JPS62204213A - Optical coupler - Google Patents

Abstract

PURPOSE:To convert the stress direction of a fixing part into a direction independent of optional coupling and to prevent the efficiency of optical coupling from reduction due to fixing by fixing a base with a prism through a fixing board. CONSTITUTION:In a device for executing optical coupling of an optical waveguide 2 formed on the base 1 with the external by the prism 3 pressed against the optical waveguide 2, the prism 3 is fixed on the base 1 through the fixing board 4. Polyester resin, soldering or laser welding is used as a more concrete fixing means, the gap between the bottom of the prism 3 and the optical waveguide 2 is kept as it is or filled with transparent resin or transparent grease and a material having linear expansion coefficient almost equal to that of the prism 3 is used as the material of the fixing board 4. Consequently, the prism 3 can be rigidly fixed and stabilized against external force and vibration, the positional shear at the time of fixing can be easily reduced as <=1mum and the reduction of the coupling efficiency can be neglected. Since the gap between the prism 3 and the optical waveguide 2 is not almost changed in spite of temperature change and stable optical coupling can be attained.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to the fields of optical fiber communications, optical applied measurement and control, and optical information processing.

Prior Art FIGS. 4 and 5 are a side view and a front view showing the prior art. 4 and 5, the bottom surface of the prism 3 pressed onto the optical waveguide 2 formed on the substrate 1 and the substrate 1 are bonded using epoxy adhesive or ultraviolet curing resin. Fill with agent 11,
After adjusting the air gap to obtain the highest optical coupling efficiency, it was cured and the prism 3 was fixed. Also,
Adhesive 12 was also applied to the sides of the prism 3 for reinforcement.

Problems to be Solved by the Invention In the conventional technology, the gap between the prism and the optical waveguide changes due to contraction and expansion when the adhesive 11 hardens, making it impossible to correct and reducing the optical coupling efficiency. It became. Furthermore, since the device is fixed with adhesive, the optical coupling efficiency fluctuates due to external force, vibration, and temperature, which has been a problem.

Means for Solving the Problems In order to solve the above problems, the optical coupling device of the present invention performs optical coupling between the optical waveguide provided on the substrate and the outside using a prism pressed against the leading waveguide. The optical coupling device is characterized in that the prism is fixed onto a substrate via a fixing stand. More specifically, it is characterized by using polyester resin, soldering, or laser welding as the fixing means, and the gap between the bottom surface of the prism and the optical waveguide is left as is, or is made of transparent resin or transparent resin. The present invention is characterized in that it is filled with grease, and that a material having a coefficient of linear expansion approximately equal to that of the prism is used as the material for the fixing base.

Since the working prism and the substrate are fixed via the fixing plate, the prism is firmly fixed and stable against external forces and vibrations. Additionally, polyester adhesives have a shrinkage rate of 0 when cured.
．． There are 1 to 0.2%, and the positional deviation during fixation is 1
A diameter of less than μm can be easily obtained, and there is no problem with a slight decrease in coupling efficiency. In addition, soldering allows quick fixing, and readjustment is possible by raising the temperature.

Furthermore, fixation using laser welding can achieve fixation in seconds or less, making it possible to achieve extremely quick and firm fixation. In addition, by filling the gap between the prism bottom surface and the optical waveguide with transparent resin, it is possible to prevent foreign particles from entering the part of the gap where optical coupling takes place, and reduce light scattering loss. Acts as a layer of protection over a period of time. Also,
By filling the voids with transparent grease, no stress is created in the voids of the prism, and dust is prevented from entering.
It also has the effect of reducing light scattering loss. moreover,
By using a material for the fixed base whose coefficient of linear expansion is approximately equal to that of the prism, the gap between the prism and the optical waveguide hardly changes even with temperature changes, and stable optical coupling can be achieved.

Embodiment FIGS. 1 and 2 are a side view and a front view showing a first embodiment of the present invention. For the sake of explanation, sapphire is used for the substrate 1, and a PLZT-based WI film is used for the optical waveguide 2.
An example of using this material is described below.

