CN117406328A - Holographic diffraction grating of middle-long wave infrared band and manufacturing method thereof - Google Patents
Holographic diffraction grating of middle-long wave infrared band and manufacturing method thereof Download PDFInfo
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- CN117406328A CN117406328A CN202311626430.XA CN202311626430A CN117406328A CN 117406328 A CN117406328 A CN 117406328A CN 202311626430 A CN202311626430 A CN 202311626430A CN 117406328 A CN117406328 A CN 117406328A
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- 238000004519 manufacturing process Methods 0.000 title description 6
- 239000000758 substrate Substances 0.000 claims abstract description 22
- 229920002120 photoresistant polymer Polymers 0.000 claims description 16
- 229910052751 metal Inorganic materials 0.000 claims description 11
- 239000002184 metal Substances 0.000 claims description 11
- 238000000034 method Methods 0.000 claims description 8
- 238000000151 deposition Methods 0.000 claims description 6
- 239000000463 material Substances 0.000 claims description 6
- 239000000956 alloy Substances 0.000 claims description 3
- 229910045601 alloy Inorganic materials 0.000 claims description 3
- 238000005530 etching Methods 0.000 claims description 3
- 239000007769 metal material Substances 0.000 claims description 3
- 239000000919 ceramic Substances 0.000 claims description 2
- 239000011521 glass Substances 0.000 claims description 2
- 238000001228 spectrum Methods 0.000 abstract description 14
- 230000006835 compression Effects 0.000 abstract description 5
- 238000007906 compression Methods 0.000 abstract description 5
- 238000011160 research Methods 0.000 abstract description 2
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 9
- 230000010287 polarization Effects 0.000 description 6
- 238000004528 spin coating Methods 0.000 description 5
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 4
- 238000007747 plating Methods 0.000 description 4
- 238000004544 sputter deposition Methods 0.000 description 4
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 3
- 239000011248 coating agent Substances 0.000 description 3
- 238000000576 coating method Methods 0.000 description 3
- 238000010586 diagram Methods 0.000 description 3
- 238000005516 engineering process Methods 0.000 description 3
- 239000005350 fused silica glass Substances 0.000 description 3
- PCHJSUWPFVWCPO-UHFFFAOYSA-N gold Chemical compound [Au] PCHJSUWPFVWCPO-UHFFFAOYSA-N 0.000 description 3
- 239000010931 gold Substances 0.000 description 3
- 229910052737 gold Inorganic materials 0.000 description 3
- 238000001755 magnetron sputter deposition Methods 0.000 description 3
- 230000003321 amplification Effects 0.000 description 2
- 229910052786 argon Inorganic materials 0.000 description 2
- 238000011161 development Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 238000005259 measurement Methods 0.000 description 2
- 238000003199 nucleic acid amplification method Methods 0.000 description 2
- 230000003111 delayed effect Effects 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 229910052732 germanium Inorganic materials 0.000 description 1
- GNPVGFCGXDBREM-UHFFFAOYSA-N germanium atom Chemical compound [Ge] GNPVGFCGXDBREM-UHFFFAOYSA-N 0.000 description 1
- 238000002329 infrared spectrum Methods 0.000 description 1
- 238000000025 interference lithography Methods 0.000 description 1
- 238000012544 monitoring process Methods 0.000 description 1
- 230000003287 optical effect Effects 0.000 description 1
- 239000013307 optical fiber Substances 0.000 description 1
- 238000001259 photo etching Methods 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- 238000005086 pumping Methods 0.000 description 1
- 230000005855 radiation Effects 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
- 229940105963 yttrium fluoride Drugs 0.000 description 1
- RBORBHYCVONNJH-UHFFFAOYSA-K yttrium(iii) fluoride Chemical compound F[Y](F)F RBORBHYCVONNJH-UHFFFAOYSA-K 0.000 description 1
Classifications
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B5/00—Optical elements other than lenses
- G02B5/32—Holograms used as optical elements
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B5/00—Optical elements other than lenses
- G02B5/18—Diffraction gratings
- G02B5/1847—Manufacturing methods
- G02B5/1857—Manufacturing methods using exposure or etching means, e.g. holography, photolithography, exposure to electron or ion beams
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B5/00—Optical elements other than lenses
- G02B5/18—Diffraction gratings
- G02B5/1861—Reflection gratings characterised by their structure, e.g. step profile, contours of substrate or grooves, pitch variations, materials
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- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Optics & Photonics (AREA)
- Engineering & Computer Science (AREA)
- Manufacturing & Machinery (AREA)
- Diffracting Gratings Or Hologram Optical Elements (AREA)
Abstract
The volcanic diffraction grating comprises a volcanic grating structure and an external reflecting layer on a grating substrate, wherein the volcanic grating structure is described by a specific structural function and is a novel holographic diffraction grating structure. The structure can provide a diffraction grating with wide spectrum and high efficiency, has universality in the middle-long wave infrared band, and has important research and application values in the fields of middle-long wave infrared pulse compression, spectrum beam combination, spectrograph and the like.
