Showing papers on "Photonic crystal published in 1993"

Photonic band-gap structures

Abstract: The analogy between electromagnetic wave propagation in multidimensionally periodic structures and electron-wave propagation in real crystals has proven to be a fruitful one. Initial efforts were motivated by the prospect of a photonic band gap. a frequency band in three-dimensional dielectric structures in which electromagnetic waves are forbidden irrespective of the propagation direction in space. Today many new ideas and applications are being pursued in two and three dimensions and in metallic, dielectric, and acoustic structures. We review the early motivations for this research, which were derived from the need for a photonic band gap in quantum optics. This need led to a series of experimental and theoretical searches for the elusive photonic band-gap structures, those three-dimensionally periodic dielectric structures that are to photon waves as semiconductor crystals are to electron waves. We describe how the photonic semiconductor can be doped, producing tiny electromagnetic cavities. Finally, we summarize some of the anticipated implications of photonic band structure for quantum electronics and for other areas of physics and electrical engineering.

Photonic band gaps and localization

Abstract: Localization, Diffusion, and Correlation: The Localization of Light S. John. The Speed of Diffusing Light B.A. van Tiggelen, A. Lagendijk. Diffusion of Classical Waves in Random Media C.M. Soukoulis, et al. Accurate Measurement of Backscattered Light from Random Media P.N. den Outer, et al. Photonic Band Gaps: Photonic Band Structure E. Yablonovitch. Photonic Gaps for Electromagnetic Waves in Periodic Dielectric Structures K.M. Ho, et al. Plane-Wave Calculation of Photonic Band Structure K.M. Leung. Measurements of Localization and Photonic Band Gap Systems in Two Dimensions S. Schultz, D.R. Smith. Wave Propagation in Random Media: Localization Transition in Anisotropic and Inhomogenous Systems P. Sheng, Z.Q. Zhang. Statistical Inversion of Stratified Media from Acoustic Pulses Scattered at Two Angles of Incidence B. White, et al. 30 additional articles. Index.

Radiation properties of a planar antenna on a photonic-crystal substrate

Abstract: The photonic crystal is investigated as a substrate material for planar antennas in the microwave and millimeter-wave bands. Experimental results are presented for a bow-tie antenna on a (111)-oriented face-centered-cubic photonic-crystal substrate with a band gap between approximately 13 and 16 GHz. When driven at 13.2 GHz, the antenna radiates predominantly into the air rather than into the substrate. This suggests that highly efficient planar antennas can be made on photonic-crystal regions fabricated in semiconductor substrates such as GaAs.

Photonic band-gap crystals

Abstract: The analogy between electromagnetic wave propagation in multidimensionally periodic structures and electron wave propagation in real crystals has proven to be a very fruitful one Initial efforts were motivated by the prospect of a photonic band gap, a frequency band in three-dimensional dielectric structures in which electromagnetic waves are forbidden, irrespective of propagation direction in space Today many new ideas and applications are being pursued in two and three dimensions, and in metallic, dielectric and acoustic structures, etc The author reviews the early motivations for this work, which were derived from the need for a photonic band gap in quantum optics This led to a series of experimental and theoretical searches for the elusive photonic band-gap structures, those three-dimensionally periodic dielectric structures which are to photon waves what semiconductor crystals are to electron waves Then he describes how the photonic semiconductor can be 'doped', producing tiny electromagnetic cavities Finally he summarizes some of the anticipated implications of photonic band structure for quantum electronics and the prospects for the creation of photonic crystals in the optical domain

Nature of the photonic band gap: some insights from a field analysis

Abstract: To clarify the nature of photonic band gaps, a series of calculations on two-dimensional photonic crystals is undertaken. Systems that possess a large gap for one polarization and no gap for the other polarization are analyzed. Two features of a photonic crystal that give rise to a large photonic band gap for each polarization, i.e., connectivity and concentration of the dielectric material, are elucidated. The implications for making materials with large photonic band gaps in two and three dimensions are discussed.

Observation of surface photons on periodic dielectric arrays.

Abstract: The first observation to the authors’ knowledge of electromagnetic surface waves in a two-dimensional dielectric crystal is reported. By using the coherent microwave transient spectroscopy technique, surface waves are shown to exist at frequencies within the photonic band gap for certain lattice terminations. Energy at gigahertz frequencies is coupled into the surface mode using a prism coupling technique. The experimental results are in excellent agreement with theoretical predictions.

