INVESTIGATION OF THERMO-OPTIC EFFECTS IN SILICON MICRORING RESONATORS FOR SENSING AND INTERROGATION

Integrated photonics technology has great potential for enhancing the performance and reducing the volume and cost of optical sensing systems. Among many integrated photonic structures, silicon microring resonators have received much attention for both sensing and interrogation. Particularly, the high quality-factor of the microring resonators and the large thermo-optic coefficient and high thermal conductivity of silicon make them attractive for temperature sensing and thermally-tunable-filter-based interrogation. In this dissertation work, the thermo-optic effects in silicon microring resonators is studied and used in the silicon-ring-resonator-based temperature sensing and interrogation. The first objective of this dissertation work is to develop a highly sensitive photonic temperature sensor, which can be potentially used for achieving portable, compact temperature sensing systems employing a low-resolution on-chip spectrometer. However, the sensitivity of conventional silicon-ring-resonator-based temperature sensors is relatively low (less than ~80 pm/°C). These sensors often require the use of a bulky and expensive fine-resolution interrogator for high resolution temperature monitoring, since the sensor resolution is determined by the sensitivity. In this work, a novel photonic temperature sensor based on cascaded-ring-resonators with the Vernier effect is developed to simultaneously enhance the sensitivity and sensing range. With a proof-of-concept device, sensitivity enhancement of 6.3 times and sensing range enhancement of 5.3 times are demonstrated. On-chip optical interrogators employing a silicon-ring-resonator-based thermally tunable filter (SRRTF) offer a promising solution for realizing portable, compact optical sensing systems. However, the slow interrogation speed of conventional SRRTF-based interrogators (less than a few Hz) has hindered their application for dynamic sensing. The second objective of this dissertation work is to develop a high-speed SRRTF-based interrogator, which can be used to interrogate optical sensors monitoring dynamic parameters. In this work, an SRRTF-based system utilizing the nonlinear transient thermal response of the SRRTF is developed for the speed enhancement. High speed interrogation (100 kHz of interrogation speed) of a fiber Bragg grating (FBG) sensor is successfully demonstrated with this system. The third objective of the dissertation work is to further enhance the tuning speed and range of the previously developed SRRTF and to use it for simultaneous interrogation of multiplexed FBG sensors. Performance of SRRTF-based interrogators is primarily determined by thermal and optical characteristics of the SRRTF. However, conventional SRRTF structures with a metallic heater on the top oxide cladding have limitations on interrogation speed and range. In this dissertation work, a novel SRRTF employing an interior-ridge-ring resonator and thermal through-cladding-vias is developed, which can realize enhanced tuning speed and range. With this SRRTF, interrogation of multiplexed FBG sensors at 125 kHz speed is demonstrated

Investigation into Smart Multifunctional Optical System-On-A-Chip Sensor Platform and Its Applications in Optical Wireless Sensor Networks

