Note: Descriptions are shown in the official language in which they were submitted.
- 1 ~
FIXING SUBSTRATE STR~CTURES FOR FIXING OPTICAL FIBERS ~ND
LENSES, PROCESSES FOR PREPARING SAME AND DEVICES USING S~ME
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a fixing substrate
s~ructure for fixing an optical fiber and a lens, a process
for preparing the same and a device using the same.
2. Brief Description of the Prior Art
OpticaL devices such as optical connectors, optical
switches and the like are pLaying a significant role in communi-
cation through opticaL fibexs. For this purpose, a variety
of devices have ~een heretofore proposed. For e~ample, there
has been proposed a device in which the opposing tips of
optical ribers are relatively moved by mechanical means.
This device, however, has enccuntered problems with reliability
and with a lcss o~ light at the connecting portions. A technique
has also been proposed in which, using a lens of the graded
(reflective) index type, parallel light beams converted from
light transmitted from an optical fiber ,are tr~nsmitted into
a core of the optical fiber. This conventional technique,
however, requires an expensive me~al device for registering
the a~is of the optical fiber with the axis of the graded
index type lens or for registering the axes of the graded
inde~ type lenses. The registration of the optical fiber
with the graded inde:c type lens or of the graded index type
lens with the other requires e~tremely high accuracy. An
experimental technique has been applied to permit an accurate
registration in which the axis of the optical fiber is registered
5~ 1~ ~
-- 2 --
with the axis of the graded index type Lens one by one by
means of a manipulator or the like while light is incided
thereinto from one optical fiberO This technique involves
high expenditures and provides an extremely poor reproducibility.
The lens of the graded index type may be of a trans-
parent body in a rod form made of glass or a plastic material
having a parabolic distribution in reflective indexes, that
is, of the graded index type in which the reflective index
n at a portion in a cross section orthogonal to the axis
in a distance apart from the axis may be represented by:
n = nOsech( ~ r)
or in approximation by:
n = nO~1 - Ar )
where nO is the reflective index at the axis;
r is the distrance from the axis;
A is the reflective index constant; and
a is ~ positive constant.
The graded index type lenses are utilized in a wide field
of micro-optics for optical communication or of pattern treatment
utilizing a lens~
It has also been proposed to provide a multi-core
optical connecter of optical fibers capable of detachably
connecting a number of optical fibers with a good reproducibility
and a low optical loss. For example, there is proposed one
in which a precision-processed substrate is employed that
i5 provided with sectional V-shaped grooves by means of aniso-
tropic etching on the surface of silicon single crystal.
This procedure utilizes a photomask that can provide grooves
-- 3 --
with high accuracy so that it presents ~he advantages that
a number of ~he grooves with a V-shaped cross section can
be formed in high preci.sion with respect to shape and relative
geographical relationship between the grooves.
A multi-core optical connecter has also been proposed
in which a sectional V-shaped groove for fixing an optical
fiber is integrally formed with a sectional V-shaped groove
for a connecting pin on a common substrate in order to permit
an accurate connection betwQen plugs.
In each case, however, the conventional devices
encounter the disadvantages, for example, that dust will
be caused to adhere to end sur~aces of the optical fibers,
thereby resulLing in a space therebetween and an increase
in connecting loss.
OBJECTS AND SUMMARY OF THE INVENTION
A primary object of the present invention is to
provide a fixing substrate structure capable of permitting
registration of the axis of a lens of the graded index -type
with the axis of an optical fiber or of the axes of the graded
index *ype lenses with extremely high precision and with
ease and to provide a process for manufacturing such substrate
structure with the structure of the type capable of being
manufactured at low costs and with ease.
Another object of the present invention is to provide
a device using such substrate structure capable of being
assembled with ease and with high reproducibilityO
A further object o~ the present invention is to
provide an optical switch or an optical connecter capable
7~
~ 4
of registering the axis of the opt:ical ~iber with that of
the lens of the graded index ~ype with high accuracy, failing
to cause a connecting loss resulting from light di~fusion
even i~ ~here i~ a space between t:he opposing ends of the
lenses of the connecter~ and capable of being manufactur~d
with relative ease.
In accordance with one aspect of the present invention r
the fixing substrate structure for fixins the optic:al fiber
and the lens of the graded i.ndex type is made o~ sllicon
single crystaL and which has a surface in a ~100} plane thereof
with a first groove and a second groove co~mllnîcating each
other so as to have ~he side walls corresponding in plane
to ~111} plane thereofO
In accordance with another aspec~ of the present
i~vention, a process for manufacturing such fixing substrate
structure involves carrying out the aniso~ropic etching on
the sur~ace of silicon single crystal in the {100} plane
with an etching mask having a predetermined pattern formed
thereon. The anisotrop~c etching may be carried QUt with
a~ etchant such as an alkali or the like.
