JPS58174905A - Optical waveguide and converging device - Google Patents

Abstract

PURPOSE:To enable disposition of respective elements by emitting convergent light from the end face of a substrate, and spacing the waveguide surface and a focus thereby preventing the emission to the same direction as the direction of the light except the convergent light and selecting the space on the waveguide freely. CONSTITUTION:The light 22 diffracted in a substrate by a diffraction grating 13 in a substrate is diffracted as convergent light 23 to the focus in the outside part of the substrate by a diffraction grating 14. The pattern of the grating 14 in this case corresponds to the interference pattern of the light 22 in the substrate and the light 23. Part of the light 22 is refracted by an end face 15 and is transmitted through the substrate. The direction thereof differs from the direction of the light 23 and only the convergent light can be drawn out. If the space of the grating 13 and the lattice vector thereof are so selected that the diffracted light is totally reflected on the end face 15, the light that is transmitted through the substrate by the end face 15 can be eliminated. The diffraction grating of high efficiency which refracts the primary diffracted light only to the the substrate side without emitting the same into air and prevents the emission of the diffracted light of high order to either of the substrate and the space is formed, by selecting properly the spaces of the grating 13 and lattice vector.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention provides a waveguide light converging device (nil) that extracts light from a flat plate optical waveguide to the outside and converges it.

[Technical background of the invention]

As a method of converging light from an optical waveguide to the outside using a diffraction grating, as shown in FIG. A diffraction grating 3 is used to direct the guided light 4 from the waveguide surface directly to the outside (
There are two ways to converge. One of the objectives of the Jin-like method is to integrate the optical system of the Jin-C2 disc head used as the head of an optical audio disc or an optical video disc.

[Key points of background technology]

However, with the method shown in the IS1 diagram, when reading recorded information at high density, such as in the case of optical discs, in order to reduce the spot size at the focal point 5 of the convergent light 4, it is necessary to use the diffraction grating area. The distance between the waveguide surface and the disk surface must be small compared to the size of the waveguide, and the space on the waveguide surface becomes free and cannot be used. In addition, in the method shown in Figure 1, the diffracted light is emitted to the top surface of the waveguide (and the diffracted light is also emitted to the second substrate side), so it is difficult to use a substrate of 1 kdi. The reflected and leaked light causes a decrease in the output δ S and X in the same direction as the convergent light.

[Purpose of the invention]

*The purpose of the invention is to separate the output surface of the convergent light from the waveguide surface (2) and to introduce a waveguide light converging device that eliminates the above drawbacks4.
There are two.

[From & j1o summary] Not @ni! A waveguide light converging device using Al2 is configured such that the guided light is first guided inside the substrate (2) by a first diffraction grating C2, and then guided by a second diffraction grating formed on the end surface of the substrate, and then guided by -It is biconvergent.

[Embodiments of the invention]

Embodiments of the present invention will be described below with reference to drawings showing various embodiments.

FIG. 2 shows an embodiment of the present invention.

In the figure, 11 is a dielectric substrate, and 1 is #I, which has a refractive index higher than that of the substrate.
#Electric waveguide layer, 13 is the 10th diffraction grating with δ formed on the waveguide, 14 is the substrate edge dii 15 (= second diffraction grating that was not formed. In this example, the guided light 4 is Although the diffraction grating 13 is a diffraction grating composed of groups of equally spaced lllll beams, the present invention can be applied even when the guided light is not parallel light, or when the diffraction grating openings are groups of curved lines at non-uniform intervals. Example Q and C: If the diffraction grating on the waveguide surface is a diffraction grating with equally spaced straight lines, it has the advantage of being easy to manufacture.Here, the propagation constant of light in vacuum used for this optical waveguide is The effective propagation constant of the waveguide "Jt, 21 is N, the refractive index of the substrate 110 is O, , - the grating spacing of the diffraction grating 130 is A.

The traveling direction of the guided light! The angle between the grating vector of the diffraction grating 13 (thick cram is 2t/A) and the
X-m of the propagation vector of the m-th new party by 3 people” 5l
It is given by ncl. If the sum of the Δ squares of these two components is smaller than kn-, the guided light 4 is - of the substrate 11.
It is diffracted into the air, and it is also diffracted into the air if it is smaller than the nani/goose. Therefore, the following condition km"<ke"N"-2"koN-", 400
1α10(9)"<ke"ns"... If you choose A and α so as to satisfy ■, the first-order diffracted light will only be on the substrate side (the second-order diffracted light will not go out into the air. The condition of ■) (= addition 4 times (2), it is possible to prevent the higher-order diffraction light higher than 2nd order from exiting to either the substrate side or the aerial feeder.
It becomes possible to form a diffraction grating with high efficiency.