Surface effects and band measurements in photonic crystals.

Abstract: An analytic study of Bloch waves near photonic crystal surfaces has been carried out. This is a generalization of Heine's theory of metal/semiconductor interfaces. The main concern of this study is how the surfaces of a finite system affect band determination--which usually involves transmission measurements on small photonic crystals. An analytic expression for transmission is obtained. The results show that the usual band measurements could lead to considerable errors, especially when they involve narrow band gaps. A possible method to improve band measurements has been suggested. The analytic surface analysis has been demonstrated to be fairly accurate, even for a small system. The theory is expected to be applicable to other surface-related problems of photonic systems.

Nonlinear optical solitary waves in a photonic band gap

Abstract: It is suggested that solitary wave solutions exist in the gap region of photonic band gap materials with a Kerr nonlinearity. Using a variational trial function we estimate the amplitude, size scale, and the nature of phase modulation of these nonlinear waves. In two dimensions, we predict the occurrence of a variety of finite energy solitary waves associated with the different symmetry points of the crystalline Brillouin zone. Solutions which preserve the symmetry of the crystal exist for both positive and negative Kerr coefficient whereas solutions which break the symmetry occur only for positive nonlinearity. These states are relevant to the bistable switching properties of photonic band gap materials.

Periodic dielectric structure for production of photonic band gap and method for fabricating the same

Abstract: A method for fabricating a periodic dielectric structure which exhibits a photonic band gap. Alignment holes are formed in a wafer of dielectric material having a given crystal orientation. A planar layer of elongate rods is then formed in a section of the wafer. The formation of the rods includes the step of selectively removing the dielectric material of the wafer between the rods. The formation of alignment holes and layers of elongate rods and wafers is then repeated to form a plurality of patterned wafers. A stack of patterned wafers is then formed by rotating each successive wafer with respect to the next-previous wafer, and then placing the successive wafer on the stack. This stacking results in a stack of patterned wafers having a four-layer periodicity exhibiting a photonic band gap.

Periodic dielectric structure for production of photonic band gap and devices incorporating the same.

Abstract: A method for fabricating a periodic dielectric structure which exhibits a photonic band gap. Alignment holes are formed in a wafer of dielectric material having a given crystal orientation. A planar layer of elongate rods is then formed in a section of the wafer. The formation of the rods includes the step of selectively removing the dielectric material of the wafer between the rods. The formation of alignment holes and layers of elongate rods and wafers is then repeated to form a plurality of patterned wafers. A stack of patterned wafers is then formed by rotating each successive wafer with respect to the next-previous wafer, and then placing the successive wafer on the stack. This stacking results in a stack of patterned wafers having a four-layer periodicity exhibiting a photonic band gap.

Impurity Modes in One Dimensional Periodic Systems: The Transition from Photonic Band Gaps to Microcavities

Abstract: Within the context of this volume on confined photons and electrons, the notions of photonic band gap structures, light localisation and microcavities are widely used. It was pointed out some time ago that there is a connection between a cavity constructed from dimensional Bragg reflectors with a π/2 phase slip and a photonic band gap structure with an impurity. However, the connection between Fabry-Perot microcavities and deep centre impurities has not been explicitly made. In this context it is a useful tutorial to consider the transition from one dimensional photonic band gaps to microcavities1.

Photonic band structures of optically anisotropic periodic arrays.

Abstract: We use a plane-wave expansion to calculate the photonic band structures of anisotropic dielectric composites. The composites consist of a periodic array of anisotropic dielectric spheres embedded in air. Calculations are carried out for spheres that are optically uniaxial or biaxial, Faraday active, or naturally optically active. Anisotropy in the sphere dielectric function is found to split degenerate bands and to narrow or even close band gaps, analogous to Stark or Zeeman splitting in conventional band structures. At long wavelengths, the lowest bands are well described by effective indices of refraction, which are in fairly good agreement with an anisotropic Maxwell-Garnett approximation.

