CN1936634A - Method for realizing optical point joint seal in optical-fiber close-packed array - Google Patents

Abstract

The invention discloses a method for realizing close connection of light spots in an optical fiber close-arranged line array. It includes the following steps: 1) drawing one end of a standard single-mode optical fiber into a micro-fiber with a diameter of 5 to 25 microns, which includes a standard optical fiber, a transition zone and a micro-fiber; 2) spacing the ends of the above-mentioned multiple micro-fibers horizontally Arranged in parallel on a silicon substrate with a V-shaped groove or a magnesium fluoride substrate with a rectangular groove coated with a magnesium fluoride film on the surface; A glass sheet or a magnesium fluoride thin plate is fixed to the substrate by ultraviolet glue to form a micro-fiber close-packed array; 4) The end of the standard optical fiber is connected to the semiconductor laser through the FC interface, and the close-packed micro-fiber array end outputs an array of light spots. The invention realizes close arrangement of light spots in which multiple optical fibers are densely arranged on the horizontal line; improves imaging precision in a laser phototypesetting system; increases focal depth, and reduces requirements on position precision during film exposure.

Description

A method to realize close connection of light spots in optical fiber close-packed line array

technical field

The invention relates to providing the optical fiber close-arranged line array technology in a laser phototypesetting system, in particular to a method for realizing the close connection of light spots in the optical fiber close-arranged line array.

Background technique

In laser scanning equipment such as laser phototypesetting machines, laser photoplotters, and direct plate-making machines, a main solution to realize multi-channel optical scanning is to use multiple semiconductor lasers and multiple optical fibers to construct a line array of light spots as a The object plane is then imaged on the image plane (film surface) in a certain proportion through the imaging system, thereby realizing multi-channel scanning.

However, due to the structure of ordinary optical fibers, the light in the optical fiber is only distributed in a small area in the center. For example, the size of a typical multimode optical fiber is 125 microns in outer diameter and 62.5 microns in core diameter (light guide part). If it is single-mode The fiber core diameter is only 8-10 microns. Even if the fibers are arranged without gaps, the light spots emitted by the close-packed array are separated (see Figure 6). Taking the light-emitting end face of the optical fiber array as the object plane, the light spots obtained on the image plane are also separated after passing through the imaging system, which cannot meet the scanning requirements. If the defocusing method is used to expand the spot diameter of the image plane, although the gap between the spots can be bridged, the edge quality of the spot will be sacrificed.

In order to solve this problem, some optical fibers are densely arranged at a certain angle, and the dots are controlled through the delay on the circuit, so that the light spots are densely arranged. This method is successful, but the control circuit is complicated and cannot solve the problem of short depth of focus of the focused light spot.

Contents of the invention

The purpose of the present invention is to propose a method for realizing close connection of light spots in a densely packed optical fiber line array in order to solve the problems existing in the prior art.

It includes the following steps:

1) Drawing one end of a standard single-mode fiber into a micro-fiber with a diameter of 5-25 microns, which includes a standard fiber, a transition zone and a micro-fiber;

2) Arrange the ends of the above-mentioned multiple micro-fibers in parallel at intervals on a silicon chip with a V-shaped groove or a magnesium fluoride substrate with a rectangular groove coated with a magnesium fluoride film on the surface, and the arrangement interval is the diameter of the micro-fiber plus The upper adjacent micro-fiber spacing d, where, $d\&Greater\; Equal;\frac{\mathrm{\λ}}{{\mathrm{\π}\&Center\; Dot;\mathrm{no}}_1\sqrt{{\sin }^2{\mathrm{\θ}-({\mathrm{no}}_2/{\mathrm{no}}_1)}^2}}$ In the formula: λ is the wavelength of light in the fiber, n ₁ is the refractive index of the fiber, n ₂ is the refractive index of air, and θ is the incident angle of light in the fiber;

3) A glass sheet coated with a magnesium fluoride film or a magnesium fluoride thin plate is arranged above the micro-optical fiber on the substrate, and fixed to the substrate by ultraviolet glue to form a close-packed array of micro-fibers;

4) The end of the standard optical fiber is connected to the semiconductor laser through the FC interface, and the end of the densely packed micro-fiber array outputs an array of light spots.

Beneficial effects of the present invention:

1) Realize the close arrangement of light spots in which multiple optical fibers are densely arranged on the horizontal line;

2) Improving the imaging accuracy in the laser phototypesetting system;

3) The depth of focus is increased, which reduces the requirement for positional accuracy during film exposure.

