RU2515672C1 - Method to manufacture microoptic raster - Google Patents

Abstract

FIELD: construction.

SUBSTANCE: method to manufacture a microoptic raster in a plate from a porous optical material consists in serial formation of areas with varied optical properties by means of local laser exposure into the plane of area formation, combined with the plane of focusing of the laser beam. The plate from the porous optical material is preliminarily exposed to impregnation in a liquid, the dipole moment of molecule of which is arranged within the limits from 0.2 to 2.5 D, local laser exposure is carried out with density of capacity not exceeding 2.1·10⁷ W/cm², during the time of at least 300 seconds. Then the plate with the microoptic raster is exposed to thermal treatment in a furnace, besides, the plate is heated from room temperature to temperature not exceeding 250°C. At the temperature of 250°C the plate is maintained for at least 30 minutes, further heating is carried out to temperature of 860-880°C with soaking of at least 10-20 minutes, afterwards the plate is cooled to room temperature.

EFFECT: expansion of functional capabilities of a microoptic element of a raster and provision of conditions for preservation of its optical characteristics during time.

2 cl, 13 dwg

Description

The invention relates to the manufacturing technology of micro-optical elements - the main element of optics and optoelectronics and rasters from them. The invention can be used in signal processing devices in optoelectronics, where the main function of micro-optical rasters is to focus the radiation of laser source matrices or LEDs into a single-mode fiber matrix or to the corresponding display element. In addition, micro-optical elements and rasters from them can be widely used in imaging systems and in laser technology for converting laser beams and in systems for determining the distribution of power over the beam cross section.

A known method of manufacturing a micro-optical raster in a plate of silicate glass of various compositions, which consists in creating a thin layer not exceeding 20 microns, enriched with silver ions, by ion exchange of sodium ions to silver ions by contact of the glass plate with a solution comprising 5 molar% AgNO ₃ and 95 mole% NaNO ₃ at 340 ° C for one hour heat treatment iprotsessa plate in a hydrogen atmosphere at 180 ° C during one hour or at 200 ° C for 0.5 hours, by which this layer assumes a peak n absorption at 410 nm and sequential local exposure to the wafer surface by a focused continuous-wave laser beam with a radiation wavelength close to the absorption peak of the created layer, with a radiation power of 30-60 mW, with an exposure duration of 100-500 ms (Microlens and method of marking same (Microlenses and the method of their formation), authors: Michae1 Rosenblunh, Yuri Kaganovskii, publication No. US 2005/0200961, publication date: September 15, 2005).

The disadvantage of this method is the impossibility of creating a refractive micro-optical element in the volume of the plate, as well as the limitation on the range of its transparency, which is in the range of 0.4-2 microns. In addition, this method does not allow to produce a micro-optical element of complex structure, capable of refracting one part of the incident beam and deflecting the other part.

A known method of manufacturing a microlens raster in a plate of porous optical material, the authors selected for the prototype (AS No. 1108383, IPC G02B 21/00, publ. 08/15/1984), which consists in the sequential formation of areas with altered optical properties - by means of a local laser exposure, in the plane of formation of areas combined with the focusing plane of the laser beam, with the duration of exposure, determined by the ratio:

,

,

- плотность мощности потока излучения в области воздействия;Where $$q=\frac{\left(\mathrm{one}-R\right)P\rho }{\pi r_0^2}$$

- power density of the radiation flux in the area of influence;

R is the reflection coefficient of the plate material;

P is the radiation power of the source of exposure, W;

ρ is the transmittance of the optical system, forming the area of influence;

r ₀ is the radius of the impact area, m;

T _yn is the compaction temperature of porous silicate glass;

a is the coefficient of thermal diffusivity of the plate;

k is the coefficient of thermal conductivity of the plate;

until the formation of the last element of the raster.

The disadvantages of the prototype method include the impossibility of creating a microlens in the volume of the plate, as well as the inability to manufacture a microlens of a complex structure that can simultaneously reject a part of the incident beam of rays to deflect another part of the beam, as well as the change in the optical characteristics of the microlens over time, due to the nature of the porous glass surrounding the microlens.

