JPH0344988A - Integrated circuit for light amplification - Google Patents

Abstract

PURPOSE:To obtain a light amplification integration circuit capable of preventing the generation of unrequired emission and improving optical sensitivity by using a light amplifier which includes rare earth elements, such as erbium, and amplifying only a signal light equivalent to the level of said rare earth elements. CONSTITUTION:A light amplifier 21 which has a GaInAsP layer 11 containing rare earth elements, such as erbium and a photodetector 23 are integrated with an optical waveguide 22 so that may be under a monolithic structure. Under this structure, inverse bias is applied between a p type electrode 8 and an n type electrode 9 of the photodetector 23 while forward bias is applied between the electrode 8 and electrode 9 of the optical amplifier 21 and incident light 20 is entered under the above state. If the wavelength of the light 20 is the optically amplified wavelength of erbium, the wavelength is amplified with an amplifier 21, and then is received by the detector 23 by way of a waveguide passage 22. Moreover, no light other than the wavelength is generated in terms of the optical output of the amplifier 21. Therefore, the signal light is further amplified and intensified, thereby generating no other light which may become a noise. It is, therefore, possible to improve an S/N ratio to a great extent.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical integrated circuit that improves the sensitivity of optical detection applied to optical transmission systems.

[Conventional technology]

Optical transmission systems have made great progress in high-speed, long-distance transmission, such as the practical application of distributed feedback lasers that oscillate at a single frequency, and are currently capable of transmitting 1.6 Gb/s signal light at 120 Gb/s without repeating.
It has reached the level where it can transmit distances of Km. and,
What determines this performance is the sensitivity of the optical detector.For future higher-speed optical transmission systems, the sensitivity of the optical detector will be a factor that will determine the performance of the system.

However, the optical detectors currently in use, such as pin photodiodes and avalanche photodiodes (APDs), have achieved performance close to their theoretical limits.
It is not possible to expect to improve the performance of the layer.

On the other hand, optical amplifiers that amplify weak signal light that has conventionally been propagated through optical fibers are being researched.

This is to operate a semiconductor laser as a linear optical amplifier that directly amplifies signal light from the outside by setting the device condition to below the oscillation threshold. If this optical amplifier is used immediately before the optical detector, the minimum reception level can be improved compared to the case without this optical amplifier.

Therefore, the optical integrated circuit shown in FIG. 3, in which this optical amplifier and optical detector are monolithically coupled through a waveguide, is considered to be useful. This optical amplification integrated circuit uses an n-type 1nP substrate 1 as shown in FIG.
．． 55 μm GaInAsP layer2. G with a wavelength of 1.3 μm
aInAsp layer 3 + p-type InP layer 6. p-type GaInAs
an optical amplifier 21 having a laser structure consisting of a P cap layer 7;
GaInAsP layer with a wavelength of 1.55 pm2. Wavelength 1.3μ
m GaInAaP layer 3. Non-doped D-type InP layer 5
．． A photodetector 23 consisting of a p-type InP layer 6° and a p-type GaInAsP layer 7 is connected to a GaInAsP layer 4 having a wavelength of 1.3 μm.
．． It has a monolithic structure in which a non-doped n-type InP layer s and a p-type InP layer 6 are coupled by a waveguide 22. Here, a forward bias is applied between the n-type electrode 8 and the n-type electrode 9 of the optical amplifier 21, and the n-type electrode 8 and the n-type electrode of the photodetector 23 are
With reverse bias applied to the mold electrode 9, this optical amplifier 2
When incident light 20 is introduced into the optical waveguide 1, the incident light 20 is amplified and then passed through a waveguide 22 and received by a photodetector 23.

[Problem to be solved by the invention]

However, in such conventional optical amplification integrated circuits, due to the airy light emission generated by the optical amplifier,
There is a drawback that noise light other than the wavelength of the signal also enters the optical detector and the signal-to-noise ratio cannot be improved.

The present invention has been developed in view of the above points, and its purpose is to prevent undesirable light emission from an optical amplifier that causes noise,
The purpose of the present invention is to provide an optical amplification integrated circuit that amplifies only signal light and improves optical sensitivity.

[Means to solve the problem]

In order to achieve the above object, the present invention utilizes erbium (
The main feature is that an optical amplifier and an optical detector having a Ga1nAsP layer containing rare earth elements such as Er) are monolithically integrated in an optical waveguide.

