Surface plasmon laser microcavity

Abstract

The surface plasmon laser microcavity comprises a semiconductor nanowire, a plurality of metal ellipsoids and a semiconductor substrate; wherein the plurality of metal ellipsoids are arranged in a one-dimensional array on the surface of the semiconductor substrate, each metal ellipsoid is half-buried in the semiconductor substrate, and the semiconductor nanowire covers the plurality of metal ellipsoids and coats a part of each metal ellipsoid; wherein electromagnetic waves of a specific frequency cannot propagate at both ends of the plurality of metal ellipsoids arranged in a one-dimensional array and oscillate in the middle of the plurality of metal ellipsoids arranged in a one-dimensional array. The surface plasmon laser can realize mode selection, has low loss, high quality factor and other comprehensive performance.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to the field of laser and micro-nano system technology, in particular to a surface plasmon laser microcavity. BACKGROUND

[0002] Lasers are widely used in information, communication, biology, military and other fields, and play a crucial role in improving people's lives. Among them, micro-nano lasers play a very key role in optical communication, laser radar, photonic integrated chips and other aspects. Micro-nano lasers are likely to make further applications in artificial intelligence, sensing technology, Internet of Things and other aspects. These new requirements have put forward new requirements for the development of micro-nano lasers, including small size, high precision, fast response, low cost, low loss and easy control.

[0003] The development of lasers has a trend of miniaturization. Since the advent of lasers, the size of lasers has become smaller and smaller, from meters to nanometers. The research of traditional photonic mode lasers is getting closer to the diffraction limit. In order to break through the limit of the diffraction limit, surface plasmon lasers emerge as the times require. Surface plasmons are quasi-particles generated by the coupling of electromagnetic waves and the collective oscillation of electrons on the surface of the metal. Due to its relatively high photon density, it can break through the diffraction limit of the mode size.

[0004] At present, various structures of surface plasmon lasers have been realized. Among them, the nanowire structure has natural microcavity characteristics, and the nanowire composed of gain medium has been widely used in laser preparation. However, due to the structural characteristics of the nanowire microcavity, the laser radiation loss is large, the quality factor is low, which seriously affects the performance of the laser. SUMMARY

[0005] In view of the problems of the prior art, the present disclosure provides a surface plasmon laser microcavity to solve the problems of large radiation loss and low quality factor of the existing semiconductor-metal type nanowire surface plasmon laser.

[0006] The present disclosure provides a surface plasmon laser microcavity, comprising: a semiconductor nanowire, a plurality of metal ellipsoids and a semiconductor substrate; wherein the plurality of metal ellipsoids are arranged in a one-dimensional array form on the surface of the semiconductor substrate, each metal ellipsoid is half-buried in the semiconductor substrate, and the semiconductor nanowire covers the plurality of metal ellipsoids and coats part of each metal ellipsoid; wherein electromagnetic waves of a specific frequency cannot propagate at both ends of the plurality of metal ellipsoids arranged in a one-dimensional array form, and oscillate in the middle of the plurality of metal ellipsoids arranged in a one-dimensional array form.

[0007] According to an embodiment of the present disclosure, the length of the short axis of the single metal ellipsoid is equal to half the distance between the two focal points, and the lengths of the short axes of the plurality of metal ellipsoids are equal; along the one-dimensional array arrangement direction, the lengths of the long axes of the plurality of metal ellipsoids gradually increase first and then gradually decrease, and the lengths of the long axes of the metal ellipsoids at both ends are the smallest, and the length of the long axis of the metal ellipsoid at the middle position is the largest.

[0008] According to an embodiment of the present disclosure, the length of the short axis of the metal ellipsoid is 60-120 nm; the length of the long axis of the metal ellipsoid at the middle position is 120-300 nm; and the length of the long axis of the metal ellipsoid at both ends is 60-120 nm.

[0009] According to an embodiment of the present disclosure, the number of the plurality of metal ellipsoids is 10-30, and the spacing between adjacent metal ellipsoids is 150-250 nm.

[0010] According to an embodiment of the present disclosure, the metal crystal type of the metal ellipsoid is a single-crystal metal, and the single-crystal metal includes one of gold, silver, copper, aluminum, and nickel.

