| 1. |
- Lewen, R., et al.
(author)
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High frequency characterization of a GaInAs/InP electronic waveguide T-branch switch
- 2002
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In: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 91:4, s. 2398-2402
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Journal article (peer-reviewed)abstract
- We report comprehensive microwave measurements on a T-branch switch; a GaInAs/InP electron waveguide based structure. The study includes a small signal model of the device where limitations of high frequency operation are discussed. An example of large signal operation where the nonlinearity of the device is exploited by operating the T-branch switch as a frequency multiplier is demonstrated.
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| 2. |
- Aggerstam, Thomas, et al.
(author)
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GaN/AlN multiple quantum well structures grown by MBE on GaN templates for 1.55 mu m intersubband absorption
- 2007
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In: Quantum Sensing and Nanophotonic Devices IV. - : SPIE. - 9780819465924 ; 6479, s. 64791E-
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Conference paper (peer-reviewed)abstract
- We have used MBE to grow MQW structures on MOVPE GaN/sapphire templates. The MQW devices are intended for high speed intersubband electroabsorption modulator devices operating at 1.55-mu m. The GaN/AlN multiple quantum well material was systematically studied regarding the surface morphology, structural characterization and optical property by atomic force microscopy, X-ray diffraction and Fourier transform infrared spectroscopy, respectively. The intersubband resonance energy was also calculated considering many-body effects in n-type doped structures. The multiple quantum well structure showed superior performance in terms of linewidth when grown on GaN templates as compared on sapphire. GaN quantum well and AlN barriers with a thickness of 3.3 and 4.2 nm respectively resulted in FWHM of the intersubband absorption peak as low as 93 meV at an absorption energy of 700 meV. This is promising for intersubband modulator applications.
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| 3. |
- Akram, Nadeem, 1971-
(author)
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Photonic devices with MQW active material and waveguide gratings : modelling and characterisation
- 2005
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Doctoral thesis (other academic/artistic)abstract
- The research work presented in this thesis deals with modelling, design and characterisation of passive and active optical waveguide devices. The rst part of the thesis is related to algorithm development and numerical modelling of planar optical waveguides and gratings using the Method of Lines (MoL). The basic three-point central-di erence approximation of the δ2=δx2 operator used in the Helmholtz equation is extended to a new ve-point and seven-point approximation with appropriate interface conditions for the TE and TM elds. Di erent structures such as a high-contrast waveguide and a TM surface plasmon mode waveguide are simulated, and improved numerical accuracy for calculating the optical mode and propagation constant is demonstrated. A new fast and stable non-paraxial bi-directional beam propagation method, called Cascading and Doubling algorithm, is derived to model deep gratings with many periods. This algorithm is applied to model a quasi-guided multi-layer anti-resonant reecting optical waveguide (ARROW) grating polarizing structure. In the second part of the thesis, our focus is on active optical devices such as vertical-cavity and edge-emitting lasers. With a view to improve the bandwidth of directly modulated laser, an InGaAsP quantum well with InGaAlAs barrier is studied due to its favorable band o set for hole injection as well as for electron con nement. Quantum wells with di erent barrier bandgap are grown and direct carrier transport measurements are done using time and wavelength resolved photoluminescence upconversion. Semi-insulating regrown Fabry-Perot lasers are manufactured and experimentally evaluated for light-current, optical gain, chirp and small-signal performance. It is shown that the lasers having MQW with shallow bandgap InGaAlAs barrier have improved carrier transport properties, better T0, higher di erential gain and lower chirp. For lateral current injection laser scheme, it is shown that a narrow mesa is important for gain uniformity across the active region. High speed directly modulated DBR lasers are evaluated for analog performance and a record high spurious free dynamic range of 103 dB Hz2=3 for frequencies in the range of 1-19 GHz is demonstrated. Large signal transmission experiment is performed at 40 Gb/s and error free transmission for back-to-back and through 1 km standard single mode ber is achieved.
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| 4. |
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| 5. |
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| 6. |
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| 7. |
- Andersson, Thorvald, 1946, et al.