[Effect]

In the present invention, by using an optical amplifier containing a rare earth element such as erbium, it is possible to amplify only the signal light corresponding to the level of the rare earth element.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a structural sectional view showing an embodiment of the optical amplification integrated circuit according to the present invention. In the figure, 1 is an n-type InP substrate,
2 is a GaInAsP layer with a wavelength of 1.55 μm, 3 and 4 are GaInAsP layers with a wavelength of 1.3 μm, 5 is a non-doped n-type InP layer, 6 is a p-type InP layer, γ is a p-type GarnA layer
sP cap layer, 8 is a p-type electrode, 9 is an n-type electrode, 10 is an anti-reflection coating film, 11 is erbium-doped GaInAs
This is the P layer.

That is, the optical amplification integrated circuit of this embodiment includes the optical amplifier 21
The optical amplifier 21 is similar to the conventional example shown in FIG.
Erbium-doped Ga formed on n-type InP substrate 1
1nAsP layer 11, p-type 1rsP layer 6. p-type (r
An optical amplifier having a laser structure including an alnAsP cap layer T is used, and is configured to amplify only the signal light corresponding to the level of erbium. Note that in the drawings, the same reference numerals indicate the same or equivalent parts.

In order to operate the optical amplification integrated circuit configured in this way, a reverse bias is applied between the n-type electrode 8 and the n-type electrode 9 of the optical detector 23, and the n-type electrode 8 and the n-type electrode of the optical amplifier 21 are 9 and enters the incident light 20 into the optical amplification section. At this time, if the wavelength of the incident light 20 is adjusted to 1.54 μm, which is the optical amplification wavelength of erbium, the incident light 20 is amplified by the optical amplifier 21, and then passes through the waveguide 22 to the optical detector. The light is received at 23. In the conventional configuration shown in FIG. 3, the optical output from the optical amplifier 21 at this time is 1.53μ in addition to the amplified signal light as shown in FIG.
Emissions are uniformly emitted over a wavelength range from m to 1,57 μm. Since light other than this received light becomes noise, the signal-to-noise ratio is not improved in this example. On the other hand, in the embodiment of the present invention shown in FIG. 1, as shown in FIG. 2, no light other than the amplified wavelength of erbium is generated. This is because non-luminescent centers are introduced into the GaInAsP layer 11 due to the addition of erbium. Therefore, the signal light is amplified and becomes stronger, and almost no other light that becomes noise is generated. This improved the signal-to-noise ratio by a factor of 100.

a>, In the above example, a case was shown in which erbium was used as the rare earth element, but the present invention is not limited to this, and various rare earth elements having a transition wavelength of 1°2 to 1.6 μm can be used. It can also be used.

〔Effect of the invention〕

As explained above, according to the optical amplification integrated circuit of the present invention, GaInAsP doped with rare earth elements such as erbium
By injecting a current into an optical amplifier with a layer, the signal light corresponding to the level of one rare earth element is amplified, and no other noise light is generated, which helps improve the light receiving sensitivity of the detection and is useful for optical transmission systems. This has the advantage of extending the relay distance.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional view of the structure of an embodiment of the optical amplifier integrated circuit of the present invention, Fig. 2 is a diagram showing the optical output characteristics from the optical amplifier of this embodiment, and Fig. 3 is a diagram showing the optical output characteristics of the optical amplifier of this embodiment. A fourth structural cross-sectional view showing an example of an optical amplification integrated circuit that integrates optical amplifiers.
The figure is a diagram showing optical output characteristics from a conventional optical amplifier. 1...N-type InP substrate, 2...Wavelength 1.55μ
m GaInAsP layer, 3,46 ams wavelength 1.3 μm
G-type InAsP layer, 5...Non-doped n-type In
P layer, 5ee*ep type InP layer, 7 m m a *
P-type GaInAsP cap layer, 8... p-type electrode,
9...n-type electrode, 10...non-reflective coating film,...-
- Erbium-doped GaInAsP layer, 21... optical amplifier, 22... waveguide, 23... optical detector.

Claims (1)

[Claims] An optical amplification integrated circuit characterized in that an optical amplifier having a GaInAsP layer containing a rare earth element and a waveguide type optical detector are monolithically coupled through a waveguide.