Bent taper and polarization rotator

Abstract

A bent taper is provided that includes one or more waveguide bends, at least one of which has a tapering waveguide width along at least a portion thereof. In one embodiment, the bent taper is an S-shaped bent taper that is configured as a TE 0 -TE 1 mode convertor. Such a bent taper can be combined with a linear bi-layer taper configured as a TM 0 -TE 1 mode converter to form a TM 0 -TE 0 polarization rotator.

1 - 22 . (canceled) 
     
     
         23 . A waveguide test structure comprising:
 a substrate;   a pair of waveguide mode converters supported by the substrate, the pair of waveguide mode converters comprising:
 a first waveguide mode converter supported by the substrate and configured for converting between a first optical mode and a second optical mode, the first waveguide mode converter comprising a first port configured for coupling the first optical mode, and a second port configured for coupling the second optical mode; and, 
 a second waveguide mode converter supported by the substrate and configured for converting between the first optical mode and the second optical mode, the first waveguide mode converter comprising a first port configured for coupling the first optical mode, and a second port configured for coupling the second optical mode; 
   wherein the second port of the first waveguide mode converter is optically coupled to the second port of the second waveguide mode converter so that the first waveguide mode converter and the second waveguide mode converter are optically connected in series.   
     
     
         24 . The waveguide test structure of  claim 23  further comprising a first test port optically coupled to the first port of the first waveguide mode converter, and a second test port optically coupled to the first port of the second waveguide mode converter. 
     
     
         25 . The waveguide test structure of  claim 24  wherein at least one of the first test port or the second test port comprises a vertical coupler. 
     
     
         26 . The waveguide test structure of  claim 23  wherein the first optical mode is a TE mode, the second optical mode is a TM mode. 
     
     
         27 . The waveguide test structure of  claim 23  wherein the first optical mode is a fundamental TE mode and the second optical mode is a higher-order TE mode. 
     
     
         28 . A wafer comprising two or more instances of the pair of waveguide mode converters of  claim 23  optically connected in series between a first test port and a second test port. 
     
     
         29 . The waveguide test structure of  claim 23  wherein the first waveguide mode converter comprises a bent waveguide taper. 
     
     
         30 . The waveguide test structure of  claim 29  wherein the bent waveguide taper comprises two bent waveguide segments of opposite curvature. 
     
     
         31 . The waveguide test structure of  claim 30  wherein the two bent waveguide segments comprise a first bent waveguide segment and a second bent waveguide segment optically connected in series, and wherein the first bent waveguide segment increases in width in a direction toward the second bent waveguide segment. 
     
     
         32 . The waveguide test structure of  claim 29  wherein the bent waveguide taper is configured to convert a fundamental TE mode to a higher-order TE mode. 
     
     
         33 . The waveguide test structure of  claim 32  wherein the first waveguide mode converter further comprises a TE to TM mode converter configured to convert the higher-order TE mode to the fundamental TE mode. 
     
     
         34 . The waveguide test structure of  claim 32  wherein the TE to TM mode converter comprises a bilayer taper. 
     
     
         35 . The waveguide test structure of  claim 23  wherein the first waveguide mode converter comprises a bent waveguide taper. 
     
     
         36 . The waveguide test structure of  claim 23  wherein each of the first waveguide mode converter and the second waveguide mode converter comprises a bent waveguide taper. 
     
     
         37 . The waveguide test structure of  claim 36  wherein each of the bent waveguide tapers comprises two bent waveguide segments of opposite curvature. 
     
     
         38 . The waveguide test structure of  claim 37  wherein the two bent waveguide segments comprise a first bent waveguide segment and a second bent waveguide segment optically connected in series, and wherein the first bent waveguide segment increases in width in a direction toward the second bent waveguide segment. 
     
     
         39 . The waveguide test structure of  claim 36  wherein each of the bent waveguide tapers is configured to convert a fundamental TE mode to a higher-order TE mode. 
     
     
         40 . The waveguide test structure of  claim 39  wherein each of the first waveguide mode converter and the second waveguide mode converter further comprises a TE to TM mode converter configured to convert the higher-order TE mode to the fundamental TE mode. 
     
     
         41 . The waveguide test structure of  claim 40  wherein the TE to TM mode converter comprises a bilayer taper. 
     
     
         42 . A wafer comprising:
 one or more waveguide test structures, the one or more waveguide test structures comprising:   a first test port;   a second test port; and,   a waveguide mode converter optically connected between the first test port and the second test port, the waveguide mode converter configured for converting between a first optical mode and a second optical mode;   wherein each of the first test port and the second test port is configured to preferentially couple in the waveguide mode converter or out of the waveguide mode converter the same one of the first optical mode or the second optical mode.