Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
WO 01/48532 CA 02392467 2002-05-23 PCT/US00/32164
INTEGRATED PLANAR OPTICAL WAVEGUIDE AND SHUTTER
FIELD OF THE INVENTION
The present invention is directed to an optical switch for allowing or
preventing the
passage of light between an input waveguide and an output waveQuide.
BACKGROUND OF THE INVENTION
Optical switches are essential components in an optical network for
determining and
controlling the path along which a light signal propagates. Typically, an
optical signal (the
terms "light signal" and optical signal" are used interchangeably herein and
are intended to be
broadly construed and to refer to visible, infrared, ultraviolet light. and
the like), is guided by
a waveguide along an optical path, typically defined by the waveguide core. It
may become
necessary or desirable to block the optical signal so it does not continue
along a waveguide or
redirect the optical signal so that it propagates along a different optical
path, i.e., through a
different waveguide core. Transmission of an optical signal from one waveguide
to another
may require that the optical signal propagate through a medium which may have
an index of
refraction different than the index of refraction of the waveguides (which
typically have
approximately the same refractive index). It is known that the transmission
characteristics of
an optical signal may be caused to change if that signal passes through
materials (mediums)
having different indices of refraction. For example, an unintended phase shift
may be
introduced into an optical signal passing from a material having a first index
of refraction to a
material having a second index of refraction due to the difference in velocity
of the signal as
it propagates through the respective materials and due, at least in part, to
the materials'
respective refractive indices. Additionally, a reflected signal may be
produced due to the
WO 01/48532 CA 02392467 2002-05-23 PCT/US00/32164
mismatch of polarization fields at the interface between the two media. As
used herein, the
term "medium" is intended to be broadly construed and to include a vacuum.
This reflection of the optical signal is undesirable because it reduces the
transmitted
power by the amount of the reflected signal, and so causes a loss in the
transmitted signal. In
addition, the reflected signal may travel back in the direction of the optical
source, which is
also known as optical return loss. Optical return loss is highly undesirable,
since it can
destabilize the optical signal source.
If two materials (or mediums) have approximately the same index of refraction,
there
is no significant change in the transmission characteristics of an optical
signal as it passes
from one material to the other. One solution to the mismatch of refractive
indices involves
the use of an index matching fluid. A typical use in an optical switch is to
fill a trench
between at least two waveguides with a material having an index of refraction
approximately
equal to that of the waveguides. Thus, the optical signal does not experience
any significant
change in the index of refraction as it passes through the trench from one
waveguide to
1 S another.
An example of that solution may be found in international patent application
number
WO 00/25160. That application describes a switch that uses a collimation
matching fluid in
the chamber between the light paths (i.e., between waveguides) to maintain the
switch's
optical performance. The use of an index matching fluid introduces a new set
of
considerations, including the possibility of leakage and a possible decrease
in switch response
time due to the drag on movement of the switching element in a fluid.
In addition, the optical signal will experience insertion loss as it passes
across a trench
and between waveguides. A still further concern is optical return loss caused
by the
discontinuity at the waveguide input/output facets and the trench. In general,
as an optical
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signal passes through the trench, propagating along a propagation direction,
it will encounter
an input facet of a waveguide which, due to physical characteristics of that
facet (e.g.,
reflectivity, verticality, waveguide material, etc.) may cause a reflection of
part (in terms of
optical power) of the optical signal to be directed back across the trench
(i.e., an a direction
opposite of the propagation direction). This is clearly undesirable.
Size is also an ever-present concern in the design. fabrication, and
construction of
optical components (i.e., devices. circuits, and systems). It is clearly
desirable to provide
smaller optical components so that optical devices. circuits, and systems may
be fabricated
more densely, consume less power, and operate more efficiently.
SUMMARY OF THE INVENTION
The present invention is directed to an optical switch having an input
waveguide and
an output waveguide separated by and disposed around a trench. The input
waveguide and
the output waveguide have respective optical paths defined by their respective
cores; those
optical paths (and cores) being generally aligned or coaxial with each other.