Description
Technical Field
The invention relates to a diffraction grating of a middle-long wave infrared band and related fields, such as spectrum beam combination, pulse compression, a spectrometer and the like, in particular to a metal type holographic grating in the middle-long wave infrared band and a manufacturing method thereof.
Background
The medium-long wave infrared laser has the characteristics of an atmospheric window, a main heat radiation energy concentration area, a water window wave band and the like, and has important significance in the fields of intense field physics, photoelectric countermeasure, medical treatment, material processing, environmental monitoring and the like.
Compared with the output power of short-wave infrared room temperature continuous laser which is more than the magnitude of microwave kilowatts, the development of high-power medium-long wave infrared laser is more delayed. For example, the middle-long wave infrared quantum cascade laser (Quantum cascade laser, QCL) is limited by problems such as pumping efficiency and thermal effect, and the upper limit of the current output power is only in the watt level, so that the application requirement of the high-power middle-long wave infrared laser cannot be met. The grating-based spectrum beam combining technology is an effective means for improving the output power of the medium-long wave infrared laser and maintaining good beam quality.
In addition, in recent years, mid-wavelength infrared ultra-short laser light based on chirped pulse amplification technology (Chirped pulse amplification, CPA) is rapidly developed to pulse energy millijoules or more, pulse widths of tens of femtoseconds, even on the order of cycles. In CPA technology, pulse stretching and compression are carried out by utilizing gratings, and the broadband high diffraction efficiency gratings are key elements for realizing ultra-large energy and ultra-narrow pulse width output of medium and long wave infrared bands.
At present, the available medium-long wave infrared gratings are mechanical ruling metal gratings no matter the medium-long wave infrared spectrum beam combination, pulse compression or other grating-based application requirements, and most of commercially selectable gratings are master plate resculpting. The ruling grating has ghost lines and high stray light in manufacturing. In contrast, the holographic grating has the advantages of less stray light, strong adjustability of groove-shaped profile, high uniformity of linear density and the like, and has great application significance in various fields of medium and long waves in the future.
At present, no holographic diffraction grating of a medium-wavelength infrared grating is reported, and the holographic diffraction grating comprises a characteristic structure of the medium-wavelength infrared diffraction grating and a preparation mode thereof.
Disclosure of Invention
The technical problem to be solved by the invention is to realize a holographic diffraction grating with broadband high diffraction efficiency in a medium-long wave infrared band, and the holographic diffraction grating comprises a characteristic structure of the grating and a manufacturing method thereof.
The technical scheme of the invention is as follows:
a holographic diffraction grating suitable for medium-long wave infrared band is composed of volcanic grating structure on grating substrate and external reflecting layer.
The volcanic grating structure can be described as a function:
h(x)＝max{0,H×[cos 2 [πxD]/sin 2 [π(1-f)/2]] σ where H is the structural function, x is the lateral distance, H is the groove depth of the grating structure, D is the grating line density, f is the grating's duty cycle, and σ is the grating shape factor.
The groove depth of the volcano-shaped grating structure is greater than 400 nanometers, the linear density is less than or equal to 1000 lines/millimeter, the occupied width ratio value is greater than or equal to 0 and less than or equal to 1, and the shape factor is any positive real number.
