CN103245995B - 10.3 mu m-11.3 mu m transmissive long-wave infrared optical filter and preparation method - Google Patents

Abstract

The invention relates to a 10.3 mu m-11.3 mu m transmissive long-wave infrared optical filter and a preparation method, and belongs to the technical field of optical thin films. The optical filter comprises a germanium substrate, a long-wave-pass film system and a short-wave-pass film system, wherein the structure of the long-wave-pass film system is (0.5hl0.5h)^9(0.574l1.148h0.574l)^5(0.36h0.7210.36h)^5, and the central wavelength is 7,300 nm; the structure of the short-wave-pass film system is (1h)^ 8, and the central wavelength is 14,600 nm; l and h adopt a zinc sulphide film and a lead telluride film respectively; and the substrate is heated in vacuo and bombarded by an ion beam, the film systems are deposited on the two sides of the substrate respectively through resistance evaporation under the condition that argon is fed into an ion source, and the optical filter is prepared after cooling. The optical filter has a high transmittance when in a range from 10.3 mu m to 11.3 mu m, and has a large stop width in a range from 0.9 mu m to 10.15 mu m and in a range from 11.45 mu m to 20 mu m; further, the film layers are fewer, and using requirements of a remote sensing system are met; and the method is simple, convenient, stable, and high in yield.

Description

10.3-11.3 μm long-wave infrared filter and its preparation method

technical field

The invention relates to a 10.3-11.3 μm long-wave infrared filter and a preparation method thereof, in particular to a filter with high transmittance in the 10.3-11.3 μm spectral band and at the same time at 0.9-10.15 μm and 11.45-20 μm The invention relates to a long-wave infrared filter with a wide cut-off spectrum; it belongs to the technical field of optical thin films.

Background technique

The optical filter with high transmittance in the 10.3-11.3 μm spectral band is a key optical filter in the current remote sensing detection system. In order to reduce the influence of signal noise, the optical signals in the 0.9-10.15 μm and 11.45-20 μm spectral bands need to be suppressed in the remote sensing detection system. Therefore, it is urgent to design a long-wave infrared filter with high transmittance in the 10.3-11.3 μm spectral band, wide cut-off in the 0.9-10.15 μm and 11.45-20 μm spectral bands, and better film quality.

Contents of the invention

Aiming at the prior art, there is no long-wave infrared filter with high transmittance in the 10.3-11.3 μm spectral band and wide cut-off in the 0.9-10.15 μm and 11.45-20 μm spectral bands. One of the objectives of the present invention is to provide a long-wave infrared filter that passes through 10.3-11.3 μm. 20μm broad cut-off.

The second object of the present invention is to provide a method for preparing a long-wave infrared filter that transmits at 10.3-11.3 μm.

The purpose of the present invention is achieved through the following technical solutions.

Disclosed is a 10.3-11.3 μm long-wave infrared filter, which includes a substrate, a long-wave pass film system on one side of the substrate, and a short-wave pass film system on the other side of the substrate.

Wherein, the base material is germanium, the preferred size is: length 29.5mm, width 1.36mm, thickness 1.2mm, and the preferred surface finish is 40/20;

The long-wave pass film system includes alternately stacked zinc sulfide (ZnS) film layers and lead telluride (PbTe) film layers, and the structure is: (0.5hl0.5h)^9 (0.574l1.148h0.574l)^5 (0.36h0. 72l0.36h)^5, the central wavelength is 7300nm; where h is the lead telluride film layer, 0.5, 1.148 and 0.36 are the coefficients of the lead telluride film thickness corresponding to the basic thickness, and 0.5h represents the lead telluride film thickness is 0.5 basic thickness, 1.148h means the lead telluride film thickness is 1.148 basic thickness, 0.36h means the lead telluride film thickness is 0.36 basic thickness, l is the zinc sulfide film layer, 1, 0.574 and 0.72 are respectively The coefficient of the zinc sulfide film thickness corresponding to the basic thickness, l means that the thickness of the zinc sulfide film is 1 basic thickness, 0.574l means that the thickness of the zinc sulfide film is 0.574 basic thickness, and 0.72l means that the thickness of the zinc sulfide film is 0.72 basic Thickness, the basic thickness is a quarter of the central wavelength of the optical thickness, the cycle number of the basic film stack (0.5hl0.5h) is 9, the basic film stack (0.574l1.148h0.574l) and the basic film stack (0.36h0 .72l0.36h) are all 5 cycles.