The porous glass surrounding the microlens, due to its structural features - a branched system of pores and channels - is an unstable material, the physical and optical characteristics of which change over time due to the absorption of porous glass from the environment, gases, vapors, individual molecules and atoms, constituents of air, as well as small particles polluting the air [TVAntropove, D.Petrov, E.Yakovlev. “Porous glasses as basic matrixes of microoptacal devices: effect of composition and leaching conditions of the initial phase separated glass.” Physics and Chemistry Glasses. - 2007, vol 48, No. 5, p. 324-327].

These disadvantages of the prototype method limit the use of trace elements and rasters from them in optics and optoelectronics.

The objective of the present invention is to expand the functionality of the micro-optical element of the raster and provide conditions for maintaining its optical characteristics over time.

The goal in the claimed method is achieved by the fact that according to the method of manufacturing a micro-optical raster, which consists in sequentially forming areas with altered optical properties in a plate of porous optical material by local laser irradiation into the plane of formation of regions, combined with the focusing plane of the laser beam until the formation of the raster, a plate of porous optical material is preliminarily impregnated in a liquid, the dipole moment of the molecule which is located in the range from 0.2 to 2.5 D, local laser exposure is carried out with a power density not exceeding 2.1 · 10 ⁷ W / cm ² for a period of at least 300 seconds with a radiation wavelength for which the plate material is transparent after all regions of the micro-optical raster are formed, the micro-optical raster plate is heat treated in a furnace, and the plate is heated from room temperature to a temperature not exceeding 250 ° C at a speed. not exceeding 1.6 ° C / min, at a temperature of 250 the plate is held for at least 30 minutes, further heating is carried out at a speed not exceeding 3 ° C / min, to a temperature of not lower than 860 ° C and not higher than 880 ° C, at which the plate is kept for at least 10 minutes and no more than 20 minutes, after which the plate is cooled to room temperature, turning off the oven.

In addition, glycerin is used as an impregnating liquid.

The indicated impregnation of a plate of porous optical material with a liquid, the dipole moment of the molecule of which is in the range from 0.2 to 2.5 D, enhances the mass transfer process of finely dispersed amorphous silica, lining the walls of the channels and pores and capable of moving towards the central part of the formed micro-optical element under the action of a secondary constant electric field arising in the focus area of the laser beam, on which the process of microoptical formation is based Skogen element.

The restrictions in the claims on the power density and the duration of the laser exposure for the formation of the micro-optical element of the raster were determined experimentally.

The restrictions indicated in the claims on the heating rate of the first and second stages of heat treatment, the restriction on temperature and duration of exposures that complete these stages, ensure decomposition of the impregnating liquid at the first stage of heat treatment, and the complex structure of the micro-optical element is preserved at the second stage, its optical characteristics remain unchanged over time, as well as providing conditions for maintaining the integrity of the plate with a micro-optical raster by minimizing thermomechanical stresses eny arising in the plate and facilitating its destruction, were determined experimentally.

при длительности воздействия 300 с.The invention is illustrated by drawings, where figure 1 shows a diagram of a device for implementing a method of manufacturing a micro-optical raster. Figure 2 shows the transmission spectrum of a porous glass plate. Figure 3 shows the transmission spectrum of a porous glass impregnated with glycerol. Figure 4 shows a computer printout of photographs of one of the micro-optical elements of the raster, heat-treated in the oven in accordance with the parameters claimed in the claims, that is, the plate with the raster was heated from room temperature to a temperature of 250 ° C at a speed of 1.6 ° C / min, at a temperature of 250 ° C, the plate was held for 30 minutes, further heating was carried out at a speed of 3 ° C / min to a temperature of 870 ° C, at which the plate was kept for 15 minutes, after which the plate was cooled to room temperature, turning off the oven. The micro-optical element shown in the photograph was formed at a depth of 500 μm from the surface of the plate impregnated with glycerin, with a radiation flux density $$2\cdot {10}^7\frac{\mathrm{AT}t}{\mathrm{from}{\mathrm{<figure-callout\; id="2"\; label="m"\; filenames="00000010.png"\; state="\{\{state\}\}">m</figure-callout>}}^2}$$

with exposure duration 300 s.

