Liquid crystal polarization tuning facet emitting semiconductor laser array and method of making the same

Abstract

The embodiment of the application relates to the technical field of semiconductor lasers, in particular to a liquid crystal polarization tuning surface-emitting semiconductor laser array and a preparation method thereof, the semiconductor laser comprising: a laser VCSEL array, an intermediate layer and an upper cover layer located above the laser VCSEL array; the laser VCSEL array comprising liquid crystal orientation lower layers arranged at intervals; the intermediate layer comprising a liquid crystal layer and a spacing layer, the spacing layer forming a wall surface structure at the edge of the laser VCSEL array, and the liquid crystal layer being located in the wall surface structure; the upper cover layer being a glass cover layer with a patterned ITO electrode; the upper cover layer comprising liquid crystal orientation upper layers arranged at intervals and ITO comb-shaped electrodes; and the laser VCSEL array being connected with the upper cover layer through the spacing layer. The liquid crystal layer of the liquid crystal polarization tuning surface-emitting semiconductor laser array provided by the application does not need to share the same electrode with the VCSEL array, so that the electronic crosstalk between them is reduced, the reliability is improved, and the stable orthogonal polarized light is realized by combining the birefringence characteristics of the liquid crystal.

Description

Technical Field

[0001] This application relates to the field of semiconductor laser technology, and in particular to a liquid crystal polarization tuned surface emitting semiconductor laser array and its fabrication method. Background Technology

[0002] Vertical-cavity surface-emitting lasers (VCSELs) offer superior characteristics compared to edge-emitting lasers, such as very low threshold current, circular output spot size, small divergence angle, and ease of integration into two-dimensional arrays. With the continuous development of the intelligent information world, VCSELs are playing an increasingly prominent role in consumer electronics. They are widely used in areas such as smartphone facial recognition, drone obstacle avoidance, virtual / augmented reality technology, robotic vacuum cleaners, and home security cameras. The increasing demand for miniaturization in smartphones and consumer electronics applications simplifies system design and manufacturing processes, reducing costs and complexity, making these devices even more advantageous.

[0003] Simultaneous emission of orthogonally polarized light from a single laser is the best way to integrate flood illumination and dot matrix projection. Current methods for controlling the polarization state of VCSELs using surface gratings face challenges: the fabrication of nanoscale subwavelength gratings is difficult, requiring electron beam lithography or nanoimprint technology, resulting in high costs. Furthermore, the direction of the subwavelength grating limits the flexibility of changing the polarization direction of the unit polarized light, leading to high power loss and low efficiency. Liquid crystal-tuned VCSEL arrays offer greater flexibility in polarization state. By voltage-controlled liquid crystals, two orthogonal polarization states can be emitted. When applied to mobile devices or facial recognition in driver assistance systems, this allows for smaller chip areas and further miniaturization. Simultaneous flood illumination and dot matrix projection can handle more environments, improving recognition accuracy. Moreover, by using ordinary photolithography on the ITO electrodes, the liquid crystal and VCSEL electrodes can be made independent, reducing mutual interference and simplifying fabrication. Summary of the Invention

[0004] This application provides a liquid crystal polarization tuned surface-emitting semiconductor laser array and its fabrication method. The liquid crystal layer of the semiconductor laser array and the VCSEL array do not need to share the same electrode, which reduces mutual electronic crosstalk, increases reliability, and achieves stable orthogonal polarized light by combining the birefringence characteristics of liquid crystal.

[0005] To address the aforementioned technical problems, in a first aspect, embodiments of this application provide a liquid crystal polarization tuned surface-emitting semiconductor laser array, comprising: a laser VCSEL array and an intermediate layer and a top cover layer located above the laser VCSEL array; the laser VCSEL array includes spaced-apart liquid crystal alignment lower layers; the intermediate layer includes a liquid crystal layer and a spacer layer, the spacer layer forming a ring of wall structures at the edge of the laser VCSEL array, the liquid crystal layer being located within the wall structures; the top cover layer is a glass cover layer with patterned ITO electrodes; the top cover layer includes spaced-apart liquid crystal alignment upper layers and ITO comb electrodes; the laser VCSEL array is connected to the top cover layer through the spacer layer; the liquid crystal alignment lower layers and liquid crystal alignment upper layers are used to achieve vertical alignment of the liquid crystals; when a voltage is applied, the liquid crystal molecules rotate under the action of a horizontal electric field between the ITO comb electrodes, birefringence occurs in the liquid crystal layer, the emitted light from the laser VCSEL array experiences phase delay, and the polarization state changes; the polarization state is controlled by voltage stabilization to achieve the desired effect.

[0006] In some exemplary embodiments, the top cover layer further includes: a glass substrate and a metal layer for bonding liquid crystal tuning wires; the glass substrate is located above the liquid crystal alignment top layer and the ITO comb electrode; the metal layer is located on the lower surface of the ITO comb electrode extending from the spacer layer.

[0007] In some exemplary embodiments, the height of the spacer layer is 6 micrometers.

