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Silicon micro optical switching device with an electromagnetically operated cantilever
Sensors and Actuators 83 Ž2000. 220–224 www.elsevier.nlrlocatersna
Silicon micro optical switching device with an electromagnetically operated cantilever Tsukasa Matsuura a,) , Tatsuya Fukami a , Martial Chabloz a , Yuichi Sakai a , Shin-ichi Izuo a , Aritomo Uemura b, Shin-ichi Kaneko b, Kazuhiko Tsutsumi a , Koichi Hamanaka c a
AdÕanced Technology R & D Center, Mitsubishi Electric Corporation, 8-1-1, Tsukaguchi-Honmachi, Amagasaki, Hyogo 661-8661, Japan b Information Technology R & D Center, Mitsubishi Electric Corporation, Kamakura, Kanagawa 347-8501, Japan c Chitose Institute of Science and Technology (CIST), Chitose, Hokkaido 066-8655, Japan Accepted 17 December 1999
Abstract We report on a new concept 2 = 2 fiber-optical switching device with an electromagnetically operated cantilever. The device is composed of a switching mirror module and a fiber array module. The switching mirror module consists of a fixed mirror, a moving mirror, a cantilever, support glasses and magnets. The mirrors and the cantilever are micromachined from one silicon wafer by deep silicon etching. As the cantilever has a magnetic film on its surface, it is driven by an electromagnet and latched by permanent magnets. The fiber array module consists of four optical fibers with graded index fibers, which are aligned parallel and fixed in a glass holder. The required current to operate the cantilever is 34 mA Ž0.3 V. and 20 ms for the pulse width, and the required magnetomotive force is 9.5 A P turns. The shortest switching time is 20 ms. The surface roughness of the mirrors are about 30 nm, the reflection loss of one mirror is y0.05 dB, crosstalk is smaller than y60 dB, and the insertion loss is y1.5 dB. Owing to the optical fibers preassembled as a module, the proposed device facilitates the optical path adjustment and the assembly. q 2000 Elsevier Science S.A. All rights reserved. Keywords: Optical switch; Electromagnetic actuator; Micromachining; Fiber-optic switch
1. Introduction Fiber-optic network system is becoming important due to its low loss, light weight and large data transmission capacity. To increase the reliability of the systems, rerouting of data traffic is conducted using optical switches in case of cable damage. Currently, there are waveguide type switches and free-space type switches, though, the mechanical free-space type is widely used as it has many advantages over the waveguide type, such as lower wavelength dependency, smaller crosstalk and lower insertion loss. Recently, optical switches using micromachining have been studied to keep these advantages and overcome drawbacks of conventional switches, including low speed, large size and high cost. For example, devices with optical fibers aligned at 908 of each other, as shown in Fig. 1Ža., have been demonstrated w1–3x. The package size of this type of devices is large, due to optical fibers that require a large
curvature to prevent high losses. Therefore, we have studied a new type in which four optical fibers are aligned parallel and mirrors are at the ends of optical fibers, as shown in Fig. 1Žb.. The proposed switch realizes high-density packaging and easy assembly. Design, fabrication process and characterization are reported in this paper. 2. Design and principle of actuation 2.1. Design The schematic diagram of the switching device is shown in Fig. 2. It consists of two modules: a fiber array module
) Corresponding author. Tel.: q81-6-6497-7509; fax: q81-6-64977295. E-mail address: [email protected] ŽT. Matsuura..
0924-4247r00r$ - see front matter q 2000 Elsevier Science S.A. All rights reserved. PII: S 0 9 2 4 - 4 2 4 7 Ž 9 9 . 0 0 3 8 7 - 8
Fig. 1. Two types of optical switch.