The photograph was taken on a microscope (Carl Zeiss Axio Imager Al) in transmitted light and in crossed polarizers at a magnification of 100 ^X. The complex structure of a micro-optical element consisting of a central region with a refractive index equal to the refractive index of a quartzoid formed during heat treatment and surrounding the central region of the spherical layer with a refractive index of a lower value than the refractive indices of the central region and the plate is clearly visible in the photograph.

при длительности воздействия 360 с. Фотография, как и в предыдущем случае, выполнена в проходящем свете и в скрещенных поляризаторах при увеличении 100^X. На фотографии заметны трещины, окружающие микрооптический элемент растра.Figure 5 shows a computer printout of photographs of one of the micro-optical elements of the raster, which has undergone heat treatment in the furnace in accordance with the parameters claimed in the claims. The micro-optical element shown in the photograph was formed at a depth of 500 μm from the surface of the plate impregnated with glycerin, with a radiation flux density $$q=2\cdot {10}^7\frac{\mathrm{AT}t}{\mathrm{from}{\mathrm{<figure-callout\; id="2"\; label="m"\; filenames="00000010.png"\; state="\{\{state\}\}">m</figure-callout>}}^2}$$

with exposure duration 360 s. The photograph, as in the previous case, was made in transmitted light and in crossed polarizers at a magnification of 100 ^X. Cracks surrounding the micro-optical element of the raster are noticeable in the photo.

при длительности воздействия 420 с. Фотография выполнена в проходящем свете и в скрещенных поляризаторах с увеличением 100^X. На фотографии виден начинающийся процесс разрушения микрооптического элемента.Figure 6 shows a computer printout of photographs of one of the micro-optical elements of the raster, which collapsed at the stage of formation. The micro-optical element shown in the photograph was formed at a depth of 500 μm from the surface of the plate impregnated with glycerin, with a radiation flux density $$q=3\cdot {10}^7\frac{\mathrm{AT}t}{\mathrm{from}{\mathrm{<figure-callout\; id="2"\; label="m"\; filenames="00000010.png"\; state="\{\{state\}\}">m</figure-callout>}}^2}$$

with exposure duration 420 s. Photo taken in transmitted light and in crossed polarizers with a magnification of 100 ^X. The photograph shows the beginning of the process of destruction of the micro-optical element.

в течение 360 с. Фотография выполнена в скрещенных поляризаторах с увеличением 100^X.Figure 7 shows a computer printout of photographs of one of the micro-optical elements of the raster, the central region of which has undergone irreversible changes at the formation stage - the onset of crystallization and destruction. The micro-optical element shown in the photograph was formed at a depth of 500 μm from the surface of the plate impregnated with glycerin, with a radiation flux density $$q=\mathrm{3,5}\cdot {10}^7\frac{\mathrm{AT}t}{\mathrm{from}{\mathrm{<figure-callout\; id="2"\; label="m"\; filenames="00000010.png"\; state="\{\{state\}\}">m</figure-callout>}}^2}$$

within 360 s. Photo taken in crossed polarizers with a magnification of 100 ^X.

On Fig shows a computer printout of photographs of one of the micro-optical elements of the raster after heat treatment, in which the heating rate in the first stage was 2.5 ° C / min, and all other heat treatment parameters were maintained in accordance with the parameters claimed in the claims. The micro-optical element shown in the photograph was formed at a depth of 500 μm from the surface of the plate impregnated with glycerin, in accordance with the laser exposure parameters claimed in the claims. A photograph taken in crossed polarizers with a magnification of 100 ^X shows cracks surrounding the trace element.

Figure 9 shows a computer printout of photographs of one of the micro-optical elements of the raster after heat treatment, in which all the claimed parameters of both stages of heat treatment were met, except for one - exposure after the first stage of heat treatment was performed at 300 ° C for 10 minutes. The micro-optical element shown in the photograph was formed at a depth of 500 μm from the surface of the plate impregnated with glycerol, in accordance with the laser exposure parameters claimed in the claims. In a photograph taken in transmitted light with a magnification of 100 ^X , an increased turbidity of the central region of the micro-optical element is noticeable.

