Automated wavelength recovery for silicon photonics

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2013.Cataloged from PDF version of thesis.Includes bibliographical references.In 2020, 1Tb/s on-/off-chip communication bandwidth and ~100fJ/bit total energy in a point to point link is predicted by Moore's law for high performance computing applications. These requirements are pushing the limits of on-chip silicon CMOS transistors and off-chip VCSELs technology. The major limitation of the current systems is the lack of ability to enable more than a single channel on a single wire/fiber. Silicon photonics, offering a solution on the same platform with CMOS technology, can enable Wavelength Division Multiplexed (WDM) systems. However, Silicon photonics has to overcome the wafer level, fabrication variations and dynamic temperature fluctuations, induced by processor cores with low-energy high-speed resonators. In this work, we offer a solution, called as Automated Wavelength Recovery (AWR), to these limitations. In order to demonstrate AWR, we design and demonstrate high performance active silicon resonators. A microdisk modulator achieved open eye-diagrams at a data rate of 25Gb/s and error-free operation up to 20Gb/s. A thermo-optically tunable microdisk modulator with Low power modulation (1 If/bit) at a data rate of 13-Gb/s, a 5.8-dB extinction ratio, a 1.22-dB insertion loss and a record-low thermal tuning (4.9-[mu].W/GHz) of a high-speed modulator is achieved. We demonstrated a new L-shaped resonant microring (LRM) modulator that achieves 30 Gb/s error-free operation in a compact (< 20 [mu]m²) structure while maintaining single-mode operation, enabling direct WDM across an uncorrupted 5.3 THz FSR. We have introduced heater elements inside a new single mode filter, a LRM filter, successfully. The LRM filter achieved high-efficiency (3.3[mu]W/GHz) and high-speed ([tau]f ~1.6 [mu]s) thermal tuning and maintained signal integrity with record low thru to drop power penalty (<1.1 dB) over the 4 THz FSR and <0.5dB insertion loss. We have integrated a heater driver and adiabatic resonant microring (ARM) filter in a commercial bulk CMOS deep-trench process for the first time. The proposed AWR algorithm is implemented with an ARM multiplexer. An advanced method for AWR is also introduced and demonstrated with passive resonators.by Erman Timurdogan.S.M

Optical sampling and metrology using a soliton-effect compression pulse source

A low jitter optical pulse source for applications including optical sampling and optical metrology was modelled and then experimentally implemented using photonic components. Dispersion and non-linear fibre effects were utilised to compress a periodic optical waveform to generate pulses of the order of 10 picoseconds duration, via soliton-effect compression. Attractive features of this pulse source include electronically tuneable repetition rates greater than 1.5 GHz, ultra-short pulse duration (10-15 ps), and low timing jitter as measured by both harmonic analysis and single-sideband (SSB) phase noise measurements. The experimental implementation of the modelled compression scheme is discussed, including the successful removal of stimulated Brillouin scattering (SBS) through linewidth broadening by injection dithering or phase modulation. Timing jitter analysis identifies many unwanted artefacts generated by the SBS suppression methods, hence an experimental arrangement is devised (and was subsequently patented) which ensures that there are no phase modulation spikes present on the SSB phase noise spectrum over the offset range of interest for optical sampling applications, 10Hz-Nyquist. It is believed that this is the first detailed timing jitter study of a soliton-effect compression scheme. The soliton-effect compression pulses are then used to perform what is believed to be the first demonstration of optical sampling using this type of pulse source. The pulse source was also optimised for use in a novel optical metrology (range finding) system, which is being developed and patented under European Space Agency funding as an enabling technology for formation flying satellite missions. This new approach to optical metrology, known as Scanning Interferometric Pulse Overlap Detection (SIPOD), is based on scanning the optical pulse repetition rate to find the specific frequencies which allow the return pulses from the outlying satellite, i.e. the measurement arm, to overlap exactly with a reference pulse set on the hub satellite. By superimposing a low frequency phase modulation onto the optical pulse train, it is possible to detect the pulse overlap condition using conventional heterodyne detection. By rapidly scanning the pulse repetition rate to find two frequencies which provide the overlapping pulse condition, high precision optical pulses can be used to provide high resolution unambiguous range information, using only relatively simple electronic detection circuitry. SIPOD’s maximum longitudinal range measurement is limited only by the coherence length of the laser, which can be many tens of kilometres. Range measurements have been made to better than 10 microns resolution over extended duration trial periods, at measurement update rates of up to 470 Hz. This system is currently scheduled to fly on ESA’s PROBA-3 mission in 2012 to measure the intersatellite spacing for a two satellite coronagraph instrument. In summary, this thesis is believed to present three novel areas of research: the first detailed jitter characterisation of a soliton-effect compression source, the first optical sampling using such a compression source, and a novel optical metrology range finding system, known as SIPOD, which utilises the tuneable repetition rate and highly stable nature of the compression source pulses