T. Matsuura et al.r Sensors and Actuators 83 (2000) 220–224
Fig. 2. Schematic view of the switching device.
and a switching mirror module. The fiber array module consists of four single-mode optical fibers with 125 mm in diameter for each one, and a fiber holder. A Graded Index fiber ŽGI fiber. is fixed to the end of each optical fiber by fusion splicing to collimate laser beam. To minimize the coupling loss, the optimized length of the GI fiber is about 1 mm. The optical fibers are aligned parallel and fixed in the V-grooves of the fiber holder. The switching mirror module consists of a fixed mirror, a moving mirror, a cantilever, support glasses and magnets. The support glasses and magnets and are not shown in Fig. 2. The dimensions of the cantilever are 180-mm wide, 50-mm thick and 10-mm long. The moving mirror is situated on the end of the cantilever. A 0.04-mm-thick Cr and a 0.36-mm-thick Au layers are deposited on the surfaces of the mirrors. The mirrors and the cantilever are micromachined from one 600-mm-thick silicon wafer using high aspect ratio silicon etch ŽHARSE. w4x process. The cantilever has a 5-mm-thick Fe–Ni magnetic film on its rear surface and is driven by an electromagnet and latched by permanent magnets.
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Fig. 4. Simulated result of the cantilever actuation. The number of coil turns is 280. I and Fm indicate the current and the magnetomotive force, respectively.
The cross-sectional view of the assembled optical switching device is shown in Fig. 3. An upper support glass, which supports an upper permanent magnet, is placed above the moving mirror and glued on the silicon body. This glass makes contact with the upper surface of the moving mirror and works as a stopper when the mirror is pulled up. The silicon body is fixed on a lower support glass, which has a 180-mm-deep groove, thus the cantilever can bend downward. The electromagnet and the lower permanent magnet are glued on the lower support glass. The electromagnet consists of an Fe core and a Cu coil of 80-mm in diameter and 280 turns. The magnetized directions of the upper and the lower magnets are opposite, as shown by the arrows in Fig. 3. The cantilever is driven downward or upward when the magnetic field is generated in the core gap. 2.2. Principle of actuation The starting point of the system is chosen to be when the cantilever is up and latched by the upper permanent
Fig. 3. Cross-sectional view of the optical switching device.
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T. Matsuura et al.r Sensors and Actuators 83 (2000) 220–224
Fig. 7. SEM micrograph of silicon mirror surfaces during step Ž3. of the fabrication process.
Fig. 5. Optical beam paths of Position 1 and 2.
magnet. In Fig. 3, the cantilever and the moving mirror are drawn by solid lines corresponding to Position 1. To move the cantilever downward, current is applied to the coil with the condition that the generated magnetic field at the
Fig. 6. Fabrication process of silicon mirrors and cantilever.
Fe–Ni magnetic film has the same direction as that of the lower permanent magnet. The cantilever moves as soon as the total magnetic force surpasses the upper permanent magnet force and restoration force of the cantilever. Once the cantilever is pulled down, it is latched by the force of the lower permanent magnet without current to the coil. In Fig. 3, the cantilever and the moving mirror are drawn by broken lines corresponding to Position 2. When a current of reverse polarity is applied, the generated magnetic field weakens the magnetic field of the lower permanent magnet and thus releases the cantilever. The cantilever moves upward by its restoration force and is again latched by the upper permanent magnet force corresponding to the starting state of the device. Fig. 4 shows a simulated result of the cantilever actuation. The x-axis is the position of the magnetic film. The cantilever is latched up at x s 0 mm, and latched down at x s y180 mm. The y-axis is the actuation force on the magnetic film from the magnets. The bold solid line shows the restoration force of the cantilever and the other lines
Fig. 8. SEM micrograph of silicon mirrors and cantilever after step Ž3. of the fabrication process.
