DE19632563A1 - Structured quarter-wave plate, mirror, grating and prism production - Google Patents

Abstract

The process is carried out on an X-Y table with an environmental chamber (1), motor-driven (2) from a control computer (3) for molecular beam movements in additive corpuscular radiation lithography. The instrumentation includes a scanning electron microscope (9) with a field emission cathode (10), a Faraday cage (11) and a secondary electron detector (12). The optically active zones and positional co-ordinates of the zone(s) to be treated are measured at increasing magnifications before the optical component layers and three-dimensional structures are applied under programmed control. The supply of material from a reservoir (4) with heating and cooling elements (5) is adjusted by valve operations (6).

Description

The invention relates to a method of manufacture structured λ / 4 plates, mirrors, gratings and Prisms on three-dimensional surfaces in the generic term of claim 1 defined in more detail and in a Device for producing structured λ / 4 platelets, Mirrors, gratings and prisms according to the generic term of claim 7.

Lasers made of fibers doped with laser material and also solid Body lasers need for optimal amplification and Selection of the λ / 4 plates suitable for the vibration mode, Mirrors, gratings and prisms at the ends of the laser area ches. With these λ / 4 plates, mirrors, gratings and Prisms become the mode number, shape, position and polarization certainly. Likewise, the way a laser works influenced. Usually a highly reflective mirror is on an end to the effective back reflection of the light in the laser medium and one with a defined transmission provided mirror on the coupling-out side of the laser required. This decoupling mirror can be structured be executed. This is how it works through targeted execution a small mirror area on the decoupling mirror as a highly reflective mirror, from a multi-fashioned working pump laser one with a single mode winning vibrating laser. Without selective mirror the laser works as a multi-mode pump laser. Through the The effect of the selective mirror is that in the pump laser without  selective mirror distributed across many fashions Laser power with selective mirror in a fashion for Provided. The one underlying this phenomenon physical process becomes "injection-mode-locking" called. By carrying the strongest electromagnetic wave that is between the highly reflective mirror areas first, all other possible fashions are in the same phase-oriented coherent vibrational state and the possible induced emissions so coherent initiated. So the whole ensemble vibrates coherently and the entire performance is in a vibration mode available. This allows special selective filters to be used Choosing the single mode is eliminated and it can be an easier one Manufacturing process for laser manufacturing applied and it's going to be powerful single-mode lasers receive.

The selectively acting mirror is made by lacquer technology and Lithography on the already on the fiber laser end attached decoupling mirror additionally with a "lift off "process established. By the dimension of the mirror with 25 µm in width, the dimensions are due with a high error. To a single mode too would define a mirror width below 10 µm desirable.

In single-mode fiber lasers, attaching one is highly reflective mirror possible by vapor deposition. However, there will be special embodiments of fiber lasers with M-profile doping and higher efficiency than with Single-mode fiber lasers, applied, is a high-precision Submicrometer accurate manufacturing of miniaturized Mirrors, gratings, prisms and λ / 4 plates required,  that so far not with conventional lithography processes can be generated.

An M-profile fiber laser has a cladding zone inner fiber of approx. 150 µm diameter and 5 µm thickness, the active laser zone in the manufacturing process highly doped glass is manufactured. This ring zone is again from a cladding glass jacket that guides the shaft surround. M-profile doped fiber lasers have already been used experimentally tested. Mode locking and phase shift individual areas of the single-mode wires of the laser Hollow cylinders were experimentally tested in principle tested by connecting an external resonator cavity that was used to introduce macroscopic filters and λ / 4 plate required space required. Here were light losses through beam expansion optics and accepted other lenses and refractive surfaces. The Stabilization of the many monomodes and their local Fixation is not satisfactory.

The invention has for its object a method and specify a device that struk for the manufacture tured λ / 4 plates, mirrors, gratings and prisms three-dimensional surfaces with additive corpuscular beam Lithography used to be effective, cohesive limit, phase position, location, light-direction selection and Light coupling and decoupling and its alignment in several Directions in the manufacture of optical devices such as B. of fiber lasers with doping profiles select and define these optical elements.

This task is accomplished with a procedure according to the Characteristic of claim 1 solved.  

