Tunable mems-vcse with wide tuning range

Abstract

The application relates to the technical field of lasers, and particularly provides a tunable MEMS-VCSEL with a wide tuning range, a segmented MEMS structure is designed on a conventional VCSEL structure, the MEMS unit comprises two functional areas, each functional area comprises an air layer, the thickness of the two air layers is changed by adjusting the corresponding thickness control layer, the MEMS cantilever is deformed by voltage driving of the two functional areas, the resonant cavity length is changed, and then the output wavelength is tuned, the cantilever can be bent upwards and downwards by controlling the two MEMS functional areas respectively, the maximum displacement range of the MEMS cantilever is effectively enlarged, and the wavelength tuning range is improved. The application enlarges the maximum displacement range of the MEMS cantilever part, and solves the problem that the tuning range of the MEMS structure is limited under a small air gap thickness.

Description

Technical Field

[0001] This invention relates to the field of laser technology, specifically providing a tunable MEMS-VCSEL with a wide tuning range. Background Technology

[0002] Vertical-cavity surface-emitting lasers (VCSELs) possess numerous advantages, including low threshold current, circular spot size, high modulation bandwidth, single longitudinal mode lasing, ease of fabrication into high-density two-dimensional arrays, and relatively low manufacturing cost, leading to their widespread application in many fields. By integrating microelectromechanical systems (MEMS) technology with the VCSEL laser, an air gap exists between the MEMS structure and the VCSEL. External electrodes control the displacement of the MEMS structure, altering the thickness of the air gap. This change in air gap thickness results in a change in the resonant length of the VCSEL's resonant cavity. Therefore, continuous tuning of the VCSEL's output wavelength can be achieved by continuously changing the external control voltage of the MEMS. Compared to other tunable laser structures (e.g., external cavity tunable lasers, tunable DFB lasers), MEMS-VCSELs can achieve a tuning range greater than 10% of the relative wavelength, a more precise output spot size for the fundamental transverse mode, and wavelength tuning rates up to the MHz level. They have become a core laser source in medical spectroscopy and optical coherence tomography (OCT) technology. For laser light sources in OCT technology, the core parameters are the maximum wavelength tuning range and the wavelength tuning rate of the laser chip. The former directly affects the imaging depth and accuracy of human tissue, while the latter affects the system's imaging speed. Therefore, further expanding the maximum wavelength tuning range of MEMS-VCSEL devices presents a greater technical challenge to the performance parameters of the core light source in OCT applications.

[0003] Currently, the maximum tuning range achieved by MEMS-VCSELs for OCT applications is 150 nm. Theoretical research shows that the main factor limiting the maximum wavelength tuning range of tunable lasers is the free spectral range (FSR) of the device structure, which determines the theoretical upper limit of the tuning range. According to the formula, FSR = λ² / 2nL, where n is the equivalent refractive index of the optical cavity, L is the physical length of the optical cavity, and λ is the wavelength. For MEMS-VCSELs, improving the FSR of the structure is mainly achieved by reducing L, and the most effective way is to minimize the thickness of the air gap. When the FSR of the device is improved by using a small air gap structure, it is necessary to simultaneously ensure that the MEMS part can generate sufficient deformation to meet the air gap change required for FSR, achieving a match between the two, so that the device can break through a larger wavelength tuning range. Theoretically, for MEMS structures, the deformation generated by the micro / nano structure satisfies the one-third rule, that is, the maximum displacement of the MEMS structure deformation theoretically does not exceed one-third of the total air gap thickness. When the MEMS microstructure reaches approximately one-third of its maximum displacement, further increasing the tuning voltage will cause the cantilever deformation to cease to be linear, leading to random "catastrophic" pull-in phenomena that cause the entire micromirror structure to collapse and deform. Therefore, for MEMS-VCSEL devices capable of tuning beyond 150nm, the limiting factor for further increasing the tuning range is not only the optimization of the VCSEL device's structural parameters (e.g., loss, gain, resistance), but also how to further improve the maximum displacement of the MEMS structure, which has become a key technical challenge. Simultaneously, MEMS structures capable of covering a wide wavelength tuning range require driving voltages of tens of volts (e.g., approximately 60V is required to meet a 150nm tuning range), which increases system power consumption and necessitates a higher-performance external driving power supply. Existing technical solutions for improving the maximum displacement of MEMS components mainly involve adding piezoelectric tuning and thermoelectric tuning to the existing electrostatic tuning. The former method adds piezoelectric material to the existing MEMS cantilever structure, using the mechanical stress generated by the potential difference on the piezoelectric material surface to force the cantilever to make a larger displacement in the direction of movement, breaking the one-third rule limitation. However, the stress generated by the piezoelectric material is limited, which restricts the increase in tuning range. The latter method expands the tuning range by combining electrostatic tuning with thermal tuning. The traditional MEMS part is responsible for tuning the output wavelength of the VCSEL to shorter wavelengths. When switching to thermal tuning, the thermal expansion of the MEMS cantilever film tunes the output wavelength of the VCSEL to longer wavelengths. The combination of the two increases the overall wavelength tuning range of the VCSEL. However, the response speed of thermal tuning is very slow, resulting in a low overall tuning speed, which cannot meet the application requirements of the OCT field.

