CA2111010A1 - Method of finely polishing planar optical elements - Google Patents
Method of finely polishing planar optical elementsInfo
- Publication number
- CA2111010A1 CA2111010A1 CA 2111010 CA2111010A CA2111010A1 CA 2111010 A1 CA2111010 A1 CA 2111010A1 CA 2111010 CA2111010 CA 2111010 CA 2111010 A CA2111010 A CA 2111010A CA 2111010 A1 CA2111010 A1 CA 2111010A1
- Authority
- CA
- Canada
- Prior art keywords
- optically transparent
- polishing
- transparent surface
- cavity
- planar optical
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B24—GRINDING; POLISHING
- B24B—MACHINES, DEVICES, OR PROCESSES FOR GRINDING OR POLISHING; DRESSING OR CONDITIONING OF ABRADING SURFACES; FEEDING OF GRINDING, POLISHING, OR LAPPING AGENTS
- B24B1/00—Processes of grinding or polishing; Use of auxiliary equipment in connection with such processes
- B24B1/04—Processes of grinding or polishing; Use of auxiliary equipment in connection with such processes subjecting the grinding or polishing tools, the abrading or polishing medium or work to vibration, e.g. grinding with ultrasonic frequency
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B24—GRINDING; POLISHING
- B24B—MACHINES, DEVICES, OR PROCESSES FOR GRINDING OR POLISHING; DRESSING OR CONDITIONING OF ABRADING SURFACES; FEEDING OF GRINDING, POLISHING, OR LAPPING AGENTS
- B24B13/00—Machines or devices designed for grinding or polishing optical surfaces on lenses or surfaces of similar shape on other work; Accessories therefor
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B24—GRINDING; POLISHING
- B24B—MACHINES, DEVICES, OR PROCESSES FOR GRINDING OR POLISHING; DRESSING OR CONDITIONING OF ABRADING SURFACES; FEEDING OF GRINDING, POLISHING, OR LAPPING AGENTS
- B24B19/00—Single-purpose machines or devices for particular grinding operations not covered by any other main group
- B24B19/22—Single-purpose machines or devices for particular grinding operations not covered by any other main group characterised by a special design with respect to properties of the material of non-metallic articles to be ground
- B24B19/226—Single-purpose machines or devices for particular grinding operations not covered by any other main group characterised by a special design with respect to properties of the material of non-metallic articles to be ground of the ends of optical fibres
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B24—GRINDING; POLISHING
- B24B—MACHINES, DEVICES, OR PROCESSES FOR GRINDING OR POLISHING; DRESSING OR CONDITIONING OF ABRADING SURFACES; FEEDING OF GRINDING, POLISHING, OR LAPPING AGENTS
- B24B31/00—Machines or devices designed for polishing or abrading surfaces on work by means of tumbling apparatus or other apparatus in which the work and/or the abrasive material is loose; Accessories therefor
Landscapes
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Grinding And Polishing Of Tertiary Curved Surfaces And Surfaces With Complex Shapes (AREA)
- Grinding-Machine Dressing And Accessory Apparatuses (AREA)
- Finish Polishing, Edge Sharpening, And Grinding By Specific Grinding Devices (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
The present invention relates to a method of finely polishing an optically transparent surface with a polishing liquid containing abrasive particles. The polishing mixture, while subjected to ultrasonic agitation, is contacted with an optically transparent surface under conditions effective to polish finely that surface. The abrasive particles typically have a size of up to 1 micron.
This process is particularly useful in smoothing the optically transparent surfaces which define cavities or sidewalls for planar optical elements in optical waveguides.
The present invention relates to a method of finely polishing an optically transparent surface with a polishing liquid containing abrasive particles. The polishing mixture, while subjected to ultrasonic agitation, is contacted with an optically transparent surface under conditions effective to polish finely that surface. The abrasive particles typically have a size of up to 1 micron.
This process is particularly useful in smoothing the optically transparent surfaces which define cavities or sidewalls for planar optical elements in optical waveguides.
Description
Hagerty-Jones 4-1 - 2 1 ~
M13THOD OF FII~ELY POLISHING PIANAR OPTICAL }3Ll~TS
FI~LD OF T~ ~VENTION
The present invention relates to a method of finely polishing planar optical elements used in conjunction with optical waveguides.
B~CKGROUN~ OF ~E_I~VENTION
~emote information is commonly transmitted by passing light waves through an optical waveguide, for example, an optical fiber. one type of optical wavegulde device of current interest is a planar optical waveguide component. Such optical wave~uide devices include a guide or core layer sandwiched between two cladding layers of media with lower indices of refraction than that of the guide layer. Increasingly, such optical waveguide devices ¦ include an integral planar optical element in the optical path of the waveguide. Such ele~ents include lenses, gratings, and microprisms.
