Electro-optic modulators (EOMs) are crucial devices for modern communication enabling high bandwidth optical communication links. Traveling wave electrodes are used to obtain high-speed modulation in these EOMs. We present the electrode design and analysis along with the study of effects of changing orientation on device performance for a thin-film lithium niobate tunable Mach–Zehnder interferometer (MZI) that offers sub-THz bandwidth operations. High velocity and impedance matching with low RF attenuation, high third-order SFDR (∼121 dB/Hz^2/3) and a low half-wave voltage length product (1.74 V.cm) have been achieved for a bandwidth of 136 GHz. High-speed digital modulation using multi-level signal formats (PAM-2, QAM-4 and QAM-16) with low BER for 400 Gbps data has been demonstrated to assess the digital performance of the device.

With the advances in on-chip photonic integrated circuits, compact and wide bandwidth mode converters are required for mode division multiplexing - demultiplexing and various other applications. We propose the design and theory for a highly compact, easy to fabricate mode converter that converts TE0 to TE1 and vice versa. The proposed design uses an arc bend waveguide structure based on Silicon on Insulator (SOI) platform and offers high mode conversion efficiency, low insertion loss, and large bandwidth of operation. We use coupled-mode theory to analyse the mode conversion within the structure, and FDTD simulations have been performed to verify the results. The mode conversion efficiency of 98.65% for TE0 to TE1 and 99.1% for TE1 to TE0 mode conversion with a device footprint of 10.5 um * 2 um is reported in this work.

Cost-effective and programmable photonic-driven solutions like electronic counterparts (FPGAs) can be implemented using waveguide mesh architectures along with tunable couplers for routing to implement general-purpose photonic processors. These processors/ networks are represented using undirected weighted graphs, where weights are included to implement constraints in the routing. Faster automated routing and cycle finding algorithms are crucial for dynamic path allocations in live networks to implement various functionalities using these processors. We propose path and cycle finding algorithms based on bidirectional and depth-first search techniques, considering various performance metrics for each device to optimize the path according to the required metric. Multiple cases of path distribution and implementation of cycles of various sizes have been demonstrated. Various methods to eliminate the non-functioning or malfunctioning units are proposed. The broad applicability of the proposed path-finding algorithm has been demonstrated using the same algorithm to create a list of all the possible input-output combinations in a 4*4 photonic switching network. A comparison of available search algorithms in terms of execution time and complexity has been described.