CA1193477A

CA1193477A - Fixing substrate for optical fibers

Info

Publication number: CA1193477A
Application number: CA000396798A
Authority: CA
Inventors: Tetsuya Yamasaki; Takashi Kishimoto
Original assignee: Nippon Sheet Glass Co Ltd
Current assignee: Nippon Sheet Glass Co Ltd
Priority date: 1981-02-24
Filing date: 1982-02-23
Publication date: 1985-09-17
Also published as: GB2141256B; GB2097550B; FR2500642A1; FR2500642B1; GB2097550A; GB8414914D0; GB2141256A; FR2545617A1; DE3206600A1

Abstract

ABSTRACT THE DISCLOSURE
The substrate structure is designed such that a base plate of silicon single crystal is provided with at least a first groove for a lens of the graded index type and a second groove for an optical fiber. The base plate has a surface corresponding in plane to the {100} plane of the single crystal, and the grooves have the side walls corresponding in plane to the {111} planes thereof. This structure is given with high accuracy and with ease and permits a high accurate and easy assembly of the optical fiber and the lens.

Description

- 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~ ~

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 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 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 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~

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 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 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 ~.~

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.

.~ ~ ~

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.

Claims

WHAT IS CLAIMED IS:

1. A substrate structure for coupling an optical fiber and a lens of the graded index type comprising a base plate of silicon single crystal having a surface corres-ponding to a {100} plane thereof with a first groove and a second groove formed on said surface so as to have the side walls corresponding to the {111} planes thereof, said first groove being constructed so as to position said graded index type lens on the side walls thereof, said second groove being constructed so as to position the optical fiber on the side walls thereof and said first groove being formed so as to bring the axis thereof in discord with the axis of said second groove.

2. The substrate structure according to Claim 1 wherein said first groove differs in width and depth from said second groove.

3. The substrate structure according to Claim 2 wherein said first groove and said second groove have each a V-shaped or an outwardly broadening square U-shaped cross section.

4. The substrate structure according to Claim 3 wherein said first groove is formed so as to have the cavity thereof communicating the cavity of said second groove thereof.

5. The substrate structure according to Claim 3 wherein said first groove on said second groove is constructed so as to have the side walls thereof in linear contact with the respective outer peripheral surfaces of said lens of the graded index type or said optical fiber, respectively.

6. The substrate structure according to Claim 2 wherein said first groove is formed so as to have the cavity therof communicating with the cavity of said second groove,

7. The substrate structure according to Claim 6 wherein said first groove or said second groove is constructed so as to have the side walls thereof in linear contact with the respective outer peripheral surfaces of said lens of the graded index type or said optical fiber, respectively.

8. The substrate structure according to Claim 2 wherein said first groove or said second groove is constructed so as to have the said walls thereof in linear contact with the respective outer peripheral surfaces of said lens of the graded index type or said optical fiber, respectively.

9. The substrate structure according to Claim 2 wherein said surface of the silicon single crystal is provided with a third groove.

10. The substrate structure according to Claim 9 wherein said third groove may be in plural number.

11. The substrate structure according to Claim 10 wherein said third groove is formed so as to have the cavity thereof communicating with the cavity or said first and second grooves.

12. The substrate sturcture according to Claim 11 wherein said third groove has a V-shaped or an outwardly broadening square U-shaped cross section.

13. The substrate structure according to Claim 11 wherein said third groove is constructed so as to bring the axis thereof in substantial registration with the axis of said first or said second groove.

14. The substrate structure according to Claim 13 wherein said third groove is formed so as to have the side walls thereof in linear contact with the outer peripheral surfaces of said lens of the graded index type or said optical fiber, respectively.

15. The substrate structure according to Claim 13 wherein said third groove is formed so as to be kept free from contact with said lens of the graded index type or said optical fiber.

16. The substrate structure according to Claim 11 wherein said third groove is constructed so as to bring the axis thereof in discord with the axis of said first or said second groove.

17. The substrate structure according to Claim 16 wherein said third groove is formed so as to have the side walls thereof in linear contact with the outer peripheral surfaces of said lens of the graded index type or said optical fiber, respectively.

18. The substrate structure according to Claim 16 wherein said third groove is formed so as to be kept free from contact with said lens of the graded index type or said optical fiber.

19. The substrate structure according to Claim 11 wherein said third groove is formed so as to have the side walls thereof in linear contact with the outer peripheral surfaces of said lens of the graded index type or said optical fiber, respectively.

20. The substrate structure according to Claim 11 wherein said third groove is formed so as to be kept free from contact with said lens of the graded index type or said optical fiber.

21. The substrate structure according to Claim 10 wherein said third groove has a V-shaped or U-shaped cross section.

22. The substrate structure according to Claim 10 wherein said third groove is constructed so as to bring the axis thereof in substantial registration with the axis of said first or said second groove.

23. The substrate structure according to Claim 10 wherein said third groove is constructed so as to bring the axis thereof in discord with the axis of said first or said second groove.

24. The substrate structure according to Claim 10 wherein said third groove is formed so as to have the side walls thereof in linear contact with the outer peripheral surfaces of said lens of the graded index type or said optical fiber, respectively.

25. The substrate structure according to Claim 10 wherein said third groove is formed so as to be kept free from contact with said lens of the graded index type or said optical fiber.

26. A device comprising a substrate structure, a lens of the graded index type, and an optical fiber;
said substrate structure being of a base plate of silicon single crystal with a surface corresponding to the {100} plane thereof and having a first groove and a second groove formed on said surface so as to have the side walls corresponding to the {111} plane thereof;
said lens being positioned on the side walls of said first groove;
said optical fiber being positioned on the side walls of said second groove; and said lens being connected to said optical fiber so as to have the axis of said lens in discord with that of said optical fiber.

27. The device according to Claim 26 further comprising a third groove on the surface of said base plate so as to communicate the cavity thereof to said first and second grooves and means for switching the transmission of light transmitted from said optical fiber and then from said graded index type lens, said means being mounted in said third groove.

28. The device according to Claim 27 wherein said means for switching the transmission of light is a prism .

29. The device according to Claim 27 wherein said means for switching the transmission of light is a mirror.

30. The device according to Claim 26 further comprising a combination with more additional sets of the substrate structure of Claim 26 on which said lens and-optical fiber are fixed so as to transmit light from one set of said structure to the other sets by switching the transmission of light in varying paths.

31. The device according to Claim 26 further comprising a matrix switch connecting said substrate structure containing said lens and optical fiber to a matrix of switch elements.