JP2967057B2 - Surface type optical multifunctional element - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface-type optical multifunctional device having both a signal light receiving function and an amplification relay function.

[0002]

2. Description of the Related Art In a massively parallel computer in which a large number of processors are simultaneously operated in parallel to dramatically improve the computing capacity, a communication network connecting the processors is enlarged with the increase in the number of processors, and the performance is expected to increase. Not going up
The so-called wiring bottleneck is a problem. As a means for solving this problem, a parallel optical interconnection technology utilizing the high speed and spatial multiplexing of light has attracted attention.

As a configuration of a parallel optical interconnection for connecting a number of boards using a surface type optical device, an optical signal transmitted from a preceding board is temporarily converted into an electric signal by each board, and wavelength shaping processing is performed. A method of relaying the optical signal to the next board as an optical signal and a method of relaying the optical signal as it is without converting the optical signal into an electric signal are conceivable. In the case of performing multi-stage connection, since the former method causes a wiring delay due to electric processing, the latter method of relaying a signal as it is light is considered to be more advantageous.

In order to realize such a parallel optical interconnection device for relaying a signal as it is, it is necessary to use a surface-type optical multifunctional element having both a light receiving function and an optical amplification relay function. FIG. 11 is a conceptual diagram showing a cross-sectional structure of a conventional surface type optical multifunctional element. This surface optical multifunctional element has a structure in which a light receiving element 101 and an optical amplifying element 102 are integrated on a semiconductor substrate 100. Of the signal light beam incident through a microlens (not shown) provided on the upper part of the element, about half of the peripheral part enters the light receiving element 101, and about half of the central part enters the optical amplifier element 102. The optical system is set so that The light receiving element 101 receives a signal light and outputs an electric signal. The optical amplifying element 102 has a function of compensating for power lost due to branching to the light receiving element 101 and reflection / absorption at an electrode / boundary portion and relaying an optical signal to the next stage.

However, in order to form a parallel optical interconnection using such a surface-type optical multifunctional element,
There were several problems, such as: First, it is difficult to suppress residual reflection in such an integrated structure. The use of bulky and expensive optical isolators is not practical in parallel optical interconnection devices between boards. In an optical interconnection device in which amplifying elements are connected in multiple stages without using an optical isolator, even if there is slight residual reflection, the operation becomes unstable due to the composite resonator effect.

In the Fabry-Perot resonance type surface optical amplifying element, when the reflectance of the entrance surface and the exit surface is R ₁ and R ₂ , respectively, and the single-pass gain is G _S , R ₁ = G _S ² R ₂ . It is known that if the relationship (1) is satisfied, the reflection gain can be suppressed at the resonance wavelength. (Note that throughout this specification, the power reflection coefficient is simply referred to as the reflectance, and R _{i is} capitalized.
It is written as follows. In contrast, the amplitude reflectance shall be referred to as r _i in lower case. Similarly, if the light receiving element is also of the resonance type, the end face reflectivities on the incident side and the reflective side are R ₃ and R ₄ , respectively, and when the single-pass transmittance is α, R ₃ = α ² R ₄ . By satisfying the relationship (2), reflected return light can be suppressed. Therefore, in order to realize a reflection-free surface optical multifunction element, the resonance wavelength of the optical amplifier receiving element, wherein _{R 1, R 2, R 3} , reflectance of the four end faces of the R _4, and G
_S and α must be precisely controlled. However, even if these controls are performed, it is extremely difficult to sufficiently suppress reflection caused by steps or electrodes existing between the optical amplification element and the light receiving element.

[0007] The second problem is that multistage optical transmission that maintains a Gaussian profile cannot be performed. That is, in this surface-type optical multifunctional element, the periphery of the incident beam is a light receiving element,
The beam profile output from the optical amplifying element is different from the incident beam profile because the beam is separated by the step portion or the electrode. In this case, since the branching ratio between the light receiving element and the optical amplifying element is not constant in each board, a sufficient power or optical alignment margin cannot be obtained. Also, since the spot size and power distribution change greatly between incident and outgoing, the design of the optical system becomes complicated and cumbersome.

The third problem is that the entire device becomes thick. When a non-resonant light receiving element is integrated,
To obtain sufficient quantum efficiency, a thick active layer of 1 to 3 μm is required. On the other hand, in the case of a resonance type light receiving element, the absorption layer can be made thin, but a multilayer Bragg reflection film (D
BR) or a dielectric multilayer mirror must be provided. Also, since the layer structure of the light receiving element and the surface type multifunctional element are different,
The total growth layer thickness is the sum of both thicknesses. Since a complicated mesa structure must be manufactured with a thick layer structure, the process becomes complicated and productivity is poor.

Fourth, there is a problem that the element structure is complicated and the area is large, and the manufacturing process is also complicated. In the above-described planar optical multifunctional element, the light receiving element is arranged around the optical amplifying element, so that the element area increases, which is disadvantageous in terms of integration with other elements and high density array. .
In addition, an invalid area such as a step is formed at the boundary between the light receiving element and the optical amplification element, which causes unnecessary loss and reflection.

[0010]

As described above, conventionally, when a parallel optical interconnection is to be constituted by using a surface-type optical multifunctional element, it is difficult to suppress the residual reflection, and the reflection gain is suppressed. However, it is not possible to obtain a sufficient transmission gain, and it is difficult to operate stably in multistage connection.

(2) Multi-stage optical transmission that maintains a Gaussian profile cannot be performed, and a sufficient power and optical alignment margin cannot be obtained. (3) In order to receive light with light efficiency, the entire device becomes thick.

(4) The element structure is complicated and the area becomes large. There was a problem. The present invention has been devised in view of the above problems, and an object thereof is to obtain a sufficient transmission gain while suppressing a reflection gain and to operate stably even in a multi-stage connection. A planar optical multifunctional device that can maintain a Gaussian profile to increase the operating margin, enable high-efficiency light reception even with a thin absorption layer, reduce the overall layer thickness, and reduce the area with a simple configuration To provide.