[0011] According to an embodiment of the present disclosure, the roughness of the single-crystal metal is as low as 0.8 nm.

[0012] According to an embodiment of the present disclosure, the semiconductor nanowire is in direct contact with the semiconductor substrate without a gap therebetween.

[0013] According to an embodiment of the present disclosure, the semiconductor nanowire is a long waveguide structure with a square cross section perpendicular to the semiconductor substrate, and the side length of the square is 100-140 nm.

[0014] According to an embodiment of the present disclosure, the length of the semiconductor nanowire is greater than the length of the plurality of metal ellipsoids arranged in the one-dimensional array, and the length of the semiconductor nanowire is 1500-7500 nm.

[0015] According to an embodiment of the present disclosure, the material of the semiconductor nanowire includes a hybrid organic-inorganic perovskite material or a semiconductor gain material.

[0016] The surface plasmon laser microcavity provided by the embodiment of the present disclosure has at least the following beneficial effects:

[0017] The microcavity is provided with a plurality of metal ellipsoids arranged in a one-dimensional array, and the semiconductor nanowire covers the plurality of metal ellipsoids and coats a part of each metal ellipsoid. Due to the energy band characteristics of the one-dimensional metal photonic crystal, electromagnetic waves of a specific frequency cannot propagate at both ends of the plurality of metal ellipsoids arranged in a one-dimensional array, and oscillate in the middle of the plurality of metal ellipsoids arranged in a one-dimensional array, thereby effectively reducing the radiation loss, improving the quality factor, and increasing by 5-7 times.

[0018] The microcavity can break the diffraction limit, and can better realize the miniaturization of the laser.

[0019] The microcavity can break the diffraction limit, and can better realize the miniaturization of the laser. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 A structure diagram of the microcavity of the metal ellipsoid one-dimensional array surface plasmon laser provided by the embodiment of the present disclosure is schematically shown.

[0021] Figure 2 A front view structure diagram of the microcavity of the metal ellipsoid one-dimensional array surface plasmon laser provided by the embodiment of the present disclosure is schematically shown.

[0022] Figure 3 A side view structure diagram of the microcavity of the metal ellipsoid one-dimensional array surface plasmon laser provided by the embodiment of the present disclosure is schematically shown.

[0023] Figure 4 A top view structure diagram of the microcavity of the metal ellipsoid one-dimensional array surface plasmon laser provided by the embodiment of the present disclosure is schematically shown.

[0024] Figure 5 A diagram of the electric field distribution and electric field lines of the microcavity of the metal ellipsoid one-dimensional array surface plasmon laser provided by the embodiment of the present disclosure is schematically shown.

[0025] Figure 6 A comparison diagram of the relative intensity of energy and wavelength in the microcavity of the surface plasmon laser microcavity and the nanowire laser microcavity of the conventional metal substrate respectively provided by the embodiment of the present disclosure is schematically shown. DETAILED DESCRIPTION

[0026] To make the objectives, technical solutions and advantages of the present disclosure clearer, the present disclosure is further described in detail below with reference to the embodiments and the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present disclosure, rather than all the embodiments. Based on the embodiments in the present disclosure, all other embodiments obtained by those skilled in the art without creative labor fall within the protection scope of the present disclosure.

[0027] The terms used herein are merely used to describe specific embodiments, and are not intended to limit the present disclosure. The terms "comprise", "contain" and the like used herein indicate the existence of the described features, steps, operations and / or components, but do not exclude the existence or addition of one or more other features, steps, operations or components.

[0028] In the present disclosure, unless specifically defined otherwise and limited in the specification, the terms "mount", "connect", "connection", "fixed", and the like, should be construed broadly and interchangeably to include fixed connections, detachable connections, or integral connections; mechanical connections, electrical connections, or communication connections; direct connections, or indirect connections via intermediate media; internal connections between elements, or interaction between external elements. The above terms should be understood by those skilled in the art according to the specific context in which they are used in the present disclosure.

[0029] In the description of the present disclosure, it should be understood that the terms "longitudinal", "length", "circumferential", "front", "back", "left", "right", "top", "bottom", "inner", "outer", and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present disclosure and simplifying the description, and do not indicate or imply that the subsystems or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present disclosure.