The trench has a
medium provided therein that has a refractive index different from that of the
waveguides.
Back reflection is therefore avoided, since the input and output waveguides
are separated by a
distance insufficient to affect the transmission characteristics of an optical
signal propagating
from the input waveguide to the output waveguide, even though the optical
signal experiences
different refractive indices as it propagates from the input waveguide to the
output
waveguide. Thus, even though an optical signal passing from the input
waveguide to the
output waveguide must completely traverse the trench, the distance over which
the optical
signal must travel between the waveguides is small enough so as to not affect
the optical
transmission characteristics of that signal.
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The invention accordingly comprises the features of construction. combination
of
elements, and arrangement of parts which will be exemplified in the disclosure
herein. The
scope of the invention will be indicated in the claims.
BRIEF DESCRIPTION OF THE DRAWINGS
In the drawing figures, which are not to scale. and which are merely
illustrative, and
wherein like reference characters denote similar elements throughout the
several views:
FIG. 1 is a top plan view of an optical switch constructed in accordance with
the
present invention;
FIGS. 2A and 2B are cross-sectional views of two embodiments of an optical
switch
taken along line 2-2 of FIG. 1;
FIG. 3 is a cross-sectional view of a waveguide of the optical switch taken
along line
3-3 of FIG. l;
FIG. 4 is a cross-sectional top view of an embodiment of an electrothermal
actuator
provided as part of an optical switch in accordance with the present
invention;
FIG. 5 is a top plan view of another embodiment of an electrostatic actuator
provided
as part of an optical switch in accordance with the present invention;
FIG. 6 is a top plan view of a further embodiment of an electrostatic actuator
provided
as part of an optical switch in accordance with the present invention;
FIG. 7 is a top plan view showing a close-up of a portion of a tapered portion
of the
waveguide of FIG. l;
FIGS. 8A and 8B depict the assembly of an optical switch in accordance with an
embodiment of the present invention; and
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FIGS. 9A and 9B are partial side cross-sectional views showing portions of the
structure of optical switches in accordance with the present invention
manufactured using
flip-chip and monolithic fabrication techniques, respectively, together with
external
components and connecting hardware.
DETAILED DESCRIPTION OF THE
PRESENTLY PREFERRED EMBODIMENTS
The present invention is directed to an optical switch having an input
waveguide and
an output waveguide separated by and disposed around a trench. The input
waveguide and
the output waveguide have respective optical paths defined by their respective
cores; and
those optical paths (and cores) are aligned or coaxial with each other. Those
waveguides are
also separated by the trench, the trench having a medium provided therein that
has a refractive
index different from that of the waveguides. The input and output waveguides
are separated
by a distance insufficient to affect the transmission characteristics of an
optical signal
propagating from the input waveguide to the output waveguide, even though the
optical signal
experiences different refractive indices as it propagates from the input
waveguide to the
output waveguide. Thus, even though an optical signal passing from the input
waveguide to
the output waveguide must completely traverse the trench, the distance over
which the optical
signal must travel between the waveguides is small enough so as to not affect
the optical
transmission characteristics of that signal.
That is, while the trench is large enough to allow for the finite thickness of
a shutter to
be placed inside the trench, the trench should also be as small as possible to
minimize the
light diffraction in the trench gap.
Referring now to the drawings in detail, and with initial reference to FIG. 1,
an optical
switch 1 constructed in accordance with an embodiment of the present invention
is there
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depicted. The optical switch 1 of the present invention is preferably
constructed of silica-
based semiconductors (e.g., Si02), and other waveguides which weakly-confine
light. Other
semiconductors such as, for example, GaAs and InP, also might be used. In
addition, the
waveguide construction described below is provided as an illustrative. non-
limiting example
of an embodiment of the present invention: other waveguide geometries and
configurations
are contemplated by and fall within the scope and spirit of the present
invention.