I Where manufacturing integral optical elements, a ! techniquQ of reactive ionic etching is sometimes used, see ~ 25 e.g. U.S. Patent No. 4,865,453 and U.S. Patent No.
,' 4,740,551.
one problem encountered with reactive ionic etching is the formation of rough cavity surfaces. AS a ~J i 1 1 ~ 1 0 result, the integral optical elements formed in such cavities tend to have rough surfaces. Due to the small and isolated nature of such cavities, it is difficult to eliminate such roughness. These defects cause light scattering or loss which reduces the performance of the planar optical element. Such performance is generally expressed in terms of excess loss -- i.e. the amount of -light loss above the loss in each optical channel due to optical circuitry splitting.
In M.M. Minot, et al., "A New Guided-Wave Lens Structure," Journal of Lightwave Technology, vol. 8, no. 12 (l990) a cavity is formed in the host waveguide by reactive ionic etching. The walls of the resulting cavities are then ~ade smoother by a wet chemical polishing etch. A
lens-shaped waveguide is then formed in the cavity by evaporative deposition of SiO2 in the bottom of the cavity as a cladding layer. Glass, which acts as a guiding layer, is then diode sputter deposited in the cavity.
This technique is not commercially useful, because long treatment periods must be utilized. The present invention is directed to overcoming the surface roughness problem encountered in integral optical elements -in a more efficient and cost effective fashion.
SUMMARY OF THE I~V~NTION
. ' The present invention is directed to a method of finely polishing an optically transparent surface with a polishing liquid containing abrasive particles. The polishing liquid, while subjected to agitation, is contacted with an optically transparent surface under conditions effective to polish finely the optically ~ 35 transparent surface. Such aqitation is desirably !', ultrasonic with the abrasive particles preferably having a size of up to 1 micron. The process is particularly useful ., -~ 2:~ 1` iala . .
where the optically transparent surface defines a cavity configured to define a planar optical element.
The procedure of the present invention substantially reduces the roughness of optically transparent cavity surfaces. When a planar optical element is subsequently formed in the cavity, the smoothness of th~
cavity surfaces causes the conforming surfaces of the planar optical element to be smooth. This substantially reduces the excess loss in the waveguide.
BRIEF ~ESCRIPTION OF TH~ DRAWINGS
FIG. 1 is a schematic view of an ultrasonic polishing apparatus in accordance with the present invention.
FIG. 2 is a photograph taken with a scanning electron microscope of a cavity in an optical waveguide which has not been subjected to ultrasonic polishing.
FIG. 3 is a photograph taken with a scanning electron microscope of a cavity in an optical waveguide which has been subjected to one hour of ultrasonic polishing in accordance with the present invention.
FIG. 4 is a photograph taken with a scanning electron microscope of a cavity in an optical waveguide which has been subjected to 2 hours of ultrasonic polishing in accordance with the present invention.
FIG. 5 is a photograph taken with a scanning electron microscope of a cavity in an optical waveguide which has been subjected to ultrasonic polishing for 4 hours in accordance with the present invention.
~AILED DESCRIPTION OF THE INVENTION AN~ DRAWINÇ~
The present invention relates to a method of finely polishing an optically transparent surface with a polishing mixture containing abrasive particles. The .
.. . . ..
al3 ~ `
-4- .
polishing mixture, while subjected to ultrasonic agitation, is contacted with an optically transparent surface under conditions effective to polish finely the optically transparent surface. This contact preferably involves immersing the surface in the polishing mixture.
FIG. 1 is a schematic view of an apparatus for ultrasonic polishing in accordance with the present invention. In this device, generator 10, which produces electrical output pulses, comprises a device for rapidly switching high-voltage DC on and off to produce pulses.
Several known devices can accomplish such switching, and they include blocking oscillators, multivibrators, flip-flops, tunnel diodes, and others.
Pulses from generator 10 are supplied to transducer 8 which moves mechanically in response to the pulses. Several generally known devices can be made pulse-responsive to serve as transducer 8, and these include crystals, piezo-electrics, electrostrictive, magnetostrictive devices, and others.
Generator 10 is designed to operate in the ultrasonic frequency range of 20-45 kilohertz at an agitation power level of 150 to 200 watts. ~ransducer 8 is caused to operate under these conditions as a result of its being coupled to generator 10. In turn, transducer 8 is attached to the base or a ~ide of tank 6 to vibrate liquid L under these conditions. Transducer 8, generator 10, and tank 6 are preferably together embodied in a conventional -~-I ultrasonic cleaning unit. one example of such a unit is the Branson D-150 Ultrasonic cleaner manufactured by Branson Equip~ent Co., Shelton, CT.