[0008] In some exemplary embodiments, the VCSEL array includes an n-faceted electrode and a substrate, an n-type DBR, and an active layer sequentially stacked on the n-faceted electrode; above the active layer is a p-type DBR and a frustum structure disposed on the p-type DBR, the frustum structure having an oxide confinement layer; a current injection window is opened at the top of the frustum structure; the current injection window is filled with a cylindrical electrode, the diameter of the cylindrical electrode being smaller than the diameter of the frustum structure; a passivation layer and a p-faceted electrode are disposed above the p-type DBR.

[0009] In some exemplary embodiments, the passivation layer covers the side surface and part of the top surface of the frustum structure; the p-face electrode is located above the passivation layer, the p-face electrode covers the passivation layer located on the top surface of the frustum structure, and the p-face electrode has a laser emission hole corresponding to the cylindrical electrode.

[0010] In some exemplary embodiments, the liquid crystal alignment layer includes a first liquid crystal alignment layer filled within the laser emission aperture and a second liquid crystal alignment layer disposed above the passivation layer.

[0011] In some exemplary embodiments, the first liquid crystal alignment lower layer is flush with the upper surface of the p-side electrode covering the top surface of the frustum structure.

[0012] In some exemplary embodiments, the height of the frustum structure is 3 micrometers.

[0013] Secondly, embodiments of this application provide a method for fabricating a liquid crystal polarization tuned surface-emitting semiconductor laser array, comprising the following steps: First, fabricating a VCSEL array; then, forming a spaced-apart liquid crystal alignment lower layer on the upper surface of the VCSEL array; next, fabricating a capping layer; the capping layer is a glass capping layer with patterned ITO electrodes; the capping layer includes a spaced-apart liquid crystal alignment upper layer and ITO comb-shaped electrodes; then, forming a spacer layer between the VCSEL array and the capping layer, the spacer layer forming a ring wall structure at the edge of the VCSEL array; the VCSEL array is then connected through the spacer layer. The upper cover layer is connected to the spacer layer; next, liquid crystal is injected into the wall structure formed by the spacer layer, and a liquid crystal layer is formed between the laser VCSEL array and the upper cover layer; finally, the electrode surface of the upper cover layer is bonded to the laser VCSEL array containing the liquid crystal layer to obtain a semiconductor laser array; the lower liquid crystal alignment layer and the upper liquid crystal alignment layer are used to realize the vertical alignment of the liquid crystal; when a voltage is applied, the liquid crystal molecules rotate under the action of the horizontal electric field between the ITO comb electrodes, and birefringence occurs in the liquid crystal layer. The emitted light from the laser VCSEL array is delayed in phase and the polarization state is changed. The polarization state is controlled by voltage stabilization to achieve the desired effect.

[0014] In some exemplary embodiments, the preparation of the top cover layer includes the following steps: providing a glass substrate; forming an ITO conductive film on the glass substrate by electron beam evaporation; forming a comb-shaped electrode pattern on the ITO conductive film by photolithography and acid etching to obtain ITO comb-shaped electrodes; spin-coating a polyimide material over the glass substrate with the prepared ITO comb-shaped electrodes, and forming a liquid crystal alignment layer by UV irradiation; and sputtering metal layers on the ITO comb-shaped electrodes on both sides of the glass substrate for connecting liquid crystal tuning wires.

[0015] The technical solution provided in this application has at least the following advantages:

[0016] This application provides a liquid crystal polarization tuned surface-emitting semiconductor laser array and its fabrication method. The semiconductor laser includes: a laser VCSEL array and an intermediate layer and a top cover layer located above the laser VCSEL array; the laser VCSEL array includes spaced-apart liquid crystal alignment lower layers; the intermediate layer includes a liquid crystal layer and a spacer layer, the spacer layer forming a ring wall structure at the edge of the laser VCSEL array, and the liquid crystal layer located within the wall structure; the top cover layer is a glass cover layer with patterned ITO electrodes; the top cover layer includes spaced-apart liquid crystal alignment upper layers and ITO comb electrodes; the laser VCSEL array is connected to the top cover layer through the spacer layer; the liquid crystal alignment lower layers and liquid crystal alignment upper layers are used to achieve vertical alignment of the liquid crystals; when a voltage is applied, the liquid crystal molecules rotate under the action of a horizontal electric field between the ITO comb electrodes, birefringence occurs in the liquid crystal layer, the emitted light from the laser VCSEL array experiences phase delay, and the polarization state changes. The polarization state is controlled by voltage stabilization to achieve the desired effect.

[0017] This application provides a liquid crystal polarization-tunable surface-emitting semiconductor laser array and its fabrication method. The semiconductor laser array includes a VCSEL laser array, a top cover layer, and an intermediate layer connecting the two. The top cover layer is a patterned ITO electrode glass plate, which can control the liquid crystal layer. The liquid crystal layer achieves anisotropy of the laser polarization state, allowing two orthogonal polarization modes of the LP mode to generate different delays when passing through the liquid crystal, thereby achieving stable control of the two orthogonal polarizations. A single layer of patterned ITO coplanar electrodes provides an electric field for the liquid crystal layer. The liquid crystal layer does not need to share electrodes with the VCSEL array. Under the effect of the liquid crystal's "equivalent birefringence," the tuning efficiency of the liquid crystal layer is greatly improved. Attached Figure Description

[0018] One or more embodiments are illustrated by way of example with reference to the accompanying drawings. These illustrations do not constitute a limitation on the embodiments, and unless otherwise stated, the figures in the drawings are not to be limited by scale.