FIG. 1 depicts a 1 x 1 switch. The switch 1 includes an input waveguide 3 and
an
output waveguide 5 arranged around and separated by a trench 1 ~. A cross-
section of the
output waveguide ~, which is also exemplary of the input waveguide 3, is
depicted in FIG. 3.
The following description of and reference to the output waveguide ~ shall
also apply to the
input waveguide 3. The waveguide 5 is constructed using semiconductor
fabrication
techniques and methods known to those skilled in the art, and thus need not be
described in
detail here. The waveguide 5 includes a core 7 deposited on a lower cladding
layer 9b, which
is deposited on a Si02 substrate 13 (by way of example only, a silicon or
quartz substrate also
could be used).
An upper cladding layer 9a is deposited over and around the core 7 to form a
buried
waveguide configuration.
The waveguides 3, 5 may be formed from a wide variety of materials chosen to
provide the desired optical properties. While it is preferable to construct
the optical switch 1
of the present invention on a silica-based (Si02) platform, other
semiconductors that provide
the desired optical properties may also be used. For example, the core 7 might
include
germanium-doped silica, while the upper and lower cladding 9a, 9b may include
thermal Si02
or boron phosphide-doped silica glass. This platform offer good coupling to
the fiber and a
wide variety of available index contrasts (0.35% to 1.10 %). Other platforms
which could be
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used include, by way of non-limiting example, SiO,~Ny. polymers. or
combinations thereof.
Other systems such as indium phosphide or gallium arsenide also might be
used..
With continued reference to FIG. 3. the core 7 can have an index of refraction
contrast
ranging from approximately 0.35 to 0.70%. and more preferably, the index of
refraction can
range from approximately 0.3~ to 0.55% to allow for a high coupling to an
output fiber. The
core 7 can be rectangular, with sides running from approximately 3-10 qm thick
and
approximately 3-15 qm wide. More preferably, the core 7 is square, with sides
from
approximately 6-8 ~m thick and approximately 6-14 qm wide. The upper and lower
cladding
layers 9a, 9b adjacent to core 7 can be approximately 3-I 8 ~m thick, and are
preferably
approximately I ~ ~m thick. and the core thickness can range from
approximately 7 to 8 pm
for the same reason. In choosing the ultimate core and cladding dimensions,
care should be
taken to allow for low horizontal diffraction and good tolerance of
misalignments.
Again, these dimensions are offered by way of example and not limitation.
The present invention will work with both weakly-confined waveguides and
strongly-
confined waveguides. Presently, use with weakly-confined waveguides is
preferred.
Referring again to FIG. 1, the core 7 of input waveguide 3 defines an optical
path 2
along the waveguide's longitudinal length. That optical path 2 is generally
coaxial with an
optical path defined by the core 7 of the output waveguide 5. The degree of
non coaxiality is
determined on one side by the angle formed between the perpendicular to the
propagation of
the optical signal and the input waveguide-trench interface, and on the other
side, by the
trench length, as will be explained later. Thus, the input waveguide 3 and
output waveguide 5
may be considered to be arranged in registry with each other with aligned or
coaxial optical
paths, which maximizes the amount of light transferred from input waveguide 3
to output
waveguide 5.
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A trench 1 ~ is defined in the substrate 13 (see, e.g., FIGS. 2A and 2B) that
separates
the input waveguide 3 and output waveguide 5, and around which the waveguides
are
arranged. The trench 1 ~ is filled, partly or completely, with an optically
transparent medium
120 such as, for example. air, having an associated index of refraction n. For
air. the index of
refraction is approximately equal to 1.00.
A switching element 130 either allows or blocks the passage of an optical
signal
between the input waveguide 3 and the output waveguide ~. The switching
element 130
includes a shutter 17 provided in the trench 1 ~ and an actuator 33 coupled to
the shutter 17 by
link 10 for providing selective movement of the shutter 17, as described in
more detail below.
