U.S. patent application number 15/584178 was filed with the patent office on 2018-05-10 for optical modulator and optical modulating array including the same.
This patent application is currently assigned to SAMSUNG ELECTRONICS CO., LTD.. The applicant listed for this patent is SAMSUNG ELECTRONICS CO., LTD.. Invention is credited to Byounglyong CHOI, Jungwoo KIM, Eunkyung LEE, Kyuil LEE.
Application Number | 20180129079 15/584178 |
Document ID | / |
Family ID | 62064534 |
Filed Date | 2018-05-10 |
United States Patent
Application |
20180129079 |
Kind Code |
A1 |
LEE; Eunkyung ; et
al. |
May 10, 2018 |
OPTICAL MODULATOR AND OPTICAL MODULATING ARRAY INCLUDING THE
SAME
Abstract
An optical modulator may include an optical wave guide
configured to allow a light to pass therethrough, and an optical
modulating layer embedded in the optical wave guide and configured
to modulate a phase of the light. The optical wave guide may
include a first material that has a first lattice constant. The
optical modulating layer may include a second material that has a
second lattice constant different from the first lattice constant.
The phase of the light may be modulated by the optical modulating
layer based on a difference between the first lattice constant and
the second lattice constant.
Inventors: |
LEE; Eunkyung; (Seoul,
KR) ; CHOI; Byounglyong; (Seoul, KR) ; KIM;
Jungwoo; (Hwaseong-si, KR) ; LEE; Kyuil;
(Incheon, KR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SAMSUNG ELECTRONICS CO., LTD. |
Suwon-si |
|
KR |
|
|
Assignee: |
SAMSUNG ELECTRONICS CO.,
LTD.
Suwon-si
KR
|
Family ID: |
62064534 |
Appl. No.: |
15/584178 |
Filed: |
May 2, 2017 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G02B 6/10 20130101; G02F
2202/10 20130101; G02F 1/0102 20130101; G02F 2203/50 20130101; G02F
1/011 20130101 |
International
Class: |
G02F 1/01 20060101
G02F001/01; G02F 1/19 20060101 G02F001/19; G02B 6/10 20060101
G02B006/10 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 8, 2016 |
KR |
10-2016-0148184 |
Claims
1. An optical modulator comprising: an optical wave guide
configured to allow light to pass in a longitudinal direction of
the optical wave guide, the optical wave guide comprising a first
material having a first lattice constant; and an optical modulating
layer having a thickness and embedded in the optical wave guide,
the optical modulating layer comprising a second material having a
second lattice constant different from the first lattice constant,
and the optical modulating layer being configured to modulate a
phase of the light based on a difference between the first lattice
constant and the second lattice constant, wherein the thickness of
the optical modulating layer is equal to or less than 100 nm such
that the phase of light proceeding through the optical modulating
layer is modulated based on a strain generated by a difference in
the lattice constants between the optical wave guide and the
optical modulating layer.
2. The optical modulator of claim 1, wherein each of the optical
wave guide and the optical modulating layer comprises at least one
of a group IV element, a group III elements, a group V element, and
a silicon nitride.
3. The optical modulator of claim 1, wherein a ratio of the second
lattice constant to the first lattice constant is equal to or
greater than 0.9 and equal to or less than 1.1.
4. The optical modulator of claim 1, wherein the optical modulating
layer comprises an element that is not included in the optical wave
guide.
5. The optical modulator of claim 1, wherein the optical modulating
layer comprises (i) a first element included in the optical wave
guide and (ii) a second element not included in the optical wave
guide.
6. The optical modulator of claim 5, wherein a composition ratio of
the first element and the second element is constant.
7. The optical modulator of claim 1, wherein each of the optical
wave guide and the optical modulating layer comprises a first
element and a second element, and a composition ratio of the first
element and the second element in the optical wave guide is
different from a composition ratio of the first element and the
second element in the optical modulating layer.
8. The optical modulator of claim 1, wherein the optical modulating
layer is of a thin layer type.
9. The optical modulator of claim 1, wherein a thickness of the
optical modulating layer is equal to or less than 100 nm.
10. The optical modulator of claim 1, wherein a longitudinal
direction of the optical modulating layer is parallel to a
longitudinal direction of the optical wave guide.
11. The optical modulator of claim 1, wherein a longitudinal
direction of the optical modulating layer intersects with a
longitudinal direction of the optical wave guide.
12. The optical modulator of claim 1, wherein a portion of the
optical modulating layer is exposed to a surface of the optical
modulator.
