JPS6051683B2 - thin film optical lens - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a thin film type optical lens comprising a dielectric layer and a metal layer.

For this type of thin film optical lens, for example, a dielectric layer with a relatively high refractive index is laminated on a dielectric substrate with a relatively low refractive index, and the dielectric layer is partially layered to form the desired thin film optical lens. A structure is known in which the structure is removed by etching.

However, in the thin-film optical lens created in this way, the etched side surface, that is, the lateral boundary surface, has boundary irregularities on the order of the wavelength of light, and this poor surface precision causes a large light scattering loss, resulting in light transmission. It was difficult to obtain a good rate. The present invention aims to alleviate these drawbacks, and includes a first dielectric layer having a relatively large refractive index formed on a dielectric substrate, and a layer laminated on the first dielectric layer. This is achieved by a structure in which a second dielectric layer having a relatively small refractive index and a metal layer having a desired pattern are laminated, and will be described in detail below with reference to the drawings. FIG. 1 is a plan view showing an embodiment of the present invention, and FIG. 2 is a sectional view taken along the X-Y direction of FIG. 1.

In FIGS. 1 and 2, 1 is a dielectric substrate with a relatively low refractive index, 2 is a first dielectric layer with a relatively high refractive index,
3 is a second dielectric substrate having a relatively small refractive index, 4 is air, 5 is a metal layer, and 6 is an incident light beam. Coupling of the input and output light with the incident light beam 6 in the first dielectric layer 2 can be performed via prism couplers 7a, 7b, 7c. Also, nl, n2, n3, n. , H are the optical refractive indexes of the materials of the dielectric/heavy substrate 1, the first dielectric layer 2, the second dielectric layer 3, the air 4, and the metal layer 5, respectively. In this example, a SlO2 substrate, an Al2O3 layer, a SiO2 layer, and an A1 layer are used as the dielectric substrate 1, first dielectric layer 2, second dielectric layer 3, and metal layer 5, respectively, and SiO
2. High frequency sputtering method (or C.V.D.
method or other method) to heat the Al2O3 layer 2 to several thousand amperes or
A few μm of the film was deposited, and then a SlO2 layer 3 of several thousand amps was deposited using the same method, and then an A1 layer 5 of several thousand amps was deposited using a mask evaporation method (
Alternatively, the film may be deposited by a photo-etching method after vapor deposition, etc.).

With this structure, the equivalent refractive index of the first dielectric layer 2 in contact with the metal plate 5 via the second dielectric layer 3, that is, the equivalent refractive index of the first dielectric layer 2 in the region A is approximately 1.6
04 and the first dielectric layer 2 in the B region in contact with the air 4
The equivalent refractive index of is approximately 1.636, and a refractive index difference occurs in the first dielectric layer 2 according to the pattern of the metal layer 5.

By creating this refractive index difference, for example, on a normal optical concave lens shown by the pattern of the metal layer 4 in FIG. 1, a focusing lens is formed in the first dielectric layer 2 for the incident beam light 6. can do. With the structure of this embodiment, it is easy to manufacture, the ohmic loss of the metal layer is small due to the effect of the second dielectric layer, and the light scattering loss at the boundary surface in the direction of light propagation is small, resulting in light transmission. A thin film optical lens with low loss can be obtained. Next, by providing the second dielectric layer 3 on the first dielectric layer 2,
The reason why the optical transmission loss in the first dielectric layer 2 is reduced will be described.

Temptation. The relationship between the light propagation constant β and the light attenuation constant α in the electric body 2, the film thickness T2 of the dielectric body 2, and the film thickness b of the dielectric body 3 is well known, with b=0. (For example, AppIiedOpt
ics first? No. 5 A. (Reisjnger) can be expressed as the following equation as an extension of the relational equation. Here, γ4
=1, γ32=1, γ53=1 (for TE mode)
γf ÷ γ32: ÷ γ534, etc. (for TM mode)
, λo is the wavelength of light in vacuum, ε1, ε2, ε3
, ε4, ε5 are wavelengths λ.

The dielectric constant of each substance of the dielectric substrate 1, dielectric layer 2, dielectric layer 3, air 4, or metal layer 5, that is, the thickness of the thin film dielectric layer that becomes the optical transmission path, and b is the intermediate insulating layer. 3 thickness, N is the order of light, Nl, n2, rl3, rLi, n
5 is a dielectric substrate 1, a dielectric layer 2, a dielectric material for λo,
This is the refractive index of each substance of layer 3, air 4, or metal layer 5. The materials of the dielectric substrate 1, dielectric layer 2, dielectric layer 3, and metal layer 5 are SlO2, Al2O3, and SiO, respectively.
2. As AI, refractive index is n1=1.48, n2=1.68
, n3=1.48, T111. =1.2-J7. The thickness of the dielectric layer 2 is 3000A, the thickness of the dielectric layer 3 is 3000A, and the lateral width of the cutout part of the metal 5 is 6.5 μm.
In this case, the amount of attenuation for the TEO mode propagating light is
It becomes about 4 dB/Crn, which is 85 dB/c when the dielectric layer 3 is not provided! This is a huge improvement compared to RL.

In addition to the prism coupler 7, coupling of input and output light with the incident beam 6 in the dielectric layer 2 can also be achieved by forming a diffraction grating on the surface of the dielectric layer 2 and interfering with the incident beam 6. .

Alternatively, an active layer such as a semiconductor laser may be embedded in the dielectric layer 2. Further, in this embodiment, the case where a converging type lens is constructed has been described, but it goes without saying that the present invention can also be applied to a diverging type lens shown in FIG. 3 by forming the metal layer into an arbitrary shape.

Furthermore, as an application example of this embodiment, semiconductor lasers 8a and 8b are embedded in a large number of different positions in a thin film as shown in FIG.
, 8c can be condensed and efficiently detected by a photodetector 9 embedded in a thin film.
As explained above, according to the present invention, it is possible to reduce the scattering of light at the boundary surface where the difference in refractive index occurs and also to reduce the loss of transmitted light, so it has advantages such as high efficiency and easy manufacture.

[Brief explanation of drawings]

Fig. 1 is a plan view of an optical lens showing an embodiment of the present invention, Fig. 2 is a sectional view taken along the X-Y line in Fig. 1, and Fig. 4 is a diagram showing an example of application of this embodiment. be. DESCRIPTION OF SYMBOLS 1... Dielectric substrate, 2... First dielectric layer, 3... Second dielectric layer, 4...
Air, 5... Metal layer, 6... Incident beam light, 7... Prism coupler, 8...
- Semiconductor laser, 9... photodetector.

Claims (1)

[Claims] 1. A first dielectric layer having a relatively high refractive index laminated on a dielectric substrate having a low refractive index, and the first dielectric layer having a relatively low refractive index and laminated on the first dielectric layer. a relatively thin second dielectric layer that reduces loss of propagating light guided through a specific portion of the first dielectric layer, and a metal layer laminated on the second dielectric layer; A thin film optical lens in which the metal layer is formed in the cross-sectional shape of a lens with respect to an optical transmission path formed in the optical transmission path.