Loss optimal monotone relabeling of noisy multi-criteria data sets

A method to relabel noisy multi-criteria data sets is presented, taking advantage of the transitivity of the non-monotonicity relation to formulate the problem as an efficiently solvable maximum independent set problem. A framework and an algorithm for general loss functions are presented, and the flexibility of the approach is indicated by some examples, showcasing the ease with which the method can handle application-specific loss functions. Both didactical examples and real-life applications are provided, using the zero-one, the L1 and the squared loss functions, as well as combinations thereof.     

Tree-based versus distance-based key recognition in musical audio

A tree-based method for the recognition of the tonal center or key in a musical audio signal is presented. Time-varying key feature vectors of 264 synthesized sounds are extracted from an auditory-based pitch model and converted into character strings using PCA-analysis and classification trees. The results are compared with distance-based methods. The characteristics of the new tonality analysis tool are illustrated on various examples. The potential of this method as a building stone in a music retrieval system is discussed.     

Compact Slanted Grating Couplers Between Optical Fiber and InP–InGaAsP Waveguides

We present theoretical and experimental results for compact slanted gratings for vertical coupling between single-mode fiber and InP-InGaAsP waveguides. The maximum calculated coupling efficiency is 59%. We have measured a coupling efficiency of 16% for a 10-mum-long slanted grating     

CLADISS-a longitudinal multimode model for the analysis of thestatic, dynamic, and stochastic behavior of diode lasers withdistributed feedback

A computer model called CLADISS is presented for the analysis of multisection diode lasers. The model allows for the analysis of a wide variety of multisection devices with discrete or distributed internal reflections. The simulator can carry out a threshold, DC, AC, and a noise analysis. The threshold analysis determines the threshold of the various longitudinal modes of the laser. The power versus current and the wavelength versus current characteristics are found with the self-consistent DC analysis. CLADISS includes all of the longitudinal variations by dividing each laser section in many short segments. Both the optical field and carrier density are discretized according to this segmentation. To demonstrate the capabilities of CLADISS some nonlinear effects in DFB lasers are treated. Instabilities induced in the side-mode suppression ratio by spatial hole burning are considered. The effects of spatial hole burning and side modes on the FM response on the linewidth are discussed     

Out-of-plane scattering in photonic crystal slabs

Photonic crystal slabs combine a slab waveguide with an in-plane photonic crystal. Light is then confined in-plane by the photonic crystal and out-of-plane by the slab waveguide. The etched structures will cause light to scatter out of the waveguide plane. We studied the out-of-plane scattering losses using a two-dimensional approximation of this three-dimensional structure, with etched slots instead of holes. Our simulation techniques include mode expansion with perfectly matched layer absorbing boundary conditions. We show that the losses increase with higher index contrast, but that with very high-index contrasts light can be coupled into lossless Bloch modes     

Rigorous electromagnetic analysis of dipole emission in periodically corrugated layers: the grating-assisted resonant-cavity light-emitting diode

We study the grating-assisted light-emitting diode, an LED design for high brightness based on a resonant cavity containing one- or two-dimensionally periodically corrugated layers (grating). We give in detail a generally applicable electromagnetic analysis based on the rigorous coupled-wave theory to calculate the extraction efficiency of spontaneous emission in a periodically corrugated layer structure. This general model is then specified on the grating-assisted resonant-cavity LED, showing simulated efficiencies of more than 40%.     

Stabilisation and control of widely tunable MG-Y lasers with integrated photodetectors

The control and stabilisation of a widely tunable modulated grating Y-branch (MG-Y) laser are discussed. A characterisation algorithm will be introduced, which produces for each standardised frequency a good operating point with a very small deviation from the wanted output frequency (plusmn2 GHz) and power (plusmn0.2 dB). In addition, a new stabilisation feedback scheme will be presented, which makes use of an external etalon for frequency stabilisation (a wavelength locker) and integrated photodetectors for mode stabilisation. This scheme guarantees that the laser continues operating at the wanted frequency even when the tuning sections degrade or when environmental conditions change. Thanks to those stabilisation algorithms, the lifetime of the device is greatly extended, in case of degrading tuning sections     

Wavelength and mode stabilization of widely tunable SG-DBR andSSG-DBR lasers

A novel mode stabilization scheme for widely tunable SG-DBR and SSG-DBR lasers is demonstrated. It is shown that a minimum in active section voltage is obtained when a cavity mode and a reflection peak of each DBR mirror are aligned. Locking the laser to such a local minimum in active section voltage therefore ensures stable single-mode operation     

Silicon Organic Hybrid Technology—A Platform for Practical Nonlinear Optics

A cost-effective route to build electrically as well as optically controlled modulators in silicon photonics is reviewed. The technology enables modulation at bit rates beyond 100 Gbit/s. This platform relies on the well-established silicon-based complementary metal-oxide-semiconductor processing technology for fabricating silicon-on-insulator (SOI) waveguides, while an organic cladding layer adds the required nonlinearity. The strength of this hybrid technology is discussed, and two key devices in communications are exemplarily regarded in more detail. The first device demonstrates demultiplexing of a 120 Gbit/s signal by means of four-wave mixing in a slot-waveguide that has been filled with a highly nonlinear chi⁽³⁾-organic material. The second device is a 100 Gbit/s/1 V electrooptic modulator based on a slow-light SOI photonic crystal covered with a chi⁽²⁾ -nonlinear organic material.     

Beam steering for wireless optical links based on an optical phased array in silicon

The ability to steer optical beams, crucial to the operation of high-speed optical wireless links may be achieved using optical phased array antennas which have significant potential in this application. The beam formed by the phased array antennas is steered by tuning the relative phase difference between the adjacent antenna elements which may be achieved nonmechanically. In this paper, the characteristics and behaviour of two dimensional optical phased arrays with a structure composed of 2?×?2, 4?×?4, and 16?×?16 antenna elements in beam steering are verified. The wavelength beam steering of ?0.16°/nm is measured along the θ direction with a required steering range (between main lobes) of 1.97° within a ?3 dB envelop of 5° extent in the θ direction and 7° extent in the Φ direction. To achieve two-dimensional beam steering, thermo-optic beam steering can be used in Φ direction. It is found that the thermo-optic phase tuning departs the expected quadratic dependence and is well characterised by a quartic dependence upon heater current or voltage.