Quantum measurement system optical filter with high precision and controllable broadband characteristic and preparation method thereof

Abstract

The invention discloses development of a quantum measurement system optical filter with high precision and controllable broadband characteristic, the optical filter comprises a glass substrate and two reflecting film layers, the glass substrate is formed by classical polishing, the polishing precision can be controlled within 0.5 mu m, the parallelism can be controlled within 1 second, the surface type can be controlled above 1 / 20 lambda, interference is effectively formed on two surfaces of glass, and the quality of the optical filter is improved. The reflecting film layer adopts a double-surface symmetrical design, the film layers on the two sides of the glass substrate are symmetrically arranged and comprise Ta2O5 and SiO2, and the Ta2O5 film layers and the SiO2 film layers are alternately overlapped; the invention further discloses a manufacturing method of the optical filter of the quantum measurement system. The manufacturing method comprises the steps of substrate grinding, substrate polishing, substrate cleaning, substrate testing, substrate clamping, substrate coating, disc feeding and cutting and small particle testing. According to the invention, the processing cost is effectively reduced, the processing period is short, the Ra can be controlled within 0.001 [mu] m, the insertion loss is low, the isolation degree is high, and the half width is adjustable and controllable.

Description

Technical Field

[0001] The present invention relates to the technical field of quantum measurement, and particularly to a filter for a quantum measurement system with high precision and controllable broadband characteristics and a preparation method thereof. Background Art

[0002] With the rapid development of the optical communication field, the expansion of communication capacity has followed. Wavelength division multiplexing (WDM) and dense wavelength division multiplexing (DWDM) have good technical advantages and good economy, which can not only meet the explosive increase in market demand but also have broad development prospects, so they have attracted more and more attention.

[0003] Based on the rapid development of WDM and DWDM, an optical etalon is one of the interference optical devices. It has the function of an optical resonator, and its transmittance changes periodically with the laser frequency. At resonance, the reflections from the two surfaces undergo destructive interference, which can make optical signals with a certain wavelength interval transmit and other wavelengths reflect, equivalent to a set of elementary filters; it can also be used as a kind of comb filter and is widely used in quantum measurement devices. In addition, the reflectivity of the optical etalon surface can be calculated from the refractive index discontinuity between the etalon material and air (Fresnel reflection) or adjusted by using a dielectric coating. By increasing the reflectivity, the finesse can be freely increased, and the resonance peak can be sharpened without reducing the free spectral range to separate monochromatic light of a single wavelength. Summary of the Invention

[0004] The main technical problem to be solved by the present invention is that the glass is mainly polished in a classical manner, the polishing accuracy can be controlled within 0.5 μm, the parallelism can be controlled within 1″, and the polishing surface shape can be controlled above 1 / 20λ, effectively enabling interference to be formed on both sides of the glass substrate. The reflective film layer adopts a double-sided symmetric design, and the reflectivity can be freely adjusted to control the finesse of the product, and a single wavelength can be separated out.

[0005] To solve the above technical problem, a technical solution adopted by the present invention is: to provide a filter for a quantum measurement system with high precision and controllable broadband characteristics, including a glass substrate, the glass substrate is polished in a classical manner, the polishing accuracy is controlled within 0.5 μm, the parallelism is controlled within 1″, the polishing surface shape is controlled above 1 / 20λ, effectively enabling interference to be formed on both sides of the glass, and reflective film layers are symmetrically arranged on both sides of the glass substrate, and the reflective film layer is composed of Ta 2 O 5 film layer and SiO 2 film layer are alternately stacked.

[0006] Preferably, the film layer structure of the reflective film layer from the side of the glass substrate is nL(HL) N (HL) 1 (HnL)1 Substrate (nLH) 1 (LH) 1 (LH) N nL, where H represents Ta 2 O 5 Film layer, L represents SiO 2 Film layer, N represents the number of deposition times, n can be variable from 0.1 to 1.0 according to the actual reflectivity requirements, but the symmetry of the double-sided film system needs to be ensured, and the reflectivity of the reflective layer can be freely adjusted according to use to control FWHM.

[0007] Preferably, the glass substrate controls FSR by substrate thickness, and adjusts the substrate thickness according to the actual use situation to meet the FSR requirements.

