JP2001024288A - Semiconductor optical control element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor optical control element having optical amplification function in a wire wavelength bandwidth. SOLUTION: A first active layer 21 wherein the band gap wavelength is λ1 and the thickness is w1, and a second active layer part 23 wherein the band gap wavelength is λ2 and the thickness is w2, sandwich a barrier layer 22. The relation of band gap wavelength is λ1<λ2. The relation of thickness is w1>w2. A wavelength bandwidth of the whole gain spectrum wherein gain spectrums obtained from the respective active layer parts 21-23 are superposed is spread by the sum of gain spectrums different in the wavelength band, an optical amplification region of wide band can be realized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor light control device having an optical amplification function, and more particularly, to a semiconductor light control device for realizing a wide band optical amplification region by using an active layer in which a plurality of active layers are stacked. Related to the element.

[0002]

2. Description of the Related Art In recent years, with the development of the multimedia information society, the amount of data in information communication has been dramatically increased, so that a high-speed and large-capacity communication system has been desired. In order to enable the transmission of such a rapidly increasing amount of information data, an optical communication system using an optical fiber has been adopted. Further, in addition to the conventional optical communication system using single wavelength light, wavelength division multiplexing (hereinafter referred to as wavelength division multiplexing) that transmits signal light of a plurality of different wavelengths through a single optical fiber and carries data for each wavelength light and transmits the data. WDM) communication technology is advancing. This wavelength division multiplexing communication technology enables a terabit-class transmission system by packing a large number of signals in a band to dramatically increase the amount of communication.

In such an optical communication system, light loss occurring in the system due to propagation of light is a major problem, but the light loss has been compensated for by using a semiconductor optical amplifier or fiber amplifier. I was In particular, semiconductor optical amplifiers are positioned as occupying an important position in optical communication systems because of their small size and easy integration, and their high performance is expected.

Further, in consideration of the operation of a semiconductor optical amplifier in a wavelength division multiplexing communication system, it is required to have a uniform optical amplification function for all wavelength bands used. That is, it is required to obtain a flat gain spectrum over a wide wavelength band.

[0005]

However, in consideration of the operation of the semiconductor optical amplifier in the wavelength division multiplex communication system, the wavelength band currently used in the wavelength division multiplex communication technology is centered on the wavelength of 1550 nm where the optical loss is the smallest. The M band, that is, the wavelength band of 1530 to 1570 nm is mainly used, and although the use of the L band of 1570 to 1610 nm wavelength band is being studied, in order to obtain a wider wavelength band, It does not have a uniform optical amplification function for all the used wavelength bands. Also, existing semiconductor optical amplifiers, for example, a semiconductor optical amplifier comprising an active layer having a bulk structure,
It is a wavelength band of about 20 nm, M band, L band,
Furthermore, there is a problem that it is not possible to cope with a drastic increase in communication traffic by obtaining a gain spectrum that is flattened in a wide wavelength band over a further band.

The present invention has been made in view of such a problem, and an object of the present invention is to provide a semiconductor light control element having an optical amplification function over a wide wavelength band.

[0007]

According to the present invention, there is provided a semiconductor light control device having an active layer having an optical amplification function by current injection, wherein the active layer has a band gap wavelength. And a plurality of active layer portions having different band gap wavelengths than the active layer portions.

The active layer includes a first active layer portion, a barrier layer laminated on the first active layer portion and having a smaller bandgap wavelength than the first active layer portion. A second active layer portion having a bandgap wavelength larger than that of the first active layer portion, the second active layer portion being stacked on the barrier layer.

[0009]

The active layer having a light amplification function by current injection is
Stacked by a plurality of active layer portions having different bandgap wavelengths, the entire gain spectrum obtained by superimposing the gain spectra obtained from each active layer portion has its wavelength band expanded by the sum of the gain spectra of different wavelength bands, A wide-band optical amplification region is realized.

