What parameter is significantly affected by the material and design of a VCSEL?

The design and material choices of a Vertical-Cavity Surface-Emitting Laser (VCSEL) play a crucial role in determining its beam divergence. Beam divergence refers to the angle at which the emitted light spreads as it propagates away from the output of the laser. This parameter is critical in applications where focused light is necessary.

Materials used in the VCSEL construction, such as the types of semiconductor materials and the layers used in the cavity design, directly influence how the optical modes are formed and how they propagate. Similarly, the cavity design, including the number of layers and their refractive indices, affects the spatial modes of the emitted light, leading to variations in beam shaping and divergence.

A well-designed VCSEL can achieve low divergence, which is advantageous for applications requiring precise beam positioning or tight focus, such as in optical communication systems. Conversely, poor design choices may lead to greater divergence, impacting performance in these applications.

Wavelength, intensity, and efficiency are indeed influenced by the materials used in a VCSEL, but they are not as directly impacted by design parameters in the same way that beam divergence is.