[0028] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.
[0029] In the following description, many specific details are explained in order to fully understand the present invention. However, the present invention can be implemented in many other ways different from those described herein, and those skilled in the art can make similar extensions without violating the connotation of the present invention. Therefore, the present invention is not limited by the specific implementation disclosed below.
[0030] See figure 1 , The method for manufacturing a surface plasmon lens of the embodiment of the present invention includes the following steps:
[0031] S1: Provide base;
[0032] S2: forming a metal film layer with a certain thickness on the upper surface of the substrate;
[0033] S3: etching the upper surface of the metal film layer to form a main annular groove;
[0034] S4: The bottom surface of the main annular groove is etched to form a secondary annular groove, the secondary annular groove is formed along the circumference of the primary annular groove, and the center of the primary annular groove and the secondary annular groove are connected Vertical to the upper surface of the metal film layer, the outer diameter of the main annular groove is greater than the outer diameter of the secondary annular groove, and the bottom end surface of the secondary annular groove is higher than the lower surface of the metal film layer.
[0035] See image 3 A specific embodiment is used to describe the specific process of the manufacturing method of the present invention. First, provide a substrate 3, such as a quartz substrate. Preferably, the substrate 3 can be cleaned first. The cleaning method can be, for example, an ultrasonic cleaning machine. Then, a metal silver film is coated on the quartz substrate with a coating machine. The thickness is preferably greater than 300 nm; then, a focused ion beam is used to etch a main annular groove 4 on the metallic silver film, the groove shape is rectangular, the groove inner diameter is preferably 1345 nm, the groove width w1 can be 310 nm, and the groove depth h1 can be 110 nm; Finally, a concentric secondary annular groove 5 with the same inner diameter is etched on the bottom of the main annular groove 4 with a focused ion beam. The groove shape is rectangular, the groove width w2 can be 155 nm, and the groove depth h2 can be 20 nm.
[0036] See figure 2 with image 3 The surface plasmon lens fabricated in this embodiment includes a substrate 3 and a metal film layer 2. The shape of the base 3 is preferably a sheet shape, directly in the shape of a lens. Of course, the shape of the base 3 may also be other shapes. The base 3 is, for example, a quartz substrate or a substrate of other transparent base materials. The metal film layer 2 can be any metal substrate used to make a surface plasmon lens. In a preferred embodiment, the metal film layer 2 is a metal silver film, which has stronger wave conductivity, lower loss, and better transparency.
[0037] See image 3 The metal film layer 2 is formed on the upper surface of the substrate 3. The metal film layer 2 can completely cover the upper surface of the substrate 3, or it can only cover the area that does not affect the operation of the lens. The metal film layer 2 has a certain thickness, so that the main annular groove 4 and the secondary annular groove 5 can be formed on the metal film layer 2. The main annular groove 4 is formed on the upper surface of the metal film layer 2, in other words, an annular groove is opened downward from the upper surface of the metal film layer 2 to form the main annular groove 4. The secondary annular groove 5 is formed at the bottom of the main annular groove 4, and the secondary annular groove 5 is opened along the circumference of the main annular groove 4. In other words, an annular groove is formed downward from the bottom of the main annular groove 4 to the circumference of the groove Slot to form a secondary annular groove 5.
[0038] The ring center line of the main ring groove 4 and the auxiliary ring groove 5 is perpendicular to the upper surface of the metal film layer 2, and the axis surrounded by the main ring groove 4 and the auxiliary ring groove 5 is the same axis, see figure 2 , When viewed from above the metal film layer 2, the main annular groove 4 and the secondary annular groove 5 are concentric. Continue to see image 3 , The notch end surface of the main annular groove 4 is coplanar with the upper surface of the metal film layer 2, the groove bottom surface of the main annular groove 4 is coplanar with the notch end surface of the secondary annular groove 5, and the groove bottom surface of the secondary annular groove 5 is higher than the metal film The bottom surface of layer 2. The outer diameter of the main annular groove 4 is larger than the outer diameter of the secondary annular groove 5. When the incident light 1 is irradiated from above the metal film layer 2 to the ring of the main annular groove 4, the surface plasmon is excited under the action of the main annular groove 4, and the surface plasma is all directed to the ring under the action of the sub-annular groove 5. Center propagation, where in-phase interference produces a surface plasmon focus, which does not or rarely propagate out of the ring, which improves the lens excitation efficiency.
[0039] See image 3 The inner diameter of the main annular groove 4 is approximately equal to the inner diameter of the secondary annular groove 5. Preferably, the inner diameters of the primary annular groove 4 and the secondary annular groove 5 are equal, that is, the inner annular walls of the two can be joined to the same annular wall. However, it can be understood that in the actual manufacturing process, the groove shapes of the main annular groove 4 and the secondary annular groove 5 will have a certain degree of deviation, and these deviations are allowed under the conditions of the normal working range of the lens. Preferably, the inner diameters of the main annular groove 4 and the secondary annular groove 5 are 1345 nm. At this inner diameter, the surface plasmon excitation effect is strong and the lens efficiency is higher.
[0040] The groove width of the main annular groove 4 is greater than the groove width of the secondary annular groove 5, and the groove depth of the main annular groove 4 is greater than the groove depth of the secondary annular groove 5. The cross-sectional groove shapes of the main annular groove 4 and the secondary annular groove 5 are rectangular. The groove width of the main annular groove 4 is 310 nm, and the groove depth is 110 nm. The groove width of the secondary annular groove 5 is 155 nm, and the groove depth is 20 nm.
[0041] The thickness of the metal film layer 2 is preferably greater than 300nm, so that the main annular groove 4 and the secondary annular groove 5 are both formed inside the metal film layer 2, and the bottom end surface of the secondary annular groove 5 to the lower surface of the metal film layer 2 (that is, near the base There is also a certain distance between the surface and the metal film layer 2 should not be too thick.
[0042] Figure 4 It is a surface plasmon lens focus comparison diagram. The solid line represents the focus intensity distribution of the surface plasmon lens with sub-annular groove 5 according to the embodiment of the present invention, and the dotted line represents the surface plasmon lens without sub-annular groove 5 (ie The current existing surface plasmon lens) focus intensity distribution. When other parameters are the same, the surface plasmon excited by the surface plasmon lens of the present invention basically propagates toward the center of the ring, and the intensity at the focal point is twice that of the surface plasmon lens without the sub-annular groove 5, while the surface plasmon lens The complexity of the structure has not increased, the volume has not increased, and the manufacturing method is simple, which is conducive to miniaturization and integration.
[0043] In one embodiment, the working wave of the surface plasmon lens (that is, the incident wave 1) is radially polarized light, and the wavelength of the working wave is selectable between 600 nm and 670 nm. Preferably, the wavelength of the working wave is 633 nm.
[0044] Figure 5 It is the relationship between the incident light wavelength and efficiency of the surface plasmon lens formed by the manufacturing method of the present invention, the solid line η i Indicates the efficiency of the surface plasma excited to the center of the ring, the dotted line η o It represents the efficiency of the surface plasmon excited outside the ring. The incident light wavelength is within a relatively wide wavelength range near 633 nm. The surface plasmon lens of the present invention has a higher plasma excitation efficiency.
[0045] Although the present invention is disclosed as above in preferred embodiments, it is not used to limit the claims. Any person skilled in the art can make possible changes and modifications without departing from the spirit and scope of the present invention. Therefore, the present invention The scope of protection shall be subject to the scope defined by the claims of the present invention.
