Method of making tunable optical filter with fabry-perot interferometre

FIELD: physics, optics.

SUBSTANCE: tunable optical filter with Fabry-Perot interferometre has transparent plates with mirror coatings with spacing in between. When making the said optical filter, a sacrificial layer is deposited on one plate with the mirror coating. A mirror coating is then deposited on top and the second transparent plate is attached through a layer of hardening material. After that the said plates are attached to holders through a hardening material and the sacrificial layer is removed through evaporation by heating to temperature below the thermal destruction temperature of the hardening layer.

EFFECT: easier obtaining of controlled spacing between plates, avoiding use of special methods of obtaining surfaces with high degree of flatness, avoiding the need to monitor the value of the spacing and its wedge.

1 dwg

 

The invention relates to optics, to methods of manufacturing devices with small controlled gap size in fractions of a micron, including the manufacture of optical devices based on the use of interference of light beams, such as Fabry-Perot interferometers used in scientific research and technology for spectral analysis and monochromatization of light.

Analogue of the invention is a method of obtaining a clearance between the plate and the membrane electrode, which consists in coating the surface of the plates an additional layer having a thickness equal to the value of the clearance, on top of which, overlapping the edges of the additional layer is applied by sputtering film electrode and remove the additional dissolution (sacrificial) layer. Due to the overlapping edges of the foil electrode and the contact plate, and foil electrode is attached to the wafer by its edges [1]. The method is not suitable for devices with high-precision adjustable flat clearances between the polished surfaces of the two plates in which the plates are moved to a special mechanism, since such plates are fixed in the mechanism for moving the plates individually, do not have common points of contact and must be moved relative to each other entirely and not change the I form.

As the prototype is set to a known method of manufacturing optical devices containing the mirror surface with a gap between them, for example devices with Fabry-Perot cavities [2].

In accordance with the prototype, pre, methods, mechanical or other polishing, preparing plates with a high degree of flatness of at least one of surfaces of each plate method, for example, deep polishing these surfaces give a mirror-like properties (thin films), then the plates are fixed relative to each other in the mechanism of their movement to the polished surface was between a flat gap.

The disadvantages of the prototype: the complexity of the way while providing acceptable flatness of the massive gap between the plates is of the order of hundredths-tenths of the wavelength of the radiation; this condition requires significant cost to the manufacture of plates and design complexity of the device with such plates as a whole and its operation in connection with the necessity of introducing into the design of the shutter mechanism and the process of alignment with the constant control of the relative position of the plates; the method does not allow to obtain controlled gaps with sizes of the order of interatomic distances.

The objective of the invention:

to simplify obtaining the con is controlled gaps between solid plates with dimensions in the submicron and nanometer areas by avoiding the use of special methods for producing surfaces with a high degree of flatness;

- exclude the control gap and wedge in the Assembly process (manufacturing) device.

The task is solved in that in the method of manufacturing a tunable optical filter with a Fabry-Perot interferometer, comprising applying a mirror coating on a transparent plate - the base of the mirrors and fixing the latter with a gap parallel to each other on the holder mechanism to move the plates, and the gap is obtained using a sacrificial layer, in accordance with the invention mirrored finish one plate, get, putting him on the sacrificial layer deposited beforehand on the mirror coating of the other plate, and then attached to the first plate layer hardening material, after which the said plates are hardened material secured on said holders.

It is also proposed that, in accordance with the invention, the sacrificial layer is made of a substance that receding melting or evaporation when heated to a temperature lower temperature thermonatrite hardening layer.

The method is illustrated in figure 1. On the first plate 1 with polished surface 2 is applied, the mirror layer 3 (Fig 1, a), over which is applied a sacrificial layer 4 (figure 1, b). On top of the sacrificial layer is applied to the mirror layer 5 of the second plate (figure 1, C) the type of land that do not overlap the edges of the sacrificial the Loya. On top of the mirror layer is applied hardening material 6 (Fig 1, d), over the obtained patterns impose the second plate 7 (Fig 1, d); hardening the material between the plate and the mirror layer of the pressure plate and under the action of surface tension is distributed in a layer 8 of uniform thickness; the amount of hardening of the material should be such that the material is not leaking outside of the reflecting layer 5. Upon completion of the process of solidification of the layer 8 of the consolidated structure containing plates and layers between them, fix in the designated place, the destination device or node, as illustrated in figure 1, e, where 9 and 10 - holders mechanism for moving the plates in the Fabry-Perot interferometer. Figure 1 e shows schematically the mechanism in which the propellers are piezoelectric or magnetostrictive elements 11. The consolidation of the holders is hardening material 12. The final step is the removal of the sacrificial layer 4, by its evaporation or dissolution (1, W). After removal of the sacrificial layer between the mirrors 3 and 5, a gap 13.

