Vortex light laser and preparation method thereof

Abstract

The invention relates to the technical field of semiconductor photoelectronics and liquid crystal materials, in particular to a vortex light laser and a preparation method thereof. The supporting structure is arranged on the laser light source; the liquid crystal structure is arranged on the supporting structure, and the liquid crystal structure is configured to convert linearly polarized light from the laser light source into circularly polarized light and further convert the circularly polarized light into vortex light. In addition, the cholesteric liquid crystal in the liquid crystal structure can change the rotation direction of the circularly polarized light under the irradiation of the ultraviolet light source, so that the topological charge number of the vortex light can be regulated and controlled. Compared with a traditional vortex light laser, the vortex light laser has the advantages of being high in conversion efficiency, low in preparation cost, high in preparation speed, capable of tuning vortex light of orbital angular momentum, capable of conducting autonomous regulation and control on emergent light under the condition that an external electric field is not introduced, and capable of improving the utilization rate of the vortex light. The preparation process is compatible with the traditional semiconductor process, the size is small, and the integration level is high.

Description

Technical Field

[0001] The invention relates to the technical fields of semiconductor optoelectronic technology and liquid crystal material technology, and in particular to a vortex light laser and a preparation method thereof. Background Art

[0002] With the increase in network traffic and the exponential growth of multimedia applications with high bandwidth requirements, big data technology has put forward strict requirements on the capacity, speed and performance of optical communication systems. For example, the migration from the fourth generation (4G) to the fifth generation (5G) of wireless communications requires a significant increase in data rates by 1,000 times. As an alternative solution to this challenge, orbital angular momentum (OAM) mode, also known as optical vortex (OV), is a new degree of freedom of light that can significantly improve the capacity of optical communications, data storage, classical and quantum information, etc. At present, most of the vortex light generation methods on the market rely on large external laser light sources. The volume and overall complexity of the system are difficult to overcome, which will inevitably lead to an increase in the overall cost of vortex light lasers. The chip-level lasers on the market all choose to use expensive and extremely high-precision micro-nano processing technology on inorganic materials, which is a catastrophic blow to the flexibility of the device and its process cost. Therefore, small-sized and low-cost vortex light lasers have become the focus of attention, and there is still room for improvement in existing technologies. Summary of the invention

[0003] In view of this, the present invention proposes an adjustable chip-level vortex light laser structure and a preparation method thereof, which effectively solves the problems of miniaturization of vortex light lasers and low cost and high preparation efficiency.

[0004] Specifically, according to a first aspect of the present invention, a vortex light laser is provided, comprising: a laser light source; a support structure arranged on the laser light source; and a liquid crystal structure arranged on the support structure, wherein the liquid crystal structure is configured to convert linearly polarized light from the laser light source into circularly polarized light, and further convert the circularly polarized light into vortex light.

[0005] In an embodiment of the present invention, the liquid crystal structure includes a first glass substrate and a second glass substrate arranged on the supporting structure, a cholesteric liquid crystal arranged between the first glass substrate and the second glass substrate, and a spherulite arranged on the surface of the second glass substrate. The liquid crystal structure is configured to convert the linearly polarized light from the laser light source into circularly polarized light through the cholesteric liquid crystal, and further convert the circularly polarized light into angularly polarized vector vortex light by absorbing the radially polarized light beam of the circularly polarized light through the spherulite.

[0006] In an embodiment of the present invention, the vortex light laser further includes an ultraviolet light source arranged adjacent to the cholesteric liquid crystal, wherein when the ultraviolet light source is turned on, the handedness of the cholesteric liquid crystal changes from an initial state, thereby changing the handedness of the circularly polarized light; when the ultraviolet light source is turned off, the handedness of the cholesteric liquid crystal returns to the initial state.

[0007] In an embodiment of the present invention, the spherulites are in the shape of a disk, the molecules are arranged radially along the disk, and the spherulites are made of the following materials: N1, N5-dihexylnaphthalene-1,5-diamine and N,N-dioctylnaphthalene diimide.