The grating substrate can be made of various glass, ceramic and metal materials.
The volcanic grating structure is prepared from a photoresist material on the surface of a grating substrate or is further transferred into the grating substrate through an etching process, wherein the thickness of the photoresist is greater than or equal to the thickness of the groove depth.
The external reflecting layer is various metal films, alloy films, multilayer dielectric films or metal dielectric mixed films.
The outer reflective layer further comprises an additional adhesion layer at the bottom to increase the adhesion between the outer reflective layer and the volcanic grating structure.
The manufacture of the medium-long wave infrared band holographic diffraction grating is prepared based on holographic lithography, and comprises the steps of forming a volcanic photoresist grating structure on the surface of a grating substrate, or further comprises the additional steps of transferring the volcanic structure onto the grating substrate after the step of forming the photoresist grating structure, depositing an adhesion layer, and finally depositing an outer reflection layer.
The invention has the following technical effects:
1) The grating is different from the structures such as sine-like, trapezoid and triangle of the traditional holographic grating, is a novel volcanic structure, has universality in the middle-long wave infrared band, can adjust corresponding structural parameters according to specific use bands, enables the grating to have optical characteristics of wide spectrum and high diffraction efficiency in the use band range, and has important application research value in the middle-long wave infrared field.
2) The invention provides a contour function of a volcano-like grating structure, which is suitable for designing a holographic grating structure with a wavelength of above 3 microns in the middle-long wave infrared band.
3) The grating of the invention is based on a holographic photoetching method, is compatible with the process of the traditional holographic grating, widens the mid-long wave infrared application wave band of the holographic metal grating, and can completely replace the traditional scratch blazed grating used in the applications of high-power laser spectrum beam combination, pulse compression, a spectrometer, a monochromator and the like.
Drawings
FIG. 1 is a schematic diagram of a holographic diffraction grating structure when the external reflection layer provided by the invention is various metal films or alloy films.
FIG. 2 is a schematic diagram of a diffraction grating structure when the external reflection layer provided by the invention is a multilayer dielectric film.
FIG. 3 is a spectrum showing the change of TM polarization-1 order reflection diffraction efficiency of the mid-infrared band metal type hologram grating with the wavelength of incident light at the 50℃incident angle calculated in example 1.
Fig. 4 is an efficiency distribution diagram of TM polarization-1 order reflection diffraction efficiency of the mid-infrared band beam-combining grating calculated in example 1 as a function of the wavelength of incident light and the angle of incidence.
FIG. 5 is a spectrum showing the change of the TM polarization-1 order reflection diffraction efficiency of the 8-10 μm long wave infrared band metal-type holographic grating with the incidence angle at the incidence angle of 44℃calculated in example 2.
FIG. 6 is a graph of the efficiency of TM polarization-1 reflection diffraction efficiency of the 8-10 micron long wave infrared band beam-combining grating calculated in example 2 as a function of the wavelength of incident light and angle of incidence.
FIG. 7 is a spectrum showing the variation of TE polarization-1 order reflection diffraction efficiency of the 8.5-9 μm long-wave infrared band beam-combining grating with the wavelength of incident light at the 19.5 incident angle calculated in example 3.
FIG. 8 is a spectrum of TE polarization, TM polarization and average-1 diffraction efficiency of the multilayer dielectric film grating between 4.6-4.7 μm bands at the 51℃incidence angle calculated in example 4.
In the figure, the 1-grating substrate, the 2-volcano-shaped grating structure, the 3-metal material plated external reflecting layer, the 4-multi-layer dielectric film, the D-grating period, the f-grating ridge top occupation ratio and the H-grating groove depth.
Detailed Description
The technical scheme of the present invention is further described below with reference to the accompanying drawings and examples, but the scope of the present invention should not be limited thereto.
Example 1:
based on the volcanic grating structure shown in fig. 1, the middle-infrared band metal type holographic diffraction grating is designed and prepared.
The period D of the grating was 2.41 microns, the groove depth H of the grating was 0.9 microns, the width ratio f of the top of the grating ridge was 0.25, and the form factor was 2.9.