Various embodiments of the actuator 33 are contemplated by the present
invention including,
by way of non-limiting example, electrothermal, electrostatic, and
piezoelectric, each of
which is described in more detail below.
The shutter 17 is preferably made from a light yet stiff material such as
silicon,
polymers, metallic or dielectric materials.. Shutter 17 can be a thin film
shutter. Such a low-
mass, rigid shutter 17 can be caused to move quickly in response to an
electrical signal, for
example, between the position depicted in FIG. 1, in which the optical signal
output from the
input waveguide 3 is blocked and prevented from entering the output waveguide
5, and a
second position (not shown) in which the shutter 17 is disposed outside of the
light path so
that an optical signal output from the input waveguide 3 passes across the
trench 1 ~ and
enters the output waveguide 5.
The thin film shutter 17 can be coated with a metal film 29 to block the
light.
Therefore, this switch is optical wavelength independent, i.e. both bands of
the
telecommunication windows (1310nm and 1550nm bands) are covered with the same
switch.
The thin film shutter 17 does not need to be very smooth or oriented in a
precisely vertical
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manner, the only requirement is that the shutter 17 can block the optical path
between
waveguides 3 and ~.
If desired, a highly-reflective coating can be provided on at least one
surface 140 of
the shutter 17. preferably the surface facing the output facet 21 of the input
waveguide 3
Using gold for that coating provides a highly reflective face 29 at surface
140 which reflects
the light without distortion (approximately 9~% reflection) and is essentially
wavelength
independent for telecommunication, data communication, and spectroscopic
applications, for
example. The term "facet" refers to an end of a waveguide.
With continued reference to Fig. 1. the back 28 of shutter 140 could in like
manner be
coated with gold. Such coating would allow switch 7 to operate in an alternate
mode and
regulate transmission of an input signal traveling from waveguide 5 to
waveguide 3
The shutter 17 has a height hs sufficient to completely block or reflect
light, as the
case may be. It will be appreciated that to block incoming optical signals
completely, the
shutter 17 should have a height greater than the thickness t~ of core 7. The
length is of the
shutter 17 is preferably minimized to reduce the distance required for the
shutter 17 to be
moved from the first position to the second position, which also reduces the
electrical power
required to move the shutter 17 in and out of the optical path and improves
the speed of the
switch 1. Again, to block incoming optical signals completely, the shutter 17
should have a
length 15 greater than the width w~ of core 7. The width ws of the shutter 17
affects the
insertion loss in the reflected light path. Specifically. a thinner shutter 17
may lower the
insertion loss.
The.trench.can be.from approximately 8-40 ~m wide. Preferably, the trench is
approximately 12-20 ~m wide.
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The shutter can be from approximately 1-8 ~m thick, approximately 10-100 ~m
high,
and approximately 10-100 ~m long. The shutter can be made from any
sufficiently rigid and
light material. Preferably, the shutter can be between approximately 20 and 70
~m long.
Even more preferably, the shutter is approximately 2 ~m thick, approximately
30-40 ~m high.
and approximately 30-40 pm long. The shutter is also preferably made from
silicon. and as
already noted, a preferred reflective surface is made from Gold.
With continued reference to FIG. 1, the input waveguide 3 receives an optical
signal
(e.g., a WDM. DWDM, UDWDM. etc.) from an optical source 100 and guides the
optical
signal in the core 7 and along an optical path 2. The optical signal exits the
input waveguide
3 via an output facet 21 and enters the trench 15. Depending upon the position
of the shutter
17, the optical signal will either propagate across the trench 15 and enter
the output
waveguide 5 via an input facet 21, or strike and either reflect off coating 29
or be absorbed by
surface 140 of the shutter 17 (if no coating is present). Only in the former
case will the
optical signal continue to propagate and be guided by the core 7 of the output
waveguide 5
along that waveguide's optical path.
