Based on application, the refractive optical elements market is subsegmented into medicine (laser treatment), semiconductor manufacturing, lighting, laser material processing, fiber & waveguide coupler
, displays & projectors, metrology, LIDAR, and others.
The asymmetric multimode waveguide coupler
developed by Love and Henry  utilized the geometry size of the output branch to control the power splitting ratios.
To see the applicability of such a waveguide coupler
as a 3 dB coupler, this four-port coupler can be represented as a three-port matrix with one port short-circuited.
Prasad, "Optimization of waveguide coupler
for coupled-cavity TWT using artificial neural network," Proc.
The coordinates output by the Rotman lens software were combined with the WR22 waveguide coupler
to generate a full CAD of the Rotman lens.
These waveguide couplers
are used for signal sampling and other general purpose applications in wireless transmit/receive systems, satellite communications, radar systems, point-to-point backhaul and telecom.
They are made of two 50% coupling sections, exploiting two (Figure 1(a)) or three (Figure 1(b)) waveguide couplers
and of a phase shifter region in which a [pi] phase shift is achieved by plasma-optic effect in a forward biased p-i-n junction.