OPTICAL MULTILAYER WITH BARRIER LAYER
A multilayer architecture includes an amorphous optical layer, a crystalline optical layer overlying the amorphous optical layer, and a barrier layer located between the amorphous optical layer and the crystalline optical layer. The barrier layer may be configured to mediate the structure of the later-formed amorphous optical layer. For instance, a low absorption barrier layer may be formed over the crystalline optical layer within the multilayer architecture and accordingly inhibit crystallization within a subsequently formed optical layer, thus providing phase separation between the neighboring optical layers and a desired refractive index gradient within the multilayer architecture without adversely affecting the optical path length therethrough. Such a multilayer structure may be configured as a light retention layer, antireflective coating, bandpass filter, etc.
1 . A multilayer structure comprising:
a first amorphous optical layer having a refractive index (n1);
a crystalline optical layer overlying the first amorphous optical layer, the crystalline optical layer having a refractive index (n2); and
an amorphous barrier layer located between the first amorphous optical layer and the crystalline optical layer, the amorphous barrier layer having a refractive index (nb).
2 . The multilayer structure of claim 1 , wherein a composition of the first amorphous optical layer and a composition of the crystalline optical layer are substantially equivalent.
3 . The multilayer structure of claim 1 , wherein n1<n2.
4 . The multilayer structure of claim 1 , wherein n1<nb<n2.
5 . The multilayer structure of claim 1 , wherein nb<n1<n2.
6 . The multilayer structure of claim 1 , wherein the amorphous barrier layer has a thickness of less than approximately 10 nm.
7 . The multilayer structure of claim 1 , wherein the amorphous barrier layer comprises a compound selected from the group consisting of aluminum oxide, niobium oxide, tantalum oxide, and magnesium fluoride.
8 . The multilayer structure of claim 1 , wherein the amorphous barrier layer is configured to inhibit crystallization of the first amorphous optical layer.
9 . The multilayer structure of claim 1 , further comprising a second amorphous optical layer disposed over the crystalline optical layer opposite to the amorphous barrier layer, the second amorphous optical layer having a refractive index (n3).
10 . The multilayer structure of claim 9 , wherein a composition of the first amorphous optical layer, a composition of the crystalline optical layer, and a composition of the second amorphous optical layer are independently selected from the group consisting of silicon dioxide and titanium oxide.
11 . The multilayer structure of claim 9 , wherein a composition of the first amorphous optical layer and a composition of the second amorphous optical layer are substantially equivalent.
12 . The multilayer structure of claim 9 , wherein a composition of the first amorphous optical layer, a composition of the crystalline optical layer, and a composition of the second amorphous optical layer are substantially equivalent.
13 . The multilayer structure of claim 9 , wherein n1=n3.
14 . The multilayer structure of claim 9 , wherein n1=n3<n2.
15 . An optical waveguide comprising the multilayer structure of claim 1 .
16 . A multilayer thin film comprising an amorphous barrier layer disposed between a first amorphous optical layer and a crystalline optical layer, wherein a composition of the amorphous optical layer is substantially equivalent to a composition of the crystalline optical layer.
17 . The multilayer thin film of claim 16 , further comprising a second amorphous optical layer disposed over the crystalline optical layer opposite to the amorphous barrier layer, wherein a refractive index of the first amorphous optical layer is substantially equal to a refractive index of the second amorphous optical layer.
18 . The multilayer thin film of claim 16 , wherein a refractive index of the crystalline optical layer is greater than the refractive index of the first amorphous optical layer.
19 . A method comprising:
forming a crystalline optical layer over a substrate;
forming an amorphous barrier layer over the crystalline optical layer; and
forming an amorphous optical layer directly over the amorphous barrier layer, wherein a composition of the crystalline optical layer and a composition of the amorphous optical layer are substantially equivalent.
20 . The method of claim 19 , wherein the amorphous barrier layer has a thickness of less than approximately 10 nm.