Figure 10 shows a computer printout of photographs of one of the micro-optical elements of the raster, after heat treatment, in which all the claimed parameters of both stages of heat treatment were met, except for one - the heating rate of the second stage was increased to 5 ° C / min. The micro-optical element shown in the photograph was formed at a depth of 500 μm from the surface of the plate impregnated with glycerol, in accordance with the laser exposure parameters claimed in the claims. A photograph taken in crossed polarizers with a magnification of 100 ^X shows cracks surrounding the micro-optical element.

Figure 11 shows a computer printout of photographs of one of the micro-optical elements of the raster after heat treatment, in which all the claimed parameters of both stages of heat treatment were met, except for one - at the second stage of heat treatment, the plate was heated to 900 ° C, at which it was held for 10 minutes. The micro-optical element shown in the photograph was formed at a depth of 500 μm from the surface of the plate impregnated with glycerol, in accordance with the laser exposure parameters claimed in the claims. In a photograph taken in transmitted light with a magnification of 100 ^X , the crystallization of the micro-optical element and the regions adjacent to it is visible.

Figure 12 shows a computer printout of photographs of one of the micro-optical elements of the raster after heat treatment, in which all the claimed parameters of both stages of heat treatment were met, except for one - when the temperature reached 870 ° C in the second stage of heat treatment, the plate was kept at this temperature for 30 minutes . The micro-optical element shown in the photograph was formed at a depth of 500 μm from the surface of the plate impregnated with glycerol, in accordance with the laser exposure parameters claimed in the claims. In a photograph taken in transmitted light with a magnification of 100 ^X , the complex structure of the micro-optical element is practically not visible, which indicates the alignment of the refractive index of the central region, the spherical layer surrounding it, and the quartzoid plate.

On Fig is a schematic drawing of the structure of the micro-optical element. The same figure shows the path of the rays through the micro-optical element for the cases of: a) a parallel beam, b) a converging beam, c) a diverging beam.

The device for implementing the proposed method of figure 1 contains a continuous ytterbium fiber laser LK 100 B, with a wavelength of 1.07 μm, a radiation line width Δλ = 0.003 μm and an output power instability of 1% (1), a mechanical shutter-timer (2) that allows you to adjust the exposure time, set at an angle of 45 ° to the optical axis of the radiation source, a transparent glass plate (3), the directing part of the radiation to the optical power meter (4), a Gentec Solo-2M meter with pi was used as an optical power meter with a UP 19K-11 OF-H9 power detector with an accuracy of 1% of the measured value and a noise power equivalent of 1 mW, a LOMO micro lens (5) with a magnification of 10 ^X , numerical aperture NA = 0.25 and focal length f = 4.75 0 25 mm, behind which there is a porous glass plate (6) fixed perpendicular to the optical axis of the radiation source on the coordinate table (7), made with the possibility of moving in x, y, z coordinates with an accuracy of 2.0 ± 0.5 μm, and behind the plate (6) is a second power meter (8) mounted perpendicular to the optical axis of the radiation source.

From the transmission spectrum of a plate of porous glass impregnated with glycerol (figure 2), the choice of a laser for a device for implementing the inventive method is obvious. At the laser radiation wavelength (a - 1.07 μm), the transmission of the plate impregnated with glycerin exceeds 0.9, i.e., in other words, the plate material is optically transparent for laser radiation. The optical transparency of the wafer material for the laser radiation wavelength allows the formation of a micro-optical raster element at a certain depth from the wafer surface, i.e. in its volume.

The device operates as follows. Laser radiation (1) passes through a mechanical shutter (2) that controls the exposure time, a plate (3) mounted at an angle of 45 ° to the optical axis of the radiation source and directing the radiation to the power meter (4), and enters the micro-lens (5) focusing radiation into the plane of formation of a micro-optical element in almost all cases of experiments located at a depth of 500 μm from the surface of a porous glass plate (6) - a raster blank previously impregnated with glycerin and placed at the coordinates th table (7) perpendicular to the incident radiation beam. The coordinate table (7) is made with an accuracy of movement in any of the coordinates - x, y, z, with an accuracy of movement of 2.0-0.5 microns. Part of the radiation. passing through the formed region is recorded by a power meter (8) placed on the optical axis of the emitter behind the porous glass plate (6) also perpendicular to the incident radiation beam. The formation of the micro-optical element in the raster is carried out by successive discrete movement of the impact area with a given step of moving the coordinate table (7), which provides the step of placing the micro-optical elements in the raster. The accuracy of moving the coordinate table 2.0 ± 0.5 μm, ensures the accuracy of the arrangement of micro-optical elements in the raster.

