A Wavelength Converter Integrated with a Discretely Tunable Laser ...

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94 7. MZI wavelength converter Table 7.1: Simulated TE performance of the symmetric (50/50) MMI power coupler. MMI-1 var de value 100 1550 500 8.0 80.5 optimal tol 50 nm 50 nm 100 nm 0.2 0.2 -3.1 dB excess loss mode 0 in [dB] 0.014 0.033 0.15 0.053 0.002 -47.7 dB suppr. mode 1 in [dB] -43.4 -42.0 -43.7 -30.7 -46.7 Table 7.2: Simulated TE performance of the asymmetric (72/28) MMI power coupler. MMI-2 var de © mode 0 value 100 1550 500 10.0 392 optimal tol 50 nm 50 nm 100 nm 0.2 0.2 (on chip) -5.48 dB arm 1 0.27 0.66 0.38 1.0 0.00 -10.23 dB -1.46 dB arm 2 0.22 0.40 0.26 0.64 0.00 -12.65 dB Curved waveguide were shallowly etched for low propagation loss. The curvature of radius was designed to show radiation loss below ¤ dB/90 , which resulted in a 450 radius. Some of the wavelength converters on the chip were realized with high index contrast waveguide bends, having a 110 radius, as can be seen on the right side of Fig. 7.8. The fiber-chip coupling at the chip facet was done on 3.0 wide anti-reflection coated waveguides. The waveguides were perpendicularly oriented with respect to the facet and positioned at a pitch of 250 , which enabled fiber-chip coupling using a tapered-lensed fiber array. Electrical resistance between p-contacts Current may flow between the p-type contacts of SOAs and power monitors, if these contacts are connected with waveguides having p-doped cladding layers. The resistance between the contacts must be sufficient to prevent any significant current flow. The resistance between the p-contacts on the converter chips is estimated using the results from Sec. 4.4.2, where a cladding resistance of 1.7 M per millimeter waveguide length was found. This results in a calculated resistance of 0.5 M between the wavelength converter SOAs that are in parallel connected with two 650 long waveguides (Fig. 7.8). This resistance is much higher than the 7 resistance through the SOAs. In addition, the potential difference between the pcontacts of the SOAs is typically much smaller than that between the p-contact and the SOA ground contact. It can be concluded that the SOA p-contacts are well isolated from each other. Measurements of the resistance between the SOA p-contacts showed a cladding resistance over 200 k , which confirmed that the isolation is sufficiently high. The isolation between p-contacts of a SOA and a monitor lower, for the same length of interconnecting waveguide, because the resistance through the reverse biased monitor is high, M at ¨ V. In addition, the potential difference between the p-contacts is § V larger than that across the monitor. The distance on the chip, between SOA and a power monitor is 1750 , which gives rise to a cladding resistance of 2.8 M . This is an order of magnitude larger than the resistance of the monitor It can be concluded that the SOAs and monitors are are isolated sufficiently.
7.5 Fabrication 95 1 2 3 4 5 6 7 8 Fiber array CP 1 PP 1 CP 2 PP 2 Monitor Pre−amplifier MMI−1 650 μm SOA 1 MMI−1 SOA SOA 2 1750 μm MMI−2 InP chip Shallowly etched Deeply etched Figure 7.8: Layout of a wavelength converter with shallowly etched bends (top device) and deeply etched bends (bottom device). On the left side the eight fiber array is shown. 7.5 Fabrication The wavelength converter chip is based on active-passive integration in InGaAsP/InP. It was fabricated by applying a selective area growth technique using a three step Low-Pressure Metal-Organic Vapor Phase Epitaxy (LP-MOVPE) process. Five layers were grown in the first processing step: 500 nm thick InP buffer, 190 nm thick Q(1.25), 120 nm thick Q(1.55) bulk active material, 190 nm thick Q(1.25) and 200 nm thick InP. Next, the passive regions were defined by covering them with a SiO ¦ masking layer, while wet-chemically etching away the uncovered regions down to the bottom of the active layer. The active regions were butt-joined to Q(1.25) waveguide layers and a not intentionally doped InP layer [91]. Finally, a 1300 nm thick p-InP cladding layer and a 570 nm thick p-InGaAs contacting layer were grown. The waveguides were defined in a 100 nm thick SiN mask using photo-lithography. Then, a reactive ion etcher (RIE) etched the waveguide ridges down to 100 nm in the film layer. During a pause in the RIE etch, the SiN mask layer was removed from the passive regions to etch away the InGaAs contact layer. After the waveguide etch, all SiN was removed and a new 380 nm thick SiN passivation layer was deposited by PE-CVD. The SiN was removed from the top of the SOAs for the electrical contacts. The metal contacts were defined using a lift-off process and the metalization stack was deposited using a sputter process. Following the lift off, the chip was annealed in order to reduce the contact resistance and to make the contacts