[0019] Figure 1 A schematic diagram of a partial structure of a liquid crystal polarization tuned surface-emitting semiconductor laser array provided in an embodiment of this application;

[0020] Figure 2 This is a schematic diagram of the structure of a liquid crystal polarization tuned surface emitting semiconductor laser array provided in an embodiment of this application;

[0021] Figure 3 This is a schematic diagram of the mesa etched by a liquid crystal polarization tuning surface-emitting semiconductor laser array according to an embodiment of this application;

[0022] Figure 4This is a schematic diagram of the injection current limiting hole formed after the lateral oxidation of the device oxide confinement layer according to an embodiment of this application;

[0023] Figure 5 This is a schematic diagram of the device structure after growing a SiO2 passivation layer according to an embodiment of this application;

[0024] Figure 6 This is a schematic diagram of the p-side electrode of a laser array formed by sputtering Ti / Au according to an embodiment of this application;

[0025] Figure 7 This is a schematic diagram of the fabrication of an n-face electrode of a laser array using a thinned substrate, provided in one embodiment of this application.

[0026] Figure 8 This is a schematic diagram of fabricating a liquid crystal lower alignment layer on a VCSEL according to an embodiment of this application;

[0027] Figure 9 This is a schematic diagram of the fabrication of a spacer layer on a VCSEL according to an embodiment of this application;

[0028] Figure 10 A schematic diagram of a pattern photolithographically formed on an ITO glass substrate provided in an embodiment of this application;

[0029] Figure 11 This is a schematic diagram of a liquid crystal alignment layer fabricated on a glass substrate according to an embodiment of this application;

[0030] Figure 12 This application provides an embodiment of sputtering a liquid crystal tuning electrode on an ITO comb electrode;

[0031] Figure 13 This is a schematic diagram of liquid crystal injection into a spacer layer according to an embodiment of this application;

[0032] Figure 14 This is a top view of an ITO comb-shaped electrode after photolithography, provided in an embodiment of this application.

[0033] Figure 15 This is a schematic diagram illustrating the orientation of liquid crystal under different voltages provided by the comb electrodes in one embodiment of this application;

[0034] Wherein, 1 is the n-side electrode, 2 is the substrate, 3 is the n-type DBR, 4 is the active layer, 5 is the oxide confinement layer, 6 is the SiO2 passivation layer, 7 is the p-side electrode, 8 is the lower liquid crystal alignment layer, 9 is the spacer layer, 10 is the liquid crystal, 11 is the metal layer, 12 is the upper liquid crystal alignment layer, 13 is the ITO electrode, and 14 is the glass substrate. Detailed Implementation

[0035] As can be seen from the background technology, existing polarization-tunable semiconductor lasers suffer from technical problems such as high cost, high power loss, low power, and high packaging difficulty.

[0036] To address the aforementioned technical problems, this application provides a liquid crystal polarization tuned surface-emitting semiconductor laser array and its fabrication method. The semiconductor laser array includes a VCSEL array and an intermediate layer and a top cover layer located above the VCSEL array. The VCSEL array includes spaced-apart lower liquid crystal alignment layers. The intermediate layer includes a liquid crystal layer and a spacer layer, with the spacer layer forming a ring of wall structures at the edge of the VCSEL array, and the liquid crystal layer located within the wall structures. The top cover layer is a glass cover layer with patterned ITO electrodes. The top cover layer includes spaced-apart upper liquid crystal alignment layers and ITO comb electrodes. The VCSEL array is connected to the top cover layer through the spacer layers. The lower and upper liquid crystal alignment layers are used to achieve vertical alignment of the liquid crystals. When a voltage is applied, the liquid crystal molecules rotate under the influence of a horizontal electric field between the ITO comb electrodes, resulting in birefringence in the liquid crystal layer. The emitted light from the VCSEL array experiences phase delay and a change in polarization state. The polarization state is controlled by voltage stabilization to achieve the desired effect. This application provides a liquid crystal polarization tuned surface-emitting semiconductor laser array and its fabrication method. The liquid crystal layer of the semiconductor laser array and the VCSEL laser array do not need to share the same electrode, which reduces mutual electronic crosstalk, increases reliability, and achieves stable orthogonal polarized light by combining the birefringence characteristics of liquid crystal.

[0037] The embodiments of this application will now be described in detail with reference to the accompanying drawings. However, those skilled in the art will understand that many technical details have been provided in the embodiments of this application to facilitate a better understanding of the application. However, the technical solutions claimed in this application can be implemented even without these technical details and various variations and modifications based on the following embodiments.