[0013]

[Means for Solving the Problems]

(Configuration) In order to solve the above problem, the present invention employs the following configuration. That is, the present invention provides a first reflector having a reflectance (power reflection coefficient) for signal light of R ₁ (0 <R ₁ <1), and a reflectance of R ₂ (0 <R ₂ <) for the signal light.
1) a second reflector, a _third reflector having a reflectance R ₃ (0 <R ₃ <1) formed between the first and second reflectors, and the first and second reflectors. A light receiving portion formed between the three reflectors, an optical amplifying portion formed between the second and third reflectors, and a signal received while electrically adjusting the absorption coefficient of the light receiving portion. A means for electrically outputting a signal, a means for injecting a current into the optical amplifier to obtain a predetermined gain, a means for injecting signal light through the first reflector, and the second Means for emitting signal light through a reflector and a surface-type optical multifunctional element having a main component,
The first and second reflectors constitute a first optical resonator for a signal light wavelength, and the second and third reflectors constitute a second optical resonator for a signal light wavelength. The light receiving
The single-pass transmittance for the signal light of the portion is α (<1),
G _S (> 1)
Where α ² is approximately equal to R ₁ and G _S ² is 1
/, Characterized in that it is set to be substantially equal to R _2.

Here, preferred embodiments of the present invention include the following. (1) The net transmission gain considering the coupling loss for the signal light is 0.9 or more and 1.1 or less, and the coupling loss of the optical system for the signal light incident from the first reflector side is also considered. The net reflection gain is 10 ⁻³ or less, and the net reflection gain is 1 or less in consideration of the coupling loss with respect to the light of the signal light wavelength incident from the side of the second reflector. (2) The third reflector is composed of a distributed Bragg reflection (DBR) layer in which a semiconductor layer having a relatively low refractive index and a semiconductor layer having a relatively high refractive index are alternately stacked by a quarter wavelength. Part of the means for electrically adjusting the absorption coefficient of the light receiving unit and electrically outputting the received signal, and part of the means for injecting current into the optical amplifying unit to give a predetermined gain. It has become. (3) The third reflector includes at least a dielectric film,
The light receiving section and the optical amplifying section are electrically insulated by the dielectric layer. (4) The device functions as a surface emitting laser by causing a forward bias current to flow through the light receiving portion and operating as a second optical amplifier. (5) The light receiving section has a pin photodiode structure in which a multi quantum well light absorption layer is sandwiched between a p-type semiconductor layer and an n-type semiconductor layer. When the reverse bias voltage applied to the layer is changed, the absorption coefficient for signal light changes due to the quantum confined Stark effect (QCSE). (6) A lens system for inputting and outputting signal light is integrated.

Furthermore, the constraints on the reflectance for preventing reflection are simplified to two, α ^{2 to} R ₁ and G _S ² to 1 / R ₂ . Moreover, by increasing the reflectance R3 of the _third reflector, it is possible to realize a transmission gain sufficient for multistage connection. In this _{^{case, α 2 ~R 1, G S}} 2 ~1 / R 2
Is satisfied, the reflectance R ₃ of the third reflector is
The reflection gain can be suppressed irrespective of (<1), and multi-stage connection without an optical isolator is possible.

Therefore, according to the present invention, a surface-type optical multi-function device which solves all of the first to fourth problems is realized.
As a result, it is possible to realize a stable and high-performance parallel optical interconnection device that connects a large number of boards.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First, the basic configuration and principle of the present invention will be described. FIG. 1 is a diagram showing a basic configuration of a surface optical multifunctional device of the present invention. The surface-type optical multifunctional device of the present invention includes a first reflector ₁ having a reflectance of R ₁ for signal light,
A second reflector ₂ having a reflectance of R ₂ for signal light, a third reflector 3 formed between the first reflector 1 and the second reflector 2, and a first reflector 1 The main components are a light receiving unit 4 formed between the second reflector 3 and the third reflector 3 and an optical amplifier unit 5 formed between the second reflector 2 and the third reflector 3.

The light receiving section 4 is provided with means 6 (semiconductor layer or electrode terminal doped with impurities) for controlling an absorption coefficient and outputting a received signal as an electric signal. Is provided with a means 7 (such as a semiconductor layer doped with an impurity or an electrode terminal) for giving a predetermined gain by current injection.

The structure of the light receiving section 4 may be, for example, a pin photodiode, an MSM light receiving element, or any other light receiving element structure. The coefficient can be controlled to some extent. Further, the absorption layer of the light receiving unit 4 and the active layer of the optical amplification unit 5 may be bulk, quantum well, or strained quantum well.
The (strain) quantum well may be formed in multiple layers. In general, the use of a (strained) multiple quantum well light absorption layer or a (strained) multiple quantum well active layer is advantageous for thinning.

The signal light enters from the first reflector 1 and exits from the second reflector 2. In the meantime, a part of the signal light is absorbed by the light receiving unit 4, and is output in the form of an electric signal from the means 6 for controlling the absorption coefficient of the light receiving unit 4 and outputting the received signal as an electric signal. The optical power lost due to the loss of the optical system or the light reception is compensated by the optical amplifier 5.

The first reflector 1 and the second reflector 2 have a wavelength λ.
_A first optical resonator 8 is formed for the signal light of ₀ ,
In addition, the second reflector 2 and the third reflector 3 form a second optical resonator 9 for the signal light having the wavelength λ ₀ . The second resonator 9 is formed inside the first resonator 8 and is a kind of composite resonator having the second reflector 2 in common.

At this time, the first reflector 1 and the third reflector 3 do not constitute an optical resonator for signal light. This can be explained as follows. As described in the textbook of optics, when a plane wave is perpendicularly incident on the third reflector 3, its amplitude reflectance r ₃ is different from the case where light is incident from the first reflector 1 side and the second case. The sign is inverted when light is incident from the side of the reflector 2 of. For example, the amplitude reflectance in the case where a plane wave refractive index material of n ₂ of a material of refractive index n ₁ is incident perpendicularly is _{r 3 = (n 1 -n 2} ) / (n 1 + n 2), n 1
If <n _2, it is negative, and if n ₁ > n _2, it is positive. This is the same for other reflectors such as a distributed Bragg reflector (DBR).

Therefore, the first reflector 1 and the second reflector 2
(The optical electric field has the same phase in one round) and the second reflector 2 and the third reflector 3 form a resonator 9.
Is formed (that is, the reflection phases of the first reflector 1 and the third reflector 3 are the same), the light reciprocating between the first reflector 1 and the third reflector 3 has a phase every round. Are inverted, and are canceled by interference.

In the present invention, there is a difference α between the single-pass transmittance α for the signal light of the light receiving section 4 and the reflectance R ₁ of the first reflector 1.
^{2 to} R ₁ , and the single-pass gain G _S of the optical amplifier 5 for the signal light and the reflectance R _{2 of the second} reflector ₂
Relationship G _{S ²} ~1 / R ² is established between. At this time, the fact that the reflection gain G _S for the light incident from the first reflector 1 side is suppressed will be described in the case of FIG. 2A in which the configuration of FIG. 1 is simplified.

