Bulletin of the American Physical Society
2016 Annual Meeting of the APS Mid-Atlantic Section
Volume 61, Number 16
Saturday–Sunday, October 15–16, 2016; Newark, Delaware
Session B3: Optical Science I |
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Chair: Patrick Grugan, University of Delaware Room: Sharp Laboratory 131 |
Saturday, October 15, 2016 11:00AM - 11:36AM |
B3.00001: Control of second harmonic generation using counterpropagating light Invited Speaker: Amy Lytle The main challenge for conversion efficiency of nonlinear frequency conversion processes like second harmonic generation is the chromatic dispersion of the nonlinear medium. The phase mismatch between the different frequencies is typically corrected by exploiting birefringence or through construction of layered nonlinear media to achieve quasi-phase matching. An all-optical method of quasi-phase matching using counterpropagating light has recently been demonstrated for high-order harmonic generation. Sequences of counterpropagating pulses are used to interfere with the harmonic generation process periodically, correcting the phase mismatch and boosting efficiency. The correction is achieved by a microscopic disruption of the phase-matching conditions caused locally by each counterpropagating pulse. We have extended the application of this mechanism to second-harmonic generation, and show an explicit measurement of this microscopic phase disruption for the first time. Numerical simulations reproduce the features of the observed disruption and indicate pathways for implementing in situ probing and quasi-phase matching of second-harmonic generation with counterpropagating fields. [Preview Abstract] |
Saturday, October 15, 2016 11:36AM - 11:48AM |
B3.00002: Divergence angle characterization of THz radiation from two-color laser filamentation in air Yungjun Yoo, Donghoon Kuk, Zheqiang Zhong, Ki-Yong Kim We have characterized the divergence angle of terahertz (THz) radiation produced via femtosecond two-color laser mixing in air. In this scheme, a femtosecond laser pulse is mixed with its second harmonic pulse to generate air plasma and simultaneous THz radiation in the far field. To measure the divergence angle, we have performed THz beam profiling at various positions along its propagation direction. In particular, we have investigated the dependence of beam focusing geometry (f-number) and THz radiation frequency. To test the f-number effect, we have varied the numerical aperture (NA) of incoming laser from 0.01 to 0.06 by using different focal length lenses. Also, to investigate the frequency dependence, we have used bandpass metallic THz filters in front of our pyroelectric or uncooled microbolometer (tau2, FLIR) detectors. We find that the THz radiation angle is greatly affected by the laser focusing geometry. For real-time THz imaging, lock-in detection is applied to the microbolometer camera, which yields an improved signal-to-noise ratio at our detection bandwidth (1\textasciitilde 30 THz). [Preview Abstract] |
Saturday, October 15, 2016 11:48AM - 12:00PM |
B3.00003: Chalcopyrite Crystals. Herath Pathiranage Piyathilaka, Derek Bas, Kevin Zawilski, Peter Schunemann, Alan Bristow CdSiP$_{\mathrm{2}}$ (CSP) and CdGeP$_{\mathrm{2}}$ (CGP) are negative uniaxial II-IV-V$_{\mathrm{2}}$ chalcopyrite compound semiconductors. Optical rectification is demonstrated in CSP and CGP providing terahertz (THz) generation. These sources are compared to ZnGeP$_{\mathrm{2}}$ (ZGP)$^{\mathrm{[1]}}$ over a wavelength range of 1200 nm to 2320 nm at an average pump power 3.7 mW and emission strength is fitted to these two dependencies. During this analysis $\alpha $ (linear absorption coefficient), $\beta $ (two-photon absorption), and $\gamma $ (three-photon absorption) are taken into an account while comparing with the values of the ZGP and a conclusion is made of the properties of CSP and CGP. [1] J. D. Rowley\textit{ et al,} Optics Letters, Vol. 37, No. 5 (2012) [Preview Abstract] |
Saturday, October 15, 2016 12:00PM - 12:12PM |
B3.00004: Two-photon Resonant Ramsey Interference using a Repeated-Query Scheme for Atomic Clock Development Zachary Warren, Renu Tripathi, Gour Pati For communication and navigation, precision atomic clock technology relies on optical resonances with narrow linewidths and high signal-to-noise ratios. Continuous optical pumping of rubidium atoms produces stable and coherent atomic dark state resonances with some limitations. To overcome power broadening and light shift, an optical two-pulse sequence comprising of a coherent population trapping (CPT) preparation pulse and short query pulse is used to generate and detect Ramsey interference fringes. The fringe-width of Ramsey interference is decided by the free evolution time, T, the time separation between the two pulses. Often, Ramsey fringes produced by two-photon frequency detuning have nearly uniform amplitude around the frequency sweep center, and the central fringe can be nearly indistinguishable from the surrounding ones. We introduce a repeated-query scheme using periodic query pulses for the Ramsey interrogation. Unlike the two-pulse scheme, the repeated-query scheme enhances the central fringe amplitude while suppressing the side fringes. We have conducted numerical simulations and experiments to demonstrate the effectiveness of the repeated-query scheme. Applying the scheme to future clock experiments would show increased stability relative to the two-pulse method. [Preview Abstract] |
Saturday, October 15, 2016 12:12PM - 12:36PM |
B3.00005: Design of many-body spin states of Rydberg atoms excited to highly tunable magnetic sublevels Svetlana Malinovskaya Quantum control methodology is presented to design many-body spin states in a spin chain of Rydberg atoms using laser pulses and the magnetic field. Two-photon ladder type configuration is implemented, which is advantageous due to a combined action of the one-photon and two-photon detunings as control parameters. Many-body spin states are designed of an ensemble of spins encoded in sublevels of Rydberg states and interacting through the van der Waals interactions. [Preview Abstract] |
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