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Coupling tolerances of high-index silicon-oxynitride waveguides with small bending radii
Int. J. Electron. Commun. (AEÜ) 61 (2007) 168 – 171 www.elsevier.de/aeue
Coupling tolerances of high-index silicon-oxynitride waveguides with small bending radii Maxim Fadel∗ , Roland B. Gentemann University of Dortmund, High Frequency Institute, Friedrich-Woehler-Weg 4, D-44221 Dortmund, Germany Received 13 September 2006; received in revised form 2 November 2006 Dedicated to Professor Edgar Voges on the occasion of his 65th birthday
Abstract Silicon-oxynitride waveguides gained by plasma-enhanced chemical vapour deposition are very attractive for the fabrication of passive optical components used in optical networks. The low-loss and compact devices with small bending radii are achieved with a new high-index waveguide design. At the same time this feature increases the requirements on the fibreto-chip coupling compared to common fibre-matched waveguides. In this paper, we discuss the junction of the high-index optical components to fibre systems and their coupling tolerances. The presented solution is based on using high numerical aperture fibres. Furthermore, the option of higher automation and reliability is given by the coupling with tapered fibres because they allow better positioning tolerances. 䉷 2007 Elsevier GmbH. All rights reserved. Keywords: Optical waveguide; Silicon-oxynitride; Small bending radii; Fibre-to-chip coupling
1. Introduction The waveguide design made by silicon oxide on silicon is commonly mode-matched to telecom fibre systems. It could have large core dimension with a low refractive index contrast [1] like in Fig. 1a or a high index waveguide with a small core [2] like in Fig. 1b. However, it is not possible to fabricate small optical circuits by minimizing the optical paths with this kind of waveguide because of high losses due to small bending radii. The new waveguide design in Fig. 1c combines a thick core layer with high index contrast [3,4]. This gives the feature of high mode guidance, and the bending losses can be minimized. At the same time the coupling efficiency to standard telecom fibre will decrease.
∗ Corresponding author.
E-mail address: [email protected] (M. Fadel). 1434-8411/$ - see front matter 䉷 2007 Elsevier GmbH. All rights reserved. doi:10.1016/j.aeue.2006.12.007
In this paper, we introduce possibilities in order to improve the optical interconnection of high guidance waveguides to standard telecom fibres.
2. Waveguide technology A system plasma-enhanced chemical vapour deposition (PECVD) with the process gases SiH4 , N2 O and NH3 is used for the deposition of the silicon oxide and oxynitride layers on 4 inch silicon {1 0 0}-wafers. The deposition parameter settings were optimized to get homogenous and low-loss optical layers to suit the high requirements for optical applications. The hydrogen content in the layer that will cause optical losses has been reduced. Nevertheless, a high-temperature annealing treatment is still necessary to break the hydrogen bonds and to achieve low-loss devices. At the same time, the stress caused by the different thermal
M. Fadel, Roland B. Gentemann / Int. J. Electron. Commun. (AEÜ) 61 (2007) 168 – 171
169
Fig. 1. Fibre-matched waveguides are fabricated as a channel core with low-n (a) or as a ridge core with high-n (b). With the design in (c) much smaller bending radii are possible.
and used as a mask for a dry reactive ion etching step with CHF3 . Finally, the SiO2 cover layer is deposited [see Fig. 2(a)]. The facets of the waveguides are prepared with a special polishing saw disc with a grit size of about 3 m so they can directly be butt coupled. The residual roughness of the waveguide facets is lower than 3 m and has no effect when using an index-matched fluid or adhesive during the butt coupling. The transmitted power by a butt coupling scan with a high numerical aperture (UHNA) fibre is presented in Fig. 2(b). The coupling efficiency and the mode field diameter (MFD) of the waveguide will be discussed next.
