CN113608371B

CN113608371B - Infrared electric absorption modulator based on II-type broken band energy gap quantum well

Info

Publication number: CN113608371B
Application number: CN202110790767.9A
Authority: CN
Inventors: 李俊; 陈盟
Original assignee: Xiamen University
Current assignee: Xiamen University
Priority date: 2021-07-13
Filing date: 2021-07-13
Publication date: 2024-03-19
Anticipated expiration: 2041-07-13
Also published as: CN113608371A

Abstract

An infrared electro-absorption modulator based on a II-type broken band energy gap quantum well relates to the field of semiconductor photoelectrons. Comprises (i) at least one absorption modulation region, wherein the absorption modulation region comprises a single-period or multi-period II-type broken band energy gap quantum well structure; (ii) Means for providing a modulation bias to the class II bandgap quantum well structure; the II-type broken band energy gap quantum well structure of one periodic unit consists of a first potential barrier, an electron potential well, a hole potential well and a second potential barrier, wherein the electron potential well and the hole potential well are arranged between the first potential barrier and the second potential barrier and do not depend on relative stacking order, and the energy of the band edge of a bulk material conduction band of the electron potential well is lower than that of the band edge of a bulk material valence band of the hole potential well. The waveguide coupling configuration or the normal incidence configuration can be adopted, a larger extinction ratio can be obtained with a smaller bias swing, and the modulation efficiency is high. The mid-infrared light polarized in the transverse magnetic mode and the far-infrared light polarized in the transverse electric mode can be modulated simultaneously. The device has smaller coverage and is suitable for the integration of semiconductor chips.

Description

Infrared electric absorption modulator based on II-type broken band energy gap quantum well

Technical Field

The invention relates to the technical field of semiconductor photoelectrons, in particular to an infrared absorption modulator which works in a mid-infrared or far-infrared band, can regulate and control energy band reverse bias and has high performance and is based on a II-type broken band energy gap quantum well.

Background

An electroabsorption modulator is an optoelectronic device that is independent of the light source and is capable of modulating the intensity of transmitted light. Compared with direct modulation of light intensity by driving current of a light source, external modulation based on an electroabsorption modulator has advantages of high speed, large extinction ratio, low chirp and the like, so that the electroabsorption modulator has become one of core components of modern high-speed optical communication systems. The current widely used electroabsorption modulator is mainly based on quantum confinement stark effect of I-type semiconductor quantum well structure (see patent US7142342B 2), and has the advantages of small driving voltage, high modulation rate, easiness in monolithic integration with semiconductor lasers and the like. Due to the need for low loss fiber optic transmission, conventional fiber optic communications electro-absorption modulators are often designed to operate in several near infrared bands of 0.85 μm, 1.31 μm, and 1.55 μm.

The mid-infrared band (2.5-25 μm) is an important band of the electromagnetic spectrum, which can be used for detecting specific molecules and has wide application in the fields of sensing, environmental monitoring, biomedicine, thermal imaging and the like. In addition, mid-infrared materials are also of great value in modern military defense, photoelectric countermeasure, free space optical communication and other technologies. In recent years, with the continuous progress and maturity of mid-infrared quantum cascade lasers and interband cascade lasers, a great deal of mid-infrared electronic technology has been rapidly developed. Among them, the great potential of mid-infrared Free-space optical communication (Free-space optical communications) [ see literature Alexandre Delga, luc Levidier, "Free-space optical communications with quantum cascade lasers," Proc. SPIE 10926,Quantum Sensing and Nano Electronics and Photonics XVI,1092617 (2019) ] is also gradually recognized and appreciated by people: the medium infrared free space optical communication uses air as a transmission medium, and the signal wavelength is selected in the ranges of 3-5 mu m and 8-14 mu m of a low-absorption atmospheric window, so that an optical fiber is not required to be used as a medium, and the medium infrared free space optical communication has the advantages of quick installation, low cost and 'human eye safety'; compared with the near infrared light used as a carrier wave, the medium infrared free space optical communication is less influenced by smoke, raindrops, dust, air turbulence and the like, so that the transmission distance in the air is longer, and the tolerance to complex weather conditions is higher; compared with wireless radio frequency communication, the bandwidth of the mid-infrared free space optical communication is wider, the ideal target communication bandwidth can reach 40-50 GHz, and the mid-infrared free space optical communication has the characteristic of point-to-point signal transmission, so that data are difficult to intercept, and the mid-infrared free space optical communication has the advantages of electromagnetic interference resistance, high safety, low energy consumption, small volume and the like. Therefore, the mid-infrared free space optical communication has comprehensive optimal advantages in four dimensions of bandwidth capacity, transmission distance, equipment cost and availability, and is expected to become a new generation communication technology with wide application prospect.

Currently, researchers have successfully implemented Mid-infrared free-space optical communication links with data transmission rates between 70Mb/s and 3Gb/s in the laboratory, but the communication links implemented are still based on direct modulation of Mid-infrared lasers, with a maximum bandwidth of only 330MHz[Jony J.Liu,et al., "Mid and long-wave infrared free-space optical communication," Proc.SPIE 11133,Laser Communication and Propagation through the Atmosphere and Oceans VIII,1113302 (2019) ]. Clearly, there is a tremendous boost in this from the ideal target bandwidth of 40-50 GHz for mid-infrared free-space optical communications. Although direct modulation is the simplest way of optical communication coding, the modulation bandwidth is limited by relaxation of working current of a laser, and only lower-speed signal transmission can be realized. Just as semiconductor electroabsorption modulators based on external modulation are necessary devices for high-speed optical fiber communication, electroabsorption modulators which have high performance, can be integrated and operate in the mid-infrared band are also important devices which are indispensable for realizing high-speed mid-infrared free space optical communication. However, since conventional electroabsorption modulators are typically fabricated using group III-V group I semiconductor quantum wells (patent US7142342B2 and EP0809129 A2), most of the group III-V semiconductor materials have energy gaps in the near infrared or visible range, and thus they cannot be used for modulation of mid-far infrared light. On the other hand, in addition to the small amount of research on mid-infrared modulators based on quantum well subband transitions in the 90 s of the last century, only a part of mid-infrared modulators based on graphene-metal plasmas, lithium niobate waveguides, or the like have been reported in recent years, but they have not been practically used for reasons of difficulty in preparation, incompatibility with lasers, and the like. It can be seen that mid-infrared modulators that can be practically used in free-space optical communications are relatively lacking, and in particular, there is a need to develop high-performance mid-infrared absorption modulators that are compatible with quantum cascade lasers or interband cascade lasers.