T. Matsuura et al.r Sensors and Actuators 83 (2000) 220–224
Fig. 9. SEM micrograph of the fixed mirror. The surface of the effective mirror area is smooth.
show the magnetic forces. At x s y180 mm, the magnetic forces surpass the cantilever restoration force, even the applied current I s 0 mA. This means that the cantilever is latched. The result indicates that a current of "100 mA or a magnetomotive force of "28 A turns is enough to actuate the cantilever. Fig. 5Ž1. shows the optical paths of Position 1. The beam is reflected by the fixed mirror and the moving mirror. Therefore, Ch1–Ch2 and Ch3–Ch4 are connected. Fig. 5Ž2. shows the optical paths of Position 2. The beam is reflected only by the fixed mirror. Therefore, Ch1–Ch4 and Ch2–Ch3 are connected.
3. Fabrication process Fabrication process of the silicon mirrors and the cantilever is shown in Fig. 6. Ž1. A Fe–Ni soft magnetic film is plated on a 600-mmthick silicon wafer. The film thickness is about 5 mm and the area is about 0.5 mm2 .
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Ž2. A 60-mm-deep groove is made using the HARSE process. This groove is etched through in the next step. Ž3. The mirrors and 50-mm-thick cantilever are made also using the HARSE process. In this process, we applied a standard Bosch process and the etching power is mainly adjusted so that the effective mirror area, that is from the top to about 150 mm in depth, will be smooth and vertical. Fig. 7 shows a SEM micrograph of silicon mirror surfaces during the process. The cantilever is released in this step. Ž4. A 0.04-mm-thick Cr film and a 0.36-mm-thick Au film are deposited by vacuum evaporation. To cover the vertical mirror surfaces, the film is deposited at an angle of 458. Fig. 8 shows a SEM micrograph of the silicon mirrors and the cantilever after the step Ž3. of the fabrication process. Fig. 9 is a SEM micrograph of the fixed mirror. The surface roughness is measured by AFM ŽAtomic Force Microscope.. The roughness increases as etching depth increases, but that of the effective mirror part remains as small as 30 nm rms. After completing the silicon process, the support glasses and the magnets are attached to obtain the switching mirror module.
4. Characterization Firstly, the reflection loss is measured. The optical power from a stabilized light source is directly measured by an optical power meter, and this power is defined as 100%. Then, using a mirror sample, the power of reflected light by an etched sidewall is measured. The reflected power is 98.9% or the reflection loss is y0.05 dB. Then the insertion loss is measured. When the moving mirror is up ŽPosition 1., the insertion loss is y1.5 dB, and when the mirror is down ŽPosition 2., it is y3.4 dB. Because the process is still not stable and optimized enough, verticality of the fixed mirror and the moving mirror are slightly
Fig. 10. Output fluctuation by switching operation. The outputs, measured through Ch1 and Ch2, are normalized by the initial output value. One set of up-and-down switching operation is defined as one cycle.
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T. Matsuura et al.r Sensors and Actuators 83 (2000) 220–224
References w1x S.S. Lee, E. Motamedi, M.C. Wu, Surface-micromachined free-space fiber optic switches with integrated microactuators for optical fiber communication systems, Transducers ’97, Digest of Technical Papers 1 Ž1997. 85–88. w2x R.A. Miller, Y.C. Tai, G. Xu, J. Bartha, F. Lin, An electromagnetic MEMS 2=2 fiber optic bypass switch, Transducers ’97, Digest of Technical Papers 1 Ž1997. 89–92. w3x C. Marxer, N.F. de Rooij, Silicon micromechanics for the fiber-optic information highway, Sens. Mater. 10 Ž6. Ž1998. 351–362. w4x Licensed from Robert Bosch, patent number 5501893, issued March 26, 1996.
