Edwin Jan Klein - Universiteit Twente

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Chapter 2 2.1 Introduction Integrated optic microring resonators were first proposed by Marcatili in 1969 [15]. These resonators find their origin in the field of fiber optic ring resonators [16, 17] and micrometer sized resonant spheres and droplets [18-20]. These resonators are, like the Fabry-Perot resonator (FP), a class of resonant filters that, due to internal optical feedback, achieve high frequency selectivity. Functionally these resonators behave similar to the Fabry-Perot resonator and share its Lorentzian-like frequency response. The integrated optic microring-resonator, however, has the linear cavity of the FP replaced by a loop waveguide and the cavity mirrors replaced by a directional coupler or, occasionally, a Multi Mode Interferometer (MMI). In an integrated optics FP the cavity the mirrors are commonly created using cleaved facets or reflective gratings, both of which are difficult to integrate when produced on a large scale. However, the use of directional couplers in a microring resonator allows, depending on the index contrast, ring radii as small as a few micrometers [21, 22]. The microring-resonator is therefore a highly attractive component for Large Scale Integrated Optics (LSIO) [23-26]. In addition, by careful design of the resonator geometry and choice of the materials system it can be made to perform a wide range of functions. Aside from its use as a highly selective passive filter the microring resonator has seen application as an optical delay line element, a dispersion compensator and even as a highly sensitive sensor [27-30]. Using electrooptic polymers or materials such as silicon-on-insulator (SOI), Gallium-Arsenide (GaAs) and Indium-Phosphide (InP) high speed modulators can be created [31-36] and also microring-resonator lasers [37-42] have been demonstrated. 2.2 Operational description Most integrated optics microring resonators operate as either a two or a four port device. In a two-port resonator the resonant cavity is coupled to a single port waveguide and therefore has only a single in and output, as shown in Figure 2.1a. This type of resonator is ideally suited as a dispersive or attenuating element and has been used in dispersion compensation [43, 44] and true-time-delay [45] applications. The two port configuration can also be used for making lasers [37, 41] and sensors [27-29]. It is, however, less useful as a wavelength filtering element in the applications described in this thesis and is therefore not further covered. In Out In 1 Figure 2.1a. Two port ring resonator. Figure 2.1b. Four port ring resonator. Conversely, the four port configuration is ideal for this task. Used throughout this thesis the four port configuration, shown in Figure 2.1b, is created by adding an additional port waveguide to the two-port resonator. This effectively transforms the micro-resonator into a wavelength selective filter that allows signals of certain wavelengths to be transferred from one port waveguide to the other. 12 Out 2 In 2 Out 1
2.2.1 Four port filter operation 13 The Micro-Resonator The transfer of power between the two port waveguides of a four port micro-resonator is only possible at discrete wavelength regions at which the optical path length of the light in the resonator is an integer multiple of its effective wavelength. The process by which power is transferred through the resonator is characterized by three distinct phases: the initial, transient and the equilibrium phase. In the initial phase, shown in Figure 2.2a, incoming light Iin of a certain wavelength propagates along one of the port waveguides of the micro-resonator. When the light 2 reaches the first coupler a small power fraction κ 1 ⋅ Iin is evanescently coupled into the resonator. Most of the light, however, will continue its path along the port waveguide as Ithrough The light Icav1 that is now in the resonator will propagate along the resonator until it reaches the other port waveguide and the second coupler. Here a 2 small fraction κ 2 ⋅ Icav1 of the light is coupled out of the resonator as Idrop while the larger fraction Icav2 continues its roundtrip towards the first coupler. In the transient phase the dominant factor that determines the buildup of power the resonator is the modal phase of the light Icav2 as it interferes with the light in the port waveguide at the first coupler. If the resonance condition: ϕ r = m ⋅ 2π , m ∈ Ν (2.1) is satisfied for the roundtrip phase of Icav2, constructive interference will occur at the resonator side of the first coupler, resulting in a net increase of power within the resonator. At the same time destructive interference at the port waveguide side results in a decrease of the power Ithrough, as shown in Figure 2.2b. Icav2 = 2 Icav1 − κ 2 ⋅ Icav1 Idrop Iin κ ⋅ I 2 κ 1 2 2 cav1 ⋅ I in Icav1 = 2 κ1 ⋅ Iin Ithrough = Iin − ⋅ Iin 2 κ 1 Figure 2.2a. Light coupling into the microresonator in the initial phase. Power (a.u.) 4 3 2 1 0 Interference after first roundtrip results in an increase in Icav and a decrease in IThrough I Cav1 IThrough 0 10 20 30 40 50 60 Time (a.u) Figure 2.2b. Constructive interference at the first coupler results in a build-up of power in the resonator while reducing the power IThrough. The process of power enhancement within the cavity while transferring more power from Iin will repeat itself many times as Icav2 continues to interfere with the light in the port waveguide on every roundtrip. In tandem the dropped power Idrop will also 2 increase according to I drop = κ 2 ⋅ I cav1. The intra-cavity power cannot rise indefinitely, however, and at a certain power level a state of equilibrium is reached between the
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Page 25: 9 Introduction these basic paramete
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Chapter 3 overlap losses are only 0
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Chapter 3 3.7 Component design cons
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Chapter 3 By maximizing the power t
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Chapter 3 important, due to the fac