[0010]

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

FIG. 1 is a perspective view showing an embodiment of a semiconductor light control device according to the present invention. In FIG. 1, reference numeral 1 denotes a substrate made of n-InP, and a mesa stripe having a width of 0.4 μm is formed on the substrate 1. Layer 2 is provided. The mesa stripe layer 2 has nI
It comprises a 1 μm thick cladding layer 3 of nP, an active layer 4 laminated thereon, and a 0.2 μm thick p-InP layer 5 further laminated thereon.

The mesa stripe layer 2 is buried by a p-InP clad layer 7 laminated on the substrate 1, and the n-InP
A current exploitation layer 6 is provided. Further, a p-electrode 8 is provided on the p-InP clad layer 7. The element length of the semiconductor light control element thus configured is 600 μm.

FIG. 2 is a cross-sectional view of the active layer constituting the semiconductor light control device shown in FIG. 1. In FIG. 2, reference numeral 13 denotes a second active layer portion, which has a band gap wavelength of 1.62 μm and a thickness of 0. .1 .mu.m InGaAsP. Sign 1
Reference numeral 2 denotes a barrier layer disposed on the second active layer portion 13, which has a band gap wavelength of 1.3 μm and a thickness of 0.05 μm.
Of InGaAsP. Reference numeral 11 denotes a first active layer portion disposed on the barrier layer 12, and has a bandgap wavelength of 1.58 μm and a thickness of 0.2 μm of InGaAs.
sP. In this case, the width of the active layer 4 is 0.
4 μm.

FIG. 3 is a diagram showing the band structure of the active layer shown in FIG. 2. In FIG. 3, reference numeral 21 denotes a first active layer portion.
Corresponds to the first active layer portion 11 in FIG.
Reference numeral 2 denotes a barrier layer, which corresponds to the barrier layer 12 in FIG. 2, and reference numeral 23 denotes a second active layer portion,
Of the active layer 13.

The band gap wavelength λ sandwiching the barrier layer 32
1. Consisting of a first active layer portion 21 having a thickness w1 and a second active layer portion 23 having a band gap wavelength λ2 and a thickness w2, the band gap wavelength relationship is λ1 <λ2, and the thickness relationship is It is configured such that w1> w2.

In the embodiment having such a configuration, first, the light incident on the active layer 4 is amplified by the first active layer portion 21 and the second active layer portion 23. Light near λ1 is mainly emitted from the first active layer portion 21.
While the light near the wavelength λ2 is mainly
Are amplified in the active layer portion 23.

Further, the light having the wavelength λ1 also suffers a loss in the second active layer portion 23 at the same time. However, the first
Since the thickness w1 of the active layer portion 21 is larger than the thickness w1 of the second active layer portion 23, the effect of light confinement is large and a large gain can be obtained. Can be.

Accordingly, the entire gain spectrum of the active layer 4 is represented as shown in FIG. The horizontal axis represents wavelength, and the vertical axis represents gain. In the figure, a is a gain spectrum obtained from the first active layer portion 21, b is a gain spectrum obtained from the second active layer portion 23, and c is an active layer 4. Is a gain spectrum obtained from the whole of.

As shown in FIG. 4, the first InGaAs
The sum of the gain spectrum of the 1.55 μm wavelength band in the P active layer portion 21 and the gain spectrum of the 1.58 μm wavelength band in the second InGaAsP active layer portion 23 gives an overall gain spectrum with an expanded wavelength band. I have. At this time, the gain spectrum in the 1.55 μm band is absorbed in the second InGaAsP active layer portion 23 as apparent from FIG. 4, but the gain is increased by increasing the thickness w1 of the first active layer portion 21. The increase cancels out the absorption effect in the second InGaAsP active layer portion 23.

That is, the first active layer portion 21 and the second
In the active layer portion 23, each band gap wavelength λ
1, there are two different gain spectra corresponding to λ2, and the overall gain spectrum is obtained by superimposing these different gains, that is, by summing the gain spectra of different wavelength bands, as shown in FIG. It will be flattened and spread.

FIG. 5 is a diagram comparing the gain spectrum of the semiconductor light control device of the present invention with the gain spectrum of the conventional structure, wherein the horizontal axis represents the wavelength and the vertical axis represents the gain.

