Bulletin of the American Physical Society
APS March Meeting 2010
Volume 55, Number 2
Monday–Friday, March 15–19, 2010; Portland, Oregon
Session V29: Optical/Laser Devices and Applications |
Hide Abstracts |
Sponsoring Units: FIAP Chair: Anthony Johnson, University of Maryland-Baltimore County Room: C123 |
Thursday, March 18, 2010 8:00AM - 8:12AM |
V29.00001: Integrated E-field and B-field sensor using electro-optic and magneto-optic materials Anthony Garzarella, Dong Ho Wu In this presentation, we describe an integrated, fiber optic, electro-optic (EO) and magneto-optic (MO) sensor for the detection and measurement of electric and magnetic fields. Conventional sensors such as dipole and loop antennas are metallic-based, thereby perturbing the very fields they measure. Additionally, metallic probes cannot be used high power microwaves, large magnetic fields, or in small cavities. EO sensors (based on the Pockels Effect) and MO sensors (based on the Faraday rotation) are small in size (a few mm$^{2})$, have large bandwidths, and detect external electric and magnetic fields optically without the use of metallic components in the sensorhead. In spite of their intrinsic advantages, EO and MO sensors are rarely used in actual field measurement applications and are confined to more research-oriented laboratory applications due to low sensitivity, optical phase noise and other limitations. In this presentation, we describe an integrated EO and MO sensor which overcomes many of these obstacles and has been used in a variety of field tests involving numerous sources of electric and magnetic fields. Experimental data is presented with power levels from tens of milliwatts to several megawatts and frequencies from dc to 10 GHz. [Preview Abstract] |
Thursday, March 18, 2010 8:12AM - 8:24AM |
V29.00002: Design, Fabrication, and Measurement of a MEMS Fabricated 220 GHz Slow Wave Structure Mark Field, Robert Borwick, Berinder Brar, Young-Min Shin, Neville Luhmann, Larry Barnett We report on the development, fabrication and RF test of a MEMS fabricated structure designed to slow 220 GHz radiation to a group velocity of 8.15E7 m/s (approximately 27{\%} the speed of light in vacuum). This slow wave structure is designed to operate within a travelling wave tube microwave amplifier, where the group velocity of the radiation matches the electron beam velocity from a 20 keV source. The slow wave structure uses two TE mode gratings in the form of vanes within a waveguide. The two set of vanes on the top and bottom of the waveguide have a phase shift between them resulting in a staggered vane circuit, which provides more than 50 GHz wide bandwidth around the operational frequency of 220 GHz. The measured group velocity remains constant across the operating band. MEMS fabrication techniques have been developed which control the etch processes to produce vertical sidewalls while keeping the surface roughness to an acceptable level. [Preview Abstract] |
Thursday, March 18, 2010 8:24AM - 8:36AM |
V29.00003: Tunable and Broadband Nonlinear Nanomechanical Resonators Hanna Cho, Min-Feng Yu, Alexander F. Vakakis, Lawrence A. Bergman, D. Michael McFarland Recent advance has seen the development of nanomechanical resonators operated in the linear regime that are capable of detecting extremely small physical quantities and even quantum interactions. However, the reduced device size reduces its dynamic range (down to nanometer) for linear operation, which makes developing the required measurement system difficult and accordingly limits their sensitivity, especially in ambient and room temperature environments. We design and develop a conceptually new nanomechanical resonator integrating an essential nonlinearity, which consists of a simple doubly clamped carbon nanotube driven with an oscillating concentrated force. We demonstrate the RF broadband nanoresonator that realizes a tunable bandwidth over three times its natural frequency and a room temperature mass sensitivity up to 0.1 zg/ Hz, over two orders of magnitude better than the corresponding linear nanoresonator. This intrinsically nonlinear design can be readily integrated into the ongoing development of nanoscale electromechanical systems to extend their practical operation for ultrahigh sensitivity sensing. [Preview Abstract] |
Thursday, March 18, 2010 8:36AM - 8:48AM |
V29.00004: Real-Time THz Imaging Using Full-Field Electro-Optic Sampling A. Ayesheshim, I. Bushfield, F.A. Hegmann Real time terahertz imaging offers diverse opportunities and applications for non-destructive imaging applications [1,2]. In this paper, we demonstrate real-time THz imaging of still, moving, and concealed objects. Using a Ti: sapphire amplifier laser system, a THz beam is generated and detected via optical rectification and EO sampling respectively using [110] ZnTe wafers. Real time THz video rate imaging of metal objects and dripping water within a cardboard cylinder are clearly seen by an 8-bit grayscale CCD camera. The ring-like temporal and spatial intensity distribution of the various frequency components of the THz signal on the focal plane is also studied. To improve SNR, we use frame averaging and dynamic subtraction methods [3]. \\[4pt] [1] B .B. Hu and M. C. Nuss, \textit{Opt.Lett. 20, 1716(1995).} \\[0pt] [2] K.Kawase, Y.Ogawa, Y.Watanabe, \textit{Opt. Express 11, 2546(2003).} \\[0pt] [3] Z.Jiang, X.G.Xu, and X. -C. Zhang, \textit{Appl.Opt.39, 2982-2987(2000).} [Preview Abstract] |
Thursday, March 18, 2010 8:48AM - 9:00AM |