Wireless sensor networks (WSNs) have been widely used in various applications to acquire distributed information through cooperative efforts of sensor nodes. Most of the sensor nodes used in WSNs are based on mechanical or electrical sensing mechanisms, which are susceptible to electromagnetic interference (EMI) and can hardly be used in harsh environments. Although these disadvantages of conventional sensor nodes can be overcome by employing optical sensing methods, traditional optical systems are usually bulky and expensive, which can hardly be implemented in WSNs. Recently, the emerging technologies of silicon photonics and photonic crystal promise a solution of integrating a complete optical system through a complementary metal-oxide-semiconductor (CMOS) process. However, such an integration still remains a challenge. The overall objective of this dissertation work is to develop a smart multifunctional optical system-on-a-chip (SOC) sensor platform capable of both phase modulation and wavelength tuningfor heterogeneous sensing, and implement this platform in a sensor node to achieve an optical WSN for various applications, including those in harsh environments. The contributions of this dissertation work are summarized as follows. i)A smart multifunctional optical SOC sensor platform for heterogeneous sensing has beendeveloped for the first time. This platform can be used to perform phase modulation and demodulation in a low coherence interferometric configuration or wavelength tuning in a spectrum sensing configuration.The multifunctional optical sensor platform is developed through hybrid integration of a light source, an optical modulator, and multiple photodetectors. As the key component of the SOC platform, two types of modulators, namely, the opto-mechanical and electro-optical modulators, are investigated. For the first time, interrogating different types of heterogeneous sensors, including various Fabry-Perot (FP) sensors and fiber Bragg grating (FBG) sensors, with a single SOC sensor platform, is demonstrated. ii)Enhanced understanding of the principles of the multifunctional optical platform withanopto-mechanical modulator has been achieved.As a representative of opto-mechanical modulators, a microelectromechanical systems (MEMS) based FP tunable filter is thoroughly investigated through mechanical and optical modeling. The FP tunable filter is studied for both phase modulation and wavelength tuning, and design guidelines are developed based on the modeling and parametric studies. It is found that the MEMS tunable filter can achieve a large modulation depth, but it suffers from a trade-off between modulation depth and speed. iii) A novel silicon electro-optical modulator based on microring structures for optical phase modulation and wavelength tuning has been designed. To overcome the limitations of the opto-mechanical modulators including low modulation speed and mechanical instability, a CMOS compatible high speed electro-optical silicon modulator is designed, which combines microring and photonic crystal structures for phase modulation in interferometric sensors and makes use of two cascaded microrings for wavelength tuning in sensors that require spectrum domain signal processing. iv)A novel optical SOC WSN node has been developed. The optical SOC sensor platform and the associated electric circuit are integrated with a conventional WSN module to achieve an optical WSN node, enabling optical WSNs for various applications. v) A novel cross-axial dual-cavity FP sensor has been developed for simultaneous pressure and temperature sensing.Across-axial sensor is useful in measuring static pressures without picking up dynamic pressures in the presence of surface flows. The dual-cavity sensing structure is used for both temperature and pressure measurements without the need for another temperature sensor for temperature drift compensation. This sensor can be used in moderate to high temperature environments, which demonstrates the potential of using the optical WSN sensor node in a harsh environment

Silicon photonic polarimeters and spectropolarimeters

Puisqu’ils offrent la possibilité d’intégrer monolithiquement un grand nombre de composants à un faible coût, les circuits intégrés photoniques (CIPs) sont devenus une plateforme de choix pour la réalisation de capteurs optiques sur puce. Cette thèse propose, puis démontre l’utilisation de CIPs sur silicium pour la réalisation de polarimètres et de spectro-polarimètres sur puce. Dans le premier chapitre, nous présentons un séparateur de polarisation utilisant un réseau de nano-antennes en forme d’arêtes de poisson sur silicium. Nous montrons également qu’une structure de la sorte est en mesure de séparer deux états de polarisation arbitraires qui sontorthogonaux entre-eux. De plus, nous avons amélioré le précédent modèle théorique existant pour y inclure ce phénomène. Dans le second chapitre, nous présentons et démontrons de façon expérimentale un polarimètre intégré sur silicium qui requiert 6 photodétecteurs (6-PDs). Ici, la structure optimale veut dire que, pour un niveau de bruit donné, cette structure permet d’obtenir l’état de polarisation avec la précision la plus élevée. Nous démontrons également de façon théorique que cette configuration proposée peut maintenir un état optimal sur une plage de longueur d’onde de100 nm. Dans le troisième chapitre, nous proposons une jonction en « Y » paramétrisée dont le ratio de séparation de puissance peut être choisi avant la fabrication, lors de la conception. Sur une plage de longueur d’onde de 100 nm, les pertes de puissance de la jonction sont inférieuresà 0.36 dB, et ce, pour tout ratio arbitraire de séparation de puissance. De plus, sa taille de1.4 µm × 2.3 µm le rend très compact.Au chapitre 4, nous proposons un polarimètre optimal composé de quatre photodétecteurs(4-PDs) possédant ces propriétés à partir de la jonction en « Y » proposée au chapitre 3. Un polarimètre non-optimal est fabriqué de manière à montrer la différence entre celui-ci et le cas optimal. Les résultats expérimentaux montrent que l’erreur de reconstruction du composant optimal est inférieure de 44 % à celle du composant non-optimal.Dans le cinquième chapitre, nous proposons et faisons la démonstration d’un spectro- polarimètre réalisé intégralement sur puce. Afin de permettre une analyse spectro-polarimétrique iiicomplete, quatre micro-résonateurs à effet Vernier compacts sont intégrés monolithiquement avec un polarimètre large-bande. Le composant optique proposé offre une solution de spectropolarimétrie sur semi-conducteur tout en gardant une taille très compacte de 1 × 0.6 mm2et une faible consommation de puissance de 360 mW. La détection spectrale pour tous les composants de Stokes est démontrée sur une large plage de longueur d’onde de 50 nm, et ce avec une résolution de 1 nm par la caractérisation d’un matériau possédant une chiralité structurelle.The ability to monolithically integrate numerous components in low-cost, photonic integratedcircuits (PICs) has become a hot topic in the research for realizing on-chip optical measurement. In this thesis, we propose and demonstrate two on-chip polarimeters and an on-chipspectropolarimeter using silicon PICs.In the first chapter, we investigate the optical properties of the silicon fishbone nanoantennaarray. We found that this type of structure can be used to identify any two arbitrary orthogonalpolarization states. The previous theoretical model was also improved upon in order to explainthis phenomenon.In the second chapter, we propose and experimentally demonstrate a silicon polarimeter whichrequires six photodetectors. We also theoretically demonstrate that the proposed configurationcan maintain an optimal state over a wavelength range of 100 nm. Here, the optimal structuremeans that for a given noise, the structure would allow for the highest and polarizationindependent accuracy of the polarization state measurement to be obtained.In the third chapter, we propose a parameterized Y-junction whose arbitrary power splittingratio can be selected in layout design. For an arbitrary power splitting ratio, its excess losscan keep below 0.36 dB over a wavelength range of 100 nm. Moreover, this device has anultra-compact footprint of 1.4 µm × 2.3 µm.Based on the Y-junction proposed in chapter 3, the fourth chapter proposes an optimal siliconphotonic polarimeter that only requires four photodetectors and its configuration is optimal.A non-optimal device is fabricated to show the difference between optimal and non-optimaldevices. The experimental results indicate that the reconstructed error of the optimal deviceis 44% lower than that of the nonoptimal device.In the fifth chapter, a completely chip-level spectropolarimeter is proposed. Four compactVernier microresonator spectrometers are monolithically integrated with a broadband polarimeter to achieve full-Stokes spectropolarimetric analysis. The proposed device offers asolid-state spectropolarimetry solution with a small footprint of 1 × 0.6 mm2 and low powerconsumption of 360 mW. Full-Stokes spectral detection across a broad spectral range of 50 nmwith a resolution of 1 nm is demonstrated in characterizing a material that possesses structuralvchirality

