CN213903986U

CN213903986U - Optical fiber MEMS tunable filter

Info

Publication number: CN213903986U
Application number: CN202022864532.3U
Authority: CN
Inventors: 葛益娴; 沈令闻; 张鹏; 顾钦顺
Original assignee: Nanjing University of Information Science and Technology
Current assignee: Nanjing University of Information Science and Technology
Priority date: 2020-12-03
Filing date: 2020-12-03
Publication date: 2021-08-06
Anticipated expiration: 2030-12-03

Abstract

The invention discloses an optical fiber MEMS tunable filter and a manufacturing method thereof, the optical fiber MEMS tunable filter comprises an optical fiber and a sensitive element, the sensitive element sequentially comprises an upper DBR reflector, a polysilicon dielectric film, a lower DBR reflector and silicon nitride from top to bottom, the upper DBR reflector is provided with a metal resistor, the metal resistor comprises a heating resistor and a temperature measuring resistor, the optical fiber comprises an incident optical fiber and an emergent optical fiber, the incident optical fiber is arranged on one side of the upper DBR reflector, the emergent optical fiber is arranged on one side of the lower DBR reflector, the emergent optical fiber is fixed on a silicon substrate, the upper DBR reflector, the polysilicon dielectric film and the lower DBR reflector form a Fabry-Perot cavity, the refractive index of the polysilicon dielectric film is changed by directly heating the heating resistor, the optical path of the incident optical fiber is changed, and tuning filtering of light is realized. The invention has the advantages of batch production, small volume, simple manufacturing method and low cost, and the manufactured sensor has the advantage of quick tuning.

Description

Optical fiber MEMS tunable filter

Technical Field

The utility model relates to an optic fibre MEMS filtering technology field, an optic fibre MEMS tunable filter specifically says so.

Background

The optical filter is a phase filtering structure with phase response changing along with frequency, separates signal light with different wavelengths in a frequency domain or a space domain, has real-time selectivity on optical signals with specific frequencies, has very important application in optical fiber communication and optical sensing systems, and has extremely important value for the development of all-optical networks. The fiber MEMS sensor is very practical in many application fields due to the characteristics of micro size, wide response frequency band, high sensitivity, low cost and the like. Compared with other traditional sensors, the optical fiber MEMS sensor has stronger adaptability under severe environments such as strong electromagnetic interference, high temperature and the like. The MEMS device is suitable for large-scale integrated production, so that the production cost of the sensor is greatly reduced. Fabry-perot interferometers modulate the amplitude and phase of an incident light wave. The F-P standard is various, one of the F-P standard is composed of two reflectors, light enters an F-P cavity through a transmission optical fiber, and is reflected back and forth for multiple times between the reflectors to cause phase difference between light beams so as to form interference light beams, and the light at an emergent end receives multiple interference fringes or realizes the change of the phase difference between the light beams by changing the distance between resonant cavities, so that the comb spectrum of the interferometer is adjusted. However, the existing F-P resonant cavity type filters have the problems of high price, low tuning speed and the like.

Disclosure of Invention

The utility model aims at the not enough among the above-mentioned prior art, provide an optic fibre MEMS tunable filter.

The utility model aims at realizing through the following technical scheme:

an optical fiber MEMS tunable filter comprises an optical fiber and a sensitive element, wherein the sensitive element sequentially comprises an upper DBR reflector, a polysilicon dielectric film, a lower DBR reflector and silicon nitride from top to bottom, the upper DBR reflector is provided with a metal resistor, the metal resistor comprises a heating resistor and a temperature measuring resistor, the optical fiber comprises an incident optical fiber and an emergent optical fiber, the incident optical fiber and the emergent optical fiber are symmetrically arranged on two sides of the sensitive element, the incident optical fiber is arranged on one side of the upper DBR reflector, the emergent optical fiber is arranged on one side of the lower DBR reflector, the emergent optical fiber is fixed on a silicon substrate, the incident optical fiber and the emergent optical fiber are arranged on a straight line, the upper DBR reflector, the polysilicon dielectric film and the lower DBR reflector form a Fabry-Perot cavity, the refractive index of the polysilicon dielectric film is changed through the direct heating of the heating resistor, the optical path of the incident optical fiber is changed, and realizing tuned filtering of light.

The utility model discloses in the further design, above-mentioned DBR speculum and lower DBR speculum all have four-layer structure, respectively by the SiO that lays in turn₂Dielectric film and Poly-Si/SiO₂The upper DBR reflector and the lower DBR reflector are in contact with the polysilicon dielectric film and are all SiO₂And (3) a dielectric film.

In a further embodiment of the present invention, the SiO layer is formed of a material selected from the group consisting of₂Dielectric film and Poly-Si/SiO₂The dielectric films are all made by low pressure chemical vapor deposition LPCVD growth, and the optical thickness of each layer is one quarter of the incident wavelength.