[0038] This application provides a liquid crystal polarization tuned surface-emitting semiconductor laser array, including: a laser VCSEL array and an intermediate layer and a top cover layer located above the laser VCSEL array. Figure 1 A schematic diagram of a portion of the structure of a liquid crystal polarization-tunable surface-emitting semiconductor laser array, as shown below. Figure 1As shown, the VCSEL array includes a lower liquid crystal alignment layer 8 spaced apart; an intermediate layer includes a liquid crystal layer and a spacer layer 9, the spacer layer 9 forming a wall structure at the edge of the VCSEL array, the liquid crystal layer being located within the wall structure; the liquid crystal layer is formed by injecting liquid crystal 10 into the wall structure formed by the spacer layer 9; the upper cover layer is a glass cover layer with patterned ITO electrodes; the upper cover layer includes a higher liquid crystal alignment layer 12 spaced apart and ITO electrodes 13, the ITO electrodes 13 being ITO comb electrodes; the VCSEL array is connected to the upper cover layer through the spacer layer 9; the lower liquid crystal alignment layer 8 and the upper liquid crystal alignment layer 12 are used to achieve vertical alignment of the liquid crystals; when a voltage is applied, the liquid crystal molecules rotate under the action of the horizontal electric field between the ITO comb electrodes, birefringence occurs in the liquid crystal layer, the emitted light from the VCSEL array experiences phase delay, and the polarization state changes; the polarization state is controlled by voltage stabilization to achieve the desired effect.

[0039] For details, please refer to Figure 2 The liquid crystal polarization-tunable surface-emitting semiconductor laser array provided in this application comprises, from top to bottom: a glass substrate 14 (with patterned ITO electrode glass substrate), an intermediate layer, and a laser VCSEL array. The intermediate layer includes a liquid crystal layer and a spacer layer 9. The spacer layer 9 forms a ring-shaped wall structure at the edge of the laser VCSEL array, and the liquid crystal layer is located within this wall structure. The patterned ITO electrode glass substrate can control the liquid crystal layer, achieving anisotropy of the laser polarization state. This allows two orthogonal polarization modes of the LP mode to generate different delays when passing through the liquid crystal, thereby achieving stable control of the two orthogonal polarizations. A single-layer patterned ITO coplanar electrode provides an electric field to the liquid crystal layer. The liquid crystal layer does not need to share electrodes with the VCSEL array, and the tuning efficiency of the liquid crystal layer is greatly improved under the effect of the liquid crystal's "equivalent birefringence." This invention also discloses a method for fabricating the aforementioned laser.

[0040] Please continue reading. Figure 2 In some embodiments, the top cover layer includes: a glass substrate 14 and a metal layer 11 for bonding liquid crystal tuning leads; wherein the metal layer 11 is a liquid crystal tuning electrode; the glass substrate 14 is located above the liquid crystal alignment top layer 12 and the ITO electrode 13 (ITO comb electrode); the metal layer 11 is located on the lower surface of the ITO comb electrode extending from the spacer layer 9. Figure 2 As shown, the metal layer 11 is disposed on both sides of the wall structure where the ITO electrode 13 extends out of the spacer layer 9.

[0041] In some embodiments, the height of the spacer layer 9 is 6 micrometers.

[0042] In some embodiments, the VCSEL array includes an n-plane electrode 1 and a substrate 2, an n-type DBR 3, and an active layer 4 sequentially stacked on the n-plane electrode 1. Above the active layer 4 is a p-type DBR and a frustum structure disposed on the p-type DBR, with an oxide confinement layer 5 inside the frustum structure. A current injection window is formed at the top of the frustum structure. A cylindrical electrode is filled in the current injection window, with the diameter of the cylindrical electrode being smaller than the diameter of the frustum structure. Above the p-type DBR is a passivation layer 6 and a p-plane electrode 7. The substrate 2 is a GaAs substrate, the DBR is a distributed Bragg mirror, and the passivation layer 6 is a SiO2 passivation layer.

[0043] Specifically, the structure of the liquid crystal polarization tuned surface emitting semiconductor laser array provided in this application is as follows: Figure 2 As shown, the structure, from bottom to top, mainly includes an n-plane electrode 1, a substrate 2, an n-type DBR 3, an active layer 4, an oxide confinement layer 5, a SiO2 passivation layer 6, a p-plane electrode 7, a lower liquid crystal alignment layer 8, a spacer layer 9, liquid crystal 10, a metal layer 11 (liquid crystal tuning electrode), an upper liquid crystal alignment layer 12, an ITO electrode 13, and a glass substrate 14. In this structure, the two independent parts of the coplanar ITO electrode are obtained through photolithography, development, and etching.

[0044] In some embodiments, the passivation layer 6 covers the side surface and part of the top surface of the frustum structure; the p-side electrode 7 is located above the passivation layer 6, the p-side electrode 7 covers the passivation layer 6 located on the top surface of the frustum structure, and the p-side electrode 7 has a laser light emission hole corresponding to the cylindrical electrode.

[0045] In some embodiments, the liquid crystal alignment lower layer 8 includes a first liquid crystal alignment lower layer filled within the laser emission aperture and a second liquid crystal alignment lower layer disposed above the passivation layer 6. It should be noted that the liquid crystal alignment lower layer 8 used to achieve the effect of "vertical alignment of liquid crystals between the liquid crystal alignment lower layer 8 and the liquid crystal alignment upper layer 12" is the first liquid crystal alignment lower layer filled within the laser emission aperture; the second liquid crystal alignment lower layer above the passivation layer 6 is a residue from spin coating and does not affect the overall structure.