With continued reference to FIG. l, the actuator 33 of the switching element
130
controls the movement of the shutter 17 between the first and second
positions. Movement of
the shutter 17 may be in virtually any direction (e.g., along a plane parallel
with or
perpendicular to the bottom surface 150 of the trench 15), so long as that
movement provides
the ability either to prevent or permit the optical signal from entering the
output waveguide 5.
For example, FIGS. 1 and 2A depict a first embodiment of the switching element
130 having
a shutter 1? that is movable along a plane generally parallel with the plane
of the bottom
surface 150 of the trench 15 and in a direction generally indicated by arrow A
(FIG. 1 ).
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Another embodiment is depicted in FIG. 2B in which the shutter 17 is movable
along
a plane generally perpendicular with the bottom surface 150 of the trench 15
and in a
direction generally indicated by arrow B. The movement direction of the
shutter 17 is not
critical, provided that the shutter 17 is movable into and out of the optical
path 2 defined
between the input waveguide ~ and the output waveguide ~. When positioned in
that optical
path ?, the optical signal will reflect off or be absorbed by the shutter 17
and will not enter the
output waveguide ~. When positioned out of that optical path 2, the optical
signal will
traverse the trench 1 ~ and enter into the output waveguide ~. Movement of the
shutter 17 by
the actuator 133 may be in response to a control signal input to the actuator
133. That signal
may be electrical, optical, mechanical, or virtually any other signal capable
of causing the
actuator 133 to respond.
Actuator 133 is joined to shutter 17 by link 110 and serves to shift the
shutter 17 into
and out of the optical path 2. While any suitable actuator could be used to
implement the
present invention, either an electrothermal or electromechanical type actuator
is preferred.
Electrothermal actuators are generally known in the art, and therefore will
not be
described in precise detail. For the purposes of this invention, it will be
appreciated that any
electrothermal actuator could be used which sufficiently changes its size in
response to the
application of thermal energy (which, it will be appreciated, could be
generated by applied
electrical energy). One benefit to using electrothermal actuators is that such
actuators may be
latching-type devices, i.e., one that maintains its position without the
continuous application
of energy. This means that if suitably constructed, the actuator, once
switched to one of two
positions, will remain in that position until it is switched to its other
position.
An exemplary electrothermal latching-type actuator 233 suitable for use with
the
present invention is depicted in FIG. 4. That actuator 233 includes a flexible
member 34
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which is securely fixed at endpoints 3~. 3~' to the walls of a cavity 37.
Cavity 37 is of a size
sufficient to allow the movement of flexible member 34. Also provided is a
heater 39, which
is located in relatively close proximity with the member 34. When the heater
39 is driven, the
member 34 warms and expands. Since the member's ends are secured at endpoints
3~, 3~',
the member 34 cannot simply expand so that the endpoints shift outward.
Instead,
compressive stresses will be generated along the member's length. These
stresses increase
until they reach a level sufficient to cause the member 34 to change its
position to that
indicated by reference character D. Thus, when the heater 39 is caused to heat
(e.g., by the
application of current through contacts (not shown)), the flexible member 34
also will be
warmed and caused to move between an ambient position, indicated by reference
character C,
and a flexed position, indicated by reference character D. Alternatively, the
member 34
could itself be the heater.
An electrostatic actuator may also be used to selectively move shutter 17.
Benefits of
electrostatic actuators include high operating speed, low energy consumption,
and minimal
system heating. One type of electrostatic actuator 333 usable in connection
with the present
invention is depicted in FIG. 5. That actuator 333 includes electrodes 41, 41'
located on
opposite sides of a piezoelectric element 43 made from a material which
expands in at least
one dimension (i.e., width or length) when an electric field is applied
thereto. Consequently,
by applying an electric signal to electrodes 41, 41', an electric field is
generated and
piezoelectric element 43 will expand in the direction indicated by arrow E
thus imparting
movement to the shutter 17.
