ORCID Profile
0000-0003-4367-6601
Current Organisation
University of York
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Publisher: Optica Publishing Group
Date: 26-09-2008
DOI: 10.1364/OL.33.002206
Abstract: We demonstrate postprocessed microfluidic double-heterostructure cavities in silicon-based photonic crystal slab waveguides. The cavity structure is realized by selective fluid infiltration of air holes using a glass microtip, resulting in a local change of the average refractive index of the photonic crystal. The microcavities are probed by evanescent coupling from a silica nanowire. An intrinsic quality factor of 57,000 has been derived from our measurements, representing what we believe to be the largest value observed in microfluidic photonic crystal cavities to date.
Publisher: Optica Publishing Group
Date: 09-01-2008
DOI: 10.1364/OL.33.000147
Abstract: Switching light is one of the most fundamental functions of an optical circuit. As such, optical switches are a major research topic in photonics, and many types of switches have been realized. Most optical switches operate by imposing a phase shift between two sections of the device to direct light from one port to another, or to switch it on and off, the major constraint being that typical refractive index changes are very small. Conventional solutions address this issue by making long devices, thus increasing the footprint, or by using resonant enhancement, thus reducing the bandwidth. We present a slow-light-enhanced optical switch that is 36 times shorter than a conventional device for the same refractive index change and has a switching length of 5.2 microm.
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 2010
Publisher: OSA
Date: 2015
Publisher: The Optical Society
Date: 07-01-2016
DOI: 10.1364/OE.24.000443
Publisher: American Physical Society (APS)
Date: 27-04-2010
Publisher: The Optical Society
Date: 15-12-2010
DOI: 10.1364/OE.18.027627
Publisher: SPIE
Date: 05-2014
DOI: 10.1117/12.2052211
Publisher: Springer Science and Business Media LLC
Date: 05-02-2014
DOI: 10.1038/NCOMMS4246
Abstract: The ability to use coherent light for material science and applications is linked to our ability to measure short optical pulses. While free-space optical methods are well established, achieving this on a chip would offer the greatest benefit in footprint, performance and cost, and allow the integration with complementary signal-processing devices. A key goal is to achieve operation at sub-watt peak power levels and on sub-picosecond timescales. Previous integrated demonstrations require either a temporally synchronized reference pulse, an off-chip spectrometer or long tunable delay lines. Here we report a device capable of achieving single-shot time-domain measurements of near-infrared picosecond pulses based on an ultra-compact integrated CMOS-compatible device, which could operate without any external instrumentation. It relies on optical third-harmonic generation in a slow-light silicon waveguide. Our method can also serve as an in situ diagnostic tool to map, at visible wavelengths, the propagation dynamics of near-infrared pulses in photonic crystals.
Publisher: Elsevier BV
Date: 05-2009
Publisher: IEEE
Date: 10-2009
Publisher: IEEE
Date: 07-2012
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 11-2012
Publisher: Springer Science and Business Media LLC
Date: 15-01-2014
DOI: 10.1038/NCOMMS4160
Publisher: IEEE
Date: 06-2013
Publisher: IEEE
Date: 10-2009
Publisher: Optica Publishing Group
Date: 22-09-2008
DOI: 10.1364/OE.16.015887
Abstract: We demonstrate the spectral and spatial reconfigurability of photonic crystal double-heterostructure cavities in silicon by microfluidic infiltration of selected air holes. The lengths of the microfluidic cavities are changed by adjusting the region of infiltrated holes in steps of several microns. We systematically investigate the spectral signature of these cavities, showing high Q-factor resonances for a broad range of cavity lengths. The fluid can be removed by immersing the device in toluene, offering complete reconfigurability. Our cavity writing technique allows for tolerances in the infiltration process and provides flexibility as it can be employed at any time after photonic crystal fabrication.