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Chapter 4 4.1 Introduction As was s
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Chapter 4 4.2.1 Transient response
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Chapter 4 Under the condition that
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Chapter 4 Figure 4.4. Screenshot of
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Chapter 4 The equations required to
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Chapter 4 using an approach based o
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Chapter 4 4.5.1 Architecture The Au
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Chapter 4 4.5.2 Simulation method A
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Chapter 4 Figure 4.9. A Primitive w
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Chapter 4 Listing 4.3. Pseudo code
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Chapter 4 Listing 4.4. Pseudo code
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Chapter 4 simulated output spectra
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Chapter 4 Figure 4.21. The reflecto
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Chapter 4 P Drop /P In (dB) 0 -10 -
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Chapter 4 Figure 4.27a. OADM with r
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Chapter 4 will propagate through th
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Chapter 4 As demonstrated by these
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Chapter 4 What is more interesting
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Chapter 4 method it does allow time
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Chapter 4 complex than the interact
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Chapter 5 5.1 Introduction The mate
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Chapter 5 wafer is used (step 1). T
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Chapter 5 range of 0.9 to 1.1 µm.
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Chapter 5 The process flow with the
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Chapter 5 5.3.3 Mask layout The big
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Chapter 5 5.4. Fabrication and mask
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Chapter 5 1. Definition of the vert
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Chapter 5 5.4.2 Fabrication The fab
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Chapter 5 Figure 5.21. Process flow
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Chapter 5 removed using lift-off of
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Chapter 6 6.1 Introduction About ha
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Chapter 6 In early, comparatively s
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Chapter 6 that the TEOS has a very
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Chapter 6 The most important aspect
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Chapter 6 6.2.3 Chromium heater des
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Chapter 6 Therefore, even if the si
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Chapter 6 Next, the heater was heat
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Chapter 6 6.3 Characterization of s
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Chapter 6 polarization maintaining
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Chapter 6 the resonators in this gr
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Chapter 6 Although the fitted coupl
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Chapter 6 a cladding thickness of 3
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Chapter 6 6.4 A wavelength selectiv
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Chapter 6 A possible explanation fo
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Chapter 7 Densely integrated device
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Densely integrated devices for WDM-
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7.2.2 Spectral measurements Densely
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Power Densely integrated devices fo
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7.3.4 Characterization Densely inte
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Figure 7.31a. Eye pattern of the re
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Chapter 8 8.1 Introduction In most
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Chapter 8 amount of power will be d
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Chapter 8 Another problem that may
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Chapter 8 halves that are each comp
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Chapter 9 Discussion and Conclusion
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Appendix A. Mason’s rule Several
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Appendix B. Crosstalk Derivation Th
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List of Acronyms ADSL - Asymmetric
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List of Symbols Q - Quality Factor
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Bibliography [1] Dan Schiller, “E
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Regions,” IEEE Photonics Technolo
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[66] B. E. Little, S. T. Chu, J. V.
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[97] H. Haeiwa, T. Naganawa and Y.
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[135] A. Driessen, D. H. Geuzebroek
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[165] T. Barwicz, M. R. Watts, M. A
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Publication List Patents (pending)
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R. Dekker, L.T.H.Hilderink, M.B.J.
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Networks (BB Photonics),” Interna
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Dankwoord/Acknowledgements Zo, dit
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Edwin Jan Klein - Universiteit Twente

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