Planar optical device D is placed in container 2 I for fine polishing in accordance with the present I invention. A weighted cover 4 is then placed over ;:
,,-- 21.,i{31',~
container 2 to keep it in contact with the bottom of tank 6. Also held within container 2 is polishing mixture P
which is subjected to ultrasonic conditions as the high intensity positive displacements produced in liquid L are transmitted through the wall of container 2. In turn, such displacements of polishing mixture P impinge planar optical device D. During operation of the apparatus of FIG. 1, the level of liquid L should be maintained at a height sufficient to ensure transmission of such positive displacements. Generally, a depth of 2.0 to 2.6 centimeters, preferably 2.54 centimeters, of liquid in tank 6 is sufficient.
Instead of utilizing the arrangement of FIG. 1, ~5 the ultrasonic polishing process of the present invention can employ a workholder or clamp to immerse planar optical device D in polishing mixture P of container 2. This technique is disclosed in U.S. Patent Nos. 2,796,702 and 3,564,775 to Bodine, Jr. which are hereby incorporated by reference.
In another alternative embodiment of the present invention, the process can be carried out without utilizing ~ container 2 and cover 4. Polishing mixture P and planar 3 25 optical device D can be placed directly in tank 6 for fine polishing.
Polishing mixture P is prepared from a mixture of a liquid and abrasive particles. The polishing mixture has a volumetric ratio of liquid to abrasive particles of 1:0.4 to 1:2.5, preferably 1:1.
, :
Polishing can be carried out at any temperature which is not detrimental to tne optically transparent surface being polished. Temperatures of not more than 20 to 50-C should be used with room temperature being .
a l ~
preferred. If need be, ice can be added to liquid L to ensure that it is not overheated by transducer 8.
Generally, the longer polishing is carried out, the smoother the optically transparent surfaces become.
Polishing times of about 1 to 4 hours are usually satisfactory.
The abrasive particles preferably have a size of up to 1 micron, more preferably .l to .3 microns. These particles are made from aluminum oxide, glass, diamond dust, carborundum, tungsten carbide, silicon carbide, boron carbide, and mixtures thereof. Preferably, aluminum oxide powder with a .3 micron particle size is utilized.
The liquid component of polishing mixture P can be any liquid suitable for slurrying the above abrasive particles. Such liquids include tap water and deionized water.
The fine polishing method of the present invention is useful in treating optically transparent surfaces which define a cavity or sidewall in an optical waveguide. Such cavities or sidewalls are formed by subjecting optical waveguides to reactive ionic etching and have a configuration corresponding to that of a planar optical element. After the cavity or sidewall is formed, it is finely polished in accordance with the present invention. A planar optical element is then formed in the polished cavity in accordance with the procedure of U.S.
Patent Nos. 4,868,453 to Gidon, et al. and 4,740,951 to Lizet, et al. and M.M. Minot, "A New Guided-Wave Lens Structure, n Journal of Lightwave Technology, vol. 8, no. 12 (1990), all of which are discussed above. Suitable planar optical element configurations are those of a geodesic component, a Luneberg lens, a Fresnel lens, a grating lens, a TIPE lens, and other similar microcomponent devices.
- 2 ~
Several techniques are known for producing such planar optical elements in planar integrated optical devices. The following references disclose suitable procedures: U.S. Patent No. 4,712,856 to Nicia for geodesic components; Suhara, et al., "Graded-Index Fresnel ~ -~
Lenses for Integrated opticS," Ap~lied O~tics, vol. 21, no. ~-11, pp. 1966-71 (1982) for Fresnel lenses: Columbini, "Design of Thin-film Luneberg-type Lenses for Maximum Focal Length Control," A~Dlied optics, vol. 20, no. 20, pp. 3589-93 (1981) for Luneberg lenses; and Hatakoshi et al., "Waveguide Grating Lenses for Optical Couplers," A~plied Optics, vol. 23, no. 11, pp. 1749-53 (1984) for grating lenses. Another technique has been developed where planar optical waveguides and components therein are fabricated using polymers, e.g., Fan, et al., EPO Patent Publication No. 0,446,672.
Geodesic lenses are characterized by a surface indentation in the top of the planar optical waveguide.
Geodesic lenses require tight control during the manufacture of this surface indentation in order to keep scattering losæes at transition points to a minimum.
Luneberg lenses, which are a subclass of geodesic lenses, require the use of a lens material which has a higher index of refraction than the planar optical wave~uide substrate with which it is used.
Fresnel lenses, which are similar to zone plates in bulk optics, rely on phase shifting and/or absorption to obtain the desired focusing effect. This phase shifting is achieved through a series of half-period zones which are applied to a planar optical waveguide. For a more detailed 1 35 discussion of the use of Fresnel lenses in planar optical waveguides, see Ashley et al., "Fresnel Lens in a Thin-film ~ 2 i ~ 0 Waveguide", Applied Physics Lette~s, vol. 33, pages 490-92 ---(1978).