In accordance with a further aspec~ of the present
invention, a connecting device comprises a fixi~g sub~trate
str~cture having the surface in the {100} plane with th~
ixst and second grooves having the side walls in th~ {111} planes
a lens of the graded index tvpe connected to the side
walls o the first grcove and an optical ~iber connected
to th~ ~ide walls of the second groove, said lens and said
optical i~er connected at ~.heir ends to each other a5 necessary~
t7
- 5 --
In accordance with a still further aspect of the
present invention, a process for fixing a lens of the graded
index ~ype and an optical ~iber on such fixing substrate
structure of the invention involves fixing ~he graded index
type lens in ~he ~irst groove and the optical fiber in the
second groove and connecting the end por~ons o~ the lens
and of the optical fiber, when n~cessaryO
In acc~rdance with a still further aspec~ o~ ~he
present lnvention, the connec~$ng d~vice h~ving the con~truction
~f th~ type ~ha~ has b~en describea c~neisely hereinaboYe
and will be descrlbed ln detail hereinbelow is assembled
with a part for optical devicesO
BRIEF DESCRIPTION OF THE DRAWINGS
FIG, 1 is a pexspective view illustrating an embodiment
of the substrate structure in accordance with the present
invention~
FIGS. 2A and 2B are, respectively, a plan view
and a front vlew of the substrate structure of FIGr 1~
FIGS~ 3~ to 5At 7A and 8A are each a plan view
illustrating ~aryiny embodiments of substrate struc~ures,
respec~ively, in accordance with the present invention~
FIGS. 3B to 5B~ 7~ and 8B are each a ron* ~iew
of the suhstrate structures of FIGS. 3A t~ 8A respectively,
FIG. 6 is a perspe~tive view illustxating another
embodiment of the substrate structure in accordance with
the presen~ invention.
FIG5. 9A~ 9B and 9D are each a cross sectional
view illustra~ing the su~s~rate structures demonstrating
the steps of preparing the substrate s1:ructure in accordance
with the present invention~
FIG. 9C ls a plan view illustr~ting a pattern formed
the sl1bstrate structure of ~IG~ 9B.
~ IG~ 1OA is a plan view illustrating a basç plate
of silicon single crystal for ma~ufacturing ~he substrate
structure in accordance with ~he present invention.
~ IGS. 1OB and lOC are each a cross sectional view
illustrating the substrate structures demonstratin~ the steps
of manufacturing the substrate structure in accordance with
the pxesent invention~
FIG~ 1OD is a plan view illustrating the substrate
structure having a pattern on the substrate surface of FIG.
10C.
FIGS. 1OE to 1OG are each a cross sectional view
of the substrate structu.re illustrating the steps of m~m1f~turing the
substrate struc~ure in accordance with the present invention.
FIG. 11 is a cross sectional view illustrating
the base plate with a cross-sectional V-s~aped groove.
FIG. 12 is a perspective view illustrating the
base plate of FIG. 110
FIG.13 is a cros~ sectional view illustratlng the
state of a cxoss-sectional V-shaped groove wi$h a phvtoresist
layer immediately after the completion ~f the etching step.
F~GS. l~A and 14B are respec~ively a plan view
and a side view illustrating ~he ~ubstra~e structure in which
a graded index type lens and an optical fiber are ~ixed in
the cross-sectional V~shaped grooves formed in the ~ase plate
of FIG. 120
FIGS. l~C and 14D ar cross-sectional views illustrating
states in which the gr~ded index ~ype le~ls and the optical
fi3:er are fixed in the ~ross~sectic~nal V-shaped grooves fo:rmed
in the base plai:e of E'I~:;S. 14A and 14B, respectivelyI
~ IC;., 15 is a cross secti:nal view illustrating
a state in which the graded index l:ype lens or the optical
fiber is fixed in the respective cross=~s~c~ional V~shaped
groove formed in the substrate structure in accordance with
the present inve~tion.
FI~. 16 is a front view illustrating a state in
which a pair of the substxa es are connected so as for the
cross~sectionàl V-shaped grooves to form a square space ln
which thP gxaded index type lens or the optical fiber i5
~ixed.
FIG. 17 is a representation illustrating the passageway
of light through the op$ical fibers a~d the graded index
type lensesO
FIGS. 18 and 19 are each a representation illustrating
a variation ln the pa5sageway of light through a variat~on
~n a construc~ion of the deviceO
FIG. 20 is a representation ~llustrating a l~ser
diode genexating beams passing through a graded index type
lens and an op~ ical f iber .
FIG~ 21 is a plan view illustra~ing a matrix switch
using the connecting substrate s~ruc~ure in accordanee with
~he prese~t inven~ion.
, "~ "
~ 8 ~
FIG~ 22 is a represen~ation illustrating a device
in which a pair of the graded inclex type lenses are conn cted
to each other with ~hree light ~ibers ~ixed to ~he respec~ive
lenses.
FIG. 23 is a represen~ati~n ~llus~rating a variation
in cons~ruction in which a pair of the devices of FIG~ 22
are connected to each othex.
. FIG. 24 is a representati.on illustrating a ~tate
in which a plurality o the connecting devices are disposed
with half mirrors by which light or beams are changed in
dif~erent transmission paths~
FIGo 25 is a perspective ~iew illustrating an optical
switch in which khree pairs o~ ~he graded index type lenses
with the optical fibers connected thereto are fixed ~o the
respective cross-sec~ional V-shaped grooves formed in the
base plate and in which a prism is mounted in a thixd groove
formed so as to communicate the V-shaped grooves.
