# US 2016/0259090 A1 · Photonic Crystal Supporting High Frequency Sensitivity Self-collimation Phenomenon and Design Method and Use thereof

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- Number: US 2016/0259090 A1
- Document ID: US20160259090A1
- Status: Published application
- Kind: A1
- Application number: 14/761,612
- Filed: 2014-03-28
- Published: 2016-09-08
- Earliest claimed: 2013-11-27
- Assignees: Shanghai Institute of Microsystem and Information Technology, Chinese Academy; Fudan University
- Applicants: Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences; Fudan University
- Inventors: XUNYA JIANG; XULIN LIN; XIAOGANG ZHANG; WEI LI; LIANG CHEN
- Web page: https://patentgrep.com/patent/US20160259090A1

## CPC

- G02B 1/005: {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)}
- G02B 6/1225: {comprising photonic band-gap structures or photonic lattices}
- G02F 1/3511: {Self-focusing or self-trapping of light; Light-induced birefringence; Induced optical Kerr-effect}
- G02F 2202/30: Metamaterials
- G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02F: OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS

## Abstract

The present invention provides a photonic crystal supporting high frequency sensitivity self-collimation phenomenon and design method and use thereof. The photonic crystal supporting high frequency sensitivity self-collimation phenomenon has a periodic distribution of refractive index formed by at least two kinds of materials; there exists straight equi-frequency contours or flat equi-frequency surfaces in a certain band in a dispersion space of the photonic crystal, and the change rate of curvatures of the equi-frequency contours or the equi-frequency surfaces with frequencies around the frequency of straight equi-frequency contours or flat equi-frequency surfaces is at least increased at least 50 times than the change rate in vacuum. For the photonic crystal of the present invention is used for controlling diffracted intensity of light beam, detecting refractive index and the like.

## Claims

### Claim 1

A photonic crystal supporting high frequency sensitivity self-collimation phenomenon, characterized in that:
it has a periodic distribution of refractive index formed by at least two kinds of materials; there exists straight equi-frequency contours or flat equi-frequency surfaces in a certain band in the dispersion space of the photonic crystal, and the change rate of curvatures of the equi-frequency contours or the equi-frequency surfaces with frequencies around the frequency of straight equi-frequency contours or flat equi-frequency surfaces is increased at least 50 times than the change rate in vacuum.

### Claim 2

A design method for the photonic crystal supporting high frequency sensitivity self-collimation phenomenon, characterized in that, the design method for the photonic crystal supporting high frequency sensitivity self-collimation phenomenon at least includes:
a) Based on the types of crystal lattice, material and structural parameters of the photonic crystal, calculating the dispersion relation of the photonic crystal, so as to form equi-frequency contours and to determine a candidate photonic crystal that exists a self-collimation point and one or more van Hove singularities inside the Brillouin zone within the same band, the material parameter of the photonic crystal comprises refractive indexes of various materials that constitutes the photonic crystal, the structural parameter of the photonic crystal comprises shapes and sizes of various materials that constitutes the photonic crystal and lattice lengths of each directions thereof, the types of the van Hove singularities inside the Brillouin zone comprises one or more of saddle-point-type van Hove singularities, a maximum-point-type van Hove singularities and minimum-point-type van Hove singularities;
b) Change each material and structural parameter of the candidate photonic crystal, recalculating the dispersion relation to form equi-frequency contours and to determine the key parameter of the photonic crystal, wherein, the key parameter of the photonic crystal refers to, the material and/or structural parameter of the photonic crystal as its value changes, it enables the van Hove singularities move close to or away from the self-collimation point;
c) Based on the dispersion relation around the self-collimation point, determining the distribution of the self-collimation frequency sensitivity γ with the key parameter of the photonic crystal;
d) Selecting a required self-collimation frequency sensitivity determining the value of the key parameter of the photonic crystal and the value of other structural and material parameters of the photonic crystal according to the distribution of the self-collimation frequency sensitivity with the key parameter of the photonic crystal.

### Claim 3 (depends on 2)

The design method for the photonic crystal supporting high frequency sensitivity self-collimation phenomenon according to claim 2, characterized in that, calculate the dispersion relation of the photonic crystal, based on the types of crystal lattice, material and structural parameters of the photonic crystal, and by adopting one of the plane wave expansion method, the FDTD method, and the finite element method.