[0046] In some embodiments, the first liquid crystal alignment layer is flush with the upper surface of the p-side electrode 7 covering the top surface of the frustum structure. For example... Figure 2 As shown, the passivation layer 6 covers the side surface and part of the top surface of the frustum structure, the p-side electrode 7 covers the upper surface of the passivation layer 6, and the p-side electrode 7 covers the passivation layer 6 located on the top surface of the frustum structure and covers the end of the passivation layer 6 located on the top surface of the frustum structure.

[0047] In some embodiments, the height of the frustum structure is 3 micrometers. For example, the oxide confinement layer may include four or more frustum structures, such as 4, 6, 8, or 10 frustum structures. As an example, Figure 1 The case where the oxide confinement layer includes a six-frustum structure is shown.

[0048] This application also provides a method for fabricating a liquid crystal polarization-tunable surface-emitting semiconductor laser array. Figures 3 to 14 This is a schematic diagram illustrating the fabrication process of the liquid crystal polarization tuned surface-emitting semiconductor laser array of this application. The fabrication method includes the following steps: First, fabricating a VCSEL laser array; then, forming a spaced-alternate liquid crystal alignment lower layer on the upper surface of the VCSEL laser array; next, fabricating a capping layer; the capping layer is a glass capping layer with patterned ITO electrodes; the capping layer includes a spaced-alternate liquid crystal alignment upper layer and ITO comb-shaped electrodes; then, forming a spacer layer between the VCSEL laser array and the capping layer, the spacer layer forming a ring wall structure at the edge of the VCSEL laser array; the VCSEL laser array and the capping layer are connected through the spacer layer. Next, liquid crystal is injected into the wall structure formed by the spacer layer, forming a liquid crystal layer between the laser VCSEL array and the top cover layer. Finally, the electrode surface (ITO electrode 13) of the top cover layer is bonded to the laser VCSEL array containing the liquid crystal layer to obtain a semiconductor laser array. The liquid crystal alignment lower layer and liquid crystal alignment upper layer are used to achieve vertical alignment of the liquid crystal. When a voltage is applied, the liquid crystal molecules rotate under the action of the horizontal electric field between the ITO comb electrodes, and birefringence occurs in the liquid crystal layer. The emitted light from the laser VCSEL array is delayed in phase and the polarization state is changed. The polarization state is controlled by voltage stabilization to achieve the desired effect.

[0049] Specifically, the fabrication of a VCSEL array includes the following steps:

[0050] Step 1: Grow 34.5 Al atoms on substrate 2 (n-type GaAs substrate) using metal-organic chemical vapor deposition (MOCVD). 0.9 Ga 0.1 As / Al 0.12 Ga 0.88 Si-doped n-type DBR3 composed of As was formed, and then an active layer 4 and a p-type DBR were sequentially formed on the n-type DBR3, such as... Figure 3 As shown. Active layer 4 consists of three quantum wells with a barrier thickness of 8 nm, and the material is Al. 0.3 Ga 0.7 As, with a well thickness of 6 nm, the material is GaAs. The doped p-type DBR consists of 20 Al pairs. 0.9 Ga 0.1 As / Al0.12 Ga 0.88 As composition. A 30nm thick Al layer exists between the active layer 4 and the top p-type DBR. 0.98 Ga 0.02 The As layer can be oxidized to Al. x O y This allows for the limitation of light and current.

[0051] Step 2: Use a combination of photolithography and selective wet etching to form a frustum structure until the Al2O3 sidewalls are exposed. 0.98 Ga 0.02 As layer.

[0052] Step 3: Place the etched mesa chip into the oxidation furnace, introduce nitrogen gas carrying moisture, and heat the oxidation furnace to make the Al... x O y Al reacts with water to form an oxide confinement layer 5, such as Figure 4 As shown; the oxide confinement layer 5 is annular, with an injection current confinement hole at its center.

[0053] Step 4: Deposit a 300 nm thick passivation material layer on the structure formed in Step 3 using plasma-enhanced chemical vapor deposition. The passivation material layer can be a SiO2 passivation layer. Etch the passivation material layer using a combination of photolithography and selective wet etching. A laser exit aperture is formed at the center of the frustum, forming passivation layer 6. Figure 5 As shown; the passivation layer 6 covers the upper surface of the oxide material and the side and part of the top surface of the frustum structure, that is, the passivation layer 6 forms a stepped structure at the edge of the top surface of the frustum structure.

[0054] Step 5: Sputter Ti-Au onto the p-side of the chip to form the p-side electrode 7 of the laser, etch out the light window, and etch away the Ti-Au at the window to form the light emission window, as shown. Figure 6 As shown. The p-side electrode 7 is located above the passivation layer 6, and the p-side electrode 7 covers the passivation layer 6 located on the top surface of the frustum structure. The p-side electrode 7 has a laser light emission hole (light emission window) corresponding to the cylindrical electrode.

[0055] Step 6: Thin the back side of the n-type substrate to 300μm-350μm, sputter an Au-Ge-Ni layer to form the n-face electrode 1 of the laser, and perform alloy annealing to ensure good ohmic contact between the n-face electrode and the back side of the n-type substrate. The VCSEL array fabrication of the laser is now complete. Figure 7 As shown.

