Reconfigurable optical spectra from perturbations on elliptical whispering gallery resonances

Elastic strain, electrical bias, and localized geometric deformations were applied to elliptical whispering-gallery-mode resonators fabricated with lithium niobate. The resultant perturbation of the mode spectrum is highly dependant on the modal indices, resulting in a discretely reconfigurable optical spectrum. Breaking of the spatial degeneracy of the whispering-gallery modes due to perturbation is also observed

Optical Lattice Trap for Kerr Solitons

We show theoretically and numerically that dichromatic pumping of a nonlinear microresonator by two continuous wave coherent optical pumps creates an optical lattice trap that results in the localization of intra-cavity Kerr solitons with soliton positions defined by the beat frequency of the pumps. This phenomenon corresponds to the stabilization of the Kerr frequency comb repetition rate. The locking of the second pump, through adiabatic tuning of its frequency, to the comb generated by the first pump allows transitioning to single-soliton states, manipulating the position of Kerr solitons in the cavity, and tuning the frequency comb repetition rate within the locking range. It also explains soliton crystal formation in resonators supporting a dispersive wave emitted as a result of higher-order group velocity dispersion or avoided mode crossing. We show that dichromatic pumping by externally stabilized pumps can be utilized for stabilization of microresonator-based optical frequency combs when the comb span does not cover an octave or a significant fraction thereof and standard self-referencing techniques cannot be employed. Our findings have significant ramifications for high-precision applications of optical frequency combs in spectrally pure signal generation, metrology, and timekeeping.Comment: 13 pages, 12 figure

Generation of optical frequency combs with a CaF2 resonator

We demonstrate optical frequency combs using the fluorite whispering gallery mode resonator as a nonlinear Kerr medium. Two regimes of generation are observed, giving the record low repetition rate of 13 GHz, equal to the cavity's free spectral range (FSR) or high repetition rates of multiples of cavity FSR. An intermediate regime was also observed. Raman lasing spectrum similar to modulation instability in fibers was observed for the first time to the best of our knowledge

Flicker noise in high-speed p-i-n photodiodes

The microwave signal at the output of a photodiode that detects a modulated optical beam contains the phase noise phi(t) and the amplitude noise alpha(t) of the detector. Beside the white noise, which is well understood, the spectral densities S_phi(f) and S_alpha(f) show flicker noise, proportional to 1/f. We report on the measurement of the phase and amplitude noise of high-speed p-i-n photodiodes. The main result is that the flicker coefficient of the samples is approximately 1E-12 rad^2/Hz (-120dB) for phase noise, and approximately 1E-12 Hz^-1 (-120dB) for amplitude noise. These values could be observed only after solving a number of experimental problems and in a protected environment. By contrast, in ordinary conditions insufficient EMI isolation, and also insufficient mechanical isolation, are responsible for additional noise to be taken in. This suggests that if package and EMC are revisited, applications can take the full benefit from the surprisingly low noise of the p-i-n photodiodes.Comment: 11 pages, 3 figures, 24 reference

Perception of Ticket Scalping In New York State

The development and growth of the secondary ticket market over the last few decades was discussed, in order to see how it has become what it is today. The goal of the research is to see how people living in New York perceive ticket scalping and whether or not they respect the law. The expanding use and popularity of secondary websites such as StubHub are discussed, and how most transactions take place over the internet. Additionally, the current trends in the ticketing industry are mentioned and how organizations have attempted to curb scalping over the last few years. As a result, the basic recommendation is that the secondary market should either be free, or there should be a uniform federal law to place each state under the same restrictions

Durability of calcium-aluminate based binders for rapid repair applications

Within the last few decades, the amount of vehicle miles traveled within the US has increased approximately 40% with the construction of new roads only increasing 4% during this same time period. This dramatic increase in traffic on existing infrastructure has led to the rapid decline of the condition our nation’s roads resulting in the increased need for maintenance and repair. Rapid hardening repair materials are in high demand for these applications as they allow for minimal traffic delays and road closures. Calcium aluminate cement (CAC) is a rapid hardening binder that is used for specialty applications where high early strength and increased durability are desired. In recent years, blended cement systems incorporating both CAC and calcium sulfate (C$) with portland cement (PC) have been developed to utilize the rapid hardening characteristics of CAC but at a reduced cost. While the durability of CAC is well researched and documented, the durability of these new blended systems is not yet fully understood. The focus of this research was to evaluate the performance and long term durability of various blended systems which utilize CAC or calcium sulfoaluminate cement (CSA) to attain rapid hardening. More specifically, these systems were evaluated to determine their resistance to common modes of concrete deterioration such as alkali-silica reaction, external sulfate attack, delayed ettringite formation, carbonation, and corrosion in marine environments through in-situ lab methods and large scale outdoor exposure. The results of the testing conducted related to alkali-silica reaction, external sulfate attack, and delayed ettringite formation identified the potential for large levels of expansion in blended systems of PC:CAC:C$ and PC:CSA. Details regarding each mode of deterioration and mechanisms of expansion are discussed.Civil, Architectural, and Environmental Engineerin