| 1. |
- Birney, Ewan, et al.
(författare)
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Identification and analysis of functional elements in 1% of the human genome by the ENCODE pilot project
- 2007
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 447:7146, s. 799-816
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Tidskriftsartikel (refereegranskat)abstract
- We report the generation and analysis of functional data from multiple, diverse experiments performed on a targeted 1% of the human genome as part of the pilot phase of the ENCODE Project. These data have been further integrated and augmented by a number of evolutionary and computational analyses. Together, our results advance the collective knowledge about human genome function in several major areas. First, our studies provide convincing evidence that the genome is pervasively transcribed, such that the majority of its bases can be found in primary transcripts, including non-protein-coding transcripts, and those that extensively overlap one another. Second, systematic examination of transcriptional regulation has yielded new understanding about transcription start sites, including their relationship to specific regulatory sequences and features of chromatin accessibility and histone modification. Third, a more sophisticated view of chromatin structure has emerged, including its inter-relationship with DNA replication and transcriptional regulation. Finally, integration of these new sources of information, in particular with respect to mammalian evolution based on inter- and intra-species sequence comparisons, has yielded new mechanistic and evolutionary insights concerning the functional landscape of the human genome. Together, these studies are defining a path for pursuit of a more comprehensive characterization of human genome function.
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| 2. |
- Renugopalakrishnan, V, et al.
(författare)
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Nanomaterials for energy conversion applications
- 2009
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Ingår i: Nanomaterials for Energy Conversion Applications. - : American Scientific Publishers. ; , s. 155-178
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Bokkapitel (övrigt vetenskapligt/konstnärligt)
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| 3. |
- de Rossi, S., et al.
(författare)
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Longitudinal mode selection in constricted photonic crystal guides and electrically injected lasers
- 2005
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Ingår i: Journal of Lightwave Technology. - : Institute of Electrical and Electronics Engineers (IEEE). - 0733-8724 .- 1558-2213. ; 23:3, s. 1363-1368
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Tidskriftsartikel (refereegranskat)abstract
- Locally reducing the width of a wide photonic crystal (PhC) waveguide generates a constriction which acts as an internal reflector. We have simulated and measured the spectral behavior of a wide PhC waveguide locally constricted to a narrower PhC waveguide and ended by two cleaved facets, thus generating two coupled cavities. Passive structures as well as electrically injected active structures have been investigated. The multimode behavior of wide PhC waveguides is evidenced to play a deciding role. Modal reflection and transmission at the constriction are simulated and measured on passive PhC waveguides, when varying the constrictions' hole size and length. The spectral behavior of full-PhC electrically pumped lasers including such a constriction is measured and analyzed according to the constriction geometry. Design rules are finally proposed to take advantage of this coupled-cavities behavior for high rejection and high external efficiency monomode laser operation.
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| 4. |
- Fischer, A.M., et al.
(författare)
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Time-resolved cathodoluminescence of Mg-doped GaN
- 2008
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 93:15
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Tidskriftsartikel (refereegranskat)abstract
- The optical properties of GaN films doped with magnesium concentrations of the order of 1018 and 1019 cm-3 have been analyzed by picosecond time-resolved cathodoluminescence spectroscopy. Two luminescence bands in the vicinity of ~3.45 and ~3.27 eV are observed to increase in intensity with Mg concentration. They have been identified as related to acceptor-bound exciton and donor-acceptor pair (DAP) transitions, respectively. Time-resolved cathodoluminescence spectra, taken at low temperatures (~4 K), show that the lifetime of the DAP peak (3.27 eV) and of what appears to be its first longitudinal-optical phonon replica at ~3.19 eV decrease with increasing Mg concentration. These peaks differ in their recombination kinetics, strongly suggesting the existence of an underlying broad emission band which may be related to Mg. © 2008 American Institute of Physics.
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| 5. |
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| 6. |
- Martin, M. J., et al.
(författare)
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Evidence of Bloch wave propagation within photonic crystal waveguides
- 2006
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Ingår i: Applied physics. B, Lasers and optics (Print). - : Springer Science and Business Media LLC. - 0946-2171 .- 1432-0649. ; 82:1, s. 9-12
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Tidskriftsartikel (refereegranskat)abstract
- We report in this paper results obtained from characterizations of photonic band gap waveguide, using near field optical microscopy. We will show evidence of a Bloch wave propagating within our W1 photonic crystal waveguides (PCWs) structure, using a 2D Fourier transform approach. The processed image will then be compared to simulations obtained from plane wave method. This comparison exhibits that near-field measurements, using tapered optical fibers as probes, are mainly sensitive to the electric field propagating within the structure.
