Inter-band and inter-sub-band hybrid TM electric absorption modulator

Abstract

The invention discloses an inter-band and inter-sub-band hybrid TM electric absorption modulator which comprises a quantum well structure. The quantum well structure comprises at least one quantum well and at least one barrier; the quantum well is provided with a conduction band bottom energy level and at least one conduction band high-order energy level; the conduction band high-order energy level and the conduction band bottom energy level have the same energy difference as the designed absorbed photons. On the basis of conventional inter-band absorption, the width of a quantum well and the height of a barrier are ingeniously designed and adjusted, multiple conduction band energy levels are increased, modulatable sub-band absorption with the same absorption energy as the inter-band absorption is achieved, the quantum efficiency upper limit of the electric absorber can be increased, and the quantum efficiency of the electric absorber can be improved. The invention provides that inter-band and inter-band absorption is simultaneously used in a semiconductor quantum well to realize electro-absorption modulation on the same operating wavelength for the first time in the industry and academic circles, and has extremely high requirements on accurate calculation and design of an energy band.

Description

Technical Field

[0001] The present invention relates to the technical field of electro-absorption modulators, and in particular to an inter-band and inter-sub-band hybrid TM electro-absorption modulator. Background Art

[0002] The existing common electroabsorption modulator mainly relies on the absorption of electrons between bands, that is, the electrons jump from the valence band to the conduction band to absorb photons. The design of this conventional absorption mode is relatively simple, which is limited by the bandgap energy range of the material itself, and each electron absorbs one photon in each quantum well, so the maximum quantum absorption efficiency is limited. Summary of the invention

[0003] The purpose of the present invention is to provide an inter-band and inter-sub-band hybrid TM electro-absorption modulator. On the basis of conventional inter-band absorption, the present invention adjusts the quantum well width and barrier height through ingenious design, increases multiple conduction band energy levels, and realizes modulated inter-sub-band absorption with the same absorption energy as inter-band absorption, thereby increasing the upper limit of the quantum efficiency of the electro-absorber.

[0004] To achieve the above objectives, the following technical solutions are adopted:

[0005] An inter-band and inter-sub-band hybrid TM electro-absorption modulator comprises a quantum well structure; the quantum well structure comprises at least one quantum well and at least one barrier; the quantum well has a conduction band bottom energy level and at least one conduction band high-order energy level; the conduction band high-order energy level and the conduction band bottom energy level have the same energy difference as the designed absorbed photon.

[0006] Furthermore, the quantum well is designed such that: under zero bias, the inter-band and inter-sub-band absorption of photons of the designed wavelength of the quantum well is very small, while under operating bias, the absorption of the operating wavelength between sub-bands and between bands reaches peak values ​​simultaneously.

[0007] Furthermore, it also includes an n-doped substrate, a p-doped substrate, and a transition layer arranged on the n-doped substrate; the quantum well structure includes a highest barrier, a high-energy quantum well, an intermediate barrier, and a narrow-bandwidth quantum well; the highest barrier, high-energy quantum well, intermediate barrier and narrow-bandwidth quantum well are arranged in sequence from top to bottom between the transition layer and the p-doped substrate.

[0008] Furthermore, the highest barrier is made of AlGaAs material, has a thickness of 4 nm, and an energy band width of 2.13 eV.

[0009] Furthermore, the high energy quantum well is composed of Al 0.5 Ga 0.1 In 0.4 It is made of As material, with a thickness of 6.5nm and an energy band width of 1.9268eV.

[0010] Furthermore, the intermediate barrier is made of Al 0.8 Ga 0.1 In 0.1 Made of As material, it has a thickness of 1nm and an energy band width of 2.01086eV.

[0011] Furthermore, the narrow bandwidth quantum well is composed of Al 0.175 Ga 0.095 In 0.73 It is made of As material, with a thickness of 5nm and an energy band width of 0.800eV.

