If the question is in context of on-chip optical waveguide, answer is "likely no cladding". Some processes have polyimide coating over top silicon nitride, but polyimide option is uncommon.Sciencestd said:
Evanescent as long as beam angular diameter is much smaller than full reflection angle.Sciencestd said:
Narrow beams will produce only evanescent field above waveguide; unfocused (i.e. on-chip LED) will produce propagation modes above waveguide.Sciencestd said:
A silicon nitride waveguide is a type of optical waveguide used in the field of photonics. It is made of a thin layer of silicon nitride, a compound of silicon and nitrogen, and is used to guide and manipulate light for various applications such as telecommunications, sensing, and integrated optics.
The cladding in a silicon nitride waveguide is a layer of material that surrounds the core of the waveguide, which is made of silicon nitride. The cladding has a lower refractive index than the core, which helps to confine and guide the light within the core of the waveguide.
The cladding plays a crucial role in the performance of a silicon nitride waveguide. It helps to reduce the loss of light and improve the efficiency of the waveguide by confining the light within the core. It also helps to protect the core from external influences and provides mechanical support to the waveguide structure.
Using a silicon nitride waveguide with cladding offers several benefits. It allows for efficient light guiding, low loss of light, and high optical confinement. It also provides mechanical stability and protection to the waveguide, making it suitable for various applications in photonics and integrated optics.
While silicon nitride waveguides with cladding have many advantages, they also have some limitations. The fabrication process can be complex and expensive, and the waveguides are sensitive to temperature changes. Additionally, the cladding material must have a lower refractive index than the core, which limits the material choices for the cladding layer.