High-efficiency large-bottom-occupancy trapezoidal groove grating applied to OCT

Abstract

The application discloses a high-efficiency large-bottom-occupying-wide trapezoidal groove grating applied to OCT, and relates to the technical field of gratings. The period of the specific grating is 833.33 nm; the side wall inclination angle is 85 degrees; the grating bottom-occupying-wide ratio is 1; the grating depth is A, 2550 nm >= A >= 2450 nm; the central wavelength is 840 nm; and the incidence angle is 30.26 degrees. The application aims at improving the diffraction efficiency of the OCT grating.

Description

Technical Field

[0001] This invention relates to the field of grating technology, and in particular to a high-efficiency trapezoidal slot grating with a large bottom area for use in OCT. Background Technology

[0002] Spectral imaging is a widely used technique in optics and optoelectronics to analyze and acquire the spectral information of objects. It combines the features of spectral analysis and image acquisition, enabling the simultaneous acquisition of spectral information at different wavelengths and spatially resolved images. In spectral imaging, gratings, through their periodic structure, disperse light to different angles or positions for spectral analysis and imaging.

[0003] Surface relief gratings, as the most commonly used high-diffraction-efficiency transmission gratings, are currently mainly applied in the field of high-energy lasers. The requirements for high diffraction efficiency can be met by adjusting the bottom octane width, groove depth, and sidewall mask tilt angle. Furthermore, surface relief gratings have a wide spectral applicability range and are currently manufactured using mature technology.

[0004] Currently, the imaging dispersive elements used in OCT systems on the market can achieve efficiencies of TE > 83% and TM > 83% at a center wavelength of 840nm, indicating that there is still room for improvement in efficiency.

[0005] Therefore, how to further improve the diffraction efficiency of OCT gratings has become an urgent technical problem to be solved. Summary of the Invention

[0006] The main objective of this invention is to provide a high-efficiency trapezoidal groove grating with a large bottom area for use in OCT, aiming to further improve the diffraction efficiency of OCT gratings.

[0007] To achieve the above objectives, this invention proposes a high-efficiency trapezoidal slot grating with a large bottom area ratio for use in OCT. The grating has a period of 833.33 nm, a sidewall tilt angle of 85°, a bottom area ratio of 1, a grating depth of A, where 2550 nm ≥ A ≥ 2450 nm, a center wavelength of 840 nm, and an incident angle of 30.26°.

[0008] In one embodiment of this application, the grating depth is 2550nm.

[0009] In one embodiment of this application, the grating is made of quartz.

[0010] In one embodiment of this application, the line density of the grating is 1200 lines.

[0011] The above technical solution utilizes a large bottom-area trapezoidal groove, which expands the bottom grating's aspect ratio compared to the traditional trapezoidal groove. This results in a higher aspect ratio and greater etching tolerance, reducing the complexity of the manufacturing process. The trapezoidal groove grating with a bottom grating aspect ratio of 1 exhibits a diffraction efficiency of 96% under both electric field perpendicular and parallel-field vibrations, a center wavelength efficiency of 99%, and a polarization sensitivity of 0.012%. It is insensitive to the polarization state of the incident light and possesses wide bandwidth and high dispersion. Attached Figure Description

[0012] The present invention will now be described in detail with reference to specific embodiments and accompanying drawings, wherein:

[0013] Figure 1 This is a simulation construction model of the first embodiment of the present invention;

[0014] Figure 2 This is a schematic diagram of the geometric structure of the present invention;

[0015] Figure 3 This is a schematic diagram showing the effect of different bottom width-to-width ratios and slot depths on the vibration efficiency of the electric field perpendicular to the incident plane.

[0016] Figure 4 This is a schematic diagram showing the effect of different bottom width-to-width ratios and slot depths on the vibration efficiency of the electric field parallel to the incident plane.

[0017] Figure 5 This is the effect of different bottom fill ratios on the grating diffraction efficiency when the grating groove depth is 2000nm;

[0018] Figure 6 These are simulation results when the grating groove depth is 2000nm and the bottom aspect ratio is 0.9;

[0019] Figure 7 These are simulation results when the grating depth is 2250nm and the bottom aspect ratio is 0.93;

[0020] Figure 8 These are simulation results when the grating depth is 2400nm and the bottom aspect ratio is 0.96;

[0021] Figure 9 These are simulation results when the grating depth is 2500nm and the bottom aspect ratio is 0.99;

[0022] Figure 10 These are simulation results when the grating depth is 2450nm and the bottom aspect ratio is 1;

[0023] Figure 11 These are simulation results when the grating depth is 2500nm and the bottom aspect ratio is 1;

[0024] Figure 12 These are simulation results when the grating depth is 2550nm and the bottom aspect ratio is 1;

[0025] Figure 13 These are simulation results for the 700-1000nm range when the grating depth is 2450nm and the bottom aspect ratio is 1.