FIG. 26 is a plan view il~ustrating the optical
switch of FX~. 25.
FI~. 27 is a plan view illustrating an optical
swi~ch for a computer link.
FIG. 28 ls a cross-sectional view illustrating
the substr~te structure in which a groovc i5 in a U~shaped
cross section with an optical fiber or a graded index type
l~ns fixed so as to ~e in contact with ~he groove side walls.
FIG. 29 is a perspective view illustrating a substrate
structure for an op'cical connecter in accordance with the
present invention.
y~
~ ~1r ~r
- 9 -
FIGS. 30 and 32 are each a plan view illustrating
the optical connecter using the substrate of FIG. 29.
FIG. 3'1 is a cross~sec~i.onal view illustrating
the optical connecter of FIG. 30.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The substrate structure in accordance with the
presen~ inven~ion c~mprises a base plate of silicon single
crystal~ The silicon single crystal ~o be used for the base
plate may be prepared in substantially the same manner as
in the manufacture of silicon single crys~als ~or preparing
silicon wafers for integrated circuits or the like.
The base plate to be used for the fixing substrate
structure in accQrdance with the present invention is prepared
so as to have a surface corresponding to a {l00} plane .
of the silicon single crystal. The base plate is then
treated in a way as will be described in detail hereinbelow
to provide the surface with a predetermined number or combination
of grooves in such a manner that the grooves are formed to
have the side walls there~f corresponding to {lll~ planes
of silicon s.ingle crystal ~t a par~icular angle ~ with
resp~ct tQ the surface of ~he ~l00} plane ~hereof. The first
gro~ve i5 formed so as to co~ nicate the second groove.
I~ accoxdan~e wi~h use of ~he fixing substrate s~ruc~ure
of the present invention~ a third groove which may be single
or plural in number may be formed on the surface of the base
plate in associa~ion with or in ro~ nication to ~he firs~
and second gro~ve~. The first, second and third gr~oves
may vary in depth and width from each other in accordance
~t ~ d~
- 1Q ~
with parts of optic~l devices Which are to be mounted therein
or therewith. In general, the first groove in ~hich a lens
of the graded lndex type is fixed is larger in width and
in depth than the ~econd gxoove .in which an op~ical fiber
is ~ixed. The third groove may have any ~arying relative
width or depth in accordance with use.
The grooves may be formed so as $~ ha~e the ~xis
of one o the grooves in substantial registr~tion with that
of the other of the groovesO It should be noted herein that
registration of the axis of one groove with that of the other
may contain~ for xample, an instance in which, where light
or beams are transmitted in a substantially straight direction,
the axls of an optical fiber is physically connected dixectly
or indirectly in correspondence to that of lens of the graded
index type, whether the optical fiber is bonded to or disposed
apar~ from the lens, and an instance in which~ where the
axis of the optical fiber does not physically correspond
~o that of the graded index type lens, tha~ is, where the
axis of the optical fiber is in physical ~iscord with that
of the lens~ light ox beams transmitted through the optical
f~ber are concen~rated or focused into ~he axis of another
opposlng optical fiber in different direc~ions and/or in
different passageways through one or more lenses of the graded
index type in which the light or beams transmitted from the
optical fiber are reflected.
Ref~rring to FIGS~ 1 and 2A~2B, there is seen a
base ~late 10 o~ silicon single ~rystal having a surface
12 ~orrespondlng to the {lOO} plane of the ~ingle
3ll~7t~
crystaln The base plate is provided on the surface thereof
with a first groove 14 and a second groove 16 in such a manner
that ~he firs~ groove is communicated to the second one and
tha~ the side walls thereof are formed in correspondence
to the ~ll} planes of the single crystal~ The first and
second groo~es may be in a V-shaped, U-shaped or any oth~r
suitable form in section. In this embodiment of ~he construction
of the grooves, the first groove is designed so as for the
axis thereof to be in registration with ox in correspondence
to that of the second groove such that the axis of a lens
of the graded index type to be mounted in the first groove
is regist~red with tha~ of an optical iber ~o the mounted
in the second groove, as will be desc~ibed hereinafter more
in detail.
The constructio~ and structure of the grooves to
be formed on the surface of the base plate may vary with
use of the substrate structure for a device. For example,
FIGS. 3A to ~A, inclusive, illustrate a variatio~ in
emhodiments o~ the construction or structure of the groo~es.
AS shown in FIGS. 3A and 3B, a ~irst V-shaped groove or vee
14 and a second V-shaped ox vee 16 are formed on the surface
of the bas~ plate 10 so as to brin~ the axis of the firs~
groove in discord with ~ha~ o~ ~he second groove. FI~S.