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| 7. |
- Aubin, G., et al.
(författare)
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Highly dispersive photonic crystal-based guiding structures
- 2006
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Ingår i: CLEO/QELS 2006. - : Optical Society of America. - 1557528136 - 9781557528131 ; , s. 972-974
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Konferensbidrag (refereegranskat)abstract
- Propagating modes supported by Photonic-Crystal guiding structures can demonstrate very high group velocity dispersion close to a cut-off. We investigate here the wavelength dependence of the dispersion for different Photonic Crystal structures.
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| 8. |
- Benyattou, T., et al.
(författare)
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Optical Bloch waves studied by near optical field microscopy
- 2005
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Ingår i: Journal of the Korean Physical Society. - 0374-4884 .- 1976-8524. ; 47, s. S72-S75
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Tidskriftsartikel (refereegranskat)abstract
- Photonic bandgap structures are very promising for the integration of optical function at the nanoscale level and particularly 2D structures perforated on a slab waveguide. In this context, photonic crystal waveguides obtained by removing rows of holes in the periodic structure are very interesting. We will present here, results of near field optical microscopy conducted on PCW. With a Fourier transform analysis of the image, we can image the Bloch waves propagating in the waveguide. The results are compared to FDTD simulations and we will show that the images obtained correspond to the electric field. Such result allows us to study the interaction of the optical tip with the electromagnetic field. 2D FDTD simulations of 1D photonic crystal interaction with a SNOM tip is presented. The results obtained confirm that the SNOM signal is mainly related to the electric field.
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| 9. |
- Berrier, Audrey, et al.
(författare)
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Characterization of the feature-size dependence in Ar/Cl2 chemically assisted ion beam etching of InP-based photonic crystal devices
- 2007
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Ingår i: Journal of Vacuum Science & Technology B. - : American Vacuum Society. - 1071-1023 .- 1520-8567. ; 25:1, s. 1-10
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Tidskriftsartikel (refereegranskat)abstract
- The authors address feature-size dependence in Ar/Cl-2, chemically assisted ion beam etching (CAIBE) in the context of the fabrication of photonic crystal (PhC) structures. They systematically investigate the influence of various parameters such as hole diameter (115-600 nm), etch duration (10-60 min), and ion beam energy (300-600 eV) on PhC etching in InP with Ar/Cl-2, CAIBE. For a 60 min etching at an Ar-ion energy of 400 eV, the authors report an etch depth of 5 mu m for hole diameters d larger than 300 nm; the etch depth is in excess of 3 mu m for d larger than 200 nm. The evolution of roughness at the bottom of the etched holes and its dependence on hole size and etching conditions,is discussed. The physical mechanism of the observed feature-size dependent etching (FSDE) is then discussed and the effect of the process parameters is qualitatively understood using a model combining the effect of ion sputtering and surface chemical reactions. Finally, the effect of FSDE on the PhC optical properties is assessed by measuring the quality factor of one-dimensional Fabry-Perot PhC cavities. The measured quality factors show a clear trend with the etch depth: the cavity Q increases as the etch depth increases.
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| 10. |
- Berrier, Audrey, et al.
(författare)
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Feature size effects in Ar/Cl-2 chemically assisted ion beam etching of InP-based protonic crystals
- 2006
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Ingår i: 2006 International Conference on Indium Phosphide and Related Materials Conference Proceedings. - NEW YORK : IEEE. - 9780780395572 ; , s. 341-344
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Konferensbidrag (refereegranskat)abstract
- This work addresses feature size effects (the lag-effect and roughness development) in chemically assisted ion beam etching (CAIBE) etching of InP-based photonic crystals. Photonic crystal fields The slope of the etch,with varying hole size and periods were etched with different etching times. depth versus diameter cures (lag-curves) reveals an aspect ratio dependence, with an etch limiting aspect ratio of the order of 25. A model of the etch rate specific to Ar/Cl-2 CAIBE is proposed. We calculate the etch rate using a physico-chemical model which takes in to account the effect of Ar-ion sputtering and surface chemical reactions. lit addition, it combines the aspect ratio dependence of the gas conductance of the etched holes. Finally, the bottom roughness of the etched holes is examined; its origin and evolution are discussed.
