Antenna-coupled silicon-organic hybrid integrated photonic crystal modulator for broadband electromagnetic wave detection

In this work, we design, fabricate and characterize a compact, broadband and highly sensitive integrated photonic electromagnetic field sensor based on a silicon-organic hybrid modulator driven by a bowtie antenna. The large electro-optic (EO) coefficient of organic polymer, the slow-light effects in the silicon slot photonic crystal waveguide (PCW), and the broadband field enhancement provided by the bowtie antenna, are all combined to enhance the interaction of microwaves and optical waves, enabling a high EO modulation efficiency and thus a high sensitivity. The modulator is experimentally demonstrated with a record-high effective in-device EO modulation efficiency of r33=1230pm/V. Modulation response up to 40GHz is measured, with a 3-dB bandwidth of 11GHz. The slot PCW has an interaction length of 300um, and the bowtie antenna has an area smaller than 1cm2. The bowtie antenna in the device is experimentally demonstrated to have a broadband characteristics with a central resonance frequency of 10GHz, as well as a large beam width which enables the detection of electromagnetic waves from a large range of incident angles. The sensor is experimentally demonstrated with a minimum detectable electromagnetic power density of 8.4mW/m2 at 8.4GHz, corresponding to a minimum detectable electric field of 2.5V/m and an ultra-high sensitivity of 0.000027V/m Hz^-1/2 ever demonstrated. To the best of our knowledge, this is the first silicon-organic hybrid device and also the first PCW device used for the photonic detection of electromagnetic waves. Finally, we propose some future work, including a Teraherz wave sensor based on antenna-coupled electro-optic polymer filled plasmonic slot waveguide, as well as a fully packaged and tailgated device.Comment: 20 pages, 16 figure

ELECTRO-OPTIC ANTENNA ELEMENTS FOR PASSIVE PHASED ARRAY RADAR

Passive phased antenna arrays are utilized in military and civilian radar systems to determine the received signal origination. Phased array placement for optimal reception is challenging due to the required supporting electronic hardware and the associated coaxial cabling that typically accompanies each antenna channel. Low noise amplifiers and frequency conversion hardware add size and complexity, limiting possible positions for phased array placement. Eliminating required phased array electronic subcomponents without sacrificing function would allow placement onto smaller agile platforms, such as unmanned systems and rapid deployment networks. Electro-optic (EO) antenna elements utilize an optical waveguide embedded between the antenna and ground plane that responds to the electric field received by the resonating antenna. Using EO antenna elements removes associated electronic hardware from antenna sites, thus simplifying advanced phased array technology. EO antenna elements modulate received signals directly into the optical domain where the low loss, electromagnetic immunity, low weight, and small size advantages of optical fiber can be utilized for antenna remoting. The combination of optical signals from EO antenna elements in Mach-Zehnder interferometers reduces the number of overall channels needed for a given radar system. The reduction of channels further serves to decrease the size, weight, cost, computation, and power requirements of the radar system. This thesis details the design, fabrication, and characterization of EO phased arrays and prototype EO antenna elements, both as individual antenna elements and in a phased array configuration. Waveguide loss, refractive index, and EO coefficient measurements are made for individual EO antenna elements. Radio Frequency (RF) phase modulation emulating a changing angle of arrival is applied by direct injection to a two-element phased array of EO antenna elements. The system’s optical output is correlated to the array factor for a two-element phased array showing proof-of-concept that EO antenna elements can be used in direction finding applications. The sensitivity of EO antenna elements is analyzed and a new design for EO antenna elements with improved sensitivity is presented. The electric field distribution of a rectangular patch antenna at resonance was found to be useful for driving a push-pull Mach-Zehnder modulator, doubling the EO antenna element sensitivity