13. The optical modulator of claim 1, wherein an entire surface
area of the optical modulating layer is surrounded by the optical
wave guide.
14. The optical modulator of claim 1, further comprising an
additional optical modulating layer embedded in the optical wave
guide, the additional optical modulating layer being separated from
the optical modulating layer.+
15. The optical modulator of claim 14, wherein the optical
modulating layer and the additional optical modulating layer are
arranged in one of a direction parallel to a longitudinal direction
of the optical wave guide and a direction perpendicular to the
longitudinal direction of the optical wave guide.
16. The optical modulator of claim 1, further comprising a heat
providing layer disposed on the optical modulator and configured to
provide heat to the optical modulator.
17. The optical modulator of claim 16, wherein the heat providing
layer overlaps with at least a portion of the optical modulating
layer.
18. An optical modulating array comprising: a plurality of optical
modulators, each of the plurality of optical modulators comprising:
an optical wave guide configured to allow light to pass in a
longitudinal direction of the optical wave guide, the optical wave
guide comprising a first material having a first lattice constant,
and an optical modulating layer having a thickness and embedded in
the optical wave guide, the optical modulating layer comprising a
second material having a second lattice constant different from the
first lattice constant, and the optical modulating layer being
configured to modulate a phase of the light based on a difference
between the first lattice constant and the second lattice constant,
wherein the plurality of optical modulators are separated from each
other, wherein the thickness of the optical modulating layer is
equal to or less than 100 nm such that the phase of light
proceeding through the optical modulating layer is modulated based
on a strain generated by a difference in the lattice constants
between the optical wave guide and the optical modulating
layer.
19. The optical modulating array of claim 18, wherein at least two
optical modulators of the plurality of optical modulators have
different levels of phases to be modulated.
20. The optical modulating array of claim 19, wherein a level of
the modulated phase varies depending on at least one of a location,
a size, a number, and a material of the plurality of optical
modulators.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims priority from Korean Patent
Application No. 10-2016-0148184, filed on Nov. 8, 2016, in the
Korean Intellectual Property Office, the disclosure of which is
incorporated herein in its entirety by reference.
BACKGROUND
1. Field
[0002] The present disclosure relates to an optical modulator
capable of modulating phases and an optical modulating array
including the same.
2. Description of the Related Art
[0003] Optical phase array (OPA) technology is mainly used for
modulating phases and wavelengths. A light-steering light detection
and ranging (LIDAR) structure including silicon semiconductors may
include a light input unit, a light separator, a phase modulator,
and a light output unit of a grating coupler type. Outputted light
may be steered by means of phase modulation.
[0004] Phase modulation methods may include a method of providing
heat to a wave guide when light proceeds in the wave guide, a
method of electrically injecting electric charges into the wave
guide, a method of applying an electric field to the wave guide,
etc.
[0005] When a heat method or an electrical method is used for phase
modulation, a change in a refractive index may not be large enough,
and thus, problems such as a reduction in modulation efficiency or
an increase in sizes of elements may occur. In addition, when
methods of various modulation types are used, an adverse effect may
occur or a modulation speed may vary. Thus, effect maximization may
be difficult to realize even when various methods are
simultaneously used.
SUMMARY
[0006] Provided are an optical modulator capable of modulating
phases and an optical modulating array including the same.
[0007] Additional aspects will be set forth in part in the
description which follows and, in part, will be apparent from the
description, or may be learned by practice of various exemplary
embodiments.
[0008] According to an aspect of an exemplary embodiment, an
optical modulator may include: an optical wave guide configured to
allow a light to pass therethrough, the optical wave guide
including a first material having a first lattice constant; and an
optical modulating layer embedded in the optical wave guide, the
optical modulating layer including a second material having a
second lattice constant different from the first lattice constant,
and the optical modulating layer being configured to modulate a
phase of the light based on a difference between the first lattice
constant and the second lattice constant.
[0009] In addition, each of the optical wave guide and the optical
modulating layer may include at least one of a group IV element, a
group III element, a group V element, and a silicon nitride.
[0010] A ratio of the second lattice constant to the first lattice
constant may be equal to or greater than about 0.9 and equal to or
less than about 1.1.
[0011] The optical modulating layer may include an element that is
not included in the optical wave guide.
[0012] The optical modulating layer may include a first element
included in the optical wave guide and a second element not
included in the optical wave guide.
[0013] A composition ratio of the first element and the second
element may be constant.
[0014] Both the optical wave guide and the optical modulating layer
may include the first and second elements, and a composition ratio
of the first element and the second element in the optical wave
guide may be different from a composition ratio of the first
element and the second element in the optical modulating layer.