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| 11. |
- Berrier, Audrey, et al.
(författare)
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Feature size effects in chemically assisted ion beam etching of InP-based photonic crystals - art. no. 632707
- 2006
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Ingår i: Nanoengineering: Fabrication, Properties, Optics, and Devices III. - BELLINGHAM, WA : SPIE-INT SOC OPTICAL ENGINEERING. - 0819464066 ; , s. 32707-32707
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Konferensbidrag (refereegranskat)abstract
- This work addresses feature size effects (the lag-effect and roughness development) in chemically assisted ion beam etching (CAIBE) etching of InP-based photonic crystals. Photonic crystal fields with varying hole size and periods were etched with different etching times. The slope of the etch depth versus diameter curves (lag-curves) reveals a hole size dependence, with a critical aspect ratio higher than 25. A model for the etch rate specific to Ar/Cl-2 CAIBE is proposed. We calculate the etch rate using a physico-chemical model which takes in to account the effect of Ar-ion sputtering and surface chemical reactions. In addition, it combines the aspect ratio dependence of the gas conductance of the etched holes. The origin and evolution of the bottom roughness of the etched holes is examined. The impact of the feature size dependence of the etching on the photonic crystal optical properties is then assessed by measuring the quality-factor of one-dimensional Fabry-Perot cavities using the Internal Light Source method, and discussed in terms of hole shape and depth. A systematic trend between the determined quality factor (Q) and the lag-effect is evidenced: Q decreases from about 250 to 60 when the hole depth drops from 5 mu m to 2 mu m.
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| 12. |
- Berrier, Audrey, et al.
(författare)
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Impact of feature-size dependent etching on the optical properties of photonic crystal devices
- 2008
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 103:9, s. 096106-1-096106-3
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Tidskriftsartikel (refereegranskat)abstract
- Feature size dependence in Ar/Cl-2 chemically assisted ion beam etching of InP-based photonic crystals (PhCs) and its influence on the optical properties of PhC devices operating in the band gap are investigated. The analysis of the measured quality factors, the determined mirror reflectivities, and losses of one-dimensional Fabry-Perot cavities clearly demonstrates the importance of feature-size dependent etching. The optical properties show a dramatic improvement up to a hole depth of about 3.5 mu m that is primarily due to a significant reduction in extrinsic losses. However, beyond this hole depth, the improvement is at a lower rate, which suggests that extrinsic losses, although present, are not dominant.
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| 13. |
- El-Kallassi, P., et al.
(författare)
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Optical and local tuning of planar photonic crystals infiltrated with organic molecules
- 2007
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Ingår i: Conference on Lasers and Electro-Optics, 2007, CLEO 2007. - 9781557528346 ; , s. 1375-1376
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Konferensbidrag (refereegranskat)abstract
- We report on the optical tuning of InP-based planar photonic crystals (PhCs) infiltrated with a photoresponsive liquid crystal system. Preliminary results on the local tuning of PhC devices are also presented.
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| 14. |
- El-Kallassi, P., et al.
(författare)
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Optical and local tuning of planar photonic crystals infiltrated with organic molecules
- 2007
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Ingår i: Lasers and Electro-Optics, 2007 European Conference on and the International Quantum Electronics Conference. - 1424409306 - 9781424409303 ; , s. 4387041-
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Konferensbidrag (refereegranskat)abstract
- We report on the optical tuning of InP-based planar photonic crystals infiltrated with a photoresponsive liquid crystal system. Preliminary results on the local tuning of infiltrated structures are also presented.
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| 15. |
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| 16. |
- Kamp, M., et al.
(författare)
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Low loss InP based photonic crystal waveguides and resonators
- 2005
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Ingår i: Optoelectronic Integrated Circuits VII. - : SPIE - International Society for Optical Engineering. - 0819457035 ; , s. 249-256
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Konferensbidrag (refereegranskat)abstract
- We report on low-loss light propagation at the communication wavelength of 1.55 μm through straight two-dimensional photonic crystal waveguides patterned into InGaAsP/InP heterostructures. The linear defect waveguides along the ΓK direction of a triangular lattice of air holes were etched deeply into the semiconductor by Cl 2/Ar electron cyclotron resonance reactive ion etching. Efficient waveguiding was observed for both polarization directions, although a photonic band gap exists for only one of the polarization states. Propagation losses, determined by the Fabry-Pérot resonance method, are as low as 0.2 dB/mm and 1.5 dB/mm for waveguides based on seven and three missing rows of holes, respectively. Waveguide resonators with 100 GHz channel spacing and quality factors up to 15,000 have been realized by inserting photonic crystal mirrors into the waveguides. The dispersion of the resonators was measured using a phase shift technique. Values for the group velocity dispersion range from -250 ps/nm to +250 ps/nm at wavelengths around 1.55 μm, which is sufficient to compensate for the dispersion of 15 km standard single-mode fiber. Controlling the device temperature allows to tune the dispersive properties of the devices.
