A. James Clark School of Engineering
Permanent URI for this communityhttp://hdl.handle.net/1903/1654
The collections in this community comprise faculty research works, as well as graduate theses and dissertations.
Browse
3 results
Search Results
Item HIGH THROUGHPUT STIMULATED BRILLOUIN SCATTERING SPECTROSCOPY(2024) Rosvold, Jake Robert; Scarcelli, Giuliano; Bioengineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Brillouin light scattering arises from the coupled interaction between light and material acoustic phonons. The measurand of Brillouin scattering is the characteristic frequency difference between incident and scattered light which depends on the local longitudinal modulus of the material. Spontaneous Brillouin scattering has been used in combination with confocal microscopy to provide non-contact, label-free mapping at micron-scale resolution in biological media. To date, spontaneous Brillouin microscopy has reached the speed limit (~20-50ms per spectrum) as determined by the theoretical scattering efficiency. While a great deal of research has been directed to speeding up Brillouin microscopy acquisition times, spontaneous Brillouin scattering is fundamentally an inefficient process thus limiting the ability to study faster biological phenomena and rapid processes. To combat this limitation, its nonlinear counterpart, stimulated Brillouin scattering (SBS) has been proposed for microscopy applications. For decades, stimulated Brillouin scattering has been used in fiber sensing and all-optical pulse control and leverages a nonlinear interaction where two counterpropagating light beams stimulate a more efficient scattering relationship. However, the small interaction volumes and photodamage constraints presented in microscopy have hindered the translation of stimulated Brillouin scattering into the biological realm. Recently, continuous wave stimulated Brillouin microscopy has led to competitive acquisition times (~5ms per spectrum) when compared to the spontaneous alternative but has yet to be widely adopted. Due to a plethora of factors, such as an inefficient power balance between pump and probe beams, lack of proper commercial laser sources, and nonoptimal detection schemes, the complete picture of what SBS spectroscopy has to offer has yet to be revealed. As such, there is a need to customize light sources and detection schemes in order to fully take advantage of the enhanced Brillouin efficiency possible in SBS. Herein we introduce novel methodology to improve the acquisition speed of Brillouin microscopy by designing and developing proper laser sources and detection schemes for efficient SBS spectroscopy. First, we showcase the potential utility of our state-of-the-art continuous wave SBS technology in a flow cytometry application, highly suitable for the counterpropagating geometry of SBS where the laser position is fixed while the sample is being moved at high speeds. Additionally, we will present an optimized receiver design based on polarization detection which enables 100x faster spectral measurements in the low-gain regime relevant to biological materials. Finally, we demonstrate an optimal pulsed laser source specifically designed for SBS Brillouin microscopy.Item QUANTUM MODEM AND ROUTER FOR THE QUANTUM INTERNET(2022) Saha, Uday; Waks, Edo; Electrical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Like the internet, the quantum internet can change the world by connecting quantum computers over long distances. This connectivity can revolutionize different industries like banking, healthcare, and data analytics that utilize quantum computing and simulations. Additionally, it would enable us to connect multiple small quantum computers into powerful distributed quantum computers that can solve problems of significant societal impact. Despite the rise of excellent quantum computers, we don't yet have the core technologies to connect them. This is because modems and routers we use to connect classical computers don't work for quantum information. They destroy the coherence and entanglement of quantum information, which is vital for connecting quantum computers. In my thesis, I developed a quantum modem and router that can connect quantum computers and create a scalable quantum network. I have conceived the modem and router for the trapped ion quantum computers, the most promising quantum computing platform. However, we can easily use my developed concepts to connect different quantum computing platforms. I accomplished a quantum modem that provides an interface between a quantum computer and a fiber-optic network by generating telecommunication photons from the computer. I used a two-stage quantum frequency conversion scheme to realize the quantum modem. By calculating the second-order correlation function, I experimentally verified single-photon characteristics retained after the frequency conversion process. Telecommunication photons generated by the quantum modem can carry quantum information from ions over long distances. This will allow a long-distance quantum network to realize the quantum internet. On the other hand, I implemented a quantum router with photonic integrated circuits. Utilizing the thermo-optic property, I route photons from a trapped barium ion into different output ports of the quantum router in a programmable manner. This router can connect multiple quantum computers on-demand and in a scalable way. We are the first group to demonstrate a quantum modem and router working together with a quantum computer. This demonstration could lead to a scalable quantum network where photons from different quantum computers can be interfered with a programmable photonic chip to herald entanglement. Additionally, I