V29.00005: Metallic wire structures under an intense electromagnetic field Weiyi Zhang, S.T. Chui We discuss the limitation of metallic wire structures as absorbers of high intensity electromagnetic radiation due to the large local electrical fields developed at junctions and free ends of the wires. We find that at resonance the breakdown external electric field applied to the body of the wire structure is smaller by several orders of magnitude than the dielectric breakdown field induced at the ends of the wire. We consider the {\bf double} split ring structure and find that it can offer an enhancement of the ohmic power absorbed by an order of magnitude over that of single component systems. For multiply connected wire structures we find classes of resonant modes with zero local fields at the junctions but the fields at the free wire ends remain finite. [Preview Abstract] |
Thursday, March 18, 2010 9:00AM - 9:12AM |
V29.00006: ``Rectifying'' reflection from a magnetic photonic crystal Shiyang Liu, Wanli Lu, Zhifang Lin, S.T. Chui When an oscillating line source is placed in front of a special mirror consisting of an array of flat uniformly spaced ferrite rods, half of the image disappeared at some frequency. We believe that this comes from the coupling to photonic states of the magnetic surface plasmon band. These states exhibit giant circulations that only go in one direction due to time reversal symmetry breaking. Possible applications of this ``rectifying'' reflection include a robust one-way waveguide, a $90^{\circ}$ beam bender and a beam splitter, which are shown to work even in the deep subwavelength scale. [Preview Abstract] |
Thursday, March 18, 2010 9:12AM - 9:24AM |
V29.00007: Electron Population Investigation in Quantum Cascade Lasers using Femtosecond Mid-IR Pump-Probe Spectroscopy Sheng Liu, Elaine Lalanne, Robinson Kuis, Anthony Johnson Femtosecond mid-IR pulses have been coupled into a room temperature 4.8$\mu $m Quantum Cascade Laser (QCL) to investigate the carrier dynamics. In the pump-probe technique a strong pump beam is coupled into the QCL to deplete or excite electrons from upper or lower lasing subband. A weaker probe beam is used to monitor the evolution of the gain as a function of the delay between probe and pump -- this pump-probe signal is directly related to the electron population in the intersubband level. The 4.8$\mu $m mid-IR pulses were resonant with the QCL lasing transition, had a temporal width of 140 fs at a repetition rate of 250 kHz, synchronous to the pulsed bias. The pump-probe transmission experiment was done at different bias conditions. We observed a faster gain recovery time with increased bias, due to the dramatic reduction of upper state lifetime, because the phonon assisted non-radiative decay in a QCL far below threshold is much slower than the photon driven stimulated emission near or above threshold. At zero bias, we observed an increase in the probe signal as opposed to gain depletion by the pump pulse under high bias. Thus at zero bias, the pump excites electrons to the upper lasing level and the delayed probe experiences amplification instead of absorption. [Preview Abstract] |
Thursday, March 18, 2010 9:24AM - 9:36AM |
V29.00008: ABSTRACT WITHDRAWN |
Thursday, March 18, 2010 9:36AM - 9:48AM |
V29.00009: Highly sensitive PMOS photodetector with wide band responsivity assisted by nanoporous anodic aluminum oxide membrane Yung Ting Chen, Yang Fang Chen A new approach for developing highly sensitive PMOS photodetector based on the assistance of AAO membrane is proposed, fabricated, and characterized. It enables the photodetector with the tunability of not only the intensity but also the range of the response. Under a forward bias, the response of the PMOS photodetector with AAO membrane covers the visible as well as infrared spectrum; however, under a reverse bias, the near-infrared light around Si band edge dominates the photoresponse. Notably, the response at the optical communication wavelength of 850 nm can reach up to 0.24 A/W with an external quantum efficiency of 35{\%}. Moreover, the response shows a large enhancement factor of 10 times at 1050 nm under a reverse bias of 0.5 V comparing with the device without AAO membrane. The underlying mechanism for the novel properties of the newly designed device has been proposed. [Preview Abstract] |
Thursday, March 18, 2010 9:48AM - 10:00AM |
V29.00010: Tunable Localization and Oscillation of Optical Signals in Planar Graded Optical Waveguide Arrays Mingjie Zheng, Jun Jun Xiao, Kousuke Yakubo, Kin Wah Yu The optical Bloch oscillation has been studied theoretically in planar graded optical waveguide arrays with nearest-neighbor couplings. The gradient in the propagation constants can be achieved conveniently by the eletro-optic effects. We identified a variety of normal modes (called gradons) in the waveguide arrays with the aid of a phase diagram. Moreover, the localization properties of the normal modes are characterized and the transitions among these modes are obtained from the analysis of a picture of overlapping bands. The existence of the Bloch oscillation and other oscillations are confirmed by using the field evolution analysis with various initial Gaussian beams. From the results, we obtain a correspondence between gradon localization and Bloch oscillation. The results offer great potential applications in controlling wave propagation by means of graded materials and graded systems, which can be used to explore the tunability of light manipulation and applied to design suitable optical devices. [Preview Abstract] |