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| 17. |
- Kamp, M., et al.
(författare)
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Photonic crystal based active optoelectronic devices
- 2006
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Ingår i: Photonic Crystals: Advances in Design, Fabrication, and Characterization. - Weinheim, FRG : Wiley-Blackwell. - 9783527602599 ; , s. 329-346
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- We have described a number of ways to integrate photonic crystals with active optoelectronic devices. PhCs can be used as mirrors in semiconductor lasers where their high reflectivity allow the fabrication of lasers with small cavity length. Lasers with a length down to 100 μm and two PhC mirrors have been demonstrated.
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| 18. |
- Kamp, M., et al.
(författare)
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Photonic crystal waveguide based dispersion compensators
- 2006
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Ingår i: Proc SPIE Int Soc Opt Eng. - : SPIE. - 0819461652 - 9780819461650
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Konferensbidrag (refereegranskat)abstract
- We have investigated the dispersion properties of photonic crystal waveguide resonators. A passive InGaAsP/InP slab waveguide structure was used for the fabrication of the samples. The PhC waveguide resonators were defined by the omission of several rows of holes along the ΓK or ΓM direction of a triangular photonic crystal lattice. In addition, mirrors with a thickness of 1 to 4 rows of holes were inserted into the waveguide. An optimized dry etch process was used to etch the patterns to a depth of 3.5 μm through the waveguide layer. The group delay of the PhC devices was measured using the phase shift technique. The signal of a tunable laser was modulated at 3 GHz using a LiNbO 3 Mach-Zehnder modulator and detected with a high-frequency lightwave receiver. A phase sensitive detection with a network analyer measured the phase shift of the transmitted signal, which is proportional to the group delay. Close to the center of the resonances, the chromatic dispersion reaches values of -250 ps/nm and 250 ps/nm. This corresponds to the chromatic dispersion of 15 km standard fiber.
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| 19. |
- Lourdudoss, Sebastian, et al.
(författare)
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Heteroepitaxy and selective epitaxy for discrete and integrated devices
- 2006
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Ingår i: 2006 CONFERENCE ON OPTOELECTRONIC AND MICROELECTRONIC MATERIALS & DEVICES. - NEW YORK : IEEE. - 9781424405770 ; , s. 309-311
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Konferensbidrag (refereegranskat)abstract
- We present first results on heteroepitaxy of InP on silicon on insulator (SOI). We also demonstrate InP nanopillar fabrication by means of selective epitaxy. Selective epitaxy is also exploited to fabricate advanced photonic integrated devices for Optical Code Division Multiplex Access (OCDMA) networking applications.
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| 20. |
- Martz, J., et al.
(författare)
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Liquid crystal infiltration of InP-based planar photonic crystals
- 2006
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 99:10
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Tidskriftsartikel (refereegranskat)abstract
- A procedure for the infiltration of planar photonic crystals (PhCs) with liquid crystals (LCs) is presented. InP-based PhCs are infiltrated with the nematic LC-K15 in a specially designed high-vacuum chamber. The infiltration technique is validated and systematically characterized by measuring the transmission through the infiltrated PhCs at different temperatures and for different polarizations. The reproducibility and reliability of our procedure are demonstrated and a high filling efficiency is obtained.
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| 21. |
- Martz, J., et al.
