高性能中波红外陷波滤光片设计与研制|江阴雨辰互联

2024年4月11日发(作者：)

第 16 卷　第 4 期

2023年7月

中国光学（中英文）

Chinese Optics

Vol. 16　No. 4

Jul. 2023

文章编号 2097-1842（2023）04-0904-12

Theoretical design and preparation of high performance

MWiR notch filter

SHANG Peng

1,2

，CHEN Bei-xi

，SUN Peng

，LIU Hua-song

2 *

，BAI Jin-lin

，JI Yi-qin

，

CAO Bo

1 *

，MA Yuan-fei

，LIN Quan

（1. GRINM Guojing Advanced Materials Co., Ltd, General Research Institute for

Nonferrous Metals, Beijing 100088, China；

2. Tianjin Key Laboratory of Optical Thin Film, Tianjin Jinhang Technical

Physics Institute, Tianjin 300308, China；

3. Northwestern Polytechnical University, Xi’an 710129, China）

* Corresponding author，E-mail: **********************; **********************

Abstract: In order to effectively suppress the interference of CO

radiation 4.3 μm on MWiR target signal

with wavelength of 3 μm−5 μm, based on the Needle random intercalation optimization algorithm, an accur-

ate inversion correction model for the growth error of multi-layer ultra-thick Ge/Al

films under quartz

crystal monitoring is established by the electron beam evaporation method, thus realizing the design, the ac-

curate inversion and the accurate preparation of MWiR notch filter. In order to solve the problem that the sur-

face profile of the MWiR notch filter changes greatly, the preset substrate surface method is used to realize

the low surface profile regulation of MWiR notch filter. The results show that the high refractive index Ge

film has good deposition stability with the increase of coating time, while the deposition scale factor of low

refractive index Al

thin film changes up to 11.9% in a regular gradual trend. For the prepared MWiR

notch filter, the average cut-off transmittance is less than 0.3% in the wavelength range of 4.2 μm−4.5 μm,

and the average transmittances are more than 95% in the wavelength range of 3.5 μm−4.05 μm and 4.7 μm−

5.0 μm. The surface profile of the substrate after coating can be effectively controlled in a small range. The

film has good adaptability to complex environment, and has successfully passed the environmental test of

firmness, high temperature, low temperature and damp heat specified in GJB 2485-95.

Key words: electron beam evaporation; quartz crystal deposition monitor; infrared filter; thin film; inversion

correction

收稿日期：2022-09-16；修订日期：2022-10-08

基金项目：国家自然科学基金（No. 61905179）；河北省自然科学基金（No. F2022103002）；河北省重点研发计划项目

（No. 22351101D）

Supported by the National Natural Science Foundation of China (No. 61905179); Natural Science Foundation

of Hebei Province (No. F2022103002); Key R & D Projects of Hebei Province (No. 22351101D)

第 4 期

SHANG Peng, et al. : Theoretical design and preparation of high performance ......

905

高性能中波红外陷波滤光片设计与研制

尚　鹏

1,2

，陈蓓曦

，孙　鹏

，刘华松

2 *

，白金林

，季一勤

，曹　波

1 *

，马远飞

，林　泉

（1. 有研国晶辉新材料有限公司北京有色金属研究总院, 北京 100088；

2. 天津津航技术物理研究所天津市薄膜光学重点实验室, 天津 300308；

3. 西北工业大学, 陕西西安 710129）

摘要：为了有效抑制4.3 μm CO

辐射对3 μm~5 μm中波红外目标信号的干扰，基于Needle随机插层优化算法，采用电子

束蒸发方法，建立了石英晶振监控方式下多层超厚Ge/Al

薄膜生长误差的精确反演修正模型，实现了中波红外陷波滤

光片的设计、精确反演与制备；同时，针对中波红外陷波滤光片存在的面型变化大的问题，采用预置基底面型方法，实现

了中波红外陷波滤光片低面型调控。研究结果表明：随着镀膜时间的增加，高折射率Ge膜具有较好的生长稳定

性，而低折射率Al

薄膜材料沉积比例因子变化高达11.9%，且呈规律性渐变趋势；所制备的中波红外陷波滤光片在

4.2 μm~4.5 μm波段区间平均截止透过率小于0.3%；3.5 μm~4.05 μm及4.7 μm~5.0 μm波段的平均透过率大于95%，镀

膜后的面型被有效控制在较小范围；膜层具有较好的复杂环境适应性，成功通过了GJB 2485-95中牢固性、高温、低温、

湿热等环境试验考核。

关键词：电子束蒸发法；石英晶振监控法；红外滤光片；薄膜；反演修正

中图分类号：O484 文献标志码：A doi：10.37188/CO.2022-0193

target imaging, filtering optics need to be intro-

1 Introduction

With the development of infrared optoelectron-

ic technology, the application field of passive photo-

electric detection and imaging system based on tar-

get infrared radiation is becoming more and more

extensive, and plays an important role in enhan-

cing the dynamic perception of complex environ-

ments

[1-2]

. In order to obtain a clearer infrared target

imaging, the acquired target signal should be modu-

lated or filtered by various means to suppress the in-

terference of background noise and improve the

contrast of the image. And a considerable part of the

interference noise is from the environmental back-

ground, such as atmospheric CO

radiation interfer-

ence

[3-5]

, whose radiation peak wavelength position

is at 2.7 μm, 4.3 μm and 15 μm, of which the radiation

coefficient value at 4.3 μm is the largest, which is

one of the most serious radiation sources in the

background noise of MWiR detection imaging.

