Edwin Jan Klein - Universiteit Twente

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Chapter 6 6.3 Characterization of single, vertically coupled microring resonators Apart from the resonator building block of which the design was described in the preceding section other vertically coupled microring resonators, with for instance a different radius or cladding thickness, have also been realized. In this section several measurements performed on these devices will be presented. These measurements were specifically chosen to illustrate certain important or interesting aspects in the design and application of the resonator: • The importance of phase matching and the ability to identify a misalignment of the resonator through extraction of the basic parameters from the resonator measurements. • The effect of cladding layer thickness on the heater efficiency and a method to improve the thermal tuning speed. First, however, the measurement setups used to perform these measurements will be discussed. 6.3.1 Measurement setup The lens setup shown in Figure 6.15 is mainly used for “difficult devices” i.e. those devices that are hard to couple into. This may for instance occur for experimental devices where no tapers have been added or in devices that have damage facets. By choosing the right input objective it is then often still possible to characterize the device. Figure 6.15. Measurement setup for the characterization of optical devices using lenses. For the characterization of a device first a HeNe laser is used to align the sample. A switch is then made to a Hewlett Packard 8168C tunable laser, with a maximum resolution of 1 pm, to perform the actual measurement. The light from the lasers is first polarized and then focused on the input facet of the devices using a 40x objective. The light at the output facet is collected using a 20x objective and focused 144
145 Microring-resonator building blocks on a 50 µm wide multi mode fiber. The light is then measured using a HP 81521B photo-detector. Aside from the measurements with the tunable laser this setup was also used in combination with a Sensors Unlimited 320 MX-1.7 RT infrared camera. The camera provides unique information that cannot be obtained through other means, e.g. by measuring the different ports of a device. Figure 6.16a and 6.16b for instance, show an infrared image of a cross coupled microring resonator. The orientation and heater placement in these images is similar to that of the resonator shown in Figure 6.3b. In Figure 6.16a the resonator is off-resonance. Most of the light propagates past the resonator to the through port and only a minor fraction of the light is coupled into the drop port. In In Through Drop Through Drop Figure 6.16. Infrared image (inverted) of a vertically coupled resonator in the off a) and onresonance b) state. In Figure 6.16b where the resonator is in the on-resonance state the reverse can be seen. Most of the light propagates through the resonator to the drop port and only a minor fraction of the light is present in the through port. Of special interest in this image is the “scatter” point that appears near the input (pointed to by the diagonal arrow). This point is only seen when the resonator is in resonance and is caused by light that radiates out of the resonator and then hits the port waveguide where it scatters to all directions. Another scatter point, seen in both images, is located at the crossing between the two waveguides. Although the lens setup is highly useful for the measurement of devices that would otherwise be difficult to characterize, the adjustment of the lenses to off-axis port waveguides, i.e. waveguides that are not in the same line from input to output, can be quite difficult. Also it is not possible to measure an output port that is on the same side as the input. In these cases or when devices are relatively easy to measure then it is useful to use a fiber setup as shown in Figure 6.17a. This setup can be equipped with single fibers or fiber arrays which are relatively easy to align to port waveguides, thereby speeding up the measurements. Also, the fiber arrays make it possible to measure ports that are on the same side of a device. Where possible small core fibers have been used to coupled light into the devices in order to reduce the fiber-chip coupling loss. The setup, of which a photograph is shown in Figure 6.17b, uses a HeNe laser for the alignment of the fibers to the port waveguides. Two laser sources have been used in this setup, depending on the resolution required. The previously mentioned tunable laser source in combination with the power meter is used for slow but high resolution measurements down to 1 pm. The Erbium Doped Fiber Amplifier with Amplified Spontaneous Emission Source (EDFA ASE) in combination with an Optical Spectrum Analyzer (OSA) on the other hand is used for near real-time measurements with a resolution down to 100 pm. On the input port of the device a
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DENSELY INTEGRATED MICRORING- RESON
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DENSELY INTEGRATED MICRORING- RESON
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To my parents…
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esonators is limited by the spacing
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iv Samenvatting Dit proefschrift be
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schakelaar “aan” is, dan is de
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3.6.2 Overlap loss reduction.......