[0004] For MEMS-VCSEL devices with a tuning range greater than 100 nm, existing techniques for increasing the tuning range mainly focus on optimizing and improving the VCSEL's structural components, such as the quantum well gain bandwidth, device loss, and semiconductor / air cavity coupling efficiency. The air gap thickness in MEMS devices is typically designed to be 1.5–3 wavelengths (λ) thick, allowing the MEMS to generate sufficient displacement to meet the tuning range requirements. With the gradual improvement of epitaxial technology, fabrication techniques, and tunable device theory, the maximum tuning range achieved by MEMS-VCSELs is basically consistent with the theoretical FSR value of this structure, indicating that the tuning range has reached a bottleneck due to the device's own structure. Therefore, reducing the air gap thickness is another effective way to improve the FSR.

[0005] However, when MEMS-VCSELs adopt a small air gap structure, the following problems will be faced:

[0006] (1) Whether the maximum displacement of MEMS can cover the wavelength tuning requirements of a wide range, or whether the theoretical deformation of MEMS is artificially reduced in actual application due to factors such as materials and processes.

[0007] (2) The initial lasing wavelength of a MEMS-VCSEL structure is generally designed to be at a long wavelength, at which point the MEMS part is not loaded with a tuning voltage. By controlling the tuning electrodes, the output wavelength is tuned from the long wavelength to the short wavelength, covering the complete FSR tuning range. Therefore, the initial air gap thickness determines the degree of agreement between the actual wavelength tuning range and the theoretical value. However, due to uncertainties introduced by the process, such as process growth errors and MEMS cantilever release, the actual wavelength tuning range is often smaller than the design value. In small air gap structures, the influence of process errors will also be amplified.

[0008] (3) In a wide-range tuned MEMS-VCSEL structure, a very high driving voltage is required (for example, the driving voltage required to meet a 150nm tuning range is about 60V) to achieve a wide range of displacement of the MEMS cantilever. Furthermore, due to the reduction in air gap, in order to meet the continuity of the tuning wavelength in OCT applications, the tuning power supply needs to have high voltage and high resolution output requirements, which increases the requirements for the tuning power supply. Summary of the Invention

[0009] To address the aforementioned problems, this invention provides a tunable MEMS-VCSEL with a wide tuning range, which mainly expands the maximum displacement range achievable by the MEMS cantilever and adopts a segmented MEMS displacement tuning method.

[0010] The present invention provides a tunable MEMS-VCSEL with a wide tuning range, comprising a VCSEL unit and a MEMS unit.

[0011] MEMS units include:

[0012] A first thickness control layer is disposed on the electrodes of the VCSEL cell and forms a first air layer inside it. The first thickness control layer is used to control the thickness of the first air layer.

[0013] The MEMS cantilever, which is set on the first thickness control layer, can be deformed by applying voltage to change the length of the resonant cavity, thereby achieving tuning of the output wavelength.

[0014] The first MEMS electrode is disposed on the upper surface of the MEMS cantilever outside the light outlet. A second DBR is disposed at the center of the upper surface of the MEMS cantilever. The second DBR is a periodic structure of alternating growth of semiconductor materials with different refractive indices. The number of periods of the second DBR is less than the number of periods of the first DBR. The first DBR and the second DBR constitute a resonant cavity.