Other techniques for producing planar optical elements in optical waveguides are disclosed in U.S. Patent Application Serial No. 840,74g to Bhagavatula, which is hereby incorporated by reference.
Optically transparent surfaces treated in accordance with the present invention generally have a surface roughness which is substantially smoother than that encountered after reactive ionic etching. When surfaces of an optical waveguide cavity are finely polished in this fashion before formation of a planar optical element in the cavity, the waveguide has substantially less excess loss than waveguides which have not been polished in this fashion. Thus, optical waveguides treated in accordance with the present invention exhibit substantially better performance than those not subjected to polishing.
EXAMPLES
Exampl~ 1 An optical waveguide with a cavity formed by reactive ionic etching was subjected to a buffered oxide etch with a modified HF buffered solution for 30 seconds at an etch rate of 400 Angstroms per minute. After completion of the buffered oxide etch treatment, a photograph of the optical waveguide was taken with a scanning electron microscope. See Figure 2. This photograph shows that the cavity surfaces have significant roughness.
~xample 2 An optical waveguide with a cavity like that of Example 1 was subjected to a buffered oxide etch according to the procedures set forth in Example 1.
~7`~s ~
The waveguide was then placed in a 30 milliliter beaker to which has been added a polishing mixture -~
formulated from 10 milliliters of 0.3 micron alumina powder and 10 milliliters of water. The beaker was then placed in the tank of a Branson D-lso ultrasonic cleaner and a weighted plastic cover was put on top of the beaker to ensure that it remained in good contact with the base of the ultrasonic cleaner. The ultrasonic cleaner tank was then filled to a height of 2.54 centimeters of water so that ultrasonic vibrations were transmitted to the beaker contents. The ultrasonic cleaner was then turned on and operated for a period of 1 hour.
:
After completion of the ultrasonic treatment, the optical waveguide was removed and a photograph of it was taken with a scanning electron microscopeO This photograph is FIG. 3. A comparison of FIGS. 2 and 3 show that the fine polishing procedure of the present invention produces a substantially smoother cavity.
Exampl* 3 The test procedure of Example 2 was repeated except that the ultrasonic polishing stage was carried out for 2 hours. After completion of ultrasonic polishing, the optical waveguide was removed from the polishing mixture and a photograph of it was taken with a scanning electron microscope. This photograph is FIG. 4. A comparison of FIG. 4 with FIGS. 2 and 3 shows that increasing the ultrasonic polishing time enhances the smoothness of the cavity walls.
~xample 4 The process of Example 2 was repeated except that the ultrasonic polishing time was 4 hours. After completion of ultrasonic polishing, the optical waveguide was removed from the polishing mixture and a photograph of it was taken with a scanninq electron microscope. This ~ 2lii~la photograph is FIG. 5. A comparison of FIG. 5 with FIGS. 2, 3, and 4 indicates that the 4 hour polishing time achieved increased smoothness of the cavity walls.
Example 5 lx8 coupler/splitter devices were made according to the design and process set forth in copending U.S. . :
Patent Application Serial No. 07/840,749, which is incorporated herein by reference. One such device was measured after processing according to Example 1 for optical performance. The mean ratio between the input power and the output power for the 8 outputs was approximately 12 dB (theoretical ratio is 9 dB for lx8 splitting).
Another such device was additionally treated according to the polishing process of Example 4. The mean excess loss was about 11 dB, an improvement of 33% from the excess loss without the inventive polishing treatment.
M13THOD OF FII~ELY POLISHING PIANAR OPTICAL }3Ll~TS
FI~LD OF T~ ~VENTION
The present invention relates to a method of finely polishing planar optical elements used in conjunction with optical waveguides.
B~CKGROUN~ OF ~E_I~VENTION
~emote information is commonly transmitted by passing light waves through an optical waveguide, for example, an optical fiber. one type of optical wavegulde device of current interest is a planar optical waveguide component. Such optical wave~uide devices include a guide or core layer sandwiched between two cladding layers of media with lower indices of refraction than that of the guide layer. Increasingly, such optical waveguide devices ¦ include an integral planar optical element in the optical path of the waveguide. Such ele~ents include lenses, gratings, and microprisms.
I Where manufacturing integral optical elements, a ! techniquQ of reactive ionic etching is sometimes used, see ~ 25 e.g. U.S. Patent No. 4,865,453 and U.S. Patent No.