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Chapter 1 Introduction The devices
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1.2 Broadband to the home 3 Introdu
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1.3 Bringing Fiber to the Home 5 In
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Figure 1.5. The technological scope
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9 Introduction these basic paramete
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Chapter 2 2.1 Introduction Integrat
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Chapter 2 light Icav2 in the cavity
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Chapter 2 ∆ = ⎛ β r − β g
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Chapter 2 2.3.3 Combined model The
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Chapter 2 FC 4µ 1µ 2 ⋅ χr = 2
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Chapter 2 P Through /P In (dB) 0 -1
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Chapter 2 The figure shows that it
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Chapter 2 In − jϕr1 2 Figure 2.1
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Chapter 2 differences between the f
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Chapter 2 M = ⋅ FSR = N ⋅ FSR F
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Chapter 2 the heat will therefore f
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Chapter 2 index. Although this can
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Chapter 2 resonators for instance h
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Chapter 2 a rather complex MEMS bas
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Chapter 3 3.1 Introduction The most
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Chapter 3 3.2.1 Drop port on-resona
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Chapter 3 3.2.3 Filter bandwidth In
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Chapter 3 (resulting in a higher ba
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Chapter 3 Figure 3.11. Residual cha
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Chapter 3 3.3 Geometrical design ch
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Chapter 3 resonator and the port wa
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Chapter 3 Another important fact wh
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Chapter 3 The flowchart of the desi
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Chapter 3 While the resonator in th
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Chapter 3 3.6.1 Port waveguide and
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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
Page 110 and 111: Chapter 4 Figure 4.21. The reflecto
Page 112 and 113: Chapter 4 P Drop /P In (dB) 0 -10 -
Page 114 and 115: Chapter 4 Figure 4.27a. OADM with r
Page 116 and 117: Chapter 4 will propagate through th
Page 118 and 119: Chapter 4 As demonstrated by these
Page 120 and 121: Chapter 4 What is more interesting
Page 122 and 123: Chapter 4 method it does allow time
Page 124 and 125: Chapter 4 complex than the interact
Page 126 and 127: Chapter 5 5.1 Introduction The mate
Page 128 and 129: Chapter 5 wafer is used (step 1). T
Page 130 and 131: Chapter 5 range of 0.9 to 1.1 µm.
Page 132 and 133: Chapter 5 The process flow with the
Page 134 and 135: Chapter 5 5.3.3 Mask layout The big
Page 136 and 137: Chapter 5 5.4. Fabrication and mask
Page 138 and 139: Chapter 5 1. Definition of the vert
Page 140 and 141: Chapter 5 5.4.2 Fabrication The fab
Page 142 and 143: Chapter 5 Figure 5.21. Process flow
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Page 146 and 147: Chapter 6 6.1 Introduction About ha
Page 148 and 149: Chapter 6 In early, comparatively s
Page 150 and 151: Chapter 6 that the TEOS has a very
Page 152 and 153: Chapter 6 The most important aspect
Page 154 and 155: Chapter 6 6.2.3 Chromium heater des
Page 156 and 157: Chapter 6 Therefore, even if the si
Page 158 and 159: Chapter 6 Next, the heater was heat
Page 162 and 163: Chapter 6 polarization maintaining
Page 164 and 165: Chapter 6 the resonators in this gr
Page 166 and 167: Chapter 6 Although the fitted coupl
Page 168 and 169: Chapter 6 a cladding thickness of 3
Page 170 and 171: Chapter 6 6.4 A wavelength selectiv
Page 172 and 173: Chapter 6 A possible explanation fo
Page 175 and 176: Chapter 7 Densely integrated device
Page 177 and 178: Densely integrated devices for WDM-
Page 183 and 184: 7.2.2 Spectral measurements Densely
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Page 191 and 192: 7.3.4 Characterization Densely inte
Page 195 and 196: Figure 7.31a. Eye pattern of the re
Page 197: Densely integrated devices for WDM-
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Page 202 and 203: Chapter 8 amount of power will be d
Page 204 and 205: Chapter 8 Another problem that may
Page 206 and 207: Chapter 8 halves that are each comp
Page 209 and 210: 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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