(author)
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Macroscopic defects in GaN/AlN multiple quantum well structures grown by MBE on GaN templates
- 2009
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In: Microelectronics Journal. - : Elsevier BV. - 0026-2692. ; 40:2, s. 360-362
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Journal article (peer-reviewed)abstract
- We have used MBE to grow in AlN/GaN superlattices, with different number of periods, on 2.5-mu m-thick MOVPE-GaN templates to study the development of defects such as surface deformation due to strain. After growth the samples were studied by atomic force microscopy (AFM), transmission electron microscopy (TEM), XRD and Fourier transform infrared spectroscopy (FT-IR). The strain increased with the number of quantum wells (QWs) and eventually caused defects such as microcracks visible by optical microscopy at four or more QW periods. High-resolution TEM images showed shallow recessions on the surface (surface deformation) indicating formation of microcracks in the MQW region. The measured intersubband (IS) absorption linewidth from a four period structure was 97 meV, which is comparable with the spectrum from a 10 period structure at an absorption energy of similar to 700 meV. This indicates that the interface quality of the MQW is not substantially affected by the presence of cracks.
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| 8. |
- Arve, Per, et al.
(author)
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Propagation of two-dimensional pulses in electromagnetically induced transparency media
- 2004
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In: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 69:6, s. 063809-
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Journal article (peer-reviewed)abstract
- The propagation in two dimensions of "optical" pulses in electromagnetically induced transparency media is analyzed. Results are presented for coupled Maxwell-Bloch equations with slowly varying envelope approximation, for both adiabatic and nonadiabatic situations. The possibility of changing the direction of the pulse by a switch of control beam direction is investigated in detail.
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| 9. |
- Berglind, Eilert, et al.
(author)
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Microwave engineering approach to metallic based photonic waveguides and waveguide components
- 2006
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In: Proceedings of International Symposium on Biophotonics, Nanophotonics and Metamaterials. - 9780780397736 ; , s. 247-251
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Conference paper (peer-reviewed)abstract
- Approaches from microwave engineering are used to analyze metallic waveguides and wave-guiding circuits and to point out the usefulness of these techniques in photonics applications, for design of components and to achieve higher densities of integration in integrated photonics circuits than is the case today. It is also find that the losses are severe for certain applications.
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| 10. |
- Berglind, Eilert, et al.
(author)
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On the Possibilities to Create a Negative Permittivity Metamaterial with Zero Imaginary Part of the Permittivity at a Specific Frequency-Electrical Network Theory Approach
- 2012
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In: IEEE Journal of Quantum Electronics. - 0018-9197 .- 1558-1713. ; 48:4, s. 507-511
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Journal article (peer-reviewed)abstract
- A permittivity function suggested in the literature describing a material that exhibits negative permittivity and no loss at a specific frequency (and losses at other frequencies) is analyzed using electrical network theory. An equivalent circuit of the polarization admittance consisting of RLC components is derived. Further, a proof is given showing that if the admittance is lossless at a specific frequency, then all components with losses (resistances) in the circuit have to be short circuited or blocked or virtually disconnected at this frequency by the use of ideal lossless resonant LC circuits. However, in the literature, inductors in metamaterials are associated with inherently lossy metal nanoparticles, hence invalidating the suggested permittivity function unless a lossless inductor at optical frequencies is found or proved possible.
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| 11. |
- Berglind, Eilert, et al.
(author)
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Plasmonic/metallic passive waveguides and waveguide components for photonic dense integrated circuits : a feasibility study based on microwave engineering
- 2010
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In: IET Optoelectronics. - : Institution of Engineering and Technology (IET). - 1751-8768. ; 4:1, s. 1-16
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Journal article (peer-reviewed)abstract
- To investigate the potential for dense integration of photonic components, we analyse passive plasmonic/metallic waveguides and waveguide components at optical frequencies by using mostly microwave engineering approaches. Four figures of performance are formulated that are utilised to compare the characteristics of four different slab waveguides with zero frequency cut-off modes. Three of these are metallic based whereas the fourth one, which also serves as a reference, is dielectric based with high index-contrast. It is found that all figures of performance cannot be optimised independently; in particular there is a trade-off between the waveguide Q-value and the transversal field confinement. Microwave methods are used to design several photonic transmission line components. The small Q-value of the metallic waveguides is the main disadvantage when using materials and telecom frequencies of today. Hence plasmonic waveguides do not offer full functionality for some important integrated components, being severe for frequency-selective applications. To achieve a dense integration, it is concluded that new materials are needed that offer Q-values several orders of magnitude higher than metals.
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| 12. |
- Berrier, Audrey, et al.
(author)
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Negative Refraction at Infrared Wavelengths in a Two-Dimensional Photonic Crystal
- 2004
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In: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 93:073902
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Journal article (peer-reviewed)abstract
- We report on the first experimental evidence of negative refraction at telecommunication wavelengths by a two-dimensional photonic crystal field. Samples were fabricated by chemically assisted ion beam etching in the InP-based low-index constrast system. Experiments of beam imaging and light collection show light focusing by the photonic crystal field. Finite-difference time-domain simulations confirm that the observed focusing is due to negative refraction in the photonic crystal area.