Adopt TFCalc software to optimize the structure of the long-wave pass film system, obtain the preferred long-wave pass film system, as shown in table 1, wherein, the film layer that the number of layers is 1 is the outermost layer of the long-wave pass film system, and the number of layers The film layer of 39 is deposited on the germanium substrate, which is the innermost layer of the long-wave pass film system;

Table 1 Long wave pass film system

The short-wave pass film system includes alternately stacked zinc sulfide film layers and lead telluride film layers. The coefficient of the basic thickness, l means the thickness of the zinc sulfide film layer is 1 basic thickness, h is the lead telluride film layer, 1 is the coefficient of the lead telluride film layer thickness corresponding to the basic thickness, h means the lead telluride film layer thickness is 1 a basic thickness, the basic thickness is a quarter of the central wavelength of the optical thickness, and the period number of the basic film stack (lh) is 8.

Adopt TFCalc software to optimize the structure of the short-wave pass film system, obtain the preferred short-wave pass film system, as shown in table 2, wherein, the film layer that the number of layers is 1 is the outermost layer of the short-wave pass film system, and the number of layers The film layer of 16 is deposited on the germanium substrate, which is the innermost layer of the short-wave pass film system;

Table 2 Short-wave pass film system

A method for preparing a 10.3-11.3 μm long-wave infrared filter according to the present invention, the steps of the method are as follows:

(1) Put the clean substrate into a clean vacuum chamber and evacuate to 3.0×10 ^-3 Pa;

(2) Heat the substrate to 150°C and keep it for 30min;

(3) Turn on the Hall light ion source to pass argon gas, the gas flow rate is 30 sccm, the cathode voltage is 100-200V, and the anode voltage is 50-100V, so that the anode current is 0.5A; Alternately deposit the zinc sulfide film layer and the lead telluride film layer in the long-wave pass film system layer by layer, and alternately deposit the zinc sulfide film layer and the lead telluride film layer in the short-wave pass film system layer by layer on the other side of the substrate until the completion The deposition of the film system; wherein, the deposition rate of the zinc sulfide film layer is 2.0-3.0nm/s, and the deposition rate of the lead telluride film layer is 0.8-1.0nm/s; the thickness of the film layer is monitored by the optical ratio method;

(4) The substrate is naturally cooled to room temperature to obtain the 10.3-11.3 μm long-wave infrared filter according to the present invention.

Beneficial effect

1. The present invention provides a 10.3-11.3 μm long-wave infrared filter, the filter achieves excellent technical indicators: it has a high transmittance τ _av ≥ 80% in the 10.3-11.3 μm spectrum, and at 0.9 ～10.15μm and 11.45～20μm wide cut-off, the cut-off depth τ _λ <1% in the cut-off area, the half-power point wavelength tolerance is within 50nm, which can greatly improve the pass band and cut-off band of the filter in this spectrum. Features, meet the requirements of the remote sensing detection system, with high stability and reliability;

2. The present invention provides a 10.3-11.3 μm long-wave infrared filter, the film system of the filter includes alternately stacked zinc sulfide film layers and lead telluride film layers, and the number of film system layers is relatively small;

3. The present invention provides a preparation method of a 10.3-11.3 μm long-wave infrared filter, the method can produce the filter of the present invention, the process is stable, the repeatability is good, the operation is simple, and the finished product is High rate.

Description of drawings

Fig. 1 is the transmittance spectrum diagram of the optical filter in embodiment 1.

Detailed ways

In order to fully illustrate the characteristics of the present invention and the mode of carrying out the present invention, examples are given below.

Example 1

Disclosed is a 10.3-11.3 μm long-wave infrared filter, which includes a germanium substrate, a long-wave pass film system on one side of the substrate, and a short-wave pass film system on the other side of the substrate.