For more than ten years, alSb/InAs/GaSb/AlSb quantum wells have attracted continued attention from researchers as a type II broken band gap quantum well (type-II brooken-gap quantum wells) structure. The unique property of the quantum well is that the conduction band of InAs is lower than the valence band of GaSb, forming a class II broken band energy gap band alignment (type-II brooken-gapband alignment); under the limitation of the AlSb barrier layer, electrons and holes in the quantum well are respectively limited in the InAs layer and the GaSb layer, so that a two-dimensional electron gas and a two-dimensional hole gas which are spatially separated are formed. When the thickness of the InAs or GaSb layer is greater than a certain critical value, the quantum well has a reversed band gap phase, and opens a micro-energy gap caused by electron-hole hybridization at the finite wave vector, when the system is in a two-dimensional topological insulator phase, exhibiting quantum spin hall effect [ imaging Liuet al, "Quantum Spin Hall Effect in Inverted Type-II Semiconductors," Phys.rev.lett.100,236601 (2008); andKnez,I.,Du,R.&Sullivan,G.,"Evidence for Helical Edge Modes in Inverted InAs/GaSb Quantum Wells,"Phys.Rev.Lett.107,136603(2011)]. In addition, researchers have found that electric fields can be used to regulate AlSb/InAs/GaSb/AlSb quantum wells in both normal and reverse bandgap phase-to-phase transitions [ Qu, F.et al electric and Magnetic Tuning Between the Trivial and Topological Phases in InAs/GaSb Double Quantum Wells. Phys. Rev. Lett.115,036803 (2015) ]At the same time, there are several interesting quantum phenomena in the quantum well, such as spiral Luttinger liquid, exciton insulator and anomalous magnetic transport oscillations, etc. On the other hand, the materials composing the II-type broken band energy gap quantum well belong toAntimonide semiconductor family is an important mid-infrared material, and the material system has been successfully used for preparing mid-infrared photoelectric detector, quantum cascade laser, inter-band cascade laser and other mid-infrared devices. Therefore, if the physical properties of the II-type broken band gap quantum well which are rich in structure and adjustable can be utilized, the novel high-performance mid-infrared photoelectric device is hopefully realized.

Disclosure of Invention

Aiming at the problems that the existing electric absorption modulator for medium infrared free space optical communication is relatively lack, the invention provides the infrared electric absorption modulator based on the II-type broken band energy gap quantum well, which can work in the medium infrared or far infrared wave band at the same time and has the advantages of high extinction ratio, low driving voltage, low power consumption, high modulation efficiency, small volume, compatibility with antimonide-based quantum cascade lasers and interband cascade lasers and the like.

Another object of the present invention is to provide a method of electro-optical modulation of selected light that is based on the principle of bias-controlled energy band inversion with high efficiency.

The infrared electro-absorption modulator based on the class II broken band energy gap quantum well comprises: (i) At least one absorption modulation region comprising a single-period or multicycle class II broken band energy gap quantum well structure; (ii) Means for providing a modulating bias voltage to the class II bandgap quantum well structure for generating an electric field perpendicular to a plane in which the class II bandgap quantum well structure material layer is located;

the II-type broken band energy gap quantum well structure of one periodic unit consists of a first potential barrier, an electron potential well, a hole potential well and a second potential barrier, wherein the electron potential well and the hole potential well are arranged between the first potential barrier and the second potential barrier and do not depend on relative stacking order;

the electron potential well is adjacent to the hole potential well, and the body material of the electron potential well has a conduction band edge E _c Is lower than the bulk material valence band edge E of the hole potential well _v Form a class II broken band gap heterojunction;

the first potential barrier and the second potential barrier form quantum restriction on electron state wave functions and hole state wave functions in an electron potential well and a hole potential well, an electron state wave function body at the bottom of a lowest sub-band of a conduction band is restricted in the electron potential well, and a hole state wave function body at the top of the highest sub-band of the valence band is restricted in the hole potential well;

When an on-state bias voltage is applied to two ends of the II-type broken band energy gap quantum well structure, the quantum well is in a normal band gap phase, and the bottom of the lowest conduction band sub-band of the electron potential well is higher than the top of the highest valence band sub-band of the hole potential well in energy;

when an off-state bias is applied across the class II broken bandgap quantum well structure, the quantum well is in the inverted bandgap phase, and the bottom of the lowest conduction band sub-band of the electron potential well is energetically lower than the top of the highest valence band sub-band of the hole potential well.

The material of the electron potential well of the II-type broken band energy gap quantum well structure can be at least one selected from InAs, inAsSb, inGaAs, inGaAsSb and the like; the material of the hole potential well can be at least one selected from GaSb, gaInSb, gaAlSb, gaAsSb, gaAlAsSb, gaInAsSb, gaAlInSb, gaAlInAsSb and the like; the material of the first barrier and the second barrier may be at least one selected from AlSb, alGaSb, alGaAsSb, alInSb, alGaInSb, alInAsSb, alGaInAsSb and the like.

The infrared electro-absorption modulator based on the class II broken band energy gap quantum well can adopt a waveguide coupling configuration or a normal incidence configuration.

The waveguide coupling configuration has a waveguide structure comprising at least: a base layer; a first cladding layer, a waveguide core layer and a second cladding layer are sequentially arranged on the upper side of the basal layer; a first contact electrode is arranged on the lower side of the basal layer or the upper side of the table top exposed by etching of the first coating layer; a second contact electrode is arranged on the upper side of the second cladding layer; the waveguide core layer comprises at least one absorption modulation area; the first coating layer and the second coating layer are respectively heavily doped with semiconductor materials or have a multilayer structure; the first contact electrode and the second contact electrode respectively apply bias voltages to the absorption modulation region through the first cladding layer and the second cladding layer, so that the device for providing modulation bias voltages for the II-type broken band gap quantum well structure is formed.

Preferably, the waveguide core layer may adopt a separate confinement structure, and further includes a first separate confinement layer and a second separate confinement layer; the first and second limiting layers are doped semiconductor materials or multilayer structures, are adjacent to the lower and upper interfaces of the absorption modulation region, and have optical refractive indexes greater than those of the first and second cladding layers.

Preferably, the base layer further comprises a substrate and a buffer layer having a thickness of not less than 200nm for releasing strain, isolating dislocation and impurities to reduce the influence of the substrate on the device.

Preferably, a first transition layer and a second transition layer are respectively arranged at the lower interface and the upper interface of the first cladding layer, a third transition layer and a fourth transition layer are respectively arranged at the lower interface and the upper interface of the second cladding layer, and the transition layers are used for reducing parasitic voltage drop caused by abrupt change of interfaces of adjacent area layers; the doping concentration of the transition layer is respectively between the doping concentrations of the adjacent materials at two sides of the transition layer.

The normal incidence configuration is that light is incident perpendicular to a plane of the material layer of the absorption modulation region, and at least comprises: a bottom cladding layer, an absorption modulation region, a top cladding layer, a bottom electrode and a top electrode;

The bottom coating layer and the top coating layer are doped with semiconductor materials or have a multilayer structure; the absorption modulation area is arranged between the bottom cladding layer and the top cladding layer; the bottom electrode is a transparent electrode or a grating electrode or is provided with a light-transmitting window, and is arranged on the upper side of the etched exposed table top of the bottom cladding layer and forms electrical contact; the top electrode is a transparent electrode or a grating electrode or is provided with a light-transmitting window, and is arranged on the upper side of the top coating layer and forms electrical contact; the bottom electrode and the top electrode respectively apply bias voltages to the absorption modulation region through the bottom cladding layer and the top cladding layer to form a device for providing modulation bias voltages for the II-type broken band energy gap quantum well structure.