Advantageous further training options of this procedure are in the characterizing part of subclaims 2 to 6 listed.

A device with which to accomplish this task is made possible is in the characterizing part of patent claim 7 described.

The invention is illustrated below with reference to embodiments play explained in more detail. In the accompanying drawings show the

Fig. 1 shows the diagram of a lithography system for lithography additives,

Fig. 2 shows the densification of the deposited material due to long-pixel exposure time which must be taken into account in multilayer films,

Fig. 3 Calculated real and imaginary parts of the dielectric constant metal-filled Nanocrystalline materials for a 20% gold ball suspension with gold spheres of 1.6 nm in diameter,

Fig. 4 is a TEM of a thin-filled nanocrystals polymer / Pt layer with crystallite illustration in the network side picture,

Fig. 5 shows a construction method of a dielectric single layer to reduce reflection and as a λ / 4 plate to phase shift,

Fig. 6 shows the structure of dielectric multilayers as a highly reflective mirror,

Fig. 7 shows the structure of a grating in addition to the highly reflective mirror of dielectric multilayers, which is below a deflecting prism,

Fig. 8 is a schematic of the adjustment of the exposure area on an M-profile fiber laser and

Fig. 9 is a diagram of the combination of λ / 4 layer, grating, mirror, prism, and focusing lens.

With the manufacturing process described in more detail below ren of micromirrors, λ / 4 plates, prisms and gratings and lenses and their combination, these are based on dreidi mensional existing interfaces of optical devices structured with nm precision and additionally applied, without prior preparation for the assignment of the waiters areas is required and without a subsequent Development to complete the optical element is required. The additive nano- Lithography with corpuscular beam-induced deposition under computer control of the corpuscular beam, its up treffortes, the sample position and the supply of precursor sor molecules used. Form the precursor materials the starting materials from which the polymerizing Effect of the corpuscular beam the optically effective Structures under computer control of dose distribution and Location of the corpuscular beam. Through the Choice of different precursors and different deposi conditions such as energy, electricity, power density, Dwell time of the jet and partial pressure of the precursors, can vary the material properties of the landfill Limits from insulating to conductive, from nanocrystalline until structurally polymerized. Materials with different refractive index can also do so in layers through computer control of the valve feed Molecules are deposited, such as. B. for highly reflective dielectric mirror is required.

When using multiple parallel beams with this Technology also large numbers of optical components and their combinations economically interesting and fast getting produced.  

The example of the M-profile fiber laser is the advantageous one Use of this technique explained. With this it succeeds due to different structured mirrors in the µm range Reflective and transmissive parts of the laser Material cylinder jacket as a single mode area through "mode locking ". The first one that vibrates strongly monomode area then controls the vibration states neighboring areas. This can be done with λ / 4 plates in their phase position are influenced so that in phase Light emission is achieved for all areas. Through along the mirror applied to the effective zone This build-up of vibrations can reflect shapes can also be fixed and supported locally. To the Rays of light from the uniformly swinging fashion label range in other optical components, such as. B. Monomode Fibers, which can be coupled, can prisms and lenses on the Mirror areas also applied with nm precision will.

For "injection mode locking" and for determining the phase and the polarization of the modes in the area of the cylinder The active zone of the M-profile laser is a local one Structuring and a local variation of the layer sequence gene required to desired λ / 4 plates and mirrors also to apply varying reflectivities locally gene, as well as prisms for determining the direction of the entrance pump and laser radiation len, as well as attaching grids with which the Polarisa tion state of the modes can also be predetermined.

In contrast to existing methods, the direct Production of λ / 4 plates, mirrors, gratings and Programmed prisms by exposure to the Corpuscular beam on the fiber laser end or laser  directly as a significant improvement over the state of the Technology introduced.

Lithography is used as a manufacturing technique Use of dry lacquer layers deposited in the plasma and of vapor-deposited layers of paint and also the additives Lithography with the corpuscular beam-induced Deposition into consideration. Leave with the latter technique under high-precision computer control Multiple layers structured quickly and selectively on the Laser fiber without additional pre and post treatment apply the same. The multi-layers and others optical components are with submicron accuracy placed and also structurable without additional Process steps are required.