Therefore, in order to effectively suppress the inter-

ference of CO

radiation 4.3 μm on the infrared tar-

get signal, and then obtain clear and stable infrared

duced in the original infrared optical system.

At present, the method commonly used at

home and abroad is the short-wave infrared band-

pass filter

[6-7]

. However, while the short-wave in-

frared band-pass filter effectively removes 4.3 μm

radiation interference, the useful signal light

with wavelength greater than 4.3 μm will also be

filtered out, resulting in the useful MWiR signal

light in the wavelength range from 3.0 μm to 5.0 μm

not being fully effective. Therefore, in recent years,

notch filter (also called bandstop filter or minus fil-

ter) with high transmittance for most MWiR

wavelengths light and effective cutoff for light in a

specific wavelength range (stop band) has received

a lot of attention from researchers

[8-9]

. For example,

Wang S L et al..

[10]

from Xi'an Institute of Applied

Optics prepared a dual-channel bandpass filter with

excellent spectral performance by using the method

of respectively designing a MWiR bandpass filter

film and a MWiR minus filter on both sides of a

single-crystal germanium substrate; meanwhile, it is

pointed out that the variation of the evaporation

angle of the coating material and the accumulation

906

中国光学（中英文）

第 16 卷

of errors in the thickness of each layer were the

main reasons for the difference between the test

spectrum of the experimental film and the theoretic-

al design spectrum. Based on the Rugate theory,

Zhang B S et al.. from Institute of Lanzhou

Physics

[11]

designed 3.8 μm single-wavelength

minus filter and 1.315 μm and 3.8 μm dual-

wavelength minus filter, but it is difficult to achieve

because the film layer is relatively complicated;

[12]

that can be selected in the 3 μm~5 μm MWiR band,

such as Ge, Al

, SiO, ZnS, YbF

, and ZnSe. Due

to the thickness of MWiR notch filter film is relat-

ively thick, if the material ZnS, YbF

and/or ZnSe is

used, a large stress will be generated with the in-

crease of the film deposition thickness, which is

very easy to produce damage such as cracking and

delamination. Meanwhile, considering the maturity

of the existing coating process, the mechanical prop-

erties of the film layer and its matching with sub-

strate Ge, Ge and Al

are finally selected as the

high and low refractive index materials of the film

structure of MWiR notch filter. The thin film pre-

paration method uses the electron beam evaporation

method. The starting background vacuum of

1.3×10

−3

Pa was used for film deposition, and the

background vacuum was gradually increased to ~

6×10

−4

Pa with the increase of coating time. The

substrate surface was pre-cleaned for 5 min using an

APS ion source before coating, and the deposition

process parameters are shown in Table 1. The vari-

ation of optical constants (refractive index and ex-

tinction coefficient) of the obtained high and low re-

fractive index films in the wavelength range of

2.0 μm~10.0 μm are shown in Fig. 1 (color online).

Tab. 1 Deposition parameters of thin film

表 1 薄膜沉积工艺参数

ThinOxygen flowGrowthDeposition rateElectron beam

film(sccm)temperature (°C)(nm/s)(mA)

Gao P et al.. proposed the fold-like design meth-

[12]

od for notch filter, and analyzed the effects of vari-

ous design parameters on the spectra; Zhou Sh et

al..

[13]

from Shanghai Institute of Technical Physics

designed the minus filter system and the long wave

cut-off film system on both sides of the Ge sub-

strate respectively to form a bi-color filter contain-

ing two channels, 3.2 μm−3.8 μm and 4.9 μm−

5.4 μm, respectively. In addition, according to the

theory of equivalent refractive index, the research-

ers also proposed multi-film design methods

[14]

and

thickness matching layer method

[15-16]

, but there are

certain limitations in practical engineering imple-

mentation

[12]

Therefore, to address the current problem of

difficult design and accurate preparation of MWiR

notch filters, we firstly adopt the Needle random in-

terpolation optimization method based on the

(4H/L)

basic film system structure to achieve the

optimal design of high-performance MWiR notch

filters; secondly, by establishing a multilayer film

growth error correction model, the cumulative thick-

ness error in the coating process is effectively re-

duced to ensure the accurate preparation of MWiR

notch filters; finally, the low surface profile regula-

tion of the MWiR notch filter is achieved by using

the pre-substrate surface profile method. In addition,

the surface morphology and the applicability to

complex environments of the obtained MWiR notch

filters are evaluated.

