JPH01200233A - Optical switch - Google Patents

Abstract

PURPOSE:To surely separate and take out light signals by forming 1st and 2nd waveguides into vertical juxtaposition constitution where optical coupling is efficiently executed and the shorter waveguides are necessitated and isolating output ports in a horizontal direction, then coupling optical fibers thereto. CONSTITUTION:A groove 1A is provided on an n-type InP substrate and an InGaAsP layer 2, an InP layer 4, an InGaAsP layer 5, an n-type InP layer 6, a p-type InP layer 7, and a p-type InGaAsP layer 8 are superposed thereon. An SiO2 mask of about 1.4 deg. intersection angle with the groove 1A and about 5mum width is then applied on the surface and the layers are chemically etched by a CVD method and a photomechanical process to form the mesa arriving at the n-type InP layer 6. A TiPt electrode 9 is deposited on the surface of the waveguide WG 2 intersecting with the waveguide WG 1 and an AuSn elec trode 10 is deposited on the rear of the substrate while the SiO2 mask is re moved. The 1st, 2nd waveguides are diagonally intersected by maintaining the intersected part necessary for optical coupling and the output ports are isolated in the horizontal direction. The light signals are surely separated and taken out when the optical fibers are coupled thereto.

Description

[Detailed Description of the Invention] [Summary] A directional coupling type optical switch suitable for use in an optical communication system or an optical information processing system, etc., has good integration properties and can reliably and easily transmit light from each of a plurality of output ports. A first waveguide whose direction is determined by a groove formed in a semiconductor substrate, and a layer laminated above the first waveguide in an area where optical coupling is possible, for the purpose of making it possible to extract a signal. and a second waveguide whose direction is determined by a mesa portion formed on the surface side and extending diagonally across the first waveguide.

[Industrial application field]

The present invention relates to a directional coupling type optical switch suitable for use in optical communication systems, optical information processing systems, and the like.

[Conventional technology]

Generally, in order to improve the performance of optical communication systems or optical information processing systems, it is necessary to be able to process optical signals temporally and spatially without replacing them with electrical signals.

Naturally, this requires an optical switch, and research and development is currently underway mainly on L i N b O3 materials and semiconductor materials.

FIG. 3 shows a cut-away oblique view of essential parts of a conventional example called a directional coupling type optical switch.

In the figure, 21 is an n+ type 1nP substrate, 21A and 2
1B is a groove formed in the substrate 21, and 22 is an n-type! n
Q a A, 3 p layer, 23 is n-type 1nP layer, 24
is a p+ type 1nP layer, 25A and 25B are mutually independent n-side electrodes, 26 is an n-side electrode, PIN is a human-powered boat, and P
out+ and P. o7□ each indicates an output port.

In this optical switch, the optical signal input from the input port (Pus) effectively changes the refractive index of the waveguide depending on the voltage applied to the P-side electrodes 25A and 25B. UT+ or P. It is possible to output an optical signal by switching to either UT□.

[Problem to be solved by the invention]

In the conventional optical switch explained with reference to FIG.
The coupling force between two waveguides depends on the distance between them, and becomes stronger as the waveguide becomes narrower.

However, in the configuration shown in Figure 3, it is difficult to bring the two waveguides close enough together, and the coupling force is weak.
In order to sufficiently couple light between two waveguides, it is necessary to make them longer, but this reduces the integration efficiency and increases the number of optoelectronic integrated circuits.
integrated circuit:0EI
It is inconvenient to configure C).

In order to solve this problem, attempts have been made to arrange the two waveguides in parallel in the vertical direction instead of in parallel in the horizontal direction, that is, to stack the two waveguides in close proximity.

However, with this arrangement, there is a problem in that it is difficult to connect optical fibers to the two output ports and reliably extract optical signals.

The present invention aims to provide an optical switch that has good integration and can reliably and easily extract optical signals from each of a plurality of output ports.

[Means to solve the problem]

In the optical switch of the present invention, a semiconductor substrate (for example, an n-type 1n
A first waveguide (e.g. first waveguide WG) whose direction is determined by a groove (e.g. groove IA) formed in the P substrate l)
I), and a mesa portion that is laminated above the first waveguide in an area where optical coupling is possible, is on the surface side, and is formed so as to extend diagonally across the first waveguide. A second waveguide (second waveguide WG2) whose direction is determined.

[Effect]

By adopting the above-mentioned means, the first waveguide and the second waveguide are arranged in parallel in the vertical direction, which is said to be a form in which optical coupling is efficiently performed and can be shortened. However, since the output ports are separated laterally, it is easy to reliably separate and extract the optical signals by coupling an optical fiber thereto.

〔Example〕

FIG. 1 shows a plan view of essential parts for explaining one embodiment of the present invention, and the same symbols as those used in FIG. 3 indicate the same parts or have the same meanings.

In the figure, WF is the wafer, WGI is the first waveguide, and W
O2 is the second waveguide, EL is the electrode, PINI and p+N
z is the input port, 11 is the effective length where the waveguides WGI and WO2 intersect, 12 is the length between the centers of the output ports, and θ is the intersection angle of the waveguides WGI and WO2, respectively.

In this example, 11: about 400 cμm] I! , :20 (μm) θ: 1.4°. Note that 11 is approximately the same as the optical coupling length when the waveguides WGI and WO2 are stacked.

Now, from input capo-1-P, □, for example, wavelength 1.
When an optical signal of 55 (μm) is input manually, the optical signal propagating through the waveguide WGI is coupled to the waveguide WG2 at the intersection, propagates, and is sent out from the output port P.uT□.

