Zero-index photonic crystals for visible and near infrared applications

Patent metadata

Field	Value
Publication number	US-2021311226-A1
Application number	US-201917265063-A
Country	US
Kind code	A1
Filing date	Aug 1, 2019
Priority date	Aug 2, 2018
Publication date	Oct 7, 2021
Grant date	—

Abstract

A two dimensional (2D) photonic crystal (PhC) structure includes a substrate and a periodic grating structure formed on the substrate. The periodic grating structure includes a plurality of gratings having a grating period, a. Each pair of adjacent gratings is separated by air. Each grating has a grating width, d, and includes a plurality of alternating layers of a first material and a second material. The first material corresponds to a high index material. The second material corresponds to a low index material. A ratio of a first refractive index of the first material to a second refractive index of the second material is greater than or equal to two. Each first material layer has a first thickness, t 1 . Each second material layer has a second thickness, t 2 . The 2D PhC structure has a structure refractive index at or near zero for a range of frequencies.

First claim

1 . A two dimensional (2D) photonic crystal (PhC) structure comprising:
a substrate; and a periodic grating structure formed on the substrate, the periodic grating structure comprising a plurality of gratings having a grating period, a, each pair of adjacent gratings separated by air, each grating having a grating width, d, and comprising a plurality of alternating layers of a first material and a second material, the first material corresponding to a high index material, the second material corresponding to a low index material, a ratio of a first refractive index of the first material to a second refractive index of the second material greater than or equal to two, each first material layer having a first thickness, t 1 , each second material layer having a second thickness, t 2 , wherein the 2D PhC structure has a structure refractive index at or near zero for a range of frequencies.

2 . The 2D PhC structure of claim 1 , wherein the first material is TiO 2 (titanium dioxide) and the second material is SiO 2 (silicon dioxide).

3 . The 2D PhC structure of claim 1 , wherein the periodic grating structure is configured to receive TE (transverse electric)-polarized light.

4 . The 2D PhC structure of claim 1 , wherein the plurality of layers are formed using oblique angle deposition.

5 . The 2D PhC structure of claim 4 , wherein the first material is TiO 2 (titanium dioxide), the second material is SiO 2 (silicon dioxide), a first deposition angle during formation of the layers of TiO 2 is at or near 30° and a second deposition angle during formation of the layers of SiO 2 is at or near 89°.

6 . The 2D PhC structure according to claim 1 , wherein the periodic grating structure comprises five first material layers and four second material layers.

7 . The 2D PhC structure according to claim 1 , wherein the grating period is 600 nanometers (nm), the grating width is 270 nm, the first material is dense TiO 2 , the second material is porous SiO 2 , the first refractive index is 2.45, the second refractive index 1.05, the first thickness is 270 nm and the second thickness is 330 nm.

8 . The 2D PhC structure according to claim 1 , wherein the substrate comprises silicon.

9 . The 2D PhC structure according to claim 1 , wherein the range of frequencies corresponds to at least one of visible and/or near-infrared wavelengths.

10 . The 2D PhC structure according to claim 1 , wherein the 2D PhC structure is C 4v symmetric.

11 . A method for forming a two dimensional (2D) photonic crystal (PhC) structure, the method comprising:
depositing, by oblique angle deposition, a plurality of alternating layers of a first material and a second material onto a substrate to form a layered structure, the first material corresponding to a high index material, the second material corresponding to a low index material, a ratio of a first refractive index of the first material to a second refractive index of the second material greater than or equal to two, each first material layer having a first thickness, t 1 , each second material layer having a second thickness, t 2 ; patterning, by photolithography, a plurality of photoresist strips onto a top layer of the plurality of alternating layers, each of the plurality of photoresist strips comprising a photoresist soft mask; depositing, by electron-beam evaporation, a solid material with thickness t mask onto the photoresist strips, the solid material corresponding to a hard etch mask; selectively removing, by sonication, the photoresist soft mask; removing anisotropically, by dry etching, a plurality of portions of the layered structure; and stripping the hard etch mask to yield the 2D PhC structure, wherein the 2D PhC structure has a structure refractive index at or near zero for a range of frequencies.

12 . The method of claim 11 , wherein the first material is TiO 2 (titanium dioxide) and the second material is SiO 2 (silicon dioxide).

13 . The method of claim 11 , wherein the first material is TiO 2 (titanium dioxide), the second material is SiO 2 (silicon dioxide), a first deposition angle during deposition of the layers of TiO 2 is at or near 30° and a second deposition angle during deposition of the layers of SiO 2 is at or near 89°.

14 . The method of claim 11 , wherein the 2D PhC structure is configured to receive TE (transverse electric)-polarized light.

15 . The method according to claim 11 , wherein the range of frequencies corresponds to at least one of visible and/or near-infrared wavelengths.

16 . The method according to claim 11 , wherein the 2D PhC structure is C 4v symmetric.

17 . The method according to claim 11 , wherein the 2D PhC structure comprises a periodic grating structure formed on the substrate, the periodic grating structure comprising a plurality of gratings having a grating period, a, each pair of adjacent gratings separated by air, each grating having a grating width, d, and comprising a plurality of alternating layers of the first material and the second material.

18 . The method of claim 17 , wherein the grating period is 600 nanometers (nm), the grating width is 270 nm, the first material is dense TiO 2 , the second material is porous SiO 2 , the first refractive index is 2.45, the second refractive index 1.05, the first thickness is 270 nm and the second thickness is 330 nm.

19 . The method according to claim 11 , wherein the dry etching is performed according to a recipe.

20 . The method of claim 19 , wherein the recipe comprises a parameter selected from the group comprising ICP (inductively coupled plasma), RIE (reactive ion etching), pressure, He (helium) cooling, temperature, flow rate of CHF 3 (Fluoroform) and flow rate of O 2 (Oxygen).

Assignees

• Rensselaer Polytech Inst

Inventors

• Liu Shizhao
• Plawsky Joel L

Classifications

• G02B1/005 Primary

  made of photonic crystals or photonic band gap materials (photonic band-gap structures or photonic lattices in integrated optics G02B6/1225; photonic band-gap structures or photonic lattices in optical fibres G02B6/02295) · CPC title

• B82Y20/00

  Nanooptics, e.g. quantum optics or photonic crystals · CPC title

• G02B1/11

  Anti-reflection coatings · CPC title

• G02B5/1847

  Manufacturing methods · CPC title

• G02B5/1857

  using exposure or etching means, e.g. holography, photolithography, exposure to electron or ion beams · CPC title