,' 4,740,551.
one problem encountered with reactive ionic etching is the formation of rough cavity surfaces. AS a ~J i 1 1 ~ 1 0 result, the integral optical elements formed in such cavities tend to have rough surfaces. Due to the small and isolated nature of such cavities, it is difficult to eliminate such roughness. These defects cause light scattering or loss which reduces the performance of the planar optical element. Such performance is generally expressed in terms of excess loss -- i.e. the amount of -light loss above the loss in each optical channel due to optical circuitry splitting.
In M.M. Minot, et al., "A New Guided-Wave Lens Structure," Journal of Lightwave Technology, vol. 8, no. 12 (l990) a cavity is formed in the host waveguide by reactive ionic etching. The walls of the resulting cavities are then ~ade smoother by a wet chemical polishing etch. A
lens-shaped waveguide is then formed in the cavity by evaporative deposition of SiO2 in the bottom of the cavity as a cladding layer. Glass, which acts as a guiding layer, is then diode sputter deposited in the cavity.
This technique is not commercially useful, because long treatment periods must be utilized. The present invention is directed to overcoming the surface roughness problem encountered in integral optical elements -in a more efficient and cost effective fashion.
SUMMARY OF THE I~V~NTION
. ' The present invention is directed to a method of finely polishing an optically transparent surface with a polishing liquid containing abrasive particles. The polishing liquid, while subjected to agitation, is contacted with an optically transparent surface under conditions effective to polish finely the optically ~ 35 transparent surface. Such aqitation is desirably !', ultrasonic with the abrasive particles preferably having a size of up to 1 micron. The process is particularly useful ., -~ 2:~ 1` iala . .
where the optically transparent surface defines a cavity configured to define a planar optical element.
The procedure of the present invention substantially reduces the roughness of optically transparent cavity surfaces. When a planar optical element is subsequently formed in the cavity, the smoothness of th~
cavity surfaces causes the conforming surfaces of the planar optical element to be smooth. This substantially reduces the excess loss in the waveguide.
BRIEF ~ESCRIPTION OF TH~ DRAWINGS
FIG. 1 is a schematic view of an ultrasonic polishing apparatus in accordance with the present invention.
FIG. 2 is a photograph taken with a scanning electron microscope of a cavity in an optical waveguide which has not been subjected to ultrasonic polishing.
FIG. 3 is a photograph taken with a scanning electron microscope of a cavity in an optical waveguide which has been subjected to one hour of ultrasonic polishing in accordance with the present invention.
FIG. 4 is a photograph taken with a scanning electron microscope of a cavity in an optical waveguide which has been subjected to 2 hours of ultrasonic polishing in accordance with the present invention.
FIG. 5 is a photograph taken with a scanning electron microscope of a cavity in an optical waveguide which has been subjected to ultrasonic polishing for 4 hours in accordance with the present invention.
~AILED DESCRIPTION OF THE INVENTION AN~ DRAWINÇ~
The present invention relates to a method of finely polishing an optically transparent surface with a polishing mixture containing abrasive particles. The .
.. . . ..
al3 ~ `
-4- .
polishing mixture, while subjected to ultrasonic agitation, is contacted with an optically transparent surface under conditions effective to polish finely the optically transparent surface. This contact preferably involves immersing the surface in the polishing mixture.
FIG. 1 is a schematic view of an apparatus for ultrasonic polishing in accordance with the present invention. In this device, generator 10, which produces electrical output pulses, comprises a device for rapidly switching high-voltage DC on and off to produce pulses.
Several known devices can accomplish such switching, and they include blocking oscillators, multivibrators, flip-flops, tunnel diodes, and others.
Pulses from generator 10 are supplied to transducer 8 which moves mechanically in response to the pulses. Several generally known devices can be made pulse-responsive to serve as transducer 8, and these include crystals, piezo-electrics, electrostrictive, magnetostrictive devices, and others.
Generator 10 is designed to operate in the ultrasonic frequency range of 20-45 kilohertz at an agitation power level of 150 to 200 watts. ~ransducer 8 is caused to operate under these conditions as a result of its being coupled to generator 10. In turn, transducer 8 is attached to the base or a ~ide of tank 6 to vibrate liquid L under these conditions. Transducer 8, generator 10, and tank 6 are preferably together embodied in a conventional -~-I ultrasonic cleaning unit. one example of such a unit is the Branson D-150 Ultrasonic cleaner manufactured by Branson Equip~ent Co., Shelton, CT.
Planar optical device D is placed in container 2 I for fine polishing in accordance with the present I invention. A weighted cover 4 is then placed over ;:
,,-- 21.,i{31',~
container 2 to keep it in contact with the bottom of tank 6. Also held within container 2 is polishing mixture P
which is subjected to ultrasonic conditions as the high intensity positive displacements produced in liquid L are transmitted through the wall of container 2. In turn, such displacements of polishing mixture P impinge planar optical device D. During operation of the apparatus of FIG. 1, the level of liquid L should be maintained at a height sufficient to ensure transmission of such positive displacements. Generally, a depth of 2.0 to 2.6 centimeters, preferably 2.54 centimeters, of liquid in tank 6 is sufficient.