−

200

0.35

0.30

250

320

From Fig. 1(a), it can be seen that the optical

constants (refractive index n and extinction coeffi-

cient k) of the prepared Ge films show a trend of

first decreasing and then stabilizing with the in-

crease of the examined wavelength in the range of

2.0 μm~10 μm band, specifically, the refractive in-

dex of the film layer material gradually decreases

from ~4.31 to ~4.20 and stabilizes. The extinction

coefficient k gradually decreases from ~0.005 to 0,

and it shows good infrared transparency properties

2 Film system design and analysis

There are various transparent film materials

第 4 期

SHANG Peng, et al. : Theoretical design and preparation of high performance ......

907

0.040

4.34

(a)

4.32

0.035

Ge thin film

4.30

0.030

4.28

4.26

0.025

4.24

0.020

4.22

4.20

0.015

4.18

0.010

4.16

4.14

0.005

4.12

4.10

2 000

3 000

4 0005 0006 000

7 0008 0009 00010 000

ively small thickness difference is obtained by us-

ing the Needle optimization algorithm in combina-

tion with multiple de-thinning and local re-optimiza-

tion. The corresponding theoretical transmission

spectral curves are shown in Fig. 2. From Fig. 2, it

can be seen that the infrared notch filter film has

good spectral characteristic. The average transmit-

tance within the band ranges of 3.5 μm~4.05 μm

and 4.7 μm~5.0 μm reaches ~97.21% and ~97.75%,

respectively, and the average cut-off transmittance

Wavelength/nm

1.65

0.25

(b)

1.60

1.55

0.20

1.50

1.45

0.15

thin film

1.40

1.35

0.10

1.30

1.25

0.05

1.20

1.15

1.100

2 000

3 000

4 0005 0006 000

7 0008 0009 00010 000

within the band of 4.2 μm~4.5 μm is ~0.27%. The

total thickness of this MWiR notch filter film struc-

ture is ~18.6 μm, and it needs to be coated in three

times to complete according to the existing coating

process and crucible configuration, which puts high-

er requirements on the control precision and stabil-

ity of the film preparation process.

Wavelength/nm

Fig. 1 Variation curves of refractive index and extinction

coefficient of Ge and Al

films

(

)

图 1 Ge和Al

薄膜折射率和消光系数变化曲线

in the wavelength range of 3.5 μm~5.0 μm. For the

prepared Al

films, the variation of the optical

constants is relatively more complicated due to the

influence of the transparency band of the film ma-

terial. As can be seen from Fig. 1(b), for the refract-

ive index n, with the increase of the wavelength

from 2 μm to 10 μm, the refractive index of the

film material shows a gradual decreasing

trend, and its average size is about 1.55 in the wave

band of 3.5 μm~5 μm; the size of the extinction

coefficient k shows an opposite trend, and is ba-

sically 0 in the band of 2.0 μm~6.0 μm, and the ef-

fect of the absorption loss of the film material is

basically negligible; however, the value of k in-

creases rapidly with the further increase of the

wavelength.

During the optimized design of the MWiR

notch filter film, the selected initial film system is

Sub/(4H/L)

/Air, where H is Ge and L is Al

, and

after selecting the material and the initial film sys-

tem, a 28-layer non-regular film system with relat-

100

3 600

3 8004 0004 200

4 4004 6004 8005 000

Wavelength/nm

Fig. 2 Theoretical design spectral curve of MWiR notch

filter

图 2 中波红外陷波滤光薄膜理论设计光谱曲线

The variation of the theoretical spectral trans-

mittance of the MWiR notch filter film with the in-

cident angle is shown in Fig. 3. As can be seen from

Fig. 3, with the increase of the incident angle, the

transmission spectra of the MWiR notch filter films

gradually move toward the short-wave direction,

and the cut-off transmittances at the wavelengths of

4.2 μm and 4.3 μm remain basically unchanged,

both being lower than 0.5%, while the cut-off trans-

mittance at the wavelength of 4.5 μm shows an in-

creasing trend with the increase of the incident

angle. At an incidence angle of 30°, the transmit-

tance increases from 0.799% at vertical incidence to

908

中国光学（中英文）

第 16 卷

32.17%. With the increase of incidence angle to 30°,

the average transmittance within the band range of

3.5 μm~4.05 μm decreases rapidly, and the average

transmittance within the band range of 4.7 μm~

5.0 μm tends to increase and then decrease, which is

related to the certain mismatch of the equivalent op-

tical conductance of the film layer under the tilt

angle incidence.

ical design curve. Therefore, how to realize the ac-

curate inversion and correction of the multilayer IR

film is the key to the successful preparation of the

IR notch filter.