With the evaporable, positive working varnishes the mirror layer of several dielectric layers below different refractive index in multiple adjusted structure Generation steps by "lift-off".

A process is available with dry paint technology at which the laser or the fiber laser end through Evaporation in a high vacuum with a defined layer thickness of a polymer sensitive to corpuscular rays becomes. This polymer is used in the corpuscular beam Exposure crosslinked to a silicon oxide rich polymer, that is well matched to the fiber laser material in the refractive index fits (n = 1.48). On the laser end is one made of silicon Evaporated oxide mirror, on which the Lin material also adapts well to the refractive index. In order to is the insertion loss of these made of dry paint Theoretically, λ / 4 plates, gratings and prisms careless.  

In order to produce mirrors, several layers of ver differently doped dry varnish or from changing mate structured materials. That requires multiple Process steps and is with the negative working dry varnish only possible if the layers are selected Dry etching are generated, with the dry varnish as Etching mask is used. (This is a standard process of Lithograph).

With additive lithography with corpuscular beam-induced deposition, the λ / 4 plates, mirrors, gratings and prisms are produced in a vacuum process from precursor molecules adsorbed from the gas phase by corpuscular beam polymerisation and crosslinking. The position of the beam, the level of the local dose and the type of precursor molecules are controlled directly with computer control and the optical element is thus constructed without the prior assignment or subsequent development of the structure being necessary, see FIG. 1.

The exposure time required for thick structures is Compared to lacquer technology a lot higher, but remains in reasonable times per item. Will only be thin, optically strong-acting, metal-filled polymers used as they at low current densities from organometallic compounds arise, so there are only short exposure times per pixel and therefore required per element. Arrays of such Structures can be precisely and economically with this Process controlled by computer and placed with high precision Produce.

The nanostructured metal-filled polymers are created by segregation of metals in the form of crystals the one induced by the corpuscular beam  Molecules and by their inclusion in non-conductive Hydrocarbon polymers. Such materials have a high especially in the infrared Dielectric constant and low absorption. A particularly high dielectric constant, as for Applications in infrared at 1.3 µm and 1.55 µm are required derlich, can be achieved if the structures and Layers of amorphous silicon can be produced (e = 12). Compounds made of silicon can advantageously be used for this purpose Halogens that also have multiple silicon atoms in the molecule used to be amorphous with the silicon included Precipitate corpuscular beam-induced deposition. For example, the silicon can be made from SiJ₄ (silicon tetraiodide) be deposited. This is a low temperature process and does not contain silicon contaminants Hydrocarbons.

The water in the residual gas atmosphere becomes too low Impurities are precipitated as HJ or SiO₂ and contaminates the landfill at most in the alcohol range. Becomes Oxygen admixed by external gas supply, so can Layers of changing composition made of silicon and Silicon oxide (e = 2.25) can be produced. Such Layers form highly effective mirrors and it is enough few layers for a high reflection coefficient the layer. By reducing the number of layers decreases also the possible absorption and insertion loss of the Element.

By using the easily controllable corpuscular beam in the scanning corpuscular microscope is at 100 nm exact placement of the exposure field to the effective zone of the laser with image processing and scanning microscopy possible. Through the macro control of the adjustment and the  Exposure is the exposure process program-guided automatable.

By the computer guidance of the exposure and the Precalculation of the dose distribution measured accordingly Gradation curves of the coating or deposition process, can be round, elliptical and others geometric shapes of the elements, even with a Deflection prism and oriented the laser beam leading lens combinations with the mirrors and grids Execute united and precise in one optical element adjust.

The adjustment and the manufacturing process are in one summarized and the conventional method around consider at least an order of magnitude of precision. Here is the easy controllability and image rotation with the Corpuscular beam exposure a z. B. laser deposition superior method of building the elements.

Due to the computer-controlled variation of the gas type and the Effective precursor material can change layers Thickness of different materials with predetermined Properties are deposited. This is the case for gases Known control option via mass flow controller to use. For solid substances as precursors there is one Device with bistable valves electrically controllable Valve slides between the sample chamber and the reservoir installed with short distances but high conductance, to use. This arrangement is directly beneficial installed the table of the corpuscular beam scanning device and if possible per reservoir with heating and cooling Peltier elements equipped.  