Wherein, the base is 29.5mm long, 1.36mm wide, 1.2mm thick, and has a surface finish of 40/20.

The long-wave pass film system includes alternately stacked zinc sulfide film layers and lead telluride film layers, and the center wavelength is 7300nm; the parameters of each film layer are shown in Table 3, and the film layer with the number of layers is 1. The outer layer, the film layer with 39 layers is deposited on the germanium substrate, which is the innermost layer of the long-wave pass film system;

Table 3 Long-wave pass film system and film thickness monitoring

The short-wave pass film system includes alternately stacked zinc sulfide film layers and lead telluride film layers, and the center wavelength is 14600nm. The parameters of each film layer are shown in Table 4, and the film layer with the number of layers is 1. The outer layer, with 16 layers deposited on the germanium substrate, is the innermost layer of the short-wave pass film system;

Table 4 Short-wave pass film system and film thickness monitoring

The steps of the preparation method of the optical filter described in this embodiment are as follows:

(1) Use a vacuum cleaner to remove impurities in the vacuum chamber, and then wipe the inner wall of the vacuum chamber with degreasing gauze dipped in absolute ethanol; ultrasonically clean the substrate with analytical pure acetone for 10 minutes, and then ultrasonically clean the germanium substrate with analytical pure ethanol for 10 minutes. Put the substrate into a clean vacuum chamber and evacuate to 3.0×10 ^-3 Pa;

(2) Heat the substrate to 150°C and keep it for 30min;

(3) Turn on the Hall light ion source to pass argon gas, the gas flow rate is 30 sccm, the cathode voltage is 100-200V, and the anode voltage is 50-100V, so that the anode current is 0.5A; Alternately deposit the zinc sulfide film layer and the lead telluride film layer in the long-wave pass film system layer by layer, and alternately deposit the zinc sulfide film layer and the lead telluride film layer in the short-wave pass film system layer by layer on the other side of the substrate until the completion The deposition of the film system; wherein, the deposition rate of the zinc sulfide film layer is 2.0-3.0nm/s, and the deposition rate of the lead telluride film layer is 0.8-1.0nm/s; the thickness of the film layer is monitored by the light ratio method, and the monitoring The wavelength and times are shown in Table 3 and Table 4;

(4) The substrate is naturally cooled to room temperature to obtain the 10.3-11.3 μm long-wave infrared filter described in this embodiment.

Carry out following performance test to described optical filter:

The system 2000 infrared Fourier spectrometer of PE Company was used to test, and the transmission spectrum was obtained as shown in Figure 1. The spectral lines in Figure 1 were calculated with UVWINLAB software, and it can be known that the average transmission of the filter in the 10.3-11.3 μm spectral segment The transmittance is 84.61%, the average transmittance in the 0.9-10.15μm spectrum is 0.43% and the average transmittance in the 1.45-20μm spectrum is 0.01%.

The present invention includes but is not limited to the above embodiments, and any equivalent replacement or partial improvement made under the spirit and principle of the present invention will be considered within the protection scope of the present invention.

Claims (9)

