Increased tolerance polarization converters
An optical polarization converter device includes a first polarization converter section [ 1100 ] and a second polarization converter section [ 1102 ], which have mirror image cross-sections of each other and which are made of a common material and have orientation (i.e., tilt) errors equal in magnitude and opposite in sign. Preferably, one section has half, the other one and a half times the length of an original (single section, non-tolerant) polarization converter, i.e., the lengths of the two sections have a ratio of 1:3. Other embodiments include length ratios of 3:5 and 5:7. In addition to correcting fabrication errors, the polarization converter also corrects errors due to temperature and wavelength, improving the tolerance with respect to operational conditions.
1. An optical polarization converter device comprising:
a first polarization converter section, and a second polarization converter section;
wherein the first polarization converter section and second polarization converter section have mirror image cross-sections of each other;
wherein the first polarization converter section and second polarization converter section are made of a common material and have orientation/tilt errors equal in magnitude and opposite in sign;
wherein the first polarization converter section and second polarization converter section have lengths L 1 and L 2 , respectively, where L 1 =(M+0.5)L 0 , L 2 =(N+0.5)L 0 , |M−N|=2m+1, for non-negative integers M,N,m, where L 0 is a constant length.
2. The device of claim 1
wherein the first polarization converter section and second polarization converter section have lengths in the ratio of 1:3, 3:5, or 5:7.
3. The device of claim 1
wherein a phase shift error Δφ between modes after propagation along the constant length L 0 is less than 0.2 radians.
4. The device of claim 1
wherein the first polarization converter section and second polarization converter section have lengths L 1 (1+Δφ/2π) and L 2 (1+Δφ/2π), respectively, respectively, where L 1 =(M+0.5)L 0 , L 2 =(N+0.5)L 0 , |M−N|=2m+1, for non-negative integers M,N,m, and where Δφ is a constant.
5. The device of claim 4
wherein Δφ is less than 0.4 radians.
6. The device of claim 4
wherein Δφ is less than 0.566 radians.