To this end, a high standard and low refractive

index film stack structure (LH)

L was grown and

deposited by fixing the scaling factor in combina-

tion with the final optimized obtained multilayer

film system structure, where the physical thickness

of the high and low refractive index film layers in

(

)

(

)

−5

−10

−15

−20

−25

51015

Incident angle/(°)

2530

Change of taverage @3 500-4 050 nm

Change of taverage @4 700-5 000 nm

Transmittance@4 500 nm vs angle

Transmittance@4 300 nm vs angle

Transmittance@4 200 nm vs angle

the (LH)

L standard film stack should be as close as

possible to the average thickness of the high and

low refractive index film layers in the film system

structure, so as to reduce the influence of the differ-

ence in film thickness between the standard film

stack and the actual film system structure on the fi-

nal results. The curves of the theoretical design

spectrum and the measured spectrum are shown in

Fig. 4. As can be seen from Fig. 4, there is a large

gap between the theoretical spectral curve distribu-

tion and the measured spectral curve within the in-

vestigated band range of 2.0 μm~6.0 μm, and the

reasons for the deviation are closely related to vari-

ous factors such as coating vacuum, crystal control

monitoring error, temperature variation in the coat-

ing chamber and evaporation source state during the

actual long time coating process.

51015

202530

Fig. 3 Variation of theoretical spectral transmittance of

films with incident angle

图 3 薄膜理论光谱透过率随入射角度的变化

(

)

2 000

3 000

4 0005 000

Wavelength/nm

6 000

Design

EXP

3 Test results and analysis

3.1 Thin film inversion correction and spectral

performance testing

During the coating process of MWiR notch fil-

ter film, due to the combined effect of various influ-

encing factors (vacuum, evaporation state of the

film material, monitoring errors, etc.), the actual

thickness of the film layer will gradually deviate

from the calibration value as the coating time in-

creases by quartz crystal oscillator monitoring

mode, which eventually causes the actual spectral

curve to be significantly different from the theoret-

Fig. 4 Theoretical design and measured spectral curves of

(LH)

L multilayer film structure under fixed scale

factor

图 4 固定比例因子下，(LH)

L多层薄膜结构理论设计与

实测光谱曲线

Based on the measured spectral curves, the rel-

第 4 期

SHANG Peng, et al. : Theoretical design and preparation of high performance ......

909

ative error distribution of the multilayer film struc-

ture was obtained by fitting with the software

OplayerRe, as shown in Fig. 5. As can be seen from

Fig. 5, with the increase of coating time, for the

films with the low refractive index, the relat-

ive errors of the 1st, 3rd, 5th, 7th and 9th layers are

3.3%, 5.9%, 9.8%, 10.2% and 11.9%, respectively,

and the amount of relative variation between the

layers shows a trend of first increasing and then de-

creasing; for the Ge films with the high refractive

index, the actual layer thickness is smaller than the

designed layer thickness, and the relative error is

negative, and varies between −2.7% and −1.7%, and

the maximum relative variation between the film

layers is 1.0%, which is within the theoretical fit-

ting error range.

(

)

3 0003 500

EXPDesign

4 000

4 500

Wavelength/nm

5 0005 500

Fig. 6 Design and measured spectral curves of MWiR

notch filter film obtained based on the modified

scale factor

图 6 基于修正比例因子，获得的中波红外陷波滤光薄膜

设计与实测光谱曲线

Preparation of mid-wave infrared anti-reflect-

ive coating on the back of the MWiR notch filter is

illustrated. The measured transmission spectra of the

double-sided coating sample are shown in Fig. 7. As

can be seen from Fig. 7, the average cut-off trans-

mittance of MWiR notch filter film after double-

sided coating is less than 0.3% in the band range of

4.2 μm~4.5 μm; the average transmittance is larger

0.12

0.10

0.08

0.06

0.04

0.02

−0.02

−0.04

123456789

Layer number

than 95% in the band range of 3.5 μm~4.05 μm and

4.7 μm~5.0 μm, which is about <2.0% lower than

the theoretical design, but still higher than the tech-

nical index requirement of related products. The oc-

currence of this phenomenon is closely related to the

increase of coating time, the oxidation of Ge materi-

al during the coating process, and the increase of

surface roughness of deposited film layer.

Fig. 5 Relative error distribution of each film

图 5 各膜层相对误差分布情况

With the above calibrated scale factors of high

and low refractive index film thickness, the whole

film structure of the MWiR notch filter film was

prepared by electron beam evaporation method.

During the preparation process, it is required to

maintain the parameter consistency of each coating

ing time, charge weight, and quartz crystal state.