In addition to the above conditions, when a negative voltage is applied to the electrode EL, the depletion layer from the pn junction expands and the refractive index changes, so the light coupled to the waveguide WG2 is again
Coupled to waveguide WGI and output port P. Sent from uy+.

In this embodiment, as described above, the output boat P.

LITI and P. Since the distance between U and A2 is 20 [μm], there is sufficient margin even when connecting optical fibers, and it is extremely easy to separate and extract optical signals. Note that since the waveguides WGI and WO2 are stacked close to each other in the vertical direction, light is sufficiently coupled over a short distance.

FIG. 2 shows a side view of the main part of the embodiment shown in FIG. 1 taken along line A--A.

In the figure, ■ is an n-type 1nP substrate, IA is a groove for forming the second waveguide, 2 is an l nGaAs P layer, and 3 is an I
n Q a A S P layer, 4 is InP layer, 5 is I
nGaAsP layer, 6 is n-type InP layer, 7 is p-type InP layer, 8 is p-type 1nGaAsP layer, 9 is p-side electrode, 10 is n
In the side electrode, Wl indicates the width of the groove IA, and W2 indicates the width of the mesa portion.

Examples of main data regarding each part are as follows.

(1) Surface index for substrate 1: (100) Impurity concentration: 2 × 10I8 [cm-”) + 2)l
/ilA Width W1: 5 (μm) Depth: 0.3 Cμm] Direction: <Qll> (3) In Ga As P layer 2 Composition (wavelength conversion): 1.15 Cμm] Thickness: 0 .ICμ
m] Non-doped impurity concentration: 2 X 10” (cm-ff) f4)
Composition (wavelength conversion) of T n Ga As P layer 3: 1.3 C μm Thickness: 0.5 C μm Non-doped impurity concentration: 2 x 1016 (cm-') (51
Thickness of InP layer 4: 0.6 Cμm] Non-doped impurity concentration: 2×l016 [Cffl-3] (6) I
Composition (wavelength conversion) for n Ga As P N 5: 1.3 Cμm] Thickness: 0.5 (μm) Non-doped impurity concentration: 2 X 10"(cm-') (6) n
Thickness of type 1nP layer 6: 1 [μm] Impurity concentration: 5 X I Q10 (cm-') (7)
Thickness of p-type InP layer 7: 0.5 Cμm] Impurity concentration: I x 10” (am-”) (8)
Composition (wavelength conversion) of p-type InGaAsP layer 8: 1
．． 3Cμm] Thickness: 0.4Cμm] Impurity concentration: lX10 violet 9 (Cm −' ) (9) Material for p-side electrode 9: T i P Thickness: 0.1Cμm] 00) Material for n-side electrode 10: AuSn Thickness: 0.1 [μm] 0υ Width W2 of mesa part: 5 (μm) Height: 1.4Cμm) (excluding n-side electrode 9) Figures 1 and 2
It is the hour wheel that produces the light switch seen in the figure.

That is, the groove IA is formed in the substrate 1 by applying a normal photolithography technique, and then liquid phase epitaxial growth (liquidphase epitaxial growth) is performed.
axy:LPE) method, InGa
AsPnGaAsP layer The nGaAsP layer 8 is grown continuously, and then chemical vapor deposition (chemical vapor deposition) is performed.
By applying apordeposition (CVD) method and photolithography technology, a cross angle θ=1.4° and a width of 5 C μm with respect to the groove IA]
A mask film made of silicon dioxide (SiOz) is formed, and then, by applying a chemical etching method, etching is performed from the surface to reach the n-type In2 layer 6, with a step difference of 1.4 [μm]. After forming a certain mesa and then removing the mask film, an electrode 9 is formed on the surface of the waveguide WG2 intersecting with the waveguide WGI, and an electrode 10 is formed on the back surface of the substrate 1 to complete the process.

〔Effect of the invention〕

In the optical switch according to the present invention, the first waveguide and the second waveguide laminated above the first waveguide intersect diagonally while maintaining the intersection necessary for optical coupling.

By employing the above configuration, the first waveguide and the second waveguide are arranged in parallel in the vertical direction, which is considered to be a type of optical coupling that is efficient (and short). However, since the output ports are spaced apart laterally, it is easy to reliably separate and extract the optical signals by coupling an optical fiber thereto.

[Brief explanation of the drawing]

FIG. 1 is a plan view of the main part for explaining one embodiment of the present invention, FIG. 2 is a cutaway side view of the main part along line A-A in FIG. 1,
FIG. 3 each shows a cutaway slope view of the main part for explaining the conventional example. In the figure, WF is the wafer, WGI is the first waveguide, and W
O2 is the second waveguide, EL is the electrode, PIN+ and PIN
□ is the input port, pout+ and P. UT□ is the output port, x is the effective length where the waveguides WGI and WO2 intersect, 12 is the length between the centers of the output boats, θ is the intersection angle of the waveguides WGI and WO2, and ■ is the n-type 1nP substrate,
IA is a groove for forming the second waveguide, 2 is InGaA
sPN, 3 is InGaAsP layer, 4 is InP layer, 5 is I
nGaAsP layer, 6 is n-type 1nP layer, 7 is p-type 1nP layer, 8 is p-type In Ga As P N%, 9 is p-side electrode, 10 is n-side electrode, Wl is the width of trench IA, W2 is The width of each mesa portion is shown. Patent Applicant: Fujitsu Ltd. Representative Patent Attorney: Akira Aitani Representative Patent Attorney: Hiroshi Watanabe Plan view of essential parts to explain one embodiment Figure 1 Figure 2

Claims (1)

[Claims] A first waveguide whose direction is determined by a groove formed in a semiconductor substrate; An optical switch comprising: a second waveguide whose direction is determined by a mesa portion formed to extend diagonally across the first waveguide.