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| 13. |
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| 14. |
- Bratkovsky, A. M., et al.
(author)
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Properties of nanostructured metamaterials at optical frequencies
- 2008
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Conference paper (peer-reviewed)abstract
- A variety of metamaterials has been demonstrated recently that support backward waves and negative refraction (Negative Index Materials, NIM.) In particular, these materials enable sub-wavelength resolution that makes them even more interesting, especially in optical domain rather than at microwave frequencies where their unusual properties were known for decades. We describe below theoretical and experimental studies of the so-called 'fishnet' metal-spacer holearray metamaterials, which exhibit NIM behavior at optical frequencies, having unit cell size of a few 100s nm. We demonstrate experimentally that their refractive index can be modulated very fast and very strongly (from -2.4 to -1.5) around the communication wavelength of =1.55 um, in good agreement with the FDTD results. We also discuss a problem of loss compensation in those materials with hefty Ohmic losses by using gain media and local field enhancement in metallic nanoparticles ensembles that enable SERS.
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| 15. |
- Chacinski, Marek, et al.
(author)
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50 Gb/s modulation and/or detection with a travelling-wave electro-absorption transceiver
- 2008
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In: 2008 Conference on Optical Fiber Communication/National Fiber Optic Engineers Conference. - 9781557528568 ; , s. 94-96
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Conference paper (peer-reviewed)abstract
- Electro-Absorption-Transceiver (EAT) structures used as efficient Travelling-Wave Electro-Absorption-Modulator (TWEAM) as well as Travelling-Wave-Photo-Detector (TWPD) are investigated. Clear eye-openings at 50Gb/s for modulation and for detection are presented. Transmission over 2.2km and 5km SSMF were achieved.
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| 16. |
- Chacinski, Marek, et al.
(author)
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Electroabsorption Modulators Suitable for 100-Gb/s Ethernet
- 2008
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In: IEEE Electron Device Letters. - 0741-3106 .- 1558-0563. ; 29:9, s. 1014-1016
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Journal article (peer-reviewed)abstract
- The design of a traveling-wave electroabsorption modulator (TWEAM) has been improved to decrease the drive voltage. The absorption layer was optimized and together with a novel segmentation of microwave design was introduced to increase the active modulator length. The resulting -3-dBe bandwidth of fabricated devices was estimated to be 99 GHz. Extinction ratios of 10 dB back-to-back and 6.7 dB after transmission over 2.2-km long fiber were measured with an incident drive voltage of only 2 V peak to peak. This TWEAM performance is believed to constitute a new state of the art for modulators suitable for 100-Gb/s Ethernet with on-off keying.
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| 17. |
- Chacinski, Marek, et al.
(author)
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ETDM Transmitter Module for 100-Gb/s Ethernet
- 2010
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In: IEEE Photonics Technology Letters. - : Institute of Electrical and Electronics Engineers (IEEE). - 1041-1135 .- 1941-0174. ; 22:2, s. 70-72
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Journal article (peer-reviewed)abstract
- Performance of a packaged distributed-feedback travelling-wave electroabsorption modulator module for data transmission at 100 Gb/s is presented for the first time. Clearly open eye diagrams at 80 Gb/s with an extinction ratio ( ER) of 4.9 dB and 100 Gb/s with ER 4.2 dB ( limited by measurement setup) are demonstrated together with data transmission over 100-m-long standard single-mode fiber and over dispersion-compensated 10-km fiber link.
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| 18. |
- Chacinski, Marek, et al.
(author)
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Modulation and chirp evaluation of 100 GHz DFB-TWEAM
- 2010
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In: European Conference on Optical Communication, ECOC. - NEW YORK : IEEE.
-
Conference paper (peer-reviewed)abstract
- The modulation and chirp performance of an InGaAsP based monolithically integrated distributed feedback (DFB) laser and travelling wave electro-absorption modulator (TWEAM) designed for 100Gb/s operation is presented. Open eye-diagrams at 100Gb/s, and error free 50Gb/s BER (limited by measurement system) were achieved. The chirp factor varied between 1.5 and 0 for absorptions between 10% and 90%.
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| 19. |
- Chacinski, Marek, et al.