In FIG. 2A, the light receiving section 4 has a refractive index n ₁ ,
The optical amplifier 5 is made of a uniform material having a single-pass gain g ₁ (= α ^1/2 <1) with respect to the amplitude, and the optical amplifier 5 has a refractive index n ₂ (> n ₁ ).
It is made of a uniform material having a single-pass gain g ₂ (= G _S ^1/2 > 1) with respect to the amplitude. It is assumed that the outside of the element is air (refractive index = 1). Two materials 4 and 5 having different refractive indexes
Are in contact with each other, the boundary surface acts as the third reflector 3.

The amplitude reflectance of the third reflector 3 viewed from the optical amplifier 5 is r ₃ = (n ₂ −n ₁ ) / (n ₁ + n ₂ ) (>)
0). Third amplitude reflectance of the reflector 3 as viewed from the light receiving unit 4 is given by -r _3. It is assumed that a plane wave is vertically incident from the side of the first reflector 1. Amplitude reflectance for light incident on the first reflector 1, -r ₁ = (1
−n ₁ ) / (1 + n ₁ ) (<0), and the amplitude reflectance for the light emitted from the second reflector 2 is r ₂ = (n ₂ −1)
/ (N ₂ +1) (> 0). Here, FIG.
As shown in (b), when the portion from the third reflector 3 to the second reflector 2 is considered as an etalon 9, its amplitude reflectance _gr3 is

[0027]

(Equation 1) Given by Here, φ ₂ is a phase change of light transmitted through the optical amplification unit 5 in a single pass, and mπ (m
Is an integer). Next, as shown in FIG. 2 (c), the be regarded overall as one of the resonator 8, the entire amplitude reflectance g _r
Is

[0028]

(Equation 2) Given by Here, φ ₁ is a phase change of light transmitted through the light receiving unit 4 in a single pass, and m′π (m
Is an integer).

At the resonance frequency, exp (2iφ ₁ ) = exp
Since (2iφ ₂ ) = 1, α ² = R ₁ and G _S ² =
1 / R _2, ie if g ₁ ² = r ₁ and ^{_{g 2 2 r 2 = 1,}} , the molecules of the above formula

[0030]

(Equation 3) Therefore, regardless of r ₃ (however, r ₁ where the denominator is also 0)
= 1, r ₃ = 1), and g _r = 0. Therefore, α ² = R ₁ (where 0 <α <1) and G _S ² = 1
/ R ₂ (> 1) holds (as long as r ₃ <1)
Reflection gain at the resonant wavelength regardless of the value of R ₃ will be suppressed. The fact that the reflection gain is similarly suppressed even in a more complicated structure will be described in a later-described embodiment.

To explain it a little more clearly, g ₂ ²
If r ₂ = 1, then g _r3 = 1, so that the optical electric field incident on the third reflector 3 from the light receiving unit 4 is equal to the optical electric field returning from the third reflector 3 to the light receiving unit 4. At this time, the amplitude reflectance of the light having the resonance wavelength incident on the first reflector 1 is:

[0032]

(Equation 4) It is represented by In the present invention, since g ₁ ² = r ₁ , g _r =
That is, it becomes 0. In other words, g _r3 = 1 (g ₂ ²
r ₂ = 1) and g ₁ ² = r ₁ , the first reflector 1
Light reflected at (21) and light receiving unit 4 (18, 19, 20)
The entire reflected light is suppressed by the interference between the light that is multiple-reflected by the first reflector 1 (21) and the second resonator 9 across the.

The above two relational expressions, α ² = R ₁ , and G
_S ² = 1 / R ₂ does not mean that both sides must exactly match, and there is no practical problem even if it is shifted by about several%, for example, unless the transmission gain is extremely large. The transmission gain only needs to be able to compensate for the loss of the optical coupling between the boards, so that the transmission gain does not need to be so large as long as it is coupled by a microlens or the like.

First, second and third reflectors 1, 2, 3
May be composed of any type of reflector. For example, it may be a reflector only in contact with a substance having a different refractive index, a semiconductor DBR layer, a dielectric multilayer film, or a metal film. Further, the first and second reflectors 1 and 2 may be composite reflectors having a phase adjustment layer between a plurality of reflectors. However, in any case, it is preferable that the material constituting the reflector absorb as little as possible the signal light.

If the absorption layer and the active layer are provided in accordance with the position of the antinode of the standing wave in the resonator, it is possible to receive and amplify light with higher efficiency. On the other hand, when the first resonator is configured by a composite reflector provided with a phase adjustment layer between a plurality of reflectors,
By displacing the active layer from the position of the antinode of the resonator, the amplification factor is reduced, but the wavelength band can be widened.

As the reflectance R _{3 of} the third reflector 3 increases, the transmission gain of the surface-type optical multifunctional device of the present invention can be increased. Moreover, if the above two relationships are satisfied, it is possible to suppress the reflection gain with respect to the light incident from the first reflector 1 side while increasing the transmission gain. But R
_{As 3} approaches 1, the transmission wavelength band, the reflection suppression wavelength band, and the design margin become narrower.
There is a tendency that the reflection gain with respect to the light incident from the side increases. In order to realize a stable multi-stage connection, both the reflection gain and the transmission gain for incident light from the opposite direction must not be extremely increased.

However, when applied to an optical bus, the net transmission gain may be about 1 on average, and need not be so high. Therefore, for the forward propagating signal light, if the net reflection gain per stage including the coupling loss of the optical system is suppressed to 10 ⁻³ or less, the net reflection gain per stage including the coupling loss of the optical system is reduced. By setting the transmission gain to 0.9 or more and 1.1 or less and setting the net reflection gain to 1 or less for incident light from the opposite direction, even for a multistage connection of about 20 to 30 steps,
A practically sufficient band, margin, and stability can be secured.

Hereinafter, specific embodiments of the present invention will be described. (Embodiment 1) FIG. 3 is a diagram schematically showing a cross-sectional structure of a surface-type optical multifunctional device having a wavelength band of 0.98 μm according to a first embodiment of the present invention.