Publisher: AIP Publishing
Date: 08-06-2009
DOI: 10.1063/1.3152998
Abstract: We present a principle for the temperature stabilization of photonic crystal (PhC) cavities based on optofluidics. We introduce an analytic method enabling a specific mode of a cavity to be made wavelength insensitive to changes in ambient temperature. Using this analysis, we experimentally demonstrate a PhC cavity with a quality factor of Q≈15 000 that exhibits a temperature-independent resonance. Temperature-stable cavities constitute a major building block in the development of a large suite of applications from high-sensitivity sensor systems for chemical and biomedical applications to microlasers, optical filters, and switches.
Publisher: IEEE
Date: 05-2011
Publisher: OSA
Date: 2016
Publisher: AIP Publishing
Date: 15-02-2010
DOI: 10.1063/1.3314287
Publisher: SPIE
Date: 30-04-2010
DOI: 10.1117/12.858154
Publisher: IEEE
Date: 11-2008
Publisher: Optica Publishing Group
Date: 04-09-2007
DOI: 10.1364/OL.32.002638
Abstract: We study efficient injectors for coupling light from z-invariant ridge waveguides into slow Bloch modes of single-row defect photonic crystal waveguides. Two-dimensional vectorial computations performed with a Bloch mode theory approach predict that very high efficiencies (>90%) can be achieved for injector lengths of only a few wavelengths in length, even for small group velocities in the range of c/100-c/400. This result suggests that photonic crystal devices operating with slow waves can be interfaced with classical waveguides without sacrificing compactness.
Publisher: IEEE
Date: 09-2012
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 2009
Publisher: Optica Publishing Group
Date: 30-03-2010
DOI: 10.1364/OE.18.007770
Publisher: American Physical Society (APS)
Date: 05-11-2009
Publisher: Optica Publishing Group
Date: 2008
DOI: 10.1364/OE.16.001365
Abstract: The mini-stopband (MSB) of a W3 line-defect photonic crystal waveguide is used as a mirror for a GaAs based quantum-dot laser. Single mode, continuous-wave lasing is demonstrated for broad area lasers up to a current of 125 mA (2.7 x laser threshold), which demonstrates the high degree of mode selectivity of the MSB mirror. FDTD calculations indicate that optimisation of the mirror interface could lead to a further fourfold increase in reflectivity resulting in significantly reduced thresholds.
Publisher: Optica Publishing Group
Date: 27-03-2008
DOI: 10.1364/OE.16.004991
Abstract: The confinement and controlled movement of metal nanoparticles and nanorods is an emergent area within optical micromanipulation. In this letter we experimentally realise a novel trapping geometry near the plasmon resonance using an annular light field possessing a helical phasefront that confines the nanoparticle to the vortex core (dark) region. We interpret our data with a theoretical framework based upon the Maxwell stress tensor formulation to elucidate the total forces upon nanometric particles near the particle plasmon resonance. Rotation of the particle due to orbital angular momentum transfer is observed. This geometry may have several advantages for advanced manipulation of metal nanoparticles.
Publisher: Optica Publishing Group
Date: 23-10-2009
DOI: 10.1364/OL.34.003292
Publisher: Springer Science and Business Media LLC
Date: 04-11-2013
DOI: 10.1038/SREP03087
Publisher: The Optical Society
Date: 04-10-2011
DOI: 10.1364/OE.19.020681
Publisher: IEEE
Date: 05-2013
Publisher: IEEE
Date: 2008
Publisher: The Optical Society
Date: 31-03-2011
Publisher: SPIE
Date: 11-02-2010
DOI: 10.1117/12.840948
Publisher: The Optical Society
Date: 26-08-2011
DOI: 10.1364/OL.36.003413
Publisher: SPIE
Date: 18-04-2016
DOI: 10.1117/12.2231199
Publisher: IEEE
Date: 07-2008
Publisher: The Optical Society
Date: 15-01-2014
DOI: 10.1364/OL.39.000363
Publisher: Springer Science and Business Media LLC
Date: 22-03-2009
Publisher: SPIE
Date: 11-02-2010
DOI: 10.1117/12.840945
Publisher: The Optical Society
Date: 14-10-2010
DOI: 10.1364/OE.18.022915
Publisher: IEEE
Date: 10-2011
Publisher: IEEE
Date: 05-2007
Publisher: IEEE
Date: 08-2011
Publisher: AIP Publishing
Date: 08-2019
DOI: 10.1063/1.5110275
Abstract: We demonstrate the emission of photons from a single molecule into a hybrid gap plasmon waveguide. Crystals of anthracene, doped with dibenzoterrylene (DBT), are grown on top of the waveguides. We investigate a single DBT molecule coupled to the plasmonic region of one of the guides and determine its in-plane orientation, excited state lifetime, and saturation intensity. The molecule emits light into the guide, which is remotely out-coupled by a grating. The second-order autocorrelation and cross-correlation functions show that the emitter is a single molecule and that the light emerging from the grating comes from that molecule. The coupling efficiency is found to be βWG = 11.6(1.5)%. This type of structure is promising for building new functionality into quantum-photonic circuits, where localized regions of strong emitter-guide coupling can be interconnected by low-loss dielectric guides.