Fig. 11. Picture of package. The package dimensions are 10.4=23.5=7 mm and it has 14 pins. Japanese 100 yen coin is shown as a reference.
different. That is the reason the insertion losses of two states are not the same. Crosstalk is smaller than y60 dB in any position. During the optical measurement, the fiber modules are actively aligned, because the tolerance of angle misalignment is rather severe. For example, 0.58 misalignment leads to the loss of y2.5 dB. The switching operation is carried out by applying a pulsed current. The minimum required current is 34 mA Ž0.3 V. for 20 ms, and the magnetomotive force is 9.5 A P turns. The shortest switching time is 20 ms. The output fluctuation by switching operation was also measured. The stabilized light source was connected to Ch1 and the output optical power was measured through Ch2. The result is shown in Fig. 10, where the output is normalized by the initial output. During 50 switching cycles, the output fluctuation is within "0.4 dB. The assembled switching device is placed in a package shown in Fig. 11. Its dimensions are 10.4 = 23.5 = 7 mm and it has 14 pins. 5. Conclusions A new concept 2 = 2 fiber-optical switching device with an electromagnetically operated cantilever has been demonstrated. The smooth and vertical mirrors with high reflectivity and low loss are achieved by optimizing the conditions of deep silicon etching. The surface roughness of the mirror is about 30 nm, the reflection loss of one mirror is y0.05 dB, the smallest total insertion loss is y1.5 dB, and crosstalk is smaller than y60 dB. The switching operation is carried out by applying a pulsed current. The required current is 34 mA Ž0.3 V. for 20 ms, and the required magnetomotive force is 9.5 A P turns. The shortest switching time is 20 ms. The output fluctuation is within "0.4 dB during 50 switching cycles. Higher operational speed and smaller current can be achieved by increasing the number of coil turns of the electromagnet. The proposed switch can realize easy assembly and high-density packaging.
Biographies Tsukasa Matsuura received his BS Ž1982. and MS Ž1984. degrees in Mechanical Engineering from Waseda University, Tokyo, Japan, and joined Mitsubishi Electric in 1984. He has been doing research on silicon micromachined devices since 1993 including micro sensors and optical switches. Tatsuya Fukami received his BS Ž1983. and MS Ž1985. degrees in Science from Osaka University, Osaka, Japan, and joined Mitsubishi Electric in 1985. He has been doing research on magnetic thin film devices including micro sensors and magneto-optical disks. Martial Chabloz received his Diploma in Microengineering in 1996 from the Swiss Federal Institute of Technology Lausanne ŽEPFL.. In 1997, he joined the Institute of Microsystems at EPFL, Switzerland to develop elements of integrated optics within silicon substrates. Since April 1998, he has been working at Mitsubishi Electric, Japan on inertial microsensors and micro optical switches using micromachining technologies. Yuichi Sakai received his BS Ž1983., MS Ž1985. and PhD degrees in Physical Chemistry Ž1988. from Osaka University, Japan. He joined Mitsubishi Electric in 1988. He is currently researching silicon microsensors and micromachining technologies. Shin-ichi Izuo received his BS Ž1996. and MS Ž1998. degrees in Material Science and Engineering from Kyoto University, Kyoto Japan, and joined Mitsubishi Electric in 1998. He has been doing research on silicon micromachined devices. Aritomo Uemura received a BS degree in Electric Engineering from Kyoto University in 1989, Japan, and joined Mitsubishi Electric. He has been engaged in research and development of lightwave communication systems, including optical switching system. Shin-ichi Kaneko received a BS degree Ž1986. in Physics from Tokyo Institute of Technology, Tokyo, Japan, and he joined Mitsubishi Electric in 1986. He has been engaged in research and development on optical components for optical fiber communication systems. Kazuhiko Tsutsumi received his BS Ž1976. and MS Ž1978. degrees in Materials Engineering and his PhD degree in Electrical Engineering Ž1986. from Osaka University, Japan. Since 1982, he has worked as a research scientist at Mitsubishi Electric, Japan and he is now a group manager in the Advanced Technology R&D Center. Research interests in his group include device physics, microsensors, micromachining and process optimization related to sensors. Koichi Hamanaka received his BS Ž1965., MS Ž1967., and PhD Ž1996. degrees in Electronic Engineering from Keio University, Tokyo, Japan. He joined Mitsubishi Electric in 1967 and moved in to the Chitose Institute of Science and Technology in 1999. His recent research interest is the thin film technique for optoelectronics and cryoelectronics.