Instead of utilizing the arrangement of FIG. 1, ~5 the ultrasonic polishing process of the present invention can employ a workholder or clamp to immerse planar optical device D in polishing mixture P of container 2. This technique is disclosed in U.S. Patent Nos. 2,796,702 and 3,564,775 to Bodine, Jr. which are hereby incorporated by reference.
In another alternative embodiment of the present invention, the process can be carried out without utilizing ~ container 2 and cover 4. Polishing mixture P and planar 3 25 optical device D can be placed directly in tank 6 for fine polishing.
Polishing mixture P is prepared from a mixture of a liquid and abrasive particles. The polishing mixture has a volumetric ratio of liquid to abrasive particles of 1:0.4 to 1:2.5, preferably 1:1.
, :
Polishing can be carried out at any temperature which is not detrimental to tne optically transparent surface being polished. Temperatures of not more than 20 to 50-C should be used with room temperature being .
a l ~
preferred. If need be, ice can be added to liquid L to ensure that it is not overheated by transducer 8.
Generally, the longer polishing is carried out, the smoother the optically transparent surfaces become.
Polishing times of about 1 to 4 hours are usually satisfactory.
The abrasive particles preferably have a size of up to 1 micron, more preferably .l to .3 microns. These particles are made from aluminum oxide, glass, diamond dust, carborundum, tungsten carbide, silicon carbide, boron carbide, and mixtures thereof. Preferably, aluminum oxide powder with a .3 micron particle size is utilized.
The liquid component of polishing mixture P can be any liquid suitable for slurrying the above abrasive particles. Such liquids include tap water and deionized water.
The fine polishing method of the present invention is useful in treating optically transparent surfaces which define a cavity or sidewall in an optical waveguide. Such cavities or sidewalls are formed by subjecting optical waveguides to reactive ionic etching and have a configuration corresponding to that of a planar optical element. After the cavity or sidewall is formed, it is finely polished in accordance with the present invention. A planar optical element is then formed in the polished cavity in accordance with the procedure of U.S.
Patent Nos. 4,868,453 to Gidon, et al. and 4,740,951 to Lizet, et al. and M.M. Minot, "A New Guided-Wave Lens Structure, n Journal of Lightwave Technology, vol. 8, no. 12 (1990), all of which are discussed above. Suitable planar optical element configurations are those of a geodesic component, a Luneberg lens, a Fresnel lens, a grating lens, a TIPE lens, and other similar microcomponent devices.
- 2 ~
Several techniques are known for producing such planar optical elements in planar integrated optical devices. The following references disclose suitable procedures: U.S. Patent No. 4,712,856 to Nicia for geodesic components; Suhara, et al., "Graded-Index Fresnel ~ -~
Lenses for Integrated opticS," Ap~lied O~tics, vol. 21, no. ~-11, pp. 1966-71 (1982) for Fresnel lenses: Columbini, "Design of Thin-film Luneberg-type Lenses for Maximum Focal Length Control," A~Dlied optics, vol. 20, no. 20, pp. 3589-93 (1981) for Luneberg lenses; and Hatakoshi et al., "Waveguide Grating Lenses for Optical Couplers," A~plied Optics, vol. 23, no. 11, pp. 1749-53 (1984) for grating lenses. Another technique has been developed where planar optical waveguides and components therein are fabricated using polymers, e.g., Fan, et al., EPO Patent Publication No. 0,446,672.
Geodesic lenses are characterized by a surface indentation in the top of the planar optical waveguide.
Geodesic lenses require tight control during the manufacture of this surface indentation in order to keep scattering losæes at transition points to a minimum.
Luneberg lenses, which are a subclass of geodesic lenses, require the use of a lens material which has a higher index of refraction than the planar optical wave~uide substrate with which it is used.
Fresnel lenses, which are similar to zone plates in bulk optics, rely on phase shifting and/or absorption to obtain the desired focusing effect. This phase shifting is achieved through a series of half-period zones which are applied to a planar optical waveguide. For a more detailed 1 35 discussion of the use of Fresnel lenses in planar optical waveguides, see Ashley et al., "Fresnel Lens in a Thin-film ~ 2 i ~ 0 Waveguide", Applied Physics Lette~s, vol. 33, pages 490-92 ---(1978).
Other techniques for producing planar optical elements in optical waveguides are disclosed in U.S. Patent Application Serial No. 840,74g to Bhagavatula, which is hereby incorporated by reference.
