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Hasan Alper Gunes

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Proceedings Article | 26 May 2022 Poster + Presentation + Paper

Genetic algorithm based, on-chip, fishbone grating waveguide and transition design for time-domain operation

Ahmet Sakin, Hasan Gunes, Hamza Kurt, Mehmet Unlu

Proceedings Volume 12148, 121480J (2022) https://doi.org/10.1117/12.2622120

KEYWORDS: Waveguides, Dispersion, Optical design, Planar waveguides, Cladding, Genetic algorithms

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The limited bandwidth of conventional phase-shifter-based antenna arrays, which is caused by steering in different angles at different frequencies named as the beam-squint effect, is a problem that should be taken into consideration for the ultrawide band systems. To overcome this problem, designing optical true time delay (TTD) lines for the antenna arrays is crucial for the development of next-generation, wideband communication, and imaging systems, which employ short pulses for wideband operation. One of the important problems for employing such short pulses is the dispersion during the propagation along the on-chip optical waveguides, which cause the distortion in the pulse shape and decrease in the amplitude of the pulse. Therefore, we propose a one-dimensional (1D) fishbone grating waveguide with a “Lego” type of step taper on silicon-on-insulator (SOI) substrate, both of which are designed for time-domain operation. The designed grating waveguide/taper pair is excited by a pulsed Gaussian light source, having a FWHM of 90 fs at a center wavelength of 1550 nm, where we investigate the possibility of controlling the dispersion by using SiO2 cladding modulation and taper structure optimization using genetic algorithm. The simulation results show that it is possible to decrease the dispersion in terms of the amplitude of the pulse up to 85%. The simulation results also show that the coupling efficiency from the taper to the waveguide can be increased up to 73%, which also decrease the dispersion of the pulse significantly. The simulated bandwidth of the grating waveguide/taper pair is found to be 56 nm, which allows ultrawide band operation.

Proceedings Article | 26 May 2022 Presentation + Paper

A fiber-to-waveguide, 1D grating coupler design using genetic algorithm for 1550 nm applications

Beyza Akcay, Hasan Alper Gunes, Hamza Kurt, Mehmet Unlu

Proceedings Volume 12148, 121480C (2022) https://doi.org/10.1117/12.2621844

KEYWORDS: Optical design, Waveguides, Genetic algorithms, Silicon, Particle swarm optimization, Finite-difference time-domain method, Fiber couplers

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Silicon photonics on silicon-on-insulator (SOI) technology has great potential in the integrated photonics field. Propagation modes are mostly confined within Silicon waveguides because of the high refraction index difference between silicon waveguide and silicon dioxide cladding. Nowadays, couplers designed using this special feature of SOI are in demand. Edge coupler and grating coupler are the two most preferred coupler types for coupling light between integrated photonic circuits and single-mode optical fibers. In this work, we focused on grating couplers to couple light from fiber to horizontal waveguide since their advantages are easy fiber alignment, lower cost, compact design, and more possible optic inputs/outputs. However, in the literature, the fabrication process of grating couplers with high coupling efficiency is complicated. Therefore, in this paper, we are proposing a grating coupler design with standard SOI lithography technology with a minimum feature size of 250 nm. In our research, the finite difference time domain (FDTD) method is utilized to analyze and design the grating coupler structure with a center of 1.55 μm. We used a genetic algorithm (GA) and particle swarm optimization (PSO) to optimize grating coupler features. SiO₂ cladding thickness, SiO₂ buried oxide layer thickness, grating widths, and fiber distance from grating couplers are optimized with these optimization processes. Our design is an apodized grating coupler with a -3.29 dB (46.8%) coupling efficiency and a 3 dB bandwidth of 78 nm. The design layer of the grating coupler is 12 μm × 16 μm.

Proceedings Article | 26 May 2022 Poster + Presentation + Paper

Waveguide-to-substrate, vertical bend coupler design for 3D photonic integrated circuits

Hasan Gunes, Hamza Kurt, Mehmet Unlu

Proceedings Volume 12148, 121480K (2022) https://doi.org/10.1117/12.2622038

KEYWORDS: Photonic integrated circuits, Waveguides, Silicon, Genetic algorithms, Integrated circuit design

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A waveguide-to-substrate, vertical bend coupler that is based on genetic algorithm is introduced to couple and direct the optical flow in 3D photonic integrated circuits. The vertical coupler device enables high-efficiency broadband optical transmission between different dielectric layers over comparable distances to the coupler’s length. The vertical coupler attains an adept transition between a silicon waveguide and a planar Si layer separated by a SiO₂ spacer. The simulation results of the designed vertical coupler device show a coupling ratio of -3.4 dB at 1550 nm wavelength and at 1 μm vertical transition depth, thanks to the effective manipulation of light. The coupler possesses a miniscule area of 2 μm × 2 μm compared to its conventional counterparts. Our proposed waveguide-to-substrate coupler represents an unprecedented, elevated solution with high-efficiency and broadband operation for the vertical transition in 3D photonic integrated circuits. It can take an important part in overcoming the obstacles on the way of 3D photonic integrated circuits for virtual reality and quantum computing applications.

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