The designed and measured transmission spectra of

the MWiR notch filter film are shown in Fig. 6. As

can be seen from Fig. 6, the measured transmission

spectra show a good consistency with the theoretic-

al design spectra by using the modified film thick-

ness gradient scaling factor, which further verifies

the accuracy of the inverse fitting of the relative er-

ror of the above multilayer film.

process, such as the starting coating vacuum, coat-

(

)

100

3 600

3 8004 0004 200

4 4004 6004 8005 000

Wavelength/nm

Fig. 7 Measured transmission spectrum curve after double-

sided coating

图 7 双面镀膜后的实测透射光谱曲线

910

中国光学（中英文）

第 16 卷

3.2 Film surface morphology

Fig. 8 (color online) shows the surface morpho-

logy of the MWiR notch filter coated on the ger-

manium substrate. It can be also seen from Fig. 8

that the surface RMS values of the germanium sub-

strate used before and after coating are 0.546 nm

and 0.551 nm, respectively. In comparison, the sur-

face roughness increases slightly after coating,

which is related to the release of internal stresses in

the film layer, structural defects in the film material,

external contamination, and many other factors.

In addition, we also tested the change of re-

flective surface profile of the substrate before and

after coating by ZYGO interferometer, as shown in

Fig. 9 (color online). Wherein, Figs. 9(a)−9(b) show

the changes of surface profile before and after coat-

ing without surface profile compensation, and

Figs. 9(c)−9(d) show the changes of surface profile

before and after coating with surface profile com-

pensation. From Fig. 9(a) and Fig. 9(b), it can be

seen that due to the thickness of the prepared MWiR

notch filter film is thick, for the substrate with

PV=0.121λ (where λ is at the test laser wavelength

of 632.8 nm) before coating, it becomes 1.999λ after

coating, which is far beyond the relevant usage re-

+0.002 02

−0.002 03

0.526

(a)+0.004 51

−0.002 37

0.526

(b)

0.702

quirements. In order to effectively reduce the sur-

face profile change of the substrate after coating and

avoid its influence on the wavefront, the method of

presetting the surface profile of the substrate is in-

troduced. As can be seen from Fig. 9(c) and Fig. 9(d),

by presetting the 1.990λ surface profile state on the

surface of the coated MWiR notch filter film, the

surface profile becomes 0.191λ after coating, and

the surface profile of the MWiR notch filter is im-

proved more significantly.

0.702

coating

Fig. 8 Surface morphology graphs before (a) and after (b)

图 8 镀膜前(a)及镀膜后(b)表面形貌图

(a)+0.049 60

−0.071 48

(b)

+1.068 74

−0.930 36

(c)

+0.906 06

−1.084 29

(d)

+0.903 1

−1.002 8

Fig. 9 Surface profile change before and after coating without surface profile compensation (a, b) and with surface profile

compensation (c, d)

图 9 基底无面型补偿情况下，镀膜前后的面型变化(a, b)；基底有面型补偿情况下，镀膜前后的面型变化(c, d)

第 4 期

SHANG Peng, et al. : Theoretical design and preparation of high performance ......

911

3.3 Film environmental adaptability

According to the environmental test require-

ments and methods of adhesion, high temperature,

low temperature, humidity and heat in

GJB2485~95 General Specification for Optical

Films, the complex environmental adaptability as-

sessment of MWiR notch filters was carried out sys-

tematically. The results show that after the environ-

mental test, no cracking, delamination and other

morphological features appear on the surface of the

MWiR notch filter film, and the spectral transmis-

sion performance does not change significantly. It

can be seen that the prepared MWiR notch filter

film has excellent spectral performance and com-

plex environmental adaptability.

beam evaporation method, combined with multilay-

er Ge/Al

thin film growth error inversion correc-

tion model. The results show that the material cor-

rection scale factor of Al

thin film tends to

change regularly with the increase of coating time,

which is related to various factors such as coating

vacuum, evaporation state of film material, and

monitoring error. The theoretical and experimental

test results of the MWiR notch filter have good

consistency, and its transmittance is less than 0.3%

within the band range of 4.2 μm~4.5 μm, and its av-

erage transmittance is larger than 95% within the

band ranges of 3.5 μm~4.05 μm and 4.7 μm~5.0

μm. The low surface profile (<0.2λ) modulation of

the MWiR notch filters is successfully achieved by

the pre-setting substrate surface profile method. The

obtained MWiR notch filters have good environ-

mental adaptability and successfully passed the en-

vironmental tests such as adhesion, high temperat-

ure, low temperature, humidity and heat in GJB

2485-95.