(author)
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Monolithically Integrated 100 GHz DFB-TWEAM
- 2009
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In: Journal of Lightwave Technology. - 0733-8724 .- 1558-2213. ; 7:16, s. 3410-3415
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Journal article (peer-reviewed)abstract
- A monolithically integrated distributed feedback (DFB) laser and traveling-wave electro-absorption modulator (TWEAM) with >= 100 GHz -dBe bandwidth suitable for Non-return-to-zero (NRZ) operation with on-off keying (OOK) is presented. The steady-state, small-signal modulation response, microwave reflection, chirp characteristic, and both data operation and transmission were investigated. The DFB-TWEAM was found to be an attractive candidate for future short distance communication in high bitrates systems.
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| 20. |
- Chacinski, Marek, et al.
(author)
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Monolithically Integrated DFB-EA for 100 Gb/s Ethernet
- 2008
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In: IEEE Electron Device Letters. - : Institute of Electrical and Electronics Engineers (IEEE). - 0741-3106 .- 1558-0563. ; 29:12, s. 1312-1314
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Journal article (peer-reviewed)abstract
- The world's first monolithically integrated distributed feedback laser and electroabsorption (EA) modulator with an expected >= 100 GHz -3 dBe bandwidth suitable for 100 Gb/s operation with on-off keying is presented. The design of the EA modulator uses a traveling-wave structure with three active segments and a total active length of 180 mu m resulting in similar to 2.5 V peak-to-peak drive voltage for 10 dB optical extinction ratio and low electrical reflection.
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| 21. |
- Chacinski, Marek, et al.
(author)
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Monolithically Integrated DFB-EAT for Transmission beyond 50 Gb/s
- 2008
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In: ICTON MEDITERR WINTER CONFER. - New York : IEEE. - 9781424434848 ; , s. 211-214
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Conference paper (peer-reviewed)abstract
- We demonstrate >= 60 GHz Electro-Absorption-Transceiver (EAT) composed of monolithically integrated Distributed-Feedback laser (DFB) with low drive voltage Electro-Absorption-Modulator. Clear eye-openings at 50 Gb/s for modulation and detection are presented. The device can be used as efficient and compact size transmitter or as detector in direct 80 Gb/s links. Transmission over 7.2 km long fibre with dispersion compensation is achieved.
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| 22. |
- Chen, Jiajia, et al.
(author)
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Comparison of hybrid WDM/TDM passive optical networks (PONs) with protection
- 2008
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In: 34th European Conference on Optical Communication, 2008, ECOC 2008.
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Conference paper (peer-reviewed)abstract
- We present the evolution of PON protection and compare reliability performance related to investment and management cost for some representative cases. Our results can indicate the most cost efficient architectures.
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| 23. |
- Chen, Jiajia, et al.
(author)
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Novel Architectures of Asynchronous Optical Packet Switch
- 2007
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In: 33rd European Conference and Exhibition on Optical Communication ECOC’07, 2007. - : IEEE conference proceedings. - 9783800730421
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Conference paper (other academic/artistic)abstract
- We propose two asynchronous optical packet switch architectures, with efficient contention resolution based on controllable optical buffers and tunable wavelength converters TWCs. Providing a few shared optical buffers significantly boosts the performance obtained by TWCs.
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| 24. |
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| 25. |
- Dai, Daoxin, et al.
(author)
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Gain enhancement in a hybrid plasmonic nano-waveguide with a low-index or high-index gain medium
- 2011
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In: Optics Express. - 1094-4087. ; 19:14, s. 12925-12936
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Journal article (peer-reviewed)abstract
- A theoretical investigation of a nano-scale hybrid plasmonic waveguide with a low-index as well as high-index gain medium is presented. The present hybrid plasmonic waveguide structure consists of a Si substrate, a buffer layer, a high-index dielectric rib, a low-index cladding, a low-index nano-slot, and an inverted metal rib. Due to the field enhancement in the nano-slot region, a gain enhancement is observed, i.e., the ratio partial derivative G/partial derivative g > 1, where g and G are the gains of the gain medium and the TM fundamental mode of the hybrid plasmonic waveguide, respectively. For a hybrid plasmonic waveguide with a core width of w(co) = 30nm and a slot height of h(slot) = 50nm, the intrinsic loss could be compensated when using a low-index medium with a moderate gain of 176dB/cm. When introducing the high-index gain medium for the hybrid plasmonic waveguide, a higher gain is obtained by choosing a wider core width. For the high-index gain case with h(slot) = 50nm and w(co) = 500nm, a gain of about 200dB/cm also suffices for the compensation of the intrinsic loss.
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