[0015] The optical modulating layer may include a thin layer.
[0016] A thickness of the optical modulating layer may be equal to
or less than about 100 nm.
[0017] A longitudinal direction of the optical modulating layer may
be parallel to a longitudinal direction of the optical wave
guide.
[0018] The longitudinal direction of the optical modulating layer
may intersect with the longitudinal direction of the optical wave
guide.
[0019] A portion of the optical modulating layer may be exposed to
a surface of the optical wave guide.
[0020] An entire surface area of the optical modulating layer may
be surrounded by the optical wave guide.
[0021] In addition, the optical modulator may further include an
additional optical modulating layer embedded in the optical wave
guide, the additional optical layer being separated from the
optical modulating layer.
[0022] The optical modulating layer and the additional optical
modulating layer may be arranged in a direction parallel to the
longitudinal direction of the optical wave guide or a direction
perpendicular to the longitudinal direction of the optical wave
guide.
[0023] The optical modulator may further include a heat providing
layer disposed on the optical modulator and configured to provide
heat to the optical modulator.
[0024] The heat providing layer may overlap with at least a portion
of the optical modulating layer.
[0025] According to an aspect of an exemplary embodiment, an
optical modulating array may include one or more modulating layers
separated from each other.
[0026] At least two optical modulators of the one or more optical
layers may have different levels of phases to be modulated.
[0027] A level of the phase to be modulated may vary depending on
at least one of a location, a size, a number, and a material of the
one or more optical modulating layers.
BRIEF DESCRIPTION OF THE DRAWINGS
[0028] The above and/or other aspects will become apparent and more
readily appreciated from the following description of the exemplary
embodiments, taken in conjunction with the accompanying drawings in
which:
[0029] FIG. 1 is a diagram of an optical modulator according to an
exemplary embodiment;
[0030] FIGS. 2 through 4 are diagrams of optical modulators
according to different embodiments;
[0031] FIGS. 5 through 8 are diagrams of optical modulators
according to different embodiments;
[0032] FIG. 9 is an optical modulator according to an exemplary
embodiment;
[0033] FIG. 10 is a diagram of a hybrid type optical modulator
according to an exemplary embodiment; and
[0034] FIG. 11 is a diagram of an optical modulating array
according to an exemplary embodiment.
DETAILED DESCRIPTION
[0035] Reference will now be made in detail to exemplary
embodiments, which are illustrated in the accompanying drawings,
wherein like reference numerals refer to like elements throughout.
In this regard, the exemplary embodiments may have different forms
and should not be construed as being limited to the descriptions
set forth herein. Accordingly, the exemplary embodiments are merely
described below, by referring to the figures, to explain aspects.
Expressions such as "at least one of," when preceding a list of
elements, modify the entire list of elements and do not modify the
individual elements of the list.
[0036] Below, detailed descriptions on an optical modulator and an
optical modulating array according to exemplary embodiments will be
provided with reference to the attached drawings. Widths and
thicknesses of layers or areas illustrated in the attached drawings
may be exaggerated for convenience of explanation. Throughout the
specification, like reference numerals in the drawings denote like
elements.
[0037] FIG. 1 is a diagram of an optical modulator 100 according to
an exemplary embodiment. As illustrated in FIG. 1, the optical
modulator 100 may include an optical wave guide 10 through which
light proceeds and an optical modulating layer 20 embedded in the
optical wave guide 10. The optical modulating layer 20 modulates a
phase of light passing therethrough based on a difference in a
lattice constant with respect to the optical wave guide 10.
[0038] The optical wave guide 10 may be a layer transmitting
incident light with small light loss. A length of the optical wave
guide 10 may be greater than a side length of a cross-section of
the optical wave guide 10. Thus, light may be incident on the
optical wave guide 10 at an end of the optical wave guide 10,
proceed in a longitudinal direction L1 of the optical wave guide
10, and then, exit through another end of the optical wave guide
10. In other words, the longitudinal direction L1 of the optical
wave guide 10 may be the same as a direction in which light
proceeds. The length of the optical wave guide 10 may be in a range
from dozens of micrometers to hundreds of micrometers. The optical
wave guide 10 is illustrated as a hexahedron (e.g., a rectangular
cuboid) in FIG. 1. However, the present disclosure is not limited
thereto. The optical wave guide 10 may have various shapes such as
a polygonal column, a cylinder, and an elliptical column.
[0039] The optical wave guide 10 may include one of group IV
elements, group III/V elements, silicon dioxides, and silicon
nitrides. However, the present disclosure is not limited thereto.