Silicon micro optical switching device with an electromagnetically operated cantilever Tsukasa Matsuura a,) , Tatsuya Fukami a , Martial Chabloz a , Yuichi Sakai a , Shin-ichi Izuo a , Aritomo Uemura b, Shin-ichi Kaneko b, Kazuhiko Tsutsumi a , Koichi Hamanaka c a
AdÕanced Technology R & D Center, Mitsubishi Electric Corporation, 8-1-1, Tsukaguchi-Honmachi, Amagasaki, Hyogo 661-8661, Japan b Information Technology R & D Center, Mitsubishi Electric Corporation, Kamakura, Kanagawa 347-8501, Japan c Chitose Institute of Science and Technology (CIST), Chitose, Hokkaido 066-8655, Japan Accepted 17 December 1999
Abstract We report on a new concept 2 = 2 fiber-optical switching device with an electromagnetically operated cantilever. The device is composed of a switching mirror module and a fiber array module. The switching mirror module consists of a fixed mirror, a moving mirror, a cantilever, support glasses and magnets. The mirrors and the cantilever are micromachined from one silicon wafer by deep silicon etching. As the cantilever has a magnetic film on its surface, it is driven by an electromagnet and latched by permanent magnets. The fiber array module consists of four optical fibers with graded index fibers, which are aligned parallel and fixed in a glass holder. The required current to operate the cantilever is 34 mA Ž0.3 V. and 20 ms for the pulse width, and the required magnetomotive force is 9.5 A P turns. The shortest switching time is 20 ms. The surface roughness of the mirrors are about 30 nm, the reflection loss of one mirror is y0.05 dB, crosstalk is smaller than y60 dB, and the insertion loss is y1.5 dB. Owing to the optical fibers preassembled as a module, the proposed device facilitates the optical path adjustment and the assembly. q 2000 Elsevier Science S.A. All rights reserved. Keywords: Optical switch; Electromagnetic actuator; Micromachining; Fiber-optic switch
1. Introduction Fiber-optic network system is becoming important due to its low loss, light weight and large data transmission capacity. To increase the reliability of the systems, rerouting of data traffic is conducted using optical switches in case of cable damage. Currently, there are waveguide type switches and free-space type switches, though, the mechanical free-space type is widely used as it has many advantages over the waveguide type, such as lower wavelength dependency, smaller crosstalk and lower insertion loss. Recently, optical switches using micromachining have been studied to keep these advantages and overcome drawbacks of conventional switches, including low speed, large size and high cost. For example, devices with optical fibers aligned at 908 of each other, as shown in Fig. 1Ža., have been demonstrated w1–3x. The package size of this type of devices is large, due to optical fibers that require a large
curvature to prevent high losses. Therefore, we have studied a new type in which four optical fibers are aligned parallel and mirrors are at the ends of optical fibers, as shown in Fig. 1Žb.. The proposed switch realizes high-density packaging and easy assembly. Design, fabrication process and characterization are reported in this paper. 2. Design and principle of actuation 2.1. Design The schematic diagram of the switching device is shown in Fig. 2. It consists of two modules: a fiber array module
) Corresponding author. Tel.: q81-6-6497-7509; fax: q81-6-64977295. E-mail address: [email protected] ŽT. Matsuura..
0924-4247r00r$ - see front matter q 2000 Elsevier Science S.A. All rights reserved. PII: S 0 9 2 4 - 4 2 4 7 Ž 9 9 . 0 0 3 8 7 - 8
Fig. 1. Two types of optical switch.
