JPS5930026A - Light integrated spectrum analyzer - Google Patents

Abstract

PURPOSE:To make it possible to obtain a monolithic semiconductor, by providing a piezoelectric thin film surface wave transducer between both a collimation lens and a Fourier transformation lens, which are arranged on an As-S series thin film optical waveguide provided on a semiconductor substrate. CONSTITUTION:An As-S series thin film optical waveguide 12 is provided on a semiconductor substrate 11. A collimation lens 14 and a Fourier transformation lens 15 are sequentially arranged in the propagating direction 13 of light on the waveguide 12. A piezoelectric thin film surface wave transducer 17 is provided on the substrate 11 so as to cross the waveguide 12 at a right angle between both leses 14 and 15. In this case, e.g., a ZnO piezoelectric thin film is used as a constituting material of the transducer 17. A facing electrode 21 is provided between a piezoelectric thin film 18, on the surface of which a comb shaped electrode 19 is provided, and the substrate 11. In this way, e.g., monolithic integration of a semiconductor element such as a laser and an acoustooptic element can be formed on the substrate 11.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to optical integrated circuits. In particular, the present invention relates to the structure and materials of construction of optical integrated spectrum analyzers.

Conventional Structure and Problems The optical integrated spectrum analyzer is a type of acousto-optic device, and has conventionally been fabricated on a piezoelectric single crystal substrate such as LiNbO3. In this case, for example, an optical waveguide is formed by diffusing Ti metal into the surface layer of a L I NbO5 single crystal substrate whose surface has been polished, and a pair of geodesic lenses is formed by mechanically forming, for example, a recess on the waveguide. A surface wave transducer is formed by providing, for example, a comb-shaped electrode on the LiNbO3 substrate at a position perpendicular to the optical waveguide, and the light propagating through the optical waveguide between the pair of lenses. The purpose is to create a spectrum analyzer by interacting with the surface waves excited by the surface wave transducer.

That is, a surface wave was excited by a signal inserted into a comb-shaped electrode, and the guided light was passed through a geodesic lens for collimation, and the surface wave gave a spatial directional displacement according to the frequency of the signal. 1) a photodiode array placed at the focal point of a geodesic lens for Fourier transform; 2) the spectral distribution of the above signal is detected in real time. This device is highly accurate for inputs with unpredictable frequencies, such as short pulse signals, because conventional electrical spectrum analyzers sample input data at a sweep rate and process the signals serially. This eliminates the drawback that it cannot be processed using However, since a LiNbQ3 substrate is used, there is a drawback that it is essentially impossible to form a monolith with, for example, a ■-■ group semiconductor device.

Purpose of the Invention The inventors have succeeded in eliminating the conventional drawbacks by introducing a thin film multilayer structure substrate into this type of device,
Invented a new optical integrated spectrum analyzer.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a structure and materials for an optical integrated spectrum analyzer having a thin film multilayer structure.

Composition of the invention The present invention will be explained below with reference to the drawings.

FIG. 1 shows the main structure of an optical integrated spectrum analyzer according to the present invention. In the figure, the optical integrated spectrum analyzer according to the present invention includes a semiconductor substrate 11,
As-8 thin film optical waveguide 12 provided on the semiconductor substrate
A collimation lens 14 and a Fourier transform lens 15 are arranged in sequence in the light propagation direction 13 on the optical waveguide 12, and the substrate is perpendicular to the optical waveguide between the collimation lens and Fourier transform lens. Above, surface wave 1
In this case, the piezoelectric thin film surface wave transducer 17 consists of a piezoelectric thin film 18 and a comb-shaped electrode provided on its surface. It consists of 19. When an input signal from the outside is introduced into the comb-shaped electrode terminal 101, the surface wave 16 is excited, and for example, the collimation lens 14
After the light from the semiconductor laser 102 provided at the focal point is collimated, the spatial direction distribution is changed by the surface wave 16, and after passing through the Fourier transform lens 16,
It reaches onto a photodiode array 103 placed at the focal point of this Fourier transform lens.

In this case, the semiconductor substrate 11 is made of Si, GaA
s.

The use of semiconductor crystals such as InP has the advantage that, for example, photodiode arrays can be integrated within the substrate.

Furthermore, the inventors have discovered that an amorphous AS2 S3 thin film is effective as a constituent material for an AS-8 thin film optical waveguide. This is because, for example, a collimation lens or a Fourier transform lens can be easily formed by writing using electron beam irradiation. The inventors also confirmed that it is effective as an As-S-based material.

At the interface between the semiconductor substrate and the thin film optical waveguide, a thin film such as a thin film of quartz with a refractive index between that of the semiconductor substrate and that of the thin film optical waveguide is usually used as a buffer 1 to prevent propagating light from entering the substrate. Furthermore, the inventors have discovered that ZnO or AIN is particularly effective as a component of a surface wave transducer in terms of both piezoelectric conversion properties and ease of formation. Based on this, we have invented a surface wave transducer that is ideal for this type of device.