The TM polarization-1 order diffraction efficiency spectrum of the above designed grating at an incident angle of 50 ° was calculated, and as shown in fig. 3, the average diffraction efficiency of the grating exceeds 94% at a 3-4 micron band, and the diffraction efficiency exceeds 98% at a center wavelength of 3.5 microns. And simultaneously has a wide angular spectrum, and as shown in figure 4, the efficiency in the range of 30-70 degrees at the center wavelength of 3.5 microns is over 90 percent.
A grating of the above parameters was prepared. Spin-coating a 900 nm thick photoresist layer on a 50mm×50mm fused quartz substrate at 1700 rpm by using spin-coating equipment, baking at 100deg.C for 120s, exposing the substrate coated with the photoresist layer by holographic interference exposure method with exposure power of 30 μW and exposure time of 600s, and developing the exposed sample with 0.4% sodium hydroxide solution to obtain volcanic grating structure sample.
Plating a gold film on the prepared sample by using a magnetron sputtering coating machine, wherein the background of sample platingVacuum is 8×10 -4 Pa, argon flow rate of 40sccm, operating pressure of 0.5Pa, sputtering power of 300W, and sputtering rate of 2.36nm/s.
The gold grating prepared based on the above steps has an actual measurement of 94.13% of TM polarization-1 diffraction efficiency at a wavelength of 3.16 μm and an incident angle of 50 DEG, and an actual measurement of 94.67% of TM polarization-1 diffraction efficiency at a wavelength of 3.76 μm and an incident angle of 50 deg.
Example 2:
based on the volcanic grating structure shown in fig. 1, the metal type holographic diffraction grating with long wave infrared band is designed and prepared.
The period D of the grating was 6.67 microns, the groove depth H of the grating was 2.25 microns, the width ratio f of the top of the grating ridge was 0.2, and the form factor was 2.5.
The diffraction efficiency spectrum of the grating at an incident angle of 44 deg. was calculated, and as shown in fig. 5, the TM polarization-1 order diffraction efficiency of the grating is greater than 98% in the 8-10 micron band. Meanwhile, the optical fiber has a wide angle spectrum, and as shown in figure 6, the diffraction efficiency of TM polarization-1 level is over 98% in the range of 35-65 degrees of incidence angle.
A grating of the above parameters was prepared. Spin-coating a layer of photoresist with the thickness of 2.25 micrometers on a fused quartz substrate with the rotation speed of 1400 revolutions per minute by using spin-coating equipment, baking the substrate coated with the photoresist at the temperature of 100 ℃ for 120 seconds, exposing the substrate with the photoresist by using a holographic interference exposure method, and developing the exposed sample with the exposure power of 100 mu W for 120 seconds by using sodium hydroxide solution with the concentration of 0.5% to obtain a volcanic grating structure sample.
Plating a gold film with the thickness of 200 nanometers on the prepared sample by using a magnetron sputtering coating machine, wherein the background vacuum of sample plating is 8 multiplied by 10 -4 Pa, argon flow of 40sccm, operating pressure of 0.5Pa, sputtering power of 300W, and sputtering rate of 2.36nm/s. The TM polarization-1 diffraction efficiency was found to be 75% at a wavelength of 10.6 microns at an angle of incidence of 44 °.
Example 3:
based on the volcanic grating structure shown in fig. 1, a TE polarization high-efficiency diffraction grating of a long-wave infrared band is designed.
The period D of the grating was 12.82 microns, and the TE polarization-1 diffraction efficiency of the grating was calculated at an incident angle of 19.5 °, as shown in fig. 7, the average diffraction efficiency of the grating was > 94% for TE polarized light-1 orders in the 8.5-9 micron band, and the TE polarization-1 order diffraction efficiency at 8.5 microns was > 98%.
Example 4:
the volcanic multilayer dielectric film middle-infrared grating is designed and prepared, and is shown in figure 2.