3. Mode field and coupling efficiency
Fig. 2. The principal waveguide design is shown in (a). A lateral offset scan of the transmitted power is shown in (b). Here we butt couple the waveguide to a special high numerical aperture fibre.
expansion coefficients between the material systems SiO2 /Si could lead to layer cracking at high temperature. To avoid that, the stress and the hydrogen content of the deposited layer should be controlled within the given parameter area. With new parameter settings, robust and low-loss optical layers were deposited. After the annealing treatment at about 1150 ◦ C they show losses between 0.2 and 0.05 dB/cm within the C-band (1530–1565 nm). Besides a very reproducible and homogeneous layer thickness and refractive index were achieved. The refractive index contrast of the core to the undoped cover layer can be tuned from 0 to 0.08. Based on these oxide layers, waveguides are fabricated on 4 inch silicon wafers with 10 m thermal oxide. The core layer of 2 m is deposited and annealed. A negative resist is structured by UV photolithography
Compared to common fibre-matched waveguides the high guidance waveguides increase the optical coupling losses to fibre systems because their mode shape is much smaller than that of the standard single-mode fibre (SSMF). Thus, a mode size adaptation is required. This problem is already known from the packaging of laser diodes, because of their small spot size. The most widely used solution is based on lensed fibre systems. But here the spot focusing on the waveguide facet needs an alignment in the optical z-axes, which will be very difficult in case of multichannel interconnection. So we preferred first to use Ultra-High-NA-fibre (or UHNAfibre) [5] with a small MFD. This will increase the coupling efficiency to the waveguide. On the other side, this UHNAfibre has the feature of low-loss splicing to the SSMF. By using special splice parameters, causing thermal diffusion of the core doping material during splicing, the small MFD is extended to fit that of the SSMF. The losses are optimized below 0.2 dB per splice. It is important to study the coupling efficiency and tolerances between the waveguide and the UHNA-fibre because they are crucial for the characterisation and packaging of optical circuits. An analysis will follow now. We set the assumption that the modes of lightguiding structure are regarded as transversal electromagnetic waves (TEM), and they can be approximated by a Gaussian beam. The spot size w is defined as the distance from the mode summit at which the field amplitude is 1/e = 0.37 and the intensity 1/e2 = 0.135. The MFD is twice the spot size w. Streckert [6] introduced a practical definition for the spot size that could be easily measured
170
M. Fadel, Roland B. Gentemann / Int. J. Electron. Commun. (AEÜ) 61 (2007) 168 – 171
Fig. 4. The longitudinal shift measurement and calculation of SSMF, UHNA and a waveguide are presented. Table 1. Losses caused by misalignments between waveguide and UHNA-fibre
Fig. 3. A lateral offset measurement by butt coupling of a UHNA-fibre to another one (—) and to a waveguide (− · −) is shown.
with a transverse offset scan of two identical fibres. So ws is now defined as the distance from the best coupling position at which the normalized transmitted power is 1/e = 0.37. Fig. 3 shows such a butt coupling scan measurement of a UHNA-fibre to another one and to a waveguide. The good agreement of the transmitted power shape depending on the lateral misalignment presumes an excellent mode match between the UHNA-fibre and the waveguide. The coupling efficiency factor k is given for a lateral misalignment as [7] k =
21 2 21 + 22
2
2x 2 exp − 2 1 + 22
,
(1)
where 1,2 are the spot sizes of the coupling partner, and x is the lateral distance of their axes. The first part describes the misalignment caused by different spot sizes (x = 0). In the case of coupling the UHNA to the SSMF the losses will be −3.5 dB/facet, which also have been measured. Furthermore, it is possible to estimate the spot size of a waveguide from a coupling scan measurement with a nearly identical fibre and well-known spot size. So from Eq. (1) we obtain 2 − 2 . 2 = 2x1/e (2) 1 This definition works also for elliptical modes. From Fig. 3 (top) we read x1/e = 1.88 m and y1/e = 1.7 m. This results for the fabricated waveguides in wg,x = 1.9 m and wg,y = 1.5 m. In case of elliptical modes we are able to calculate the coupling losses between the UHNA and the
Lateral distance x (m) Measurement (dB) ±0.2 dB Calculation (dB) (w1 = w2 = 1.9 m); Eq. (1) Longitudinal distance (m) Measurement (dB) ±0.2 dB (normalized) Calculation (dB); Eq. (4) (normalized)
0.6 −0.5 −0.43
1 −1.5 −1.2
1.5 −3 −2.7
1 −0.4
3 −0.9
8 −2.9
−0.3
−0.8
−2.3
waveguides by using the equation [7]: 4 ((1,x /2 ) + (2 /1,x )) · ((1,y /2 ) + (2 /1,y )) ≈ 0.03 (≈ −0.12 dB). (3)
k =
The total attenuation caused by the optical interconnection waveguide/UHNA and UHNA/SSMF is about 0.35 dB. This is an excellent coupling efficiency of an optical device to the standard telecom fibre. But unfortunately small modes require a high-precision positioning and tighter tolerances than modes of large diameter. Especially the longitudinal offset, the distance between fibre and waveguide, is crucial. Fig. 4 shows the attenuation above the distance z of the fibre and/or waveguide facets as well as a calculation and measurement. It is clear, that the alignment precision relaxes for larger modes (see in Fig. 4 – SSMF vs. SSMF). The equation describing the pure longitudinal losses is written as follows [7]: k =
4(2 /1 )1/2 (z/na 21 )2 + ((2 /1 )2 + 1)2
.