[0026] Figure 14 These are simulation results for the 700-1000nm range when the grating depth is 2500nm and the bottom aspect ratio is 1.

[0027] Figure 15 These are simulation results for the 700-1000nm range when the grating depth is 2550nm and the bottom aspect ratio is 1. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the following specific embodiments are only used to explain the invention and do not constitute a limitation thereof.

[0029] like Figures 1 to 15 As shown, in order to achieve the above objectives, this invention proposes a high-efficiency trapezoidal slot grating with a large bottom area ratio for OCT. The grating has a period of 833.33 nm, a sidewall tilt angle of 85°, a bottom area ratio of 1, a grating depth of A, where 2550 nm ≥ A ≥ 2450 nm, a center wavelength of 840 nm, and an incident angle of 30.26°.

[0030] Specifically, this invention proposes a high-efficiency trapezoidal slot grating with a large bottom area ratio for use in OCT. The grating has a period of 833.33 nm, an incident angle of 30.26°, a sidewall tilt angle of 85°, and a bottom area ratio of 1.

[0031] If the sidewall inclination angle remains unchanged, by changing the bottom width and groove depth, we can obtain the changes in diffraction efficiency when the electric field vibrates perpendicular to the incident plane and when the electric field vibrates parallel to the incident plane.

[0032] With a groove depth of 2000 nm and a constant sidewall inclination angle, when the bottom width ratio is greater than 0.9, the diffraction efficiency of electric field vibration perpendicular to the incident plane and electric field vibration parallel to the incident plane are both >84%. The polarization sensitivity shows an overall trend of gradually decreasing, and the process tolerance is large, making it easier to operate in practice.

[0033] As the groove depth gradually increases while the sidewall inclination angle remains constant, the diffraction efficiency changes as the bottom width increases from 0.9.

[0034] When the groove depth is 2000 nm and the bottom width-to-width ratio is 0.9, the vibration efficiency is 92.5% when the electric field is parallel to the incident plane, 94.7% when the electric field is perpendicular to the incident plane, and the polarization sensitivity is 0.045%.

[0035] With a groove depth of 2250 nm and a bottom width-to-width ratio of 0.93, the vibration efficiency is 94.7% when the electric field is parallel to the incident plane, 91.2% when the electric field is perpendicular to the incident plane, and the polarization sensitivity is 0.055%.

[0036] When the groove depth is 2400 nm and the bottom width-to-width ratio is 0.96, the vibration efficiency is 95.1% when the electric field is parallel to the incident plane, 90% when the electric field is perpendicular to the incident plane, and the polarization sensitivity is 0.062%.

[0037] With a groove depth of 2500 nm and a bottom width-to-width ratio of 0.99, the vibration efficiency is 95.7% when the electric field is parallel to the incident plane, 96% when the electric field is perpendicular to the incident plane, and the polarization sensitivity is 0.017%.

[0038] With a groove depth of 2550 nm and a bottom width-to-width ratio of 1, the vibration efficiency is 95.9% when the electric field is parallel to the incident plane, 96% when the electric field is perpendicular to the incident plane, and the polarization sensitivity is 0.012%.

[0039] When the grating groove depth is 2450 nm and the operating wavelength is between 700 nm and 790 nm or between 890 nm and 1000 nm, the diffraction efficiency is: electric field perpendicular to the incident plane vibration (TE) is 87%; electric field parallel to the incident plane vibration (TM) is 71%; and polarization sensitivity is 0.19%.

[0040] When the grating groove depth is 2500nm and the operating wavelength is between 700nm and 790nm or between 890nm and 1000nm, the diffraction efficiency is: electric field perpendicular to the incident plane vibration (TE) equals 87%, electric field parallel to the incident plane vibration (TM) equals 72%, and polarization sensitivity equals 0.18%.

[0041] When the grating groove depth is 2550nm and the operating wavelength is between 700nm and 790nm or between 890nm and 1000nm, the diffraction efficiency is: electric field perpendicular to the incident plane vibration (TE) equals 85%, electric field parallel to the incident plane vibration (TM) equals 75%, and polarization sensitivity equals 0.16%.

[0042] When the grating groove depth is 2450nm, the top ridge width is 413.5nm, and the bottom part-width ratio of the top grating is 0.496, the diffraction efficiency in the working band at 790nm is: electric field perpendicular to the incident plane vibration (TE) equals 95.5%, and electric field parallel to the incident plane vibration (TM) equals 97.2%.

[0043] When the grating groove depth is 2450nm, the top ridge width is 413.5nm, and the bottom part-width ratio of the top grating is 0.496, the diffraction efficiency at the center wavelength of 840nm is: electric field perpendicular to the incident plane vibration (TE) equals 96.5%, and electric field parallel to the incident plane vibration (TM) equals 98.2%.