### Claim 4 (depends on 2)

The design method for the photonic crystal supporting high frequency sensitivity self-collimation phenomenon according to claim 2, characterized in that, the self-collimation frequency sensitivity is:
γ
=
(
1
c

/

ω
2
)

∂
κ

/

∂
ω

|
ω
=
ω
sc
,
k
1
=
0
=
(
1
c

/

ω
2
)

∂
3

ω
∂
k
2

∂
k
1
2

/

u
g
2

|
ω
=
ω
sc
,
k
1
=
0
,
wherein, κ represents curvature of the equi-frequency contour, ω represents a frequency of the equi-frequency contour, ωsc is the frequency of the self-collimation point, k1 represents the wavevector component parallel with the straight equi-frequency contours, k2 represents the wavevector component perpendicular with the straight equi-frequency contours, group velocity νg=√{square root over ((∂ω/∂k1)2+(∂ω/∂k2)2)}, constant c is the velocity of light in vacuum, normalized base c/ω2 represents an absolute value of change rate of curvature κ of the equi-frequency contours with frequency ω in vacuum.

### Claim 5

A method for controlling diffraction of light beam based on a photonic crystal supporting high frequency sensitivity self-collimation phenomenon, characterized in that, the method for controlling diffraction of light beam based on a photonic crystal supporting high frequency sensitivity self-collimation phenomenon at least comprises the following steps:
A) Providing a piece of photonic crystal supporting high frequency sensitivity self-collimation phenomenon;
B) Launching a light beam to be regulated into the photonic crystal along a self-collimation direction of one side of the provided photonic crystal;
C) Receiving the incident light beam at the other side of the provided photonic crystal.

### Claim 6 (depends on 5)

The method for controlling diffracted intensity of light beam based on a photonic crystal supporting high frequency sensitivity self-collimation phenomenon according to claim 5, further characterized in that, diffraction of the light beam propagated in the photonic crystal is determined by a curvature of equi-frequency contours.

### Claim 7 (depends on 5)

The method for controlling diffraction of light beam based on a photonic crystal supporting high frequency sensitivity self-collimation phenomenon according to claim 5, further characterized in that, material and structural parameters of the photonic crystal is determined according to the frequency of the incident light beam and the degree of diffraction intended to be achieved.

### Claim 8 (depends on 5)

The method for controlling diffraction of light beam based on a photonic crystal supporting high frequency sensitivity self-collimation phenomenon according to claim 5, further characterized in that, a lateral size of the photonic crystal relative to the self-collimation direction satisfies the condition that: it enables to hold the light beam propagate in the photonic crystal rather than escaping from lateral of the photonic crystal.

### Claim 9 (depends on 5)

The method for controlling diffracted intensity of light beam based on a photonic crystal supporting high frequency sensitivity self-collimation phenomenon according to any one of claims 5 characterized in that, it further comprises: changing the curvature of the equi-frequency contours at the frequency of the incident light beam by changing the refractive index of a certain or some certain component of the photonic crystal, so as to achieve tunable diffraction control.

### Claim 10

A method for detecting refractive index based on a photonic crystal supporting high frequency sensitivity self-collimation phenomenon, characterized in that, the method for detecting refractive index based on a photonic crystal supporting high frequency sensitivity self-collimation phenomenon at least comprises the following steps:
1) Providing a piece of photonic crystal supporting high frequency sensitivity self-collimation phenomenon, a light source placed at one side of the photonic crystal and a light intensity detector arranged at the other side of the photonic crystal being opposite to the light source; wherein, there are interspaces of periodic configuration inside the photonic crystal; the light source enables to generate a light beam with specific frequency, width and intensity along with the incident direction of the self-collimation; the light intensity detector is used for detecting a centre intensity of the light beam that emits from the photonic crystal;
2) The interspaces of periodic configuration inside the photonic crystal are filled with multiple materials of known refractive indexes, respectively, to form each first filled photonic crystal;
3) Making a light beam launch into each first filled photonic crystal, and detecting a centre intensity of outgoing beam corresponding to each refractive index, so as to determine the relationship between each refractive index and the intensity of the outgoing beam;
4) Filling the photonic crystal with sample to be tested, to form a second filled photonic crystal;
5) Making a light beam launch into the second filled photonic crystal, and determining the refractive index of the sample to be tested based on the measured centre intensity of outgoing beam, and the relationship between the refractive index and the intensity of the outgoing beam.