Bulletin of the American Physical Society
2005 APS March Meeting
Monday–Friday, March 21–25, 2005; Los Angeles, CA
Session D16: Photonic Crystals and Nanoscale Physics |
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Sponsoring Units: DCMP Chair: Richard Warburton, Heriot-Watt University Room: LACC 404A |
Monday, March 21, 2005 2:30PM - 2:42PM |
D16.00001: Ultra-low threshold photonic crystal quantum dot laser Stefan Strauf, Kevin Hennessy, Matthew T. Rakher, Antonio Badolato, Pierre M. Petroff, Evelyn L. Hu, Dirk Bouwmeester Photonic crystal microcavities can provide small mode volumes on the order of one wavelength cubed. As a consequence, spontaneous emission coupling of the gain medium into spurious modes is highly suppressed and the threshold pump power for lasing activity can be very low [1]. We have fabricated 2D photonic crystal microcavities with embedded self-assembled InAs/GaAs quantum dots as active material. Single mode emission with quality factors up to 10000 has been found for various L3-type cavity geometries covering the wavelength region of 910-970 nm. Single mode lasing under optical excitation is characterized by line width narrowing and record low threshold pump powers down to 160 nW, corresponding to a high degree of spontaneous emission coupling efficiency. Together with active positioning schemes of the mode maximum with respect to the quantum dot location [2], this type of microcavity is highly attractive for reaching the regime of single quantum dot lasing. [1] G. Bjoerk, A. Karlsson, and Y. Yamamoto, Phys. Rev. A, \textbf{50}, 1675 (1994). [2] K. Hennessy et al., Photonics and Nanostructures -- Fundamentals and Applications 2 (2) 65-72 (2004). [Preview Abstract] |
Monday, March 21, 2005 2:42PM - 2:54PM |
D16.00002: Observation of Ultrahigh Spontaneous Emission Factors in GaAs(Ga,Al)As Microdisk Lasers W.H. Wang, X. Li, R. C. Myers, S. Ghosh, D. D. Awschalom, N. Samarth We study optically-pumped stimulated emission in small diameter ($D \approx 2 \mu m$) GaAs/(Ga,Al)As microdisk lasers that contain interface fluctuation quantum dots (IFQDs) in the active region. We observe single-mode laser operation over a wide range of pump power, and analyze the double logarithm input-output data with a standard rate equation. The analysis yields a spontaneous emission factor as high as $\beta \approx 0.82$, not seen in control experiments on microdisks with either larger diameters ($D \approx 4 \mu m$, $\beta \approx 0.45$) or without IFQDs ($D \approx 2 \mu m$, $\beta \approx 0.2$). This suggests that the ultrahigh values of $\beta$ result from the small cavity volume and high optical confinement in small diameter microdisks, as well as the combination of relatively narrow gain width and carrier localization in microdisks with IFQDs. Supported by DARPA-QUIST and NSF. [Preview Abstract] |
Monday, March 21, 2005 2:54PM - 3:06PM |
D16.00003: Controlled Coupling of Single InAs Quantum Dots to Photonic Crystal Cavity Modes Antonio Badolato, Kevin Hennessy, Evelyn Hu, Pierre Petroff, Mete Atature, Jan Dreiser, Atac Imamoglu We describe an experimental method that allows for the deterministic coupling of a single microcavity optical mode to an integrated single InAs/GaAs quantum dot (QD). Freestanding photonic crystal slabs were used as microcavities with embedded vertically stacked QDs. The QD stack formed a tracer for the seed layer whose emission was blue-shifted by annealing when partially capped. By means of high resolution active positioning and the ability to tune the mode through the entire quantum dot spectrum, this method provided strong Purcell factor enhancement of the QD luminescence in all fabricated samples. [Preview Abstract] |
Monday, March 21, 2005 3:06PM - 3:18PM |
D16.00004: Patterned porous silicon structures for microphotonics Daniel Gargas, Donald Sirbuly, Ovidiu Muresan, Steve Buratto Dry-removal soft lithography is used to fabricate microstructures in porous silicon films for use in microphotonics. In our experiments a heated porous silicon film is brought into contact with a patterned PDMS stamp. The stamp is then peeled from the film removing the porous Si from regions in contact with the film leaving behind a patterned structure. [1] The removed porous Si can be then be transferred from the PDMS stamp to other polymer films by this same contact and peel procedure to create patterned porous Si on polymer substrates. Details of our lithographic technique will be presented. We have also used this lithographic technique to create microscale and nanoscale patterned porous Si structures for a number of new applications including porous Si waveguides, amplified stimulated emission in waveguides, patterned Bragg mirrors and chemical sensors based on reflectivity and luminescence. Details of these applications will also be discussed. [1] Sirbuly D.J.; Lowman G.M.; Scott B.; Stucky G.D.; and Buratto S.K.: Adv. Mater. 15, 149 (2003). [Preview Abstract] |
Monday, March 21, 2005 3:18PM - 3:30PM |