4A and 4B are another embodiment of the construction and
structure of the subs~ra~e structure in accordance wi~h the
present inven~ion. A first V-shaped gxoove or v~e 14 is
formed at the middle poxtion of the surface 12 of a base
plate 10, and three second V~shaped grooves or vees 16 are
,
3~7
~ 12 o
formed so as ~o communica~e the firs~ groove. The second
grooves may ~e axranged in varlous manner, for example, such
that ~wo of th~m are op~ically connecte~ ~hrough the firs~
groove to each other so as ~ bri.ng the axis of the one into
registration with that of ~he o~her. FIGS. 5A and 5~ i1lustrate
a still further embodiment of ~he substrate ~tructure in
accordance with ~he present invention. In this embodiment,
a third V-shaped groove or vee 1~ is formed b~ween a ~irst
sectional V-shaped groove 14 and a second sectional V-shaped
groove 16 so as to have the axis of the third groove corres-
ponding exactly to~that of the first and second grooves.
The width~ and dep~hs of the fixs~, secon~ and third grooves
may be descended in this order, Particularly where no part
for assembling an optical device in accordance with the present
invention is disposed in the ~hird groove, however, there
is no limitation on the shape or size of the third groov~.
It is also to be noted that the third groove may b~ disposed
outside th~ first and/or second grooves and that the wid h
and~or dep~h o~ the third groove may be varied. ~he third
groove may be composed of plural grooves. FIG. 6 shows another
embodiment of ~he cons~ruc~ion of the substrate structure
~n accordance with the present inven~ion t in which a ~irst
groove ~4 is in a fcxm with an equiangular semitrapezoid
5~ction or outwaxdly broadenin~ square "U'~shaped s~ction,
that is ~ it is constructed such that the side walls 14a of
the fir5~ groo~e 14 correspond each to the {lll}planes of
silicon singLe crystal and the bottom portion 14b th~reof
is flat and parallel to the surface 12 of the base plate.
13 ~
It is, of course, to be noted that a second groove 16 may
be formed so as to have an outwardLy broadening square U-shaped
section or any other suitable section and, further, that
the shape of the grooves may he varied as long as the side
walls thereof correspond to the (111) plane of silicon single
crystal.
In accordance with the present inventionl the number
of combinations or sets of the first and second grooves may
be varied with use of a device resulting from the base plate
on which the first and second grooves are formed. For example,
FIGS. 7A and 7B illustrate an embodiment of the construction
of the grooves in which three pairs of the first groove 14
and the second groove 16 as shown in FIGS. 1 and 2A - 2B
are formed on the surface 12 of a common base plate 10 of
silicon single crystal. FIGS~ 8A and 8B illustrate another
feature of the construction of grooves on the base plate
in accordance with the present invention. In this embodiment,
six sets of a first groove 14 and a second groove 16 are
formed on the surfaces 12 of the base plate 10. Furthermore,
each two sets of the first and second grooves are communicated
to each other so as to have the axis of the first set in
registration with that of the second set and further to connect
the end portion of the second groove 16 of the first set
to the opposing end por-tion of the first groove 14 of the
second set~
In accordance wtih the present invention~ ~he grooves
may be formed on the surfacP of the base plate of silicon
single crystal in various manners. For example, FIGS. 9A
3~
- 14
to 9D illustrate an ~x~ent of form;ng grooves on the surface of
the base plate of silicon single cxystal, As sho~n in FIG. 9A, a ~ase
plate 10 to be used for the s~strate structure is prepared by cutting
silicon single crystal alcng a {100~ p~ne thereof and polishing the
surface 12 to give a flat surface. It is herein to be noted that the
{100~ plane referred to herein means any plane selected from (100) 1
(010), (001), (100), (010) and (001) p~nes of silicon singLe crystal.
In similar fashion, it is to be noted that the~ p~e m~s any
p~ne selected from (111), (111), (111), (111), (111), (111), (111)
and (111) planes of silicon single crystal,
Referring now to FIGS. 9B and 9C, the base plate
10 is cleansed and then provided over a whole area of its
flat surface 12 with a SiO2 layer 20. On the surface of
the SiO2 layer is formed a photoresist layer 22. The photoresist
layer ~2 is then covered over a whole area of the surface
with a masking layer 24 of material such as chromium or the
like. The mas~ins layer 2a has a pattern 32 with a first
groove Pattern portion 14A and a second groove pattern portion
16A corresponding respectively to the first groove 14 and
the second groove 16. The photoresis~ layer is then exposed
through the masking layer to light, and the exposed portions
o~ the photoresist layer 22 are removed with the SiO~ layer
20 by meâns of the etching technique using hydrofluoric acid.
The treatment with hydrofluoric acid does not corrode the
surface 12 of Si single crystal base plate 10 so that the
groove portions corresponding to the first and second groove
pattern portions 14A and 16A, respectively, are formed as
shown in FIG. 16A and the rest of portions where no grooves
are formed is covered with the layers consisting the SiO2
layex 20, the photoresist layer 22 and the mask 24.