Inside the base of the diffraction grating 13 (the light n that has been twice diffracted is the diffraction grating 1
4, the light n becomes convergent at a focal point 244 outside the substrate and is folded once. In this case, the pattern of the diffraction grating I4 is an interference pattern between the particle n in the substrate and the convergent light n (2 corresponds to -). Therefore, if the end face of the substrate is x@42, the phase g of the interference pattern is that of YEN. It is given as a function by the following equation.

・・・・・・・・・・・・ ■ When the diffraction grating 14 is used as a phase mirror, the phase is given by The area of Ω〉O is 1゜COtΩ
(Rather than setting it to 0 in the O area) (It's more leverage to turn.

11111ffi15 (In general, a part of g22 from inside the substrate is refracted and transmitted. Since the direction is different from the direction of the convergent light A, it is possible to extract only the convergent light.6) If the rigid refractive grating 13 (DA and α) are bent at an angle f66 such that the diffracted light is totally reflected in the substrate edge direction 15, the source of transmission at the end face 15 can be eliminated.11I42all In the embodiment shown in , this condition is given by the following equation.

′-! -eos4! , > ko(N −v' *knee 1) ・------... ■A, α is ■*'21s
Satisfying all of the conditions (2) is cIJ' wt:. k(70.6328 am″″”* na=1-2
1.46. In the case of N-1, 53, the region that satisfies all the conditions of tDe and ■ and in which the diffracted light is emitted in the positive direction of X is indicated by region 31 in FIG. In this region, the grating spacing is in the range of 0.3 μm to 0.78 mO. This is a value that can be produced using a holographic method or the like. If we decide that the condition (2) is not satisfied, the area will be expanded to the part that can be shown by the friend. In actual fabrication, the structure shape of the diffraction grating 130 is selected from M
Since the allocation can be made low, high efficiency can be obtained even with a lattice spacing of a V area.

[Effect of enlightenment]

As explained above, in the waveguide light converging device according to the present invention, by emitting the convergent light from the end face of the substrate, the waveguide direction and the focal point can be placed at a separate place, and the space on the waveguide can be freely used. This makes it possible to arrange each element. It also has the advantage that light other than convergent light is not emitted in the same direction.
Applications include heads of digital audio disks, waveguide-fiber couplers, etc.

[Brief explanation of drawings]

Fig. 1 is a diagram showing a conventional waveguide light converging device, Fig. 1i42 is a diagram showing an embodiment of the present invention, and Fig. 3 is a diagram showing the angle l of the first (b) folded grating and the grating interval in the present invention. It is a diagram for explaining the relationship between the following: 11... n' @ body substrate substrate 12... Dovetail housing waveguide pigeon 13... $1O diffraction grating 14... Second fighting grating 21 ... Guided light... Convergent light...
...Focus representative Patent attorney Noriyuki Chika (one person) Figure 1? ! ff 22 15

Claims (4)

[Claims] (1) An optical waveguide consisting of a single plate and a dielectric waveguide with a high p refractive index formed on the electric substrate with δ formed in its direction.
forming a diffraction grating inside or within the boundary of the waveguide layer, in which the guided light is emitted to the outside of the optical waveguide and converged to a single point outside the four waveguides; and (2) forming a second diffraction grating consisting of unequal interval curves #l# at the end of the substrate. A waveguide light converging device characterized in that the second diffraction grating causes the generated light to be twice diffracted δ outside the substrate and converged δ. (2)゛ The optical waveguide 6; the propagation constant of the light used in vacuum is kO, the effective propagation constant of the guided light is @N, the refractive index of the substrate is 0, and the grating of the 10th diffraction grating is When the spacing is A, and the angle between the grating vector (direction is the grating and its own weight) of the refractory grating and the propagation direction of the guided light is α, then A, α
is the condition jc, "(ko"N"-2・keN-", 4 cot
A temporary light convergence device according to the patent claim OMFMa1, characterized in that it satisfies the following: a. (3) Said light guide 1! What is the propagation constant in vacuum of the source used for the IL path, what is the actual propagation constant of the conduction a, and what is the effective propagation constant koN?The refraction index of the substrate is n, and the grating spacing of the first diffraction grating is A. , when the angle between the grating vector (direction is perpendicular to the grating line) of the - folded grating and the traveling direction of the guided light is α, then A
, a is the condition @INshi4- is @N4eosα+k +) / lc
Claim 1, characterized by:
Waveguide light collection device with term distribution. (4) The first diffraction grating (=A such that the particles diffracted into the substrate satisfy the total reflection condition at the output end face 42 where the second diffraction grating is formed. 112. The uniform wave light converging device according to claim 111, further comprising the first o-th diffractive grating.