LINEAR RING RESONATOR MODULATOR FOR MICROWAVE PHOTONIC LINKS

Modulators within Microwave photonic links (MPLs) encode Radio Frequency (RF) signal information to the optical domain for transmission in applications such as wireless access networks and antenna remoting exploiting advantages optical fiber offers over RF coaxial cables including bandwidth, loss, size, weight, and immunity to electromagnetic interference. A critical figure-of-merit in MPLs is spur-free-dynamic-range (SFDR) defining the range of RF signal power a MPL transmits without distortion. Current Mach-Zehnder Interference (MZI) modulators used in MPLs limit the SFDR because of the associated nonlinear sinusoidal transfer function. A rigorous theoretical method is developed followed by design, fabrication, and testing to investigate a linear ring resonator modulator (RRM) modulator for MPLs. The linear nature of the Lorentzian transfer function for the RRM is utilized over the sinusoidal transfer function within MZI modulators offering significant improvement in MPL SFDR. A novel bias voltage adjustment method is developed for practical implementations improving SFDR of 6 dB versus MZI at 500 MHz noise bandwidth. RRM is shown to be applicable for applications requiring high operational frequencies while in a limited operational bandwidth such as millimeter-wave wireless networks. To improve RRM SFDR in wide operational bandwidths a novel dual ring resonator modulator (DRRM) design is demonstrated. DRRM suppresses the third order intermodulation distortion in a frequency independent process removing SFDR limits of RRM

Plasmonic-Organic and Silicon-Organic Hybrid Modulators for High-Speed Signal Processing

High-speed electro-optic (EO) modulators are key devices for optical communications, microwave photonics, and for broadband signal processing. Among the different material platforms for high-density photonic integrated circuits (PIC), silicon photonics sticks out because of CMOS foundries specialized in PIC fabrication. However, the absence of the Pockels effect in silicon renders EO modulators with high-efficiency and large modulation bandwidth difficult. In this dissertation, plasmonic and photonic slot waveguide modulators are investigated. The devices are built on the silicon platform and are combined with highly-efficient organic EO materials. Using such a hybrid platform, we realize compact and fast plasmonic-organic hybrid (POH) and silicon-organic hybrid (SOH) modulators. As an application example, we demonstrate for the first time an advanced terahertz communication link by directly converting data on a 360 GHz carrier to a data stream on an optical carrier. For optical transmitter applications, we overcome the bandwidth limitation of conventional SOH modulators by introducing a high-k dielectric microwave slotline for guiding the modulating radio-frequency signal which is capacitively-coupled to the EO modulating region. We confirm the viability of such capacitively-coupled SOH modulators by generating four-state pulse amplitude modulated signals with data rates up to 200 Gbit/s

Silicon - polymer hybrid integrated microwave photonic devices for optical interconnects and electromagnetic wave detection

textThe accelerating increase in information traffic demands the expansion of optical access network systems that require high-performance optical and photonic components. In short-range communication links, optical interconnects have been widely accepted as a viable approach to solve the problems that copper based electrical interconnects have encountered in keeping up with the surge in the data rate demand over the last decades. Low cost, ease of fabrication, and integration capabilities of low optical-loss polymers make them attractive for integrated photonic applications to support futuristic data communication networks. In addition to passive wave-guiding components, electro-optic (EO) polymers consisting of a polymeric matrix doped with organic nonlinear chromophores have enabled wide-RF-bandwidth and low-power active photonic devices. Beside board level passive and active optical components, on-chip micro- or nano-photonic devices have been made possible by the hybrid integration of EO polymers onto the silicon platform. In recent years, silicon photonics have attracted a significant amount of attentions, because it offers compact device size and the potential of complementary metal–oxide–semiconductor (CMOS) compatible photonic integrated circuits. The combination of silicon photonics and EO polymers can enable miniaturized and high-performance hybrid integrated photonic devices, such as electro-optic modulators, optical interconnects, and microwave photonic sensors. Silicon photonic crystal waveguides (PCWs) exhibit slow-light effects which are beneficial for device miniaturization. Especially, EO polymer filled silicon slotted PCWs further reduce the device size and enhance the device performance by combining the best of these two systems. The potential applications of these silicon-polymer hybrid integrated devices include not only optical interconnects, but also optical sensing and microwave photonics. In this dissertation, the design, fabrication, and characterization of several types of silicon-polymer hybrid photonic devices will be presented, including EO polymer filled silicon PCW modulators for on-chip optical interconnects, antenna-coupled optical modulators for electromagnetic wave detections, and low-loss strip-to-slot PCW mode converters. In addition, some polymer-based devices and silicon-based photonic devices will also be presented, such as traveling wave electro-optic polymer modulators based on domain-inversion directional couplers, and silicon thermo-optic switches based on coupled photonic crystal microcavities. Furthermore, some microwave (or RF) components such as integrated broadband bowtie antennas for microwave photonic applications will be covered. Some on-going work or suggested future work will also be introduced, including in-device pyroelectric poling for EO polymer filled silicon slot PCWs, millimeter- or Terahertz-wave sensors based on EO polymer filled plasmonic slot waveguide, low-loss silicon-polymer hybrid slot photonic crystal waveguides fabricated by CMOS foundry, logic devices based on EO polymer microring resonators, and so on.Electrical and Computer Engineerin