QUANTUM SIMULATIONS OF THE ISING MODEL WITH TRAPPED IONS: DEVIL'S STAIRCASE AND ARBITRARY LATTICE PROPOSAL

A collection of trapped atomic ions represents one of the most attractive platforms for the quantum simulation of interacting spin networks and quantum magnetism. Spin-dependent optical dipole forces applied to an ion crystal create long-range eective spin-spin interactions and allow the simulation of spin Hamiltonians that possess nontrivial phases and dynamics. We trap linear chains of 171Yb+ ions in a Paul trap, and constrain the occupation of energy levels to the ground hyperne clock-states, creating a qubit or pseudo-spin 1/2 system. We proceed to implement spin-spin couplings between two ions using the far detuned Mlmer-Srenson scheme and perform adiabatic quantum simulations of Ising Hamiltonians with long-range couplings. We then demonstrate our ability to control the sign and relative strength of the interaction between three ions. Using this control, we simulate a frustrated triangular lattice, and for the first time establish an experimental connection between frustration and quantum entanglement. We then scale up our simulation to show phase transitions from paramagnetism to ferromagnetism for nine ions, and to anti-ferromagnetism for sixteen ions. The experimental work culminates with our most complicated Hamiltonian - a long range anti-ferromagnetic Ising interaction between 10 ions with a biasing axial field. Theoretical work presented in this thesis shows how the approach to quantum simulation utilized in this thesis can be further extended and improved. It is shown how appropriate design of laser elds can provide for arbitrary multidimensional spin-spin interaction graphs even for the case of a linear spatial array of ions. This scheme uses currently existing trap technology and is scalable to levels where classical methods of simulation are intractable

Advances in Optical Amplifiers

Optical amplifiers play a central role in all categories of fibre communications systems and networks. By compensating for the losses exerted by the transmission medium and the components through which the signals pass, they reduce the need for expensive and slow optical-electrical-optical conversion. The photonic gain media, which are normally based on glass- or semiconductor-based waveguides, can amplify many high speed wavelength division multiplexed channels simultaneously. Recent research has also concentrated on wavelength conversion, switching, demultiplexing in the time domain and other enhanced functions. Advances in Optical Amplifiers presents up to date results on amplifier performance, along with explanations of their relevance, from leading researchers in the field. Its chapters cover amplifiers based on rare earth doped fibres and waveguides, stimulated Raman scattering, nonlinear parametric processes and semiconductor media. Wavelength conversion and other enhanced signal processing functions are also considered in depth. This book is targeted at research, development and design engineers from teams in manufacturing industry, academia and telecommunications service operators

Design and Development of an Optical Chip Interferometer For High Precision On-Line Surface Measurement

Advances in manufacturing and with the demand of achieving faster throughput at a lower cost in any industrial setting have put forward the need for embedded metrology. Embedded metrology is the provision of metrology on the manufacturing platform, enabling measurement without the removal of the workpiece. Providing closer integration of metrology upon the manufacturing platform will improve material processing and reliability of manufacture for high added value products in ultra-high-precision engineering. Currently, almost all available metrology instrumentation is either too bulky, slow, destructive in terms of damaging the surfaces with a contacting stylus or is carried out off-line. One technology that holds promise for improving the current state-of-the-art in the online measurement of surfaces is hybrid photonic integration. This technique provides for the integration of individual optoelectronic components onto silicon daughter boards which are then incorporated on a silica motherboard containing waveguides to produce a complete photonic circuit. This thesis presents first of its kind a novel chip interferometer sensor based on hybrid integration technology for online surface and dimensional metrology applications. The complete metrology sensor system is structured into two parts; hybrid photonic chip and optical probe. The hybrid photonic chip interferometer is based on a silica-on-silicon etched integrated-optic motherboard containing waveguide structures and evanescent couplers. Upon the motherboard, electro-optic components such as photodiodes and a semiconductor gain block are mounted and bonded to provide the required functionality. Optical probe is a separate entity attached to the integrated optic module which serves as optical stylus for surface scanning in two measurement modes a) A single-point for measuring distance and thus form/surface topography through movement of the device or workpiece, b) Profiling (lateral scanning where assessment of 2D surface parameters may be determined in a single shot. Wavelength scanning and phase shifting inteferometry implemented for the retrival of phase information eventually providing the surface height measurement. The signal analysis methodology for the two measurement modes is described as well as a theoretical and experimental appraisal of the metrology capabilities in terms of range and resolution. The incremetal development of various hybrid photonic modules such as wavelength encoder unit, signal detection unit etc. of the chip interferometer are presented. Initial measurement results from various componets of metrology sensor and the surface measurement results in two measurement modes validate the applicability of the described sensor system as a potential metrology tool for online surface measurement applications

Optoelectronics – Devices and Applications

Optoelectronics - Devices and Applications is the second part of an edited anthology on the multifaced areas of optoelectronics by a selected group of authors including promising novices to experts in the field. Photonics and optoelectronics are making an impact multiple times as the semiconductor revolution made on the quality of our life. In telecommunication, entertainment devices, computational techniques, clean energy harvesting, medical instrumentation, materials and device characterization and scores of other areas of R&D the science of optics and electronics get coupled by fine technology advances to make incredibly large strides. The technology of light has advanced to a stage where disciplines sans boundaries are finding it indispensable. New design concepts are fast emerging and being tested and applications developed in an unimaginable pace and speed. The wide spectrum of topics related to optoelectronics and photonics presented here is sure to make this collection of essays extremely useful to students and other stake holders in the field such as researchers and device designers