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A Wavelength Converter Integrated w
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Contents v 4.3 Waveguide components
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Chapter 1 Introduction 1.1 Optical
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1.2 Exploiting optical fiber capaci
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1.3 Wavelength conversion in WDM ne
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Chapter 2 Wavelength converter over
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2.2 Optical gating 9 λcontrol λpr
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2.2 Optical gating 11 powers (in th
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2.2 Optical gating 13 Michelson Int
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2.3 Coherent wave mixing (FWM, DFG)
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2.5 Summary 17 2.5 Summary The main
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Chapter 3 Semiconductor optical amp
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3.2 Amplification in SOAs 21 Table
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3.3 Extended Cavity Lasers and exte
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Chapter 4 Integration of waveguide
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4.3 Waveguide components 41 Table 4
Page 49 and 50: 4.3 Waveguide components 43 4.3.2 P
Page 51 and 52: 4.4 Integration trade-offs 45 the a
Page 53 and 54: 4.4 Integration trade-offs 47 The c
Page 55 and 56: 4.4 Integration trade-offs 49 speed
Page 57 and 58: 4.4 Integration trade-offs 51 resis
Page 59 and 60: 4.4 Integration trade-offs 53 activ
Page 61 and 62: 4.4 Integration trade-offs 55 a) 60
Page 63 and 64: 4.4 Integration trade-offs 57 due t
Page 65 and 66: 4.4 Integration trade-offs 59 The
Page 67 and 68: 4.5 Conclusions 61 4.5 Conclusions
Page 69 and 70: Chapter 5 Technology 5.1 Introducti
Page 71 and 72: 5.2 Epitaxy 65 of the stack Q(1.25)
Page 73 and 74: 5.3 Waveguide processing 67 InP Q(1
Page 75 and 76: 5.3 Waveguide processing 69 h l h S
Page 77 and 78: 5.4 Contact openings and metalizati
Page 79 and 80: 5.4 Contact openings and metalizati
Page 81 and 82: Chapter 6 MWL with absolute wavelen
Page 83 and 84: 6.3 MWL with absolute wavelength co
Page 85 and 86: 6.3 MWL with absolute wavelength co
Page 87 and 88: 6.5 Measurements 81 facet M 1 O4 O3
Page 89 and 90: 6.5 Measurements 83 127 mA, which e
Page 91 and 92: Chapter 7 MZI wavelength converter
Page 93 and 94: 7.2 Operating principle of the MZI
Page 95 and 96: 7.3 Converter performance 89 Note t
Page 97 and 98: 7.3 Converter performance 91 Chirp
Page 99: 7.4 Wavelength converter design 93
Page 103 and 104: 7.6 Measurements 97 Power out [dBm]
Page 105 and 106: 7.6 Measurements 99 mental and firs
Page 107 and 108: 7.6 Measurements 101 fiber-to-fiber
Page 109 and 110: 7.6 Measurements 103 P out [dBm] P
Page 111 and 112: 7.6 Measurements 105 Power [dBm] -1
Page 113 and 114: 7.6 Measurements 107 Substituting E
Page 115 and 116: 7.6 Measurements 109 7.6.4 BER meas
Page 117 and 118: 7.7 Conclusion 111 output extinctio
Page 119 and 120: Chapter 8 Wavelength Converter inte
Page 121 and 122: 8.2 Design 115 MWL1 M1 O1 O2 O3 O4
Page 123 and 124: 8.4 Static measurements 117 Control
Page 125 and 126: 8.4 Static measurements 119 The LI-
Page 127 and 128: 8.5 Dynamic operation 121 BER 2.5 G
Page 129 and 130: 8.6 Discussion 123 Wavelength [μm]
Page 131 and 132: 8.6 Discussion 125 lower then the l
Page 133 and 134: 8.7 Conclusions 127 8.7 Conclusions
Page 135 and 136: Appendix A Mask plates The mask pla
Page 137 and 138: References [1] H. Takara, E. Yamada
Page 139 and 140: References 133 [24] R.G. Broeke, J.
Page 141 and 142: References 135 [51] C.Q. Xu, K. Shi
Page 143 and 144: References 137 [88] J.J.M. Binsma,
Page 145 and 146: Summary A wavelength converter inte
Page 147 and 148: Samenvatting Een golflengte omzette
Page 149 and 150: Dankwoord Een dankwoord hoort vol m
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echoduo een glas komen claimen, en
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List of Abbreviations AOWC All Opti
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Curriculum Vitae Ronald Broeke was
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List of publications 1. R.G. Broeke
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18. R.G. Broeke A Chirped phased-ar
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