developed visible photonic circuits for quantum data centers. In a quantum data center, there can be multiple trapped ion quantum computers that need to be connected. For this purpose, I designed a photonic circuit on a thin-film lithium niobate platform that can entangle two trapped ion quantum computers with >99% fidelity. Apart from achieving high fidelity entanglement, the circuit can achieve any polarization-independent power splitting ratio, which can have extensive use in integrated photonic technology. Finally, I invented a multiplexing scheme by which we can send quantum information from multiple quantum computers using a single fiber-optic cable. That will increase the channel capacity, where multiple quantum computers can communicate through the same channel. By encoding quantum information into the different wavelengths of photons, I devised my idea of multiplexing quantum information. These results will enable us to achieve a programmable and scalable network of quantum computers to increase the capability of quantum computing and quantum simulations and lead us to the future quantum internet.Item Nonlinear Optics and Carrier Dynamics in Nanostructured and Two-Dimensional Materials(2016) Suess, Ryan; Murphy, Thomas E; Electrical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Understanding and measuring the interaction of light with sub-wavelength structures and atomically thin materials is of critical importance for the development of next generation photonic devices. One approach to achieve the desired optical properties in a material is to manipulate its mesoscopic structure or its composition in order to affect the properties of the light-matter interaction. There has been tremendous recent interest in so called two-dimensional materials, consisting of only a single to a few layers of atoms arranged in a planar sheet. These materials have demonstrated great promise as a platform for studying unique phenomena arising from the low-dimensionality of the material and for developing new types of devices based on these effects. A thorough investigation of the optical and electronic properties of these new materials is essential to realizing their potential. In this work we present studies that explore the nonlinear optical properties and carrier dynamics in nanoporous silicon waveguides, two-dimensional graphite (graphene), and atomically thin black phosphorus. We first present an investigation of the nonlinear response of nanoporous silicon optical waveguides using a novel pump-probe method. A two-frequency heterodyne technique is developed in order to measure the pump-induced transient change in phase and intensity in a single measurement. The experimental data reveal a characteristic material response time and temporally resolved intensity and phase behavior matching a physical model dominated by free-carrier effects that are significantly stronger and faster than those observed in traditional silicon-based waveguides. These results shed light on the large optical nonlinearity observed in nanoporous silicon and demonstrate a new measurement technique for heterodyne pump-probe spectroscopy. Next we explore the optical properties of low-doped graphene in the terahertz spectral regime, where both intraband and interband effects play a significant role. Probing the graphene at intermediate photon energies enables the investigation of the nonlinear optical properties in the graphene as its electron system is heated by the intense pump pulse. By simultaneously measuring the reflected and transmitted terahertz light, a precise determination of the pump-induced change in absorption can be made. We observe that as the intensity of the terahertz radiation is increased, the optical properties of the graphene change from interband, semiconductor-like absorption, to a more metallic behavior with increased intraband processes. This transition reveals itself in our measurements as an increase in the terahertz transmission through the graphene at low fluence, followed by a decrease in transmission and the onset of a large, photo-induced reflection as fluence is increased. A hybrid optical-thermodynamic model successfully describes our observations and predicts this transition will persist across mid- and far-infrared frequencies. This study further demonstrates the important role that reflection plays since the absorption saturation intensity (an important figure of merit for graphene-based saturable absorbers) can be underestimated if only the transmitted light is considered. These findings are expected to contribute to the development of new optoelectronic devices designed to operate in the mid- and far-infrared frequency range. Lastly we discuss recent work with black phosphorus, a two-dimensional material that has recently attracted interest due to its high mobility and direct, configurable band gap (300 meV to 2eV), depending on the number of atomic layers comprising the sample. In this work we examine the pump-induced change in optical transmission of mechanically exfoliated black phosphorus flakes using a two-color optical pump-probe measurement. The time-resolved data reveal a fast pump-induced transparency accompanied by a slower absorption that we attribute to Pauli blocking and free-carrier absorption, respectively. Polarization studies show that these effects are also highly anisotropic - underscoring the importance of crystal orientation in the design of optical devices based on this material. We conclude our discussion of black phosphorus with a study that employs this material as the active element in a photoconductive detector capable of gigahertz class detection at room temperature for mid-infrared frequencies.