- ~5 -
FIGS. 10A to 1OG show another embodimen~ of forming
grooves on the surface of a base pla~e 10 of silicon single
crystal~ As shown in FIG. 1OA, the base plate for the substrate
structure in accordance with the invention is prepared by
~utting silicon ~ingle crystal so as to have a surface 12
corresponding to the {lO~} plane ~hereof and an orientation
flat 10A corresponding to the ~llO} plane thereof, Over
a whole area of the surace is formed a l~yer of Si3H4 layer
26 as an etching mask as shown in FIG. 19B, ~or example~
by means of the reduced pressure CVD method by flowin~ a
gas mix~re of SiH2C12 and NH3 while heating ~he base plate
at 750C to 900C. The etching mask 26 may ~e formed by
different techniques such as the plasma CVD method. On the
e~ching mask 26 is then coated, as shown in FIG. 10C, a photo-
resist layer 2B (or example, trade mark: AZ-13050J; S~ipley
Co.~ in conventional manner. The photoresist layer 28 is
provided, ~s shown in FIGS. 1OD and 1OE, with a photomask
30 having a given pattern 32 comprising a pattern portion
32A capable of being permeable to light and a pattern portion
32B incapable of being permeable ~o light~ The photomask
30 has a reference pattern 34 for positioning the base plate
10 50 as to regis~er ~.he orientation fiat 10A of ~he base
pla~e with ~he reference p ttern. Referring now ~o FIG.
1OF, the photoresist la~er 28 is exposed to light to form
a pa~tern corresponding ~o the firs~ and second grooves,
The pattern so formed is then developed~ and the pattern
p3rtion 32A is removed so as ~o expose ~he surface of the
etching mask 26 in substantial corxespondence to a pattexn
for the first and second grooves and so as to cover ~he res~
of the surface of the etching mask with the pho~oresist layer
28~ The photoresist layer works as an etching protective
lay~r. ~he etchin~ is then carried out ~y means of th~ plasma
etching technique under a high-frequency electric field (for
example, 13~5 MHz) while flowing, for example~ CF4, whereby
the etching mask 26 is removed in corxespondence to the openin~s
formed on the photoresist layer. The photoresist layer is
then remove~ to leave the etching mask 26 with the predetermined
pattern on the base pl~e.
The base plate 10 having the layex with the predeter-
mined pattern as sh~wm in FIG~ 11 is then subjected to the
aniso~ropic etching step with an etchan~ such as an alkali
solution, for example, a KOH aqueous solution or a NaOH aqueous
solutlon. Referring now to FIGS. 11 and 12, the anisotropic
etching gradually corrodes the surface of the silicon single
crystal exposed to the etchan~ so as to form a groove having
the side walls corresponding in plane to ~he {ll~ planes
thereof at particular angle ~ with the respect to the tl00} plane
thereof~ Thi~ anisotropic etching is effected by utilizing
the principle that the {lll} planes ~f silicon single crystal
are hardly etch~d with-~he etchant so ~hat a difference arises
in a speed of etching be~ween the ~l00} and {lll} planes.
Where ~he e~ching is effected to a final stage, ~he corxocion
of the crystal surface at t~e angle e proceeds to form a
groove with a V shaped sec~ion and the etching will not proceed
any 1Gn~er when the V~shaped section is completed. Where
the e~c.hing is ~erminated in ~ shorter period o time ~han
\
~ 17 ~
i~ proceeds to completiGn, there is given a groove wi~h a
square "U"~shaped cross sec~ion~ tha~ is, a groove with the
side walls corresponding to ~he {lll} planes of the silicon
single crys~al a~ the angle ~ with respect to ~he {l~O} plane
thereGf and with a fla~ bottom surface in ~he ~lOO} plane
~hereof, as shown by dot~dashed lines in FIG~ 11. This technique
enables the etched surfaces to be extremely flat and smooth~
In the anisotropic etching process, an etchant such as a
50 mol ~ ~ydraz ine ~2H~ 3 aqueous solution may also be use~.
After the anisotropic etching process is completed, the layer
or layers that can protect ~he surface of the base pla~e
from being etched are removed~ for example, by means of the
plasma etching technique.
It i~ to be noted that ~he angle H corresponds
to the {lll} plane with respect to the [lOO} plane
i~ remained constant at 54.74~ regardless of the depth of
the groove~ Where a groove with a larger cross section is
intended ~o be formed t a pattern to be formed on a photoresist
layer ox any other layer disposed on the base plate is simply
rendered larger so as to correspond to ~he intended wid~h
of the groove.
As shown in ~IG. 13, however, it is ~o be no~ed
that a width 2W of the flrst or second groove 14 or 16 is
wide~ than a wid~h ~W' of ~he pa~tern portio~ 14A or 16A.
As a ratio of 2W3/~W remains constant where the etching condi~
tions are determined constan~ ~he width 2W' can be previously
determined when these condi~ions are t~ken into consideration.
In a laxge sca~e production process~ ît is preferable to
7
- 18 -
fix an op~ical fi~er bare filament coated with a secondary
nylon coat or the like in the sectional V-shaped groove of
the base plate.
The fixing substrate structure thus obtained in
accordance with the present invention is suitably adapted
to fix a lens of the graded index type to the first groove
formed on the base plate of siLicon single crystal and an
optical fiber to the second groove formed thereon, whereby
a device having a desired function is given. This device
may be connected to or associated with parts and/or devices,
whereby a device particularly suitable for optical communication,
such as an optical connector and an optical switch is given.