[0015] The second thickness control layer is disposed at the edge of the upper surface of the first MEMS electrode and forms a second air layer inside it. The second thickness control layer is used to control the thickness of the second air layer.

[0016] The second MEMS electrode is disposed on the second thickness control layer outside the light output port.

[0017] Preferably, the VCSEL unit includes:

[0018] First VCSEL electrode;

[0019] A substrate disposed on the first VCSEL electrode;

[0020] The first DBR, which is set on the substrate, is a periodic structure with alternating growth of materials with different refractive indices;

[0021] The active region, a multi-quantum-well structure, is used to provide optical gain. It is connected downward to the first DBR and upward to the insulating layer.

[0022] A current limiting layer, positioned above the middle of the insulating layer, is used to provide electrical isolation to non-injected current regions.

[0023] The second VCSEL electrode is laid on the outside of the light outlet, and the first thickness control layer is set on the upper surface edge of the second VCSEL electrode.

[0024] Preferably, spacers for adjusting the VCSEL cavity length are provided on the upper and lower sides of the active region.

[0025] Preferably, both the first DBR and the second DBR are grown alternately using dielectric film materials with high and low refractive indices, and the thickness of each dielectric film is one-quarter of the optical thickness of the wavelength.

[0026] Preferably, a spacer layer is also provided on the current limiting layer.

[0027] Preferably, the lower surface of the second VCSEL electrode is further provided with a VCSEL electrode contact layer to form an ohmic connection and reduce resistance.

[0028] Preferably, the lower surface of the second MEMS electrode is further provided with a MEMS electrode contact layer to form an ohmic connection and reduce resistance.

[0029] Compared with the prior art, the present invention can achieve the following beneficial effects:

[0030] This invention features an innovative design for the MEMS tuning section, expanding the maximum achievable displacement range of the MEMS cantilever and solving the problem of limited tuning range of MEMS structures with small air gap thickness. Simultaneously, the segmented MEMS displacement tuning method avoids the reduction in MEMS-VCSEL tuning range due to growth errors, reduces the maximum tuning voltage required for total MEMS displacement, and lowers the complexity of the MEMS drive power supply. Attached Figure Description

[0031] Figure 1 This is a structural diagram of a tunable MEMS-VCSEL with a wide tuning range provided according to an embodiment of the present invention.

[0032] The reference numerals in the figures include:

[0033] Substrate 100;

[0034] First DBR101;

[0035] Spacer layer 102;

[0036] Active region 103;

[0037] Current limiting layer 104;

[0038] VCSEL electrode contact layer 105;

[0039] First air layer 106;

[0040] Insulation layer 107;

[0041] Second VCSEL electrode 108;

[0042] First VCSEL electrode 109;

[0043] MEMS cantilever 110;

[0044] Second DBR111;

[0045] First thickness control layer 112;

[0046] Second air layer 113;

[0047] Second thickness control layer 114;

[0048] MEMS electrode contact layer 115;

[0049] Second MEMS electrode 116;

[0050] First MEMS electrode 117. Detailed Implementation

[0051] In the following description, embodiments of the invention will be described with reference to the accompanying drawings. In the description below, the same modules are denoted by the same reference numerals. Where the same reference numerals are used, their names and functions are also the same. Therefore, their detailed description will not be repeated.

[0052] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and do not constitute a limitation thereof.

[0053] like Figure 1 As shown, the tunable MEMS-VCSEL with a wide tuning range provided in this embodiment of the invention has a centrally symmetric structure, mainly composed of two parts: a VCSEL unit and a MEMS unit. The specific data involved in the structure are designed with the 1050nm band commonly used in OCT as the target. The overall structure includes the following components from bottom to top:

[0054] VCSEL unit:

[0055] The substrate 100 can be made of various semiconductor substrates, such as GaN, InP, GaAs, GaSb, and other group III-V semiconductor materials, and can cover the visible light, near-infrared, and mid-infrared wavelengths. In this embodiment of the invention, an N-type GaAs substrate 100 is specifically selected. A first VCSEL electrode 109 is disposed on the lower surface of the substrate 100. The first VCSEL electrode 109 is the negative electrode of the VCSEL unit, and the negative electrode material is Au-Ge / Ni / Au.