[0008] In an embodiment of the present invention, the laser light source includes a lower DBR, an active area, an oxidation restriction layer, an upper DBR, and a passivation layer grown in sequence on a GaAs substrate; a first electrode sputtered on the back of the GaAs substrate and a second electrode sputtered on the passivation layer.

[0009] In an embodiment of the present invention, the laser light source includes a single-tube laser or an array laser, and its wavelength includes 760nm~808nm; the first electrode and the second electrode each use any one of Ti / Au, Ni / Au and Cr / Au material systems.

[0010] According to a second aspect of the present invention, there is provided a method for preparing a vortex optical laser, comprising the following steps: S10. preparing a laser light source; S20. spin-coating a photoresist on the surface of the laser light source, performing photolithography, and then developing the photoresist to form a support structure, and exposing the table portion and the electrode portion of the laser light source to the outside; S30. preparing a liquid crystal structure; and S40. fixing the liquid crystal structure on the support structure, wherein step S30 specifically comprises the following steps: S32. uniformly mixing a nematic liquid crystal with a chiral agent and a molecular motor in proportion and heating them to a clearing point, pouring the mixed liquid crystal at the clearing point between a first glass substrate and a second glass substrate, sealing the first glass substrate and the second glass substrate and slowly cooling them to room temperature to form a cholesteric liquid crystal; and S33: applying a spherulite material on the second glass substrate, covering the spherulite material with NaCl crystals, heating the spherulite material and then slowly cooling it to room temperature, the spherulite molecules complete self-assembly to form a disc-shaped structure, dissolving the NaCl layer with deionized water, and preparing spherulites.

[0011] In an embodiment of the present invention, step S10 specifically includes: epitaxially growing a lower DBR, an active area, an oxidation restriction layer and an upper DBR on a GaAs substrate in sequence by metal organic chemical vapor deposition or molecular beam epitaxy, photolithography and etching a table top, performing lateral wet nitrogen oxidation on all sides to form an oxidation restriction hole for limiting the light field and current; growing a passivation layer and photolithography and etching the light exit hole of the passivation layer, then sputtering a second electrode and photolithography and etching the light exit hole of the second electrode, and finally sputtering a first electrode on the back side of the GaAs substrate; and in step S20, using a photoresist to spin-coat the surface of the second electrode as a whole, removing the light exit hole of the passivation layer and the photoresist at the light exit hole of the second electrode after photolithography and development, and the photoresist includes SU8 type photoresist.

[0012] In an embodiment of the present invention, step S30 further includes the following steps before step S32: S31. Parallel orientation is performed between the first glass substrate and the second glass substrate by using an orientation material and the first glass substrate and the second glass substrate are sealed around, leaving only gaps on both sides for pouring the mixed liquid crystal at the clearing point, wherein in step S2, after the liquid crystal is poured, the gap is sealed; wherein the orientation material includes polyimide and the sealing material includes UV curing glue.

[0013] In an embodiment of the present invention, step S40 specifically includes: applying UV light-curing glue on the support structure, placing the first glass substrate and the second glass substrate including the cholesteric liquid crystal and the spherulite on the support structure, irradiating UV light for fixing, and completing the preparation of the vortex light laser.

[0014] The tunable vortex light laser proposed in the present invention utilizes a liquid crystal structure to realize that the laser directly emits a tunable angular polarization vector vortex light beam, which has at least the following advantages: 1. The liquid crystal structure has an optical feedback effect on the laser, which can reduce the laser threshold current and the divergence angle of the emitted light; 2. No external light source input is required, it is highly integrated, and is conducive to the simplification and miniaturization of the detection system; 3. The liquid crystal structure is integrated with the laser, the preparation process is simple and fast, the process cost is low, and the precision requirement is low; 4. Liquid crystal materials are highly plastic and can be flexibly customized, enabling the preparation of vortex lasers of various wavelength bands; 5. The topological charge number of the vortex light emitted by the laser can be freely modulated. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention. For ordinary technicians in this field, other embodiments can be obtained based on these drawings without paying creative work.