Referring to FIGS. 14A and 14B, a connecting device
for connecting a lens 36 of the graded index type and an
optical fiber 38 is seen to comprise the lens fixed in the
first ~r~o~.r~ 1a an.d the opt~a~ fi ~e~ fi:~e~ in the se~-nd
groove 16. The graded index lens is bonded at its end portion
to the opposing end o~ the optical fiber through an adhesive
layer 40. The lens and the optical fiber are also bonded
t t.heir side portions to the side walls of the respective
first and second grooves by means of adhesive 42. As best
shown in FIGS. 14C and 1a~ respectively, there are seen
the sta~es in which the graded inde~ type lens 36 and the
optical fiber 38 are connected on the side walls 14B and
16B of ~he first groove 14 and the second groove 16 formed
in the base plate 10.
Referring now to FIGS. 15, the registration of
the axis of the graded index type lens 36 with that of the
~r`3
1 9 --
optical fiber 38 in the X-axis direction is determined by
a dimensional accuracy of a pattexn 32 comprising a first
pattern portion 14A corresponding to the first groove 14
and a second pattern portion 16A corresponding to the second
groove, as best shown in FIGS. 9C and 1OD. The registration
with extremely high precision can be effected by forming
a masking layer by means of a known technique of forming
a thin layer with a pattern, such as a photoLithography technique
as adopted in the field of the manufacture of integrated
circuits or the like.
Wher~ the V-shaped groove 14 or 16 has a width
2W in the widthwise direction and side walls at the angle
9 with respect to the surface portion 12 of the base plate
10 and where the graded index type lens 36 in a rod form
or the optical fiber 38 having a radius r has the center
at a height h right above the surface plane 12 of the base
plate, the following relationship can be given.
h = sin 5 tan 9
In this equation, where r = rO, W - WO and h - ho, the width
W that gives h = ho when r = nrO can be given as follows:
W = (n - 1)rO/cos ~ + WO
As the anisotropic etching of silicon single crystal is caused
to occur at the particular angle ~ with respect to the surface
of the base plate, WO will become 66 microns where r - 60
microns and ho = 10 microns. When r = nrO - 7.5 x 60 = 450
microns) W that gives ho = 10 is 542 microns. Thus, where
the registration of the lens having a radius of O.9mm with
~.~
- 20
the optical fiber having a radius of 120 microns is conducted
so as to locate their axes at a height of 10 microns right
above the surface of the base plate, the masking on the base
plate is effected that has a pattern with a width of 1~084
microns for the first groove and with a width of 132 microns
for the second groove.
When h = 0, two base plates 10 having an identical
shape and size is connected to each other with the sectional
V-shaped grooves thereof in registration with each other,
and the graded index type lens 36 and the optical fiber 38
are fixed in the opening in a rhombic cross section of the
two grooves as shown in FIG. 16.
The connecting devices in accordance with the present
invention can be applied, ~or example, to the field of micro-
optics for optical communication. As shown in FIGS. 17 to -
~19, for examplet an incident light 4~A that passed through
a first optical fiber 38A is converted into parallel beams
42B in a lens 36A of the graded index type of a 1/4 pitch
length, and the parallel beams are transmitted to an opposing
lens 36B of the graded index type. In the s~cond lens to
which parallel beams are transmitted from the other lens,
the parallel beams are ocused as a single beam 42C into
an optical fiber 38B that is connected to the second lens.
The light or beam 42C is then transmitted through the second
optical fiber 38B to a desired locatîon. As shown in FIG.
18~ a half mirror 44 may be disposed between a first lens
36A and a second lens 36B opposing thereto. With the half
mirror, the parallel beams txansmitted from the first lens
~L~L~''it ~ 1~
are changed at a predetermined reflection angle in a different
direction and then received by a ~hird lens 36C~ thereby
being transmitted further as a slngle light or beam through
an optical fiber 38C. The light or beams having a wavelen~th
different from that of ~he light or beams reflected by the
half mirror is passed and transmitted to the lens 36B and
then to the optical fiber 38B. This construction of a combina-
tion of the graded index type lenses and the optical fibers
may be used for a T type coupler. As also shown in FIG~
19, a number of light attenuation plates such as metal layer
filters are disposed between the opposing graded index type
lenses 36A and 36B. In this construction~ light or beams
transmitted to an optical fiber 38A are transmitted through
the lens 36A and the light~attenwation plates (generally
referred to as 4~) to a lens 36B and an opkical fiber 38B
in substantially the same mode as shown in FIG. 17.
Referring now to FIG. 20, there is seen a connecting
device comprising the base plate 10 haviny a first groove
14 and a second groove 16 with a lens 36 of the graded index
type and an optical fiber 38 connected respectively to the
first and second grooves. In this embodiment of the construction
of the suhstrate structure in accordance with the present
invention, a third yroove 18 is disposed between the first
and second grooves 3~ and 38, respectively, and the lens
36 is not connected directly to the optical fiber 38. This
construction can also permit an efficient transmission of
light or beams. A Light emi~ting diode or a laser diode
S0 may be used as a source of light or laser beams.