For example, the optical wave guide 10 may include silicon (Si) as
a group IV element, at least one of aluminum (Al), gallium (Ga),
and indium (In) as a group III element, binary compound, ternary
compound, or quaternary compound formed with at least one of
phosphorus (P), arsenic (As), and antimony (Sb) as a group V
element, silicon nitride (SiN), and at least one combination of
these elements.
[0040] The optical modulating layer 20 may be embedded in the
optical wave guide 10. As illustrated in FIG. 1, at least a portion
of the optical modulating layer 20 may be embedded from a surface
of the optical wave guide 10 toward the inside of the optical wave
guide 10. In addition, the other portion of the optical modulating
layer 20 may extend to the surface of the optical wave guide 10 and
be exposed together with the optical wave guide 10.
[0041] The optical modulating layer 20 may be of a thin layer type.
For example, a longitudinal direction L2 of the optical modulating
layer 20 may be parallel to the longitudinal direction L1 of the
optical wave guide 10, and a direction of a thickness t of the
optical modulating layer 20 may intersect with the longitudinal
direction L1 of the optical wave guide 10. In addition, the
thickness t of the optical modulating layer 20 may be less than a
length of the optical modulating layer 20 and may be, for example,
equal to or less than about 100 nm. The optical modulator 100 may
be formed by an epi-growth method or a deposition method.
[0042] The optical modulating layer 20 may include a material
having a different lattice constant from the optical wave guide 10,
and modulate the phase of the light proceeding therethrough by
means of the above-described difference in the lattice constant. A
lattice constant may refer to a physical dimension of unit cells in
a crystal lattice of the given material. Even though materials
included in the optical modulating layer 20 and the optical wave
guide 10 may be different from each other, the lattice constant of
the optical modulating layer 20 and that of the optical wave guide
10 may be similar to each other. For example, a ratio of the
lattice constant of the optical wave guide 10 to the lattice
constant of the optical modulating layer 20 may be in the range of
about 0.9 to about 1.1. In addition, a refractive index of the
optical modulating layer 20 and the refractive index of the optical
wave guide 10 may be similar to each other. For example, a
difference between the refractive index of the optical modulating
layer 20 and the refractive index of the optical wave guide 10 may
be equal to or less than about 1.5.
[0043] The optical modulating layer 20 may include at least one of
group IV elements, group III/V elements, silicon oxides, and
silicon nitrides. However, the present disclosure is not limited
thereto. For example, the optical wave guide 10 may include Si as a
group IV element, at least one of Al, Ga, and In as a group III
element, binary compound, ternary compound, or quaternary compound
formed with at least one of P, As, and Sb as a group V element,
SiN, and at least one combination of these elements.
[0044] In detail, the optical wave guide 10 and the optical
modulating layer 20 may include different elements from each other.
In other words, the optical wave guide 10 may include a first
element, while the optical modulating layer 20 may include a second
element. Even though the first element and the second element are
different from each other, lattice constants thereof may be similar
to each other. For example, the optical wave guide 10 may include
Si, while the optical modulating layer 20 includes Ge. The Si and
Ge may have single crystals. A ratio of a difference in the lattice
constants between Si and Ge over the lattice constant of Si may be
about 4%. Thus, if the optical modulating layer 20 is allowed to
grow epitaxially, strain may occur in the optical modulating layer
20 having a thickness of equal to or less than several nanometers
and the phase of a proceeding light may be modulated.
[0045] Alternatively, the optical modulating layer 20 may further
include other elements in addition to elements included in the
optical wave guide 10. In other words, the optical wave guide 10
may include the first element, and the optical modulating layer 20
may include the first and second elements. For example, the optical
wave guide 10 may include Si, while the optical modulating layer 20
includes a Si--Ge alloy in a Si--Ge super-lattice. For example,
when the optical modulating layer 20 includes the Si--Ge alloy, a
change in the refractive index thereof may be approximately about
0.05 when a composition ratio of Si to Ge is about 80:20, and thus,
this method may be more efficient for changing the refractive index
than conventional electrical or thermal methods. When the optical
modulating layer 20 includes a plurality of elements, the
composition ratio between the plurality of elements may be constant
or may vary. The composition ratio and a change in the composition
ratio may vary depending on the phase to be modulated.
[0046] Even though the optical wave guide 10 and the optical
modulating layer 20 include identical elements, the lattice
constants of the optical wave guide 10 and the optical modulating
layer 20 may vary according to different composition ratios between
elements. For example, the optical wave guide 10 may include
SiO.sub.2, while the optical modulating layer 20 includes
SiO.sub.3.