[0016] Figure 1 A schematic diagram of a vortex light laser provided by one embodiment of the present invention; Figure 2 A flow chart of a method for preparing a vortex optical laser provided by one embodiment of the present invention; Figure 3 The laser emission spot observed by CCD; Figure 4a Forked interference fringes generated by off-axis self-interference of vortex light generated by left-handed cholesteric liquid crystal; and Figure 4b The forked interference fringes are produced by the off-axis self-interference of the vortex light generated by the right-handed cholesteric liquid crystal. DETAILED DESCRIPTION

[0017] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the embodiments of the present invention are further described in detail below in combination with specific embodiments and with reference to the accompanying drawings.

[0018] It should be noted that all expressions using "first" and "second" in the embodiments of the present invention are for distinguishing two non-identical entities with the same name or non-identical parameters. It can be seen that "first" and "second" are only for the convenience of expression and should not be understood as limitations on the embodiments of the present invention. The subsequent embodiments will not explain this one by one.

[0019] The present invention proposes an adjustable chip-level vortex light laser and a preparation method thereof to solve the shortcomings of existing vortex light lasers, such as large size, high cost, complex manufacturing process, and single-tube uncontrollable. Compared with the traditional vortex light laser that requires the use of a large external laser light source, the laser of the present invention is a vertical cavity surface emitting laser (VCSEL). As an advanced chip-level laser, VCSEL can realize the miniaturization of vortex light lasers due to its advantages such as low threshold current, high energy efficiency, and circularly symmetric beam profile. In order to avoid complex and costly micro-nano processing on the laser, the liquid crystal structure is directly integrated on the surface of the VCSEL, and the VCSEL output light can be directly controlled, which reduces the preparation cost. At the same time, the reflective characteristics of the liquid crystal can provide an optical feedback effect for the laser, further reducing the threshold current of the laser and improving the overall performance of the laser.

[0020] The vortex light free tuning proposed in the present invention is based on optical polarization analysis. Circularly polarized light is a light beam that carries spin angular momentum, and it does not carry orbital angular momentum itself. In a rectangular coordinate system, a circularly polarized light beam can be decomposed into two orthogonal linear polarization components with the same amplitude and a phase difference of π / 2. By using basis vector transformation, the two orthogonal basis vectors in the rectangular coordinate system are transformed into radial basis vectors and angular basis vectors in the cylindrical coordinate system, and the expression is as follows:

[0021]

[0022] Where P(r) represents the amplitude of light in the coordinate system. For the sake of simplicity, we can assume that P(r)=1, e x and e y Represent two orthogonal basis vectors in the rectangular coordinate system, e r and e φ represent the radial component and angular component in the cylindrical coordinate system, respectively. φ represents the phase angle, E L is left-handed circularly polarized light and E R is right-handed circularly polarized light, i By transforming the coordinates, the Berry phase is generated, and the circularly polarized light, which originally only has spin angular momentum, can be represented by two radially polarized beams and angularly polarized beams carrying OAM. This means that as long as the radial polarization component in the circularly polarized light is filtered, the beam will become an angularly polarized beam carrying orbital angular momentum.

[0023] The orbital angular momentum carried by the emitted vortex light is different for different handedness of circularly polarized light. Based on this principle, the present invention adds a molecular motor to the cholesteric liquid crystal, which changes handedness under the stimulation of ultraviolet light, so that the direction of the emitted circularly polarized light also changes, and thus the vortex light can be controlled to change, thereby solving the problem of freely regulating the emitted vortex light with a single laser.

[0024] Based on the above principle, the first aspect of the present invention provides a vortex light laser 100, such as Figure 1As shown, it includes: a laser light source 110; a support structure 8 disposed on the laser light source 110; and a liquid crystal structure 130 disposed on the support structure 8, wherein the liquid crystal structure 130 is configured to convert the linear polarized light from the laser light source 110 into circular polarized light, and further convert the circular polarized light into vortex light. The vortex light laser 100 of the present invention uses the liquid crystal structure 130 disposed on the laser light source 110 through the support structure 8 to realize that the vortex light laser 100 directly emits a tunable angular polarization vector vortex light beam, wherein the laser light source 110 provides linear polarized light, and the support structure 8 is used to separate the liquid crystal structure 130 from the laser light source 110, to prevent the liquid crystal structure 130 from contacting the laser light source 110 and damaging the laser light source 110.

