Integrated optical, wavelength selective, acoustically tunable 2×2 switches (add-drop multiplexers) in LiNbO/sub 3/

Passive polarization converter in SiON technology

“…If the existence of modes of both polarizations poses a problem to a given integrated optical device, there are two ways to eliminate it. One is the realization of polarization-independent devices [3], thereby posing severe limitation/requirements to both the design and technology. Another is the implementation of polarization manipulating functionalities in the devices, such as a polarization converter [4], which enables transfer of optical power from one state of polarization to the other and vice versa.…”

“…Both active [3] and passive [4] converters have been reported in literature. Here, active refers to the use of physical cross effects for inducing the grating that is needed for obtaining polarization conversion.…”

“…Here, active refers to the use of physical cross effects for inducing the grating that is needed for obtaining polarization conversion. Active converters have the advantage that the amount of conversion can be controlled by changing the driving power, while in the optoacoustic case, also the grating period can be adjusted [3]. However, the use of most of the active converters reported up to now [3], [5] is limited by the need for (expensive) materials, which should show physical cross effects (such as electrooptical or acoustooptical) and should have a crystal structure with a symmetry that permits coupling between both types of polarization.…”

“…Active converters have the advantage that the amount of conversion can be controlled by changing the driving power, while in the optoacoustic case, also the grating period can be adjusted [3]. However, the use of most of the active converters reported up to now [3], [5] is limited by the need for (expensive) materials, which should show physical cross effects (such as electrooptical or acoustooptical) and should have a crystal structure with a symmetry that permits coupling between both types of polarization. In the case of acoustooptical devices, an additional drawback is the use of high-frequency control electronics [3], which limits low-cost commercial application of these devices.…”

“…However, the use of most of the active converters reported up to now [3], [5] is limited by the need for (expensive) materials, which should show physical cross effects (such as electrooptical or acoustooptical) and should have a crystal structure with a symmetry that permits coupling between both types of polarization. In the case of acoustooptical devices, an additional drawback is the use of high-frequency control electronics [3], which limits low-cost commercial application of these devices. Contrary to active converters, in passive converters there are fewer restrictions with respect to the materials used and, in general, a much simpler fabrication technology is possible.…”