Mirror with photonic band structure

Abstract: An apparatus for achieving in-phase mode operation of a diode laser. A photonic band gap mirror (photonic crystal) having a periodic lattice structure is placed in front of light emitted from one side of the laser diode array. Because of an incomplete photonic band gap in the photonic crystal, light normal to the crystal will be primarily reflected while light at an angle will be primarily transmitted through the mirror. Since in-phase emission is primarily normal and out-of-phase emission primarily off axis, the reflected light which is directed back into the laser cavity will be the predominant lasing mode. The out-of-phase mode primarily transmitted will have significantly larger losses. The resulting laser diode apparatus will therefore operate in-phase and produce a single lobe far-field distribution.

Photonic Band Structure

Abstract: We employ the concepts of band theory to describe the behavior of electromagnetic waves in three dimensionally periodic face-centered-cubic (fcc) dielectric structures. This can produce a “photonic band gap” in which optical modes, spontaneous emission, and zero point fluctuations are all absent. In the course of a broad experimental survey, we have found that most fcc dielectric structures have “semi-metallic” band structure. Nevertheless, we have identified one particular dielectric “crystal” which actually has a “photonic band gap”. This dielectric structure, consisting of 86% empty space, requires a refractive index contrast greater than 3 to 1, which happens to be readily obtainable in semiconductor materials.

Photonic Band Structures of Two-Dimensional Dielectric Media

Abstract: When a quantum or a classical wave propagates in a periodic structure in any number of spatial dimensions, the dispersion curves that relate the frequencies of the wave to the wave vector characterizing its propagation possess an infinite number of branches. These branches form bands that are separated by frequency gaps at points of symmetry in the corresponding Brillouin zones. In some cases an absolute gap occurs, viz. a frequency range in which no waves can propagate that exists for all values of the wave vector in the Brillouin zone, and gives rise to a gap in the density of states of the waves propagating through these structures.

Quantum electrodynamics in photonic band gaps: atomic-beam interaction with a defect mode

Abstract: A structural defect in a two-dimensionally periodic dielectric structure may form a local field mode within a photonic band gap in which no other E-polarized field modes exist. We show that such a defect mode can give rise to new quantum-electrodynamic effects in resonant field–atom interaction, owing to the spatially modulated standing-wave character of its field. Atomic-beam motion is considered (a) along an interplanar defect and (b) through a spherical defect. The resonant interaction of a moving two-level atom with the quantized field of these defects can yield hitherto unknown features—oscillatory patterns of the atomic population inversion, fluorescence spectra, and nonclassical field states—that are essentially different from their counterparts in the standard Jaynes–Cummings model, which holds for atomic-beam motion in a spatially uniform single-mode field.

Tunneling of electromagnetic waves in two-dimensional photonic crystals

Abstract: The tunneling of electromagnetic waves in the band-gap region of periodic dielectric arrays is investigated with the coherent microwave transient spectroscopy technique. Transmission probabilities at frequencies in the fundamental band gap are measured and found to depend exponentially on sample thickness. From these results the frequency dependence of the imaginary wave vector is determined. The peak imaginary wave vector, which occurs at midgap, is observed to be proportional to the width of the band gap, unlike the case for single-barrier tunneling of electrons, where the relationship is expected to vary as the square root of the barrier height.

Plane-Wave Calculation of Photonic Band Structure

Abstract: The new class of artificial periodic dielectric media called the photonic crystals, originally proposed by Yablonovitch[1] and John[2] a few years ago, has been attracting a great deal of research interests because of its highly unusual properties which offer exciting and challenging new problems, and because of its broad potentials for device applications from the mm to the uv wavelengths. Recently photonic crystals which have a full photonic bandgap have been discovered.[3] [4] Surface states as well as defect modes[5] in these crystals have now also been studied.

k.p theory of photonic band structures in periodic dielectrics

Abstract: A kp band-structure formalism is presented to describe photonic dispersion relations in periodic dielectric structures, within the scalar wave approximation A reciprocal effective dielectric tensor is defined and an expression analogous to the f-sum rule for semiconductors is derived Application of the present formalism is discussed using a two-band model The generalization to vector waves is outlined