[0030] Throughout the drawings, the same elements are denoted by the same or similar reference numerals. When it may cause confusion in understanding the present disclosure, conventional structures or configurations will be omitted. Also, the shape, size, positional relationship of the components in the drawings do not reflect the true size, scale and actual positional relationship. In addition, in the claims, any reference symbols located between parentheses should not be construed as a limitation on the claims.

[0031] Similarly, in order to simplify the present disclosure and help understand one or more of the various disclosed aspects, in the above description of the exemplary embodiments of the present disclosure, various features of the present disclosure are sometimes grouped together in a single embodiment, figure or description thereof. The description of the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present disclosure. In the present description, the illustrative description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0032] In addition, the terms "first", "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly indicating the number of the technical features indicated. Therefore, the features defined with "first", "second" can explicitly or implicitly include one or more of the features. In the description of the present disclosure, the meaning of "multiple" is at least two, such as two, three, etc., unless otherwise specifically defined.

[0033] Figure 1 A structural diagram of the metal-ellipsoid one-dimensional array surface plasmon laser microcavity is shown schematically.

[0034] As shown in the figure, the surface plasmon laser microcavity includes a semiconductor nanowire 1, a plurality of metal ellipsoids 2, and a semiconductor substrate 3. Figure 1

[0035] The plurality of metal ellipsoids 2 are arranged in a one-dimensional array on the surface of the semiconductor substrate 3, each metal ellipsoid 2 is half-buried in the semiconductor substrate 3, and the semiconductor nanowire covers the plurality of metal ellipsoids and coats a portion of each metal ellipsoid.

[0036] Figure 2 A front view structural diagram of the metal-ellipsoid one-dimensional array surface plasmon laser microcavity is shown schematically.

[0037] Figure 3 A side view structural diagram of the metal-ellipsoid one-dimensional array surface plasmon laser microcavity is shown schematically.

[0038] Figure 4 A top view structural diagram of the metal-ellipsoid one-dimensional array surface plasmon laser microcavity is shown schematically.

[0039] As shown in the figure, in the embodiment of the present disclosure, the short axis length a of a single metal ellipsoid 2 is equal to one-half c of the distance between two focal points, and the short axis lengths a of the plurality of metal ellipsoids 2 are equal. Figures 2 to 4

[0040] Along the one-dimensional array arrangement direction, the long axis length b of the plurality of metal ellipsoids 2 presents a trend of gradually increasing first and then gradually decreasing, the array-arranged metal ellipsoids 2 have symmetry relative to the midpoint of the one-dimensional array, and the long axis length of the metal ellipsoids 2 at both ends is the smallest, denoted as b min , and the long axis length of the metal ellipsoids 2 at the middle position is the largest, denoted as b max .

[0041] Further, the short axis length a of the metal ellipsoid 2 is 60nm-120nm, the long axis length b max of the metal ellipsoid 2 at the middle position is 120nm-300nm, and the long axis length b min of the metal ellipsoid 2 at both ends is 60nm-120nm.

[0042] The number of the plurality of metal ellipsoids 2 is 10-30, and the spacing D between adjacent metal ellipsoids 2 is 150nm-250nm.

[0043] ​​In the embodiments of the present disclosure, the metal crystal type of the metal ellipsoid 2 is single-crystal metal, which can include one of gold, silver, copper, aluminum, and nickel. The single-crystal metal surface has no grain boundary, high smoothness, and low roughness of 0.8 nm, effectively reducing the loss.

[0044] In the embodiments of the present disclosure, the semiconductor nanowire 1 covers and wraps each metal ellipsoid 2, and there is no gap between the semiconductor nanowire 1 and the semiconductor substrate 3. The semiconductor nanowire 1 cannot completely cover the metal ellipsoid 2, and each metal ellipsoid 2 has a part in contact with air.

[0045] Further, the semiconductor nanowire 1 can be a long waveguide structure with a square cross section perpendicular to the semiconductor substrate 3. Preferably, the side length W of the square is 100 nm to 140 nm.

[0046] The length L of the semiconductor nanowire 1 is greater than the length of the plurality of metal ellipsoids 2 arranged in a one-dimensional array, and the length of the semiconductor nanowire 1 is 1500 nm to 7500 nm.