[0008] The present invention also provides a preparation method for a filter of a quantum measurement system, including the following steps: substrate polishing - substrate cleaning - substrate clamping - substrate coating - substrate testing - upper plate cutting.

[0009] Preferably, the above substrate polishing includes the following steps: polishing both sides of the glass substrate through a polishing device - measuring the polished thickness of the substrate through a physical instrument - measuring the surface shape and parallelism of the substrate through a laser interferometer - measuring FSR through an optical measurement to meet the requirements.

[0010] Preferably, before polishing both sides of the glass substrate, the surface shape of the asphalt disk is corrected by using an asphalt disk low polishing process, and whether the standard piece polishing test meets the polishing surface shape requirement of 1 / 20λ is tested.

[0011] Preferably, when polishing both sides of the glass substrate, an nm-level polishing liquid is used, and the surface roughness Ra of the glass substrate < 10nm; at the same time, a high-precision measuring device is used to test while polishing, and the polishing thickness accuracy is controlled within 0.5um.

[0012] Preferably, the above substrate coating process is to place the glass substrate on an umbrella rack in a clean room, transport it to the coating equipment by a special lifting table, and in a vacuum environment, use a light cell coating equipment to coat a beam splitting film on one side of the glass substrate, and then coat a beam splitting film with the same thickness on the other side.

[0013] Preferably, in the above substrate coating process, the vacuum coating equipment is heated and baked to 220°C, kept warm for 2 hours, and the vacuum degree reaches below 8.0E-4Pa.

[0014] Preferably, in the above substrate coating furnace discharging process, the glass plate is cooled during the deposition of the double-sided reflective film, and the door is opened after cooling to below 120°C.

[0015] The beneficial effects of the present invention are:

[0016] Although classical polishing methods have been used in the production of filters for quantum measurement systems at home and abroad in the early stage, the processing process is simple and rough, the production cost is high, the processing cycle is long, and Ra can only be controlled at 0.02um, with a large IL. The present invention changes the design concept, deeply explores on the basis of the existing classical polishing method, and combines factors such as process control, film structure design, and control of key coating conditions to obtain a filter for a quantum measurement system. This not only effectively reduces the processing cost, but also has a short processing cycle. The surface roughness Ra can be controlled within 0.001um, and the optical measurement FSR can meet the requirement of 100G controllability, with an accuracy meeting the requirement of ±0.5G. At the same time, the film layer adopts a symmetric design with IL < 0.5db, low insertion loss, and high isolation. The reflectivity of the reflective layer can be freely adjusted according to use to control the FWHM to be less than 0.1nm, and the half-width is adjustable and controllable, which has very good technical promotion value and market promotion value and improves market competitiveness. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 is a schematic structural diagram of a filter for a high-precision and broadband characteristic controllable quantum measurement system of the present invention;

[0018] Figure 2 is the free spectral range FSR situation of the glass substrate in a filter for a high-precision and broadband characteristic controllable quantum measurement system prepared by the present invention;

[0019] Figure 3 is the FSR situation of a filter for a high-precision and broadband characteristic controllable quantum measurement system prepared by the present invention cut into small grains for testing;

[0020] Figure 4 is the broadband characteristic FWHM of a filter for a high-precision and broadband characteristic controllable quantum measurement system prepared by the present invention cut into small grains for testing. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0021] The following elaborates on the preferred embodiments of the present invention in detail so that the advantages and features of the present invention can be more easily understood by those skilled in the art, thereby making the protection scope of the present invention more clearly defined.

[0022] Embodiment:

[0023] The present invention provides a filter for a high-precision and broadband characteristic controllable quantum measurement system, and the structure is as Figure 1 shown. Reflective film layers are symmetrically coated on both sides of the glass substrate. The basic structure of the filter has no obvious difference from the industry, mainly in the acquisition method, parameter control, and design and control of each preparation process.

[0024] The method for obtaining the filter of the high-precision and broadband characteristic controllable quantum measurement system in the present invention, the first step is the polishing of the glass substrate, specifically:

[0025] First, adopt the classical asphalt disk low polishing process to correct the surface profile of the asphalt disk before substrate polishing, and test whether the standard wafer polishing meets the requirements of the polishing surface profile to reach 1 / 20λ.