As the prism 3, a GaP right angle prism 3 having a refractive index of 3.3 was used. The edge of the prism 3 is pressed against the optical waveguide 2, the gap 8 formed between the bottom surface of the prism 3 and the optical waveguide 2 is adjusted, the input light 〇 is focused, and it is applied to the vicinity of the edge, and the waveguide in the prism 3 is focused. When the light was incident at an angle θ of 40.7 degrees, it was guided into the optical waveguide 2 as guided light 7. The gap 8 and the beam incidence position were adjusted, and the fixing table 4 was fixed to the substrate 1 at the time of maximum coupling efficiency, and then fixed to the prism 3. void 8
The dimensions are prism 3N! This can be determined by measuring the interval between fringes caused by interference between the surface and the optical waveguide 2. As the material of the fixing base 4, soda glass was used. The fixing is done by the fixing part 5a,
Both 5b are made of polyester resin (Technovit 400
0 (registered trademark), manufactured by Kultur GmbH, West Germany, shrinkage rate during curing is 0.1 to 0.2%), and was completely cured in about 15 minutes. Almost no change in the voids 8 was observed during curing.

This is because the shrinkage rate of the resin during curing is extremely small at 0.2% or less, and because the fixing base 4 is fixed to the prism 3 from the side and is fixed from both sides simultaneously, the stress is balanced and the prism It seems that the tilt of 3 and the ups and downs of prism 3 are gone. Note that the direction of the coordinate axes is shown at the bottom of the figure.

FIG. 3 is a side view showing a second embodiment of the invention. In FIG. 3, the bottom surface of the prism 9 is a pure color,
In the experiment, a pure color twill wire 10 of 85° was pressed against the optical waveguide 2, and the incident light 6 was focused and applied to this part. In the case of this prism 9, by adjusting the optical coupling efficiency by adjusting the gap angle ε1 on the guided light 7 side, higher efficiency can be obtained than in the case of the prism 3 of the first embodiment. In the case of this prism 9 as well, as in the first example, there was almost no change in the gap distance and gap angle ε1 before and after fixing. Therefore, almost no variation in optical coupling efficiency was observed.

As other fixing methods, we also tried soldering and laser welding.

In the soldering method, a copper block was used as a fixing base, In was vapor-deposited on the fixing base and the fixing surface of the GaP prism, and the prism was preheated and alloyed. Then, as shown in FIG. 1, after adjusting the prism position, the fixing part 5b between the fixing base 4 and the substrate 1 is fixed with polyester resin, and then a hot wire is applied to the fixing part 5a between the prism 3 and the fixing base 4. , In solder was melted and soldered. Almost no positional displacement due to soldering was observed.

In addition, it is possible to easily solder by forming a highly adhesive thin metal film such as chromium or gold on the surface of the prism, fixed stand, substrate, etc. by vacuum deposition or sputter deposition, and then applying solder plating to this. can be attached,
Therefore, the number of types of materials that can be used for joining increases.

In laser welding, glass or metal is used as the fixing base material, and after adjusting the prism position, the fixing base is placed in contact with the substrate and the prism, and the laser beam is focused on the fixing part 5b with the substrate to perform welding. Welding was performed by focusing a laser beam on the prism and the fixing part 5a of the fixing table. Q switch Y for light source
An AG laser was used. There was almost no change in the prism gap due to fixation, and the change in coupling efficiency was less than 0.5 dB. In the case of laser welding, unlike in the case of soldering,
Although it cannot be repaired, it is the most solid fixation possible, and provides the most stable connection against external forces and vibrations.

In addition, dust from the outside may enter the gap between the prism bottom surface and the optical waveguide, causing scattering of the guided wave light seeping out, resulting in a decrease in optical coupling efficiency. In order to prevent this, the gap was filled in advance with a transparent epoxy resin or ultraviolet curable resin, fixed, and then the resin was cured.