[0025] exist Figure 1 In the illustrated embodiment, the liquid crystal structure 130 may include a first glass substrate 12 and a second glass substrate 9 disposed on a support structure 8, a cholesteric liquid crystal 10 disposed between the first glass substrate 12 and the second glass substrate 9, and a spherulite 11 disposed on the surface of the second glass substrate 9. The liquid crystal structure 130 is configured to convert linearly polarized light from a laser light source 110 into circularly polarized light through the cholesteric liquid crystal 10, and further convert the circularly polarized light into angularly polarized vector vortex light by absorbing the radially polarized light beam of the circularly polarized light through the spherulite 11.

[0026] The first glass substrate 12 and the second glass substrate 9 are arranged on the upper and lower sides of the cholesteric liquid crystal 10, and are used to orient the cholesteric liquid crystal, protect the cholesteric liquid crystal 10 and prevent it from flowing. The cholesteric liquid crystal 10 can convert the linear polarized light emitted by the VCSEL into circularly polarized light. At the same time, the cholesteric liquid crystal 10 will be stimulated by the ultraviolet light source to change the hand direction, thereby changing the hand direction of the circularly polarized light, and finally changing the hand direction of the vortex light, realizing the autonomous light regulation of the vortex light, as described in other parts of the present invention. The spherulite 11 can absorb radially polarized light, and then can convert the incident circularly polarized light into angularly polarized vector vortex light.

[0027] The vortex light laser 100 may further include an ultraviolet light source (not shown) disposed adjacent to the cholesteric liquid crystal 10. As described above, the ultraviolet light source may be used to change the handedness of the circularly polarized light, wherein when the ultraviolet light source is turned on, the handedness of the cholesteric liquid crystal 10 changes from the initial state, thereby changing the handedness of the circularly polarized light; when the ultraviolet light source is turned off, the handedness of the cholesteric liquid crystal 10 returns to the initial state.

[0028] In order to achieve the above purpose, the cholesteric liquid crystal 10 can be a cholesteric liquid crystal with tunable spiral direction under light stimulation, which can be a mixture of multiple substances. By adjusting the ratio of liquid crystal to chiral agent and molecular motor in the mixture, the pitch of the cholesteric liquid crystal 10 can be changed. When the wavelength of the incident linear polarized light matches the pitch of the liquid crystal, the linear polarized light will be modulated into circular polarized light. When the liquid crystal is irradiated by an ultraviolet light source, the handedness of the liquid crystal will gradually change, and eventually become a cholesteric liquid crystal with the same pitch and opposite handedness, so that the handedness of the circular polarization of the outgoing light is also reversed; when the ultraviolet light source is removed, the liquid crystal will gradually return to its initial state.

[0029] In one embodiment, when the ultraviolet light source is turned off, when the wavelength of the linear polarized light incident on the cholesteric liquid crystal 10 (e.g., left-handed cholesteric liquid crystal) from the laser light source 110 matches the pitch of the cholesteric liquid crystal 10, the linear polarized light will be modulated into circular polarized light (e.g., right-handed circular polarized light). When the ultraviolet light source is turned on, the cholesteric liquid crystal 10 is irradiated by ultraviolet light, and the rotation direction of the cholesteric liquid crystal 10 will gradually change, and eventually become a cholesteric liquid crystal with the same pitch and opposite rotation direction (e.g., from left-handed cholesteric liquid crystal to right-handed cholesteric liquid crystal), so that the rotation direction of the circular polarization of the outgoing light is also reversed (e.g., from right-handed circular polarized light to left-handed circular polarized light); when the ultraviolet light source is removed, the cholesteric liquid crystal 10 will gradually return to the initial state (e.g., return to the left-handed cholesteric liquid crystal state).