The size of the micro-optical element and its optical characteristics at the stage of formation are controlled by changing the size of the exposure region r ₀ , the radiation flux power P, and the exposure duration τ.

The minimum size of a micro-optical element that can be manufactured by the claimed method is determined by the divergence of the radiation beam of the laser used (1) and the optical characteristics of the micro-lens (5) and can be ~ 10 μm on the equipment described in the description.

The micro-optical element of the raster is formed by local exposure to a focused laser beam in the plane of formation of the region. The process of formation of a micro-optical element is due to the mass transfer of finely dispersed amorphous silica hydrated with water, lining the walls of the channels and pores of a porous glass plate soaked in glycerol. Under the influence of an alternating electric field with a frequency of the optical visible range in the focus area of the laser radiation, leading to the polarization of the substance and the distribution of charges, which during irradiation create a constant secondary electric field. The use of glycerol as an impregnating liquid, the dipole moment of the molecule of which falls within the range from 0.2 to 2.5 D, increases the intensity of the secondary constant electric field in the focusing region by more than an order of magnitude, compared with the value of the secondary constant electric field responsible the process of forming a micro-optical element in the volume of the plate of "dry" porous glass, and thereby enhances the mass transfer process.

As a result of laser exposure to the plane of formation of the micro-optical element, combined with the focus plane of the laser beam, a mass transfer of the substance filling the channels of the porous glass plate occurs, the determining factor for the speed and duration of this process is the power density of the laser beam in the focusing area, the duration of exposure, and also the dipole moment of a liquid molecule used as an impregnating element for a porous glass plate.

As a result of exposure, a region forms in the form of a microsphere, consisting of a central part, the channels of which are completely or in large part filled with a substance transferred from the spherical layer surrounding the central part of the spherical layer, i.e. area with complex structure. Due to the complete or partial filling of the central region with matter, its refractive index is close in value to the refractive index of a plate of porous glass impregnated with glycerin, while the refractive index of the spherical layer surrounding the central part of the micro-optical element, i.e., a layer with an increased porosity, than smaller in value, the greater part of the substance in the process of mass transfer left it. A microspherical region of complex structure with a central part with a refractive index exceeding the refractive index of the spherical layer surrounding it, is able to refract part of the incident radiation beam by the central part and deflect another part of the beam by a spherical layer. In other words, the complex structure of the microspherical region - the micro-optical element of the raster contributes to the expansion of its functionality.

After all regions of the micro-optical raster are formed, the micro-optical raster plate is subjected to heat treatment in an oven, and the plate is heated from room temperature to a temperature not exceeding 250 ° C, at a speed not exceeding 1.6 ° C / min, at a temperature of 250 the plate is held for at least 30 minutes, further heating is carried out at a speed not exceeding 3 ° C / min, to a temperature of not lower than 860 ° C and not higher than 880 ° C, at which the plate is held for at least 10 minutes and no more than 20 minutes, after bringing the plate to room temperature temperature by turning off the oven.

The complex structure of the micro-optical element of the raster, which ensures the expansion of its functional capabilities, is preserved during heat treatment aimed at stabilizing the physical and optical characteristics of the micro-optical element of the raster and plate on which this raster is made, as well as eliminating the liquid impregnating the plate by decomposition.

Heat treatment of plates with a micro-optical raster is carried out in an oven, for example, model CHOL 6/10, in which heating to a temperature of 1050 ° C is possible, it is possible to provide different heating rates and it is possible to maintain the temperature with an accuracy of ± 5 ° C.

For plates with a micro-optical raster, the micro-optical elements of which were formed with laser radiation parameters, in accordance with the claims, and two-stage heat treatment was performed in accordance with the parameters given in the claims, (for example, Fig. 4), integrity is maintained, each the raster element and, accordingly, the raster as a whole is characterized by optical qualities.