[0026] Secondly, polish both sides of the glass substrate through the above polishing equipment. When polishing, use nm-level polishing liquid, and the surface roughness Ra of the glass substrate < 10nm; at the same time, use high-precision measurement equipment to test while polishing, and control the polishing thickness accuracy within 0.5um; at the same time during the polishing process, use a laser interferometer to measure the surface profile and parallelism of the glass substrate, control the polishing parallelism within 1″, and control the polishing surface profile above 1 / 20λ, effectively forming interference on both sides of the glass. After reaching the above indicators, unload the disk; in this embodiment, according to this polishing method, the obtained glass substrate has a thickness of 1.0248mm and the size of the glass substrate is 20mm * 20mm.

[0027] After unloading the disk, for the obtained glass substrate above, use the optical measurement method to test the product transmittance, specifically project a beam of laser light source onto the glass substrate, receive it on the opposite side and conduct optical tests, and use the self-developed software to calculate the FSR, and the accuracy is as Figure 2 shown, control the FSR through optical measurement to meet the requirement of 100G controllable, and the accuracy meets the requirement of ±0.5G. After meeting the FSR standard, transfer to the next process.

[0028] Then, ultrasonically clean the glass substrate polished on both sides, dry it with a hot air oven, and install the cleaned glass substrate into the coating fixture for the substrate coating process.

[0029] The coating process is that in a vacuum environment, use an Optorun coating equipment to coat a reflective film layer on one side of the glass substrate, and at the same time coat a reflective film layer of the same thickness on the other side. The reflective film layers are designed to be double-sided symmetric on both sides of the glass substrate, and the film layer structure is that the film layer structure from the side of the glass substrate of the reflective film layer is nL(HL) N (HL) 1 (HnL) 1 Substrate (nLH) 1 (LH) 1 (LH) N nL, where H represents Ta 2 O 5 film layer, and L represents SiO 2Film layer, N represents the number of depositions. n can vary from 0.1 to 1.0 according to the actual reflectivity requirements, but the symmetry of the double-layer film system needs to be ensured. The reflectivity of the reflective layer can be freely adjusted according to usage to control the FWHM. The film layer structure embodied in this embodiment is 0.5L(HL) 2 (HL) 1 (H0.8L) 1 Substrate (0.8LH) 1 (LH) 1 (LH) 2 0.5L. The reflectivity of the reflective layer can be freely adjusted according to usage to control the FWHM within 0.1 nm. The double-layer film uses a symmetric film system design with a reflectivity of 80 ± 1%.

[0030] Place the above-treated glass substrate on the umbrella rack in the cleanroom and transport it to the coating equipment using a special lifting platform. Before coating the glass substrate, heat and bake the vacuum coating equipment to 220 °C and keep it warm for 2 hours. The vacuum degree reaches below 8.0E-4 Pa. Deposit a reflective film layer on one side of the glass substrate according to the above film layer structure, and simultaneously deposit a reflective film layer of the same thickness symmetrically on the other side. After depositing the double-sided reflective film layer, perform a cooling process and cool it below 120 °C before opening the door and taking it out of the furnace.

[0031] Use a spectrophotometer to test the single-sided reflectivity of the product after the above coating, and use an OSA to test the transmission curve of the product, and confirm whether the FSR and ISO meet the design requirements; then cut the obtained product through a cutting device, and finally perform a small-particle test, that is, use an OSA to test the transmission curve of the product, and test whether the test curve meets the requirements of the FSR and ISO. The test situation is as Figure 3 shown, and the product meets the requirements. In addition, use a spectrometer to further test the broadband characteristics of the filter product in this embodiment. The test situation is as Figure 4 and the following table shows. It can be seen that FWHM < 0.1 nm, and the specific data is around 0.08, and IL < 0.5 db.