Fig. 1 shows a schematic of the lithography tool for additive lithography with varying gas supply, which is first described in terms of its apparatus components, and is then also used to illustrate the method steps.

An xy table with environmental chamber 1 is used to carry out the process, on which the fiber laser to be treated is located. It is controlled by an infe rometer and table motor actuator 2 , which is connected to a control computer 3 for the beam movement, table position and material selection. Further connections from here lead to the reservoir 4 , to heating and cooling elements 5 and to valves 6 for the materials and the connection to the vacuum pump, on the one hand, and via D / A converter 7 for the x / y deflection to the deflection coils 8 for the beam deflection in the corpuscular beam device (scanning electron microscope) 9 with the field emission cathode 10 , a Faraday cage 11 and a secondary electron detector 12 on the other hand.

In additive lithography with corpuscular rays a compression process depending on the exposure time to watch the production of multilayer Layers must be taken into account.

FIG. 2 shows the influence of the exposure time per pixel by varying the pixel exposure time to compress the deposited material and examining the material composition in a scanning microscope.

In Fig. 3, the strength for a 20% gold ball suspension with gold spheres of 1.6 nm diameter calculated real and imaginary part is given of the refractive index metal-filled nanokri stalliner materials.

Fig. 4 shows a TEM of a thin-filled nanocrystals polymer / Pt layer,

FIG. 5 shows the construction method of a dielectric single layer for reducing reflection and as a λ / 4 plate for phase shifting.

Fig. 6 shows the structure of dielectric multilayers as a highly reflective mirrors or anti-reflection layer.

FIG. 7 shows the structure of a grating in addition to the highly reflecting mirror made of dielectric multilayers.

Fig. 8 shows schematically the adjustment of the exposure area on an M-profile fiber laser. In addition to the x / y deflections 21 to 24 , the core for pump light 25 , the fiber core 26 and cladding for wave guide 27 and a focusing window 28 are indicated from the inside out.

FIG. 9 shows schematically how the combination of the λ / 4 layer 30 with the dielectric multilayer mirror 31 with the prism is arranged on the exit window of the M-profile fiber laser. Such elements are required in order to bring the single-mode light of the individual areas of the cladding zone of the M-profile laser into the phase-coherent state, to tune it as an amplifier by correctly selecting the reflectivity of the mirror, and to adjust the light of this single-mode area to individual single-mode Uncouple fibers with change of direction and guide them. A lens can also be installed in this element in order to compensate for the beam expansion by diffraction and to focus the light on the fiber.

The diagram of the adjustment of the optical elements to the areas of the effective zone of the fiber laser and the exposure area to the fiber laser with the aid of image processing is shown in FIG. 8. There are several steps involved.

First, the Position of the optically active zone of the fiber laser in the Corpuscular beam scanning microscope can be measured with it the position coordinates of the zone to be occupied relative to the edge of the fiber laser are known. After the Fiber laser or a fiber laser bundle in it Corpuscular beam optical exposure device, with in the Height and mutual position pre-adjusted positions of the Fiber laser, is used to measure the rough adjustment of the Fiber lasers give each other an image of the ensemble at low Magnification drawn into the image memory of the device and the locations of the individual fiber lasers with the focus Determination localized.

The fiber laser to be assigned is then selected and with the motorized table using the coordinates previously determined. Now at increased magnification another image of a fiber laser drawn in and the beam in a selected area outside the optically active area of the fiber laser, e.g. B. in the edge area of the outer cladding (protective cover of the active area). This focus can automated because there is enough information on the edge tion is available.

By gradually increasing the magnification in the focus field will be the best focus and stigmatization enough. Now is predetermined in the overview Places in opposite places of the edge by Kon  trast measurement along a line perpendicular to the edge thereof Location with accuracy of 1 pixel at 3-4 points of the Diameter determined. This is the fiber laser center and so every point of the surface of the fiber laser to 0.3 µm (512 pixels, or 0.15 µm at 1024 pixels). Is a Angular orientation of the structures on the fiber laser required with the corpuscular beam microscope this is determined or only with the exposure of the applied structure an orientation mark applied and be created visibly for later adjustments.

