A polarization effect adjustable mirror for an optical module and an optical module comprising the same

Abstract

The application provides a polarization-effect-adjustable mirror for an optical module and an optical module comprising the same, the mirror comprising a substrate and a substrate layer, a silver film layer, a metal oxide film layer and a dielectric film layer stack arranged on the substrate in sequence; the substrate layer is a chromium film or a titanium film; the material of the metal oxide film layer is Al2O3 or TiO2; the dielectric film layer stack is formed by stacking a high-refractive-index film layer and a low-refractive-index film layer, and the structure formula of the dielectric film layer stack is (aHbL)*n cH / AIR, wherein H is a high-refractive-index film layer with a 1 / 4 wavelength optical thickness, L is a low-refractive-index film layer with a 1 / 4 wavelength optical thickness, n is a period number, n is an integer greater than or equal to 1, a, b and c are film layer thickness coefficients respectively, and AIR is air. The mirror has excellent reflectivity, can reduce the separation of P-polarized light and S-polarized light, and can adjust and control the polarization effect.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of optical communication optical modules, and particularly relates to a polarization effect adjustable mirror for optical modules and an optical module comprising the same. BACKGROUND

[0002] With the advent of the big data and AI era, a large amount of data needs to be transmitted and processed at high speed, and optical interconnection is one of the main ways of data transmission. Optical interconnection is realized through optical cables, optical modules and the like. An optical transceiver module is one of the core devices of optical communication, and is used to realize optical-electric conversion of signals. Transmission nodes are composed of optical modules. Factors such as optical spectrum absorption, polarization effect and loss will affect the overall signal quality of the optical module.

[0003] Due to the need for miniaturization and size constraints, there is not much space left for optical path construction in optical modules. Therefore, mirrors are often used in optical modules, especially high-speed optical modules, to fold and turn the optical path. For example, mirrors are used in optical devices such as Z-Block, rhomboid prism, turning prism and 45° coupling prism commonly used in high-speed optical modules. As an important optical element, the mirror has the functions of high-efficiency transmission of optical energy and turning of optical path. When signal light is obliquely incident on an optical thin film, it will inevitably produce separation of P-polarized light and S-polarized light. The greater the separation of the two polarized lights, the stronger the polarization effect and the greater the phase difference. The performance of the optical system is more seriously damaged, which will cause serious polarization effect, excessive optical signal loss and other problems, affecting the overall signal transmission function of the optical module. SUMMARY

[0004] To solve the problems in the background art, the present application provides a polarization effect adjustable mirror for optical modules and an optical module comprising the same.

[0005] The technical solution of the present application to solve the above technical problems is as follows:

[0006] In a first aspect, the present application provides a polarization effect adjustable mirror for optical modules, comprising a substrate and a substrate layer, a silver film layer, a metal oxide film layer and a dielectric film layer stack arranged in sequence on the substrate.

[0007] The substrate layer is a chromium film or a titanium film;

[0008] The material of the metal oxide film layer is Al2O3 or TiO2;

[0009] The medium film layer stack is formed by stacking high refractive index film layers and low refractive index film layers, and the structural formula of the medium film layer stack is (aHbL)*n cH / AIR, wherein H is a high refractive index film layer with a 1 / 4 wavelength optical thickness, L is a low refractive index film layer with a 1 / 4 wavelength optical thickness, n is the number of periods, n is an integer greater than or equal to 1, a, b, and c are film layer thickness coefficients, and AIR is air.

[0010] According to the above scheme, the material of the high refractive index film layer is Ta2O5, and the material of the low refractive index film layer is SiO2.

[0011] According to the above scheme, in the structural formula of the medium film layer stack, a=1.54, b=1.92, c=1.54, and n=20.

[0012] According to the above scheme, the thickness of the silver film layer is 50-200 nm.

[0013] According to the above scheme, the thickness of the substrate layer is 8-25 nm, and the thickness of the metal oxide film layer is 5-20 nm.

[0014] According to the above scheme, the operating wavelength of the mirror is 1250-1350 nm.

[0015] According to the above scheme, the average reflectivity of the mirror is 99.98% and the average polarization degree is 0.021% when the mirror is incident at an incident angle of 40-50° within the operating wavelength range.

[0016] In a second aspect, the present application provides an optical module comprising the mirror.

[0017] The mirror on a rhomboid prism for beam displacement in an optical module, the mirror for beam folding on a Z-Block, and a turning prism in an optical module can all use the mirror of the present application.