[0032] Name FSR Standard Value FSR FSR Difference Value BW@3dB IL 1 100 99.99788 0.002122 0.083273 -0.07783 2 100 100.0344 -0.034425 0.088474 -0.24044 3 100 99.97553 0.024475 0.085995 -0.21652 4 100 100.0159 -0.015901 0.083423 -0.12609 5 100 100.0176 -0.017636 0.077714 -0.00696 6 100 99.98113 0.018875 0.087367 -0.14544 7 100 99.97482 0.025185 0.087027 -0.08348 8 100 99.97738 0.022623 0.091705 -0.13304 9 100 100.0245 -0.024545 0.085303 -0.12783 10 100 99.98104 0.018965 0.089797 -0.15609

[0033] The above are only the embodiments of the present invention, and do not limit the patent scope of the present invention accordingly. Any equivalent structure or equivalent process transformation made using the content of the specification of the present invention, or directly or indirectly applied in other related technical fields, shall be equally included in the patent protection scope of the present invention.

Claims

1. A high-precision and broadband controllable quantum measurement system filter, characterized by: The invention comprises a glass substrate, wherein the glass substrate is polished in a classical manner, the polishing precision is controlled within 0.5um, the parallelism is controlled within 1″, the polishing surface shape is controlled above 1 / 20λ, and reflective film layers are symmetrically arranged on both sides of the glass substrate, wherein the reflective film layers are alternately stacked by Ta2O5 film layers and SiO2 film layers.

2. The high-precision and broadband-controllable quantum measurement system filter according to claim 1, characterized in that: The film structure of the reflective film layer from the glass substrate side is nL (HL) N (HL) 1 (HnL) 1 Substrate (nLH) 1 (LH) 1 (LH) N nL, where H represents the Ta2O5 film layer, L represents the SiO2 film layer, and N represents the number of depositions. n can be changed from 0.1 to 1.0 according to the actual reflectivity requirements, but the symmetry of the double-sided film system needs to be ensured, and the FWHM is controlled by freely adjusting the reflectivity of the reflective layer.

3. The high-precision and broadband-controllable quantum measurement system filter according to claim 1, characterized in that: The glass substrate controls the FSR by controlling the thickness of the substrate, and the thickness of the substrate is adjusted according to actual usage to meet the FSR requirement.

4. A method for preparing a high-precision and broadband-controllable quantum measurement system filter according to any one of claims 1 to 3, characterized in that: The process includes the following steps: substrate polishing - substrate cleaning - substrate clamping - substrate coating - substrate testing - upper plate cutting.

5. The high-precision and broadband-controllable quantum measurement system filter according to claim 4, characterized in that: The above substrate polishing includes the following steps: polishing both sides of the glass substrate by a polishing device - measuring the substrate polishing thickness by a physical instrument - measuring the substrate surface shape and parallelism by a laser interferometer - optically measuring FSR to meet the requirements.

6. The high-precision and broadband-controllable quantum measurement system filter according to claim 5, characterized in that: Before polishing both sides of the glass substrate, the asphalt disc low-polishing process is used to correct the asphalt disc surface shape, and the standard sheet polishing test is performed to see whether it meets the polishing surface shape requirement of 1 / 20λ.

7. The high-precision and broadband-controllable quantum measurement system filter according to claim 5, characterized in that: When the glass substrate is polished on both sides, nm-level polishing liquid is used, and the surface roughness Ra of the glass substrate is less than 10nm; at the same time, high-precision measuring equipment is used to test while polishing, and the polishing thickness accuracy is controlled within 0.5um.

8. The high-precision and broadband-controllable quantum measurement system filter according to claim 5, characterized in that: The above-mentioned substrate coating process is to place the glass substrate on an umbrella stand in a clean room, transport it to the coating equipment by a special lifting platform, and use the optical pool coating equipment to coat a spectroscopic film on one side of the glass substrate in a vacuum environment, and then coat a spectroscopic film of the same thickness on the other side.

9. The high-precision and broadband-controllable quantum measurement system filter according to claim 5, characterized in that: In the above substrate coating process, the vacuum coating equipment is heated and baked to 220°C and kept warm for 2 hours, and the vacuum degree reaches below 8.0E-4Pa.

10. The high-precision and broadband-controllable quantum measurement system filter according to claim 5, characterized in that: In the above-mentioned substrate coating and furnace exiting process, the glass plate is cooled down before coating the double-sided reflective film, and the door is opened after the temperature is cooled to below 120°C.

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