, τ=360 с (фиг.5); $$q=3\cdot {10}^7\frac{Вт}{с{м}^2}$$

, τ=360 с (фиг.6) или $$q=\mathrm{3,5}\cdot {10}^7\frac{Вт}{с{м}^2}$$

, τ=360 с (фиг.7)),For wafers with a micro-optical raster, micro-optical elements of which were formed under the condition that at least one of the parameters of the laser exposure did not satisfy the parameters given in the claims (for example, $$q=2\cdot {10}^7\frac{\mathrm{AT}t}{\mathrm{from}{\mathrm{<figure-callout\; id="2"\; label="m"\; filenames="00000010.png"\; state="\{\{state\}\}">m</figure-callout>}}^2}$$

, τ = 360 s (Fig. 5); $$q=3\cdot {10}^7\frac{\mathrm{AT}t}{\mathrm{from}{\mathrm{<figure-callout\; id="2"\; label="m"\; filenames="00000010.png"\; state="\{\{state\}\}">m</figure-callout>}}^2}$$

, τ = 360 s (Fig.6) or $$q=\mathrm{3,5}\cdot {10}^7\frac{\mathrm{AT}t}{\mathrm{from}{\mathrm{<figure-callout\; id="2"\; label="m"\; filenames="00000010.png"\; state="\{\{state\}\}">m</figure-callout>}}^2}$$

, τ = 360 s (Fig. 7)),

a violation of the integrity of the micro-optical raster is manifested, which manifests itself in the formation of a fractured layer surrounding the micro-optical elements of the raster, or in the splitting of a plate with a raster.

For wafers with a micro-optical raster, the micro-optical elements of which were formed in accordance with the laser exposure parameters given in the claims, but at least one of the parameters of any of the two stages of heat treatment was not maintained (for example, the speed increased to 2.5 ° C / min the first stage of heat treatment (Fig. 8), exposure is completed the first stage of heat treatment, at a higher temperature of 300 ° C and with a shorter duration of 10 minutes (Fig. 9), an increase in the heating rate in the second stage of heat treatment to 5 ° C / in (Fig. 10), reducing exposure, completing the second stage of heat treatment at a higher temperature of 800 ° C (Fig. 11), reducing exposure, completing the second stage of heat treatment within 30 minutes (Fig. 12), it is typical either the formation of a fractured layer ( 8 and 10) surrounding the micro-optical element, or increased turbidity, in other words, a significant reduction in transmittance (FIG. 9), or crystallization of the micro-optical element and its adjacent areas (FIG. 11), or the disappearance of the complex microelement structure (FIG. 12 )

Based on the foregoing, the claimed combination allows the formation of a micro-optical raster, the functionality of the micro-optical elements of which is expanded due to the complex structure of the micro-optical element, the central part of which is able to refract, its surrounding part - to reject the radiation incident on the microelement and whose optical characteristics do not change over time.

The expansion of the functionality of micro-optical elements of the raster will reduce the number of circuit elements in signal processing devices in optoelectronics.

Claims (2)

1. A method of manufacturing a micro-optical raster in a plate of a porous optical material, which consists in the sequential formation of regions with altered optical properties by local laser exposure to the plane of formation of regions, combined with the focus plane of the laser beam until the formation of the raster, characterized in that the plate is made of porous optical material is preliminarily impregnated in a liquid, the dipole moment of the molecule of which is located in the range from 0.2 to 2.5 E, local laser exposure is carried out with a power density not exceeding 2.1 · 10 ⁷ W / cm ² for a period of at least 300 seconds with a radiation wavelength for which the plate material is transparent, after all areas of the micro-optical raster are formed, the plate with a micro-optical raster is subjected to heat treatment in an oven, and the plate is heated from room temperature to a temperature not exceeding 250 ° C, at a speed not exceeding 1.6 ° C / min, at a temperature of 250 ° C the plate is held for at least 30 minutes, gave Further heating is carried out at a speed not exceeding 3 ° C / min, to a temperature not lower than 860 ° C and not higher than 880 ° C, at which the plate is held for at least 10 minutes and no more than 20 minutes, after which the plate is cooled to room temperature, turning off the oven. 2. A method of manufacturing a micro-optical raster according to paragraph 1, characterized in that glycerin is used as an impregnating liquid.

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