[0056] After the VCSEL array is fabricated, polyimide material is spin-coated onto the prepared VCSEL, and a liquid crystal alignment layer 8 is formed by UV irradiation, as shown below. Figure 8As shown. The liquid crystal alignment lower layer 8 includes a first liquid crystal alignment lower layer filled in the laser light emission hole and a second liquid crystal alignment lower layer disposed above the passivation layer 6, wherein the first liquid crystal alignment lower layer is flush with the upper surface of the p-side electrode 7 covering the top surface of the frustum structure.

[0057] A spacer layer 9 of a certain thickness is prepared by photolithography, such as... Figure 9 As shown, it is then cured. The spacer layer 9 contains spacer spheres for fixing the height, and the spacer layer 9 forms a wall structure around the light-emitting unit.

[0058] Then, a capping layer is prepared. In some embodiments, preparing the capping layer includes the following steps: providing a glass substrate 14; forming an ITO conductive film on the glass substrate 14 by electron beam evaporation; forming a comb-shaped electrode pattern on the ITO conductive film by photolithography and acid etching to obtain ITO electrodes 13, such as... Figure 10 As shown. ITO electrode 13 is an ITO comb-shaped electrode. A top view of the ITO comb-shaped electrode after photolithography is shown below. Figure 14 As shown.

[0059] Polyimide material is spin-coated onto a glass substrate 14 having ITO electrodes 13, and a liquid crystal alignment layer 12 is formed by UV irradiation. Figure 11 As shown; metal layers 11 are sputtered onto the ITO electrodes 13 on both sides of the glass substrate 14, as follows. Figure 12 As shown, the metal layer 11 is a liquid crystal tuning electrode used to connect the liquid crystal tuning wire.

[0060] After fabricating the VCSEL array and the top cover layer, a spacer layer 9 is formed between the VCSEL array and the top cover layer. The spacer layer 9 forms a ring-shaped wall structure around the edge of the VCSEL array. The VCSEL array and the top cover layer are connected through the spacer layer 9. Then, liquid crystal 10 is injected into the wall structure formed by the spacer layer 9, such as... Figure 13 As shown, a liquid crystal layer is formed between the laser VCSEL array and the top cover layer; finally, the electrode surface (ITO electrode 13) of the top cover layer is bonded to the laser VCSEL array containing the liquid crystal layer, and after curing, a liquid crystal polarization tuned surface-emitting semiconductor laser array is obtained.

[0061] The fabrication method of the liquid crystal polarization tuned surface-emitting semiconductor laser array provided in this application will be described in detail below through specific embodiments.

[0062] This application provides a method for fabricating a liquid crystal polarization-tunable surface-emitting semiconductor laser array, comprising the following steps:

[0063] Step 1: Grow 34.5 pairs of Al atoms on an n-type GaAs substrate using metal-organic chemical vapor deposition (MOCVD). 0.9 Ga 0.1 As / Al 0.12 Ga 0.88 As is used to construct the n-type DBR. The active layer (also called the active region) consists of three quantum wells with a barrier thickness of 8 nm, and the material is Al. 0.3 Ga 0.7 As, with a well thickness of 6 nm, the material is GaAs. The doped p-type DBR consists of 20 Al pairs. 0.9 Ga 0.1 As / Al 0.12 Ga 0.88 The structure consists of As. A 30nm thick Al layer is placed between the active layer and the top p-type DBR. 0.98 Ga 0.02 The As layer can be oxidized to Al. x O y This allows for the limitation of light and current.

[0064] Step 2: Form a circular mesa by chemical etching. The etching depth should be deeper than the oxide confinement layer to expose the oxide confinement layer and prepare it for the wet oxidation process.

[0065] Step 3: Place the etched chip into the oxidation furnace, introduce nitrogen gas carrying water vapor, heat the oxidation furnace, and allow the Al in the oxidation confinement layer to react with water to generate oxides. Strictly control various parameters and oxidation time to ensure that the generated oxide layer is uniform, dense, and of appropriate thickness.

[0066] Step 4: After oxidation, cover the chip surface with a 300nm SiO2 insulating passivation layer. This layer should not be too thin or too thick. If it is too thin, pinholes are likely to appear, leading to leakage current. If it is too thick, it will put too much stress on the device and easily cause device damage.

[0067] Step 5: Overlay a circular electrode to etch away the SiO2 inside the electrode, thereby forming a current injection window. The diameter of the overlaid circular electrode is slightly smaller than the diameter of the mesa (truncated cone structure). This is to ensure that the sidewalls of the circular mesa are protected by a SiO2 insulating passivation layer, so as to prevent current from flowing directly into the substrate from the sidewalls of the mesa.

[0068] Step 6: Grow a Ti-Au layer on the P-surface as the P-surface electrode, and peel off the photoresist to expose the laser's output aperture.

[0069] Step 7: Grind the back side of the substrate to 300 micrometers, sputter Au-Ge-Ni layer to form the n-face electrode of the laser, and anneal it to make good ohmic contact between the n-face electrode and the back side of the n-type substrate. The VCSEL array of the laser is now fabricated.

[0070] Step 8: Spin-coat polyimide solution onto the fabricated VCSEL array and form a liquid crystal vertical alignment layer by UV irradiation.