D16.00005: Arrays of aligned carbon nanotubes act as nano-antennae to receive and transmit light Z.F. Ren, Y. Wang, K. Kempa, T. Kempa, J. Rybczynski, A. Herczynski, B. Kimball, J.B. Carlson, G. Benham, W.Z. Li We present optical measurements of random arrays of aligned carbon nanotubes, and show that the response is consistent with conventional radio antenna theory. We first demonstrate the \textit{polarization effect}, the suppression of the reflected signal when the electric field of the incoming radiation is polarized perpendicular to the nanotube axis. Next, we observe the interference colors of the reflected light from an array, and show that they result from the \textit{length matching }antenna effect. This antenna effect could be used in a variety of optoelectronic devices, including THz and IR detectors, solar cells, optical switches and computers, etc. [Preview Abstract] |
Monday, March 21, 2005 3:30PM - 3:42PM |
D16.00006: Template-directed growth of nanoparticle-mediated colloidal crystals on large-area patterned substrates generated by multibeam holography Ryan Kershner, Summer Rhodes, Florencio Garcia-Santamaria, Paul Braun, Jennifer Lewis, Pierre Wiltzius Large-domain colloidal crystals were created by gravitational settling of microspheres onto patterned substrates. The large-area patterned substrates were produced using multibeam interference lithography, facilitating templated epitaxial growth of single domain crystals with controlled crystallographic orientation. A 2-beam UV laser setup was employed to produce 1-D features with a periodicity on the order of 500 nm ($\sim$ colloid diameter). This was extended to a square array of 2-D features through multiple exposures. Atomic force microscopy (AFM) was used to characterize the resulting surface structures. The exposure parameters were varied to control the depth and width of the features in an attempt to optimize the pattern for defect free colloidal epitaxy. Colloidal crystals were produced from a binary suspension of colloidal microspheres stabilized through the addition of highly charged nanoparticles (Tohver et al., PNAS (2001)) followed by subsequent nanoparticle gelation (Lee et al., Langmuir (2004) to yield robust structures that can withstand capillary forces during drying. [Preview Abstract] |
Monday, March 21, 2005 3:42PM - 3:54PM |
D16.00007: Dynamic spatial ordering of nanostructures Ramki Kalyanaraman, Wei Zhang, Chi Zhang e We present results showing that the application of a rapid spatio-temporal surface modulation $\textit{in-situ}$ with film deposition directs the assembly of ordered structures. Co clusters of approximately 50 nm or 200 nm in size were assembled into one-dimensionally ordered arrays spaced 400 nm apart on Si (100) substrates during film growth of a 0.5 nm and 23 nm thick film, respectively. This ordered arrangement was achieved under e-beam evaporation of Co with simultaneous two-beam laser interference irradiation of the substrate. The ordering length scale was consistent with the theoretical two-beam fringe spacing. For the thicker Co film, the particles are irregularly shaped indicating a rapidly solidified liquid-like structure. The areal concentration of Co in the irradiated films is comparable to that in the unirradiated samples, suggesting that reevaporation is minimal. From this evidence, the mechanism for ordering is attributed mainly to material accumulation by spatially periodic laser interference heating of the growing cobalt film. Also, ordering is more readily observed for the dynamic experiments, as compared to irradiation after film deposition. This implies that laser-scattering from growing Co clusters is very important towards the observed ordering. This dynamic $\textit{in-situ}$ process is an economical and simple approach to assemble ordered nanostructured films. [Preview Abstract] |
Monday, March 21, 2005 3:54PM - 4:06PM |
D16.00008: Light propagation in random colloidal films with varying coordination number Xiaotao Peng, Anthony Dinsmore We measure the propagation of light through a random film of strongly-scattering microspheres as a function of the number of contacts per particle (the coordination number, Z). Decreasing Z reduces the average refractive index, and enhances the optical contrast of each scattering sphere with the effective background. In our experiments, we mix two kinds of colloidal spheres and prepare a dried film with random structure. We then dissolve spheres of one kind to vary Z for the other kind. Polystyrene and poly(methylmethacrylate) spheres are used, as well as latex spheres coated with a high-index ZnS or SnS layer to enhance scattering. The transport mean-free path is then extracted from the angular distribution of backscattered light. The results may guide our understanding of the propagation of waves in random media in general and may lead to new photonic materials. This work is supported by the NSF-sponsored UMass MRSEC. A.D.D. is a Cottrell Scholar of the Research Corporation. [Preview Abstract] |
Monday, March 21, 2005 4:06PM - 4:18PM |
D16.00009: Resonant excitation of off channel localized impurity modes by the modes of a photonic crystal waveguide Arthur McGurn A theoretical treatment is presented of the electromagnetic transmission properties of a photonic crystal waveguide that interacts with off channel dielectric impurities, impurity clusters, neighboring waveguides, or neighboring waveguide networks. The photonic crystal studied is a two-dimensional square lattice array of parallel axis dielectric cylinders (formed of linear dielectric medium) in vacuum, and impurities and waveguides are created by cylinder replacement. The waveguide whose transmission is calculated is formed from linear dielectric media, but the off channel features that it interacts with may be formed from either linear or Kerr nonlinear dielectric media. The off channel features may also be composed of dissipative or amplifying media. Waveguide transmission resonances, associated with resonant scattering from electromagnetic modes on the off channel features, are found. Modes present on off channel features formed from linear dielectric media include both propagating and localized modes. Modes present on off channel features formed from Kerr nonlinear dielectric media include simple localized and intrinsic localized (soliton like) modes. [Preview Abstract] |