[0047] When the optical modulating layer 20 having a different
lattice constant is embedded in the optical wave guide 10, the
phase of light proceeding through the optical modulating layer 20
may be modulated due to a difference in the lattice constants. In
detail, when materials having mismatched lattice constants are
laminated, the strain may occur in each material due to the
difference in the lattice constants. The strain may change
effective mass of electrons or holes in the optical modulating
layer 20 and change optical characteristics such as the refractive
index. In addition, the optical characteristics may modulate the
phase of the proceeding light.
[0048] As described above, when the optical modulating layer 20
having the strain generated therein is embedded in a portion of the
optical wave guide 10 having light proceeding therethrough, a phase
modulation may easily occur. Thus, power consumption for the phase
modulation may be reduced and forming a structure for controlling
the phase modulation may be simplified.
[0049] As the optical modulating layer 20 becomes thicker, defects
such as dislocation may occur and accumulated strain may disappear.
Thus, the optical modulating layer 20 may need to have a thickness
at which the strain does not disappear. For example, the optical
modulating layer 20 may have a thickness of approximately equal to
or less than about 100 nm. When an area in which the optical wave
guide 10 and the optical modulating layer 20 overlap (hereinafter
an "optical wave layer") is also of a thin layer type, the strain
may occur. In other words, the optical wave layer may modulate the
phase of light, due to the thickness thereof as the optical
modulating layer 20. For example, when the optical wave layer
becomes thick enough for the accumulated strain to disappear, the
optical wave layer may not modulate the phase of light. However,
when the optical wave layer becomes too thin, the strain may not
disappear and thus, the phase of light proceeding through the
optical wave layer may be modulated.
[0050] In FIG. 1, the optical modulating layer 20 is illustrated as
a portion thereof exposed to a top side area of the optical wave
guide 10. However, the present disclosure is not limited thereto.
The optical modulating layer 20 may be at various locations in the
optical wave guide 10 and a plurality of optical modulating layers
20 may be in the optical wave guide 10.
[0051] FIGS. 2 through 4 are diagrams of optical modulators 101,
102, and 103 according to different exemplary embodiments. As
illustrated in FIG. 2, an optical modulating layer 20a of the
optical modulator 101 may be inside the optical wave guide 10.
Thus, an entire surface area of the optical modulating layer 20a
may be surrounded by the optical wave guide 10. Since the optical
modulating layer 20a having the strain occur therein is in the
inside area of the optical wave guide 10, modulation of light may
be more stably performed.
[0052] Alternatively, the optical modulator may include the
plurality of optical modulating layers separated from each other.
As illustrated in FIG. 3, the optical modulator 102 may include a
first optical modulating layer 20b and a second optical modulating
layer 20c separated from each other. For example, the first optical
modulating layer 20b may be on one side surface of the optical wave
guide 10 and the second optical modulating layer 20c may be on the
other side surface of the optical wave guide 10. In addition, a
portion of the optical wave guide 10, that is, the optical wave
layer 11 a may be between the first and second optical modulating
layers 20b and 20c. The first and second optical modulating layers
20b and 20c may be facing a direction perpendicular to the
longitudinal direction L1 of the optical wave guide 10.
[0053] The first and second optical modulating layers 20b and 20c
may include materials having different lattice constants from the
optical wave guide 10, be of thin layer types, and have strain
generated therein by means of the difference in the lattice
constants. When the optical wave layer is also thin, the strain may
be additionally generated. The first and second optical modulating
layers 20b and 20c may include identical materials or different
materials from each other. Alternatively, the first and second
optical modulating layers 20b and 20c may include identical
elements while composition ratios of elements are different from
each other.
[0054] Alternatively, as illustrated in FIG. 4, the optical
modulator 103 may include three or more optical modulating layers
20d, 20e, and 20f separated from each other. Some of the optical
modulating layers (20d and 20f) may be embedded on side surfaces of
the optical modulator 103 and the other of the optical modulating
layers (20e) of the optical modulating layer 20 may be embedded
inside the optical modulator 103. In addition, a plurality of
optical wave layers 11b and 11c may be between the optical
modulating layers 20d, 20e, and 20f. A plurality of optical
modulating layers 20d, 20e, and 20f and the plurality of optical
wave layers 11b and 11c may be alternately arranged in a direction
parallel to the longitudinal direction L1 of the optical wave guide
10. Intervals between the optical modulating layers 20d, 20e, and
20f may be determined as periodical or non-periodical according to
phases to be modulated. In addition, when the optical wave layers
11b and 11c are of the thin layer types, the optical wave layers
11b and 11c may modulate the phase of light along with the optical
modulating layers 20d, 20e, and 20f. As described above, various
types of the phase modulation may be realized by varying layers
generating the strain.