[0047] The material of the semiconductor nanowire 1 includes a hybrid organic-inorganic perovskite material or a semiconductor gain material, which can be, for example, gallium arsenide, a laser crystal, or the like. The semiconductor substrate 3 can use SiO2, or other commonly used dielectric substrate materials.

[0048] According to the embodiments of the present disclosure, according to the related principles of photonic bandgap structure, the size of the metal ellipsoid 2 and the spacing of the array determine the mode frequency supported by the metal photonic crystal. Electromagnetic waves with a frequency within the bandgap range of the metal photonic crystal energy band cannot propagate in the metal photonic crystal. By adjusting the size of the metal ellipsoid, electromagnetic waves with a specific frequency cannot propagate at both ends of the one-dimensional array, but can only oscillate in the middle of the array, so that the mode distribution is mainly located in the middle of the array. Using this principle, the laser microcavity structure proposed in the present disclosure can effectively reduce the radiation loss and improve the Q value.

[0049] According to an embodiment of the present disclosure, the surface plasmonic laser microcavity uses a semiconductor nanowire as a gain medium and is covered on a metal ellipsoid array. The size of the semiconductor nanowire also affects the mode supported by the microcavity, and therefore needs to be designed for the wavelength range in which the laser works, specifically, the laser works in the visible and infrared bands, the laser pumping mode is optical pumping, and the laser microcavity is surrounded by air. In the working of the laser, the semiconductor nanowire as the gain medium generates excitons under the action of pump light, the excitons transfer energy to the plasmonic mode, the plasmonic mode oscillates in the laser microcavity, and lasing is achieved. The size-graduated metal ellipsoid array structure proposed in the present disclosure effectively reduces the radiation loss and improves the Q value. The structure can control the mode frequency supported by the laser microcavity through size design, achieve mode selection, and thus realize single-mode lasing. At the same time, the surface plasmonic laser proposed in the present disclosure also has a mode volume that breaks the diffraction limit, has a fast response speed, a low excitation threshold, and other advantages, which is of great significance for promoting the development of nanoscale optics and the integration of high-performance optoelectronic elements.

[0050] To further illustrate the characteristics of the surface plasmonic laser microcavity provided by the present disclosure, specific experimental data are listed below.

[0051] For example, the laser works in the wavelength range of 500 nm-600 nm. The material of the semiconductor nanowire 1 is CH3NH3PbBr3 perovskite material, which has a high exciton binding energy and can provide a large gain. In the implementation process, the refractive index of the perovskite material at 550 nm is 2.2, the semiconductor nanowire is exposed to air, the refractive index of air is 1, and the semiconductor nanowire 1 directly contacts the one-dimensional array arranged metal ellipsoid 2 to generate surface plasmons. The overall shape of the semiconductor nanowire 1 is a cuboid, the length of which is 2.5 microns, and the cross section is a square with a side length of 130 nm.

[0052] Since silver has a relatively low metal loss in the wavelength range of 500 nm-600 nm compared with other common metals, the metal ellipsoid 2 is made of single-crystal silver material. The values of a and c of the metal ellipsoid are both 70 nm. The metal ellipsoids are arranged in a one-dimensional array, and the value of b of the metal ellipsoid gradually changes along the array, being the smallest at both ends of the array and taking a value of 200 nm, and being the largest at the midpoint of the array and taking a value of 250 nm. The total number of the array arranged metal ellipsoids 2 is 12.

[0053] Figure 5 The electric field distribution and electric field line diagram of the metal ellipsoid one-dimensional array surface plasmonic laser microcavity provided by the embodiment of the present disclosure are schematically shown.

[0054] Figure 6A comparison chart of the relative intensity of energy in the microcavity and the wavelength is shown in the surface plasmonic laser microcavity provided by the embodiment of the present disclosure and the nanowire laser microcavity of the traditional metal substrate.

[0055] As shown in Figure 5 and Figure 6 The mode frequency supported by the surface plasmonic laser microcavity is 548nm-553nm, compared with the traditional structure, that is, the structure of placing semiconductor nanowires on the metal substrate, the Q value of the structure is effectively improved by 6 times, and has better frequency selectivity, further promoting the research of surface plasmonic laser.