[0030] The spherulite 11 may be in the shape of a disk, and the liquid crystal molecules are arranged radially along the disk. The spherulite 11 may realize radial polarization absorption and angular polarization transmission for any polarized light with matching wavelength. The spherulite 11 may be made of the following materials: N1, N5-dihexylnaphthalene-1,5-diamine and N,N-dioctylnaphthalene diimide.

[0031] Reference again Figure 1 , the laser light source 110 includes a lower DBR 2, an active area 3, an oxidation restriction layer 4, an upper DBR 5, and a passivation layer 6 grown sequentially on a GaAs substrate; a first electrode 1 sputtered on the back of the GaAs substrate and a second electrode 7 sputtered on the passivation layer 6. The second electrode 7 is used to inject current into the vortex light laser 100. The passivation layer 6 and the second electrode 7 each include light exit holes 6a and 7a. The laser light source 110 may include a single-tube laser or an array laser, and its wavelength includes 760nm~808nm. In one embodiment, the wavelength of the laser light source 110 is 760nm. The first electrode 1 and the second electrode 7 can each use any one of the Ti / Au, Ni / Au and Cr / Au material systems.

[0032] It should be understood that only the GaAs substrate is used as an example here for description, however, the present invention is also applicable to other substrates besides the GaAs substrate. When other substrates are used, the wavelength range of the laser light source of the vortex light laser can be 523nm ~ 760nm, which is also within the scope of the present invention.

[0033] In summary, the vortex light laser 100 provided by the present invention includes, from bottom to top, a laser light source 110, a support structure 8, a cholesteric phase liquid crystal 10 and a spherulite 11, wherein the laser light source 110 includes, from bottom to top, a first electrode 1, a lower DBR 2, an active region 3, an oxidation restriction layer 4, an upper DBR 5, a passivation layer 6 and a second electrode 7. Through the reasonable configuration of the above structure, that is, the liquid crystal structure 130 is integrated into the vortex light laser 100, so as to realize the conversion of the linearly polarized light emitted by the VCSEL into circularly polarized light, and then absorb the radially polarized light, and then the incident circularly polarized light can be converted into angularly polarized vector vortex light, and at the same time, the handedness is changed under the stimulation of the ultraviolet light source, thereby changing the handedness of the circularly polarized light, and finally changing the handedness of the vortex light, so as to realize the autonomous optical regulation of the vortex light. Moreover, the vortex light laser 100 described in the present invention has extremely high light conversion efficiency, high integration, small size, low manufacturing process cost, and can be quickly mass-produced; at the same time, it also has a single-tube tunable characteristic, and can spontaneously change the orbital angular momentum of the emitted vortex light under the control of external light (such as the ultraviolet light source as described above).

[0034] According to a second aspect of the present invention, a method for preparing the vortex optical laser 100 as described in the above embodiment is provided. Figure 2 As shown, the method comprises the following steps: S10. Preparing a laser light source 110; S20. Spin-coating a photoresist on the surface of the laser light source 110 for photolithography and then developing to form a support structure 8, and exposing the mesa portion and the electrode portion of the laser light source to the outside world; S30. Preparing a liquid crystal structure 130; and S40. The liquid crystal structure 130 is fixed on the support structure 8, Wherein, step S30 specifically includes the following steps: S32. The nematic liquid crystal, the chiral agent and the molecular motor are uniformly mixed in proportion and heated to a clearing point, the mixed liquid crystal at the clearing point is poured between the first glass substrate 12 and the second glass substrate 9, the first glass substrate 12 and the second glass substrate 9 are sealed and slowly cooled to room temperature to form a cholesteric liquid crystal 10; and S33: smearing the spherulite material on the second glass substrate 9, covering the spherulite material with NaCl crystals, heating the spherulite material and then slowly cooling it to room temperature, the spherulite molecules complete self-assembly to form a disc-shaped structure, dissolving the NaCl layer with deionized water, and obtaining spherulites 11.