[0044] When the grating groove depth is 2450nm, the top ridge width is 413.5nm, the bottom part-width ratio of the top grating is 0.496, the diffraction efficiency in the working band at 890nm is: electric field perpendicular to the incident plane vibration (TE) equals 94.5%, electric field parallel to the incident plane vibration (TM) equals 93.5%, and polarization sensitivity equals 0.017%.

[0045] When the grating groove depth is 2500nm, the top ridge width is 395.9nm, and the bottom part-width ratio of the top grating is 0.475, the diffraction efficiency in the working band at 790nm is: 96.2% for electric field perpendicular to the incident plane vibration (TE) and 96.8% for electric field parallel to the incident plane vibration (TM).

[0046] When the grating groove depth is 2500nm, the top ridge width is 395.9nm, and the bottom part-width ratio of the top grating is 0.475, the diffraction efficiency at the center wavelength of 840nm is: 97.3% for electric field perpendicular to the incident plane vibration (TE) and 98.9% for electric field parallel to the incident plane vibration (TM).

[0047] When the grating groove depth is 2500nm, the top ridge width is 395.9nm, the bottom part-width ratio of the top grating is 0.475, the diffraction efficiency in the working band at 890nm is: electric field perpendicular to the incident plane vibration (TE) equals 95.7%, electric field parallel to the incident plane vibration (TM) equals 94.9%, and polarization sensitivity equals 0.016%.

[0048] When the grating groove depth is 2550nm, the top ridge width is 387.1nm, and the bottom part-width ratio of the top grating is 0.465, the diffraction efficiency in the working band at 790nm is: electric field perpendicular to the incident plane vibration (TE) equals 96.1%, electric field parallel to the incident plane vibration (TM) equals 96%.

[0049] When the grating groove depth is 2550nm, the top ridge width is 387.1nm, and the bottom part-width ratio of the top grating is 0.465, the diffraction efficiency at the center wavelength of 840nm is: 97.7% for electric field vibration perpendicular to the incident plane (TE) and 99.9% for electric field vibration parallel to the incident plane (TM).

[0050] When the grating groove depth is 2550nm, the top ridge width is 387.1nm, the bottom part-width ratio of the top grating is 0.465, the diffraction efficiency in the working band at 890nm is: electric field perpendicular to the incident plane vibration (TE) equals 96.5%, electric field parallel to the incident plane vibration (TM) equals 96%, and polarization sensitivity equals 0.012%.

[0051] The above technical solution utilizes a large bottom-area trapezoidal groove, which expands the bottom grating's aspect ratio compared to the traditional trapezoidal groove. This results in a higher aspect ratio and greater etching tolerance, reducing the complexity of the manufacturing process. The trapezoidal groove grating with a bottom grating aspect ratio of 1 exhibits a diffraction efficiency of 96% under both electric field perpendicular and parallel-field vibrations, a center wavelength efficiency of 99%, and a polarization sensitivity of 0.012%. It is insensitive to the polarization state of the incident light and possesses advantages such as wide bandwidth and high dispersion.

[0052] In one embodiment of this application, the grating depth is 2550nm.

[0053] Specifically, the grating has a period of 833.33 nm, a center wavelength of 840 nm, an incident angle of 30.26°, a sidewall tilt angle of 85°, a bottom aspect ratio of 1, and a grating depth of 2550 nm.

[0054] By adopting the above technical solution and setting the grating depth to 2550nm, it is easy to process and at the same time, the diffraction effect of the OCT grating can be improved.

[0055] In one embodiment of this application, the grating is made of quartz.

[0056] Using quartz material avoids the problem of difficult material selection and reduces production costs.

[0057] In one embodiment of this application, the line density of the grating is 1200 lines.

[0058] Using the above technical solution, a grating with a line density of 1200 can provide higher resolution. Higher line density means more lines per unit length, enabling more accurate separation of light signals of different wavelengths.

[0059] The above description is merely a preferred embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural transformations made using the contents of the present invention's specification and drawings under the inventive concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A high-efficiency trapezoidal slot grating with a large bottom area for use in OCT, characterized in that, The grating has a period of 833.33 nm, a sidewall tilt angle of 85°, a bottom aspect ratio of 1, a grating depth of 2550 nm, a center wavelength of 840 nm, and an incident angle of 30.26°. When the working wavelength is 790 nm, the diffraction efficiency of TE polarized light is 96.1%, and that of TM polarized light is 96%. When the working wavelength is 840 nm, the diffraction efficiency of TE polarized light is 97.7%, and that of TM polarized light is 99.9%. When the working wavelength is 890 nm, the diffraction efficiency of TE polarized light is 96.5%, and that of TM polarized light is 96%.

2. The high-efficiency large bottom area trapezoidal slot grating for OCT as described in claim 1, characterized in that, The grating is made of quartz.

3. The high-efficiency large bottom area trapezoidal slot grating for OCT as described in claim 1, characterized in that, The grating has a line density of 1200 lines.

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