Preferably, the bottom high reflection film is arranged on the lower side of the bottom coating layer, or the top high reflection film is arranged in the light-transmitting window area of the top electrode on the upper side of the top coating layer, or the bottom high reflection film and the top high reflection film are arranged at the same time; the bottom high reflection film and the top high reflection film are respectively formed by a distributed Bragg reflector (distributed Bragg reflector) formed by alternately stacking a plurality of dielectric layers or metal films, so that a Fabry-Perot cavity structure with symmetry or asymmetry is formed.

Preferably, a metal bar grating can be arranged on the upper side or the lower side of at least one layer of the bottom high reflection film, the top high reflection film, the bottom coating layer or the top coating layer, and the metal bar grating is used for increasing the coupling between the vertical electric field component of the incident light and the absorption modulation area, and the grating period is smaller than or equal to the selected working wavelength of the infrared electric absorption modulator.

The electro-optic modulation method for the selected light comprises the following steps:

1) Placing an electroabsorption modulator or electro-optic modulator in the propagation path of the selected light, wherein the modulation region of the electroabsorption modulator or electro-optic modulator comprises a semiconductor single-layer or multi-layer structure having the following characteristics:

a. the energy band structure of the semiconductor single-layer or multi-layer structure is provided with a conduction band and a valence band, and an electron state at the bottom of the conduction band and a hole state at the top of the valence band respectively belong to eigenstates with different Hamiltonian volume properties of the system, so that the conduction band and the valence band can be distinguished by the properties of the electron state at the bottom of the conduction band and the hole state at the top of the valence band;

b. the semiconductor single-layer or multi-layer structure has a normal band gap phase, and the energy of the conduction band bottom is higher than that of the valence band top;

c. the semiconductor single-layer or multi-layer structure has a reversed band gap phase, and the energy of the conduction band bottom is lower than that of the valence band top;

d. converting the semiconductor monolayer or multilayer structure from a normal band gap phase to a reversed band gap phase by varying a bias voltage applied to the semiconductor monolayer or multilayer structure;

e. the semiconductor single-layer or multi-layer structure has significantly different absorption or refractive index for selected light in the normal band gap phase and the reversed band gap phase;

2) By biasing the modulation region of the electro-absorption modulator or electro-optical modulator such that the semiconductor material or multilayer structure of step 1) is in the normal bandgap phase;

3) Changing the bias voltage of step 2) such that the semiconductor monolayer or multilayer structure of step 1) is in a reversed bandgap phase;

4) Repeating the steps 2) and 3), reducing the difference value of the bias voltages required in the step 2) and the step 3), and finding out the critical bias voltage for converting the normal band gap phase into the reverse band gap phase;

5) Setting the on-state bias near the critical bias found in step 4), slightly deviating from the critical bias and leaving the semiconductor single-layer or multi-layer structure exactly in the normal bandgap phase;

6) Setting the on-state bias voltage in the step 5), and changing the bias voltage applied to the semiconductor single-layer or multi-layer structure to enable the semiconductor single-layer or multi-layer structure to generate the transition from the normal band gap phase to the reverse band gap phase so as to achieve the off-state; the transition of the normal bandgap phase to the inverted bandgap phase results in a significant change in the absorption or refractive index of the semiconductor monolayer or multilayer structure; thereby achieving a relatively significant modulation of the intensity or phase of the selected light with a relatively small bias swing.

From the technical scheme, the invention has the following beneficial effects:

1. The on-state bias voltage and the off-state bias voltage can be arranged near the critical voltage of the class II broken band energy gap quantum well, so that the difference value between the on-state bias voltage and the off-state bias voltage is smaller, and a larger extinction ratio can be obtained with a smaller bias swing, and the modulation efficiency is higher. Theoretical calculation shows that for the optimized infrared electro-absorption modulator based on the II-type broken band energy gap quantum well, the low-temperature modulation efficiency can be several times of the modulation efficiency of a conventional optical fiber communication near-infrared electro-absorption modulator, and the infrared electro-absorption modulator has the advantages of high extinction ratio, low driving voltage, low dynamic power consumption, high modulation bandwidth-driving voltage ratio and the like. And at normal temperature, the performance indexes of the electroabsorption modulator are equivalent to those of the conventional optical fiber communication electroabsorption modulator.

2. The infrared absorption modulator of the invention is based on energy band reversal bias regulation and control of conduction band intersubband transition and valence band intersubband transition, so that mid-infrared light polarized by transverse magnetic mode (TM) and far-infrared light polarized by transverse electric mode (TE) can be modulated simultaneously.

3. Typical modulation region sizes for the infrared absorption modulator of the present invention are: the length is 20-200 mu m, and the width is 5-15 mu m, so the device coverage is smaller, and the device is suitable for semiconductor chip integration.

4. The infrared absorption modulator material of the invention belongs toThe antimonide semiconductor family is compatible with antimonide-based infrared quantum cascade lasers and interband cascades, so that the integration of the antimonide-based infrared quantum cascade lasers with the antimonide-based infrared quantum cascade lasers without process barriers is easy to realize.

Drawings

FIG. 1 is a schematic diagram of the band profile and wave function distribution of a class II broken band gap quantum well of a periodic cell in real space when different biases are applied. Wherein (a) is the application of bias voltage V _on When the II-type broken band energy gap quantum well is in a normal band gap phase; (b) To apply bias V _off When the II-type broken band gap quantum well is in a reversed band gap phase.

FIG. 2 is a schematic diagram of a preferred class II bandgap quantum well with momentum space band dispersion curves. Wherein, (a) is that the quantum well is in a normal band gap phase and (b) is that the quantum well is in an abnormal band gap phase.

FIG. 3 is a schematic diagram of an embodiment of an infrared absorption modulator of the present invention employing a waveguide coupling configuration;

FIG. 4 is a schematic diagram of an infrared absorption modulator according to an embodiment of the present invention in a normal incidence configuration and a vertical section thereof;

FIG. 5 is a graph showing the transverse magnetic mode (TM) light absorption coefficient spectra of AlSb/InAs/GaSb/AlSbII type bandgap quantum wells at different bias voltages for a periodic cell in accordance with a preferred embodiment of the present invention;

FIG. 6 is a graph of transverse electric mode (TE) light absorption coefficient spectra of AlSb/InAs/GaSb/AlSbII type bandgap broken quantum wells at different bias for a periodic cell in accordance with a preferred embodiment of the present invention;

FIG. 7 is a graph showing the extinction ratio of infrared light in different wavelength transverse magnetic mode (TM) polarizations as a function of driving voltage in accordance with a preferred embodiment of the invention.

