Browsing by Subject "Physics, Optics (0752)"
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Item CO2 Laser System for Re-flow of Toroidal Micro-cavities(2008-12-04) Roettgen, Christopher David; Franson, James D; Physics; Physics, AppliedToroid optical micro-cavities are emerging as the leading micro-cavity type for a variety of research areas and applications. The desirable properties of these cavities degrade with exposure to the atmosphere following the final step of production. A facility was designed and constructed allowing the final step in production of toroid micro-cavities, re-flow, to be performed locally, just prior to use. This facility consists of a high power CO2 laser for heating and re-flowing fused silica, a visible laser for targeting, a computer controlled multi-axis translation system for targeting, and a high resolution imaging system. The facility was tested successfully and several micro-cavities were completed. A model describing the re-flow process was developed and tested against observations. Having found discrepancies between the model and observations the model was revised, and successfully describes observations. Multiple procedures for the re-flow process were tested leading to finding the best practices and recommendations for future improvement and use.Item Design and Characterization of a Tunable Fabry-Perot Filter using an Electro-Optic Modulated Spacer Layer(2007-11-26) French, Joseph; Hayden, L. Michael; Physics; Physics, AppliedTunable Fabry-Perot filters are used in several commercial and research areas. Using an electro-optic material as a spacer layer provides an efficient way to modulate the optical path length of the etalon cavity. The design and characterization of a tunable Fabry-Perot using an electro-optic polymer as the spacer layer has been performed. The clamped Fabry-Perot devices with finesses of 40-60 showed a quadratic peak shift with applied voltage. Creep was observed in the clamped devices and a theoretical model using a viscoelastic liquid Generalized Kelvin-Voigt configuration was developed to account for the clamp's contribution to the peak shift. Glued Fabry-Perot devices were fabricated and found to have an air gap. Theoretical models taking into account the air gap were developed to explain the peak shift. The glued devices also showed a quadratic dependency with applied voltage. The measured values for the peak shift were compared to predicted values using the electro-optic coefficient r13, piezoelectric coefficient d33, and Young's modulus Y of the glue.Item FIBER-BASED LASER TRANSMITTER AND LASER SPECTROSCOPY OF THE OXYGEN A-BAND FOR REMOTE DETECTION OF ATMOSPHERIC PRESSURE(2008-08-21) Stephan, Mark Andrew; Hayden, L. M.; Physics; Physics, AppliedThe Author reports on the design and construction of an oxygen spectroscopy laser sounding instrument designed to measure atmospheric pressure. This instrument was conceived and designed with a satellite application in mind so we discuss the requirements this places on the instrument and specifically the laser transmitter. We have developed a novel, pulsed, frequency-doubled, fiber-based laser transmitter for use in the instrument. The instrument concept uses the collision broadening of spectroscopic lines of the diatomic oxygen A-band to deduce atmospheric pressure. We report on the spectroscopic and instrument theory. We discuss the development of a high-power, narrow-frequency, tunable, single spatial mode pulsed laser transmitter. The transmitter is a master oscillator power amplifier (MOPA) design. The master oscillator is a fiber coupled DFB laser with external acousto-optic modulation. The amplifier is a diode pumped, erbium-doped fiber. We discuss the non-linear optical effect of stimulated Brillouin scattering (SBS) and how it limits the transmitter performance. We review various methods for overcoming SBS in erbium fiber amplifiers and then demonstrate the performance of a high SBS threshold fiber amplifier. We demonstrate the efficacy of this transmitter by integrating it into a spectroscopic instrument and make atmospheric measurements at a test site at Goddard. We also discuss future improvements.Item Improved Technologies for a Single Photon Source(2008-01-01) Herrera, Michael Bernardo; Pittman, Todd B; Physics; Physics, AppliedThe efforts of this research have been directed towards improving both the heralding efficiency and heralding rates of a high performance fiber-coupled single photon source based on an ultrafast pulsed beam-like Type-II parametric down conversion (PDC) source. Entangled photons generated from PDC are inherently broadband (many frequencies) and exit the nonlinear crystal at varying angles (different directions). This makes coupling the photons into single-mode fibers, a desirable feature for quantum computing, difficult. In response to these difficulties we have explored applying multi-layered thin film broadband anti-reflection coatings onto the ends of single-mode fibers using the technique of RF Planar Magnetron Sputtering in an effort to increase the coupling efficiency of the beam-like down converted photons. In addition, we have explored theoretically the broadband nature of novel phase matching geometries to increase heralding rates and minimize photon losses. With the ability to tailor coupling fibers to various down conversion sources we hope to increase both the heralding efficiency and heralding rate to levels needed for a broad range of future experiments.Item Transverse Correlation in Entangled Photons and Light-Matter Interaction(2007-07-12) Wen, Jianming; Rubin, Morton H.; Physics; Physics, AppliedIn recent years, quantum entanglement has attracted much; attention, because its unique properties provide potential; applications, which could not be achieved using conventional; techniques, such as quantum computing, quantum imaging and; lithography. To realize these advancements, one has to obtain an; entanglement-generation source, thoroughly master its physical; properties, and fully understand the light-matter interaction.; This dissertation is an attempt to address such issues as stated; above.; Conventionally, paired photons are created from; \textit{spontaneous parametric down-conversion} (SPDC). It is; known that the transverse correlation in biphotons may improve the; visibility and resolution in quantum imaging and lithography. In; this thesis, we described an alternative biphoton source --; Raman-EIT (\textit{electromagnetically induced transparency}); generator, and emphasize on its geometrical and optical; properties. We found that to utilize the transverse effects in; paired Stokes-anti-Stokes, it is necessary to make the product of; the EIT window times the group delay much greater than unity.; To gain further insight into quantum imaging and lithography, we; studied the transverse correlation in triphoton entanglement; theoretically. We found that in the two-image process, the quality; of images is determined by the optical path-lengths, even though; the Gaussian thin lens equations are satisfied. The ghost; interference-diffraction patterns of double slits show one more; fold interference, which is essentially different from the; biphoton case. Klyshko's advanced-wave model is still applicable,; with some modifications. We also generalized the transverse; correlation to the case of multi-photon entangled states.; To implement quantum computing, one key element is quantum memory.; In this thesis, we have theoretically explored the feasibility of; such a memory by using nonclassical SPDC light in an EIT system at; the single-photon level. We found that both the quantum coherence; of SPDC and atomic coherence of EIT can survive after interacting; within a vapor cell. Due to the inherent mismatch of magnitude; between the spectral bandwidth of SPDC and the very narrow; transmission width of EIT, the coincidence counts of the; two-photon interference is reduced to one pair per second, which; is barely doable in the current experimental situation.