This surface type optical multifunctional element is an n-type (001)
It is formed on a GaAs substrate 10. The layer structure is, in order from the bottom, a lower DBR layer 11 (second reflector) in which twelve pairs of quarter-wave n-type Al _0.7 Ga _0.3 As layers and quarter-wave n-type GaAs layers are alternately stacked. 2), a quarter wavelength n-type AlAs spacer layer 12 (part of the second reflector 2), an n-type Al _0.3 Ga _0.7 As cladding layer 13, and an undoped strain In _0.2 Ga having a thickness of 6 nm. A strained multiple quantum well (MQW) active layer 14 in which six layers of _0.8 As layers and seven layers of undoped GaAs layers having a thickness of 6 nm are stacked, p-type Al _0.3 G
a _0.7 As clad layer 15, quarter wavelength p-type AlA
s spacer layer 16 (part of the third reflector 3), five quarter-wavelength p-type GaAs layers and quarter-wavelength p-type Al
A central DBR layer 17 (a part of the third reflector 3) in which four layers of _0.3 Ga _0.7 As layers are laminated, and p-type Al _0.3 Ga _0.7
As clad layer 18, 10 pairs of undoped strained In _0.2 Ga _0.8 As layer having a thickness of 6 nm and undoped G layer having a thickness of 5 nm
MQW light absorption layer 19 made of aAs, n-type GaAs cladding layer 20, and upper DBR layer 21 in which two pairs of a quarter wavelength Al _x O _y layer and a quarter wavelength GaAs layer are stacked.
(First reflector 1).

The optical amplifying section 5 includes the n-type cladding layer 13 and the p-type cladding layer 15 sandwiched between the second reflector 2 and the third reflector 3. This is equivalent to five wavelengths. Also, the p-type cladding layer 18 and the n-type cladding layer 20 sandwiched between the third reflector 3 and the first reflector 1
Constitute the light receiving section 4 and the total film thickness is 1.5
It is equivalent to the wavelength. A first resonator 8 is configured by the first reflector 1 and the second reflector 2, and a second resonator 9 is configured by the second reflector 2 and the third reflector 3. MQ
The W active layer 14 and the MQW light absorption layer 19 are respectively provided at positions corresponding to antinodes of standing waves standing in the resonator.

The portion above the n-type AlAs spacer layer 12 is processed into a mesa 22 having a diameter of 40 μm. The portion above the p-type cladding layer 18 has a diameter of 2 at the center.
An electrode 24 is formed on the p-type DBR layer 17 around the mesa portion 23 except for the mesa portion 23 of 0 μm. Portion 1 below electrode 24 in p-type DBR layer 17
7b, for the purpose of lowering the electric resistance, for example, Be, M
A p-type impurity such as g, C, Zn, or Cd may be doped at a high concentration.

Al _x O _y / GaAs upper DBR layer 21
Is formed by selectively oxidizing the AlAs / GaAs multilayer film (two pairs). At this time, the thickness of the AlAs layer is adjusted so that the thickness of the Al _x O _y layer after oxidation becomes equivalent to a quarter wavelength. The Al _x O _y layer may contain an impurity such as As _x O _y . Al _x O _y / GaAs
The upper DBR layer 21 has a diameter of 10 μm, and a dielectric anti-reflection film 25 is provided thereon. An electrode 2 is formed on the n-type GaAs cladding layer 20 in the surrounding area.
6 are provided.

The AlAs spacer layers 12, 16 are present only in the central portion having a diameter of about 7 μm, and the peripheral portion is formed by selective oxidation of AlAs from outside the mesa.
1 _x O _y films 27 and 28 are formed. The Al _x O _y films 27 and 28 function as insulating layers for current confinement, and also function as resonator apertures. Since the Al _x O _y films 27 and 28 are porous, they do not cause serious strain or stress in the main part of the device.

Epitaxial growth layer (lower DBR layer 11)
The total film thickness of the upper part) is as thin as about 4 μm despite the vertical integrated structure. The thickness of the substrate 10 is about 1
00 μm. A dielectric anti-reflection film 29 is formed in an optical path below the substrate 10, and an electrode 30 is formed around the dielectric anti-reflection film 29.

When a current is injected between the electrodes 24 and 30, the two AlAs spacer layers 1 of the MQW active layer 14 are formed.
A high-density carrier is injected into the optical amplifier 14a narrowed by 2 and 16, and a stimulated emission gain is generated. That is, the electrodes 24,
30, p-type and n-type semiconductor regions 17, 16, 15, 13, 12, from the electrodes 24, 30 to the optical amplifier 14 a
11 and 10, Al _x O _y films 27 and 2 for current confinement
8 and an externally provided current injection circuit
Means 7 for obtaining a predetermined gain by injecting a current into the circuit.

The light absorbing layer 1 is provided between the electrodes 24 and 26.
A reverse bias is applied so that the absorption coefficient for the signal light of 0 becomes a predetermined value. Carriers generated by light reception in the light absorbing layer 19 are extracted by the reverse bias voltage, and are extracted in the form of a current generated between the electrodes 24 and 26. That is, these electrodes 24 and 26 and the pin photodiode structures 17 to 21 formed between them are:
It functions as a means 6 for controlling the absorption coefficient by voltage and extracting the received signal as an electric signal.

The substrate 10 is mounted on a heat sink having a light transmitting hole. The signal light enters through the upper anti-reflection film 25 by a lens optical system provided outside so as to be focused near the aperture. The coupling efficiency is about 60% due to the small aperture. Part of the incident light is absorbed by the light receiving section 4 and detected as a current generated between the electrodes 24 and 26.

The loss associated with the reception and the coupling loss of the optical system are compensated by the optical amplifier 5, and are relayed to the next stage via the lower antireflection film 29 and an appropriate lens system provided outside. The coupling loss of the optical system of the outgoing light is negligible since the lens is larger.

In order to increase the precision of optical alignment with the outside, it is preferable to attach a microlens or the like to the substrate with a precise alignment by mask alignment. The lens system is also provided with a means for preventing reflection (such as an anti-reflection film).

The reflectance R ₁ of the _first reflector ₁ has a wavelength λ ₀
= 0.98 μm is about 80.7% for the signal light,
The reflectance R ₂ of the second reflector 2 for the signal light is about 82.
8%. Here, the absorption coefficient of the light receiving unit 4 for the signal light is 18000 cm ^-1 (single-pass transmittance α to 0.897
6) The applied voltage is adjusted so as to satisfy 6), and the injection current is adjusted such that the gain coefficient of the optical amplification unit 5 with respect to the signal light is 26000 cm ⁻¹ (single path gain G _S 〜1.0981). And At this time, since the relationship between α ^{2 and} R ₁ is established with an error of 4.2% and the relationship between G _S ^{2 and} 1 / R ₂ is established with an error of 0.8%, the reflection gain for the forward propagating light is obtained. Is suppressed.

At the resonance wavelength, α ^{2 to} R ₁ and G _S ² to 1 / R ₂
When the relationship is established that the forward reflection gain G _S is suppressed has been mentioned previously, it is shown here that G _S is suppressed even complex structures such as the embodiment.