FIG. 8 is a graph showing the variation of extinction ratio with driving voltage for different wavelength transverse electric mode (TE) polarized far infrared light according to a preferred embodiment of the present invention.

In the figures, each label is:

100-an absorption modulation region, 101-a first potential barrier, 102-an electron potential well, 103-a hole potential well, 104-a second potential barrier; e (E) _c -body material conduction band edge, E _v Valence band edge of bulk material, E _F Fermi level, E1 (Γ) -conduction band lowest subband E1 with bottom, E2 (Γ) -conduction band second subband E2 with bottom, HH1 (Γ) -valence band highest subband HH1 with top, HH2 (Γ) -valence band second subband HH2 with top,-electronic state wave function of band bottom of subband E1 +.>-cavitation wave function of the band roof of subband HH1, V _on -on-state bias, V _off -off-state bias;

e1-lowest conduction band sub-band, E2-second conduction band sub-band, HH 1-highest valence band sub-band, HH 2-second valence band sub-band;

300-substrate layer, 310-first cladding layer, 320-waveguide core layer, 330-second cladding layer, 340-first contact electrode, 350-second contact electrode, 321-first respective confinement layer, 322-second respective confinement layer, 301-substrate, 302-buffer layer, 311-first transition layer, 312-second transition layer, 331-third transition layer, 332-fourth transition layer;

410-bottom cladding layer, 420-top cladding layer, 430-bottom electrode, 440-top electrode, 450-bottom highly reflective film, 460-top highly reflective film, 470-metal stripe grating.

Detailed Description

For the purpose of making the objects, technical solutions and advantages of the embodiments of the present invention more apparent, the present invention will be further described in detail below with reference to the accompanying drawings. It should be understood that in the drawings, the thicknesses of layers and regions are exaggerated for clarity of illustration and should not be considered as a strict reaction geometry and the proportional relationship between layers; the described embodiments are intended to be only a few, but not all, of the various embodiments of the present invention, as those of ordinary skill in the art will readily appreciate from the disclosure of the present invention.

In the description of the present invention, it should be noted that the directions or positional relationships indicated by the terms "upper", "lower", "front", "rear", "left", "right", "inner", "outer", "bottom", "top", etc. are based on the directions or positional relationships shown in the drawings, are merely for convenience of describing the present invention and simplifying the description, and do not indicate or imply that the case or element to be referred to must have a specific direction, be configured and operated in a specific direction, and thus should not be construed as limiting the present invention. Furthermore, the terms "first," "second," and the like, are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.

The infrared electro-absorption modulator based on the class II broken band energy gap quantum well comprises: (i) At least one absorption modulation region 100, the absorption modulation region 100 comprising a single-period or multi-period class II broken band gap quantum well structure; (ii) And the device is used for providing modulation bias voltage for the II-type broken band energy gap quantum well structure and generating an electric field perpendicular to the plane of the II-type broken band energy gap quantum well structure material layer.

As shown in fig. 1, the class II broken band gap quantum well structure of one period unit is composed of a first potential barrier 101, an electron potential well 102, a hole potential well 103 and a second potential barrier 104, wherein the electron potential well 102 and the hole potential well 103 are placed between the first potential barrier 101 and the second potential barrier 104 and do not depend on the relative stacking order;

the electron potential well 102 is adjacent to the hole potential well 103, and the bulk material conduction band edge E of the electron potential well 102 _c Is lower than the bulk material valence band edge E of hole potential well 103 _v Thereby forming a class II broken bandgap heterojunction;

the first and second barriers 101 and 104 form quantum confinement for the electron and hole state wave functions in the electron and hole potential wells 102 and 103, with the electron state wave function of the conduction band lowest sub-band E1 at the bottomMainly confined in electron potential well 102, the hole state wave function of the highest subband HH1 band top of the valence band +. >Mainly confined in the hole potential well 103;

when a specific bias voltage V is applied to two ends of the II-type broken band energy gap quantum well structure _on When the quantum well is in the normal band gap phase, the bottom E1 (Γ) of the lowest conduction band sub-band E1 of the electron potential well 102 is energetically higher than the top HH1 (Γ) of the highest valence band sub-band HH1 of the hole potential well 103 [ see (a) diagram in FIG. 1 ]]The momentum space band dispersion curve of the normal band gap phase is shown in fig. 2 (a);

when a specific bias voltage V is applied to two ends of the II-type broken band energy gap quantum well structure _off (V _off ≠V _on ) When the quantum well may be in a reversed bandgap phase, characterized by the bottom E1 (Γ) of the lowest conduction band sub-band E1 of the electron potential well 102 being energetically lower than the top HH1 (Γ) of the highest valence band sub-band HH1 of the hole potential well 103 [ see (b) diagram in fig. 1 ]]The momentum space band dispersion curve of the reversed bandgap phase is shown in fig. 2 (b).

As a typical example of the type II broken band gap quantum well structure, an AlSb/InAs/GaSb/AlSb quantum well is generally used as a preferred. It should be appreciated that the first barrier 101, the electron potential well 102, the hole potential well 103, and the second barrier 104 of the class II bandgap quantum well structure may be replaced with materials of similar characteristics, and thus only the characteristics a) through e) described above need be satisfied, and should also be considered as belonging to the class II bandgap quantum well structure.

Further, the material of the electron potential well 102 of the class II broken band gap quantum well structure is selected from InAs, inAsSb, inGaAs, inGaAsSb as one or more mixtures; the material of the hole potential well 103 is selected from GaSb, gaInSb, gaAlSb, gaAsSb, gaAlAsSb, gaInAsSb, gaAlInSb, gaAlInAsSb as a mixture of one or more; the materials of the first potential barrier 101 and the second potential barrier 104 are respectively selected from AlSb, alGaSb, alGaAsSb, alInSb, alGaInSb, alInAsSb, alGaInAsSb by one or more mixing; the first potential barrier 101, the electron potential well 102, the hole potential well 103 and the second potential barrier 104 are selected to satisfy the characteristics a) to e) of the above-described class II broken band gap quantum well structure.