[0035] Among them, step S10 specifically includes: using metal organic chemical vapor deposition or molecular beam epitaxy to epitaxially grow the lower DBR 2, the active area 3, the oxidation restriction layer 4 and the upper DBR 5 on the GaAs substrate in sequence, photolithography and etching to form a table top, and lateral wet nitrogen oxidation around to form an oxidation restriction hole for limiting the light field and current; growing a passivation layer 6 and photolithography and etching the light exit hole 6a of the passivation layer 6, then sputtering the second electrode 7 and photolithography and etching the light exit hole 7a of the second electrode 7, and finally sputtering the first electrode 1 on the back side of the GaAs substrate; and in step S20, using photoresist to spin-coat the surface of the second electrode 7 as a whole, after photolithography and development, remove the photoresist at the light exit hole 6a of the passivation layer 6 and the light exit hole 7a of the second electrode 7, and the photoresist may include SU8 type photoresist.

[0036] Step S30 further includes the following steps before step S32: S31. Parallel orientation is performed between the first glass substrate 12 and the second glass substrate 9 by using an orientation material and the first glass substrate 12 and the second glass substrate 9 are sealed around, leaving only gaps on both sides for pouring the mixed liquid crystal at the clearing point, wherein in step S2, after the liquid crystal is poured, the gap is sealed; wherein the orientation material includes polyimide and the sealing material includes UV curing glue.

[0037] Step S40 specifically includes: applying UV light-curing glue on the support structure 8, placing the first glass substrate 12 and the second glass substrate 9 including the cholesteric liquid crystal 10 and the spherulite 11 on the support structure 8, irradiating UV light for fixing, and completing the preparation of the vortex light laser 100.

[0038] In step S32, the nematic liquid crystal, the chiral agent and the molecular motor are mixed uniformly at a mass percentage of 3% to 15%: 15% to 30%: 3% to 12% and heated to a clearing point. In addition, a photoinitiator of, for example, 0.1% to 1% by mass can be added to the mixed material.

[0039] In one embodiment, the nematic liquid crystal may be, for example, a SLC1717 model nematic liquid crystal, the chiral agent may be, for example, a S811 model chiral agent, and the molecular motor may be, for example, a M1 model molecular motor.

[0040] The present invention is further described below by specific examples: First, the vortex light laser 100 of the present invention is prepared, which may include the following steps: Step 1: epitaxially grow the lower DBR 2, active area 3, oxidation restriction layer 4 and upper DBR 5 on the GaAs substrate in sequence by metal organic chemical vapor deposition (MOCVD) or molecular beam epitaxy (MBE), photolithography and etching to form a table top, and lateral wet nitrogen oxidation is performed around to form an oxidation restriction hole to limit the light field and current; grow a passivation layer 6 and photolithography and etching the light exit hole 6a of the passivation layer 6, then sputter the second electrode 7 and photolithography and etching the light exit hole 7a of the second electrode 7, and finally sputter the first electrode 1 on the back of the GaAs substrate to make a laser light source 110; wherein the laser light source 110 can include a single tube laser or an array laser. The first electrode 1 can use a Ti / Au material system, and the second electrode 7 can use a Ni / Au material system.

[0041] Step 2: On the basis of the prepared laser light source 110, use a coating machine to spin-coat SU8 photoresist, perform photolithography, and then develop to form a support structure 8, and allow the laser table portion and the electrode portion to be exposed to the outside.

[0042] Step 3: Evenly mix the nematic liquid crystal, the chiral agent and the molecular motor, heat to the clearing point with a hot plate, pour the mixed liquid crystal at the clearing point between the first glass substrate 12 and the second glass substrate 9, seal the first glass substrate 12 and the second glass substrate 9 and slowly cool to room temperature to form a cholesteric liquid crystal 10. The mass ratio of the nematic liquid crystal to the chiral agent and the molecular motor can be: 8%: 20%: 9%. You can also add, for example, 0.5% by mass of a photoinitiator to the above-mentioned mixed material, then dissolve it in an organic solvent such as dichloromethane, mix evenly, and heat to the clearing point. Alternatively, the mixture including the nematic liquid crystal, the chiral agent and the molecular motor can also be directly purchased for commercial purposes.