Publisher: Optica Publishing Group
Date: 06-03-2008
DOI: 10.1364/OE.16.003712
Abstract: Near-field optical micromanipulation permits new possibilities for controlled motion of trapped objects. In this work, we report an original geometry for optically deflecting and sorting micro-objects employing a total internal reflection microscope system. A small beam of laser light is delivered off-axis through a total internal reflection objective which creates an elongated evanescent illumination of light at a glass/water interface. Asymmetrical gradient and scattering forces from this light field are seen to deflect and sort polystyrene microparticles within a fluid flow. The speed of the deflected objects is dependent upon their intrinsic properties. We present a finite element method to calculate the optical forces for the evanescent waves. The numerical simulations are in good qualitative agreement with the experimental observations and elucidate features of the particle trajectory. In the size range of 1 microm to 5 microm in diameter, polystyrene spheres were found to be guided on average 2.9 +/- 0.7 faster than silica spheres. The velocity increased by 3.0 +/- 0.5 microms(-1) per microm increase in diameter for polystyrene spheres and 0.7 +/- 0.2 microms(-1) per microm for silica. We employ this size dependence for performing passive optical sorting within a microfluidic chip and is demonstrated in the accompanying video.
Publisher: The Optical Society
Date: 15-11-2013
DOI: 10.1364/OE.21.028794
Publisher: Optica Publishing Group
Date: 12-02-2009
DOI: 10.1364/OE.17.002944
Abstract: We report nonlinear measurements on 80microm silicon photonic crystal waveguides that are designed to support dispersionless slow light with group velocities between c/20 and c/50. By launching picoseconds pulses into the waveguides and comparing their output spectral signatures, we show how self phase modulation induced spectral broadening is enhanced due to slow light. Comparison of the measurements and numerical simulations of the pulse propagation elucidates the contribution of the various effects that determine the output pulse shape and the waveguide transfer function. In particular, both experimental and simulated results highlight the significant role of two photon absorption and free carriers in the silicon waveguides and their reinforcement in the slow light regime.
Publisher: Optica Publishing Group
Date: 18-04-2008
DOI: 10.1364/OE.16.006227
Abstract: We present a systematic procedure for designing "flat bands" of photonic crystal waveguides for slow light propagation. The procedure aims to maximize the group index - bandwidth product by changing the position of the first two rows of holes of W1 line defect photonic crystal waveguides. A nearly constant group index - bandwidth product is achieved for group indices of 30-90 and as an ex le, we experimentally demonstrate flat band slow light with nearly constant group indices of 32.5, 44 and 49 over 14 nm, 11 nm and 9.5 nm bandwidth around 1550 nm, respectively.