FIG. 4 shows the distribution of the optical electric field intensity F along the optical path when the light of the resonance wavelength is input from the first reflector 1 (21) side to the surface-type multifunctional element of this embodiment. FIG. FIG. 5 shows a case where light having a resonance wavelength is input to the surface-type optical multifunctional device of the present embodiment from the first reflector 1 (21) side.
Power distribution of elements inside the forward wave (P _F; solid line) and power distribution of backward wave (P _B; dotted line). FIG. In both figures, the refractive index distribution is shown by solid lines to show the layer structure.

As shown in FIG. 4, the first reflector 1 (2
Since the first resonator 8 is formed between 1) and the second reflector 2 (12, 11), a standing wave of the optical electric field stands between them. In the first reflector 1 (21) and the second reflector 2 (12, 11), the node of the standing wave is located at the boundary where the refractive index decreases from the inside of the resonator to the outside. .

On the other hand, the third reflector 3 (16, 17)
Since the phase is the same as that of the first reflector 1 (21), the second resonator 9 is formed between the first reflector 1 (21) and the second reflector 2 (12, 11). ) Does not form a resonator. That is, in the second reflector 2 (12, 11), a node of the standing wave is formed on the surface where the refractive index decreases outward from the optical amplifying unit 5 (13 to 15). The antinode of the standing wave is located on the surface where the refractive index decreases from 4 toward the outside. Therefore, the first reflector 1 (21)
And the signal light reciprocating between the third reflector 3 (16, 17) is
Since the phase is inverted each time the circuit makes one round, it is canceled by interference.

Therefore, the surface-type optical multifunctional device of the present embodiment has the second resonator 9 included in the first resonator 8 using the second reflector 2 as a common reflector. It can be considered to have a double resonator structure. First resonator 8
Includes a light receiving section 4 and an optical amplifying section 5, of which the light receiving section 4 is located outside the second resonator 9 and the optical amplifying section 5 is located inside the second resonator 9. I have.

The electric field strength and optical power of the light receiving section 4 and the optical amplifier section 5 are larger than those of the outside due to the confinement effect of the first resonator 1, and the electric field strength and optical power of the optical amplifier section 5 are higher than those of the outside. Due to the confinement effect of the two resonators 2, the electric field intensity and the optical power of the light receiving section 4 are further increased. Therefore, high sensitivity reception and a sufficient transmission gain can be obtained even though the light absorption layer 19 and the active layer 14 are thin.

In such a configuration, the third reflector 3
The reflectance G _S ^{2 of} the second resonator 9 viewed from (16, 17)
Since R ₂ is set substantially equal to 1, as shown in FIG. 5, in the third reflector 3 (16, 17), the optical power P _F of the forward wave and the optical power P _B of the backward wave are equal to each other. It is almost equal. Since the third reflector 3 (16, 17) forms a resonator only between the third reflector 2 (11) and the second reflector 2 (11),
The optical power increases on the side of the optical amplifying unit 5 (13 to 15), and P _F increases over the entire third reflector 3 (16, 17).
~ P _B holds. Of course, in order to do this, the loss of the third reflector 3 (16, 17) needs to be small enough to be ignored. However, the third reflector 3 (1
Even if there is a small loss in (6, 17), the effect can be offset to some extent by making the gain of the optical amplification unit 5 slightly larger.

Further, when α is set so that the relationship α ^{2 to} R ₁ is satisfied, the reflected light (incident light power × R ₁ ) of the first reflector 1 (21) and the light receiving section 4 reciprocate. Since the light (incident light power × α ² ) has the opposite phase and the same power, the reflection of the entire element viewed from the first reflector 1 (21) is suppressed by interference cancellation.

In the present embodiment, it is necessary to make the square of the single-pass gain G _S of the optical amplifier 5 equal to the reflectance R ₂ of the second reflector 2. The single-pass gain and resonance wavelength of the optical amplifier 5 change depending on the current injected into the optical amplifier 5 and the temperature.
By adjusting the injection current while controlling the resonant wavelength at a temperature, to match the resonance wavelength and the signal light wavelength, and G _S ² to R
₂ can be realized.

The single-pass transmittance of the light receiving section 4 can be controlled by changing the voltage applied to the quantum well light absorption layer. That is, the quantum confined Stark effect (QCS
When E) is used, the absorption edge wavelength and the absorption spectrum change greatly change depending on the electric field applied to the well layer, so that the absorption coefficient at the signal light wavelength can be changed.

The surface optical multifunctional device of this embodiment operates cw once the current and voltage are set once at first, so that the change in the calorific value of the device itself under the equilibrium condition is small, and the ambient temperature is small. Even if temperature feedback control is performed only to control the center wavelength with respect to the change in, the function is sufficiently stable.

FIG. 6 shows the relationship between the material gain of the optical amplification unit 5 and the material gain.
Element overall transmission gain G _T, forward reflection gain G _R, and the change of the backward reflection gain G _B shown. Forward reflection gain G _R are not generally match the material gain and reverse reflection gain G material _{gain B} is suppressed to be suppressed. However, the gain range in which the reflection gain can be suppressed is not so narrow and can be controlled relatively easily.

In fact, the absorption coefficient of the light receiving section 4 is 18000c.
m ^-1 (α to 0.8976), and the gain coefficient of the optical amplifier 5 is 2
In the case of 6000 cm ^-1 (G _S １．０1.0981), the transmission gain of the element itself at the signal light wavelength is about 1.66, the reflection gain for the forward propagating light is about 0.000337, and the reflection gain for the backward propagating light is It is calculated to be about 0.478.
In this case, despite a 4.2% error in the relationship between α ^{2 and} R _1, the reflection gain for the forward propagating light is 10 ^−3.
It is suppressed below.

The gain coefficient of the optical amplifier 5 is set to 26500
Increasing to cm ^-1 reduces the reflectivity to 2.4 × 10 ^-5 , despite an increase in the error of G _S ² / R _{2 １1} . That is, the error of α ^{2 to} R _{1 and} the error of G _S ² / R ₂ to 1 are:
It is also possible to offset to some extent, practically there is sufficient margin in the control of the α and G _S.

When the coupling loss of the optical system is also taken into consideration, the net transmission gain is about 0.993, the net reflection gain for forward propagating light is about 0.0002, and the net reflection gain for backward propagating light is about 0. .478. In the case where the surface optical multifunctional devices of this embodiment are connected in 30 stages, even if the net transmission gain of each stage is increased to 1.1, the net reflection gain of the surface optical multifunctional devices at both ends is zero. .0002 and 0.478
So, round-trip gain, even if it meets the resonance conditions if there is a phase 1.1 ⁶⁰ × 0.0002 × 0.4
78 = 0.0291 << 1. Therefore, the instability of the optical power caused by the gain and the interference due to the multiple reflection can be suppressed to a level that causes no practical problem.

