JPH0671120B2 - Optical integrated device - Google Patents

Description

The present invention relates to an optical integrated device for optical switching.

(Prior Art) An optical filter element having a function of selecting an arbitrary optical signal from wavelength-multiplexed optical signals is one of key devices applicable to a wide range of applications in optical transmission, optical switching, optical information processing, and the like. Is one. In any application, sufficient wavelength selectivity and variable tuning width with a wide selection wavelength are required as the characteristics of the optical filter element. Further, since it is inevitable to make an optical integrated circuit as a structure, it is also necessary to be a transmissive wavelength selection filter that transmits only an arbitrary desired wavelength.

BACKGROUND ART Heretofore, some studies have been made on transmissive wavelength selection filters. Among them, an optical filter element having a structure in which an optical waveguide layer is formed on a semiconductor substrate by crystal growth and an optical feedback structure having wavelength selectivity is provided on the optical waveguide layer has been studied. An example of this reference is the Applied Physics Letters, published in 1986.
ics Letters) RC Alffernen, Vol. 49, page 125
I can give you other papers.

(Problems to be Solved by the Invention) However, since these conventionally proposed and examined optical filter elements do not emit light, injection of light into the optical filter element or light emission from the optical filter element There was a drawback that it was very difficult to align the optical axis when taking out.

An object of the present invention is to provide an optical filter element whose optical axis can be easily aligned.

(Means for Solving the Problems) In the optical integrated device of the present invention, an optical filter device and a semiconductor laser are arranged in parallel, and the optical filter device and the semiconductor laser are optically coupled to the same waveguide. It is characterized by being.

(Operation) When light is injected into the conventional optical filter element, the optical axis is adjusted while observing the element end face by using a television camera or the like to see whether or not the light is actually injected. This task requires skill and is inefficient.

On the other hand, when the spectrum of a semiconductor laser is measured, it is possible to inject light into the optical fiber relatively easily by using only one lens. At this time, the output light of the semiconductor laser is injected into the optical fiber, the optical output from the optical fiber is monitored, and the positions of the semiconductor laser, the lens, and the optical fiber are adjusted so as to maximize the output.

From the above, if an optical optical integrated device in which a semiconductor laser and an optical filter element are arranged in parallel and these are optically coupled to the same waveguide is used, optical axis alignment causes oscillation of the semiconductor laser. This can be done easily. Further, when operating as an optical filter element, if no current is injected into the semiconductor laser, the light branched to the semiconductor laser side of the incident light is absorbed by the active layer of the semiconductor laser and does not pass through. On the other hand, of the incident light, the light branched to the optical filter element side transmits only the light of a specific wavelength according to the transmission characteristics of the optical filter element. Therefore, the characteristics of the optical integrated element as an optical filter element are not deteriorated by integrating the semiconductor lasers in parallel.

(Example) Next, this invention is demonstrated in detail with reference to drawings. FIG. 1 is a plan view showing the structure of an optical integrated device according to an embodiment of the present invention. FIG. 2 is a perspective view showing the structure of the semiconductor laser 200, and FIG. 3 is a perspective view showing the structure of the optical filter element 300. The structure of this embodiment will be described below according to the manufacturing procedure. First, a semiconductor laser on the n-type InP substrate 110
A λ / 4 shift diffraction grating having a period of 2400Å is formed in 200 parts and the optical filter element part 300. Next, by the first LPE growth, the undoped InGaAsP optical guide layer 120 (λg = 1.3 μm, thickness 0.3
μm), n-type InP buffer layer 130 (thickness 0.1 μm), non-dove active layer 140 (λg = 1.53 μm, thickness 0.1 μm), p-type InP
The clad layer 150 (thickness 0.2 μm) is sequentially grown. InP clad layer 150 of optical waveguide 100 and optical filter element 300
And the active layer 140 are selectively removed. Next, in the second LPE growth, the p-type InP clad layer 160 is formed over the entire surface.

Next, in order to obtain a buried structure, after performing mesa etching, buried growth is performed by third LPE growth. Here, a double channel brenched embedded structure was used as the embedded structure. Finally, after forming electrodes on the substrate side and the growth layer side, the semiconductor laser 200 and the optical filter element 3
For electrical isolation between 00 and the optical waveguide 100, a groove is formed except in the vicinity of the central mesa. After that, a SiN film 170 is formed on both end faces of the device by using a plasma CVD device in order to improve the coupling with light. The reflectance of this end face was 2% or less. Semiconductor laser 200, optical filter element 30
The length of 0 is 300 μm, and the length of the optical integrated device of this embodiment including the optical waveguide 100 is 600 μm. The semiconductor laser 200 and the optical filter element 300 both have a width of 300 μm, and the width of the groove between them is 50 μm.

An example of the characteristics of the element thus prototyped is shown below. The transmission wavelength when current was not injected into the optical filter element 300 and the semiconductor laser 200 was 1.5563 μm, and when the current was injected into the optical filter element 300 only at 80 mA, the transmission wavelength was 1.5505 μm, and the transmission wavelength continuously changed by 58Å. Also, 5 of the semiconductor laser 200
The oscillation wavelength at mW output was 1.5560 μm. FIG. 4 shows the transmission characteristics when current is injected only into the optical filter element 300. The transmission blocking wavelength range is 65 Å, the transmission wavelength 10 dB attenuation width is
It was 0.5Å.

In this embodiment, the easiness of adjusting the optical axis, which is a feature of the present invention, is significantly improved. That is, the conventional optical filter element required about 1 hour for the optical axis adjustment, but the optical integrated element of the present invention was significantly improved to 10 minutes.

Although the optical filter element having the structure shown in FIG. 3 is used as the optical filter element in this embodiment, any element having another structure may be used as long as it can function as an optical filter. Furthermore, the material and composition of the element are not limited to those in the above-mentioned embodiments, and other semiconductor materials or dielectric materials may be used. Also, if the phase shift structure is configured to control the phase shift amount from the outside,
Furthermore, the variable wavelength range can be expanded. Further, in the present embodiment, the phase shift diffraction grating is used as the phase shift structure, but this is not limited to the phase shift diffraction grating, and it has a uniform diffraction grating and the width of the waveguide. Alternatively, a so-called equivalent phase shift structure in which the thickness is changed may be used. Further, a switch may be provided in the tapered portion of the waveguide 100 to reduce the loss during the filter operation.

(Effect of the Invention) In the conventional optical filter element, the optical axis adjustment was spent for about one hour, but in the optical integrated element of the present invention, the optical axis adjustment is shortened to about 10 minutes, and the optical axis adjustment is easy. Greatly improved.

[Brief description of drawings]

FIG. 1 is a plan view showing the structure of an optical integrated device according to an embodiment of the present invention. FIG. 2 is a perspective view showing the structure of the semiconductor laser integrated in the embodiment of FIG. FIG. 3 is a perspective view showing the structure of the optical filter element integrated in the embodiment of FIG. FIG. 4 is a diagram showing the transmission characteristics of the optical integrated device of this embodiment. 100 ... Optical waveguide, 200 ... Semiconductor laser, 300 ... Optical filter element, 110 ... Substrate, 120 ... Optical guide layer, 130 ...
... buffer layer, 140 ... active layer, 150, 160 ... cladding layer, 170 ... SiN film.

Claims (1)

[Claims] 1. An optical integrated device, wherein an optical filter device and a semiconductor laser are arranged in parallel, and the optical filter device and the semiconductor laser are optically coupled to the same waveguide.