[0012] By adopting the above scheme, the beneficial effects of the present invention are:

[0013] Based on conventional interband absorption, the present invention adjusts the quantum well width and barrier height through ingenious design, adds multiple conduction band energy levels, and realizes modulated sub-band absorption with the same absorption energy as interband absorption, which can increase the upper limit of the quantum efficiency of the electric absorber. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 This is a schematic structural diagram of one embodiment of the present invention;

[0015] Figure 2 FIG. 1 is a diagram of an energy band structure and absorption characteristics at a low bias voltage in one embodiment of the present invention;

[0016] Figure 3 FIG. 1 is an energy band structure diagram under an operating voltage in one embodiment of the present invention;

[0017] Figure 4 is a graph of band-to-band absorption characteristics in one embodiment of the present invention;

[0018] Figure 5 FIG. 4 is a graph showing absorption characteristics between sub-bands in one embodiment of the present invention.

[0019] The accompanying drawings illustrate:

[0020] 1. Highest barrier; 2. High-energy quantum well; 3. Intermediate barrier; 4. Narrow-bandwidth quantum well. DETAILED DESCRIPTION

[0021] The present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0022] Reference Figures 1 to 5 As shown, the present invention provides an inter-band and inter-sub-band hybrid TM electro-absorption modulator, which in one embodiment includes a quantum well structure; the quantum well structure includes at least one quantum well and at least one barrier; the quantum well has a conduction band bottom energy level, and at least one conduction band high-order energy level; the conduction band high-order energy level and the conduction band bottom energy level have the same energy difference as the designed absorbed photon.

[0023] In order to solve the performance constraint of the conventional inter-band electro-absorption modulator with a low upper limit of electron utilization efficiency, in this embodiment, the present invention designs an inter-band and inter-sub-band absorption hybrid electro-absorption modulator, which increases the electron utilization efficiency by combining the two chain absorption reactions of inter-band and inter-sub-band, thereby improving the performance upper limit. The quantum well of the present invention contains a plurality of conduction band energy levels higher than the bottom energy level. At the same time, the modulated conduction band high-order energy level and the conduction band bottom energy level have the same energy difference as the designed absorbed photons. In addition, under zero bias, the inter-band and inter-sub-band absorption of photons of the designed wavelength is very small, while under operating bias, the absorption of the sub-band and inter-band to the operating wavelength reaches a peak at the same time. This combination can improve quantum efficiency, increase dynamic ER, and reduce current.

[0024] like Figure 1 As shown, in one embodiment, a specific design and an epitaxial growth connection method with other epitaxial layers are provided, including an n-doped substrate, a p-doped substrate, and a transition layer arranged on the n-doped substrate; the quantum well structure can be repeatedly arranged in multiple periods, and the quantum well structure includes a highest barrier 1, a high-energy quantum well 2, an intermediate barrier 3, and a narrow-bandwidth quantum well 4; the highest barrier 1, the high-energy quantum well 2, the intermediate barrier 3 and the narrow-bandwidth quantum well 4 are arranged in sequence from top to bottom between the transition layer and the p-doped substrate; the highest barrier 1 is made of AlGaAs material, with a thickness of 4nm and an energy band width of 2.13eV; the high-energy quantum well 2 is made of AlGaAs material, with a thickness of 4nm and an energy band width of 2.13eV; 0.5 Ga 0.1 In 0.4 As material, with a thickness of 6.5nm and a band width of 1.9268eV; the intermediate barrier 3 is made of Al 0.8 Ga 0.1 In 0.1 As material, with a thickness of 1nm and an energy band width of 2.01086eV; the narrow bandwidth quantum well 4 is made of Al 0.175 Ga 0.095 In 0.73 It is made of As material, with a thickness of 5nm and an energy band width of 0.800eV.