Based on the grating structure shown in fig. 2, the multilayer dielectric film grating with the wave band of 4.6-4.7 microns is designed and prepared, the grating period D is 3 microns, the groove depth is 3.328 microns, and the total thickness of the high and low refractive index film layers of the multilayer dielectric film is 6.16 microns respectively. The diffraction efficiency of the grating at a 51 ° angle of incidence in the 4.6-4.7 micron band was calculated as shown in fig. 8. The grating has polarization independent characteristics, has high diffraction efficiency under TE polarization and TM polarization, and has TM polarization-1 diffraction efficiency of more than 95% under 4.6-4.7 microns wave band, TE polarization-1 diffraction efficiency of more than 85% and average diffraction efficiency of more than 90%.
And preparing the volcanic multilayer dielectric film grating. A photoresist layer with the thickness of 3.328 micrometers is spin-coated on a fused quartz substrate with the rotation speed of 2000 revolutions per minute by using spin-coating equipment, then baked for 120 seconds at the temperature of 100 ℃, the substrate coated with the photoresist is exposed by using a holographic interference exposure method, the exposure power is 140 mu W, the exposure time is 600 seconds, and the exposed sample is subjected to development treatment by using sodium hydroxide solution with the concentration of 0.4%, so that the volcanic grating structure sample is obtained. And (3) alternately plating yttrium fluoride and germanium films on the surface of the prepared volcanic grating structure by using a magnetron sputtering coating machine to prepare the multi-layer dielectric film grating.
Claims (7)
1. The holographic diffraction grating of the middle-long wave infrared band is characterized by sequentially comprising a grating substrate (1), a grating structure (2) and an external reflecting layer (3) from bottom to top;
the grating structure is volcanic and satisfies the following structural function h:
h(x)＝max{0,H×[cos 2 [πxD]/sin 2 [π(1-f)/2]] σ }
wherein x is the transverse distance, H is the groove depth of the grating structure, D is the grating linear density, f is the grating occupation ratio, sigma is the grating shape factor, H is more than 400 nanometers, D is less than or equal to 1000 lines/millimeter, 0 < f < 1, and sigma is any positive real number.
2. Holographic diffraction grating in the mid-long wave infrared band of claim 1, in which said grating substrate is made of glass, ceramic or metallic material.
3. The medium-long wave infrared band holographic diffraction grating of claim 1, wherein the grating structure is prepared from a photoresist material on the surface of the grating substrate, wherein the thickness of the photoresist material is greater than or equal to the groove depth, and the grating structure is transferred into the grating substrate by etching.
4. The holographic diffraction grating of claim 1, wherein the external reflection layer is a metal film, an alloy film, a multi-layer dielectric film, or a metal dielectric hybrid film.
5. The medium-long infrared band holographic diffraction grating of claim 4, wherein the outer reflective layer comprises an additional adhesion layer at the bottom to increase adhesion between the outer reflective layer and the volcano-like grating structure.
6. A method for preparing a holographic diffraction grating of a medium-long wave infrared band is characterized by comprising the steps of forming a volcano-shaped grating structure prepared from a photoresist material on the surface of a grating substrate, depositing an adhesion layer and finally depositing an outer reflection layer.
7. A method for preparing a medium-long wave infrared band holographic diffraction grating is characterized by comprising the steps of forming a volcano-shaped grating structure prepared from a photoresist material on the surface of a grating substrate, transferring the volcano-shaped structure into the grating substrate through etching after the step of forming the photoresist grating structure, depositing an adhesion layer, and finally depositing an outer reflection layer.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202311626430.XA CN117406328A (en) | 2023-11-30 | 2023-11-30 | Holographic diffraction grating of middle-long wave infrared band and manufacturing method thereof |
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| Application Number | Priority Date | Filing Date | Title |
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| CN202311626430.XA CN117406328A (en) | 2023-11-30 | 2023-11-30 | Holographic diffraction grating of middle-long wave infrared band and manufacturing method thereof |
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| CN117406328A true CN117406328A (en) | 2024-01-16 |
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| CN202311626430.XA Pending CN117406328A (en) | 2023-11-30 | 2023-11-30 | Holographic diffraction grating of middle-long wave infrared band and manufacturing method thereof |
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- 2023-11-30 CN CN202311626430.XA patent/CN117406328A/en active Pending
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