The proposal according to claim 1 of formula eliminates time-consuming and costly process of obtaining a polished surface of a given shape, such as flat surfaces with a roughness of not more than 0.03 µm-ipassconnect no worse than 0.05 microns, what is needed when creating interferometers. The geometrical characteristics of the sacrificial layer completely determine the geometrical characteristics of the resulting gap: if this layer is applied in the form of a film of constant thickness, the gap between the functional surfaces of the device will be equidistant. The design of the interferometer layer 8 makes a compensatory role, he local changes its thickness compensates for the unevenness of the surfaces of the plates 1 and 7, providing ravnoudalennostj gap 13 throughout its area.

The necessity of fastening plates 1 and 7 on the electrodes 9 and 10 by using the hardening material 12 due to the need to eliminate mechanical stresses at the connection that occurs when mechanical fastening, which can lead to shifts of the plates and the violation of the right shape of the gap between the mirrors 3 and 5 of the interferometer. The use of curing adhesives ensures that the changes in the amounts of solidified layers (unlike, for example, from drying formulations that changes its volume when the volatilization of the solvent).

The necessity that the sacrificial layer is made of a substance that receding melting or evaporation when heated to a temperature lower temperature thermonatrite hardening layer caused by the following circumstances, the AMI. The sacrificial layer in our case is removed from the narrow and has a large area of the gap between the solid glass plates, and its removal by dissolution would require a very large time, in our experiments we could not release the clearance from the material of the sacrificial layer at the time of the dissolution of the order of weeks. Well-known works to accelerate the removal of the sacrificial layer in the bounding layers make through holes, which fills an entire surface of the layers; in our case, this technique is not applicable as broken optical properties of the mirror coatings. When used for the sacrificial layer melting or evaporating material with proper heat already glued hardening composition device substance evaporates and the pairs themselves are removed from the gap; in the case of consumable material removal is also facilitated, as can be diluted plate with mirror coatings from each other, increasing the gap width.

Consider the examples of the invention's implementation.

To get between the two glass plates of flat gap thickness less than 1 μm will conduct their preliminary training, which is mechanically polishing at least one side of each plate with the requirements for flatness no worse than N=5 (5 of the Newton rings), ΔN=1. Draw on this surface is rnost the first plate through the mask translucent mirror layer of aluminum by vacuum deposition. In the same vacuum chamber will Nephilim this functional surface of the sacrificial layer mannitol 0.25 µm in thickness, and at him through a mask of the second semi-transparent layer of aluminum. Apply on top of the layer of aluminum drop-curing composition, for example a two-component optical glue OK-71, put the top and the second transparent plate. After hardening of the glue, or even not so cured, put the package into the socket on the holder mechanism, greased the same glue. After hardening of the adhesive resulting design is put in the vacuum and heat to boiling point mannitol (~200°C), wait for the complete evaporation of the sacrificial layer from the gap. Thus, you will get the mirror resonator Fabry-Perot, the gap between them has the same value at all points of their surface, suitable for use as tunable optical filters. Hardened material can be melt such as a molten polymer.

Examples of the invention and analysis of the reasonableness of the proposed solutions show the usefulness and novelty of solutions, their feasibility and attainability of its stated goals.

Industrial application of the method can be found in the manufacture of various optical, optoelectronic and micromechanical devices, which must receive clearance R the main and small thickness between the electrodes or plates, having a large surface area, in particular controllable Fabry-Perot interferometers.

Sources of information

1. Chesnokov V.V. Electrostatic relay // A.S. 314304 the USSR, MKI NC 17/52. Publ. 07.09.1971. Bull. No. 27.

2. S.A. Akhmanov, Nikitin HE Physical optics. Tutorial - M.: Izd-vo Mosk. University, 1998.

A method of manufacturing a tunable optical filter with a Fabry-Perot interferometer in the form of a pair of transparent plates with mirror coatings located with a gap, characterized in that on one plate with a mirror coating is applied to the sacrificial layer, over which is applied a mirrored floor and attach the second transparent plate with a layer of solid material, after which the above-mentioned plate-curing material is fixed on the holder and removing the sacrificial layer by evaporation, heating it to a temperature lower temperature thermonatrite hardening layer.



 

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