[0056] The first DBR101, disposed on the upper surface of the substrate 100, is a multi-period N-type DBR structure with alternating growth of high and low refractive index semiconductor materials. Specifically, it can be an AlxGa1-xAs semiconductor dielectric film material with high and low Al composition, typically with high Al composition x = 0.9 and low Al composition x = 0.1, and a period number of 32. The thickness of each dielectric film material is grown according to one-quarter of the optical thickness of the target wavelength, ultimately forming an N-type first DBR101 with a reflectivity > 99.5%. The reflectivity of the first DBR101 can be improved by increasing the period number. A larger period number can ensure that the first DBR101 has extremely high reflectivity and reflection bandwidth.

[0057] Spacer layer 102, which is grown on the upper surface of first DBR 101, is made of a material that satisfies the lattice matching of GaAs substrate 100.

[0058] The active region 103, grown on the upper surface of the aforementioned spacer layer 102, is a multi-quantum-well structure used to provide the optical gain required for laser formation. The classic quantum well structure configuration in the 1050nm band is as follows:

[0059] InxGa1-xAs / Ga1-xAsPx, x=0.2~0.3;

[0060] By adjusting the thickness of the trap or the P-component of the barrier, the emission band of the active region 103 can be tuned, thereby covering 1050nm.

[0061] Spacer layer 102 continues to grow to a specific thickness on the upper surface of active region 103. The spacer layer 102 on the upper and lower sides of active region 103 can be used to adjust the cavity length of VCSEL.

[0062] The insulating layer 107 is disposed on the upper surface of the spacer layer 102 above the active region 103, and can be made of SiO2, Si3N4 or other oxides, with a thickness of about 300 to 500 nm.

[0063] A current-limiting layer 104, positioned above the middle of the insulating layer 107, provides electrical isolation to the non-injected current region, thus restricting the current path. It can be fabricated using a semiconductor material with a high aluminum content, and the current-limiting layer 104 is laterally oxidized using a wet nitrogen oxidation apparatus. The oxidation rate is controlled by adjusting parameters such as oxidation temperature, water vapor temperature, pressure, and flow rate, while the lateral oxidation depth is controlled by adjusting the time. This results in an unoxidized central region and oxidized edges forming a high-resistance region, restricting the injected laser current to pass only through the central region of the corresponding aperture. Alternatively, ion implantation can also be used to form the high-resistance region.

[0064] Spacer layer 102 is disposed on current limiting layer 104. This spacer layer 102 and the spacer layers 102 on the upper and lower sides of active region 103 form an integral region. The total optical thickness of the three spacer layers 102, active region 103 and current limiting layer 104 needs to be designed to be half a wavelength that is an integer multiple of 1050nm wavelength, so as to meet the standing wave condition of laser. Insulating layer 107 can electrically isolate the non-current injection region of VCSEL unit, so that current can be injected into the surface of the top insulating layer.

[0065] The VCSEL electrode contact layer 105 is disposed above the top spacer layer 102. It is generally selected as a highly doped P-type GaAs material to reduce the Schottky barrier generated by the contact between the metal electrode and the VCSEL unit, form an ohmic contact, and reduce the resistance.

[0066] The second VCSEL electrode 108 is deposited on the VCSEL electrode contact layer 105 and insulating layer 107 outside the light outlet by electron beam evaporation. The second VCSEL electrode 108 is the positive electrode of the VCSEL unit, and the positive electrode material is Ti / Pt / Au. During the preparation, the electrode material corresponding to the light outlet is subjected to a lift-off stripping process in acetone solution to remove the electrode material part that is not needed for the light outlet. During operation, the first VCSEL electrode 109 and the second VCSEL electrode 108 are loaded by the excitation power supply of the chip, so that the VCSEL unit generates optical gain. When the laser resonance condition is reached, laser emission is formed.

[0067] MEMS unit:

[0068] A first thickness control layer 112 is deposited at the edge of the second VCSEL electrode 108 and forms a first air layer 106 inside it. The first thickness control layer 112 can be a metal (such as Ni, Ti, Pt, Cr, etc.) or a filling material (such as photoresist, BCB, polyimide, etc.). The thickness of the first thickness control layer 112 is designed according to the required thickness of the first air layer 106, and the first thickness control layer 112 is used to control the thickness of the first air layer 106. In addition, the first thickness control layer 112 also provides support and fixation for the MEMS cantilever 110 disposed above it.