Monday, March 21, 2005 4:18PM - 4:30PM |
D16.00010: Delocalization of Light in Random Multilayer Dielectric Media Alex Small, David Pine Doping random multilayer dielectric media with weak scatterers can cause delocalization of classical waves in cases not considered by previous investigators. Our system consists of parallel slabs of thickness d and refractive index n1, randomly spaced along the z axis and surrounded by a medium of refractive index n2. This system is frequently used to study 1D localization of classical waves. The slabs exhibit Fabry-Perot resonances at frequencies that are integer multiples of {\$}$\backslash $pi c/n1 d{\$}. We consider the effect of doping this system with small dielectric particles at a low volume fraction. Using scaling arguments we show that above the critical frequency waves undergo a transition from localized evanescent decay to delocalized power law decay. The transition occurs for arbitrarily weak scatterers and low scatterer concentrations, in stark contrast to previous predictions. A rate equation analysis predicts that the wave intensity scales as z\^{}(-3/2). Simulation data will be presented and compared with scaling theory predictions. We also discuss analogies between the delocalization transition and second order phase transitions. The mean angle at which photons exit the sample is analogous to an order parameter. Finally, making analogies to mean field theory, we show that waves can undergo successive delocalization and relocalization transitions. [Preview Abstract] |
Monday, March 21, 2005 4:30PM - 4:42PM |
D16.00011: Local density of states analysis of surface wave modes on truncated photonic crystal surfaces with nonlinear material Merle Elson, Klaus Halterman The local density of states and response to an incident plane wave of a finite sized photonic crystal (PC) with nonlinear material (NLM) is analyzed. Of particular interest is the excitation of surface wave modes at the truncated surface of the PC, which is collocated with the NLM material. We compute the 2D Green function of the PC with linear material and then include the Kerr NLM in a self-consistent manner. The 2D PC consists of a square array of circular rods where one row of the rods is semi- circular in order to move the surface wave defect mode frequency into the band gap. Since the surface modes are resonant at the interface, the NLM should experience at least an order of magnitude increase in field intensity. This is a possible means of increasing the efficiency of the PC as a frequency conversion device. [Preview Abstract] |
Monday, March 21, 2005 4:42PM - 4:54PM |
D16.00012: Surface Plasmon Assisted Electro-Optical Switching of Molecular Thin Films in Metal-Insulator-Metal Devices Ragip Pala, Ken Shimizu, Nicholas Melosh, Mark Brongersma Molecular electro-optical switches are one of the major milestones in the development of optoelectronic memory elements as well as the long-standing goal of highly integrated photonic circuits. We intend to exploit the unique optical properties of photochromic compounds such as spiropyrans to realize these structures. We have constructed a set-up with which the wavelength dependent refractive index and absorption of a wide variety of molecules in a polymer film can be determined. Substantial changes in the refractive index and absorption have been observed for photochromic molecules sandwiched between two metal layers under the influence of an externally applied electric field. These changes can be exploited in optical and plasmonic switches. Preliminary results of such devices will be presented. [Preview Abstract] |
Monday, March 21, 2005 4:54PM - 5:06PM |
D16.00013: Infrared Photonic Crystals on the Base of Chalcogenide Glass Inverse Opal. Ali Aliev, Anvar Zakhidov, Ray Baughman, Eli Yablonovitch Large surface area infrared photonic crystals with reflectance more than 90{\%} were successfully synthesized by self-assembling large size monodispersed SiO$_{2}$ spheres, 0.8 $\mu $m - 4.5 $\mu $m with following melt infiltration with chalcogenide glass Ge$_{33}$As$_{12}$Se$_{55}$ and extraction SiO$_{2}$ spheres by chemical etching in 1{\%}HF. The sphere size or the periodicity of the templates are chosen to guarantee the photonic gaps of inverted opals in the region of IR atmospheric transparent windows, 3 - 5 $\mu $m and 8 -12 $\mu $m. Reflection spectra measured at each step of the fabrication process are in excellent agreement with the modified form of Bragg's law, which takes into account the reduced angle with respect to the normal at which light travels in the opal (i.e. taking into account Snell's law). Fabrication, structural features and the spectral behavior of reflectance peaks of obtained chalcogenide glass inverse opals are presented. [Preview Abstract] |
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