In other words, in the configuration of a thin film surface wave transducer, the thickness of the piezoelectric thin film is normally required to be 5 degrees of the wavelength of the surface wave. This has the disadvantage that it is difficult for surface waves to be introduced into the optical propagation path. However, as shown in FIG. 2, the inventors discovered that when a new counter electrode 21 is inserted at the interface between the substrate and the piezoelectric thin film, facing the comb-shaped electrode 19, the thickness of the zno or A/N piezoelectric thin film increases. It was confirmed that a sufficiently large electromechanical coupling, for example, 15 degrees, can be obtained with several inches (2 to 3%) of the wavelength of the surface wave, making it easy to introduce the surface wave into the optical propagation path. In this case,
On the surfaces of St, GaAs, InP, etc.

After forming a buffer layer in a glass state in advance and forming a counter electrode thereon, a Zn◯ or AIN thin film is deposited by, for example, sputtering.

These thin films are C-axis oriented, and the so-called fundamental mode of Rayleigh waves is excited.

Furthermore, in the case of a Si substrate, the inventors found that when the ZnO thin film is made to have a wavelength of 20 to 30 times the wavelength of the surface waves, the higher-order mode of Rayleigh waves (Sezawa mode) is excited, which is particularly effective for excitation of high-frequency surface waves. We also confirm that this kind of combination of substrate materials, piezoelectric materials, etc. can further improve the functionality of optical spectrum analyzers, e.g.
It has become clear that this method produces features that cannot be obtained with optical spectrum analyzers using bO3 substrates.

The present invention will be described in detail below with reference to specific examples.

Description of Examples Example 1 A quartz buffer layer with a thickness of 0.1 μm was sputter-deposited on a GaAs substrate with a smooth surface. Next, an AI thin film with a thickness of 0.1 μm is vacuum-deposited on the surface wave transducer portion of this substrate to form a counter electrode, and sputter-deposited on this to a thickness of 11 μm. tm ZnO piezoelectric thin film is formed, and on top of this, an AI comb-shaped electrode with a period of 20 to 301 mm and a thickness of 0° and 1 μm is formed using vacuum evaporation and photolithography techniques, thereby producing a Rayleigh wave fundamental mode in a band of 126 to 190 MHz. A surface wave transducer was formed.

Next, an As2S3 thin film was deposited to a thickness of 1/1 m over the entire surface of the substrate by vacuum evaporation to form an optical waveguide. Finally, a collimation lens with a focal length of 5 and a Fourier transform lens made of a Fresnel lens were formed by electron beam irradiation.

Example 2 A ZnO piezoelectric thin film with a thickness of 3 μm was formed by sputter deposition on a surface wave transducer portion on a surface-oxidized St substrate, and on this a ZnO piezoelectric thin film with a period of 8.5 to 17 μm was formed.
zm AI comb-shaped electrodes were formed using the same processing method as in Example 1 to form a Sezawa mode surface wave transducer with a band of 300 to eoo MHz.

Next, after forming a 5ip-n optical guide array at the focal point of the Fourier transform lens, A
An s2S3 optical waveguide and lens were formed.

Effects of the Invention Since the optical integrated spectrum analyzer according to the present invention is formed on a semiconductor substrate, it has the feature that, for example, semiconductor elements such as photodiodes and lasers can be monolithically integrated with acousto-optic elements on the semiconductor substrate. . moreover,
AI! The 2-83 thin film optical waveguide has the advantage that various microscopic optical elements such as waveguides and condensers can be formed by simply writing by electron beam irradiation, making it easy to manufacture this type of device.

Note that the optical integrated spectrum analyzer according to the present invention takes advantage of the features of an acousto-optic device and the features of a semiconductor device, and has high industrial value as a real-time signal processing device.

[Brief explanation of drawings]

FIG. 1 (3) is a top view of the essential parts of the optical integrated spectrum analyzer according to the present invention, FIG. It is a sectional view of the main part. 11...Semiconductor substrate, 12...Thin film optical waveguide, 14...Collimation lens, 16
...Fourier transform lens, 17...P/Surface wave transducer.

Claims (1)

[Claims] (1) A semiconductor substrate and an As-
A three-system thin film optical waveguide, a collimation lens and a Fourier transform lens arranged sequentially in the light propagation direction on the optical waveguide, and a light waveguide arranged orthogonally to the optical waveguide between the collimation lens and the Fourier transform lens on the substrate. What is claimed is: 1. An optical integrated spectrum analyzer comprising: a piezoelectric thin film surface wave transducer; (2) The optical integrated spectrum analyzer according to claim 1, characterized in that the semiconductor substrate is made of one of Si, GaAs, and InP. (3) As-S thin film optical waveguide with As 2 S3
Claim 1 characterized in that the structure is made of a thin film.
A self-contained optical integrated spectrum analyzer. (4) The optical integrated spectrum analyzer according to claim 1, wherein the piezoelectric thin film surface wave transducer is constructed of a ZnO or AIN piezoelectric thin film surface wave transducer. (6) Claim 1, characterized in that the piezoelectric thin film surface wave transducer is excited by Sezawa mode surface waves.
Optical integrated spectrum analyzer described in Section 1.