With the known edge distance of the active zone and its Position relative to the center of the laser is made according to the Type of laser the position of the λ / 4 plates, mirrors and Prisms with the coordinates of the center and location of the Major axes, angles, and calculated these coordinates and Angle of the exposure data record in the form of a translation and rotation. After that, the structured optical element and the brand exposed and now lies with 0.1 µm accuracy and less than 0.1 degree angular accuracy the active zone.

The structure can also have one or more prisms on ver different places are superimposed so that a variation the radiation directions of the single-mode zones of the fiber laser can be preset.  

The image processing steps take about 2 minutes and can be programmed through the use of permanently programmed algorithms required image areas and image point to be recorded pay in the exposure range of some Seconds. With this procedure production at economically interesting costs such optical components and their marking in Manufacturing process to be carried out.

Claims (7)

1. Process for the production of structured, λ / 4 platelets, mirrors, gratings and prisms on three-dimensional surfaces using additive corpuscular beam lithography in a vacuum process, characterized in that after the fiber laser or a fiber laser has been introduced The optically active zones and thus the position coordinates of the zone (s) to be covered are measured relative to the edge with increasing magnification, then the effective layers to be applied and three-dimensional structures of optical components by means of a program-controlled manufacturing process based on the computer-controlled corpuscular beam-induced deposition , the end faces of the fiber laser to be occupied by a computer-controlled valve with a material layer made of a molecular beam and this material assignment is maintained during the exposure after the positioning for the duration of the exposure, or after the requirements of the structure to be generated, the material of the molecular beam is changed by valve control and the exposure is timed with the necessary safety times for exclusive occupancy. 2. The method according to claim 1, characterized in that suitable for secure covering with material layers  Refractive index or dielectric constant previously calibration curves used for program control as tables be available. 3. The method according to claim 1-2, characterized in that after determining the fiber laser center coordinates for the exposure of a given layer profile previously calculated and in a retrievable database stored dose distribution and material supply-Ab follow the calculated center coordinates is net, and so the layer sequence to be generated and Profile exposure highly precise on the area of Fiber laser core is exposed. 4. The method according to claim 1-3, characterized in that the mirrors that are applied along the laser zone den, so in their reflectivity and in their trans mission that a single mode zone of the active area first as a single-mode laser wire vibrates, making the neighboring zones coherent and can be defined in a fixed phase (injection mode locking). 5. The method according to claim 1-4, characterized in that in areas with oscillation excited in opposite phases Laser material by adding this vibration state add a λ / 4 plate under the mirror so influenced becomes that this light is coherent and in phase with the exciting light wave swings. 6. The method according to claim 1-5, characterized in that in the manufacture of lenses on the active zone of Solid state lasers, following the steps as in the ge described claims described for adjusting the Lens with minimal dose only near the with  working area of the lens to be covered is used with two narrow image areas that are in the y direction, d. H. lower are arranged right to the edge of the laser and left and to the right of the active zone are pictures and measurement data be fed to the edge of the edge of the laser materials and with a third rectangular area that only the current contact of the Lasers includes, if possible without the laser base material or touching construction material over the active zone, those for determining the center of gravity of the current contact area ches required measurement data are recorded that afterwards by determining the center of gravity the center of the same and from the edge and the middle position of the Stromkon clocks the center and the angular orientation of the elliptical hyperbolic lens fixed on the laser be placed. 7. Device for producing structured λ / 4 plates surfaces, mirrors, gratings and prisms on three-dimensional Surfaces using additive cor muscular beam lithography with vacuum chamber, control computer, locks, molecular beam guidance and venti len, characterized, that as an exposure device, a raster corpuscular beam Microscope with motor table with control, with image processing processing and computer-aided beam control or a lithography device with image processing add-on, or a special beam guiding and image measuring device to the corpuscular beam of a scanning microscope is coupled with which, in connection with the Control computer, permanently programmed the necessary Work steps are processed one after the other.