1. A 10.3～11.3 μm through long-wave infrared filter, characterized in that: the filter comprises a germanium substrate, a long-wave pass film system on one side of the substrate and a short-wave pass film system on the other side of the substrate; The long-wave pass film system includes alternately stacked zinc sulfide and lead telluride film layers, the structure is: (0.5hl0.5h)^9(0.574l1.148h0.574l)^5(0.36h0.72l0.36h)^5 The wavelength is 7300nm; h is the lead telluride film layer, 0.5h means the lead telluride film thickness is 0.5 basic thickness, 1.148h means the lead telluride film thickness is 1.148 basic thickness, 0.36h means the lead telluride film layer The thickness is 0.36 basic thickness, l is the zinc sulfide film layer, which means that the thickness of the zinc sulfide film layer is 1 basic thickness, 0.574l means that the thickness of the zinc sulfide film layer is 0.574 basic thickness, and 0.72l means that the thickness of the zinc sulfide film layer is 0.72 basic thickness, the cycle number of the basic membrane stack (0.5hl0.5h) is 9, and the cycle numbers of the basic membrane stack (0.574l1.148h0.574l) and (0.36h0.72l0.36h) are both 5; The short-wave pass film system includes alternately stacked zinc sulfide and lead telluride film layers, the structure is: (lh)^8, the center wavelength is 14600nm; l is the zinc sulfide film layer, indicating that the thickness of the zinc sulfide film layer is 1 basic thickness, h is the lead telluride film layer, indicating that the lead telluride film layer thickness is 1 basic thickness, and the period number of the basic film stack (lh) is 8; The basic thickness is a quarter of the central wavelength of the optical thickness of the long-wave pass film system or the short-wave pass film system. 2. A 10.3-11.3 μm long-wave infrared filter according to claim 1, characterized in that: the base is 29.5 mm long, 1.36 mm wide, and 1.2 mm thick; the surface finish is 40/20. 3. A 10.3-11.3 μm long-wave infrared filter according to claim 1 or 2, characterized in that: the long-wave pass film system is as shown in Table 1, and the film layer with 1 layer is a long-wave pass film The outermost layer of the system, the film layer with a layer number of 39 is deposited on the substrate, which is the innermost layer of the long-wave pass film system; Table 1 Long wave pass film system 4. A 10.3-11.3 μm long-wave infrared filter according to claim 1 or 2, characterized in that: the short-wave pass film system is as shown in Table 2, and the film layer with 1 layer is a short-wave pass film The outermost layer of the system, the film layer with 16 layers is deposited on the substrate, which is the innermost layer of the short-wave pass film system; Table 2 Short-wave pass film system 5. A 10.3-11.3 μm long-wave infrared filter according to claim 4, characterized in that: the long-wave pass film system is as shown in Table 1, and the film layer with 1 layer is the long-wave pass film system The outermost layer, the film layer with a layer number of 39 is deposited on the substrate, which is the innermost layer of the long-wave pass film system; Table 1 Long wave pass film system 6. A method for preparing a 10.3-11.3 μm long-wave infrared filter as claimed in claim 1 or 2, characterized in that: the steps of the method are as follows: (1) Put the clean substrate into a clean vacuum chamber and evacuate to 3.0×10 ^-3 Pa; (2) Heat the substrate to 150°C and keep it for 30min; (3) Turn on the Hall light ion source to pass argon gas, the gas flow rate is 30sccm, the cathode voltage is 100-200V, and the anode voltage is 50-100V, so that the anode current is 0.5A; use the resistance evaporation method to deposit on both sides of the substrate respectively Long-wave pass film system and short-wave pass film system; the deposition rate of the zinc sulfide film layer is 2.0-3.0nm/s, and the deposition rate of the lead telluride film layer is 0.8-1.0nm/s; the thickness of the film layer is monitored by the optical ratio method; (4) The substrate is naturally cooled to room temperature to obtain a 10.3-11.3 μm long-wave infrared filter. 7. The preparation method of a 10.3-11.3 μm long-wave infrared filter according to claim 6, characterized in that: the long-wave pass film system and film thickness monitoring are as shown in Table 3, and the number of layers is 1 The film layer is the outermost layer of the long-wave pass film system, and the film layer with 39 layers is deposited on the substrate, which is the innermost layer of the long-wave pass film system; Table 3 Long-wave pass film system and film thickness monitoring 8. A method for preparing a 10.3-11.3 μm long-wave infrared filter according to claim 6, characterized in that: the short-wave pass film system and film thickness monitoring are as shown in Table 4, and the number of layers is 1 The film layer is the outermost layer of the short-wave pass film system, and the film layer with 16 layers is deposited on the substrate, which is the innermost layer of the short-wave pass film system; Table 4 Short-wave pass film system and film thickness monitoring 9. A method for preparing a 10.3-11.3 μm long-wave infrared filter according to claim 8, characterized in that: the long-wave pass film system and film thickness monitoring are as shown in Table 3, and the number of layers is 1 The film layer is the outermost layer of the long-wave pass film system, and the film layer with 39 layers is deposited on the substrate, which is the innermost layer of the long-wave pass film system; Table 3 Long-wave pass film system and film thickness monitoring