T. Matsuura et al.r Sensors and Actuators 83 (2000) 220–224
Fig. 2. Schematic view of the switching device.
and a switching mirror module. The fiber array module consists of four single-mode optical fibers with 125 mm in diameter for each one, and a fiber holder. A Graded Index fiber ŽGI fiber. is fixed to the end of each optical fiber by fusion splicing to collimate laser beam. To minimize the coupling loss, the optimized length of the GI fiber is about 1 mm. The optical fibers are aligned parallel and fixed in the V-grooves of the fiber holder. The switching mirror module consists of a fixed mirror, a moving mirror, a cantilever, support glasses and magnets. The support glasses and magnets and are not shown in Fig. 2. The dimensions of the cantilever are 180-mm wide, 50-mm thick and 10-mm long. The moving mirror is situated on the end of the cantilever. A 0.04-mm-thick Cr and a 0.36-mm-thick Au layers are deposited on the surfaces of the mirrors. The mirrors and the cantilever are micromachined from one 600-mm-thick silicon wafer using high aspect ratio silicon etch ŽHARSE. w4x process. The cantilever has a 5-mm-thick Fe–Ni magnetic film on its rear surface and is driven by an electromagnet and latched by permanent magnets.
221
Fig. 4. Simulated result of the cantilever actuation. The number of coil turns is 280. I and Fm indicate the current and the magnetomotive force, respectively.
The cross-sectional view of the assembled optical switching device is shown in Fig. 3. An upper support glass, which supports an upper permanent magnet, is placed above the moving mirror and glued on the silicon body. This glass makes contact with the upper surface of the moving mirror and works as a stopper when the mirror is pulled up. The silicon body is fixed on a lower support glass, which has a 180-mm-deep groove, thus the cantilever can bend downward. The electromagnet and the lower permanent magnet are glued on the lower support glass. The electromagnet consists of an Fe core and a Cu coil of 80-mm in diameter and 280 turns. The magnetized directions of the upper and the lower magnets are opposite, as shown by the arrows in Fig. 3. The cantilever is driven downward or upward when the magnetic field is generated in the core gap. 2.2. Principle of actuation The starting point of the system is chosen to be when the cantilever is up and latched by the upper permanent
Fig. 3. Cross-sectional view of the optical switching device.
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T. Matsuura et al.r Sensors and Actuators 83 (2000) 220–224
Fig. 7. SEM micrograph of silicon mirror surfaces during step Ž3. of the fabrication process.
Fig. 5. Optical beam paths of Position 1 and 2.
magnet. In Fig. 3, the cantilever and the moving mirror are drawn by solid lines corresponding to Position 1. To move the cantilever downward, current is applied to the coil with the condition that the generated magnetic field at the
Fig. 6. Fabrication process of silicon mirrors and cantilever.
Fe–Ni magnetic film has the same direction as that of the lower permanent magnet. The cantilever moves as soon as the total magnetic force surpasses the upper permanent magnet force and restoration force of the cantilever. Once the cantilever is pulled down, it is latched by the force of the lower permanent magnet without current to the coil. In Fig. 3, the cantilever and the moving mirror are drawn by broken lines corresponding to Position 2. When a current of reverse polarity is applied, the generated magnetic field weakens the magnetic field of the lower permanent magnet and thus releases the cantilever. The cantilever moves upward by its restoration force and is again latched by the upper permanent magnet force corresponding to the starting state of the device. Fig. 4 shows a simulated result of the cantilever actuation. The x-axis is the position of the magnetic film. The cantilever is latched up at x s 0 mm, and latched down at x s y180 mm. The y-axis is the actuation force on the magnetic film from the magnets. The bold solid line shows the restoration force of the cantilever and the other lines
Fig. 8. SEM micrograph of silicon mirrors and cantilever after step Ž3. of the fabrication process.
T. Matsuura et al.r Sensors and Actuators 83 (2000) 220–224
Fig. 9. SEM micrograph of the fixed mirror. The surface of the effective mirror area is smooth.
show the magnetic forces. At x s y180 mm, the magnetic forces surpass the cantilever restoration force, even the applied current I s 0 mA. This means that the cantilever is latched. The result indicates that a current of "100 mA or a magnetomotive force of "28 A turns is enough to actuate the cantilever. Fig. 5Ž1. shows the optical paths of Position 1. The beam is reflected by the fixed mirror and the moving mirror. Therefore, Ch1–Ch2 and Ch3–Ch4 are connected. Fig. 5Ž2. shows the optical paths of Position 2. The beam is reflected only by the fixed mirror. Therefore, Ch1–Ch4 and Ch2–Ch3 are connected.