If the signal light power is set near the gain saturation level, the transmission gain of some stage increases if the transmission gain increases and the signal light power becomes too large. An increase in average transmission gain can be suppressed. If the error of the transmission gain can be suppressed to a small value by such a method, further multistage connection is possible.

In the present embodiment, since the light receiving section 4 is formed together with the optical amplifying section 5 in the integrated resonator 8,
There is a drawback that spontaneous noise light generated in the optical amplifier 5 is also received. In addition, when multiple stages are connected, spontaneous noise radiated forward accumulates (this problem is similar to that of the prior art surface type optical amplifier device as shown in FIG. 11). Therefore, setting the signal light power to a high level near the gain saturation level is preferable also from the viewpoint of improving the signal-to-noise ratio. In addition, by devising a receiving circuit or a transmission method, a reception that cancels a noise level (for example,
For example, the signal light is transmitted in the RZ format, and the receiving circuit subtracts the noise level received at a timing when there is no signal light. ) Is desired.

In the surface-type optical multifunctional device of the present invention, spontaneous noise emitted backward (incident side) is considerably reduced due to the existence of the absorbing layer and the balance of the reflector (for example, it can be reduced by two orders of magnitude). ). This is advantageous as compared with the prior art surface type optical multifunctional device.

[0069] Figure 7 is a diagram showing the wavelength dependence of the transmission gain G and the forward reflection gain G _R of the surface optical multifunction element in the present embodiment. The center wavelength is 978.14 nm, and the gain bandwidth at the point where the transmission gain is reduced by 20% is 1.37 nm. The center wavelength can be shifted by design or temperature control. Since the (001) substrate is used and the element shape viewed from the top is also substantially circularly symmetric, the polarization dependence of the gain is negligible.

Finally, in the structure of the planar optical multifunctional device of the present embodiment, p-type GaAs / p-type Al _0.3 Ga _0.7 A
The number of pairs (A) of the sDBR layer 17 (part of the third reflector 3)
l _0.3 Ga _0.7 As layer third reflector 3 of the reflectance R ₃ when defined) changed by the number of the transmission gain G of the device, forward reflection gain G _R, reverse reflection gain G _B, and transmission The change in bandwidth with a 20% gain down is shown in Table 1 below.

[0071]

[Table 1]

As described above, the transmission gain and the backward reflection gain increase as R ₃ increases. However, since the error margin for the above two conditional expressions is reduced, the forward reflection gain is gradually increased. Nevertheless, in the range of up to 15 pairs (R ₃ ~50%), forward reflection gain G _R are suppressed to less than ^10-3. Under the conditions of use as a normal optical bus, a low transmission gain as described in the present embodiment is sufficient, and a sufficient margin can be secured.

In the present embodiment, since the light receiving section and the optical amplifying section are arranged in a line along the same signal optical path, the element area can be reduced, and the signal light beam due to the light beam in the light receiving section and the invalid area is reduced. No change in profile. Since the light receiving part is formed in a resonator integrated with the optical amplifier, the optical power in the light receiving part can be increased by the amplification effect and the effect of the resonator. Can be received. Moreover, since only three reflectors are required, the thickness of the entire device can be reduced as compared with the case where the light receiving element and the optical amplifier are configured in another resonator and connected in series.

Conditions for suppressing the reflection gain are α ^{2 to} R
_1, and it is collected in the two G _{S ²} ~1 / R ^2. This condition can be realized individually and easily by gain control by injection current and absorption control by QCSE. At this time, by setting the reflectivity R ₃ of the third reflector appropriately, it is possible to compensate for the coupling loss of the optical system and obtain a transmission gain sufficient for performing multi-stage connection. Also,
There are no steps or electrodes in the light incident area, and no extra reflection or absorption occurs due to these.

Therefore, according to the surface type optical multifunctional device of the present embodiment, a sufficient transmission gain can be obtained while suppressing the reflection gain, and a stable operation can be realized even in a multistage connection without an optical isolator. In addition, the Gaussian profile can be maintained even at the time of multi-stage relay, and the operation margin can be increased. Furthermore, highly efficient light reception is possible even with a thin absorption layer, and the overall layer thickness can be reduced. In addition, the surface optical multifunctional device of the present embodiment has a simple device structure, is easy to manufacture, and has a small device size and a small ineffective area. As a result, it is possible to realize a stable and high-performance parallel optical interconnection device that connects a large number of boards.

(Embodiment 2) FIG. 8 is a diagram schematically showing a cross-sectional structure of a surface-type optical multifunctional device according to a second embodiment of the present invention.

This surface type optical multifunctional device is composed of (001) Ga
It is formed on an As substrate 40. The layer structure is, in order from the bottom, a quarter wavelength Al _x O _y layer 41, a half wavelength GaAs spacer layer 42, a quarter wavelength Al _x O _y layer, and a quarter wavelength undoped layer. A multilayer reflection film 43 composed of 2.5 pairs of GaAs layers, a p-type AlGaAs cladding layer 4
4. A strained multiple quantum well (MQW) active layer 45 in which six layers of an undoped strained InGaAs layer having a thickness of 6 nm and five layers of an undoped GaAs layer having a thickness of 6 nm are stacked, and n having a thickness of 30 nm
Type AlAs spacer layer 46, n-type AlGaAs cladding layer 47, the central portion reflective layer 48 made of Al _x O _y layer of tithe wavelength (third reflector 3), the thickness of the p-type GaAs cladding layer 49,10 pairs 6 nm undoped strained InGaAs
MQW light absorption layer 50 comprising a well layer and an undoped GaAs barrier layer having a thickness of 6 nm, an n-type AlGaAs cladding layer 51, a quarter wavelength Al _x O _y layer and a quarter wavelength undoped GaAs layer 2.5 Multilayer reflective film 5 composed of pairs
2 and a half-wavelength undoped GaAs spacer layer 53.

These layer structures are processed into multi-stage mesas 54 as shown in FIG.
On the peripheral portions of 49 and 51, electrodes 55 and 5 are provided, respectively.
6, 57, 58 are formed. The AlAs spacer layer 46 is selectively oxidized except for a central aperture portion of about 5 μm to form an Al _x O _y current confinement layer 59. The current injected into the active layer 45 is narrowed by the current narrowing layer 59 at the central aperture portion.