[0056] In summary, the surface plasmonic laser microcavity provided by the embodiment of the present disclosure realizes the basic function of the plasmonic laser in the case that the physical size and the mode size are both smaller than half the wavelength by means of the plasmonic characteristics. By utilizing the energy band characteristics of the photonic bandgap structure, the electromagnetic field of the supported mode is mainly distributed in the middle of the array by designing the size change of the metal ellipsoid array, and the electromagnetic wave of a specific wavelength cannot propagate at both ends of the metal ellipsoid array. The size of the metal ellipsoid and the nanometer is designed to match the wavelength of 500nm-600nm. The radiation loss of the surface plasmonic laser microcavity is significantly reduced, so that the quality factor of the resonant cavity is greatly improved. The surface plasmonic laser microcavity with effectively improved quality factor has the advantages of miniaturization and high quality factor, and has broad application prospects.

[0057] The above specific embodiments further illustrate the purpose, technical solutions and beneficial effects of the present disclosure. It should be understood that the above description is only a specific embodiment of the present disclosure and is not intended to limit the present disclosure. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present disclosure shall be included in the protection scope of the present disclosure.

Claims

1. A surface plasmonic laser microcavity, characterized in that, include: Semiconductor nanowires (1), multiple metal ellipsoids (2) and semiconductor substrate (3); The plurality of metal ellipsoids (2) are arranged in a one-dimensional array on the surface of the semiconductor substrate (3), each metal ellipsoid (2) is partially embedded in the semiconductor substrate (3), and the semiconductor nanowire (1) covers the plurality of metal ellipsoids (2) and encapsulates a portion of each metal ellipsoid (2). Among them, electromagnetic waves of a specific frequency cannot propagate at both ends of the plurality of metal ellipsoids (2) arranged in a one-dimensional array, and oscillate in the middle of the plurality of metal ellipsoids (2) arranged in a one-dimensional array.

2. The surface plasmon laser microcavity according to claim 1, characterized in that, The minor axis length of a single metal ellipsoid (2) is equal to half the distance between its two foci, and the minor axis lengths of multiple metal ellipsoids (2) are equal. Along the one-dimensional array arrangement direction, the major axis length of multiple metal ellipsoids (2) shows a trend of first gradually increasing and then gradually decreasing. The major axis length of the metal ellipsoids (2) at both ends is the smallest, and the major axis length of the metal ellipsoid (2) in the middle position is the largest.

3. The surface plasmon laser microcavity according to claim 2, characterized in that, The minor axis of the metal ellipsoid (2) is 60nm~120nm; the major axis of the metal ellipsoid (2) in the middle position is 120nm~300nm; and the major axis of the metal ellipsoids (2) at both ends is 60nm~120nm.

4. The surface plasmon laser microcavity according to claim 1, characterized in that, The number of the plurality of metal ellipsoids (2) is 10 to 30, and the spacing between adjacent metal ellipsoids (2) is 150 nm to 250 nm.

5. The surface plasmon laser microcavity according to claim 1, characterized in that, The metal ellipsoid (2) is a single crystal metal, which includes one of gold, silver, copper, aluminum and nickel.

6. The surface plasmon laser microcavity according to claim 5, characterized in that, The roughness of the single-crystal metal is as low as 0.8 nm.

7. The surface plasmon laser microcavity according to claim 1, characterized in that, The semiconductor nanowire (1) is in direct contact with the semiconductor substrate (3) without any gap between them.

8. The surface plasmon laser microcavity according to claim 1, characterized in that, The semiconductor nanowire (1) is a long waveguide structure with a square cross-section perpendicular to the semiconductor substrate (3), and the side length of the square is 100nm~140nm.

9. The surface plasmon laser microcavity according to claim 1, characterized in that, The length of the semiconductor nanowire (1) is greater than the length of the multiple metal ellipsoids (2) arranged in the one-dimensional array, and the length of the semiconductor nanowire (1) is 1500nm~7500nm.

10. The surface plasmon laser microcavity according to claim 1, characterized in that, The semiconductor nanowire (1) is made of a semiconductor gain material.

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