Publisher: Optica Publishing Group
Date: 17-03-2010
DOI: 10.1364/OE.18.006831
Publisher: Elsevier BV
Date: 05-2010
Publisher: IEEE
Date: 09-2009
Publisher: Optica Publishing Group
Date: 2006
DOI: 10.1364/OE.14.009211
Abstract: We report the demonstration of a compact, all-solid-state polymer laser system comprising of a Gallium Nitride (GaN) semiconductor diode laser as the pump source. The polymer laser was configured as a surface emitting, distributed Bragg reflector laser (DBR), based on a novel energy transfer blend of Coumarin 102 and the conjugated polymer poly(2-methoxy-5-(2'-ethylhexyloxy)-1,4-phenylene vinylene). In this configuration, diode pumping was possible both due to the improved quality of the resonators and the improved harvesting of the diode laser light.
Publisher: Optica Publishing Group
Date: 2007
DOI: 10.1364/OE.15.013129
Abstract: We examine the effects of disorder on propagation loss as a function of group velocity for W1 photonic crystal (PhC) waveguides. Disorder is deliberately and controllably introduced into the photonic crystal by pseudo-randomly displacing the holes of the photonic lattice. This allows us to clearly distinguish two types of loss. Away from the band-edge and for moderately slow light (group velocity c/20-c/30) loss scales sub-linearly with group velocity, whereas near the band-edge, reflection loss increases dramatically due to the random and local shift of the band-edge. The optical analysis also shows that the random fabrication errors of our structures, made on a standard e-beam lithography system, are below 1 nm root mean square.
Publisher: IEEE
Date: 07-2014
DOI: 10.1109/SUM.2014.79
Publisher: SPIE
Date: 19-08-2010
DOI: 10.1117/12.861474
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 05-2015
Publisher: SPIE-Intl Soc Optical Eng
Date: 02-2010
DOI: 10.1117/1.3332850
Publisher: IEEE
Date: 09-2009
Publisher: SPIE
Date: 12-02-2009
DOI: 10.1117/12.811083
Publisher: AIP Publishing
Date: 15-06-2009
DOI: 10.1063/1.3153989
Abstract: We demonstrate that two coupled photonic-crystal waveguides can route two subsequently arriving light pulses to different output ports even though the pulses are only 3 ps apart. This rerouting of light is due to an ultrafast shift in the transmittance spectrum triggered by the generation of electrons and holes in the Si base material by a femtosecond laser pulse. The use of slow-light modes allows for a coupler length of only 5.2 μm. Since these modes are not directly involved, the 3 ps dead time is solely determined by the duration of the input pulse rather than its transit time through the device.
Publisher: The Optical Society
Date: 22-06-2015
DOI: 10.1364/OE.23.017101
Publisher: IEEE
Date: 09-2009
Publisher: The Optical Society
Date: 21-07-2011
DOI: 10.1364/OL.36.002818
Publisher: The Optical Society
Date: 29-04-2011
DOI: 10.1364/OL.36.001728
Publisher: The Optical Society
Date: 30-10-2014
Publisher: IEEE
Date: 2008
Publisher: Optica Publishing Group
Date: 10-10-2008
DOI: 10.1364/OE.16.017076
Abstract: We report on the fabrication and characterization of silicon photonic crystal waveguides completely embedded in silica. These waveguides offer a robust alternative to air-membranes and are fully compatible with monolithic integration. Despite the reduced refractive index contrast compared to the air-membranes, these waveguides offer a considerable operating range of approximately 10 nm in the 1550 nm window. While the reduced index contrast weakens the perturbations due to surface roughness, we measure losses of 35 +/- 3dB/cm compared to 12 +/- 3 dB/cm for nominally identical air-membranes. Numerical analysis reveals that the difference in loss results from the different mode distribution and group index of the respective waveguide modes. Radius disorder is used as a fitting parameter in the numerical simulations with the best fits found for disorder levels of 1.4 - 1.7 nm RMS, which attest to the high quality of our structures.