The surface 60 of the uppermost half-wavelength GaAs spacer layer 53 is in direct contact with air. An antireflection film 61 is formed on the back surface of the substrate 40. The signal light is supplied to the external optical system by a half-wavelength GaAs spacer layer 5.
The light is narrowed down from the surface 60 of the device 3 to the element and emitted through the anti-reflection film 61.

N-type clad layer 51, strained MQW light absorbing layer 5
The 0 and p-type cladding layers 49 correspond to the light receiving section 4, and the thickness thereof corresponds to 2.4 wavelengths with respect to the signal light wavelength.
Clad layers 49 and 51, electrodes 57 and 58, and electrode 5
The external circuit connected via the elements 7 and 58 constitutes means 6 for controlling the absorption coefficient of the light receiving section 4 and outputting the received signal as an electric signal.

The p-type cladding layer 44 and the strained MQW active layer 4
5. AlAs spacer layer 46 and n-type cladding layer 47
Corresponds to the optical amplification unit 5 and its thickness is equivalent to two wavelengths.
The cladding layers 44 and 46, the electrodes 55 and 56, the current confinement layer 59, and the external circuit connected via the electrodes 55 and 56 constitute the means 7 for controlling the gain of the optical amplifier 5. .

The interface 60 between the multilayer reflective film 52 and the half-wavelength spacer layer 53 and its air constitutes the first reflector 1 (composite reflector), and the multilayer reflective film 43 and the half-wavelength spacer layer 42 And the quarter wavelength Al _x O _y layer 41 constitute the second reflector 2 (composite reflector). Note that the wavelength band can be expanded by using a composite reflector having such a half spacer layer sandwiched therein (SFLim and CJChan).
g-Hasnain, IEEE Photonics Technology Letters, vol.
7, pp. 1240-1242, 1995).

A first resonator 8 (resonator length is equivalent to 4.5 wavelengths) is formed between the first reflector 1 and the second reflector 2, and the third reflector 3 and the second resonator A second resonator 9 (resonator length is equivalent to two wavelengths) is formed between the reflectors 2. The light absorbing layer 50 is provided in accordance with the antinode of the standing wave standing on the first resonator 8, and although the light absorbing layer 50 is thin,
High sensitivity reception is possible. The active layer 45 is located near the node of the standing wave of the resonator, which is effective for enhancing the effect of the composite reflector and broadening the band. Nevertheless, due to the effects of the first and second resonators 8 and 9, a sufficient transmission gain for signal light is realized despite the thin active layer 45. (If the active layer 45 is provided at the position of the antinode of the standing wave, the gain efficiency is further increased, but the band is narrowed.) The basic operation principle of the present embodiment is the same as that of the first embodiment. . That is, the single-pass transmittance α of the light receiving unit 4 is determined by using the QCSE of the light absorption layer 50 and the electrodes 57 and 58.
Can be controlled via α to R ₁ ^1/2 . Moreover, single pass gain G _s of the optical amplifier 5, the electrode 5
The current can be controlled to G _s ＲR ₂ ^-1/2 by the current injected into the aperture portion 59 of the active layer 45 via the layers 5 and 56.

In this embodiment, the reflection height of each reflector is R ₁
= 0.8304, R ₂ = 0.7971, R ₃ = 0.15
79, and α = 0.9162, G _s = 1.120 satisfies this condition.

FIG. 9 shows a relationship between the traveling wave power P _F (solid thick line) and the backward wave power P _B (fine broken line) when α and G _S are set so as to substantially satisfy this condition (error 1% or less). FIG. The thin solid line in the figure shows the distribution of the refractive index. Also in this embodiment, similarly in the first embodiment, are substantially equal P _F and P _B in the vicinity of the third reflector 3 (48). At this time, the transmission gain at the resonance wavelength is G = 2.2.
0, which is larger than in the first embodiment. However, the forward reflection gain is sufficiently suppressed to G _R = 1.14 × 10 ⁻³ . Incidentally, reverse reflection gain G _B = 1.
53.

[0086] Figure 10 shows the spectrum of the transmitted gain G and the forward reflection gain G _R in the above condition of the surface-type optical multi-functional device of this embodiment. Normally, there is a trade-off between the magnitude of the gain and the bandwidth. However, in the present embodiment, the transmission bandwidth is large compared to the first embodiment, but the wide bandwidth (the transmission gain increases from the peak). 2.086 nm with a wavelength width falling by 20%). This is because the second reflector 2 has Al _x O _y / GaAs having a large refractive index difference.
And the use of the composite reflectors 1 and 2.

The surface type optical multifunctional device of this embodiment has a thin epitaxial growth layer of about 3 μm and a relatively simple structure. It is smaller in size than the conventional surface type optical multifunctional device. The change in the beam profile during optical relaying is small, and a sufficient operation margin can be obtained. These effects are almost the same as those in the first embodiment.

In the surface type optical multifunctional device of the present embodiment, the light receiving section 4 and the amplifying section 5 are electrically insulated by the Al _{x Oy} film 48. Interference can be prevented. For example, the reverse bias applied to the light absorption layer 50 does not change due to the change in the voltage drop due to the current flowing through the light amplification unit 5.

The external circuit of the surface-type optical multifunctional device of this embodiment is set so that the light receiving section 4 can be forward-biased. When the light receiving unit 4 is forward-biased, the light receiving unit 4 functions as a second optical amplifier 4 '. For example,
The single-pass gain of the second optical amplifier 4 ′ is set to 1.08 without changing the single-pass gain (1.12) of the original optical amplifier 5.
When the gain is increased to 8 (gain coefficient of 14000 cm ^-1 ), the surface-type multifunctional element of this embodiment starts laser oscillation. If the surface optical multifunctional device of this embodiment is applied to an optical interconnection between boards, the same device can be used as a light source or a light receiving / relaying device.

(Modifications and Applications) The present invention can be variously modified and applied in addition to the above embodiment. For example, the wavelength is not limited to the 0.98 μm band,
Materials are also various III-V semiconductors (for example, InGaAsP
System, InGaAlAs system, InGaAlP system, InGa
AlN system, GaNP system, GaInNAs system, InGaAs
1N-based, InGaAlAsSb-based, etc.), II-VI group semiconductors (for example, ZnCdMgSSe-based, HgCdTe-based, etc.), chalcopyrite semiconductors, IV group semiconductors (Si, G
e, C, SiC type, SiGe type, etc.), magnetic semiconductors, or these semiconductors and other materials (for example, metal, dielectric film, glass, amorphous film, sapphire, ceramic, liquid crystal, plastic, polyimide, resin, etc.) Organic materials and the like) may be applied to a structure or the like combined with a hybrid.

