Reflecting mirror with adjustable polarization effect for optical module and optical module comprising reflecting mirror

Abstract

The invention provides a reflector with an adjustable polarization effect for an optical module and the optical module comprising the reflector. The reflector comprises a substrate, and a substrate layer, a silver film layer, a metal oxide film layer and a dielectric film layer stack which are sequentially arranged on the substrate, the substrate layer is a chromium film or a titanium film; the metal oxide film layer is made of Al2O3 or TiO2; the dielectric film layer stack is formed by stacking high-refractive-index film layers and low-refractive-index film layers, the structural formula of the dielectric film layer stack is (aHbL) * n cH / AIR, H is the high-refractive-index film layer with the optical thickness of 1 / 4 wavelength, L is the low-refractive-index film layer with the optical thickness of 1 / 4 wavelength, n is the periodicity and an integer larger than or equal to 1, a, b and c are film layer thickness coefficients respectively, and AIR is air. The reflector has excellent reflectivity, separation of P polarized light and S polarized light can be reduced, and the polarization effect can be regulated and controlled.

Description

Technical Field

[0001] The present invention relates to the technical field of optical modules for optical communications, and in particular to a reflector with adjustable polarization effect for an optical module and an optical module containing the reflector. Background Art

[0002] With the advent of the era of big data and AI, a large amount of data needs to be transmitted and processed at high speed. Optical interconnection is one of the main ways of data transmission. Optical interconnection is realized through optical cables, optical modules, etc. Among them, the optical transceiver module is one of the core components of optical communication, which is used to realize the photoelectric conversion of signals. The transmission node is composed of optical modules. Spectral absorption, polarization effect, loss and other factors will affect the signal quality of the overall transmission of the optical module.

[0003] Due to the need for miniaturization and size limitations of optical modules, there is not much space left for building optical paths. Therefore, in optical modules, especially high-speed optical modules, reflectors are often needed to fold and turn the optical path. For example, reflectors are used in optical devices such as Z-Block, rhombus prism, turning prism, and 45° coupling prism commonly used in high-speed optical modules. As an important optical component, reflectors have the functions of efficiently transmitting light energy and turning optical paths. When the signal light is incident on the optical film at an angle, the separation of P polarized light and S polarized light will inevitably occur. The greater the separation of the two polarized lights, the stronger the polarization effect, the greater the phase difference, the more seriously the performance of the optical system will be damaged, and serious polarization effects and excessive optical signal loss will occur, affecting the overall signal transmission function of the optical module. Summary of the invention

[0004] In order to solve the problems existing in the background technology, the present invention provides a reflector with adjustable polarization effect for an optical module and an optical module including the reflector. The technical solution of the present invention to solve the above technical problems is as follows: In a first aspect, the present invention provides a reflector with adjustable polarization effect for an optical module, comprising a substrate and a substrate 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, and the structural formula of the dielectric film layer stack is: (aHbL)*n cH / AIR, wherein 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, c are film layer thickness coefficients respectively, and AIR is air.

[0005] 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.

[0006] According to the above scheme, in the structural formula of the dielectric film layer stack, a=1.54, b=1.92, c=1.54, and n=20.

[0007] According to the above scheme, the thickness of the silver film layer is 50~200nm.

[0008] 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.

[0009] According to the above scheme, the operating wavelength of the reflector is 1250~1350nm.

[0010] According to the above scheme, when the incident light is incident at an angle of 40-50° within the working wavelength range, the average reflectivity of the reflector is 99.98% and the average polarization degree is 0.021%.

[0011] In a second aspect, the present invention provides an optical module including the above-mentioned reflector.

[0012] The reflector of the present invention can be used as the reflector on the rhombus prism used for light beam displacement in the optical module, the reflector on the Z-Block used for light beam folding, and the steering prism in the optical module.

[0013] The beneficial effects of the present invention are as follows: when the reflector of the present invention is incident at a large angle within the target wavelength range, the reflectivity of the reflector can be increased, so that the loss of the signal light when passing through the reflector is reduced, and at the same time, the polarization effect of the signal light during reflection is compensated, and the light wave is controlled in an ideal polarization state, ensuring that the polarization state of the output light remains consistent, and better matching and modulation with the isolator can be performed during the industrial production of the optical module. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 A schematic diagram of the structure of a reflector with adjustable polarization effect for an optical module of the present invention; Figure 2 A reflectivity spectrum of a reflector with adjustable polarization effect for an optical module prepared by the present invention; Figure 3 A polarization degree spectrum of a reflector with adjustable polarization effect for an optical module prepared by the present invention; In the accompanying drawings, the components represented by the reference numerals are listed as follows: 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

[0015] The principles and features of the present invention are described below in conjunction with 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.

[0016] The present invention uses the common wavelength range of 1250~1350nm of the optical module as the target wavelength of the reflector, prepares the reflector, realizes the adjustability of reflectivity, polarization effect and phase, and realizes the regulation of polarization and phase while ensuring the high reflectivity of the film layer.