Optically transparent surfaces treated in accordance with the present invention generally have a surface roughness which is substantially smoother than that encountered after reactive ionic etching. When surfaces of an optical waveguide cavity are finely polished in this fashion before formation of a planar optical element in the cavity, the waveguide has substantially less excess loss than waveguides which have not been polished in this fashion. Thus, optical waveguides treated in accordance with the present invention exhibit substantially better performance than those not subjected to polishing.
EXAMPLES
Exampl~ 1 An optical waveguide with a cavity formed by reactive ionic etching was subjected to a buffered oxide etch with a modified HF buffered solution for 30 seconds at an etch rate of 400 Angstroms per minute. After completion of the buffered oxide etch treatment, a photograph of the optical waveguide was taken with a scanning electron microscope. See Figure 2. This photograph shows that the cavity surfaces have significant roughness.
~xample 2 An optical waveguide with a cavity like that of Example 1 was subjected to a buffered oxide etch according to the procedures set forth in Example 1.
~7`~s ~
The waveguide was then placed in a 30 milliliter beaker to which has been added a polishing mixture -~
formulated from 10 milliliters of 0.3 micron alumina powder and 10 milliliters of water. The beaker was then placed in the tank of a Branson D-lso ultrasonic cleaner and a weighted plastic cover was put on top of the beaker to ensure that it remained in good contact with the base of the ultrasonic cleaner. The ultrasonic cleaner tank was then filled to a height of 2.54 centimeters of water so that ultrasonic vibrations were transmitted to the beaker contents. The ultrasonic cleaner was then turned on and operated for a period of 1 hour.
:
After completion of the ultrasonic treatment, the optical waveguide was removed and a photograph of it was taken with a scanning electron microscopeO This photograph is FIG. 3. A comparison of FIGS. 2 and 3 show that the fine polishing procedure of the present invention produces a substantially smoother cavity.
Exampl* 3 The test procedure of Example 2 was repeated except that the ultrasonic polishing stage was carried out for 2 hours. After completion of ultrasonic polishing, the optical waveguide was removed from the polishing mixture and a photograph of it was taken with a scanning electron microscope. This photograph is FIG. 4. A comparison of FIG. 4 with FIGS. 2 and 3 shows that increasing the ultrasonic polishing time enhances the smoothness of the cavity walls.
~xample 4 The process of Example 2 was repeated except that the ultrasonic polishing time was 4 hours. After completion of ultrasonic polishing, the optical waveguide was removed from the polishing mixture and a photograph of it was taken with a scanninq electron microscope. This ~ 2lii~la photograph is FIG. 5. A comparison of FIG. 5 with FIGS. 2, 3, and 4 indicates that the 4 hour polishing time achieved increased smoothness of the cavity walls.
Example 5 lx8 coupler/splitter devices were made according to the design and process set forth in copending U.S. . :
Patent Application Serial No. 07/840,749, which is incorporated herein by reference. One such device was measured after processing according to Example 1 for optical performance. The mean ratio between the input power and the output power for the 8 outputs was approximately 12 dB (theoretical ratio is 9 dB for lx8 splitting).
Another such device was additionally treated according to the polishing process of Example 4. The mean excess loss was about 11 dB, an improvement of 33% from the excess loss without the inventive polishing treatment.
Claims (10)
1. A method of finely polishing an optically transparent surface which defines a cavity or wall in an optical element contained in a small, planar optical device, said method comprising:
providing a polishing mixture in the form of a liquid slurry containing small abrasive particles and contacting the polishing mixture, while subjected to agitation, with an optically transparent surface which defines a cavity or wall in an optical waveguide contained in a small, planar optical device under conditions effective to polish finely the optically transparent surface.
providing a polishing mixture in the form of a liquid slurry containing small abrasive particles and contacting the polishing mixture, while subjected to agitation, with an optically transparent surface which defines a cavity or wall in an optical waveguide contained in a small, planar optical device under conditions effective to polish finely the optically transparent surface.
2. A method according to claim 1, wherein said contacting involves immersing the optically transparent surface in the polishing mixture.
3. A method according to claim 2, wherein the polishing mixture is in a container, wherein the container is maintained in a liquid bath which is subjected to ultrasonic agitation.
4. A method according to claim 1, wherein the agitation is carried out under ultrasonically at a frequency of 20 to 45 kilohertz, or a power level of 150 to 200 watts, or both.
5. A method according to claim 1, wherein the abrasive particles are made from aluminum oxide, glass, diamond dust, carborundum, tungsten carbide, silicon carbide, boron carbide, and mixtures thereof.
6. A method according to claim 1, wherein the polishing mixture has a volumetric ratio of liquid to abrasive particles of 1:0.4 to 1:2.5.
7. A method according to claim 1, wherein the optically transparent surface is configured to define a planar optical element, a geodesic component, a Luneberg lens, a Fresnel lens, a grating lens, a TIPE lens, or other similar microcomponent devices.