4 Conclusion

In this paper, the design and development of

4.3 μm CO

radiation notch filter is realized based

on Needle optimization algorithm, using electron

——中文对照版——

1 引　言

随着红外光电技术的发展，基于目标红外辐

射的被动光电探测与成像系统应用愈加广泛，

对于增强复杂环境动态感知能力发挥着重要作

用

[1-2]

。为了获取更加清晰的红外目标成像，对于

采集到的目标信号要利用多种手段进行调制或滤

波，以抑制背景噪声干扰，提高图像对比度。而干

扰噪声相当一部分来自环境背景，如大气CO

辐

射干扰

[3-5]

，其辐射峰波长位于2.7 μm、4.3 μm和

15 μm，其中4.3 μm处辐射系数值最大，是中波红

外探测成像背景噪声中最严重的辐射源之一。因

此，为了有效压制4.3 μm CO

辐射对红外目标信

号的干扰，以获取清晰、稳定的红外目标成像，需

在原有的红外光学系统中引入滤波光学器件。

目前，国内外普遍采用的方法是红外短波通

滤光片

[6-7]

。然而，红外短波通滤光片在有效去除

4.3 μm CO

辐射干扰的同时，对于大于4.3 μm 的

部分有用信号光也会被一并滤除，致使3.0 μm~

5.0 μm波长区间的中波红外有用信号光无法充分

发挥作用。因此，近年来，对大部分中波红外波长

光具有较高透过率，而对特定波长范围（阻带）内

的光可实现有效截止的陷波滤光片（也称带阻滤

光片或负滤光薄膜）受到了国内外学者的广泛关

注

[8-9]

。例如：西安应用光学研究所王松林等

[10]

采用在单晶锗基底两面分别设计中波红外带通滤

光膜和中波红外负滤光膜的方法，制备了一种光

谱性能优良的双通道带通滤光片；同时其指出，镀

膜材料蒸发角的变化和各层膜厚误差累积，是导

致实验片测试光谱与理论设计光谱有差异的主要

原因。兰州物理研究所的张佰森等

[11]

基于Rug-

ate理论方法，设计了3.8 μm单波长负滤光薄膜

和1.315 μm、3.8 μm 双波长负滤光薄膜，但由于

膜层相对较为复杂，实现难度较大

[12]

；高鹏等

[12]

提出了陷波滤光片的类褶皱设计方法，并分析了

各设计参数对光谱的影响；周晟等

[13]

在Ge基片

912

中国光学（中英文）

第 16 卷

两面分别设计了负滤光膜系和长波截止膜系，组

合形成了包含3.2 μm~3.8 μm和4.9 μm~5.4 μm

两个通道的双色滤光片。此外，依据等效折射率

理论，研究人员还提出了多膜料设计方法

[14]

、厚

度匹配层方法

[15-16]

等，然而，这些方法在实际工程

实现上均存在一定的局限性

[12]