[0017] 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 substrate 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; The substrate layer 2 is a chromium film or a titanium film; The material of the metal oxide film layer 4 is Al2O3 or TiO2; 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, and the structural formula of the dielectric film layer stack is: (aHbL)*n cH / AIR, wherein 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, c are the film layer thicknesses respectively, and AIR is air.

[0018] As a coating material for reflectors, silver has a stable and high reflectivity in the near-infrared band, and among various metal reflective films, the polarization effect introduced by silver film is the smallest. When light propagates in a metal film, it has a paraxial tendency. When incident at the same incident angle, the polarization effect is smaller than that of a dielectric film. For a metal film, the minimum P polarization reflectivity can be approximately expressed as:

[0019] Where k / n is the ratio of the extinction coefficient to the refractive index, i.e. the optical constant, and the degree of polarization can be calculated by the following formula:

[0020] Where Rs is the reflectivity of s-polarized light, and Rp is the reflectivity of p-polarized light.

[0021] As the optical constant increases, the minimum reflectivity of p-polarized light of the metal film increases and the polarization degree decreases. In the near-infrared region, the polarization effect brought by the metal film is smaller and has a very high reflectivity.

[0022] The substrate layer 2 disposed 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 play a protective role on the one hand, and can also make the silver film layer and the dielectric film layer stack better bonded on the other hand. The dielectric film layer stack can enhance the reflectivity and intensity of the silver film layer, reduce absorption, and further regulate its polarization phase.

[0023] In some specific embodiments, the substrate 1 is quartz glass or glass-ceramics.

[0024] In some specific embodiments, the thickness of the silver film layer 3 is 50-200 nm.

[0025] In some specific 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.

[0026] In some specific 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.

[0027] In some specific embodiments, n is an integer between 18 and 22.

[0028] In some specific embodiments, in the structural formula of the dielectric film layer stack 5 , a=1.54, b=1.92, c=1.54, and n=20.

[0029] In some specific embodiments, the operating wavelength band of the reflector is 1250~1350nm.

[0030] In some specific embodiments, the structure of the reflector is designed according to an incident angle of 45°±5°.

[0031] In some specific embodiments, at an incident angle of 40 to 50° within the working wavelength range, the maximum reflectivity of the reflector is 99.99%, the minimum reflectivity is 99.94%, the average reflectivity is 99.98%, the maximum polarization degree is 0.062%, the minimum is 0.012%, and the average polarization degree is 0.021%.

[0032] The present invention also provides an optical module including the above-mentioned reflector. The two reflectors on the rhombus prism commonly used for light beam displacement in the optical module, the reflector on the Z-Block for light beam folding, and the steering prism in the optical module can all use the reflector of the present invention. It is used in the optical module to fold or redirect the light path. When the incident light is obliquely at a large angle, it has excellent reflectivity and can also reduce the separation of P-polarized light and S-polarized light, regulate the polarization effect, and can be better matched and modulated with the isolator during the industrial production of the optical module.

[0033] The following are specific embodiments.

[0034] In this embodiment, quartz glass BK7 is used as the substrate 1, 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 arranged, the substrate layer 2 is a chromium layer with a thickness of 20 nm, the silver film layer 3 is 150 nm thick, the metal oxide film layer 4 is Al2O3 with a thickness of 20 nm, and the structure of the dielectric film layer stack 5 is: Sub / (aHbL)*n cH / AIR, wherein Sub is a 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, c are film thickness coefficients, n is the number of periods, and AIR is air.

[0035] Designed according to 45°±5° incident angle and 1250~1350nm wavelength range, the coefficients of dielectric film stack are: a=1.54, b=1.92, c=1.54, n=20. Within the wavelength range, its reflection spectrum is as follows: Figure 2 As shown in Figure 1, 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 by the reflector is 0.00087dB, which is much higher than the use requirement. Its polarization curve is shown in Figure 1. 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 working wavelength range, the polarization effect is small enough to be ignored.

[0036] When the reflector of the present invention is incident at a large angle within the target wavelength range, the reflectivity of the reflector can be increased, so that the loss of signal light when passing through the reflector is reduced, and at the same time, the polarization effect of the signal light during reflection is compensated, the light wave is controlled in an ideal polarization state, and the polarization state of the output light is ensured to remain consistent. 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 principle of the present invention should be included in the protection scope 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 base 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, and the structural formula of the dielectric film layer stack is: (aHbL)*n cH / AIR, wherein 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, c are film layer thickness coefficients respectively, and AIR is air.

2. The reflector with adjustable polarization effect for 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 optical module according to claim 1, characterized in that: In the structural formula of the dielectric film layer stack, a=1.54, b=1.92, c=1.54, and n=20.

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

5. The reflector with adjustable polarization effect for optical module according to claim 4, 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.

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

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

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

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