(författare)
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Tuning the optical properties of planar photonic crystals by liquid crystal infiltration
- 2005
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Ingår i: Proc SPIE Int Soc Opt Eng. - : SPIE. ; , s. 1-14
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Konferensbidrag (refereegranskat)abstract
- Recently there has been a growing amount of attention devoted to tuneable photonic crystals (PhCs) where the optical response of PhC structures can be dynamically modified. We will show how infiltrating planar PhCs with a synthetic organic material allows the trimming and tuning of their optical properties. The potential of PhC infiltration will be demonstrated for InP-based planar PhCs consisting of a hexagonal array of air holes (hole diameter = 200 - 400 nm; air filling factor = 0.40-0.50) etched through a planar waveguide in which light emitters (i.e. quantum wells) were embedded to enable optical measurements. The PhC pores were infiltrated with LC-K15 (5CB) nematic liquid crystals (LCs) in a specifically designed vacuum chamber, thereby changing the refractive index contrast between the holes and the semiconductor (trimming). Moreover, the possibility of tuning the optical response of PhCs by an external perturbation (i.e. temperature) was demonstrated. The change of the PhC optical properties due to infiltration and temperature tuning was studied both experimentally and theoretically. Experimental measurements were compared to theoretical calculations in order to obtain information on the in-filling efficiency, the LC refractive index, and the molecule orientation inside the holes. In the first case, optical measurements were performed as a function of temperature, whilst the average LC director configuration was determined by comparing transmission spectra in the transverse electric and magnetic polarization directions.
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| 22. |
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| 23. |
- Qiu, Min, et al.
(författare)
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Negative refraction in two-dimensional photonic crystals
- 2005
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Ingår i: Applied Physics A. - : Springer Science and Business Media LLC. - 0947-8396 .- 1432-0630. ; 80:6, s. 1231-1236
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Tidskriftsartikel (refereegranskat)abstract
- We present some of our recent results for negative refraction in photonic crystals. The concept of negative refraction in photonic crystals is firstly introduced. Then, the propagation of electromagnetic waves in photonic crystals is systematically studied. By the layer Korringa-Kohn-Rostoker method, the coupling efficiency between external plane waves and the Bloch waves in photonic crystals is investigated. It is found that the coupling coefficient is highly angular dependent even for an interface between air with n=1 and a photonic crystal with effective index n(eff)=-1. It is also shown that, for point imaging by a photonic crystal slab, owing to the negative refraction, the influence of the surface termination on the transmission and the imaging quality is significant. Finally, we present results experimentally demonstrating negative refraction in a two-dimensional photonic crystal at optical communication wavelengths.
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| 24. |
- Schuller, C., et al.
(författare)
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Polarization-dependent optical properties of planar photonic crystals infiltrated with liquid crystals
- 2005
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 87:12
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Tidskriftsartikel (refereegranskat)abstract
- Photonic crystals with infiltrated liquid crystals are investigated in the 1.5 mu m wavelength regime. Due to the strong temperature dependence of the refractive index of liquid crystals, especially near the clearing point, i.e., at the transition between nematic and isotropic phase, the optical properties of photonic crystals can be tuned by small temperature changes. The refractive index of liquid crystals is birefringent and, therefore, sensitive for the polarization of the incident light. By using microresonators embedded into planar photonic crystal waveguides, the polarization dependence of the optical properties with and without infiltrated liquid crystal is investigated. The experimental results quantitatively agree well with the calculated photonic band structure assuming a temperature depending reorientation of the liquid crystal director field inside the holes.
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| 25. |
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| 26. |
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| 27. |
- Talneau, A., et al.
(författare)
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Highly dispersive photonic crystal-based coupled-cavity structures
- 2006
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 88:20, s. 201106-1-201106-3
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Tidskriftsartikel (refereegranskat)abstract
- We measured the wavelength dependence of the group velocity dispersion (GVD) for different photonic-crystal coupled-cavity structures through a phase analysis of the transmitted modulated signal. GVD values as large as 10(6)-10(7) times the dispersion of a standard single mode fiber are obtained when operating close to the band edge of the miniband, in agreement with the calculated group index. The GVD is found to be smaller for the structure based on more open cavities.
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| 28. |
- Zimmermann, J., et al.
(författare)
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Large dispersion in photonic crystal waveguide resonator
- 2005
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Ingår i: Electronics Letters. - : Institution of Engineering and Technology (IET). - 0013-5194 .- 1350-911X. ; 41:7, s. 414-415
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Tidskriftsartikel (refereegranskat)abstract
- Group delay and chromatic dispersion of a Fabry-Perot resonator embedded in a photonic crystal waveguide have been directly measured at 1.55 mu m avelength using the phase-shift technique. The photonic crystal waveguide resonator was fabricated in an InGaAsP/InP heterostructure and was designed to show a channel spacing of 100 GHz. Group velocity dispersion up to 250 ps/nm was observed.
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