[0071] Step 9: Spin-coat a photoresist doped with SPCEr microspheres onto the surface of the liquid crystal alignment layer, and after photolithography and development, form a spacer layer surrounding the light-emitting unit.

[0072] Step 10: Grow an ITO conductive film on the upper surface of a glass substrate using an electron beam evaporation stage.

[0073] Step 11: Photolithography is performed on the ITO thin film. Using HCl:H2O = 1:1 and adding a certain amount of FeCl3, the ITO is etched to form two comb-shaped electrodes.

[0074] Step 12: Spin-coat a polyimide solution onto the ITO surface and form a liquid crystal vertical alignment layer by UV irradiation.

[0075] Step 13: Sputter Ti / Au metal layers for bonding liquid crystal tuning leads on both sides of the comb-shaped electrode.

[0076] Step 14: Inject nematic positive liquid crystal into the spacer layer.

[0077] Step 15: Seal one side of the top cover alignment agent onto the spacer layer that has been injected with liquid crystal, and then bond and cure it. The complete device fabrication is now complete.

[0078] Compared with existing technologies, the liquid crystal polarization-tunable surface-emitting semiconductor laser array provided in this application has the following advantages: In the liquid crystal polarization-tunable surface-emitting semiconductor laser array containing ITO coplanar electrodes, a polyimide alignment layer is used to vertically align the liquid crystals. When a voltage is applied, the liquid crystal molecules rotate under the influence of the horizontal electric field between the interphase comb electrodes, resulting in birefringence in the liquid crystal layer. This causes a phase delay in the emitted light from the VCSEL, thus changing the polarization state. The polarization state can then be controlled by voltage stabilization to achieve the desired effect. Furthermore, the comb electrodes change the current situation where the liquid crystal and the VCSEL array share the same electrode, reducing mutual electronic crosstalk and increasing reliability and flexibility.

[0079] Figure 15 This is a schematic diagram illustrating the alignment of liquid crystal with different voltages at the comb electrodes according to an embodiment of this application. Figure 15As can be seen, as the voltage increases, the electric field provided by the comb electrodes causes the liquid crystal to gradually align with the direction of the electric field lines, forming an electrically controlled liquid crystal birefringent field, and the phase delay of the incident light changes accordingly. Therefore, the liquid crystal polarization-tunable surface-emitting semiconductor laser array provided in this application, when a voltage is applied, causes the liquid crystal molecules to rotate under the influence of the horizontal electric field between the ITO comb electrodes, resulting in birefringence in the liquid crystal layer. The emitted light from the VCSEL laser array experiences a phase delay, and the polarization state changes. By stabilizing the polarization state with voltage, the desired effect can be achieved.

[0080] Based on the above technical solutions, this application provides a liquid crystal polarization tuned surface-emitting semiconductor laser array and its fabrication method. The semiconductor laser includes: a laser VCSEL array and an intermediate layer and a top cover layer located above the laser VCSEL array; the laser VCSEL array includes spaced-apart liquid crystal alignment lower layers; the intermediate layer includes a liquid crystal layer and a spacer layer, the spacer layer forming a ring wall structure at the edge of the laser VCSEL array, and the liquid crystal layer located within the wall structure; the top cover layer is a glass cover layer with patterned ITO electrodes; the top cover layer includes spaced-apart liquid crystal alignment upper layers and ITO comb electrodes; the laser VCSEL array is connected to the top cover layer through the spacer layer; the liquid crystal alignment lower layers and liquid crystal alignment upper layers are used to achieve vertical alignment of the liquid crystals; when a voltage is applied, the liquid crystal molecules rotate under the action of a horizontal electric field between the ITO comb electrodes, birefringence occurs in the liquid crystal layer, the emitted light from the laser VCSEL array experiences phase delay, and the polarization state changes. The polarization state is controlled by voltage stabilization to achieve the desired effect.

[0081] This application provides a liquid crystal polarization-tunable surface-emitting semiconductor laser array and its fabrication method. The semiconductor laser array includes a VCSEL laser array, a top cover layer, and an intermediate layer connecting the two. The top cover layer is a patterned ITO electrode glass plate, which can control the liquid crystal layer. The liquid crystal layer achieves anisotropy of the laser polarization state, allowing two orthogonal polarization modes of the LP mode to generate different delays when passing through the liquid crystal, thereby achieving stable control of the two orthogonal polarizations. A single layer of patterned ITO coplanar electrodes provides an electric field for the liquid crystal layer. The liquid crystal layer does not need to share electrodes with the VCSEL array. Under the effect of the liquid crystal's "equivalent birefringence," the tuning efficiency of the liquid crystal layer is greatly improved.

[0082] Those skilled in the art will understand that the above-described embodiments are specific examples of implementing this application, and in practical applications, various changes in form and detail may be made without departing from the spirit and scope of this application. Any person skilled in the art can make their own modifications and alterations without departing from the spirit and scope of this application; therefore, the scope of protection of this application should be determined by the scope defined in the claims.

