap and be seen in a larger framework. Though maybe a bit far fetched, I believe that the overarching strategy in my research is to exploit collective matter excitations that present a peculiar resonant or enhanced behaviour at picosecond timescales. Even though at first sight very diverse (collective spin excitations, carrier cyclotron resonances, molecular rotovibrational crystal oscillations, ...) these excitations all share the same property of enabling either a radically improved THz functionality (e.g. sensing, isolation, \ldots) or enable an entirely innovative approach for THz sources. Two appendices are included, listing all supervised students (with a short description of their activity) and all obtained research projects (with a brief description of their goals)
This Habilitation memoir gives a complete overview of my research activities since my PhD diploma in May 2005. During these 18 years of research (of which 16 as tenured CNRS researcher), I have been conducting my research in two different research laboratories: from 2005 until 2012 in the IEF laboratory at the Universite Paris-Sud (now C2N Paris-Saclay) and since October 2012 in the IEMN laboratory at Université de Lille. Even though this geographic mobility was accompanied by an important thematic reorientation, I have managed to maintain and even to enrich and strengthen a consistent research strategy. The thematic mobility from near-infrared (integrated telecom) optics (with a focus on magnetooptics and -plasmonics) towards the THz field, has resulted not only in deepening my expertise in electromagnetic nonreciprocity by extending it also to these longer wavelengths, but has also added two very active research lines to my scientific activities: integrated THz photonics and novel solid-state THz sources. By now, I have therefore established three fully developed research axes, for which I have proven to lead them in an independent way. I have developed a strong national and international collaborative network that has allowed me to secure funding and attract (post-)doctoral researchers on a regular basis for all three research axes. This memoir is organised thematically in three chapters in line with these axes. In each of them I highlight the key scientific achievements, placing them in the context of the challenges the domain was/is facing, explaining the developed strategy, underlining the contribution of the students and collaborators involved and indicating the project funding that supported the activities. The first (and biggest) chapter focusses on my research in the field of electromagnetic nonreciprocity. As this is also the research specialty on which I conducted my doctoral research, it has logically occupied a central place in my research preferences. It constitutes the lion's share of my research output, of my contractual activities, and of the number of PhD students. In this domain I have demonstrated both numerically and experimentally entirely novel concepts to achieve efficient isolation from the near-infrared down to THz frequencies both in guided and free-space configurations. I consider the work on magnetoplasmonic enhancement of MO effects (both at IR and THz fequencies) and in particular the demonstration of one-way mirroring to be one of my major research achievements. The theoretical insights gathered on the use of magnetic symmetry groups to design novel nonreciprocal structures has also been an intellectually satisfying exercise. All of these research activities have been supported by the development of a fully anisotropic and gyrotropic, full 3D modeling framework. The second research axis on integrated photonics for THz sensing (and potentially signal processing) has initially been developed along the research goals defined in the TERAFOOD EU research project that I have coordinated. The demonstrated integrated platform based on ultralow loss suspended HR-Si waveguides has achieved record performances both for compact low loss guiding and ultra high-Q resonant confinement at sub-mm wave frequencies. While the TERAFOOD project has used this platform to demonstrate a novel concept for integrated THz trace gas sensing, the availability of a low-cost integrated low-loss building block for mm- and submm-waves is an sich a very important realization. It opens the way towards a general-purpose (hybrid) integration platform that includes all active and passive functionalities for signal processing of high-volume short-range wireless links besides on-chip sensing and spectroscopy applications. The specific demonstration within TERAFOOD of integrated photoacoustic trace gas sensing is just a first example. Despite several setbacks, very promising first results on H$_2$S sensing have been achieved. For a first generation device, the measured and projected future performance already places this new research axis in the lab among the best photoacoustic sensing devices that have been reported. My final research axis focuses on the investigation of disruptive novel approaches for THz generation in solid-state media. With this activity, I specifically seek to place myself on a complementary and more blue-sky path compared to the research on THz generation that is already extensively covered by my group colleagues. This thematic has evolved in less than 4 years to become presently the center of my research funding activity. By luck and serendipity, I have become heavily involved in the very trending topic of ultrafast sub-ps spin dynamics in magnetic nanostructures. Supported by FET funding, I have managed to establish within the group a solid expertise on spintronic based THz sources. Together with IEMN colleagues, we have demonstrated original results on engineered magnetically anisotropic inverse spin Hall THz emitters (for scalar field controlled ultrafast dynamic polarization rotation) and spintronic photomixing. On these two research axes within the THz spintronic community, we can claim to occupy a leading and original position. The expertise I have developed is underlined by the increasing contractual activity I have recently obtained in this field. In a final chapter, I have sketched how I see my research activity developing in the coming years. These future activities are both developed on a short term timeframe in line with my ongoing research contracts (or solving some of the unfinished businesses on the finished ones), and on a longer more prospective timescale. While this is principally presented per each of the three well established research axes, I have tried to underline where possible how these activities can overlap and be seen in a larger framework. Though maybe a bit far fetched, I believe that the overarching strategy in my research is to exploit collective matter excitations that present a peculiar resonant or enhanced behaviour at picosecond timescales. Even though at first sight very diverse (collective spin excitations, carrier cyclotron resonances, molecular rotovibrational crystal oscillations, ...) these excitations all share the same property of enabling either a radically improved THz functionality (e.g. sensing, isolation, \ldots) or enable an entirely innovative approach for THz sources. Two appendices are included, listing all supervised students (with a short description of their activity) and all obtained research projects (with a brief description of their goals)