3. Fabrication process Fabrication process of the silicon mirrors and the cantilever is shown in Fig. 6. Ž1. A Fe–Ni soft magnetic film is plated on a 600-mmthick silicon wafer. The film thickness is about 5 mm and the area is about 0.5 mm2 .
223
Ž2. A 60-mm-deep groove is made using the HARSE process. This groove is etched through in the next step. Ž3. The mirrors and 50-mm-thick cantilever are made also using the HARSE process. In this process, we applied a standard Bosch process and the etching power is mainly adjusted so that the effective mirror area, that is from the top to about 150 mm in depth, will be smooth and vertical. Fig. 7 shows a SEM micrograph of silicon mirror surfaces during the process. The cantilever is released in this step. Ž4. A 0.04-mm-thick Cr film and a 0.36-mm-thick Au film are deposited by vacuum evaporation. To cover the vertical mirror surfaces, the film is deposited at an angle of 458. Fig. 8 shows a SEM micrograph of the silicon mirrors and the cantilever after the step Ž3. of the fabrication process. Fig. 9 is a SEM micrograph of the fixed mirror. The surface roughness is measured by AFM ŽAtomic Force Microscope.. The roughness increases as etching depth increases, but that of the effective mirror part remains as small as 30 nm rms. After completing the silicon process, the support glasses and the magnets are attached to obtain the switching mirror module.
4. Characterization Firstly, the reflection loss is measured. The optical power from a stabilized light source is directly measured by an optical power meter, and this power is defined as 100%. Then, using a mirror sample, the power of reflected light by an etched sidewall is measured. The reflected power is 98.9% or the reflection loss is y0.05 dB. Then the insertion loss is measured. When the moving mirror is up ŽPosition 1., the insertion loss is y1.5 dB, and when the mirror is down ŽPosition 2., it is y3.4 dB. Because the process is still not stable and optimized enough, verticality of the fixed mirror and the moving mirror are slightly
Fig. 10. Output fluctuation by switching operation. The outputs, measured through Ch1 and Ch2, are normalized by the initial output value. One set of up-and-down switching operation is defined as one cycle.
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T. Matsuura et al.r Sensors and Actuators 83 (2000) 220–224
References w1x S.S. Lee, E. Motamedi, M.C. Wu, Surface-micromachined free-space fiber optic switches with integrated microactuators for optical fiber communication systems, Transducers ’97, Digest of Technical Papers 1 Ž1997. 85–88. w2x R.A. Miller, Y.C. Tai, G. Xu, J. Bartha, F. Lin, An electromagnetic MEMS 2=2 fiber optic bypass switch, Transducers ’97, Digest of Technical Papers 1 Ž1997. 89–92. w3x C. Marxer, N.F. de Rooij, Silicon micromechanics for the fiber-optic information highway, Sens. Mater. 10 Ž6. Ž1998. 351–362. w4x Licensed from Robert Bosch, patent number 5501893, issued March 26, 1996.