[0025] like Figure 2 As shown, under low bias, the quantum well formed by the conduction band (curve a) has three energy levels, namely curve b, curve c, and curve d. The bottom energy level of the quantum well formed by the valence band (curve f) is curve e. Among them, the inter-band absorption occurs between curve e and curve f, and the energy interval is 0.9537 eV, as shown in Figure 4As shown in curve j in , the absorption wavelength (1.3 μm) is lower than the operating wavelength 1.32 μm (curve k), and the absorption is lower at the operating wavelength. The inter-subband absorption occurs between curves d and b with an energy interval of 0.728 eV (>1.5 μm). Due to the low overlap of the wave function and the longer absorption peak than the operating wavelength, as shown in Figure 5 As shown in curve m in the figure, the initial absorption at the operating wavelength (curve k) is negligible. Under the operating voltage, the band structure is as follows Figure 3 As shown, the interband absorption is Figure 4 As shown in curve i, the energy level spacing between curve e and curve d is 0.94 eV, the inter-band absorption reaches the maximum, and the inter-sub-band absorption is as follows Figure 5 As shown in curve L in the figure, inter-subband absorption occurs between curve d and curve b, and the energy level spacing is 0.935 eV (1.326 μm) and reaches the maximum at the same time, achieving maximum absorption.

[0026] Key parameters such as the band spacing, under zero bias, the band spacing of curve e-curve d should be as large as possible from the operating energy, and the band spacing of curve d-curve b should be smaller than the operating photon energy; under the operating voltage, the energy spacings of curve e-curve d and curve d-curve b should be close to the operating photon energy to achieve the maximum extinction ratio; the design structure should make the wave function overlap rate of curve d-curve b smaller under low bias and achieve a larger overlap rate under the operating voltage.

[0027] In summary, the present invention can be used in combination with a TM polarization laser in various types of modulated optical chips to achieve high efficiency and large extinction ratio optical modulation, and can also be used alone as a TM polarization modulator, with strong versatility.

[0028] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. An inter-band and inter-sub-band hybrid TM electro-absorption modulator, characterized in that: It comprises a quantum well structure; the quantum well structure comprises at least one quantum well and at least one barrier; the quantum well has a conduction band bottom energy level and at least one conduction band high-order energy level; the conduction band high-order energy level and the conduction band bottom energy level have the same energy difference as the designed absorbed photons.

2. The inter-band and inter-sub-band hybrid TM electro-absorption modulator according to claim 1, characterized in that: The quantum well is designed such that: under zero bias, the inter-band and inter-sub-band absorption of photons of the designed wavelength is very small, while under operating bias, the inter-sub-band and inter-band absorption of the operating wavelength simultaneously reaches peak values.

3. The inter-band and inter-sub-band hybrid TM electro-absorption modulator according to claim 1, characterized in that: It also includes an n-doped substrate, a p-doped substrate, and a transition layer arranged on the n-doped substrate; the quantum well structure includes a highest barrier, a high-energy quantum well, an intermediate barrier, and a narrow-bandwidth quantum well; the highest barrier, the high-energy quantum well, the intermediate barrier, and the narrow-bandwidth quantum well are arranged in sequence from top to bottom between the transition layer and the p-doped substrate.

4. The inter-band and inter-sub-band hybrid TM electro-absorption modulator according to claim 3, characterized in that: The highest barrier is made of AlGaAs material, has a thickness of 4 nm and an energy band width of 2.13 eV.

5. The inter-band and inter-sub-band hybrid TM electro-absorption modulator according to claim 3, characterized in that: The high energy quantum well is made of Al 0.5 Ga 0.1 In 0.4 It is made of As material, with a thickness of 6.5nm and an energy band width of 1.9268eV.

6. The inter-band and inter-sub-band hybrid TM electro-absorption modulator according to claim 3, characterized in that: The intermediate barrier is made of Al 0.8 Ga 0.1 In 0.1 Made of As material, it has a thickness of 1nm and an energy band width of 2.01086eV.

7. The inter-band and inter-sub-band hybrid TM electro-absorption modulator according to claim 3, characterized in that: The narrow bandwidth quantum well is made of Al 0.175 Ga 0.095 In 0.73 It is made of As material, with a thickness of 5nm and an energy band width of 0.800eV.

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