Design, Analysis and Fabrication of Silicon-Based Optical Materials and Photonic Crystal Devices

As the integration of electronic components grow so does the need for low power, low cost, and high-speed devices. These have resulted in an increased need for complementary metal-oxide semiconductor (CMOS) compatible materials and fabrication technique for novel structures as well as accurate models of the electromagnetic eld behavior in them. Recent advances in materials technology and fabrication techniques have made it feasible to consider silicon (Si)-based optical materials and photonic crystal (PhC) de- vices having physical dimensions of the order of the optical wavelength as the possible means to achieve these needs. Research has shown that light emission from Si is possible in low-dimensional state, i.e., Si-nanocrystals (Si-ncs). Furthermore, three-dimensional (3-D) control of light compatible with CMOS fabrication technology is required in order to fully integrate optical functionalities into the existing Si-technology. However, the di - culties in the fabrication of 3-D PhC waveguides have resulted in using two-dimensional (2-D) PhC structures. Finally, numerical simulations pro- vide a framework for quick low-cost feasibility studies and allow for design optimization before devices are fabricated. In this dissertation, we present our e orts along these directions. This dissertation addressed the method of obtaining high quantum e ciency from Si-ncs compatible with CMOS processing. Si ions were implanted into a fused-silica substrate (10 mm 10 mm 1 mmt) at room temperature in the Takasaki ion accelerators for advanced radiation application (TIARA) of the Japan Atomic Energy Agency. The implantation energy was 80 keV, and the implantation amount was 2 1017 ions/cm2. The Si-implanted sub- strate was cut into four pieces (5 mm 5 mm 1 mmt) using a diamond-wire saw, and the four pieces were annealed in ambient air at 1100, 1150, 1200, and 1250 oC for 25 min in a siliconit furnace. PL spectra were measured at room temperature with excitation using a He-Cd laser ( =325 nm). Ultra- violet (UV)-PL spectra having peaks around a wavelength of 370 nm were observed from all the samples. In our experiments, the UV-PL peak had a maximum intensity after annealing at 1250 oC, and the longer wavelength PL peak around 800 nm observed from the samples annealed at 1100 and 1150 oC disappeared by annealing above 1200 oC. The two PL peaks of the Si-ion-implanted samples may have originated from interface layers be- tween Si-ncs and SiO2 media. However, we successfully obtained only the UV-light emission peaks by selecting the proper annealing temperatures. UV-light-emitting materials are expected to be useful as light sources for next-generation optical-disk systems whose data densities are higher than Blu-ray Disk systems. Additionally, this dissertation addressed the numerical modeling of PhC de- vices. Accurate computations can provide a detailed understanding of the complex physical phenomena inherent in PhC devices. The nite-di erence time-domain (FDTD) method, which is widely used by many researchers around the Globe, is a powerful tool for modeling PhC devices. We devel- oped a modi ed and easy FDTD method based on a regular Cartesian Yee's lattice for calculating the dispersion diagram of triangular lattice PhCs. Our method uses the standard central-di erence equation, which is very easy to implement in any computing environment. The Bloch periodic boundary conditions are applied on the sides of the unit cell by translating the periodic boundary conditions to match with the directions of periodicity in the tri- angular lattice. Complete and accurate bandgap information is obtained by using this FDTD approach. Convergence, accuracy, and stability analysis were carried out, which ensures the reliability of this method. Numeri- cal results for 2-D transverse electric (TE) and transverse magnetic (TM) modes in triangular lattice PhCs are in good agreement with results from 2-D plane wave expansion method. The obtained results are in consistence with the reported ones. To ease the practical application of this method, clear explanations on the computer implementation are also provided. Finally, this dissertation addressed the use of CMOS-compatible fabrication method and 2-D periodic structures to realize the control of light in 3-D. In particular, we designed, analyzed and fabricated novel PhC waveguides utilizing Si-ion implantation and 2-D periodic structures. The transport of ions in matter (TRIM) prediction of implantation depth distribution pro le (1 1017 ions/cm2, 80 keV) shows the range of about 150 nm. Assuming the e ective refractive index of the Si-rich region to be 1.89 and by using FDTD method, the PhC design parameters based on the telecommunication wave- length ( =1.55 m) were obtained by varying the radius to lattice constant ratio (r=a) from 0.2 to 0.45. We analyzed both TE and TM mode prop- agation in triangular-lattice PhCs. The designed parameters were found to be a=664 nm and r=a=0.35. The PBG spanned from normalized fre- quency of 0.39 to 0.46 [2 c/a] in the TE-mode triangular lattice and the gap to midgap ratio was 0.16. The designed pattern was fabricated and the diameter, the period and the depth of air holes of the waveguide were estimated by atomic force microscopy (AFM) to be 464, 666 and 175 nm, respectively. Numerical results using FDTD characterization show that, straight line PhC waveguides can achieve 100% transmission, while the 60o bend showed 80% transmission owing to the dispersion mismatch at the two 60o bends. These results may serve as useful guides and components in future high- density photonic integrated circuits associated with optical communications, computing, and signal processing.学位記番号：工博甲40

NASA Tech Briefs, May 1989

This issue contains a special feature on the flight station of the future, discussing future enhancements to Aircraft cockpits. Topics include: Electronic Components and Circuits. Electronic Systems, Physical Sciences, Materials, Computer Programs, Mechanics, Machinery, Fabrication Technology, and Mathematics and Information Sciences

Vector finite element optimisation of compact spot-size converters in photonics integrated circuits