As is apparent from FIG. 5, a gain spectrum over a wider wavelength band can be obtained as compared with that of the conventional structure, and the gain spectrum is wider than that of the conventional optical amplifier having one active layer. it is obvious. Thus, by obtaining a wide wavelength band, it is possible to uniformly amplify incident light over a wide wavelength range.

In the above-described embodiment, the case where the active layer is constituted by two active layers is described. However, the case where the active layer is constituted by laminating three or more active layers is also applicable. Obviously, a similar effect is achieved. Further, since the active layer of the present invention can be applied to both the bulk structure and the quantum well structure, similar effects can be expected even if there is a difference between these structures.

[0024]

As described above, according to the present invention, in a semiconductor light control device having an active layer having an optical amplification function by current injection, the active layer includes a plurality of active layer portions having different band gap wavelengths. And has a bandgap wavelength smaller than that of the active layer portion, and is stacked on each other via a barrier layer. The layer thickness of the active layer portion is thinner as the bandgap wavelength is larger. It is possible to realize a light control element having a light amplification function in the amplification region.

The active layer has a first active layer portion, a barrier layer laminated with the first active layer portion, and a barrier layer having a smaller bandgap wavelength than the first active layer portion, and a laminate with the barrier layer. And has a second active layer portion having a larger bandgap wavelength than the first active layer portion,
By superimposing the gain spectrum having two shapes in the entire spectrum, a flattened gain spectrum over a wide wavelength band can be realized.

Further, since the thickness of the first active layer is thicker than that of the second active layer, the confinement effect is increased, and an optical control element having a broadband optical amplification function can be realized. Further, by arbitrarily changing the bandgap wavelength, it is possible to cope with any used wavelength.

[Brief description of the drawings]

FIG. 1 is a perspective view showing one embodiment of a semiconductor light control element of the present invention.

FIG. 2 is a sectional view of an active layer included in the semiconductor light control device shown in FIG.

FIG. 3 is an explanatory diagram illustrating a band structure of an active layer illustrated in FIG. 2;

FIG. 4 is an explanatory diagram showing an overall gain spectrum of an active layer.

FIG. 5 is an explanatory diagram comparing a gain spectrum of the semiconductor light control device of the present invention with a gain spectrum of a conventional structure.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 2 Mesa stripe layer 3 Cladding layer 4 Active layer 5 p-InP layer 6 n-InP current extracting layer 7 p-InP cladding layer 8 p electrode 11, 21 First active layer portion 12, 22 Barrier layer 13, 23 Second active layer portion

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Shunji Seki 3-19-2 Nishi-Shinjuku, Shinjuku-ku, Tokyo Inside Japan Telegraph and Telephone Corporation (72) Inventor Yuzo Yoshikuni 3- 192-1 Nishishinjuku, Shinjuku-ku, Tokyo No. Nippon Telegraph and Telephone Corporation F-term (reference) 5F073 AA72 BA01 CA12 EA29

Claims (5)

[Claims] 1. A semiconductor light control device comprising an active layer having an optical amplification function by current injection, wherein the active layer comprises:
A semiconductor light control element comprising: a plurality of active layer portions having different band gap wavelengths; and stacked together via a barrier layer having a band gap wavelength smaller than the active layer portion. 2. The semiconductor light control device according to claim 1, wherein the layer thickness of the active layer portion is smaller as the band gap wavelength is larger. 3. The semiconductor light control device according to claim 1, wherein the active layer has two active layer portions. 4. A semiconductor light control device having an active layer having an optical amplification function by current injection, wherein the active layer comprises:
A first active layer portion, a barrier layer laminated on the first active layer portion, and having a smaller bandgap wavelength than the first active layer portion, a barrier layer laminated on the barrier layer, and A second active layer portion having a bandgap wavelength larger than that of the first active layer portion. 5. The semiconductor light control device according to claim 4, wherein a thickness of said first active layer portion is larger than a thickness of said second active layer portion.