By using a substrate bonding technique, an epitaxial lift-off method, or the like, material systems manufactured in different growth steps can be integrated. For example, it is possible to integrate with a CMOS circuit manufactured on a Si substrate or to provide a beam steering function by integrating with a hologram using liquid crystal.

The device structure is not limited to the above-described embodiment, but can be applied to various forms suitable for materials.
For example, the structure of the light receiving section is not limited to the pin photodiode structure. If the single-pass transmittance can be controlled to a predetermined value, it can be used as an intersubband absorption light receiving element or an optical bistable element (eg, SEED). However, other structures may be used. Depending on the structure of the light receiving element, a non-linear operation (such as a switch operation) can be performed instead of the linear reception. In addition, various modifications can be made without departing from the scope of the present invention.

[0093]

As described above, according to the present invention, a third reflector is provided between a first reflector and a second reflector.
A light receiving unit is provided between the first and third reflectors, and an optical amplifying unit is provided between the second and third reflectors, and the first and second reflectors provide a first optical resonator for signal light. Since the second and third reflectors are configured to form the second optical resonator for the signal light, they have a sufficient transmission gain, the reflection gain is suppressed, and the device operates stably even when connected in multiple stages, It is possible to realize a planar optical multifunctional device having a small change in a light beam profile, a large operation margin, a simple structure, a small layer thickness, and a small device area.

[Brief description of the drawings]

FIG. 1 is a diagram schematically illustrating a basic configuration of a surface-type optical multifunctional device of the present invention.

FIG. 2 is a diagram for explaining the operation principle of the surface-type optical multifunctional device of the present invention.

FIG. 3 is a diagram schematically illustrating a cross-sectional structure of the surface-type optical multifunctional device according to the first embodiment.

FIG. 4 is a view showing an electric field distribution inside the surface-type optical multifunctional device of the first embodiment.

FIG. 5 is a view showing optical power distributions of a forward wave and a backward wave inside the surface-type optical multifunctional device according to the first embodiment.

FIG. 6 is a cross-sectional view of the surface optical multifunctional device according to the first embodiment;
FIG. 9 is a diagram illustrating changes in transmission gain and reflection gain when the material gain of the optical amplifier is changed.

FIG. 7 is a diagram showing a transmission gain spectrum and a reflection gain spectrum of the surface-type optical multifunctional device of the first embodiment.

FIG. 8 is a diagram schematically illustrating a cross-sectional structure of a planar optical multifunctional device according to a second embodiment.

FIG. 9 is a diagram showing the optical power distribution of a forward wave and a backward wave inside a surface-type optical multifunction element according to a second embodiment.

FIG. 10 is a diagram showing a transmission gain spectrum and a reflection gain spectrum of the surface-type optical multifunctional device according to the second embodiment.

FIG. 11 is a diagram schematically illustrating a cross-sectional structure of a conventional surface-type optical multifunctional element.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... 1st reflector 2 ... 2nd reflector 3 ... 3rd reflector 4 ... Light-receiving part 5 ... Optical amplifier 6 ... For controlling the single pass transmittance of a light-receiving part, and taking out a reception signal. Means 7: Means for controlling the gain of the amplification unit 8: First resonator 9: Second resonator 10, 40 ... Semiconductor substrate 11, 17 ... GaAs / AlGaAs DBR layer 12, 16, 46 ... AlAs layer 13 , 15,18,20,44,47,49,51 ... clad layer 14, 45 ... active layer 19,50 ... light absorbing layer 21,43,52 ... GaAs / Al _x O _y multilayer 22,23,54 ... mesa structure 24,26,30,55,56,57,58 ... electrodes 25,29,61 ... antireflection film 27,28,41,48,59 ... Al _x O _y layer 42, 53 ... half-wave spacer 60: Interface between air and GaAs

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-4-249368 (JP, A) JP-A-7-162081 (JP, A) (58) Fields investigated (Int.Cl. ⁶ , DB name) H01S 3/18

Claims (6)

(57) [Claims] 1. A reflectance (power reflection coefficient) for a signal light.
Is a first reflector of R ₁ , the reflectance for the signal light is a _second reflector of R ₂ , a third reflector formed between the first and second reflectors, A light receiving unit formed between the first and third reflectors, an optical amplifying unit formed between the second and third reflectors, and electrically adjusting an absorption coefficient of the light receiving unit. Means for electrically outputting the received signal, and means for injecting a current into the optical amplifier to give a predetermined gain, and means for injecting signal light through the first reflector. Means for emitting signal light through the second reflector, wherein the first and second reflectors form a first optical resonator for the signal light, and the second and the third reflector comprises forming a second optical resonator with respect to the signal light, single pass loss for the signal light of the light receiving portion The α (<
1) The single-pass gain of the optical amplifier for signal light is G
_{When S} (> 1), α ² is approximately equal to R ₁ and
G _S ² is set to be approximately equal to 1 / R ₂
Surface optical multifunction element characterized by that. 2. A distributed Bragg reflector (DB) in which a semiconductor layer having a relatively low refractive index and a semiconductor layer having a relatively high refractive index are alternately stacked by a quarter wavelength.
R) a part of means for electrically adjusting the absorption coefficient of the light receiving section and electrically outputting a received signal, and injecting a current into the optical amplifying section to provide a predetermined gain; 2. A surface optical multifunctional device according to claim 1, wherein said surface optical multifunctional device is a part of a means for performing said operation. 3. The third reflector includes at least a dielectric film, and the light receiving section and the optical amplifying section are electrically insulated by the dielectric layer. 2. The planar optical multifunctional device according to 1. 4. A net transmission gain in consideration of a coupling loss with respect to a signal light, which is 0.9 or more and 1.1 or less, and a coupling loss of an optical system with respect to a signal light incident from the first reflector side. wherein the reflection gain of the net in consideration does not exceed 10 ^-3, and the second reflection gain of the reflector of the coupling loss with respect to light of the signal light wavelength incident from the side also considered net is 1 or less The surface type optical multifunctional device according to claim 1, wherein 5. The surface-type multifunctional optical device according to claim 1, wherein a forward bias current is supplied to said light receiving portion to operate as a second optical amplifying portion so as to function as a surface emitting laser. element. 6. The light receiving section includes a multi-quantum well light absorbing layer having a
It has a pin photodiode structure sandwiched between a p-type semiconductor layer and an n-type semiconductor layer. When the reverse bias voltage applied to the multiple quantum well layer via the p-type semiconductor layer and the n-type semiconductor layer is changed, the quantum Confinement Stark effect (QCSE)
2. The surface optical multifunctional device according to claim 1, wherein the absorption coefficient for the signal light is changed by the change in the wavelength.