[0055] Alternatively, a longitudinal direction of the optical
modulating layers may intersect with a longitudinal direction of
the optical wave guide. FIGS. 5 through 8 are diagrams of optical
modulators 104, 105, 106, and 107 according to different
embodiments. As illustrated in FIG. 5, the optical modulator 104
may include the optical wave guide 10 having light proceeding
therethrough, and an optical modulating layer 30 being embedded in
the optical wave guide 10 and modulating the phase of light by
means of the difference in the lattice constant from the optical
wave guide 10.
[0056] The optical wave guide 10 may be the layer transmitting
incident light with little light loss. The length of the optical
wave guide 10 may be greater than the side length of the
cross-section of the optical wave guide 10. Thus, light may be
incident on the optical wave guide 10 through one end of the
optical wave guide 10, proceed in the longitudinal direction L1 of
the optical wave guide 10, and then, exit through the other end of
the optical wave guide 10. In other words, the longitudinal
direction L1 of the optical wave guide 10 may be the same as the
direction in which light proceeds. The length of the optical wave
guide 10 may be in the range of dozens of micrometers to hundreds
of micrometers. The cross section of the optical wave guide 10 is
illustrated as a square in FIG. 5. However, the present disclosure
is not limited thereto. The cross section of the optical wave guide
10 may have various shapes such as a circle.
[0057] The optical wave guide 10 may include at least one of group
IV elements, group III/V elements, silicon dioxides, and silicon
nitrides. However, the present disclosure is not limited thereto.
For example, the optical wave guide 10 may include Si as a group IV
element, at least one of Al, Ga, and In as a group III element,
binary compound, ternary compound, or quaternary compound formed
with at least one of P, As, and Sb as a group V element, SiN, and
at least one combination of these combinations.
[0058] The optical modulating layer 30 may be embedded in the
optical wave guide 10. As illustrated in FIG. 5, at least a portion
of the optical modulating layer 30 may be embedded from a surface
of the optical wave guide 10 toward the inside of the optical wave
guide 10. In addition, the other portion of the optical modulating
layer 30 may extend to the surface of the optical wave guide 10 and
be exposed together with the optical wave guide 10.
[0059] The optical modulating layer 30 may be of a thin layer type.
The longitudinal direction L2 of the optical modulating layer 30
may intersect with the longitudinal direction L1 of the optical
wave guide 10. For example, the longitudinal direction L2 of the
optical modulating layer 30 may be perpendicular to the
longitudinal direction L1 of the optical wave guide 10.
[0060] A direction of the thickness t of the optical modulating
layer 30 may be parallel to the longitudinal direction L1 of the
optical wave guide 10. In addition, the thickness t of the optical
modulating layer 30 may be less than the length L2 of the optical
modulating layer 30 and may be, for example, equal to or less than
about 100 nm.
[0061] The optical modulating layer 30 may include a material
having a different lattice constant from the optical wave guide 10,
and modulate the phase of the light proceeding therethrough by
means of the above-described difference in the lattice constants.
Even though materials included in the optical modulating layer 30
and the optical wave guide 10 are different from each other, the
lattice constant of the optical modulating layer 30 and the lattice
constant of the optical wave guide 10 may be similar to each other.
For example, a ratio of a lattice constant of the optical wave
guide 10 to a lattice constant of the optical modulating layer 30
may be in the range of about 0.9 to about 1.1. In addition, a
refractive index of the optical modulating layer 30 and a
refractive index of the optical wave guide 10 may be similar to
each other. For example, a difference between the refractive index
of the optical modulating layer 30 and the refractive index of the
optical wave guide 10 may be equal to or less than about 1.5.
[0062] The optical modulating layer 30 may include at least one of
group IV elements, group III/V elements, silicon oxides, and
silicon nitrides. However, the present disclosure is not limited
thereto. For example, the optical wave guide 10 may include Si as a
group IV element, at least one of Al, Ga, and In as a group III
element, binary compound, ternary compound, or quaternary compound
formed with at least one of P, As, and Sb as a group V element,
SiN, and at least one combination of these combinations.
[0063] In detail, the optical wave guide 10 and the optical
modulating layer 30 may include different elements from each other.