Claims

1. A liquid crystal polarization-tunable surface-emitting semiconductor laser array, characterized in that, include: A VCSEL laser array and an intermediate layer and a top cover layer located above the VCSEL laser array; The laser VCSEL array includes a liquid crystal alignment layer arranged at intervals; The intermediate layer includes a liquid crystal layer and a spacer layer. The spacer layer forms a wall structure around the edge of the VCSEL array, and the liquid crystal layer is located within the wall structure. The upper cover layer is a glass cover layer with patterned ITO electrodes; the upper cover layer includes a liquid crystal alignment upper layer and ITO comb electrodes arranged at intervals; the ITO comb electrodes are coplanar comb electrodes used to provide a horizontal electric field for the liquid crystal layer; the VCSEL laser array is connected to the upper cover layer through the spacer layer; The lower and upper liquid crystal alignment layers are used to achieve vertical alignment of the liquid crystals. When a voltage is applied, the liquid crystal molecules rotate under the action of the horizontal electric field between the ITO comb electrodes, and birefringence occurs in the liquid crystal layer. The emitted light from the VCSEL array of the laser is delayed in phase and the polarization state is changed. The polarization state is controlled by voltage stabilization to achieve the desired effect. The VCSEL array includes an n-faceted electrode and a substrate, an n-type DBR, and an active layer sequentially stacked on the n-faceted electrode. A p-type DBR is disposed above the active layer, and a passivation layer and a p-faceted electrode are sequentially disposed above the p-type DBR. A frustum structure is also disposed above the active layer on the p-type DBR, with a current injection window at the top of the frustum structure filled with a cylindrical electrode. A laser emission aperture corresponding to the cylindrical electrode is formed on the p-faceted electrode. The liquid crystal alignment underlayer includes a first liquid crystal alignment underlayer filled in the laser light emission aperture and a second liquid crystal alignment underlayer disposed above the passivation layer.

2. The liquid crystal polarization-tunable surface-emitting semiconductor laser array according to claim 1, characterized in that, The upper cover layer also includes: a glass substrate and a metal layer for bonding liquid crystal tuning wires; The glass substrate is located above the liquid crystal alignment layer and the ITO comb electrode; the metal layer is located on the lower surface of the ITO comb electrode extending from the spacer layer.

3. The liquid crystal polarization-tunable surface-emitting semiconductor laser array according to claim 1, characterized in that, The height of the spacer layer is 6 micrometers.

4. The liquid crystal polarization-tunable surface-emitting semiconductor laser array according to claim 1, characterized in that, The frustum structure has an oxidation confinement layer; the diameter of the cylindrical electrode is smaller than the diameter of the frustum structure.

5. The liquid crystal polarization-tunable surface-emitting semiconductor laser array according to claim 4, characterized in that, The passivation layer covers the side surface and part of the top surface of the frustum structure; The p-face electrode is located above the passivation layer, and the p-face electrode covers the passivation layer located on the top surface of the frustum structure.

6. The liquid crystal polarization-tunable surface-emitting semiconductor laser array according to claim 4, characterized in that, The first liquid crystal alignment layer is flush with the upper surface of the p-side electrode covering the top surface of the frustum structure.

7. The liquid crystal polarization-tunable surface-emitting semiconductor laser array according to claim 4, characterized in that, The height of the frustum structure is 3 micrometers.

8. A method for fabricating a liquid crystal polarization-tunable surface-emitting semiconductor laser array, the method being used to fabricate a liquid crystal polarization-tunable surface-emitting semiconductor laser array as described in any one of claims 1 to 7, characterized in that, Includes the following steps: Fabrication of VCSEL arrays; A liquid crystal alignment layer is formed on the upper surface of the VCSEL array of the laser; A top cover layer is prepared; the top cover layer is a glass cover layer with patterned ITO electrodes; the top cover layer includes a liquid crystal alignment top layer and ITO comb-shaped electrodes arranged at intervals; A spacer layer is formed between the VCSEL laser array and the upper cover layer, and the spacer layer forms a wall structure around the edge of the VCSEL laser array; The VCSEL laser array and the top cover layer are connected by a spacer layer; Liquid crystal is injected into the wall structure formed by the spacer layer, and a liquid crystal layer is formed between the VCSEL laser array and the top cover layer; The electrode surface of the upper cover layer is bonded to the VCSEL array containing the liquid crystal layer to obtain a semiconductor laser array; The lower and upper liquid crystal alignment layers are used to achieve vertical alignment of the liquid crystals. When a voltage is applied, the liquid crystal molecules rotate under the action of the horizontal electric field between the ITO comb electrodes, and birefringence occurs in the liquid crystal layer. The emitted light from the VCSEL array of the laser is delayed in phase and the polarization state is changed. The polarization state is controlled by voltage stabilization to achieve the desired effect.

9. The method for fabricating a liquid crystal polarization-tunable surface-emitting semiconductor laser array according to claim 8, characterized in that, The preparation of the top cover layer includes the following steps: Provide glass substrates; An ITO conductive film is formed on the glass substrate by electron beam evaporation. A comb-shaped electrode pattern is formed on an ITO conductive film by photolithography and acid etching to obtain an ITO comb-shaped electrode. Polyimide material is spin-coated on a glass substrate with a prepared ITO comb electrode, and a liquid crystal alignment layer is formed by UV irradiation. Metal layers are sputtered onto the ITO comb electrodes on both sides of the glass substrate to connect the liquid crystal tuning wires.

Images