T.F. Krauss

Optical and confinement properties of two-dimensional photonic crystals

We describe experiments on a quasi-two dimensional (2-D) optical system consisting of a triangular array of air cylinders etched through a laser-like Ga(Al)As waveguiding heterostructure. Such a configuration is shown to yield results very well approximated by the infinite 2-D photonic crystal (PC). We first present a set of measurements of the optical properties (transmission, reflection, and diffraction) of slabs of these photonic crystals, including the case of in-plane Fabry-Perot cavities formed between two such crystals. The measurement method makes use of the guided photoluminescence of embedded quantum wells or InAs quantum dots to generate an internal probe beam. Out-of-plant, scattering losses are evaluated by various means. In a second part, in-plane micrometer-sized photonic boxes bounded by circular trenches or by two-dimensional photonic crystal are probed by exciting spontaneous emission inside them. The high quality factors observed in such photon boxes demonstrate the excellent photon confinement attainable in these systems and allow to access the detail of the modal structure. Last, some perspectives for applications are offered.

Improved 60/spl deg/ bend transmission of submicron-width waveguides defined in two-dimensional photonic crystals

We compare quantitatively the transmission properties of various 60/spl deg/ bends carved into a photonic crystal based on a two-dimensional triangular lattice of holes perforating a GaAs-based heterostructure. The bends are inserted into channel waveguides defined by three missing rows in the photonic crystal. Their design is inspired by some ideas from classical integrated optics. We show experimentally that in some cases the transmission of the bent waveguide is fairly high, up to 70%, within a bandwidth of 3%, e.g., 30 nm at 1 /spl mu/m, sufficient to contemplate wavelength-division-multiplexing applications. The observed performance opens the opportunity to implement a variety of optical functions in view of future photonic crystal integrated circuits for which low-loss bends constitute an essential building block.

Ultrafast all-optical switching in AlGaAs photonic crystal waveguide interferometers

We have demonstrated ultrafast switching with photonic crystals integrated into Mach-Zehnder interferometers. The nonlinearity is induced by excitation of carriers into one arm of the interferometer, and switching times as short as 3ps are achieved.

All-photonic-crystal coupled cavity and guide

Summary form only given. In the contribution, we show clear evidence that photonic crystals (PC) can be used in ultrasmall integrated optics to cascade two elements, in this case a cavity and a waveguide. We use as a basis PC a triangular array of holes of period a=220-260 nm etched through an AlGaAs planar waveguide, in which we define a hexagonal cavity of side h=7a (H7 cavity), and a guide with width ranging from a to 4a and a length of 36a. Variable coupling is achieved by bringing both elements within N=2 to 5 PC rows of each other. By using the localized photoluminescence of InAs self-assembled quantum dot layers embedded in the GaAs planar waveguide core, we are able to excite either the guide entrance (El) or the cavity H7 (E2). We collect, in a localized fashion, either light emerging from the PC guide at the nearby cleaved edge (C1/sup 2/) or light scattered out-of-plane by the cavity boundaries (C2/sup 3/).

Ultra-thin, laterally injected light-emitting diodes-the role of photonic crystals for light extraction

Summary form only given. In planar microcavity light-emitting diodes (MCLEDs), light not extracted is lost to leaky modes and also, up to 40% or more, to unavoidable laterally propagating guided modes. Photonic crystals (PCs) located around the emitting area within a distance smaller than the absorption length may act as efficient scatterers that extract guided light outside the heterostructure plane. To maximize extraction efficiency through this mechanism it is interesting to start from a microcavity based on insulating oxidised AlAs mirrors (Alox DBRs) rather than classical AlAs-GaAs DBRs mainly because they reduce leaky modes to the benefit of guided modes.

Flatband Slow Light in Photonic Crystal Waveguides

A photonic crystal waveguide that features slow light without noticeable dispersion is demonstrated using a higher order even mode in a W2 waveguide on a SOI platform.

Integration of a 2-D photonic crystal superprism with 1-D photonic crystal microcavity filters for high channel selectivity

A 2-D photonic crystal superprism-filter device for demultiplexing applications has been designed using plane wave expansion and 2-D finite difference time domain methods. High channel selectivity with peak transmission linewidths of 15 nm is achievable.

The PICCO project: a survey

This presentation will provide a limited overview of work carried out in the multi-partner PICCO (photonic integrated circuits by crystal optics) project. In particular, the III-V material system used in PICCO is the AlGaAs/GaAs material system. In the PICCO project, the approach used for lithographic pattern definition has been, so far, primarily the conventional one, i.e. direct-write electron-beam lithography. But, at the outset, our recognition of the need for a genuinely mass-production approach has led to work on excimer-laser based photolithography, with high-precision masks giving a replicative approach.

Soliton effects in an AlGaAs Bragg grating

Experimental and theoretical research exploring the nonlinear properties of periodic structures has intensified over the past decade within a diverse range of materials utilizing both second and third order effects. Recently we studied the nonlinear transmission characteristics of high intensity pulses propagating through 4-10 mm long gratings etched into ridge waveguides formed in AlGaAs.

Analysis of Mictrostructured Edge-Emitting Semiconductor Lasers for Short-Pulse Generation

The collisional lasers s e attractive owkg to the possibility of obtaining high energy T d lasing power on excltation of large volumes of compressed gases The iopumping that IS well-horn since the &die 60-!er, the electron-beam pumping mainly, may be intended just for these conditions At the m e time, lhe efficienl (>I% efficiency) shod-wavclmgth (X < I w, the excirner systems are not considered) collisional laxrs vmh toniring excitation appeared only after 1985 substantially by the &om of OUE group, and the dciency ofnear IR lerers due tod-p vansitions of heavy m m gases did not exceed 1.3% [ 11 The paper presents B shon review of ori&d resuhs obtained by the authors on investigation of lasers operaungby 3p-3s nenn transitions (h=0.585,0 103,O 125 pm) by 1(X=O391,0428pm)and 2 (?.=0358,0381 lun)sy~lemsofnitroge~ byd.pargon (h=l 79 prn) md xenon @=2 03 urn) transitions, as well as on the study of multifrequency simultaneous lasing due to several ofthe above-mentioned transitions At optnnum and most interesting conditions helium is a major component of all the active mediums (SQ%, often >98-99%), the header inert %toms andlor molecules (Nz, Hi, NO) are used as a d m r e s The puy ofthe used gases, primanly helium, was undn special contcol, the content of moleculm impunties did not exceed 5. IOd % in helium and 5.10. % m neon and argon