An optimum design of a a-Sipoly-Si tandem solar cell

Abstract: A systematic investigation of a high efficiency a-Sipoly-Si four-terminal structure tandem solar cell has been made using both theoretical and experimental approaches. It has been shown from optimum design theory, used on a realistically attainable best efficiency, that the best combination of a tandem solar cell is a-Si/poly-Si silicon materials with respect to high achievable efficiency. In the optical design rule, priority of the photon utilization is put on the poly-Si bottom cell. Employing high conductivity with wide optical band gap p type /spl mu/c-SiC as a window material and n type /spl mu/c-Si as back ohmic contact with BSF treatment, a conversion efficiency of 17.2% has been obtained for the poly-Si cell. An optimum design of the a-Si top cell has been experimentally made on a p /spl mu/c-SiC/p a-SiC/i a-Si/n /spl mu/c-Si/ITO structure, and an efficiency of 7.25% has been obtained with a 100 nm thick i-layer top cell. The best efficiency of a p-i-n single-junction solar cell with this structure is 12.3% so far with a 500 nm i-layer thickness device using an Ag back electrode. With a 100 nm thick ultra thin top cell, a total conversion efficiency of an a-Sipoly-Si four-terminal tandem solar cell as high as 21.0% has been achieved. >

Molecular and Free Electron Spontaneous Emission in Periodic Three Dimensional Dielectric Structures

Abstract: Since the prediction by Purcell in 1946 that the spontaneous emission rate of an atom could be enhanced by placing it in a resonantly tuned high-Q cavity, a great deal of theoretical and experimental work has been performed in this area.(1) In particular, Klepner was able to extend Purcell’s observation to both predict and observe the inhibition of spontaneous emission.(2, 3) This effect relies on the opposite extreme of placing the excited atom in a structure which has no modes available at the atomic radiation frequency. The inhibition of spontaneous emission was elegantly demonstrated using high Rydberg state transitions and parallel plate structures in a molecular beam experiment. The use of high Rydberg state transitions was necessitated by the requirement of a long wavelength emission where a structure could be fabricated. The molecular beam was required because the transition energies involved are of the order of 10-2eV and the excited states would be quickly collisionally quenched in an environment with enough atoms to directly obtain a fluorescence signal.

Photonic band gap resonators for high energy accelerators

Abstract: We have proposed that a new type of microwave resonator, based on photonic band gap (PBG) structures, may be particularly useful for high energy accelerators. We provide an explanation of the PBG concept and present data which illustrate some of the special properties associated with such structures. Further evaluation of the utility of PBG resonators requires laboratory testing of model structures at cryogenic temperatures, and at high fields. We provide a brief discussion of our test program, which is currently in progress. >

Semiconductor photonic integrated circuits with directly formed waveguides using in-plane bandgap energy control by selective MOVPE

Abstract: Photonic integrated circuits (PICs), which are attractive for advanced optical-fiber communication systems, consist of various photonic components containing waveguide structures with different bandgap energy (Eg). To fabricate PICs, complicated processes including selective etching of multi-layers and the following growth of various layers have been required. The selective metalorganic vapor phase epitaxy (MOVPE) technique enables directly formed MQW waveguides with in-plane Eg control. Simple fabrication processes without semiconductor etching are desirable for high device uniformity and yield. Using this novel technique, various photonic devices have been successfully demonstrated. >

Properties And Radiation Hardness Of PbWO/sub 4/ Crystals

Abstract: Melt. Hardn. Xo. RM. Hygrosc. pointOC ( M ~ ~ ~ ) cm cm Amongst new heavy scintillating crystals which satisfy the requirements of electromagnetic calorimetry in the extreme conditions of rate and radiation foreseen in the future projects as LHC, SSC, UNK single crystals based on lead and tungsten compounds have been already considered as a possible choice [l]. Recently it has been shown that PbWO4 single crystals [2-61 possess such properties. The perspective of wide application of PbWO4 scintillator for detectors has stimulated further investigations of these crystals to control the factors which determine its scintillation properties. Beam test have been performed at MEP (Protvino) and at CERN.

Finite-element analysis of thermal distortion of directly water-cooled silicon crystal monochromator

Abstract: The directly water-cooled silicon crystal used on the multipole wiggler beam line BL16 at the Photon Factory has extended cooling fins below the crystal block. Such extended fins are useful to reduce bowing of the crystal due to thermal distortion induced by synchrotron radiation. Experimental and calculated Si(111) and Si(333) double crystal rocking curves are compared in the present paper. Thermal deformation is calculated using a finite element analysis program ANSYS. Fairly good agreement was obtained between experiment and calculation.© (1993) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Measurements of Localization and Photonic Band Gap Systems in Two-Dimensions

Abstract: We report the results of experimental investigations of two dimensional periodic and random scattering systems. The systems consist of arrays of dielectric cylindrical scatterers bounded on top and bottom by conducting sheets. We present the results of measurements made on defect modes created by removing part or all of a scatterer from an otherwise perfect lattice. We also present a series of measurements made on localized modes created by randomly removing an increasing number of scatterers. Discussion of applications for photonic band gap structures is included.