In a further design of the present invention, the optical thickness of the polysilicon dielectric film is half wavelength.

The utility model discloses in the further design, above-mentioned metal resistance material is Au or Cr, and cyclic annular distributes, and metal resistance has four, and two are heating resistor, and two are the measuring temperature resistance.

The utility model discloses following outstanding beneficial effect has:

the utility model discloses MEMS tunable filter adopts optical signal to measure, has avoided electromagnetic interference.

The sensor adopts the polysilicon dielectric film as the Fabry-Perot cavity, and because the polysilicon has larger thermo-optic coefficient and heat dissipation speed, the response time of the polysilicon tunable filter utilizing the thermo-optic effect can reach microsecond order, thereby realizing rapid tuning. The utility model discloses a method processes the preparation sensor through the MEMS technique, can realize batch production. The sensitive element of the filter is connected with the optical fiber by adopting an anodic bonding technology, so that the temperature influence caused by a glue connection mode is avoided. The utility model discloses the method has batch production, small, manufacturing method is simple, advantage with low costs, and the sensor of preparation has the advantage that can tune fast, can satisfy the filtering requirement under the general condition.

Drawings

FIG. 1 is a schematic structural diagram of an optical fiber MEMS tunable filter in an embodiment;

FIG. 2 is a schematic structural view of a sensor in the embodiment;

FIG. 3 is a process flow diagram of the fabrication of the tunable filter for fiber MEMS according to the embodiment;

FIG. 4 is a schematic diagram of the resistor layout on the upper DBR mirror in one embodiment;

FIG. 5 is a device test diagram of the fiber MEMS tunable filter in the embodiment;

in the figure, 1-incident optical fiber, 2-emergent optical fiber, 3.1-upper DBR reflector, 3.2-lower DBR reflector, 4-polysilicon dielectric film, 5-silicon nitride, 6-silicon substrate, 7-heating resistor, 8-temperature measuring resistor, 9-wide light source, 10-jumper, 11-tunable filter and 12-spectrum analyzer.

Detailed Description

The present invention will be further explained with reference to the drawings and the embodiments.

Example 1

Referring to the attached

drawings

1, 2 and 4, an optical fiber MEMS tunable filter comprises an optical fiber and a sensitive element, wherein the sensitive element sequentially comprises an upper DBR reflector 3.1, a polysilicon dielectric film 4, a lower DBR reflector 3.2 and silicon nitride 5 from top to bottom, a resistor is arranged on the upper DBR reflector 3.1, the optical fiber comprises an incident optical fiber 1 and an emergent optical fiber 2 which are symmetrically arranged at two sides of the sensitive element, the incident optical fiber 1 is arranged at one side of the upper DBR reflector 3.1, the emergent optical fiber 2 is arranged at one side of the lower DBR reflector 3.2, the incident optical fiber 1 and the emergent optical fiber 2 are arranged on a straight line, the upper DBR reflector 3.1, the polysilicon dielectric film 4 and the lower DBR reflector 3.2 form a Fabry-Perot cavity, the refractive index of the polysilicon DBR dielectric film 4 is changed by directly heating a metal heating resistor 7, the optical path of the incident light is changed, and tuning and filtering of the light is realized.

Referring to FIG. 2, the upper DBR mirror 3.1 and the lower DBR mirror 3.2 each have a four-layer structure, each consisting of alternately arranged SiO₂Dielectric film and Poly-Si/SiO₂The upper DBR mirror 3.1 and the lower DBR mirror 3.2 are in contact with the polysilicon dielectric film 4 and are both made of SiO₂And (3) a dielectric film. SiO 2₂Dielectric film and Poly-Si/SiO₂The dielectric films are all made by LPCVD growth, the optical thickness of each layer is the same, and the thickness is a quarter wavelength. The optical thickness of the polysilicon dielectric film 4 is half a wavelength. The incident wavelength is between 1510nm and 1560 nm.

Referring to fig. 4, four resistors located in the upper DBR mirror are distributed annularly, two of the resistors are heating resistors 7, and the refractive index of the polysilicon dielectric film 4 is changed by heating; the other two are temperature measuring resistors 8 for measuring the heating temperature.

The utility model discloses a manufacturing method of MEMS tunable filter, including following step: with reference to figure 3 of the drawings,

1) double-sided thermal oxidation on a double-sided polished silicon substrate 6, depositing a layer of silicon nitride 5Si on top of the silicon substrate 6 by low pressure chemical vapor deposition LPCVD₃N₄The passivation layer is used for KOH anisotropic wet etching silicon;

2) sequential growth of Poly-Si/SiO by LPCVD₂Dielectric film of (2) and SiO₂Dielectric film, and repeating once to form the lower DBR mirror.