。

针对目前中波红外陷波滤光片设计与精确制

备难的问题，本文首先基于（4H/L）

基本膜系结

构，采用Needle随机插层优化方法，实现了高性

能中波红外陷波滤光片的优化设计；其次，通过建

立多层薄膜生长误差修正模型，有效降低了镀膜

过程中存在的累积厚度误差影响，保证了中波红

外陷波滤光片的精确制备；最后，采用预置基底面

型方法，实现了中波红外陷波滤光片的低面型调

控。此外，本文还对所获得的中波红外陷波滤光

片进行了表面形貌以及复杂环境适用性考核与

评价。

对于所制备的Al

薄膜，受限于薄膜材料透明

区间的影响，其光学常数的变化相对较为复杂。

由图1（b）可知，对于折射率n而言，随着考察波

长从2 μm增加至10 μm，Al

薄膜材料的折射

率呈逐渐降低趋势，其在3.5 μm~5 μm波段区间

的平均大小约为1.55；消光系数k呈相反的变化

趋势，在2.0 μm~6.0 μm波段区间，大小基本为0，

膜层材料吸收损耗的影响基本可以忽略。但随着

波长的进一步增加，k值迅速增大。

中波红外陷波滤光薄膜优化设计过程中，选

择初始膜系为Sub/（4H/L）

/Air，其中H为Ge，L

为Al

。在选定材料和初始膜系后，采用Needle

优化算法，结合多次去薄层和局部再优化处理，最

终优化获得了厚度差异相对较小的28层非规整

膜系。其所对应的理论透射光谱曲线如图2所

示。由图2可知，红外陷波滤光薄膜具有较好的

光谱特性，3.5 μm~4.05 μm和4.7 μm~5.0 μm波段

范围的平均透过率分别约达97.21%、97.75%，在

4.2 μm~4.5 μm波段区间的平均截止透过率约为

0.27%。该中波红外陷波滤光薄膜结构总厚度约

为18.6 μm，根据现有的镀膜工艺及坩埚配置，需

要分3次才能镀制完成，这就对膜层制备工艺控

制精度和稳定性提出了更高要求。

中波红外陷波滤光薄膜理论光谱透过率随入

射角度的变化如图3所示。由图3可知，随着入

射角度的增加，中波红外陷波滤光薄膜的透射

光谱曲线逐渐向短波方向移动，波长4.2 μm和

4.3 μm的截止透射率基本保持不变，均低于0.5%，

4.5 μm截止波长的透射率随着入射角度的增加呈

现不断升高的变化趋势，在入射角度为30°时，透

过率由垂直入射下的0.799%增加至32.17%。随

着入射角度增加至30°，3.5 μm~4.05 μm波段范围

的平均透过率迅速降低，4.7 μm~5.0 μm波段范围

的平均透过率呈先增加后降低的趋势，该现象的

产生与倾斜角度入射情况下膜层等效光学导纳存

在一定失配有关。

2 膜系设计与分析

在3 μm~5 μm中波红外波段区间可选择的

透明薄膜材料有很多种，如Ge、Al

、SiO、ZnS、

YbF

、ZnSe等。由于中波红外陷波滤光薄膜相

对较厚，若采用ZnS、YbF

、ZnSe材料，随着膜层

沉积厚度的增加，将产生较大的应力水平，极易产

生开裂、脱膜等损伤；同时，综合考虑现有镀膜工

艺成熟度、膜层机械性能及其与Ge材料的结合

性能，最终选择Ge、Al

作为中波红外陷波滤

光薄膜结构的高、低折射率膜层材料。薄膜制备

采用电子束蒸发方法。薄膜沉积的起始本底真空

度为1.3×10

Pa，随着镀膜时间的增加，本底真空

−3

度逐渐提高至~6×10

Pa。镀膜前使用APS离子

−4

源对基底表面进行预清洗5 min，沉积工艺参

数如表1所示。所获得的高、低折射率薄膜在

2.0 μm~10.0 μm波段范围内的光学常数（折射率

和消光系数）变化如图1（彩图见期刊电子版）所示。

由图1（a）可知，在2.0 μm~10.0 μm波段范围

内，随着波长的增加，所制备的Ge薄膜光学常数

（折射率n和消光系数k）呈先降低后趋于稳定的

变化趋势，具体而言，膜层材料的折射率

由~4.31逐渐降低至~4.20，并趋于稳定；消光系

数k大小由~0.005逐渐降低为0，其在3.5 μm~

5.0 μm波段区间呈现出了较好的红外透明特性。

3 测试结果与分析

3.1 薄膜反演修正及光谱性能测试

中波红外陷波滤光薄膜镀制过程中，采用石

英晶振监控方式，随着镀膜时间的增加，受多种影

响因素的共同影响（真空度、膜料蒸发状态、监控

第 4 期

SHANG Peng, et al. : Theoretical design and preparation of high performance ......

913

误差等），膜层实际厚度会逐渐偏离标定值，最终

造成实际光谱曲线与理论设计曲线具有较大差

异。因此，如何实现多层红外薄膜的精确反演与

修正则是该红外陷波滤光片能否成功制备的关键。

为此，结合最终优化获得的多层膜系结构，通

过固定比例因子的方式，生长沉积了标准高、低

折射率膜堆结构(LH)

L，其中，(LH)