It is possible that one actuator alone may not be sufficient to provide the
required
amount of movement for the shutter 17. This can be rectified by providing a
piezoelectric
actuator 433 such as that depicted in FIG. 6, which includes a number of
interlaced fingers
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4~. These fingers are attached to a support 20 within actuator 433. which
serves to prevent
unwanted motion of one side of the fingers 45. When an electrical signal is
applied to
electrodes (not shown) of the actuator 433 depicted in FIG. 6, the total
displacement in the
direction of arrow F of endpoint 47 will reflect the displacements of each of
the fingers 4~.
Since the displacement of endpoint 47 is the sum of the fingers' individual
displacements, a
significant movement of the shutter 17 can be achieved. This type of
electrostatic actuator
433 may require the application of substantial voltage, possibly on the order
of 100 V, to
obtain the desired movement of the shutter 17. Despite the magnitude of this
potential. very
little power is required, since the current flow through the electrostatic
actuator 433 is
negligible.
Referring again to FIG. l, each of the waveguides 3 and 5 have an associated
index of
refraction determined, at least in part, by the material from which the
waveguide core 7 is
constructed. The associated index of refraction for the waveguides 3 and 5 are
approximately
equal to each other, and is a value of approximately 1.45 for the silica
platform. The medium
120 provided in the trench 1 ~ also has an associated index of refraction that
may be different
than the waveguide refractive indices. If the medium is air, for example, its
refractive index
is 1.00. When an optical signal experiences different refractive indices as it
propagates,
certain characteristics of that signal may be caused to change as a result of
the different
indices. For example, when an optical signal experiences different refractive
indices as it
propagates, part of the optical signal (in terms of optical power) may be
reflected back into
the input waveguide and along optical path 2. That reflected signal can
propagate back to the
source and cause it to destabilize. Also, the optical signal may experience a
phase shift when
it passes from a material having a first refractive index to a material having
a second and
different refractive index. In some cases, that is the desired result. For an
optical switch, it is
preferable that the optical signal not experience any significant change in
its optical
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characteristics as it is guided along and switched by the various components
that make up the
switch.
To overcome the undesirable effects of the differing refractive indices, the
present
invention controls the distance between the output facet 21 of the input
waveguide 3 and the
input facets 21 of the output waveguide 5 so that the optical signal
propagates too short a
distance for the difference in refractive indices to introduce anv significant
change in the
optical signal characteristics. Thus, even though the optical signal
completely traverses the
trench 15 (from input waveguide 3 to output waveguide 5), the optical signal
does not
experience any significant adverse affect due to the difference in the medium
and waveguide
respective refractive indices.
Another aspect of the present invention compensates for optical return loss
caused
when an optical signal passes between materials having different refractive
indices. The
difference in refractive indices may cause part (in terms of optical power) of
the optical signal
to be reflected and propagate backward along the input waveguide optical path
2, for
example. That reflected signal can disadvantageously reflect back to and
possible destabilize
the optical signal source. By angling the output facet 21 with respect to the
respective
waveguide's optical path, (see, e.g., FIG. 1), any reflected signal is
directed away from the
waveguide core 7 and toward the cladding 9a or 9b, thereby preventing the
reflected light
from interfering with the optical signal being guided by and propagating in
the input
waveguide 3. In an embodiment of the present invention, the output facets 21
may be
disposed at an angle of about 5° to 10°, and more preferably,
about 6°-8° to minimize the loss
of light reflecting back into the input waveguide at the waveguide/trench
interface (this is
optical return loss (ORL)). For the preferred case of 6°, the shift
against coaxiality mentioned
earlier ranges from 0.2 ~m for a 5.0 ~m trench to 1.7 ~,m for a 35 ~m trench.
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In another aspect of the present invention. optical return loss may be further
minimized by applying an antireflective coating (not shown) on the waveguide
facets 21. The
antireflective coating can be single layer or a multilayer structure. Such a
coating can reduce
reflection at the waveguide-trench interface from 3.5% to below 1 % over a
large range of
wavelengths. The materials and thickness forming the antireflection coating
layers are
identical to those used in thin film technology. For example. the best single
layer
antireflection coating layer between a silica waveguide and a trench at the
wavelength of 1.~~
~m has an refraction index of 1.204 and a thickness 322 nm.