According to the characteristics of the infrared electro-optical absorption modulator based on the II-type broken band energy gap quantum well structure, the invention also provides a high-efficiency electro-optical modulation method based on the bias voltage regulation energy band inversion principle for selected light, which comprises the following steps:

1) Placing an electroabsorption modulator or electro-optic modulator in the propagation path of said selected light, wherein the modulation region of said electroabsorption modulator or electro-optic modulator comprises a semiconductor single-layer or multi-layer structure having the following characteristics:

a. The semiconductor material or the energy band structure of the multilayer structure is provided with a conduction band and a valence band, the electronic state at the bottom of the conduction band and the electronic state at the top of the valence band respectively belong to the eigen states with different Hamiltonian volume properties of the system, and the conduction band and the valence band can be distinguished by the properties of the electronic state at the bottom of the conduction band and the electronic state at the top of the valence band; taking the class II broken band energy gap quantum well structure shown in FIG. 1 as an example, the quantum well structure has a conduction band lowest sub-band E1 and a valence band highest sub-band HH1, and the electron state wave function of the bottom of the sub-band E1And the cavitation wave function of the band top of the subband HH1 +.>Is mainly distributed in an electron potential well (102) and a hole potential well (103), and can distinguish a conduction band lowest sub-band E1 and a valence band highest sub-band HH1 by the distribution characteristics;

b. the semiconductor material or the multilayer structure has a normal band gap phase and is characterized in that the energy of the bottom of a conduction band is higher than the energy of the top of a valence band; for example, in the class II broken band energy gap quantum well structure embodiment shown in fig. 1 (a), the energy of the conduction band lowest sub-band E1 band bottom E1 (Γ) is higher than the energy of the valence band highest sub-band HH1 band top HH1 (Γ), which is in the normal band gap phase.

c. The semiconductor material or the multilayer structure has a reversed band gap phase, and is characterized in that the energy of the bottom of a conduction band is lower than that of the top of a valence band; for example, in the class II broken band gap quantum well structure embodiment shown in fig. 1 (b), the energy of the conduction band lowest sub-band E1 with bottom E1 (Γ) is lower than the energy of the valence band highest sub-band HH1 with top HH1 (Γ), which is in the inverted band gap phase;

d. The normal bandgap phase may be converted to the reversed bandgap phase by varying the bias voltage applied to the semiconductor material or multilayer structure; for example, using the type II broken band gap quantum well structure of one period unit shown in FIG. 1 as an example, the bias voltage is applied by V _on Becomes V _off When the quantum well will undergo a transition from the normal bandgap phase to the inverted bandgap phase;

e. the semiconductor material or multilayer structure has substantially different absorption or refractive index for the selected light at the normal band gap phase and the reversed band gap phase; for example, consider the class II bandgap quantum well structure shown in fig. 1 as an example: in the normal bandgap phase shown in FIG. 1 (a), due to the Fermi level E _F The band top HH1 (Γ) of HH1 is higher than the highest subband of the valence band and is lower than the bottom E1 (Γ) of the lowest subband E1 of the conduction band, neither the lowest subband E1 of the conduction band nor the highest subband HH1 of the valence band is filled, the intersubband transition is forbidden, and the light absorption is weakerThe method comprises the steps of carrying out a first treatment on the surface of the In the case of the reversed bandgap phase shown in diagram (b) of FIG. 1, due to the Fermi level E _F The band top HH1 (Γ) above the conduction band lowest subband E1 and below the valence band highest subband HH1, the conduction band lowest subband E1 and valence band highest subband HH1 distributions are filled with electrons and holes, the conduction band inter-subband transitions E1-E2 and the valence band inter-subband transitions HH1-HH2 are both allowed, resulting in a significant increase in the absorption of light conforming to the corresponding transition rules;

2) Causing the semiconductor material or multilayer structure in step 1) to be in the normal band gap phase by biasing the modulation region of the electro-absorption modulator or electro-optic modulator;

3) Changing the bias voltage of step 2) such that the semiconductor material or multilayer structure of step 1) is in the reversed bandgap phase;

4) Repeating steps 2) and 3), reducing the difference between the biases required to meet steps 2) and 3), and finding the critical bias voltage at which the transition from the normal band gap phase to the reversed band gap phase occurs;

5) Setting the on-state bias near the critical bias found in step 4), slightly deviating from the critical bias and leaving the semiconductor material or multilayer structure exactly in the normal bandgap phase;

6) After setting the on-state bias voltage in step 5), the normal bandgap phase is converted into the reversed bandgap phase by only slightly changing the bias voltage applied to the semiconductor material or the multilayer structure, so as to reach an off-state; also according to e of step 1), the transition from the normal bandgap phase to the inverted bandgap phase is accompanied by a significant change in the absorption or refractive index of the semiconductor material or multilayer structure; thus, the above steps may enable a more pronounced modulation of the intensity or phase of the selected light with a relatively small bias swing.

Obviously, the electro-optic modulation method is applicable to the infrared electro-absorption modulator based on the II-type broken band energy gap quantum well structure. It should be noted, however, that the above-described electro-optic modulation method is not limited to the infrared electro-optic absorption modulator of the present invention, and that any electro-optic modulator or electro-optic modulator having the characteristics of a) to e) described in step 1), such as an electro-optic modulator or electro-optic modulator comprising a topology insulator having a bias voltage regulating topology energy band inversion property, may be used to perform high-efficiency electro-optic modulation.

Specific examples are given below, but the present invention is not limited to the configurations of the following examples.

Example 1

With the waveguide coupling configuration shown in fig. 3, having a waveguide structure, at least comprising: a base layer 300; a first cladding layer 310, a waveguide core layer 320, and a second cladding layer 330 are sequentially provided on the upper side of the base layer 300; a first contact electrode 340 is disposed on the lower side of the base layer 300 or the upper side of the etched and exposed mesa of the first cladding layer 310 and is in electrical contact with the formation of an electrical contact; a second contact electrode 350 is provided on the upper side of the second cladding layer 330 and forms an electrical contact; wherein the waveguide core layer 320 comprises at least one absorption modulation region 100; the first cladding layer 310 and the second cladding layer 330 respectively adopt a heavily doped semiconductor material or a multi-layer structure; the first contact electrode 340 and the second contact electrode 350 apply a bias voltage to the absorption modulation region 100 through the first cladding layer 310 and the second cladding layer 330, respectively, to constitute the means for providing a modulation bias voltage to the class II bandgap quantum well structure.

The waveguide core layer 320 adopts a separate confinement structure, and further includes a first separate confinement layer 321 and a second separate confinement layer 322; the first confinement layer 321 and the second confinement layer 322 are doped semiconductor materials or a multi-layer structure, and are adjacent to the lower interface and the upper interface of the absorption modulation region 100, respectively, and are characterized by an optical refractive index greater than that of the first cladding layer 310 and the second cladding layer 330.

The base layer 300 further comprises a substrate 301 and a buffer layer 302, wherein: buffer layer 302 is not less than 200nm thick and serves to release strain, isolate dislocations and impurities to reduce the impact of substrate 301 on the device.

In order to reduce parasitic voltage drop caused by abrupt change of interfaces of adjacent regional layers, a first transition layer 311 and a second transition layer 312 may be respectively disposed at a lower interface and an upper interface in the first cladding layer 310, and a third transition layer 331 and a fourth transition layer 332 may be respectively disposed at a lower interface and an upper interface of the second cladding layer 330, where the transition layers are characterized in that their impurity concentration is respectively between the impurity concentration of the adjacent materials on two sides thereof.