[0043] Step 4: Apply the spherulite material on the upper layer of the second glass substrate 9, cover the spherulite material with NaCl crystals, heat the spherulite material and slowly cool it to room temperature, the spherulite molecules complete self-assembly to form a disc-shaped structure, dissolve the NaCl layer with deionized water, and the spherulite 9 is completed.

[0044] Step 5: Apply UV light-curing glue on the support structure 8, place the first glass substrate 12, the second glass substrate 9, the cholesteric liquid crystal 10 contained therebetween, and the spherulites 11 contained on the second glass substrate 9 on the support structure 8, irradiate UV light for fixation, and complete the preparation of the vortex light laser 100.

[0045] After the vortex light laser 100 is prepared, the vortex light laser 100 is turned on to obtain vortex light. Figure 3 shown. Figure 3FIG. 1 shows the output light spot of the vortex light laser 100 observed by using a CCD. Figure 3 As shown by the dotted circle in the figure, the light spot is in a donut shape with a dark center and bright surroundings, which is consistent with the characteristics of a vortex light spot.

[0046] Figure 4a The forked interference fringes are produced by the off-axis self-interference of the vortex light generated by the left-handed cholesteric phase liquid crystal. From the number of splitting times, it can be seen that all the forked fringes are divided into two fringes by one fringe, proving the existence of OAM of the obtained light beam and the topological charge number is -1.

[0047] If an ultraviolet light source is set and turned on at a position adjacent to the cholesteric liquid crystal 10, the rotation direction of the cholesteric liquid crystal 10 will gradually change due to the irradiation of the cholesteric liquid crystal 10 with ultraviolet light, for example, from left-handed cholesteric liquid crystal to right-handed cholesteric liquid crystal with the same pitch and opposite rotation direction, so that the rotation direction of the circular polarization of the output light is also flipped from right-handed circularly polarized light to left-handed circularly polarized light.

[0048] Figure 4b The figure shows the forked interference fringes generated by the off-axis self-interference of the vortex light generated by the right-handed cholesteric liquid crystal. The vortex light laser 100 is irradiated with ultraviolet light and the forked fringes are waited for to reappear to complete the hand-direction reversal of the cholesteric liquid crystal 10. At this time, the opening direction of the forked fringes is opposite to that when there is no ultraviolet irradiation. Since the forked fringes pattern also has chirality, only positive or negative topological charges can change the direction of the forked fringes. Therefore, it can be proved that the OAM sign carried by the outgoing light is reversed. At this time, the outgoing light is a vortex light with a topological charge number of +1.

[0049] When the ultraviolet light source is removed, the cholesteric liquid crystal 10 will gradually return to the left-handed cholesteric liquid crystal state.

[0050] It can be seen that the vortex light laser described in the present invention can directly emit vortex light, and the cholesteric liquid crystal in the liquid crystal structure will change the direction of circularly polarized light under the irradiation of ultraviolet light, thereby regulating the topological charge number of the vortex light. Compared with the traditional vortex light laser, the vortex light laser described in the present invention has high conversion efficiency, low preparation cost, fast preparation speed, vortex light of tunable orbital angular momentum, and can autonomously regulate the emitted light without introducing an external electric field. The preparation process is compatible with traditional semiconductor processes, small in size, and high in integration.

[0051] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0052] The above-mentioned embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application shall be subject to the attached claims.

Claims

1. A vortex light laser, characterized in that: include: Laser light source; A support structure disposed on the laser light source; as well as A liquid crystal structure disposed on the support structure, Wherein, the liquid crystal structure is configured to convert the linearly polarized light from the laser light source into circularly polarized light, and further convert the circularly polarized light into vortex light.

2. The vortex light laser according to claim 1, characterized in that: The liquid crystal structure includes a first glass substrate and a second glass substrate arranged on the supporting structure, a cholesteric liquid crystal arranged between the first glass substrate and the second glass substrate, and a spherulite arranged on the surface of the second glass substrate. The liquid crystal structure is configured to convert the linearly polarized light from the laser light source into circularly polarized light through the cholesteric liquid crystal, and further convert the circularly polarized light into angularly polarized vector vortex light by absorbing the radially polarized light beam of the circularly polarized light through the spherulite.