In yet another embodiment, optical return losses may be minimized by using a
combination of an angled interface and an antireflection coating.
Another aspect of this invention relates to the shape of the waveguides 3 and
5 used to
direct light to and from the switch 1. According to this aspect of the
invention, and as shown
in FIGS. 1 and 7, a tapered neck region 51 is provided on at least one of the
waveguides 3 and
5 so that the waveguide width tapers to a smaller cross-section at a location
49 remote from
the trench 15. Tapered neck 51 helps to reduce the diffraction of light in the
trench. By way
of non-limiting example only, in the region of the trench 15. the waveguide
width may be in
the range of approximately ~-15 Vim. That width may taper to a range of
approximately 4-10
~m at the remote location 49. These dimensions, it will be appreciated, are by
way of
example, and other dimensions also might fall within the scope and spirit of
the present
invention.
Tapered neck region 51 provides a smooth transition as the optical signal
propagates
along and is guided by the waveguides 3 and 5. Tapered neck ~ 1 confines the
light traveling
through the waveguide, in accordance with known principals of waveguide
optics, and greatly
reduces the transition loss which would otherwise occur where light passes
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waveguides having different dimensions. This is in contrast to the attenuation
which would
occur at a sudden transition from one width waveguide to a different width
waveguide.
Various taper rates could be used, depending upon the particular
considerations of a
given installation.
Switches in accordance with the present invention can be assembled using a
flip-chip
manufacturing technique as indicated in FIGS. 8A and 8B. In flip-chip
manufacturing. the
waveguides 3 and 5 and trench 15 are formed on one chip. and the shutter 17
and actuator 33
are formed on a different chip. Prior to assembly, the two chips are oriented
to face each
other. registered so that corresponding portions of the chips oppose one
another. and then
joined.
Alternatively, in another embodiment of the present invention, the optical
switch 1
may be constructed by monolithically forming the switching element 130 and
waveguides 3
and 5. In such an embodiment, the various parts of the optical switch 1 are
formed on a
single substrate 13 through the selective deposition and removal of different
layers of material
using now known or hereafter developed semiconductor etching techniques and
processes.
One of the benefits of monolithic fabrication is that it avoids the need to
register the different
components before the two substrates are joined
Referring next to FIGS. 9A and 9B, both a flip-chip and monolithically formed
optical
switch 1 in accordance with the present invention are there respectively
depicted. Both
figures also depict connection of the optical switch 1 to external optical
components such as.
for example, optical fibers 67, such that waveguide cores 7 optically connect
with fiber cores
65. Each optical fiber 67 is supported by a grooved member 69, and secured in
place using a
.fiber lid 63. A glass cover 61 protects the underlying switch components.
Alternative ways
of securing the optical fibers, or of using other light pathways, also could
be used.
16
WO 01/48532 CA 02392467 2002-05-23 PCT/US00/32164
One difference between the two fabrication techniques is the location of the
switching
element 130: above the waveguides for flip-chip and within the substrate 13
for monolithic.
It should be understood that this invention is not intended to be limited to
the angles,
materials. shapes or sizes portrayed herein. save to the extent that such
angles, materials.
shapes or sizes are so limited by the express language of the claims.
Thus. while there have been shown and described and pointed out novel features
of
the present invention as applied to preferred embodiments thereof. it will be
understood that
various omissions and substitutions and changes in the form and details of the
disclosed
invention may be made by those skilled in the art without departing from the
spirit of the
invention. It is the intention, therefore, to be limited only as indicated by
the scope of the
claims appended hereto.
It is also to be understood that the following claims are intended to cover
all of the
generic and specific features of the invention herein described and all
statements of the scope
of the invention which, as a matter of language, might be said to fall there
between. In
particular, this invention should not be construed as being limited to the
dimensions,
proportions or arrangements disclosed herein.
17