Thursday, March 18, 2010 10:00AM - 10:12AM |
V29.00011: Steering between Bloch oscillation and dipole oscillation in parabolically graded optical waveguide arrays Y.S. Chan, M.J. Zheng, K.W. Yu We study optical oscillations of supermodes in planar optical waveguide arrays with parabolically graded propagation constant in individual waveguide interacting through nearest neighbor couplings. The gradient in the propagation constants can be achieved conveniently by electro-optic effects. For these arrays, we have identified a symmetric dipole oscillation (DO) as well as a symmetry-breaking Bloch oscillation (BO) under appropriate conditions. Moreover, in analogy to a harmonic oscillator under gravity, we propose a lift and shift of the graded profile to cause a transition from DO to BO. The amount of lift and shift can be achieved by additional electro-optic effects. We confirm the optical transition by means of semiclassical theory, as well as the field evolution of the supermode modes. The results offer great potential applications in optical switching, which can be applied to design suitable optical devices. [Preview Abstract] |
Thursday, March 18, 2010 10:12AM - 10:24AM |
V29.00012: Broadband Electromagnetic Transparency by Graded Metamaterial Sphere L. Sun, K.W. Yu We have investigated the scattering of electromagnetic waves from a radially inhomogeneous metamaterial sphere whose dielectric permittivity is described by the graded Drude model $\epsilon_{s}(r)=1-\omega_p^2(r)/\omega^2$. The radial position dependent plasma frequency depends on $r$ as $\omega_p^2=1/2-c(r/r_{0})^n$, where $c$ and $n$ are positive constants and $r_{0}$ is the radius of the sphere. The electromagnetic field distribution has been calculated within the full-wave Mie scattering theory. When $n=2$, exact analytic solutions can be obtained in terms of confluent Heun function and confluent hypergeometric function of Kummer. This allows us to obtain the full-wave total scattering cross section analytically from the scattering field amplitudes. While the total scattering cross section $Q_{s}$ depends on both the graded plasma frequency profile and the frequency of the incident electromagnetic wave, it is found that $Q_{s}$ can achieve extremely small values over a broad frequency band and graded parameters. The analytic solutions allow us to assess the conditions for achieving broadband electromagnetic transparency in the metamaterial sphere and make tunable electromagnetic transparency feasible. [Preview Abstract] |
Thursday, March 18, 2010 10:24AM - 10:36AM |
V29.00013: Localization of electric fields in graded core-shell metamaterial structures Kin Wah Yu, En Bo Wei The electric-field distribution has been investigated in a cylindrical metamaterial structure under the illumination of a uniform incident optical field. The structure consists of a homogeneous dielectric core, a shell of metal-dielectric metamaterial with gradually varying Drude permittivity, embedded in a uniform matrix. In the quasistatic limit, the electric potentials and hence the electric fields have been derived exactly and analytically in terms of hypergeometric functions. Our results showed that the electric field distribution exhibits a prominent peak inside the shell, that can be confined to a desired position by varying the frequency of the optical field and the parameters of the permittivity profiles. Thus, by fabricating graded metamaterials, it is possible to control electric-field distribution spatially. We offer an intuitive explanation for the gradation-controlled electric-field distribution. [Preview Abstract] |
Thursday, March 18, 2010 10:36AM - 10:48AM |
V29.00014: Non-Euclidean cloaking effect for waves Huanyang Chen, Tomas Tyc, C.T. Chan, Ulf Leonhardt Non-Euclidean cloaking was recently proposed by combining non-Euclidean geometry and transformation optics. As the coordinate transformation is non-singular, cloaking may be broadband. Such a cloak has initially been designed for the regime of geometrical optics. Here we demonstrate that the cloaking device can even function in extreme wave optics when the working frequencies are quantized related to the spherical harmonics. Numerical simulations were performed to illustrate the cloaking effect. [Preview Abstract] |
Thursday, March 18, 2010 10:48AM - 11:00AM |
V29.00015: Temporal evolution of high-order transverse modes in a multi-mode VCSEL induced by a beam-profile optical feedback Chuan-Pi Hsu, Da-Long Cheng, Wang-Chuang Kuo, Tsu Chiang Yen This work studied the dynamics of the transverse modes in a multitransverse mode VCSEL when the later was conducted to lase the fundamental transverse mode by a Gaussian-beam-profile optical feedback. The multitransverse-mode beam profile of the solitary VCSEL was emitted into a single-mode fiber to achieve the Gaussian-beam-profile optical feedback. Afterward, a quasi-Gaussian beam fed back into the cavity of laser. The feedback beam irradiated on the facet of the fundamental mode of the laser chip, the photons were stimulated to lase and contribute to the fundamental transverse mode. Some high-order transverse modes were observed out of the above mentioned area. The interaction and evolution between the high-order modes and the fundamental mode of the VCSEL could be controlled by the spot of the feedback beam on the facet of laser. More experimental details will be presented and these results will help to expand the application of VCSELs. [Preview Abstract] |
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