3. The vortex light laser according to claim 2, characterized in that: It further includes an ultraviolet light source arranged adjacent to the cholesteric liquid crystal, wherein when the ultraviolet light source is turned on, the handedness of the cholesteric liquid crystal changes from an initial state, thereby changing the handedness of the circularly polarized light; when the ultraviolet light source is turned off, the handedness of the cholesteric liquid crystal returns to the initial state.

4. The vortex light laser according to claim 2, characterized in that: The spherulites are in the shape of disks, and the molecules are arranged radially along the disks. The spherulites are made of the following materials: N1, N5-dihexylnaphthalene-1,5-diamine and N,N-dioctylnaphthalene diimide.

5. The vortex light laser according to claim 1, characterized in that: The laser light source comprises a lower DBR, an active region, an oxidation restriction layer, an upper DBR, and a passivation layer sequentially grown on a GaAs substrate; a first electrode sputtered on the back of the GaAs substrate and a second electrode sputtered on the passivation layer.

6. The vortex light laser according to claim 5, characterized in that: The laser light source includes a single-tube laser or an array laser, and the wavelength thereof includes 760nm to 808nm; the first electrode and the second electrode each use any one of Ti / Au, Ni / Au and Cr / Au material systems.

7. A method for preparing a vortex light laser according to any one of claims 1 to 6, characterized in that: The following steps are involved: S10. Preparing a laser light source; S20. Spin-coating a photoresist on the surface of the laser light source for photolithography and then developing to form a support structure, and exposing the mesa portion and the electrode portion of the laser light source to the outside world; S30. Preparing a liquid crystal structure; as well as S40. The liquid crystal structure is fixed on the support structure, Wherein, step S30 specifically includes the following steps: S32. The nematic liquid crystal, the chiral agent and the molecular motor are mixed uniformly in proportion and heated to a clearing point, the mixed liquid crystal at the clearing point is poured between the first glass substrate and the second glass substrate, the first glass substrate and the second glass substrate are sealed and slowly cooled to room temperature to form a cholesteric liquid crystal; and S33: smearing the spherulite material on the second glass substrate, covering the spherulite material with NaCl crystals, heating the spherulite material and then slowly cooling it to room temperature, so that the spherulite molecules complete self-assembly to form a disc-shaped structure, dissolving the NaCl layer with deionized water, and obtaining spherulites.

8. The method according to claim 7, characterized in that Step S10 specifically includes: epitaxially growing a lower DBR, an active area, an oxidation restriction layer and an upper DBR on a GaAs substrate in sequence by metal organic chemical vapor deposition or molecular beam epitaxy, photolithography and etching a table top, and performing lateral wet nitrogen oxidation around the table to form an oxidation restriction hole for limiting the light field and current; growing a passivation layer and photolithography and etching a light exit hole of the passivation layer, then sputtering a second electrode and photolithography and etching a light exit hole of the second electrode, and finally sputtering a first electrode on the back of the GaAs substrate; In step S20, photoresist is spin-coated on the surface of the second electrode as a whole, and the photoresist at the light exit hole of the passivation layer and the light exit hole of the second electrode is removed after photolithography and development, wherein the photoresist includes SU8 type photoresist.

9. The method according to claim 7, characterized in that Step S30 further includes the following steps before step S32: S31. performing parallel orientation between the first glass substrate and the second glass substrate through an orientation material and sealing the first glass substrate and the second glass substrate around, leaving only gaps on both sides for pouring the mixed liquid crystal at the clearing point, Wherein, in step S2, after the liquid crystal is poured, the gap is sealed; Wherein, the alignment material comprises polyimide and the sealing material comprises UV curing glue.

10. The method according to claim 7, characterized in that Step S40 specifically includes: applying UV light-curing glue on the support structure, placing the first glass substrate and the second glass substrate including the cholesteric liquid crystal and the spherulite on the support structure, irradiating UV light for fixation, and completing the preparation of the vortex light laser.

Images