A Single Laser System for Ground-State Cooling of 25-Mg+

We present a single solid-state laser system to cool, coherently manipulate and detect $^{25}$Mg$^+$ ions. Coherent manipulation is accomplished by coupling two hyperfine ground state levels using a pair of far-detuned Raman laser beams. Resonant light for Doppler cooling and detection is derived from the same laser source by means of an electro-optic modulator, generating a sideband which is resonant with the atomic transition. We demonstrate ground-state cooling of one of the vibrational modes of the ion in the trap using resolved-sideband cooling. The cooling performance is studied and discussed by observing the temporal evolution of Raman-stimulated sideband transitions. The setup is a major simplification over existing state-of-the-art systems, typically involving up to three separate laser sources

'ACOUSTO-OPTIC SENSING FOR SAFE MRI PROCEDURES'

In this work, a novel sensor platform is developed for safer and more effective magnetic resonance imaging (MRI). This is achieved by tracking interventional devices, such as guidewires and catheters during interventional MRI procedures, and by measuring the radio frequency (RF) field to assess RF safety of patients with implants, such as pacemakers, during diagnostic MRI. The sensor is based on an acousto-optic modulator coupled with a miniature antenna. This structure is realized on an optical fiber which is immune to the RF field and eliminates the need for conducting lines. The acousto-optic modulator consists of a piezo-electric transducer and a fiber Bragg grating (FBG). The piezoelectric transducer is electrically connected to the miniature antenna and mechanically coupled to the FBG. Local RF signal received by the miniature antenna is converted to acoustic waves by the piezoelectric transducer. Acoustic waves change the grating geometry on the FBG, thus the reflected light from the FBG is modulated. For diagnostic imaging, short dipole antennas are used for sensing the local electric field, which is the primary cause of RF induced heating. For tracking purposes, small loop antennas are used for capturing local MRI signal which contains the location information. In this thesis, a comprehensive model for the acousto-optic modulator is developed and validated through sensitivity and linearity tests. Prototype RF field sensors are built and characterized: sensitivity of 1.36mV/nT and 98 μV/V/m with minimum detectable field strength of 8.2pT/√Hz and 2.7V/m/√Hz and dynamic range of 117dB/√Hz at 23MHz are achieved with 4mm single loop and 8mm short dipole antennas, respectively. These figures are competitive with commercial sensors with much larger form factors. Catheter tracking capability of the sensor under MRI is demonstrated in-vivo in swine in a 0.55T scanner using an 8F catheter in addition to phantom studies under 0.55T and 1.5T clinical MRI systems.Ph.D

Bandwidth of linearized electrooptic modulators

Many schemes have been proposed to make high dynamic range analog radio frequency (RF) photonic links by linearizing the transfer function of the link's modulator. This paper studies the degrading effects of finite transit time and optical and electrical velocity dispersion on such linearization schemes. It further demonstrates that much of the lost dynamic range in some modulators may be regained by segmenting and rephasing the RF transmission line

Beyond 5G Fronthaul based on FSO Using Spread Spectrum Codes and Graphene Modulators.

High data rate coverage, security, and energy efficiency will play a key role in the continued performance scaling of next-generation mobile systems. Dense, small mobile cells based on a novel network architecture are part of the answer. Motivated by the recent mounting interest in free-space optical (FSO) technologies, this paper addresses a novel mobile fronthaul network architecture based on FSO, spread spectrum codes, and graphene modulators for the creation of dense small cells. The network uses an energy-efficient graphene modulator to send data bits to be coded with spread codes for achieving higher security before their transmission to remote units via high-speed FSO transmitters. Analytical results show the new fronthaul mobile network can accommodate up to 32 remote antennas under error-free transmissions with forward error correction. Furthermore, the modulator is optimized to provide maximum efficiency in terms of energy consumption per bit. The optimization procedure is carried out by optimizing both the amount of graphene used on the ring resonator and the modulator’s design. The optimized graphene modulator is used in the new fronthaul network and requires as low as 4.6 fJ/bit while enabling high-speed performance up to 42.6 GHz and remarkably using one-quarter of graphene only