Referring to FIG. 21, a matrix switch is seen in
which he substrate structure comprising four sets of a lens
36 of the graded index type and an optical fiber 38 fixed
in aliynment with each other on the base plate 10 is connected
to a matrix of switch elements 50.
Turning now to FIG~ ~2, a device is seen to comprlse
the substrate structure of FIGS, 6A and 6B in which the graded
index type lens 36D is connected in the first groove 14 through
a haLf mirror 52 to the lens 36E. The half mir.ror may be
formed by means of vacuum evaporation deposit technique or
the like. Two optical fibers 38D and 38E are fixed in the
second grooves 16D and 16E, respectively, and connected to
the lens 36D. Another optical fiber 38F is fixed in the
second groove 16F and connected to the lens 36E. In the
substrate structure of this embodiment, the two second grooves
16D and 16E are disposed each in a distance X from the axis
of the first groove 14 and parallel to each other, and the
other second groove 16F ~s disposed in a distance X from
the axis of the first groove 14 at the portion opposing to
and coinciding with the second groove 16E. This substrate
structure is designed such that mixed light beams transmitted
from the fixst optical fiber 38D are separated in accordance
with wavelengths by means of the half mirror 52~ The light
beams reflected by the half mirror are transmitted to the
second optical fiber 38E, and the light beams passed through
the half mirror 52 are transmitted to the third optical fiber
38F~ This structure may be used for a device for mixing
light or beams having different wavelengths.
- 23 ~
Reerring to FIG, 23, a device is seen to comprise
a first set o~ graded index type 1~enses 36F and 36G connected
to each other through a half mirror 52A and a second se~
of graded index type lenses 36H and 36I connected to each
other through another half mirror 52B. The first set of
the lenses is connected to the second set of the lenses such
that light or beams are transmitted from the one set to the
other set. A first single wave light havtng a wavelength
A1 is transmitted through the optical fiber 38G in-to the
graded index type lens 36F. A second single wave light having
a wavelength ~2 is transmitted through the optical fiber
38H into the graded index type lens 36H. A third single
wave light having a wavelength ~3 is transmitted through
the optical fiber 38I into the graded index type lens 36I.
The second single wave light is reflected by the half mirror
52B and combined with the third single wave that passed through
the half mirror 52B. The combined light is then transmitted
from the lens 36H into the graded index type lens 36G and
reflected by the hal mirror 52A. The mixed light reflected
by the half mirror 52A is combined with the irst single
wave light that passed through the half mirror 52A and then
tra~smitted into a fourth optical fiber 38J as a mixed light
having wavelengths ~ r and ~3. This structure may be
assembled to an internal reflective type multiple device
in a relatively easy manner.
Referring to FIG. ~4, a device is seen to comprise
three sets of a connecting device with half mirrors disposed
in a path of 1iyht or beams~ The device is designed such
that light beams having wavel~ngt~s ~ 2 nd ~3 passed
through graded index type lenses 36K, 36L and 36M from optical
fibers 38K, 38L and 38M are reflected by mirrors 52A, 52B
and 52C, respectively, in aecord~nee with ~heir wavelengths,
and transmitted through a graded index type lens 36P into
an optical fiber 38P and such that fourth light beams having
a wavelength ~4 passed through a graded index type lens 36N
fxom an optical fiber 38N is transmitted through the mirrors
52A, 52B and 5~C into the lens 36P and the optical fiber
38P~ Conversely, mixed light beams having wavelengths ~1~
and ~ transmitted through the lens 36P from the optical
fiber 38P can be separated into the lenses 36K, 36L~ 36M
and 36N as the single wave ligh~ having the wavelengths ~
~2~ ~3 and ~, respectively. The lights having the wavelengths
and ~3 axe respectively separated and transmitted by
the mirrors 52A, 52B and 52C, and the light having the wavelength
is transmitted straight through int~ the lens 36N and
the ~pti~al f iber 38N, as shown by arrows in dot~dash lines
in FIG. 24.
Referring now to FIGS . 25 and ~6 0 an optical switch
is seen to comprise three sets of graded index type lenses
(generallyreI'erred to as ~6) and op~ical fibers ~generally
referred to as 38). The lenses 36 are fix~d in the first
grooves (generally referred to as 14) and ~he optical fibers
38 are fixed in the second grooves (generally referred to
as ~ 6 ~ ~, The base plate 10 is also provided with a thixd
g.roove 1~ with th~ side walls 18A~ corxespo~ldirlg t9 the ~lll} planes
of silicon slngle crystal arld with the bottom surface
- 25 ~-
18B flat and parallel to the surface of the base plate.
The third groove is mounted with a switching means such as
a right prism 54~ Referring further to FIG~ 26, light or
beams transmitted into the optical fiber 38Q is transnlitted
through the lens 36Q of the graded index type to the prism
54 that can change the direction of the light into a direction
opposite at an angle of 360 by causing reflection twice
at a right angle and transmit the twice refLected light to
the adjacent lens 36R and the optical fiber 38R connected
thereto. Where the prism 54 is moved to a different location,
for example, as shown by dot-dash lines in FIG. ~6, the light
transmitted to the optical ~iber 38Q and the lens 36Q can
be transmitted into and reflected twice by the prism 54 to
a direction opposing at an angle of 360. The light is then
transmitted thxough the lens 36S into the optical fiber 38~.