Description of drawings

Fig. 1 is a schematic diagram of a close-packed micro-optical fiber of the present invention;

Figure 2 is a schematic diagram of a standard single-mode optical fiber with a diameter of 125 microns with the coating removed;

Figure 3 is a schematic diagram of a micro-optical fiber with a diameter ranging from 5 to 25 microns processed by a high-temperature drawing process using a single-mode optical fiber with the coating removed;

Fig. 4 is a schematic diagram of micro-optical fibers of the present invention densely arranged on a silicon substrate with a V-shaped groove;

Fig. 5 is a schematic diagram of micro-optical fibers of the present invention densely arranged on a magnesium fluoride substrate with rectangular grooves;

Figure 6 is a schematic diagram of the distribution of focused light spots when standard optical fibers are densely packed;

Fig. 7 is a schematic diagram of the distribution of focused light spots when micro-optical fibers are densely packed;

Figure 8 is a schematic diagram of the depth of focus of the image plane after focusing through the lens when the micro-fibers are densely packed;

Figure 9 is a schematic diagram of the focal depth of the image plane after the lens lens is focused when a standard single-mode optical fiber is used;

Fig. 10 is a block diagram of the micro-fiber close-packed array of the present invention.

Detailed ways

In order to solve the problem that the light spots in the standard optical fiber close-packed array on the existing laser phototypesetting machine cannot be closely connected, and because the distance between adjacent optical fibers is large, a large magnification focusing lens is required, which causes the problem that the depth of focus is too short and the position of the exposure point is too high. The method of micro-fiber close-packing is adopted. The micro-fiber is a thin optical fiber with a diameter of about 5-25 microns produced under laser heating after removing the coating from the standard single-mode optical fiber (as shown in Figure 3). One end of the microfiber is connected to a standard single-mode fiber through a transition zone, and the standard fiber end is connected to a semiconductor laser through a common fiber interface. In a standard optical fiber, light is transmitted only in the core diameter of the fiber with a small diameter, and the outer part of the core diameter is a cladding with a lower refractive index than the core diameter; while in a microfiber, light is transmitted within the entire diameter of the microfiber, and the microfiber The air layer around the fiber is the cladding. If the microfiber is directly in contact with the fiber or a material with a higher refractive index than the fiber, light energy can easily be coupled into the material in contact with it. One of the key problems of this invention is to solve the cladding problem when the micro-fibers are densely packed.

In order to prevent optical energy coupling between arranged adjacent micro-fibers, a certain gap d (as shown in FIG. 1 ) needs to be maintained between adjacent micro-fibers. The size of the gap is:

$\mathrm{<span\; class="notranslate">\; d</span>}<span\; class="notranslate">\; \&Greater\; Equal;</span>\frac{\mathrm{<span\; class="notranslate">\; \&lambda;</span>}}{{\mathrm{<span\; class="notranslate">\; \&pi;</span>}<span\; class="notranslate">\; \&CenterDot;</span>\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}\sqrt{{\mathrm{<span\; class="notranslate">\; sin</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}\mathrm{<span\; class="notranslate">\; \&theta;</span>}<span\; class="notranslate">\; -</span>{<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; /</span>{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}}$

In the formula: λ is the wavelength of light in the fiber, n ₁ is the refractive index of the fiber, n ₂ is the refractive index of air, and θ is the incident angle of the light in the fiber.

In order to arrange the micro-fibers at equal intervals, the micro-fibers are arranged on a silicon substrate with a V-shaped groove or a magnesium fluoride substrate with a rectangular groove. Assume that the diameter of the micro-fiber is D, and the distance between adjacent micro-fibers is d. The distance between adjacent V-shaped grooves or rectangular grooves is D+d. If a silicon wafer etched with a V-shaped groove is used, the silicon wafer needs to be plated with a low-refractive index dielectric film (such as a magnesium fluoride film). The V-shaped groove on the silicon wafer is obtained by photolithography and wet etching; the rectangular groove is processed by photolithography and plasma beam etching. The upper end of the arranged micro-optical fiber array is pressed with a magnesium fluoride sheet or a glass sheet coated with a magnesium fluoride film on the surface, and the magnesium fluoride sheet or glass sheet is fixed to the substrate below by ultraviolet glue (as shown in Figure 4 and Figure 5 Show). Since the diameter of the micro-fiber is very thin, in order to prevent the breakage of the micro-fiber, the substrate and the part of the standard optical fiber close to the transition zone should be fixed with the base through ultraviolet glue (as shown in Figure 10) to form an integral body.

