Loss due to Total Internal Reflection
Let us consider an emission where the light ray due to emission makes an angle θ with respect
to the normal to the interface and the angle of incidence is θi. When light travels from a denser
medium (of refractive index n1) to a rarer medium (of refractive index n2), for an angle of
incidence greater than the critical angle (θ = sinିଵ(nଶ/nଵ), total internal reflection occurs,
which implies that the emitted light is completely reflected back into the same medium. In our
case, the critical angle (θ
) is sinିଵ(1/nଵ).
Thus, when the angle of incidence θi is greater than a critical angle θ
, the emitted light is not
available at the output of the device. If we consider the source of emission as a point source, it
may emit in all possible directions, but only a fraction of this is available outside the device.
The output is available in the cone of half-angle which corresponds to θ
Log in to save your progress and obtain a certificate in Alison’s free Understanding Optical Sources in Fiber Optic Communication online course
Sign up to save your progress and obtain a certificate in Alison’s free Understanding Optical Sources in Fiber Optic Communication online course
Please enter you email address and we will mail you a link to reset your password.