[0018] The mirror of the present application can increase the reflectivity of the mirror when the mirror is incident at a large angle within the target wavelength range, so that the loss of signal light when passing through the mirror is reduced, and the polarization effect of the signal light when reflected is compensated, the light wave is controlled in the ideal polarization state, and the polarization state of the outgoing light is kept consistent, which can better match and modulate the isolator during the industrial production of the optical module. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 FIG. 1 is a schematic diagram of a mirror structure with adjustable polarization effect for an optical module of the present application;

[0020] Figure 2 FIG. 5 is a reflectivity spectrum of the mirror with adjustable polarization effect for an optical module prepared by the present application;

[0021] Figure 3 Polarization degree spectrum of the reflector with adjustable polarization effect for the optical module prepared by the present invention;

[0022] In the accompanying drawings, the components represented by the reference numerals are as follows:

[0023] 1. Substrate, 2. Underlayer, 3. Silver film layer, 4. Metal oxide film layer, 5. Dielectric film layer stack, 51. High refractive index film layer, 52. Low refractive index film layer. DETAILED DESCRIPTION

[0024] The principles and features of the present invention are described below with reference to the accompanying drawings and specific embodiments. The examples given are only used to explain the present invention and are not used to limit the scope of the present invention.

[0025] The present invention uses the common wavelength range of 1250~1350nm of the optical module as the target wavelength of the reflector, and prepares a reflector to achieve the controllable reflectivity, polarization effect and phase, while ensuring the high reflectivity of the film layer, realizing the control of polarization and phase.

[0026] like Figure 1 As shown, the present invention provides a reflector with adjustable polarization effect for an optical module, comprising a substrate 1 and a backing layer 2, a silver film layer 3, a metal oxide film layer 4 and a dielectric film layer stack 5 sequentially arranged on the substrate;

[0027] The substrate layer 2 is a chromium film or a titanium film;

[0028] The material of the metal oxide film layer 4 is Al2O3 or TiO2;

[0029] The dielectric film layer stack 5 is formed by stacking a high refractive index film layer 51 and a low refractive index film layer 52. The structural formula of the dielectric film layer stack is: (aHbL)*n cH / AIR, where H is a high refractive index film layer with an optical thickness of 1 / 4 wavelength, L is a low refractive index film layer with an optical thickness of 1 / 4 wavelength, n is the number of periods, n is an integer ≥1, a, b, and c are the film layer thicknesses respectively, and AIR is air.

[0030] Silver, as a coating material for reflectors, has a stable and high reflectivity in the near-infrared band. Among various metal reflective films, silver films introduce the smallest polarization effect. Light propagates paraxially in metal films, and at the same incident angle, the polarization effect is smaller than that of dielectric films. For metal films, the minimum P-polarization reflectivity can be approximately expressed as:

[0031]

[0032] Where k / n is the ratio of the extinction coefficient to the refractive index, i.e., the optical constant. The degree of polarization can be calculated using the following formula:

[0033]

[0034] wherein Rs is the reflectivity of s-polarized light, and Rp is the reflectivity of p-polarized light.

[0035] As the optical constant increases, the minimum reflectivity of p-polarized light of the metal film increases, and the degree of polarization decreases. In the near-infrared region, the polarization effect caused by the metal film is smaller, and the reflectivity is very high.

[0036] The substrate layer 2 arranged between the silver film layer 3 and the substrate 1 can improve the bonding force between the silver film layer 3 and the substrate 1. The metal oxide film layer can protect the silver film layer on one hand, and on the other hand, can make the silver film layer better combined with the dielectric film stack. The dielectric film stack can enhance the reflectivity and intensity of the silver film layer, reduce absorption, and further control the phase of polarization.

[0037] In some embodiments, the substrate 1 is quartz glass or microcrystalline glass.

[0038] In some embodiments, the thickness of the silver film layer 3 is 50-200 nm.

[0039] In some embodiments, the thickness of the substrate layer 2 is 8-25 nm, and the thickness of the metal oxide film layer 4 is 5-20 nm.

[0040] In some embodiments, the material of the high-refractive-index film layer 51 is Ta2O5, and the material of the low-refractive-index film layer 52 is SiO2.

[0041] In some embodiments, n is an integer between 18 and 22.

[0042] In some embodiments, in the structural formula of the dielectric film stack 5, a=1.54, b=1.92, c=1.54, and n=20.

[0043] In some embodiments, the working wavelength range of the mirror is 1250-1350 nm.

[0044] In some embodiments, the mirror is designed at an incident angle of 45°±5°.