L标准膜堆

中高、低折射率膜层的物理厚度要尽可能接近膜

系结构中高、低折射率膜层的平均厚度，以降低

标准膜堆与实际膜系结构之间由于膜层厚度差异

对最终结果的影响。理论设计光谱与实测光谱曲

线如图4所示。由图4可知，在所考察的2.0 μm~

6.0 μm波段范围内，理论光谱曲线分布与实测光

谱曲线之间存在较大的差距，而造成该偏差的原

因与实际长时间镀膜过程中镀膜真空度、晶控监

控误差、镀膜室内温度变化、蒸发源状态等多种

因素密切相关。

基于实测光谱曲线，采用OplayerRe软件，拟

合获得了多层薄膜结构相对误差分布情况，如

图5所示。由图5可知，随着镀膜时间的增加，

对于低折射率Al

薄膜而言，第1、3、5、7、9

层的相对误差分别为3.3%、5.9%、9.8%、10.2%、

11.9%，膜层之间的相对变化量呈现先增大后减小

的趋势；对于高折射率Ge薄膜，实际膜层厚度小

于设计膜层厚度，其相对误差为负值，相对误差变

化处于−2.7%~−1.7%之间，膜层之间的最大相对

变化量为1.0%，处于理论拟合误差范围之内。

根据以上所标定的高、低折射率薄膜厚度比

例因子，采用电子束蒸发方法，完成了中波红外陷

波滤光膜全膜系结构制备。在制备过程中要求每

次镀膜工艺状态尽可能保持一致，如起始镀膜真

空度、镀膜时间、装料重量、石英晶振状态等。中

波红外陷波滤光薄膜设计与实测透射光谱曲线如

图6所示。由图6可知，采用修正后的膜层厚度

渐变比例因子，实测透射光谱曲线与理论设计光

谱曲线的变化趋势呈现出了较好的一致性，这也

进一步验证了以上多层薄膜相对误差反演拟合的

准确性。

在中波红外陷波滤光薄膜基片背面镀制中波

红外增透薄膜，双面镀膜后的实测透射光谱曲线，

如图7所示。由图7可知，在4.2 μm~4.5 μm波

段区间，双面镀膜后的中波红外陷波滤光薄膜

平均截止透过率小于0.3%；3.5 μm~4.05 μm及

4.7 μm~5.0 μm波段的平均透过率大于95%，与理

论设计相比，约有2.0%的降低，但仍高于相关产

品的技术指标要求。而该现象的产生与随着镀膜

时间的增加，镀膜过程中Ge料被氧化、沉积膜层

表面粗糙度增大等因素密切有关。

3.2 薄膜表面形貌

图8（彩图见期刊电子版）为锗基底以及镀膜

后的中波红外陷波滤光片表面形貌图。由图8可

知，镀膜前所用锗基底的表面RMS值大小为

0.546 nm，镀膜后膜层表面RMS大小为0.551 nm。

相比而言，镀膜后表面粗糙略有增加，而这与膜层

内应力的释放、膜层材料结构缺陷、外部污染等

诸多因素有关。

此外，本文还通过ZYGO干涉仪测试了镀膜

前后基底表面反射面型大小的变化情况，如图9

（彩图见期刊电子版）所示。其中图9（a）、9（b）为

基底无面型补偿情况下，镀膜前后的面型变化；

图9（c）、9（d）为基底有面型补偿情况下，镀膜

前后的面型变化。由图9（a）和图9（b）可知，由于

所制备的中波红外陷波滤光薄膜较厚，对于镀

膜前面型为PV=0.121λ（其中λ为测试激光波长

632.8 nm）的基片，镀膜后变为1.999λ，已远远超

出相关使用要求。为了有效降低镀膜后基底的面

型变化，避免其对波前的影响，引入预置基底面型

的方法。由图9（c）和图9（d）可知，通过在镀中波

红外陷波滤光薄膜面预置1.990λ面型状态，镀膜

后的面型变为0.191λ，中波红外陷波滤光片的面

型得到了较为显著的改善。

3.3 薄膜环境适应性

根据GJB2485-95 《光学薄膜通用规范》中有

关附着力、高温、低温、湿热等环境试验要求及方

法，系统开展了中波红外陷波滤光片复杂环境适

应性试验。试验结果表明：环境试验后，中波红外

陷波滤光薄膜表面未出现开裂、脱膜、分层等情

况；光谱透射性能未发生显著改变。由此可见，所

制备的中波红外陷波滤光薄膜具有优异的光谱性

能和复杂环境适应性。

4 结　论

本文基于Needle优化算法，采用电子束蒸发

914

中国光学（中英文）

第 16 卷

方法，结合多层Ge/Al

薄膜生长误差反演修正

模型，实现了4.3 μm CO

辐射陷波滤光片的设计

与研制。研究结果表明：随着镀膜时间的增加，

薄膜材料修正比例因子呈规律性变化趋势，

而这与镀膜真空度、膜料蒸发状态、监控误差等

多种因素有关；中波红外陷波滤光片理论与试验

测试结果具有较好的一致性，其在4.2 μm~4.5 μm

References：

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波段区间透过率小于0.3%；3.5 μm~4.05 μm及

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过预置基底面型方法，成功实现了中波红外陷波

滤光片的低面型（<0.2λ）调控。所获得的中波红

外陷波滤光片具有较好的环境适应性，成功通过

了GJB 2485-95中附着力、高温、低温、湿热等环

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第 4 期

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Author Biographics：

Shang Peng (1986—), male, Heze city,

Shandong province, Ph.D., Senior Engin-

eer. He received his Ph.D. degree from the

University of Chinese Academy of Sci-

ences in 2015, mainly engaged in the re-

search of special optical materials and op-

tical thin film design, preparation and test-

ing. E-mail: ********************

尚　鹏（1986—），男，山东菏泽人，博士，

高级工程师，2015 年于中国科学院大

学获得博士学位，主要从事特种光学材

料及光学薄膜设计、制备与测试方面的

研究。E-mail：********************

Cao Bo (1983—), male, Siping city, Jilin

province, B.S., Engineer, received his

B.S. degree from Changchun University

of Science and Technology in 2007,

mainly engaged in the research of opto-

electronic materials, optical processing,

optical thin film and its engineering ap-

plications. E-mail: caobo@guojing-tech.

com

曹　波（1983—），男，吉林四平人，本科，

工程师，2007 年于长春理工大学获学

士学位，主要从事光电材料、光学加工、

光学薄膜及其工程应用方面的研究。

E-mail：**********************

Liu Hua-song (1980—), male, Fuxin city,

Liaoning province, PhD, researcher,

mainly engaged in design, preparation and

characterization technology of the optical

thin film, and optical thin film material

physics. E-mail: **********************

刘华松（1980—），男，辽宁阜新人，博士，

研究员，主要从事光学薄膜设计、制备

与表征技术，光学薄膜材料物理方面研

究。E-mail：**********************

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