3) And growing a polysilicon dielectric film 4 with the optical thickness of half wavelength on the lower DBR reflector by an LPCVD method, wherein the dielectric film is a Fabry-Perot cavity.

4) Respectively growing SiO on the polysilicon dielectric film 4 by using LPCV₂Dielectric film and Poly-Si/SiO₂And repeating once to form the upper DBR mirror.

5) And photoetching the back surface of the mask silicon substrate 6, etching the unmasked silicon substrate 6 by using deep RIE, removing redundant photoresist on the silicon substrate 6, and forming a pit exposing the silicon nitride 5 layer for vertically placing and fixing the emergent optical fiber 2.

6) 4 resistors are fixed on the upper DBR reflector, two of the resistors are heating resistors 7, the refractive index of the polysilicon dielectric film 4 is changed through heating, and the other two resistors are temperature measuring resistors 8. The resistor is made of a metal film, the metal material may be Au or Cr, and the resistor is formed in a ring shape.

7) And the incident light and the emergent optical fiber 2 are symmetrically fixed on two sides of the sensitive element by adopting an anodic bonding technology.

The LPCVD in the above manufacturing method can also be PECVD using plasma enhanced chemical vapor deposition, but the effect is slightly worse than the LPCVD.

According to the MEMS tunable filter obtained through the processing steps, the polycrystalline silicon dielectric film 4 between the upper and lower high-reflectivity DBR reflectors forms a Fabry-Perot cavity, the temperature is changed through the heating resistor 7, the refractive index of the polycrystalline silicon dielectric film 4 is changed, the optical path of incident light is changed, and the transmission phase difference of interference light in the Fabry-Perot cavity is changed so as to tune the required wavelength.

During device processing, a NIKON metallographic microscope and a Veeco profiler are used for measuring the root-mean-square roughness of the silicon chip corrosion surface before and after oxidation polishing. The fiber MEMS tunable filter designed by the patent adopts a measuring system as shown in figure 5 for measurement.

(1) Using the wide light source 9 as an output response, the wide light source 9 is connected to the entrance fiber 1 by a jumper 10, and the light is perpendicularly incident on the tunable filter 11 through the entrance fiber 1.

(2) The outgoing optical fiber 2 is connected to the spectrum analyzer 12 via a jumper wire 10, and light is output from the outgoing optical fiber 2 and received by the spectrum analyzer 12, so that a broadband spectrum response is obtained.

Above is the utility model discloses a preferred embodiment, all rely on the utility model discloses the change that technical scheme made, produced functional action does not surpass the utility model discloses during technical scheme's scope, all belong to the utility model discloses a protection scope.

Claims

1. The utility model provides a tunable filter of optic fibre MEMS which characterized in that, includes optic fibre and sensing element, the sensing element includes DBR speculum (3.1), polycrystalline silicon dielectric film (4), DBR speculum (3.2) and silicon nitride (5) down from last in proper order, be equipped with metal resistance on last DBR speculum (3.1), above-mentioned metal resistance includes heating resistor (7) and temperature measuring resistor (8), optic fibre includes incident fiber (1) and exit fiber (2), and the symmetry is located the sensing element both sides, incident fiber (1) are located go up DBR speculum (3.1) one side, and exit fiber (2) are located DBR speculum (3.2) one side down, and exit fiber (2) are fixed on silicon substrate (6), and incident ray and exit fiber (2) are on a straight line, go up DBR speculum (3.1), The polysilicon dielectric film (4) and the lower DBR reflector (3.2) form a Fabry-Perot cavity, the refractive index of the polysilicon dielectric film (4) is changed through the direct heating of the heating resistor (7), the optical path of incident light is changed, and the tuning filtering of the light is realized.

2. Fiber MEMS tunable filter according to claim 1, characterized in that the upper DBR mirror (3.1) and the lower DBR mirror (3.2) both have a four-layer structure, respectively composed of alternately laid SiO₂Dielectric film and Poly-Si/SiO₂The upper DBR reflector (3.1) and the lower DBR reflector (3.2) are in contact with the polysilicon dielectric film (4) and are all made of SiO₂And (3) a dielectric film.

3. The fiber MEMS tunable filter of claim 2, wherein the SiO is₂Dielectric film and Poly-Si/SiO₂The dielectric films are all made by low pressure chemical vapor deposition LPCVD growth, and the optical thickness of each layer is one quarter of the incident wavelength.

4. The fiber MEMS tunable filter according to claim 1, wherein the optical thickness of the polysilicon dielectric film (4) is half wavelength.

5. The fiber MEMS tunable filter of claim 1, wherein the metal resistors are four, two heating resistors (7) and two measuring temperature resistors.