[0069] The MEMS cantilever 110, disposed on the first thickness control layer 112, can be deformed by applying voltage, thereby changing the resonant cavity length and thus achieving tuning of the output wavelength. The MEMS cantilever 110 is made of Si3N4 material.

[0070] The first MEMS electrode 117 is deposited on the upper surface of the MEMS cantilever 110 outside the light-emitting port by electron beam evaporation. The first MEMS electrode 117 is the positive electrode of the MEMS unit, and the electrode material can be Ti / Pt / Au, etc. During fabrication, the electrode material corresponding to the light-emitting port is subjected to a lift-off process in an acetone solution to remove the electrode material portion that is not needed for the light-emitting port.

[0071] The second DBR111 is located at the center of the upper surface of the MEMS cantilever 110. The second DBR111 is a periodic structure formed by alternating growth of semiconductor dielectric films with high and low refractive indices. The thickness of each dielectric film layer is grown to one-quarter of the optical thickness of the target wavelength. Low-refractive-index dielectric films can be selected from materials such as SiO2 and Al2O3; high-refractive-index dielectric films can be selected from materials such as Si, Ta2O5, and Nb2O5. The first DBR101 and the second DBR111 constitute the resonant cavity of the MEMS-VCSEL, providing feedback to the light waves within the cavity to achieve laser resonance conditions. The number of periods in the second DBR111 is less than that in the first DBR101, and the reflectivity of the second DBR111 is lower than that of the first DBR101, allowing laser light to exit from the second DBR111.

[0072] A second thickness control layer 114 is disposed on the upper surface edge of the first MEMS electrode 117 and forms a second air layer 113 inside it. The second thickness control layer 114 is made of the same material as the first thickness control layer 112. The second thickness control layer 114 can be made of metal (such as Ni, Ti, Pt, Cr, etc.) or filler material (such as photoresist, BCB, polyimide, etc.). The thickness of the second thickness control layer 114 is designed according to the required thickness of the second air layer 113, and the second thickness control layer 114 is used to control the thickness of the second air layer 113.

[0073] MEMS electrode contact layer 115 is disposed above the second thickness control layer 114 and the light outlet portion is removed. The materials can generally be Si, SiO2, Si3N4, etc., to reduce the Schottky barrier generated by the contact between the metal electrode and the MEMS unit, form an ohmic contact, and reduce resistance.

[0074] The second MEMS electrode 116 is deposited on the MEMS electrode contact layer 115 outside the light-emitting port by electron beam evaporation. The second MEMS electrode 116 is the negative electrode of the MEMS unit, and the electrode material can be Au-Ge / Ni / Au structure. During fabrication, the electrode material corresponding to the light-emitting port is subjected to a lift-off process in acetone solution to remove the electrode material portion that is not needed for the light-emitting port.

[0075] Based on the above structure, the working process of the tunable MEMS-VCSEL with a wide tuning range provided in the embodiment of the present invention is briefly described. The first VCSEL electrode 109 and the second VCSEL electrode 108 are driven by the excitation power supply of the chip, so that the VCSEL unit generates optical gain. When the laser resonance condition is reached, laser emission is formed.

[0076] The second VCSEL electrode 108 and the first MEMS electrode 117 are driven by the MEMS driving power supply. At this time, the second VCSEL electrode 108 can also serve as the negative electrode of the first air layer 106 of the MEMS. By adjusting the driving power supply, the electrostatic attraction generated between the two plates in the first air layer 106 causes the MEMS cantilever 110 to deform upward from the center. The resonant cavity length of the MEMS-VCSEL decreases and the output wavelength is tuned to the shortwave direction.

[0077] The first MEMS electrode 117 and the second MEMS electrode 116 are driven by the MEMS driving power supply. At this time, the electrostatic attraction between the two plates in the second air layer 113 causes the MEMS cantilever 110 to deform upward from the center. The resonant cavity length of the MEMS-VCSEL increases and the output wavelength is tuned to the long wavelength direction.