In other words, the optical wave guide 10 may include the first
element, while the optical modulating layer 30 may include the
second element. Even though the first and second elements are
different from each other, lattice constants thereof may be similar
to each other. For example, the optical wave guide 10 may include
Si, while the optical modulating layer 30 may include Ge. The Si
and Ge may have single crystals.
[0064] Alternatively, the optical modulating layer 30 may further
include other elements in addition to elements included in the
optical wave guide 10. In other words, the optical wave guide 10
may include the first element, and the optical modulating layer 30
may include the first and second elements. For example, the optical
wave guide 10 may include Si, while the optical modulating layer 30
includes a Si--Ge alloy in a Si--Ge super-lattice. When the optical
modulating layer 30 includes a plurality of elements, the
composition ratio between the plurality of elements may be constant
or may vary. The composition ratio and a change in the composition
ratio may vary depending on the phase to be modulated.
[0065] Even though the optical wave guide 10 and the optical
modulating layer 30 may include identical elements, the lattice
constants of the optical wave guide 10 and the optical modulating
layer 30 may vary according to different composition ratios between
elements. For example, the optical wave guide 10 may include
SiO.sub.2, while the optical modulating layer 30 includes
SiO.sub.3.
[0066] When the optical modulating layer 30 having a different
lattice constant is embedded in the optical wave guide 10, the
phase of light proceeding through the optical modulating layer 30
may be modulated due to a difference in the lattice constants. In
detail, when materials having mismatched lattice constants are
laminated, the strain may occur in each material due to the
difference in the lattice constants. The strain may change optical
characteristics of each material such as the refractive index. In
addition, the optical characteristics may modulate the phase of the
proceeding light.
[0067] As the optical modulating layer 30 becomes thicker, defects
such as dislocation may occur and accumulated strain may disappear.
Thus, the optical modulating layer 30 may need to have a thickness
at which the strain does not disappear. For example, the optical
modulating layer 30 may have a thickness of approximately equal to
or less than about 100 nm.
[0068] In FIG. 5, the optical modulating layer 30 is illustrated as
a portion thereof exposed to a top side area of the optical wave
guide 10. However, the present disclosure is not limited thereto.
The optical modulating layer 30 may be at various locations in the
optical wave guide 10 and a plurality of optical modulating layers
30 may be in the optical wave guide 10.
[0069] Alternatively, as illustrated in FIG. 6, an optical
modulating layer 30a of the optical modulator 105 may be inside the
optical wave guide 10. Thus, an entire surface area of the optical
modulating layer 30a may be surrounded by the optical wave guide
10. A direction of the thickness t of the optical modulating layer
30a may be parallel to the longitudinal direction L1 of the optical
wave guide 10. Since the optical modulating layer 30a having the
strain occur therein is in the inside area of the optical wave
guide 10, modulation of light may be more stably performed.
[0070] Alternatively, the optical modulator may include a plurality
of optical modulating layers separated from each other. As
illustrated in FIG. 7, an optical modulator 106 may include a
plurality of optical modulating layers 30b, 30c, and 30d separated
from each other. An optical wave layer 11d may be between the
plurality of optical modulating layers 30b, 30c, and 30d. The
optical wave layer 11d and the optical wave guide 10 may include
identical materials and each of the plurality of optical modulating
layers 30b, 30c, and 30d may include different materials from the
material of the optical wave guide 10. The plurality of optical
modulating layers 30b, 30c, and 30d may include identical materials
or at least two optical modulating layers of the plurality of
optical modulating layers 30b, 30c, and 30d may include different
materials from each other. For example, some of the plurality of
optical modulating layers 30b, 30c, and 30d may include Ge, and the
other of the plurality of optical modulating layers 30b, 30c, and
30d may include Ge--Si alloy. Intervals between optical modulating
layers 30b, 30c, and 30d may be arranged as uniform or non-uniform.
In addition, when a thickness of the optical wave layer 11d is
sufficiently thin (e.g., below a threshold), the optical wave
layers 11d may modulate light.
[0071] The intervals between the optical modulating layers, the
materials, the number, etc. of the optical modulating layers may be
differently designed according to the phases to be modulated. As
described above, the phase modulation may be variously realized by
varying layers generating the strain.
[0072] Alternatively, as illustrated in FIG. 8, the optical
modulating layer 30e may be in contact with one end of the optical
wave guide 10. The optical modulating layer 30e illustrated in FIG.
8 may not be embedded in the optical wave guide 10. When the
optical modulating layer 30e includes a different material from the
optical wave guide 10 and is of a thin layer type, the strain may
be generated by means of a difference in the lattice constants, and
thus, the phase of light proceeding through the optical modulating
layer 30e may be modulated.