Almost no changes were observed in the prism gap due to contraction and expansion due to curing, as the prism was fixed in advance using a fixing table, and the scattering of the optical waveguide was reduced, resulting in a slight decrease in loss. Furthermore, the refractive index change due to curing was slight, and the change in light coupling efficiency could be suppressed to 0.5 dB or less. In addition, when we conducted a similar experiment by filling the void with transparent grease instead of resin, a stable bond was obtained, and the change in bonding efficiency due to fixation was almost the same as when no grease was filled. there were.

Furthermore, we conducted experiments using a material with the same coefficient of linear expansion as the prism for the material of the fixing table. Specifically, when a fixing base was formed and fixed using GaP, which is the same material as the prism, it was confirmed that extremely stable optical coupling efficiency characteristics against temperature changes could be obtained.

In the description of this embodiment, the input section has been described, but it is obvious that the same effect can be obtained when the direction of the optical path is reversed, that is, for the output section.

In addition, although the PLZT-based thin optical waveguide has been explained, it is of course possible to use other optical waveguides such as Ti diffusion, proton exchange LiNbO3 optical waveguide, and Y
Optical waveguides such as IG thin film optical waveguides and glass optical waveguides,
It is obvious that the same effect can be obtained using prism materials other than aP.

Further, although glass, copper, GaP, and the like are used as the material of the fixing base, it is obvious that similar effects can be obtained with other materials. In addition, if the solder material or the material of the metal thin film for solder material can achieve the same effect,
It is obvious that the present invention is not limited to what is described in the examples.

Effects of the Invention According to the configuration of the present invention, by fixing the substrate and the prism via the fixing base, the stress direction of the fixed part is changed to a direction unrelated to optical coupling, thereby preventing a decrease in optical coupling efficiency due to fixing. Is possible. Therefore, it is possible to easily increase the optical coupling efficiency, which conventionally deteriorated significantly when fixing the prism. In addition, the rigidity of the fixed base is strong, so
Stable optical coupling can be obtained even against external forces and vibrations. Furthermore, by using a material with a coefficient of linear expansion similar to that of the prism material for the fixing base, there is almost no change in the prism gap due to temperature changes, and therefore extremely stable temperature characteristics of optical coupling can be obtained.

[Brief explanation of drawings]

1 and 2 are a side view and a front view showing a first embodiment of the optical coupling device of the present invention, FIG. 3 is a side view showing a second embodiment of the same device, and FIGS. Figure 5 shows the conventional &[
FIG. 2 is a side view and a front view showing a technical example of the invention. G... Substrate, 2... Optical waveguide, 3.9... Prism, 4... Fixing base, 5a, 5b... Fixing part, 6...
Incident light, 7... Guided light, 8... Gap, 10... Ridge agent Yoshihiroichi Morimoto ~ Kokujin encounter Figure 2 β-V cross Figure 3 Figure 4 Figure 5

Claims (1)

[Claims] 1. Optical coupling between the optical waveguide provided on the substrate and the outside,
An optical coupling device that performs optical coupling using a prism pressed against the optical waveguide, characterized in that the prism is fixed onto a substrate via a fixing table. 2. For fixing the fixed base and the prism, and the fixed base and the board,
The optical coupling device according to claim 1, characterized in that an adhesive made of polyester resin is used. 3. For fixing the fixed base and the prism, and the fixed base and the board,
Claim 1 characterized in that soldering is used.
Optical coupling device as described in section. 4. The optical coupling device according to claim 3, wherein a metal thin film is interposed when the fixing base and the prism and the fixing base and the substrate are fixed by soldering, respectively. 5. The optical coupling device according to claim 1, wherein the fixing base and the prism and the fixing base and the substrate are each fixed by laser welding. 6. The optical coupling device according to claim 1, wherein the gap between the bottom surface of the prism and the substrate is filled with a transparent resin. 7. The optical coupling device according to claim 1, wherein the gap between the bottom surface of the prism and the substrate is filled with transparent grease. 8. The optical coupling device according to claim 1, wherein a material having a coefficient of linear expansion approximately equal to that of the prism is used as the material of the fixing base.