Simulating and understanding Convex and Concave Lenses

Convex and concave lenses form the basis of Ray optics. Convex lens converges the light rays and concave lenses diverge the light rays. But how does the wave picture of light rays look? This post is dedicated to design your own lens of different radii and shape and study its property in MEEP FDTD.

(note: I'm assuming you have basic knowledge about MEEP FDTD. If not, you can first see some of my previous posts about MEEP( In any case if you are stuck, feel free to contact me!)

Convex lens:

The shape of convex lens is the common region of two intersecting circles. But it is impossible to create the shape directly. The only option is to follow this method ( . Convex lenses are characterized by radius of both sides, and refractive index. The trick here is, chose the center of respective circles, and define the points in the intersection. You can select the points with the help of polar coordinates. After defining them convert them to Cartesian coordinates in terms of radius, sine and cosine. Now that you have your points, go ahead and create your structure and run your simulation. In your simulation units, its better to chose your unit as centimeters.

Concave Lens:

Concave lens is relatively very easy. Describe 3 structures. Two non intersecting circles and a rectangular block in between. Define the refractive index of the lens in the block and air for the circles. (Note: Define the block first, followed by the circles). You have your desired lens. In my simulation, I have changed the property of the source, so that maximum amount of light travels along the axis of the lens, in order to observe a good diverging effect.


9 thoughts on “Simulating and understanding Convex and Concave Lenses

  1. My relatives every time say that I am wasting my time here at web, however I know I am getting know-how every day by reading such pleasant articles or reviews.

  2. Hi bro, just give me light on the different light simulation software that's available today. How's the package different? which one is best for research level like micro, nano-structures of photonic devices. What do you think about Multi-physics software?

    1. Hi Velu,
      Broadly light simulation softwares can classified based on the solving methods, viz FDTD and FEM. COMSOL Multi Physics solves problems based on FEM, while Lumerical, MEEP and other softwares are based on FDTD method. For the purpose of nano-structure (and not micro) softwares based on FDTD do a good job. Multi-Physics software does a pretty good job in integrating every aspect of a Photonic device. Hope this helps. Do you have any specific question in mind?

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