各向异性透明晶体如方解石、石英等的折射率，是其固有的特性，称为永久双折射。

For optical fibers as well as other waveguides, it is much more ideal to take into account the difference of successful refractive indices. That is straight connected with the primary difference in imaginary values from the propagation constants.

For propagation alongside the optical axis, the electric subject can only be perpendicular to that axis, making sure that one obtains the everyday index for just about any polarization way. In that predicament, no birefringence is knowledgeable.

If waves with different polarization directions propagate with each other in the waveguide, their period relation is restored right after integer multiples in the propagation beat duration.

This effect can seriously limit the efficiency of nonlinear frequency conversion processes, specially when making use of tightly targeted laser beams.

Equally, the polarization point out of the laser beam inside a laser crystal with thermally induced birefringence is distorted. The sort of distortion depends on the placement, Because the birefringent axis includes a various (e.

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文献中，双折射通常包含两种不同的含义。经典光学中，就是下面所说的双折射（double refraction）。

For bulk optical products, It is additionally common to take into consideration the difference of refractive indices for the two polarization directions. The bigger that variation, the much larger the attained retardance for every millimeter of propagation length.

Straight optical fibers are frequently nominally symmetric, but Nonetheless exhibit some tiny degree of random birefringence as a consequence of tiny deviations from fantastic symmetry �?for instance as a consequence of bending, other mechanical worry or little microscopic irregularities.

Quantitative Evaluation of the interference colours observed in birefringent samples will likely be accomplished by consulting a Michel-Levy chart comparable to the one particular illustrated in Figure nine. As is apparent from this graph, the polarization colours visualized during the microscope and recorded onto movie or captured digitally may be correlated with the actual retardation, thickness, and birefringence of the specimen. The chart is relatively convenient to use with birefringent samples if two from the 3 expected variables are identified. In the event the specimen is positioned amongst crossed polarizers from the microscope and rotated to a placement of maximum brightness with Anybody of many different retardation plates, the colour visualized while in the eyepieces is often traced over the retardation axis to find the wavelength difference between the everyday and incredible waves passing in the specimen.

当光束在双折射晶体表面发生折射是，折射角与偏振方向有关。这样非偏振光束在非垂直入射到材料中的情况下分为两个线性偏振的光（双折射）。当非偏振光射向一个物体，如果采用双折射晶体看该物体，会出现两个像。 

Quite a few microscope producers take advantage of this sensitivity by offering a full-wave retardation plate or 1st-get pink compensator with their polarizing microscopes to assist scientists in analyzing the Qualities of birefringent elements.

In laser know-how and nonlinear optics, the phenomenon of birefringence happens mainly from the read more context of non-isotropic crystals:

Alternatively, the extraordinary wave deviates to the still left and travels with the electric vector perpendicular to that with the regular wave. For the reason that calcite is actually a negatively birefringent crystal, the normal wave will be the gradual wave and also the incredible wave could be the quick wave.