Semiconductor Laser Dynamics

This is a collection of 18 papers, two of which are reviews and seven are invited feature papers, that together form the Photonics Special Issue “Semiconductor Laser Dynamics: Fundamentals and Applications”, published in 2020. This collection is edited by Daan Lenstra, an internationally recognized specialist in the field for 40 years

Silicon Photonic Devices and Their Applications

Silicon photonics is the study and application of photonic systems, which use silicon as an optical medium. Data is transferred in the systems by optical rays. This technology is seen as the substitutions of electric computer chips in the future and the means to keep tack on the Moore’s law. Cavity optomechanics is a rising field of silicon photonics. It focuses on the interaction between light and mechanical objects. Although it is currently at its early stage of growth, this field has attracted rising attention. Here, we present highly sensitive optical detection of acceleration using an optomechanical accelerometer. The core part of this accelerometer is a slot-type photonic crystal cavity with strong optomechanical interactions. We first discuss theoretically the optomechanical coupling in the air-slot mode-gap photonic crystal cavity. The dispersive coupling gom is numerically calculated. Dynamical parametric oscillations for both cooling and amplification, in the resolved and unresolved sideband limit, are examined numerically, along with the displacement spectral density and cooling rates for the various operating parameters. Experimental results also demonstrated that the cavity has a large optomechanical coupling rate. The optically induced spring effect, damping and amplification of the mechanical modes are observed with measurements both in air and in vacuum. Then, we propose and demonstrate our optomechanical accelerometer. It can operate with a resolution of 730 ng/Hz¹/² (or equivalently 40.1 aN/Hz¹/²) and with a transduction bandwidth of ≈ 85 kHz. We also demonstrate an integrated photonics device, an on-chip spectroscopy, in the last part of this thesis. This new type of on-chip microspectrometer is based on the Vernier effect of two cascaded micro-ring cavities. It can measure optical spectrum with a bandwidth of 74nm and a resolution of 0.22 nm in a small footprint of 1.5 mm²