Periodic Dielectric Structures: The Long Wavelength Effective Dielectric Constant

Abstract: The study of the electromagnetic properties of heterogeneous media is an old but still very active subject. Initially, various effective medium approaches [1] like the Maxwell-Garnet approximation were used to determine the dielectric constant and other properties in the long wavelength limit. It was later realized that these were inadequate and the microgeometry of the medium needs to be taken into account even though it is on a much smaller scale than the probing wavelength. Several such studies were made by McPhedran and McKenzie [2] and others for periodic systems using the boundary-matching approach. The efficacy of this approach is limited to special shapes like spheres and cubes which do not overlap. In recent years, several [3–5] groups have used Fourier expansion techniques which can be used to study any periodic microgeometry and are much wider in scope than the previous efforts. We have also used a Fourier expansion technique to study this problem and our method will be applied to find the effective dielectric constant of several classes of “photonic band gap” (PBG) materials. The PBG materials are basically periodic arrangements of one type of material embedded in another. It is interesting to note that besides the possibility of possessing photonic gaps, some of these materials are also anisotropic and thus will exhibit birefringence.

Comparative Optical Techniques for Monitoring Metals in Single-Crystal Silicon

Abstract: To detect the presence of heavy, transition metals in the process tine one must monitor the degradation of minority carrier lifetime and the increase of total metallic concentration in the bulk. These needs an not be met by some of the more familiar surfacebased analytical tools. Thus, lab-based techniques are finding applications within the IC manufacturing arena. Surface Photovoltage (SPV) and the Electrolytic Metal Tracer (ELYMAT) are both optical techniques designed to measure minority carrier dffision length (Ld). Although they have different set-ups, modes of operation, and detection schemes, the imaging signals depend on carrier dynamics. Both of these methods meet the diagnostic requirements, and are noncontact. Here in is a discussion of the need for such tests, their comparative differences, and some applications.

An optically controlled microwave attenuator

Abstract: A hybrid optoelectronic scheme, suitable for controlling microwave integrated circuits, has been demonstrated. By employing optoelectronic techniques, we have demonstrated up to 26 dB of rf attenuation using a linear one-dimensional (1 -D) AlGaAs laser diode array and a silicon photoconductive switch. Calculations indicate that this attenuation scheme can provide up to 40 dB of broad-bandwidth isolation, once optimized. The optically controlled attenuator scheme is as follows. A planar microwave transmission line is fabricated on either a silicon (Si) or gallium-arsenide (GaAs) substrate. Silicon and GaAs are both excellent photoconducting materials; therefore, fabrication of highspeed transmission lines on these materials yields imbedded photoconductive switches (PCSs) resident in the high-speed lines. Illumination of these switches by the appropriate light source creates a conductive plasma in the switch gap, and since this switch is between the transmission lines conductors, the plasma changes the transmission line's characteristic impedance. Thus the creation of a plasma within the transmission line causes the propagating wave to be attenuated, with the degree of attenuation being a function of the induced plasma density. For example, calculations indicate that this attenuation scheme yields 30 dB of rf attenuation for a shunt rf impedance of 1 a. In addition, the attenuation value is roughly an exponential function of the shunt rf impedance (i.e., the induced plasma density), which can be accurately controlled by varying the incident laser pulse intensity. The planar transmission line geometry that was chosen was coplanar waveguide, since broad-area laser diodes can be easily focused onto the gaps between the transmission line's conductors. Both Si and GaAs were used as the substrate material. GaAs has a photo-carrier lifetime of fi: 5 ns. Si was used for applications where a long attenuation time is desired, since the photo-carrier lifetime in Si is on the order of microseconds. 50-R coplanar waveguidephotoconductive switches (CPW-PCSs) were fabricated with multiple gap spacings between the coplanar conductors of 10, 20, 30 and 50pm. The switch resistance is proportional to the square of the gap length, which permits the switch resistance to be characterized as a function of laser ~