Turning to FIG. 27, an optical switch for a computer
link is seen to comprise four sets of graded index type lenses
36T to 36W, inclusive, and optical fibers 38T to 38W, inclusive,
and a pair of mirrors 56A and 56B~ The lenses and the optical
fibers ar~ fixed in the xespective first grooves (generally
referred to as 14) and in the respective second grooves (genera-
lly referred to as 16), and the mirrors are mounted in a
third groove 18 formed in the middle portion of the base
plate 10 so as to co~municate the first and second grooves.
In the optical switch of this type, light transmitted through
the optical fiber 38T and the lens 36T is transmitted into
and reflected twice at an angle of 90 by the mirror 56A.
The reflected light is transmitted in o -the lens 36U and
~ L~
the optical fiber 38U and then in~Q an optoelectric transduce.r
~8 and a terminal 60. The signa:L is then transmitted into
an electroopti al 62 and converted into ligh~ that is in
turn transmitted into the optical fiber 38V and the lens
36V. The light transmitted from the lens 36V is then reflected
twice at an a~gle of 90 by a mirror 56B and transmitted
into the lens 36W and the optical fiber 38W. The computex
link that uses the optical switch of the type shown in FIG.
27 permits a transmission of signals by means of one optical
fiber from the center station into a plurality of sub-stations.
A conventional comput~r link o~ the close~ loop system is
caused to stop when one or more sub-stations get out of order.
The optical switch of the type as shown in FIG. 27 can alleviate
khe drawbacks encountered in the conventional computer link.
For example, where a system comprising the optical fiber
38U and the lens 36U gets out of order, the mirrors 56A and
56B are moved away to give way to the light transmitted from
the lens 36T directly to the lens 36W.
Referring to FIG. ~8~ the base plate 10 is seen
to have a grooYe 14 or 16 with the side waLls 14A or 16A
inclined corresponding to the {lll} planes of silicon single
crys~al and ~he bo~tom surface ~ ox 16B flat and parallel
to the suxface o the base plateO In the first or second
grDove 1 4 or 16 is fixed a lens 36 o~ ~he graded index type
or an optical fiber 38 in such a manner that the lens or
the optlc~l fi~er i5 in linear c~ntact with the side waLls
14A or 16A with the bottom portion thereof free from contact.
.~ ~ ~
- 27 -
Referrins then to FI~S. 29 to 32, inclusive, an
optical connector is seen to contain an optical bare fiber,
a lens or Ine graaea index ~ype ana an op~ical coa~ fiber
fixed in the respective grooves formed on the base plate
of silicon single crystal. As best shown in FIG. 29, the
base plate 10 is provided with a predetermined number of
the first grooves 1a for the lenses, the second grooves 16
for the optical bare, fibers, the third grooves for the optical
coated fibers and the fourth grooves 64 for connecting the
base plate to another base plate. Turning now to FIGS. 30
and 31, there is seen an optical connector which is designed
such that the base plate 10 having the structure as described
hereinabove is provided with the lenses 36 of the graded
inae~ type fixed i.n the respective first groove 14, the optical
bare fibers 38 fixed in the respective second grooves 16,
.
and the o~tical coated fibers 66 fixed in the respective
third grooves 18. The respec~ive grooves 14, 16 and 18 are
formed so as to communicate each other and register their
axes with each other. In this embodiment, the grooves are
designed in an outwardly broadening "U~-shaped form; however,
it should be no~ed that the shape of the grooves is not rest-
ricted thereto as have already been described hereinabove.
Referring to FIG. 32, there is shown a device in
which a pair of the optical connectors of FIGS. 30 and 31
are connected to each other with the graded inde~ type lenses
36 cpposed in contact with each other. The op~ical connectoL-s
may be connected together by placing a common connecting
pin 68 in the fourth groove 64 formed usually at the both
7~9
- 2~
sides of -the base plate 10 and then inserting the pin into
a covering plate (not shown) for fixing the both end portions
of the pin and the base plates with screws (not shown) or
any other suitable means. It is also possible to mount a
covering plate (not shown) and form an opening between the
underside of the covering plate and the respective groove
of the base plate into which a common connecting pin is inserted
and fixed with a spring (not shown). The free end portion
of the connecting pin may be inserted into another opening
formed on the other base plate and covering plate connected
to each other in the same manner.
The present invention permits simplification of
the substrate structure for fixing and connecting an optical
fiber and a lens of the graded index type with high precision
and with ease. An application of a conventional technique
for forming a thin layer pattern to the formation of grooves
on a base plate of silicon single crystal enables a highly
accurate and easy provision of the grooves in which the optical
fiber and the graded index type lens are fixed. These advantages
presented by the present invention further enable an assembly
of the substrate with other parts for an optical device with
extremely high precision and with ease.