The substrate 301 is specifically an n-type GaSb substrate;

the buffer layer 302 is made of n-type GaSb material, and doped with impurities at a concentration of 1×10 ¹⁷ cm ^-3 ～2×10 ¹⁸ cm ^-3 The section is 0.2-1.5 μm thick;

The first cladding layer 310 is made of heavily doped n-type InAs/AlSb short-period superlattice or AlGaAsSb alloy material, the refractive index of the material is between 3.20 and 3.40, and the doping concentration is 0.1X10 ¹⁹ cm ^-3 ～1.5×10 ¹⁹ cm ^-3 The section is 1-5 μm thick;

the first confinement layers 321 are made of n-type GaSb material, and have refractive index of 3.70-3.90 and doping concentration of 0.5X10 ¹⁷ cm ^-3 ～2×10 ¹⁷ cm ^-3 The thickness of the section is between 0.5 and 2 mu m;

the absorption modulation region 100 adopts a class II broken band energy gap quantum well with the period of 1-15, wherein: the first potential barrier 101 and the second potential barrier 104 are made of AlSb or AlGaSb materials, and the thickness is between 5 and 50 nm; the electron barrier 102 is made of InAs material, and the thickness is between 3 and 20 nm; the hole potential barrier 103 is made of GaSb material, and the thickness is in the range of 3-20 nm;

the second confinement layer 322 is made of n-type GaSb material, and has refractive index of 3.70-3.90 and doping concentration of 0.5X10 ¹⁷ cm ^-3 ～2×10 ¹⁷ cm ^-3 The thickness of the section is between 0.5 and 2 mu m;

the second cladding layer 330 is made of heavily doped n-type InAs/AlSb short-period superlattice or AlGaAsSb alloy material, and has refractive index of 3.20-3.40 and doping concentration of 0.1X10% ¹⁹ cm ^-3 ～1.5×10 ¹⁹ cm ^-3 The section is 0.5-3 mu m thick;

a first contact electrode 340 formed on the lower side of the substrate 301 and made of a metal material such as Ti, pt, au, ag, cu or an alloy thereof;

A second contact electrode 350 formed on the first cladding layer 310 and including a cap layer and a metal electrode disposed thereon, wherein the cap layer is heavily doped with n-type InAs/AlSb short-period superlattice or heavily doped n-type InAs material with doping concentration of more than 1.0X10 ¹⁹ cm ^-3 The thickness is in the interval of 0.1-0.5 mu m; the metal electrode adopts Ti, pt, au, ag, cu and other metal materials or alloys thereof;

as a further preference, the first transition layer 311 and the second transition layer 312 may be inserted at the lower interface and the upper interface of the first cladding layer 310, respectively, and the third transition layer 331 and the fourth transition layer 332 may be inserted at the lower interface and the upper interface of the second cladding layer 330, respectively; the first transition layer 311, the second transition layer 312, the third transition layer 331 and the fourth transition layer 332 may be n-type doped InAs/AlSb short period superlattice, which has a doping concentration between the doping concentrations of the adjacent two-sided materials, and a typical value is 1×10 ¹⁷ cm ^-3 ～5×10 ¹⁸ cm ^-3 A section;

the ridge waveguide structure shown in fig. 1 can be provided by standard photolithography, in which the waveguide width w is 3-15 μm, the modulation length is determined by the length L of the first contact electrode 340, and the typical value L is 20-200 μm.

By simultaneous self-consistent calculation of an eight-band k.p effective mass model and a poisson equation, fig. 5 and 6 respectively show the light absorption coefficient spectrums of a transverse magnetic mode (TM) and a transverse electric mode (TE) of AlSb/InAs/GaSb/AlSbII type broken band energy gap quantum wells of one period unit under different bias voltages. It can be seen that as the magnitude of the reverse bias voltage (V < 0) increases to the point that the class II bandgap quantum well undergoes bandgap inversion, the light absorption coefficient spectrum of the transverse magnetic mode (TM) exhibits a narrow and strong absorption peak in the mid-infrared band, which corresponds to the intersubband transition of E1-E2, see FIG. 5; at the same time, a broad transverse electric mode (TE) absorption peak occurs in the far infrared band of the light absorption coefficient spectrum, which corresponds to the transitions of HH1-HH2 and HH1 to the other sub-bands, see fig. 6. It can be seen that if the operating wavelength of the infrared absorption modulator is set to the absorption peak region, the light at that wavelength can be effectively modulated by applying a bias voltage.

The preferred embodiment of the infrared electro-optic absorption modulator of FIGS. 5 and 6 can be implemented in accordance with the high efficiency electro-optic modulation method based on the principle of bias voltage modulated energy band inversion of the present inventionOn-state bias voltage V _on Disposed near the critical bias of its class II bandgap quantum well energy band inversion and just so that it is in the normal bandgap phase, e.g. setting V _on -0.30V. At this time, the energy band of the class II broken band gap quantum well can be reversed by slightly changing the bias voltage, for example, by v→0.35V, and the light absorption coefficient spectrum will have a sub-band transition absorption peak at a specific wavelength. If the reverse bias voltage is further increased, the absorption peak will be significantly enhanced. The off-state bias voltage V of the infrared absorption modulator can be adjusted _off At a bias voltage required to achieve the desired extinction ratio for the operating wavelength of light.

For an electroabsorption modulator of waveguide coupling configuration, its extinction ratio ER can be calculated by:

wherein I is _on And I _off The output light intensity of the electric absorption modulator in the on state and the off state is respectively, Γ is the coupling limiting factor of the waveguide, alpha (V) is the variation function of the absorption coefficient of the modulated light along with the bias voltage, and L is the modulation length of the waveguide. For an infrared electro-absorption modulator with single period class II broken band gap quantum well, the waveguide light confinement factor is Γ=Γ ^sp Approximately 0.02, the driving voltage isFor an infrared electro-absorption modulator with N period class II broken band gap quantum wells, the waveguide coupling limiting factor may be approximately Γ ^sp While its driving voltage is approximately +.>The dependence of extinction ratio of the mid-infrared light of transverse magnetic mode (TM) polarization and the far-infrared light of transverse electric mode (TE) polarization of different wavelengths on the driving voltage is shown in fig. 7 and 8, respectively, which has a waveguide coupling configuration with a waveguide modulation length l=100 μm and n=4 periods AlSb/InAs/GaSb/alsbhi type bandgap quantum wells. It can be seen from fig. 7 and 8 that for light of a corresponding wavelength in the vicinity of the sub-band transition absorption peak, for example, mid-infrared Transverse Magnetic (TM) polarized light of 4.46 μm and far-infrared Transverse Electric (TE) polarized light of 22.5 to 62.0 μm, only about 0.3V and 0.65V are required, respectively, to achieve high-efficiency electroabsorption modulation with a extinction ratio of up to 20 dB. In addition, low drive voltages and small device footprint will also provide advantages for this embodiment, such as low dynamic power consumption, high modulation bandwidth, and the like.

Example 2

On the basis of embodiment 1, unlike embodiment 1, an n-type GaAs substrate is used for the substrate 301; the buffer layer 302 is made of n-type AlGaSb material with doping concentration of 1×10 ¹⁷ cm ^-3 ～2×10 ¹⁸ cm ^-3 The thickness of the section is in the range of 0.5-3 μm.

