Design and characterization of InP based Mach-Zehnder modulators at 2μm wavelength

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Sadiq, Muhammad Usman
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University College Cork
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The Mach-Zehnder modulators (MZMs) based on InP are the key building blocks of photonic integrated circuits (PICs) due to low drive voltage and higher electro-optic (EO) bandwidth. They are the most suitable candidates to replace the widely deployed large footprint Lithium Niobate (LiNbO3) based MZMs. This thesis is focused on the design and development of travelling wave InP MZMs operating in the conventional optical C-band and also at 2000 nm which is one of the newly proposed possible alternatives for optical transmission to avoid highly anticipated ‘Capacity Crunch‘in the currently deployed standard single mode fiber (SSMF) in the next decade. InP MZMs working around the 1550 nm wavelength range were developed and characterised under DC and high frequency in order to validate the optimal electrode design. The highlight of presented work is the development of the first InP MZMs for operation around 2000 nm wavelengths for used in future optical transmission systems. To make the operation feasible around 2000 nm wavelength, compressively strained InGaAs QWs are used in the optical waveguide. The developed modulators exhibit a 3-dB EO bandwidth of 9 GHz with switching voltage as low as 3.2 V for a 3 mm long electrode. It is also shown that maximizing the electro-optical overlap by increasing the number of quantum wells can significantly reduce the Vπ, hence the modulator driving conditions for higher order modulation formats, without sacrificing the modulation bandwidth and device dimensions. Further, the devices are packaged using specially designed RF interposer to be used in an efficient, high-capacity WDM transmitter for communication over 1.15 km hollow-core photonic bandgap fiber (HC-PBGF) at 2 μm wavelength. A WDM capacity of 40 Gb/s is accomplished by using four 10 Gb/s NRZ-OOK externally modulated channels for the first time and transmission performance is evaluated using a direct detection receiver.
Mach Zehnder modulators , 2000 nm Modulators , InP based MZM , Photonic integrated circuits , 2000 nm modulators , Ramped quantum wells
Sadiq, M. U. 2016. Design and characterization of InP based Mach-Zehnder modulators at 2μm wavelength. PhD Thesis, University College Cork.
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