support a trench that penetrates the entire depth of the substrate thus for the purposes of this document a trench should be considered as a feature disposed proximate a waveguide having sufficient depth to attenuate one of the te and tm modes more than the other referring to fig4 a second embodiment of the invention is shown having a feature intended to substantially duplicate some of the effects of the trenches as described with reference to fig3 a 3 b and 3 c the waveguide structure of fig4 features a waveguide core having a periodically varying width in a region in which the waveguide core is narrow the waveguide is sufficiently narrow that the mode profiles of the lowest order te and tm modes are affected in a region where the width of the waveguide core is a maximum the waveguide core is sufficiently wide that the mode profiles of the lowerst order te and tm mode experience a different attenuation characteristic than in the narrow region optionally in the region where the waveguide core width is maximized the lower order te and tm mode are not substantially affected by the presence of the trench a person of skill in the art will appreciate that embodiments of the invention are useful for both active and passive waveguide structures although a wide variety of optical components will produce polarization dependent loss it is felt that the invention is particularly useful in compensating for polarization dependent loss in active optical components such as laser sources and optical amplifiers since a deep etching process is commonly used step in producing ridge waveguide structures the costs of providing polarization compensated components is minimal using the teaching of.