The embodiment 2 has the advantages that the more common GaAs substrate is adopted, the preparation cost is relatively low, the preparation process is mature, and the optical interconnection integration is convenient to realize.

Example 3

On the basis of example 1, unlike example 1, wherein:

the substrate 301 is an n-type InAs substrate;

the buffer layer 302 is made of n-type InAs material, and doped with 1×10 impurity concentration ¹⁷ cm ^-3 ～2×10 ¹⁸ cm ^-3 The section is 0.2-1.5 μm thick;

the first cladding layer 310 has a refractive index of 2.80-3.10, and is made of heavily doped n-type InAs material with a doping concentration of 0.5X10 ¹⁹ cm ^-3 ～2×10 ¹⁹ cm ^-3 The section is 1-4 μm thick;

the first confinement layers 321 have refractive indices designed to be in the range of 3.20-3.60, are made of n-type InAs material, and have impurity concentrations of 0.1X10 ¹⁷ cm ^-3 ～5×10 ¹⁷ cm ^-3 The section is 0.5-3 mu m thick;

the second confinement layers 322 have refractive indices designed to be in the range of 3.20-3.60, are made of n-type InAs material, and have doping concentrations of 0.1X10 ¹⁷ cm ^-3 ～5×10 ¹⁷ cm ^-3 The thickness of the interval is 0.5 to the whole3 μm interval;

the second cladding layer 330, which has a refractive index of 2.80-3.10 and is made of heavily doped n-type InAs material, has a doping concentration of 0.5X10 ¹⁹ cm ^-3 ～2×10 ¹⁹ cm ^-3 The thickness of the section is between 0.5 and 2 mu m;

a second contact electrode 350 heavily doped with a heavily doped n-type InAs material having a doping concentration greater than 1×10 ¹⁹ cm ^-3 The thickness is in the interval of 0.1-0.5 mu m;

example 3 has the advantage of using an InAs substrate, having higher mobility and thermal conductivity, and is easy to implement an ultra-high speed infrared absorption modulator with good heat dissipation.

Example 4

With the normal incidence configuration shown in fig. 4, light is incident perpendicular to the plane of the material layer of the absorption modulation region 100, and comprises at least: a bottom cladding layer 410, an absorption modulation region 100, a top cladding layer 420, a bottom electrode 430, a top electrode 440;

wherein the bottom cladding layer 410 and the top cladding layer 420 are doped with semiconductor materials or have a multi-layer structure; the absorption modulation zone 100 is disposed between a bottom cladding layer 410 and a top cladding layer 420; the bottom electrode 430 is a transparent electrode or a grating electrode or is provided with a light-transmitting window, and is arranged on the upper side of the etched exposed mesa of the bottom cladding layer 410 and forms electrical contact; the top electrode 440 is a transparent electrode or a grating electrode or is provided with a light-transmitting window, and is arranged on the upper side of the top cladding layer 420 and forms electrical contact; the bottom electrode 430 and the top electrode 440 bias the absorption modulation region 100 through the bottom cladding layer 410 and the top cladding layer 420, respectively, to form a means for providing a modulation bias to the class II bandgap quantum well structure.

Has a symmetrical or asymmetrical Fabry-perot cavity (Fabry-perot cavity) structure: a bottom high reflection film 450 is provided on the lower side of the bottom cladding layer 410, or a top high reflection film 460 is provided in the light-transmitting window region of the top electrode 440 on the upper side of the top cladding layer 420, or both the bottom high reflection film 450 and the top high reflection film 460 are provided; the bottom high reflection film 450 and the top high reflection film 460 are respectively composed of a distributed bragg reflector (distributed Bragg reflector) or a metal thin film formed by alternately stacking a plurality of dielectric layers;

to increase the coupling of the vertical electric field component of the incident light to the absorption modulation region 100, a metal bar grating 470 is disposed on the upper or lower side of one or more of the bottom highly reflective film 450, the top highly reflective film 460, the bottom cladding layer 410, and the top cladding layer 420, with a grating period less than or equal to the selected operating wavelength of the infrared absorption modulator of the present invention.

The bottom cladding layer 410 is made of heavily doped n-type InAs material or n-type InAs/AlSb short period superlattice, and the doping concentration is 0.1X10 × 10 ¹⁹ cm ^-3 ～2×10 ¹⁹ cm ^-3 The section is 0.1-1 μm thick;

the absorption modulation region 100 adopts a class II broken band energy gap quantum well with the period of 1-40, wherein: the first potential barrier 101 and the second potential barrier 104 are made of AlSb materials, and the thickness is between 5 and 50 nm; the electron barrier 102 is made of InAs material, and the thickness is between 3 and 20 nm; the hole potential barrier 103 is made of GaSb material, and the thickness is in the range of 3-20 nm;

The top cladding layer 420 is made of heavily doped n-type InAs material or n-type InAs/AlSb short period superlattice, and the doping concentration is 0.1X10% ¹⁹ cm ^-3 ～2×10 ¹⁹ cm ^-3 The section is 0.1-1 μm thick;

a top electrode 440 formed on the top cladding layer 420, made of a metal material such as Ti, pt, au, ag, cu or an alloy thereof, and having a light-transmitting window;

a bottom high reflection film 450 is provided on the lower side of the bottom cladding layer 410; the bottom high reflection film 450 adopts a distributed Bragg reflector formed by alternately stacking 4-30 pairs of GaSb and AlAsSb with the thickness of 1/4 wavelength;

optionally, a top highly reflective film 460 is disposed within the light transmissive window of the top electrode 440 on the upper side of the top cladding layer 420; the top reflection film 460 is made of 4-6 pairs of Ge and Al with a thickness of 1/4 wavelength ₂ O ₃ Distributed Bragg reflectors formed by alternately stacking; a metal bar grating 470 is arranged on the top reflection film 460, and the grating period is in the interval of 0.5-3 mu m;

optionally, for the design that the top reflection film 460 is not used, a metal bar grating 470 with a grating period between 0.5 and 3 μm may be disposed in the light-transmitting window of the top electrode 440 and above the top cladding layer 420;

the structure above the bottom cladding layer 410 may be formed into a mesa as shown in fig. 4 by standard photolithographic processes; a bottom electrode 430 is disposed around the mesa formed over the bottom cladding layer 410 to form the light-transmissive window; the bottom electrode 430 is made of a metal material such as Ti, pt, au, ag, cu or an alloy thereof.

According to the vertical incidence configuration of the present embodiment, light may be vertically incident from top to bottom of the top high reflection film 460 or from bottom to top of the bottom high reflection film 450; the device structure can be prepared on a semiconductor substrate, and can also be directly formed on the emergent surface of a Vertical Cavity Surface Emitting Laser (VCSEL), so that the integration with the VCSEL is realized.

The above-described embodiments are merely preferred embodiments of the present invention and should not be construed as limiting the scope of the present invention. All equivalent changes and modifications within the scope of the present invention are intended to be covered by the present invention.