[0045] In some embodiments, at an incident angle of 40-50° in the working wavelength range, the maximum reflectivity of the mirror is 99.99%, the minimum reflectivity is 99.94%, the average reflectivity is 99.98%, the maximum degree of polarization is 0.062%, the minimum degree of polarization is 0.012%, and the average degree of polarization is 0.021%.

[0046] The present invention also provides an optical module including the aforementioned reflector. The reflector of the present invention can be used in the two reflectors on the rhombus prism commonly used for beam displacement in optical modules, the reflector on the Z-Block used for beam folding, and the steering prism in optical modules. The reflector is used in optical modules to fold or redirect the light path. At high-angle oblique incidence, it exhibits excellent reflectivity while reducing the separation of P-polarized and S-polarized light, regulating the polarization effect. This allows for better matching and modulation with isolators during industrial production of optical modules.

[0047] The following are specific examples.

[0048] In this embodiment, a quartz glass BK7 substrate 1 is used, and a substrate layer 2, a silver film layer 3, a metal oxide film layer 4, and a dielectric film layer stack 5 are sequentially provided. The substrate layer 2 is a chromium layer with a thickness of 20 nm, the silver film layer 3 is 150 nm thick, and the metal oxide film layer 4 is Al2O3 with a thickness of 20 nm. The structure of the dielectric film layer stack 5 is: Sub / (aHbL)*n cH / AIR, where Sub is the glass substrate on which the substrate layer 2, the silver film layer 3, and the metal oxide film layer 4 have been plated, H and L represent high and low refractive index film layers with an optical thickness of 1 / 4 wavelength, respectively, a, b, and c are film thickness coefficients, n is the number of periods, and AIR is air.

[0049] Designed based on an incident angle of 45°±5° and a wavelength range of 1250~1350nm, the coefficients of the dielectric film stack are: a=1.54, b=1.92, c=1.54, and n=20. Within the operating wavelength range, its reflection spectrum is shown in the figure below. Figure 2 As shown, the maximum reflectivity of the reflector is 99.99%, the minimum reflectivity is 99.94%, and the average reflectivity is 99.98%. The loss after one reflection through the reflector is 0.00087dB, which is much higher than the use requirement. Its polarization curve is shown in Figure 3 As shown in the figure, the maximum polarization degree is 0.062%, the minimum is 0.012%, and the average polarization degree is 0.021%. It can be seen that within the operating wavelength range, the polarization effect is small enough to be ignored.

[0050] The reflector of the present invention can increase the reflectivity of the reflector when the incident light is obliquely incident at a large angle within the target wavelength range, thereby reducing the loss of the signal light when passing through the reflector. At the same time, it compensates for the polarization effect of the signal light during reflection, controls the light wave in an ideal polarization state, and ensures that the polarization state of the output light remains consistent.

[0051] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A reflector with adjustable polarization effect for an optical module, characterized in that: It comprises a substrate and a backing layer, a silver film layer, a metal oxide film layer and a dielectric film layer stack sequentially arranged on the substrate; The substrate layer is a chromium film or a titanium film; The material of the metal oxide film layer is Al2O3 or TiO2; The dielectric film layer stack is formed by stacking a high-refractive index film layer and a low-refractive index film layer. The structural formula of the dielectric film layer stack is: (aHbL)*n cH / AIR, where H is a high-refractive index film layer with an optical thickness of 1 / 4 wavelength, L is a low-refractive index film layer with an optical thickness of 1 / 4 wavelength, n is the number of periods, n is an integer ≥1, a, b, and c are film layer thickness coefficients, respectively, AIR is air, a=1.54, b=1.92, c=1.54, and n=20.

2. The reflector with adjustable polarization effect for an optical module according to claim 1, characterized in that: The material of the high refractive index film layer is Ta2O5, and the material of the low refractive index film layer is SiO2.

3. The reflector with adjustable polarization effect for an optical module according to claim 1 or 2, characterized in that: The thickness of the silver film layer is 50-200 nm.

4. The reflector with adjustable polarization effect for an optical module according to claim 3, characterized in that: The thickness of the substrate layer is 8-25 nm, and the thickness of the metal oxide film layer is 5-20 nm.

5. The reflector with adjustable polarization effect for an optical module according to claim 1, characterized in that: The operating wavelength of the reflector is 1250-1350 nm.

6. The reflector with adjustable polarization effect for an optical module according to claim 5, characterized in that: When incident at an incident angle of 40-50° within the operating wavelength range, the average reflectivity of the reflector is 99.98% and the average polarization degree is 0.021%.

7. An optical module, characterized in that: A reflector comprising the reflector according to any one of claims 1 to 6.

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