Ansys Lumerical Phased Array Lidar Simulations
Welcome to a series of videos where we will discuss how to use Lumerical to design a LIDAR. LIDAR stands for Light Detection and Ranging and, similar to its ancestor radar, can be used to detect faraway objects. LIDARs have become very popular in modern times for their applications in self-driving cars. In this series, we will be discussing LIDARs based on on-chip silicon antennas. Let's go ahead and get started.
Designing On-Chip Waveguide Antennas for LIDAR
Here we see the different steps involved in the design of on-chip waveguide antennas for LIDAR using Lumerical. The process involves multiple steps:
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Designing the Waveguides:
- Use Lumerical Mode to design the waveguides.
- Observe an array of corrugated waveguides, each carrying a waveguide mode.
- Due to perturbations in the waveguide, it scatters into free space, behaving like an antenna.
- Constructive or destructive interference from light scattered by these individual antennas gives rise to the beam shape.
- By changing the phase difference between light entering these waveguides, you can steer the beam in different directions.
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Using Mode Solutions:
- Calculate the refractive index of a particular lateral profile of a waveguide.
- Insert an eigensolver and run the calculation to determine the waveguide modes.
- The fundamental mode corresponds to the input wavelength of 1.55 microns, primarily a TE polarized mode.
- The waveguide mode is nicely confined within the cross-section of the waveguide.
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Optimization and Sweeps:
- Analyze how the effective index changes as you change the thickness of the waveguide cross-section.
- Use optimization sweeps to vary the width from 0.5 to 0.8 microns and extract the effective refractive index.
- Plot the results to visualize the relationship between waveguide width and effective refractive index.
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Coupling Analysis:
- Determine the optimal distance between waveguide antennas to prevent light coupling between them.
- Perform analysis for different cross-sections (0.5 microns and 0.8 microns).
- Calculate the length required for 10% of the light to couple from one waveguide to another.
- Use optimization sweeps to find the coupling length, ensuring interference occurs only in the far field.
Further Analysis
Once the waveguide design and coupling analysis are complete, we proceed with further analysis using FDTD numerical to examine the far-field plots.
Welcome to a series of videos where we will discuss how to use Lumerical to design a LIDAR. LIDAR stands for Light Detection and Ranging and is similar to its ancestor radar, used to detect far away objects. LIDARs have become very popular in modern times for their applications in self-driving cars.
In this series, we will be discussing LIDARs which will be based on on-chip silicon antennas. So, let's go ahead and get started. Here, we see the different steps involved in the design of on-chip waveguide antennas for LIDAR using Lumerical.
The first step is using Lumerical's mode solver to design the waveguides. Here, we see an array of corrugated waveguides, each carrying a waveguide mode. Due to perturbations in the waveguide, it scatters into free space and behaves like an antenna.
The constructive or destructive interference from the light scattered by these individual antennas gives rise to the beam shape. Depending on the phase difference between light going into these waveguides, we can achieve a beam shape in a particular direction.
By changing the value of the phase difference, you can steer the beam in different directions. For the first step, we need to design these waveguides. For that, we use mode solutions to calculate the refractive index of a particular lateral profile of a waveguide. Here, we have a waveguide.
A waveguide mode solver, such as the eigensolver, can be used to calculate the waveguide mode. Once this is known, we also have an idea of what the effective index is. The next step would be to see how the effective index changes as we change the thickness of the waveguide cross-section.
To do that, we go back to our original window and use optimizations and sweeps. Here, we have an optimization sweep which will sweep different values of the waveguide cross-section and calculate the effective refractive index of the fundamental waveguide mode.
The next important issue to discuss is how far apart two of these waveguide antennas can be placed without light coupling between them. We want each of these waveguide antennas to be independent, with interference only happening in the far field. This analysis can also be done using mode solutions.
Here, we consider the thin part of the cross-section, which is 0.5 microns, and send light to the first section, which is 0.85 microns away. We then vary the separation between them and see what length is required to couple 10% of the light inside the waveguide.
We do the same kind of analysis for the thicker part of the cross-section, which is 0.8 microns. Once we run these sweeps, we can obtain a plot showing what length of light is needed to couple from one waveguide to the other.
We decided to keep the length at around 1.5 to 1.6 microns, as this is the length needed for 10% of the light to couple from one waveguide to the other. We will continue with further analysis using FDTD numerical to look at how the far field plots look like.
