Y. Fattal, “Soliton shedding from Airy pulse in Kerr media,” 2012. Publisher's VersionAbstract

An Airy pulse, a solution of the dispersion equation, manifests two unique properties while propagating in linear media. One is self-similarity, meaning the pulse has the same envelope throughout propagation in dispersive media and the second is acceleration in time- namely moving in parabolic trajectory with respect to a time frame that moves with the group velocity of the pulse.
We simulate and analyze the propagation of truncated temporal Airy pulses in a single mode fiber in the presence of self-phase modulation (Kerr effect) and anomalous dispersion. Due to the presence of the nonlinear effect, the Airy is no longer a valid solution, such that the pulse evolution is no more predictable.
By gradually increasing the launched Airy power we examine the nonlinearity influence on the Airy pulse evolution. For sufficient large launched intensity we observe soliton pulse shedding from the Airy main lobe, with the emergent soliton parameters dependent on the launched Airy pulse characteristics. The emergent soliton performs "breathing"- periodic oscillations of its parameters along the propagation distance due to interaction with background radiation, with the periodicity increasing with the launched power. Additionally, the soliton mean temporal position shifts to earlier times with higher launched powers due to an earlier shedding event and with greater energy in the Airy tail due to collisions with the accelerating lobes. In spite of the Airy energy loss to the shed Soliton, the Airy pulse continues to exhibit the unique property of acceleration in time and the main lobe recovers from the energy loss (healing property of Airy waveforms), but performs decaying oscillations of its peak power according to the interplay between the dispersion and the nonlinear effect.
The influence of the truncation coefficient—required for limiting the Airy pulse to finite energy—on the Airy nonlinear propagation is also investigated. Small truncation degree increases the Airy tail energy, which has considerable influence on the soliton shedding distance, the soliton mean temporal position, and on the residual accelerating energy.

J. Dunayevsky, “MEMS Spatial Light Modulator for Spectral Phase and Amplitude Modulation,” 2010. Publisher's VersionAbstract

A diffractive Micro-Electro-Mechanical-system (MEMS) modulator is developed for modulating spectral components of incident light within the optical communication band. This diffractive MEMS spatial light modulator (SLM) is to be used for independently applying amplitude attenuation and phase control along one dimension. This enables a variety of applications for MEMS SLM devices such as channel selective attenuation, pulse shaping, chromatic dispersion compensation and more. The fabrication took place at Sandia National Laboratories where a predefined SUMMiT V process for MEMS designs exists. Furthermore, this fabrication process imposes constraints layer thicknesses. In addition two other constraints govern the design: the available voltage range (0-160 volts), and the need for the smallest mirror possible, due to the need of high resolution, were key factors in the design of the device. The electromechanical behavior of the device was well predicted using analytic calculation and FEA simulations. This thesis describes electrostatic technique and mechanical design features for realizing planar vertical travel in an electrostatically actuated diffractive optical device, which is robust, both to manufacture, and against pull-in. This device consists of many square elements, each 36 micron on a side. These elements act as reflective mirrors spanning a 2D rectilinear space with high fill factor. The mirrors can travel up to about 1.2 microns in the out-of-plane direction for applied voltage of 130 volts. The eigenfrequency of the device is about 24KHz.

Y. Glazer, “Novel Polymeric Waveguides Optimized for Nanocrystal Hosting,” 2009. Publisher's VersionAbstract

At the last decade, the wide growth in data transfer realized the requirement of optical communications for its high capacity capabilities. The revolution of optical communications has been enabled by the availability of ultra-low-loss silica fiber, which has also been the basis for a wide variety of optical building blocks.
Fabricating passive optical devices from high purity silica and glass, or fabricating active devices that utilize the direct band gap of semiconductors (SC) are relatively costly; therefore alternative solutions are being studied widely.
Our research is aiming to realize a platform based on passive polymer materials as the wave-guiding material, and in the future to dope it with SC nanocrystals (NC). Plastic (polymers) optical fiber has already found significant application in the Datacom market.
In this work we present the design of optical devices and their fabrication. Polymer selection is critical, as most polymers have CO and CH absorption bands which reside near 1.55m wavelength. A PFCB core and a Cytop as cladding were chosen and combined together for the first time. This two polymers combination offers a very small attenuation at the optical communication wavelength of 1.55m, high Δn and solubility with NC.
At the design process, we focused on realizing devices that will help us extract the basic characteristic of our polymer platform, such as propagation losses, bend losses and reflective index changes that will occur after NC doping.
Realizing polymeric waveguides with a micron-scale cross section of and length of a few centimeters has low defect tolerance which requires careful treatment. Fabrication was done with standard semiconductor process, such as lithography, reactive ion etching etc. Furthermore, a low preparation temperature is critical when heat-sensitive elements, such as semiconductors nanocrystals, are to be embedded in the waveguide. Finally, after the process development, we have the desired polymeric waveguide structure. This waveguide platform is now ready for future study of NC dopants.

Y. Palti, “Complex Optical (Amplitude and Phase) Device Characterization Tool,” 2009. Publisher's VersionAbstract

Optical communications has experienced a rapid development during the last decade. More bandwidth can be acquired by decreasing the spacing of the optical channels or by increasing the data rate. Characterization of the optical components and active monitoring of the network calls for accurate measurement methods. The transfer function of optical components impacts
the performance of communication systems. Analysis and accurate measurement of the transfer function is therefore essential in optimization of the performance of such systems.
Chromatic dispersion of optical bers and frequency chirp of the laser transmitters set limits for the data rate and transmission distance. Measurements of dispersion have traditionally been performed using a Modulation Phase-Shift (MPS) method. When high RF modulation frequencies are applied to achieve high resolution an alias error could be introduced. In this thesis we introduce an apparatus for full complex-amplitude spectral characterization of optical
components and bers. Based on a modication of the MPS method, we introduce a frequency dither to the RF modulation drive, allowing us to detect small phase changes thus overcoming the limitations imposed by the conventional MPS method. Its salient feature is high sensitivity phase detection enabling the use of a low RF driving frequency as necessary for precise measurement of components exhibiting fine spectral features such as microresonators and slow light devices. 
We analyze the modied MPS technique using the traditional small signal approximation and compare the results to a full analytic response of the MPS technique. The full analytic response is useful for optimization of the proposed technique. The characterization apparatus has been realized in our lab using commercially available optical and electrical components. We have characterized experimentally the signals passing in the apparatus. Care was taken to prevent higher RF tones (i.e. above 1st order) in the Mach-Zehnder Modulator (MZM) output field, which could interfere with the desired measurement. Moreover, care was taken to prevent RF leakages in the electronic circuitry, which could interfere with the measurement of weak signals. We demonstrate the operation of the modified MPS at two operating points, demodulating with either the same RF carrier or with a doubled one. We measured several component categories and fibers to demonstrate the measurement technique. Finally, we conclude with the advantages and disadvantages of the modified technique.

  • «
  • 2 of 2