JPS6051085B2 - optical device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a thin film optical device, for example, a thin film optical device comprising a first dielectric layer, a second dielectric layer having a lower refractive index than the first dielectric layer, and a metal layer. Regarding transmission line equipment and others.

This type of thin film optical device, for example, as an optical transmission line device,
A structure is known in which a dielectric layer having a relatively high refractive index is laminated on a dielectric substrate having a relatively low refractive index, and the dielectric layer is etched and left along a desired optical transmission path.

However, in such an optical transmission line, the etched side surface, that is, the lateral boundary surface, has boundary irregularities on the order of the wavelength of light, so this poor surface precision causes a large light scattering loss, which increases the transmission loss in the optical transmission line. I was making it big.

Furthermore, when a light reflector or a light splitter was created with a similar structure, the efficiency was not good because the poor surface precision at the interface caused a large light scattering loss. As a method to improve this drawback, there is a method that attempts to achieve this by laminating a dielectric layer with a relatively large refractive index and a metal layer with a desired pattern, but it is still insufficient in terms of transmission loss. It was a lot.

The present invention aims to alleviate these drawbacks,
A first dielectric layer having a relatively large refractive index, a second dielectric layer having a relatively low refractive index laminated on the first dielectric layer, and a metal layer having a desired pattern are laminated. This has been achieved by the configuration, and will be described in detail below with reference to the drawings.

FIG. 1 is a plan view of an optical transmission line device showing an embodiment of the present invention, and FIG. 2 is a sectional view taken along the X-Y direction of FIG. 1.

1 and 2, 1 is a dielectric substrate with a relatively low refractive index, 2 is a dielectric layer with a relatively high refractive index, 3 is a dielectric layer with a relatively low refractive index, 4 is air, and 5 is a dielectric layer with a relatively low refractive index. is a metal layer,
Reference numeral 6 indicates an optical transmission path, and reference numeral 7 indicates an incident light beam. Coupling of the input and output light with the incident beam of light 7 in the dielectric layer 2 can take place via prism couplers 8a, 8b.

Further, Nl, n2, rI3, n4, and n5 are respectively a dielectric substrate 1, a dielectric layer 2, a dielectric layer 3, and an air metal layer 5.
is the refractive index of light of the substance. In this example, a SlO2 substrate, an Al2O3 layer, and an A1 layer are used as the dielectric substrate 1, dielectric layer 2, dielectric layer 3, and metal layer 5, respectively.
A high frequency sputtering method (or C.V.
D method or other method) to deposit the Al2O3 layer 2 of several thousand amperes, and then, like the dielectric material 2, deposit the SiO2 layer 3 of several thousand amperes by high frequency sputtering method (or C.V.D method or other method). Furthermore, the A1 layer 5 is deposited by a several-thousand-A mask evaporation method (or a photo-etching method after evaporation, etc.).

If the thickness of the dielectric layer 2 and the dielectric layer 3 are appropriately selected in such a configuration, the equivalent refractive index of the dielectric layer 2 at a position below the dielectric layer 3 in contact with the metal layer 5, i.e. The equivalent refractive index of the dielectric layer 2 in region A is lower than the equivalent refractive index of the dielectric layer 2 at a position below the dielectric layer 3 in region B, which is in contact with air 4, and an optical transmission path is formed. At the same time, a single propagation mode optical transmission line with low transmission loss can be obtained.

Note that a 3000A (7) Al2O3 layer was used as the dielectric layer 2, and a 3000A (7) SiO2 layer was used as the dielectric layer 3.
The lateral width of the missing part of the metal layer in Figure 2 is 6.5 μm.
m, the attenuation for TEO mode is 4dB/
It will be about CM.

Next, the reason why the light transmission loss in the dielectric layer 2 is reduced by providing the dielectric layer 3 on the dielectric layer 2 will be described.

The relationship between the propagation constant β of light in the dielectric 2, the attenuation constant α of light, the film thickness T2 of the dielectric 2, and the film thickness b of the dielectric 3 is well known with b=0 (for example, Applied Opti
cs Vol. 12 No. 5 A. (Reisinger)) The relational expression can be expressed as an extension of the following expression. Here, γ4
=1, γ3. = 1, γ53 = 1 (for TE mode), where λo is the wavelength of light in vacuum, ε1, E2, ε3
, j4, ε5 are wavelengths λ.

, the dielectric constant of the dielectric substrate 1, dielectric layer 2, dielectric layer 3, air 4, or metal layer 5, T2 is the thickness of the thin film dielectric layer that becomes the optical transmission path, and N is the order of light. , N
l, n2, n3, n4, t are λ. dielectric substrate 1 for
, the refractive index of each material of the dielectric layer 2, dielectric layer 3, air layer, or metal layer 5. The materials of the dielectric substrate 1, dielectric layer 2, dielectric layer 3, and metal layer 5 are SlO2,
As Al2O3, SiO2,,Al, the refractive index is n1=1
．． 48, n2=1.68, n3=1.48, n5=1.
2-J7. O, and wavelength 6328A(7)He-
The thickness of the dielectric layer 2 is reduced to 3000 mm using Ne laser light.
The thickness of the A1 dielectric layer 3 is 3000, and the lateral width of the removed portion of the A1 metal 5 is 6. ? If it is m, the legend of TEO mode”
The amount of attenuation for light dissemination is approximately 4 dB/C7rL, which is greatly improved compared to approximately 85 dB/Cm when the dielectric layer 3 is not provided. In addition to the prism coupler, the input/output light can be coupled with the incident beam 7 in the dielectric layer 2 by forming a diffraction grating on the surface of the dielectric layer 2 and interfering with the incident beam 5.

Alternatively, an active layer such as a semiconductor laser may be embedded in the dielectric layer 2. In addition, in the configurations shown in FIGS. 1 and 2, the larger the refractive index difference between the dielectric substrate 1 and the dielectric layer 2, the greater the equivalent refractive index difference between the A region and the B region in the dielectric layer 2. Since it becomes large, the dielectric substrate 1 may be removed and replaced with air.

As explained above, according to the present invention, the scattering loss of light at lateral boundaries/interfaces is small and the amount of attenuation for propagating light is small, so transmission loss can be reduced or efficiency can be increased, or it can be manufactured easily. It has the following advantages.

[Brief explanation of the drawing]

FIG. 1 is a plan view of an optical transmission device showing an embodiment of the present invention, and FIG. 2 is a sectional view taken along the X-Y line in FIG. 1.

Claims (1)

[Claims] 1. A first dielectric layer with a relatively high refractive index, a second dielectric layer with a relatively low refractive index laminated on the first dielectric layer, and a metal layer laminated on the second dielectric layer. 1. An optical device comprising a metal layer, wherein a cutout portion of the metal layer is formed corresponding to an optical transmission path to be formed in the first dielectric layer.