It is well known that one of the major problems of integrated optical systems is the efficient coupling of photonic devices such as semiconductor lasers, amplifiers, modulators, or switches to a single mode fiber (SMF) in such a way that little or no power loss occurs. A well confined beam is needed in order to optimize the performance of a wide range of these photonic devices, because up to 90% of the optical power can be lost due to a large mismatch between their small non-circular spot-size and a SMF with a larger and circular spot-size when they are butt-coupled. Over the last 10 years several attempts have been made to close the gap and reduce such a high loss when coupling a photonic integrated circuit (PIC) to SMF. Among these is the use of a microlens or lensed fiber to enhance the coupling efficiency. However, the disadvantage of this approach is that associated sub-micron alignment tolerances lead to very high packaging costs. For a small business network, such a large cost is preventing the rapid extension of fiber-to-the-home (FTTH). This makes the problem of optical coupling a big challenge to optoelectronics researchers worldwide as huge efforts were made to expand the narrow spot-size within a PIC, such that efficient coupling to a SMF with a large spot-size can be made. Monolithically integrated spot-size converters (SSCs) have been reported recently as being used to enhance optical coupling without deteriorating alignment tolerances and majority of the expanded SSCs do incorporate tapered structures, operating very close to the modal cut-off, to expand their spot-size. In this thesis, some compact SSC designs have been carried out using the twin rib (TR), multimode interference (MMI) and silicon-on-insulator (SOI) waveguides to improve the coupling efficiency. The TR and SOI do require a tapered section in their mode of operation to expand the spot-size whereas the MMI does not need a tapered section. Some numerical techniques have been employed in this thesis as tools in the design, analysis and optimization of the above guided-wave photonics devices. The robust, versatile and accurate full-vector finite element method (FVFEM) is the backbone of all the numerical techniques, as it has been used to obtain the modal solutions of the waveguide sections of the photonic devices throughout this thesis. The FVFEM has been used in conjunction with the Least squares boundary residual (LSBR) method in the novel compact design, analysis and optimisation of 3-Core multimode waveguide as a device for improving power coupling efficiency. The transmission and reflection coefficients of the guided-waves are obtained as well. In a similar manner, the FVFEM is also used in conjunction with the finite element-based full-vector beam propagation method (FVBPM) to study the propagation of the guided-waves along the longitudinal z-direction of tapered devices for the TR and SOI waveguides. In the analysis, the propagating power, the radiation loss and the spot-size are obtained for these PICs. Tapered spot-size converters, with various high- index SOI waveguides, which consists of secondary polymeric cover, are investigated in this work. Mode beating phenomenon was observed and explained. Also the An characterisation SOI was carried in this work because of the high-index contrast of the SOI materials which is a vital information for any design Engineer since the operations depend heavily on the materials as well as the geometry of the device. The robust PML boundary conditions have been used to stem down unwanted radiations during propagation and the Pade approximation has been employed to take care of the waves propagating at wide angles to the z-axis. The incorporated popular overlap integral (OI) has been used in the determination of the coupling efficiency of the devices, which in the case of TR is 95%, and SOI is 99.25%

Miniaturized Transistors

What is the future of CMOS? Sustaining increased transistor densities along the path of Moore's Law has become increasingly challenging with limited power budgets, interconnect bandwidths, and fabrication capabilities. In the last decade alone, transistors have undergone significant design makeovers; from planar transistors of ten years ago, technological advancements have accelerated to today's FinFETs, which hardly resemble their bulky ancestors. FinFETs could potentially take us to the 5-nm node, but what comes after it? From gate-all-around devices to single electron transistors and two-dimensional semiconductors, a torrent of research is being carried out in order to design the next transistor generation, engineer the optimal materials, improve the fabrication technology, and properly model future devices. We invite insight from investigators and scientists in the field to showcase their work in this Special Issue with research papers, short communications, and review articles that focus on trends in micro- and nanotechnology from fundamental research to applications

Frequency Comb Generation From Stimulated Brillouin Scattering and Semiconductor Laser Diodes

Optical frequency combs have shown much potential in recent years to be a revolutionary tool in metrology, signals processing, and telecommunications. This dissertation is a record of our investigation of a single-section semiconductor laser diode as a portable and robust frequency comb source with the proper bandwidth and spectral coherence for spectroscopy applications. Our previous theoretical studies on stimulated Brillouin scattering demonstrated the predictive power of traveling wave models in pulsed and cascaded configurations, including calculations of Brillouin frequency comb generation. Utilizing this knowledge, a comprehensive theoretical model of semiconductor laser diodes was developed, including all carrier dynamics, cavity effects, and nonlinear phase shifts. Then, the physics and essential mechanisms of laser diode frequency comb generation were studied, focusing upon the frequency modulated nature of the output without any saturable absorber. Finally, InGaAsP / InP quantum well laser diodes, operating at 1.55 µm and 1.3 µm were fabricated and characterized, with designs specified by our theoretical models. The fabricated lasers exhibited comb behavior as predicted, generating combs with bandwidths of about 1 THz and RF linewidths of 100-250 kHz, both at 1.55 µm and 1.3 µm. These sources show much promise for spectroscopy and other frequency comb applications, paving the way toward integration in portable systems as a truly practical frequency comb source.PHDElectrical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttps://deepblue.lib.umich.edu/bitstream/2027.42/145927/1/markdong_1.pd

Conference on Binary Optics: An Opportunity for Technical Exchange

The papers herein were presented at the Conference on Binary Optics held in Huntsville, AL, February 23-25, 1993. The papers were presented according to subject as follows: modeling and design, fabrication, and applications. Invited papers and tutorial viewgraphs presented on these subjects are included

Aeronautical Engineering: a Continuing Bibliography with Indexes (Supplement 244)

This bibliography lists 465 reports, articles, and other documents introduced into the NASA scientific and technical information system in September 1989. Subject coverage includes: design, construction and testing of aircraft and aircraft engines; aircraft components, equipment and systems; ground support systems; and theoretical and applied aspects of aerodynamics and general fluid dynamics