JPS5863902A - Controlling method of optical waveguide - Google Patents

Abstract

PURPOSE:To obtain the uniform characterisics with high accuracy for an optical waveguide, by irradiating a laser beam to the waveguide and controlling the distribution of refractive index with the local heating of the waveguide. CONSTITUTION:An optical waveguide is formed by diffusing Ti to a substrate 1 of an LiNbO3 single crystal. The light of the He-Ne laser 2 is irradiated to the optical waveguide, and the two output beams are received by a silicon photodiode 3. Then powers P1 and P2 of both beams are measured, and at the same time the beam of a CO2 laser 5 is irradiated at the peak position A of the refractive index at the incident edge side of the optical waveguide. As the time of irradiation elapses, the curve of the refractive index is gradually flattened. Then a light beam 7 in the waveguide moves gradually toward the route shown by a dotted line, and accordingly the branching ratio P1/(P1+P2) is reduced to be set at a prescribed level. In the same way, the laser beam 5 is irradiated at the maximum point B of the refractive index at the output edge of the waveguide. Thus the control is possible for the distribution of the refractive index. In such way, the characteristics of an optical waveguide are made uniform with high accuracy.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to optical waveguides used in optical integrated circuits or optical switches, optical filters, optical mode splitters, and q-optical couplers each having an optical waveguide as a component. It concerns an effective adjustment method.

Optical integrated circuits are currently under research and development, and there are still many problems that need to be solved in order to put them into practical use. In particular, the precise control of element characteristics, the branching ratio of false pullers, and the demultiplexing of optical filters. Accurate control of the characteristics and operating voltage of optical switches is an important issue for practical use, and only through accurate control can optical devices with sufficient operating margins be manufactured. Ru. The branching ratio 0 branching characteristic t or operating voltage of the element is mainly influenced by the optical waveguide which is a component of the element.

More specifically, it depends on the refractive index distribution of the waveguide. When forming a leading waveguide by impurity diffusion, there is currently no way to control its waveguide characteristics.

The impurity diffusion conditions are determined by the impurity source amount, diffusion temperature, and diffusion time. However, since the waveguide characteristics change greatly due to slight differences in the refractive index distribution, sufficient reproducibility of the characteristics cannot be obtained from the viewpoint of practical use simply by controlling the diffusion conditions.

The present invention compensates for the aforementioned poor reproducibility.

The present invention provides a method for effectively adjusting the waveguide characteristics of an optical waveguide after its formation to achieve a practical level of uniformity. Specifically, energy beams such as laser beams are irradiated onto parts of optical waveguides, which are components of linear couplers, optical filters, and optical switches, to adjust the refractive index distribution by local heating. In addition, this adjustment method can improve the characteristics in one direction and at the same time uniformize each element to a desirable value (0).
? This enables a so-called motion trimming method that is performed while measuring in real time.

The uniformity of characteristics is extremely accurate.

Next, as an example, the adjustment of the branching ratio of a cross-linked wig will be explained based on FIGS. The cross base optical coupler 1 used as a sample is LiMbO
, about 4201 cTi was vacuum-deposited on a single-crystal substrate, and after forming a batten with a pattern width of 10 μm, it was heated and diffused at about 960°C for 6 hours. The solid line is the pattern of the Te1 vapor deposited film before diffusion, and the arrow 6 indicates the traveling direction of the light beam within the optical waveguide. Points A and B in the same figure are the highest points of Ti chain degree, and are also the highest points of IL and therefore the highest refractive index.When performing O-even roofing, the light of He-N laser 2 is used as the measuring light beam [at one end of the sample]. The two lights entering the optical waveguide and coming out from the other end are sent to the silicon photodiode 3, and each light power P is determined by the indicator number.

and Pitl1m are determined. While performing this measurement, the CO laser beam was adjusted to have a beam diameter of approximately 30 μm and a beam power of approximately 50 mm.
Irradiate the part that resonates with point A in Figure 2 on the incident end side. As the irradiation time t passes, the peak of the refractive index gradually becomes flat,
The optical beam in the optical waveguide gradually moves from the solid line path to the dotted line path in Figure 3, and the branching ratio of 1 (Pi/I's
+Pt) decreases along a change curve as shown by the solid line in FIG. Therefore, in one case where the branching ratio is adjusted to @aS, that is, P, to P, and 11 to l, it is necessary to set the impurity diffusion conditions in advance so that the branching ratio becomes 06 or more. 9. If undiffused T1 remains on the substrate, the T1 concentration in the substrate at the point M in Figure 2 increases due to laser beam irradiation, the peak of the refractive index becomes high, and the branching ratio Fi increases. In contrast, it rises as shown by the dotted line in Figure 4. It is also possible to perform nine laser beam adjustments. 00. used in this example. Race
(Wavelength 106μ!+1) is well absorbed by the optical waveguide, and the power indication of the measuring laser beam is not required, so it is suitable for adjustment. Although the irradiation point can be adjusted at other locations on the leading waveguide, such as point B in FIG. 2, point A is most effective. Although the laser has a relatively low output, it is also possible to increase the output to shorten the adjustment time.

Note that the present invention is not limited to the adjustment of the branching ratio of the crossed optical coupler as in the above embodiments, but is similar to that of the crossed cross-linked optical coupler.
Figure 6(a) shows the demultiplexing characteristics of an optical filter that separates light with wavelength λ and light with wavelength λ, and as shown in Figure 6(1), the TIC mode and TM mode are separated and synchronized. It can be applied in exactly the same way to adjust the operating voltage or extinction ratio in the case of an optical switch that switches the optical beam to either channel as shown in Figure (c). Also, as shown in Figure 6! The present invention is also effectively applicable to branch type and directional coupler type structures as shown in FIG. Smoothly control various characteristics of optical mode splitters, optical switches, etc., and with extremely high precision! It can be adjusted to In addition, since the adjustment method according to the present invention uses a motion trimming method, it is easy to automate for mass production.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of an apparatus for carrying out the adjustment method according to the present invention, and FIGS. 3 and 4 are diagrams for explaining one embodiment.
FIGS. 5 to 7 are ninth diagrams illustrating other embodiments. Here, 1 is the cross-type light power/Pura. 2 is a He-N laser for measurement, 3 is a silicon photodiode, number is an optical power indicator, 5 is a 00° laser for adjustment,
6 is the traveling direction of the light beam within the optical waveguide. F is the light beam inside the optical waveguide◎ Rhinoceros 1 [! 1 $41! ] 111in (111in)

Claims (1)

[Claims] (1) When a guiding waveguide is formed with a refractive index distribution formed by impurity distribution, irradiation with an energy beam causes local heating, locally adjusting the refractive index distribution of the optical waveguide, and creating a desired waveguide. Obtaining characteristics of optical waveguide (Dllll determination method 2) A method for adjusting an optical waveguide according to claim 1, wherein the energy beam is shielded from laser beam tear.