[0078] Existing MEMS-VCSELs contain only one air layer, similar to the first air layer 106 in the embodiment of this invention. When a larger FSR is obtained by compressing the air layer thickness, the displacement of the cantilever is limited by the one-third rule, resulting in the deformation displacement of the cantilever not covering the displacement required for the tuning range. This invention, however, uses a single MEMS cantilever 110 shared in two MEMS structures. The first air layer 106 and the second air layer 113 correspond to the first and second functional regions of the MEMS unit, respectively, and their sum constitutes the overall tuning range of the MEMS-VCSEL. By controlling the two functional regions separately, the cantilever can bend upwards and downwards, effectively expanding the maximum displacement range of the MEMS cantilever 110, thus improving the wavelength tuning range. Simultaneously, since both functional regions of the MEMS unit are electrostatically tuned, they exhibit high tuning speeds, meeting the technical requirements of the OCT field. The advantages of this design are that it enables fast and precise wavelength tuning and has a large tuning range, making it a promising design for applications in optics and biomedicine.

[0079] Although embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present invention.

[0080] The specific embodiments of the present invention described above do not constitute a limitation on the scope of protection of the present invention. Any other corresponding changes and modifications made in accordance with the technical concept of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A wide tuning range tunable MEMS-VCSEL, characterized in that, The VCSEL unit and the MEMS unit are included; The MEMS unit includes: A first thickness control layer is arranged on the electrode of the VCSEL unit and internally forms a first air layer, and the first thickness control layer is used to control the thickness of the first air layer; A MEMS cantilever is arranged on the first thickness control layer, and the MEMS cantilever can be deformed by applying a voltage, the resonant cavity length is changed, and then the output wavelength is tuned; A first MEMS electrode is arranged on the upper surface of the MEMS cantilever outside the light outlet, a second DBR is arranged at the central position of the upper surface of the MEMS cantilever, the second DBR is a periodic structure of alternating growth of different refractive index semiconductor materials, the number of periods of the second DBR is less than that of the first DBR, and the first DBR and the second DBR form a resonant cavity; A second thickness control layer is arranged at the edge position of the upper surface of the first MEMS electrode and internally forms a second air layer, and the second thickness control layer is used to control the thickness of the second air layer; A second MEMS electrode is arranged on the second thickness control layer outside the light outlet; The VCSEL unit includes: A first VCSEL electrode; A substrate is arranged on the first VCSEL electrode; A first DBR is arranged on the substrate and is a periodic structure of alternating growth of different refractive index materials; An active region is a multi-quantum well structure and is used to provide optical gain, which is connected downward with the first DBR and connected upward with an insulating layer; A current limiting layer is arranged above the intermediate position of the insulating layer and is used to form electrical isolation for a non-injection current area; A second VCSEL electrode is arranged outside the light outlet, and a first thickness control layer is arranged at the edge position of the upper surface of the second VCSEL electrode; The second VCSEL electrode and the first MEMS electrode are driven by the driving power supply of the MEMS, the second VCSEL electrode simultaneously serves as the negative electrode of the first air layer of the MEMS, the driving power supply is adjusted, the electrostatic force generated between the two electrodes in the first air layer attracts the MEMS cantilever to generate a deformation of upward concave from the center, the resonant cavity length of the MEMS-VCSEL is reduced, and the output wavelength is tuned to the short wave direction; The first MEMS electrode and the second MEMS electrode are driven by the driving power supply of the MEMS, the electrostatic force generated between the two electrodes in the second air layer attracts the MEMS cantilever to generate a deformation of upward convex from the center, the resonant cavity length of the MEMS-VCSEL is increased, and the output wavelength is tuned to the long wave direction.

2. The wide-tuning-range tunable MEMS-VCSEL of claim 1, wherein, The upper and lower sides of the active region are provided with spacing layers for adjusting the VCSEL cavity length.

3. The wide-tuning-range tunable MEMS-VCSEL of claim 1, wherein, The first DBR and the second DBR are both grown alternately from high and low refractive index dielectric film materials, and the thickness of each dielectric film is one-fourth of the optical thickness of the wavelength.

4. The wide-tuning-range tunable MEMS-VCSEL of claim 2, wherein, The current limiting layer is further provided with a spacing layer.

5. The wide-tuning-range tunable MEMS-VCSEL of claim 1, wherein, The lower surface of the second VCSEL electrode is further provided with a VCSEL electrode contact layer to form an ohmic connection and reduce the resistance.

6. The wide-tuning-range tunable MEMS-VCSEL of claim 5, wherein, The lower surface of the second MEMS electrode is further provided with a MEMS electrode contact layer, forming an ohmic connection and reducing resistance.

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