Publisher: Springer Science and Business Media LLC
Date: 29-01-2016
DOI: 10.1038/NCOMMS10427
Abstract: Temporal optical solitons have been the subject of intense research due to their intriguing physics and applications in ultrafast optics and supercontinuum generation. Conventional bright optical solitons result from the interaction of anomalous group-velocity dispersion and self-phase modulation. Here we experimentally demonstrate a class of bright soliton arising purely from the interaction of negative fourth-order dispersion and self-phase modulation, which can occur even for normal group-velocity dispersion. We provide experimental and numerical evidence of shape-preserving propagation and flat temporal phase for the fundamental pure-quartic soliton and periodically modulated propagation for the higher-order pure-quartic solitons. We derive the approximate shape of the fundamental pure-quartic soliton and discover that is surprisingly Gaussian, exhibiting excellent agreement with our experimental observations. Our discovery, enabled by precise dispersion engineering, could find applications in communications, frequency combs and ultrafast lasers.
Publisher: Springer Science and Business Media LLC
Date: 10-10-2013
DOI: 10.1038/NCOMMS3582
Publisher: IOP Publishing
Date: 04-11-2010
Publisher: IEEE
Date: 2008
Publisher: IOP Publishing
Date: 24-09-2010
Publisher: The Optical Society
Date: 19-01-2011
DOI: 10.1364/OE.19.001991
Publisher: Springer Science and Business Media LLC
Date: 09-03-2016
DOI: 10.1038/NCOMMS11048
Abstract: Nature Communications 7: Article number: 10427 (2016) Published: 29 January 2016 Updated: 9 March 2016 The original version of this article contained an error in the spelling of the author C. Martijn de Sterke, which was incorrectly given as de Sterke C. Martijn. This has now been corrected in both the PDF and HTML versions of the article.
Publisher: IEEE
Date: 06-2007
Publisher: Optica Publishing Group
Date: 31-03-2010
DOI: 10.1364/OL.35.001073
Publisher: The Optical Society
Date: 25-03-2011
DOI: 10.1364/OL.36.001170
Publisher: The Endocrine Society
Date: 02-2011
DOI: 10.1210/ME.2010-0295
Abstract: The acid-labile subunit (ALS) regulates IGF bioavailability by forming heterotrimeric complexes with IGFs and IGF-binding protein-3 (IGFBP-3). A homozygous missense mutation (D440N) resulting in undetectable circulating levels of ALS with a concomitant reduction in IGF-I and IGFBP-3 has been reported to cause mild growth retardation. To understand how this particular mutation affects ALS circulating levels and IGF-transport function, we expressed recombinant ALS and its variants, D440N-ALS, T442A-ALS, and D440N/T442A-ALS, using adenovirus vectors. Compared with wild-type ALS, the secretion of D440N-ALS was 80% lower. The D440N mutation was proposed to generate an N-glycosylation site additional to the seven existing motifs in ALS. D440N-ALS appeared larger than ALS, attributable to N-linked glycans because deglycosylation with N-glycosidase F reduced both proteins to the same molecular mass. When ALS was incubated with IGF-I and IGFBP-3, 70–80% of IGF-I was detected by gel-filtration chromatography in forms corresponding to the 150-kDa ternary complex. In contrast, when D440N-ALS was tested, less than 30% of IGF-I was found in high molecular mass complexes. Two other ALS variants mutated in the same putative glycosylation site, D440N/T442A-ALS and T442A-ALS, showed similar chromatographic profiles to wild-type ALS. The D440N mutation in ALS generates a hyperglycosylated form with impaired secretion and complex formation, potentially leading to dysregulation of endocrine IGF, thus contributing to the growth retardation observed in the affected patient. This is the first study to explain how a natural mutation, D440N, in ALS impairs its function.
Publisher: IEEE
Date: 11-2010
Publisher: IEEE
Date: 09-2010
Publisher: The Optical Society
Date: 27-11-2013
DOI: 10.1364/OL.38.005176
Publisher: OSA
Date: 2016
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 06-2010
Publisher: The Optical Society
Date: 10-06-2014
DOI: 10.1364/OL.39.003575
Location: United States of America
Location: United Kingdom of Great Britain and Northern Ireland
Location: United Kingdom of Great Britain and Northern Ireland
Location: United Kingdom of Great Britain and Northern Ireland
No related grants have been discovered for Thomas Krauss.