[0073] FIG. 9 is a diagram of an optical modulator 108 according to
another embodiment. As illustrated in FIG. 9, the optical modulator
108 may include both a vertical type modulating layer 40 and a
horizontal type modulating layer 50. The vertical type modulating
layer 40 may be any one of the modulating layers described above in
FIGS. 1 through 4, and the horizontal type modulating layer 50 may
be any one of the modulating layers illustrated in FIGS. 5 through
8.
[0074] As described above, the phase of light proceeding through
the optical wave guide may be modulated by arranging the optical
modulating layer, which includes a different lattice constant from
the optical wave guide and is of the thin layer type, in contact
with or embedded in the optical wave guide. A level of the phase
modulation may vary depending on the material, the location, the
number of the optical modulating layer, an arrangement relationship
between the optical modulating layers, etc.
[0075] FIG. 10 is a diagram of a hybrid type optical modulator 200
according to an exemplary embodiment. As illustrated in FIG. 10,
the hybrid type optical modulator 200 may further include a heat
providing layer 60 providing heat to the optical modulator 200
arranged on the optical modulator 200. The optical modulator 200
illustrated in FIG. 10 may include the optical modulator 100
illustrated in FIG. 1. However, the present disclosure is not
limited thereto. The optical modulators illustrated in FIGS. 2
through 9 may be applied also. The heat providing layer 60 may
include a material generating heat by an applied voltage. For
example, the heat providing layer 60 may include carbon. In
addition, an electrode applying a voltage may be on the heat
providing layer 60.
[0076] When heat is provided to the optical modulator 200, the
refractive index of the optical modulator 200 may be changed by the
heat, and thus, the phase of the proceeding light may be modulated
by means of a changed refractive index. When at least a portion of
the heat providing layer 60 overlaps with the optical modulating
layer 20, the optical modulating layer 20 having had the strain
therein may have a higher level of strain due to the heat, and
thus, a span of the phase modulation may increase.
[0077] In addition, the hybrid type optical modulator may further
include an electric charge providing layer providing electric
charges to the optical modulating layer.
[0078] A plurality of optical modulators described above may be
combined into an optical modulating array. FIG. 11 is a diagram of
an optical modulating array 300 according to an exemplary
embodiment. As illustrated in FIG. 11, the optical modulating array
300 may include a plurality of optical modulators separated from
each other. The plurality of optical modulators may be parallel to
each other. In FIG. 11, a first through eighth optical modulators
w1 through w8 are illustrated, but the total number may vary. Each
of the first through eighth optical modulators w1 through w8 may be
any one of the optical modulators described above and may
independently modulate the phase of light.
[0079] For example, light transmitting the first optical modulator
w1 may be modulated by a first level, light transmitting the second
optical modulator w2 may be modulated by a second level, light
transmitting the third optical modulator w3 may be modulated by a
third level, and so forth. In this method, light transmitting the
eighth optical modulator w8 may be modulated by an eighth level. In
other words, lights transmitting the plurality of first through
eighth optical modulators w1 through w8 may be modulated by a
certain (fixed) difference. As a result, wave-fronts of lights
outputted from each of the first through eighth optical modulators
w1 through w8 may be controlled and thus, a direction of an
outputted light may be controlled. In addition, the phase may be
controlled by using a structure including a plurality of optical
modulators of a same length which include an area having a
same-length strain applied therein (e.g., a plurality of wave
guides having the same length as the first optical modulator
w1).
[0080] The optical modulators and the optical modulating array
described above may be used for identifying objects or terrains by
means of light, and measuring distances, shapes, physical
properties, locations, etc. of the objects or the terrains.
Accordingly, the optical modulators and the optical modulating
array described above may be applied to autonomous vehicles, flying
vehicles such as drones, mobile devices, small-size personal
vehicles (for example, bicycles, motorcycles, strollers, boards,
etc.), robots, auxiliary means for people and animals (for example,
canes, helmets, clothes, accessories, watches, bags, etc.),
internet of things (IoT) devices, and building security
systems.
[0081] It should be understood that various exemplary embodiments
described herein should be considered in a descriptive sense only
and not for purposes of limitation. Descriptions of features or
aspects within each exemplary embodiment should typically be
considered as available for other similar features or aspects in
other exemplary embodiments.
[0082] While one or more exemplary embodiments have been described
with reference to the figures, it will be understood by those of
ordinary skill in the art that various changes in form and details
may be made therein without departing from the spirit and scope as
defined by the following claims.
* * * * *