Fig. 11. Picture of package. The package dimensions are 10.4=23.5=7 mm and it has 14 pins. Japanese 100 yen coin is shown as a reference.
different. That is the reason the insertion losses of two states are not the same. Crosstalk is smaller than y60 dB in any position. During the optical measurement, the fiber modules are actively aligned, because the tolerance of angle misalignment is rather severe. For example, 0.58 misalignment leads to the loss of y2.5 dB. The switching operation is carried out by applying a pulsed current. The minimum required current is 34 mA Ž0.3 V. for 20 ms, and the magnetomotive force is 9.5 A P turns. The shortest switching time is 20 ms. The output fluctuation by switching operation was also measured. The stabilized light source was connected to Ch1 and the output optical power was measured through Ch2. The result is shown in Fig. 10, where the output is normalized by the initial output. During 50 switching cycles, the output fluctuation is within "0.4 dB. The assembled switching device is placed in a package shown in Fig. 11. Its dimensions are 10.4 = 23.5 = 7 mm and it has 14 pins. 5. Conclusions A new concept 2 = 2 fiber-optical switching device with an electromagnetically operated cantilever has been demonstrated. The smooth and vertical mirrors with high reflectivity and low loss are achieved by optimizing the conditions of deep silicon etching. The surface roughness of the mirror is about 30 nm, the reflection loss of one mirror is y0.05 dB, the smallest total insertion loss is y1.5 dB, and crosstalk is smaller than y60 dB. The switching operation is carried out by applying a pulsed current. The required current is 34 mA Ž0.3 V. for 20 ms, and the required magnetomotive force is 9.5 A P turns. The shortest switching time is 20 ms. The output fluctuation is within "0.4 dB during 50 switching cycles. Higher operational speed and smaller current can be achieved by increasing the number of coil turns of the electromagnet. The proposed switch can realize easy assembly and high-density packaging.
Biographies Tsukasa Matsuura received his BS Ž1982. and MS Ž1984. degrees in Mechanical Engineering from Waseda University, Tokyo, Japan, and joined Mitsubishi Electric in 1984. He has been doing research on silicon micromachined devices since 1993 including micro sensors and optical switches. Tatsuya Fukami received his BS Ž1983. and MS Ž1985. degrees in Science from Osaka University, Osaka, Japan, and joined Mitsubishi Electric in 1985. He has been doing research on magnetic thin film devices including micro sensors and magneto-optical disks. Martial Chabloz received his Diploma in Microengineering in 1996 from the Swiss Federal Institute of Technology Lausanne ŽEPFL.. In 1997, he joined the Institute of Microsystems at EPFL, Switzerland to develop elements of integrated optics within silicon substrates. Since April 1998, he has been working at Mitsubishi Electric, Japan on inertial microsensors and micro optical switches using micromachining technologies. Yuichi Sakai received his BS Ž1983., MS Ž1985. and PhD degrees in Physical Chemistry Ž1988. from Osaka University, Japan. He joined Mitsubishi Electric in 1988. He is currently researching silicon microsensors and micromachining technologies. Shin-ichi Izuo received his BS Ž1996. and MS Ž1998. degrees in Material Science and Engineering from Kyoto University, Kyoto Japan, and joined Mitsubishi Electric in 1998. He has been doing research on silicon micromachined devices. Aritomo Uemura received a BS degree in Electric Engineering from Kyoto University in 1989, Japan, and joined Mitsubishi Electric. He has been engaged in research and development of lightwave communication systems, including optical switching system. Shin-ichi Kaneko received a BS degree Ž1986. in Physics from Tokyo Institute of Technology, Tokyo, Japan, and he joined Mitsubishi Electric in 1986. He has been engaged in research and development on optical components for optical fiber communication systems. Kazuhiko Tsutsumi received his BS Ž1976. and MS Ž1978. degrees in Materials Engineering and his PhD degree in Electrical Engineering Ž1986. from Osaka University, Japan. Since 1982, he has worked as a research scientist at Mitsubishi Electric, Japan and he is now a group manager in the Advanced Technology R&D Center. Research interests in his group include device physics, microsensors, micromachining and process optimization related to sensors. Koichi Hamanaka received his BS Ž1965., MS Ž1967., and PhD Ž1996. degrees in Electronic Engineering from Keio University, Tokyo, Japan. He joined Mitsubishi Electric in 1967 and moved in to the Chitose Institute of Science and Technology in 1999. His recent research interest is the thin film technique for optoelectronics and cryoelectronics.