Polarization-maintaining photonic crystal fiber

1. A polarization-maintaining photonic crystal fiber comprising:

an elongated guiding core; and

an elongated photonic crystal cladding surrounding the core;

wherein:

a cross-sectional area of the fiber taken orthogonally to a fiber longitudinal axis of the fiber characterized by an x-axis and a y-axis, the x-axis orthogonal to the y-axis, the x-axis and the y-axis orthogonal to the fiber longitudinal axis;

the cross-sectional area of the fiber defines a collection of groups of elongated holes located in the cladding, each hole in the collection having a hole longitudinal axis that is parallel to the fiber longitudinal axis, the collection of groups comprising a first group [1], a second group [2], a third group [3], and a fourth group [4], the first group [1] and third group [3] defining an opposing first pair, the second group [2] and fourth group [4] defining an opposing second pair;

the first group [1] and the third group [3] are symmetrical with each other with respect to the x-axis or the y-axis;

a first plurality [1A] of the holes in the first group [1] have a first adjacent-hole centerpoint distance [1AP] and a first common dimension [1AD];

the second group [2] and the fourth group [4] are symmetrical with each other with respect to the x-axis or the y-axis;

a first plurality [2A] of the holes in the second group [2] have a first adjacent-hole centerpoint distance [2AP] and a first common dimension [2AD]; and

a difference in the first adjacent-hole centerpoint distance [1AP] and the first dimension [1AD] of the first plurality [1A] of the holes in the first group [1] with respect to the first adjacent-hole centerpoint distance [2AP] and the first common dimension [2AD] of the first plurality [2A] of the holes in the second group [2] is configured to generate a predetermined birefringence in the polarization-maintaining photonic crystal fiber.

2. The polarization-maintaining photonic crystal fiber of claim 1 , wherein the fiber is single mode.

3. The polarization-maintaining photonic crystal fiber of claim 1 , wherein a guided mode of the fiber has a circularity (short radius/long radius) of greater than 0.95.

4. The polarization-maintaining photonic crystal fiber of claim 1 , wherein the birefringence is greater than 10 −5 .

5. The polarization-maintaining photonic crystal fiber of claim 1 , wherein a transmission loss of the fiber is less than 1000 dB/km.

6. The polarization-maintaining photonic crystal fiber of claim 1 , wherein the holes of the groups of the collection have any of a variety of closed shapes.

7. The polarization-maintaining photonic crystal fiber of claim 1 , wherein the collection of groups comprises a fifth group of elongated holes having a different common dimension than the respective common dimensions of the holes of the first group, second group, third group, or fourth group, the fifth group surrounding the opposing first pair and/or the opposing second pair, the fifth group configured to decrease a leakage loss of the fiber.

8. The polarization-maintaining photonic crystal fiber of claim 1 , wherein the collection of groups comprises a fifth group of elongated holes having a different adjacent-hole centerpoint distance than the holes of the first group, second group, third group, or fourth group, the fifth group surrounding the opposing first pair and/or the opposing second pair, the fifth group configured to decrease a leakage loss of the fiber.

9. The polarization-maintaining photonic crystal fiber of claim 1 , wherein the fiber is made of a single glass material.

10. The polarization-maintaining photonic crystal fiber of claim 1 , wherein the fiber is made of a soft glass having a melting temperature of less than 800C.

11. The polarization-maintaining photonic crystal fiber of claim 1 , wherein the x-axis and y-axis define four Cartesian quadrants comprising a first quadrant, a second quadrant, a third quadrant, and a fourth quadrant, each of the four Cartesian quadrants including a corresponding plurality of quadrant holes, the quadrant holes of the first quadrant symmetrical about the y-axis with the quadrant holes of the second quadrant, the quadrant holes of the second quadrant symmetrical about the x-axis with the quadrant holes of the third quadrant, and the quadrant holes of the third quadrant symmetrical about the y-axis with the quadrant holes of the fourth quadrant.

12. The polarization-maintaining photonic crystal fiber of claim 1 , wherein a second plurality of holes in the first group have a second adjacent-hole centerpoint distance and/or a second common dimension, the first adjacent-hole centerpoint distance of the first group differing from the second adjacent-hole centerpoint distance of the first group and/or the first common dimension of the first group differing from the second common dimension of the first group.

13. The polarization-maintaining photonic crystal fiber of claim 1 , wherein a second plurality of holes in the second group have a second adjacent-hole centerpoint distance and/or a second common dimension, the first adjacent-hole centerpoint distance of the second group differing from the second adjacent-hole centerpoint distance of the second group and/or the first common dimension of the second group differing from the second common dimension of the second group.

14. The polarization-maintaining photonic crystal fiber of claim 1 , wherein a second plurality of holes in the first group have a shape that differs from a shape of the first plurality of holes in the first group.

15. The polarization-maintaining photonic crystal fiber of claim 1 , wherein, with respect to the x-axis and/or the y-axis, a second plurality of holes in the first group have an orientation that differs from an orientation of the first plurality of holes in the first group.

16. A system comprising the polarization-maintaining photonic crystal fiber of claim 1 , wherein the system is selected from the group consisting of:

a LIDAR (Light Detection and Ranging) system;

a LADAR (Laser Detection and Ranging) system;

an advanced driver assistance system (ADAS);

a medical laser system;

a chemical sensor system;

a spectroscopy system;

a broadband laser beam delivery system; and

a mid-infrared transmission system.