Claims

1. An infrared electro-absorption modulator based on class II broken bandgap quantum wells, comprising: (i) At least one absorption modulation region comprising a single-period or multicycle class II broken band energy gap quantum well structure; (ii) Means for providing a modulating bias voltage to the class II bandgap quantum well structure for generating an electric field perpendicular to a plane in which the class II bandgap quantum well structure material layer is located;

The electron potential well is adjacent to the hole potential well, and the energy of the band edge of the bulk material conduction band of the electron potential well is lower than that of the band edge of the bulk material valence band of the hole potential well, so that a class II broken band energy gap heterojunction is formed;

when an on-state bias voltage is applied to two ends of the II-type broken band energy gap quantum well structure, the quantum well is in a normal band gap phase, and the energy of the lowest sub-band bottom of a conduction band of the electron potential well is higher than the energy of the highest sub-band top of a valence band of the hole potential well;

when an off-state bias voltage is applied to two ends of the II-type broken band energy gap quantum well structure, the quantum well is in a reverse band gap phase, and the energy of the lowest sub-band bottom of a conduction band of the electron potential well is lower than that of the highest sub-band top of a valence band of the hole potential well.

2. An infrared electro-absorption modulator based on a class II broken bandgap quantum well as claimed in claim 1, wherein the material of the electron potential well of the class II broken bandgap quantum well structure is selected from at least one of InAs, inAsSb, inGaAs, inGaAsSb; the material of the hole potential well is at least one selected from GaSb, gaInSb, gaAlSb, gaAsSb, gaAlAsSb, gaInAsSb, gaAlInSb, gaAlInAsSb; the material of the first potential barrier and the second potential barrier is at least one selected from AlSb, alGaSb, alGaAsSb, alInSb, alGaInSb, alInAsSb, alGaInAsSb.

3. An infrared electro-absorption modulator based on a class II bandgap quantum well as claimed in claim 1, wherein said infrared electro-absorption modulator based on a class II bandgap quantum well comprises a waveguide coupling configuration or a normal incidence configuration.

4. An infrared electro-absorption modulator based on class II bandgap quantum wells as claimed in claim 3, wherein said waveguide coupling configuration has a waveguide structure comprising at least: a base layer; a first cladding layer, a waveguide core layer and a second cladding layer are sequentially arranged on the upper side of the basal layer; a first contact electrode is arranged on the lower side of the basal layer or the upper side of the table top exposed by etching of the first coating layer; a second contact electrode is arranged on the upper side of the second cladding layer; the waveguide core layer comprises at least one absorption modulation area; the first coating layer and the second coating layer respectively adopt a heavily doped semiconductor single-layer or multi-layer structure; the first contact electrode and the second contact electrode respectively apply bias voltages to the absorption modulation region through the first cladding layer and the second cladding layer, so that the device for providing modulation bias voltages for the II-type broken band gap quantum well structure is formed.

5. An infrared electro-absorption modulator based on a class II bandgap quantum well as claimed in claim 4, wherein said waveguide core layer is of a separate confinement structure, further comprising a first separate confinement layer and a second separate confinement layer; the first and second limiting layers are doped semiconductor materials or multilayer structures, are adjacent to the lower and upper interfaces of the absorption modulation region, and have optical refractive indexes greater than those of the first and second cladding layers.

6. An infrared electro-absorption modulator based on a class II broken bandgap quantum well as claimed in claim 4, wherein said base layer further comprises a substrate and a buffer layer, said buffer layer having a thickness not less than 200nm for strain relief, dislocation isolation and impurity isolation to reduce the effect of the substrate on the device;

a first transition layer and a second transition layer are respectively arranged at the lower interface and the upper interface of the first cladding layer, a third transition layer and a fourth transition layer are respectively arranged at the lower interface and the upper interface of the second cladding layer, and the transition layers are used for reducing parasitic voltage drop caused by abrupt change of interfaces of adjacent area layers; the doping concentration of the transition layer is respectively between the doping concentrations of the adjacent materials at two sides of the transition layer.

7. An infrared electro-absorption modulator based on a class II broken bandgap quantum well as claimed in claim 3, wherein said normal incidence configuration is light incident perpendicular to the plane of the material layer of the absorption modulation zone, comprising at least: a bottom cladding layer, an absorption modulation region, a top cladding layer, a bottom electrode and a top electrode;

the bottom coating layer and the top coating layer are of a doped semiconductor single-layer or multi-layer structure; the absorption modulation area is arranged between the bottom cladding layer and the top cladding layer; the bottom electrode is a transparent electrode or a grating electrode or is provided with a light-transmitting window, and is arranged on the upper side of the etched exposed table top of the bottom cladding layer and forms electrical contact; the top electrode is a transparent electrode or a grating electrode or is provided with a light-transmitting window, and is arranged on the upper side of the top coating layer and forms electrical contact; the bottom electrode and the top electrode respectively apply bias voltages to the absorption modulation region through the bottom cladding layer and the top cladding layer to form a device for providing modulation bias voltages for the II-type broken band energy gap quantum well structure.

8. The infrared absorption modulator based on the class II broken band gap quantum well as claimed in claim 7, wherein a bottom high reflection film is arranged on the lower side of the bottom cladding layer, or a top high reflection film is arranged in a light transmission window area of a top electrode on the upper side of the top cladding layer, or both the bottom high reflection film and the top high reflection film are arranged; the bottom high reflection film and the top high reflection film are respectively formed by a distributed Bragg reflector or a metal film formed by alternately stacking a plurality of dielectric layers, so that a symmetrical or asymmetrical Fabry-Perot cavity structure is formed.

9. The infrared absorption modulator of claim 8, wherein a metal strip grating is disposed on or under at least one of the bottom highly reflective film, the top highly reflective film, the bottom cladding layer, or the top cladding layer to increase coupling of a vertical electric field component of incident light to the absorption modulation region, and wherein the grating period is less than or equal to a selected operating wavelength of the infrared absorption modulator.

10. A method of electro-optic modulation of selected light comprising the steps of:

a. The energy band structure of the semiconductor single-layer or multi-layer structure is provided with a conduction band and a valence band, and an electron state at the bottom of the conduction band and an electron state at the top of the valence band respectively belong to the eigenstates with different Hamiltonian volume properties of the system, and the conduction band and the valence band can be distinguished by the properties of the electron state at the bottom of the conduction band and the electron state at the top of the valence band;

d. converting from a normal bandgap phase to a reversed bandgap phase by varying a bias voltage applied to the semiconductor single-layer or multi-layer structure;

6) Setting the on-state bias voltage in the step 5), and changing the bias voltage applied to the semiconductor single-layer or multi-layer structure to enable the semiconductor single-layer or multi-layer structure to be converted from a normal band gap phase to the reverse band gap phase so as to achieve an off-state; the transition of the normal bandgap phase to the inverted bandgap phase results in a significant change in the absorption or refractive index of the semiconductor monolayer or multilayer structure; achieving a relatively significant modulation of the intensity or phase of the selected light with a relatively small bias swing.