If the conventional method is used to closely arrange standard optical fibers, the distance between the centers of adjacent optical fibers is 125 microns, and if the resolution of the film is required to be 2540dpi, the magnification of the imaging lens required for imaging the densely packed optical fiber spot array on the film is 12.5 times. The larger the magnification of the lens, the shorter the depth of focus; if a 12.5x imaging lens is used, the position of the film is very high, and it is difficult to be practical (as shown in Figure 9). If micro-fibers with a diameter of 20 microns are densely arranged, the distance between adjacent micro-fibers is 4 microns, and the center distance between adjacent micro-fibers is 24 microns. The magnification of the imaging lens is 2.4 times, the magnification of the lens is greatly reduced, the depth of focus is greatly increased (as shown in Figure 8), and the requirements for the position accuracy of the focusing lens to the film are greatly reduced.

Example 1

1) Stripping the coating from the single-mode optical fiber;

2) Converge the high-power laser onto the optical fiber through the focusing mirror, the heat generated by the laser melts the optical fiber, and the micro-fiber with a diameter of 20 microns is obtained by stretching the optical fiber;

3) On the silicon wafer, etch out V-shaped grooves with a spacing of 24 microns in parallel, and plate a magnesium fluoride film with a thickness of 0.3 to 1 micron on the surface of the silicon wafer etched with V-shaped grooves; The optical fiber ends are arranged parallel and horizontally in the V-shaped groove on the silicon wafer, and then the micro-fiber array is covered with a glass sheet coated with a 0.3-1 micron film on the surface, and the glass sheet and the silicon chip are fixed by ultraviolet glue, as shown in Figure 4 Show.

4) Fix the silicon chip and the standard optical fiber near the transition area to the base with ultraviolet glue, and connect the end of the standard optical fiber to the FC interface connected to the semiconductor laser (as shown in Figure 10).

5) In step 2), the distance between the laser convergence point and the heated fiber is adjusted to obtain micro-fibers with different diameters.

Example 2

1) Stripping the coating from the single-mode optical fiber;

2) Converge the high-power laser onto the optical fiber through the focusing mirror, the heat generated by the laser melts the optical fiber, and stretches the optical fiber to obtain a micro-fiber with a diameter of 10 microns;

3) On the magnesium fluoride substrate, parallel grooves with an adjacent interval of 13 microns, a width of 8 microns, and a depth of 5 microns are etched by photolithography and plasma beams, and the micro-optical fibers are horizontally arranged in parallel in the parallel grooves on the substrate. A magnesium fluoride thin plate is covered on the micro-fiber array, and the magnesium fluoride thin plate and the substrate are fixed by ultraviolet glue, as shown in FIG. 5 .

4) Fix the magnesium fluoride substrate and the standard optical fiber near the transition area to the base with ultraviolet glue, and connect the end of the standard optical fiber to the FC interface connected to the semiconductor laser (as shown in Figure 10).

5) In step 2), the distance between the laser convergence point and the heated fiber is adjusted to obtain micro-fibers with different diameters.

Claims (2)

1. A method for realizing close connection of light spots in an optical fiber close-packed line array, characterized in that it comprises the steps: 1) Drawing one end of a standard single-mode fiber into a micro-fiber with a diameter of 5-25 microns, which includes a standard fiber, a transition zone and a micro-fiber; 2) Arrange the ends of the above-mentioned multiple micro-fibers in parallel at intervals on a silicon substrate with a V-shaped groove or a magnesium fluoride substrate with a rectangular groove coated with a magnesium fluoride film on the surface, and the arrangement interval is the diameter of the micro-fiber plus The upper adjacent micro-fiber spacing d, where, $d\&Greater\; Equal;\frac{\mathrm{\&lambda;}}{\mathrm{\&pi;}\&CenterDot;{\mathrm{no}}_1\sqrt{\mathrm{the\; si}{\mathrm{no}}^2\mathrm{\&theta;}-({\mathrm{no}}_2/{\mathrm{no}}_1{)}^2}}$ In the formula: λ is the wavelength of light in the fiber, n ₁ is the refractive index of the fiber, n ₂ is the refractive index of air, and θ is the incident angle of light in the fiber; 3) A glass sheet coated with a magnesium fluoride film or a magnesium fluoride thin plate is arranged above the micro-optical fiber on the substrate, and fixed to the substrate by ultraviolet glue to form a close-packed array of micro-fibers; 4) The end of the standard optical fiber is connected to the semiconductor laser through the FC interface, and the end of the densely packed micro-fiber array outputs an array of light spots. 2. A method for realizing close connection of light spots in an optical fiber close-packed line array according to claim 1, characterized in that the drawing method of the micro-optical fiber is: 1) Stripping the coating from the single-mode optical fiber; 2) Converge the high-power laser onto the optical fiber through the focusing mirror, the heat generated by the laser melts the optical fiber, and obtains a fine-diameter micro-fiber by stretching the optical fiber; 3) Adjusting the distance between the laser convergence point and the heated fiber to obtain micro-fibers with different diameters.

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