8. A method according to claim 9, wherein the optically transparent surface defines a cavity or sidewall in an optical waveguide.
9. A method according to claim 1, wherein the abrasive particles have a size of up to 1 micron, preferrably a size range of .1 to .3 microns.
10. A method of finely polishing an optically transparent surface which defines a cavity or wall in an optical waveguide contained in a small planar optical device, said method comprising:
providing a polishing mixture, while subjected to ultrasonic agitation, with an optically transparent surface which defines a cavity or wall in an optical waveguide contained in a small planar optical device under conditions effective to polish finely the optically transparent surface.
providing a polishing mixture, while subjected to ultrasonic agitation, with an optically transparent surface which defines a cavity or wall in an optical waveguide contained in a small planar optical device under conditions effective to polish finely the optically transparent surface.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US1134393A | 1993-01-29 | 1993-01-29 | |
| US08/011,343 | 1993-01-29 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2111010A1 true CA2111010A1 (en) | 1994-07-30 |
Family
ID=21749978
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2111010 Abandoned CA2111010A1 (en) | 1993-01-29 | 1993-12-09 | Method of finely polishing planar optical elements |
Country Status (5)
| Country | Link |
|---|---|
| EP (1) | EP0608730B1 (en) |
| JP (1) | JPH0752031A (en) |
| AU (1) | AU673389B2 (en) |
| CA (1) | CA2111010A1 (en) |
| DE (1) | DE69411403T2 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110948334A (en) * | 2019-12-18 | 2020-04-03 | 肖杰 | Surface grinding device is used in magnetic ring processing |
Families Citing this family (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0749805A1 (en) * | 1995-06-20 | 1996-12-27 | Valentinas Snitka | A diamond polishing method and apparatus |
| WO1997000756A2 (en) * | 1995-06-20 | 1997-01-09 | Valentinas Snitka | A diamond polishing method and apparatus |
| KR100567982B1 (en) * | 1997-12-08 | 2006-04-05 | 가부시키가이샤 에바라 세이사꾸쇼 | Polishing solution feeder |
| US5989301A (en) * | 1998-02-18 | 1999-11-23 | Saint-Gobain Industrial Ceramics, Inc. | Optical polishing formulation |
| WO2000027586A1 (en) * | 1998-11-06 | 2000-05-18 | Shaochien Tseng | Plastic polishing process under uniform pressure |
| CN102785145B (en) * | 2012-08-16 | 2015-07-29 | 中国科学院西安光学精密机械研究所 | Airbag type polishing device based on corrosion control |
| CN102794698B (en) * | 2012-08-16 | 2015-10-21 | 中国科学院西安光学精密机械研究所 | Polishing device for accelerating corrosion of radiation temperature field |
| SG10201702432YA (en) | 2013-03-14 | 2017-05-30 | Ekos Corp | Method and apparatus for drug delivery to a target site |
| US9793613B2 (en) | 2013-10-09 | 2017-10-17 | The Boeing Company | Additive manufacturing for radio frequency hardware |
| CN115042022B (en) * | 2022-07-05 | 2023-08-18 | 湖南锐健科技有限公司 | Manipulator vision lens grinding device based on ultrasonic cavitation liquid gallium infiltration supplement |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3061422A (en) * | 1960-11-25 | 1962-10-30 | Nippon Electric Co | Method of maching semiconductors |
| SE383784B (en) * | 1970-01-28 | 1976-03-29 | France Etat Armement | PROCEDURE FOR MANUFACTURING AN OPTICAL PART WITH SMALL IMPORTANCE OF A MONOLITICAL SUBJECT |
-
1993
- 1993-12-09 CA CA 2111010 patent/CA2111010A1/en not_active Abandoned
-
1994
- 1994-01-15 DE DE1994611403 patent/DE69411403T2/en not_active Expired - Fee Related
- 1994-01-15 EP EP19940100543 patent/EP0608730B1/en not_active Expired - Lifetime
- 1994-01-19 AU AU53848/94A patent/AU673389B2/en not_active Ceased
- 1994-01-31 JP JP2586494A patent/JPH0752031A/en active Pending
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110948334A (en) * | 2019-12-18 | 2020-04-03 | 肖杰 | Surface grinding device is used in magnetic ring processing |
Also Published As
| Publication number | Publication date |
|---|---|
| AU5384894A (en) | 1994-08-04 |
| AU673389B2 (en) | 1996-11-07 |
| EP0608730B1 (en) | 1998-07-08 |
| DE69411403D1 (en) | 1998-08-13 |
| JPH0752031A (en) | 1995-02-28 |
| EP0608730A1 (en) | 1994-08-03 |
| DE69411403T2 (en) | 1999-03-04 |
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