(4)
is the used wavelength and na is the refractive index of the media between the fibres. In Table 1, the alignment tolerances by coupling the waveguides with an UHNA-fibre
M. Fadel, Roland B. Gentemann / Int. J. Electron. Commun. (AEÜ) 61 (2007) 168 – 171
171
presented. Especially the dependence on the longitudinal fibre chip distance increases the demands on the assembly techniques in comparison to SSMF. For measurement purposes tapered fibres were successfully employed for low loss fibre chip coupling. Fibres with a tapered diameter have a focus-point. In our case the focus length is relatively large so that misalignments in z-direction have a smaller effect on the coupling losses. Additionally, the fibres can be aligned by a maximum search algorithm. This speeds up the loss measurement process of optical waveguides.
References
Fig. 5. A longitudinal offset measurement of tapered fibre with different radii. The best coupling efficiency is achieved for a taper radius of about 10 m.
are listed. Because of the extreme high numerical aperture the impact of the angular misalignment stays in this case negligible. The single channel coupling with the purpose of measuring the waveguide chip shows fluctuating coupling losses due to the non-reproducible longitudinal offset between fibre and waveguide facets. For the z-axis the alignment is conducted manually, because an automated positioning procedure like that for the lateral axes is not possible. To reduce the positioning time by automating the alignment of the zaxes we use tapered fibres [8] instead of the UHNA. They show an optimum coupling by approaching to the waveguide where the best spot-size matching occurs. In Fig. 5 the tapered fibre is presented at the top, and the longitudinal offset measurement of different taper radii can be seen at the bottom. The tapered fibre with the lens radius of 10 m shows the best spot size fitting to the waveguide.
4. Conclusion In this paper, coupling tolerances between high-index silicon-oxynitride waveguides and ultra high NA fibres were
[1] Yasu M, Kawachi M. Fabrication of SiO2 /TiO2 glass planar optical waveguides by soot deposition. Trans Inst Electron Commun Eng Japan 1985;J68-C:454–61. [2] Hoffmann M, Kopka P, Voges E. Low-loss fiber-matched lowtemperature PECVD waveguides with small core dimensions for optical communication systems. IEEE Photon Technol Lett 1997;9(9):1238–40. [3] Bona G. Integrated optical planar waveguide components. Microsystem Technol 2003;9(5):291–4. [4] Fadel M, Voges E. Fibre-coupled high-index PECVD siliconoxynitride waveguides on silicon. In: 207th meeting of the electochem society, vol. 9(5). Quebec, Canada; 2005. [5] Nufern: Ultra high NA fibres, 13.09.2006 www.nufern.com. [6] Streckert J. A new fundamental mode field-radius definition usable for non-Gaussian and noncircular field distributions. J Lightwave Technol 1985;LT-3(2). [7] Neumann E-G. Single-mode fibres. Berlin, Heidelberg, New York: Springer; 1988. [8] Windel Th, Fischer UHP. Integrated optical mode field adapters at the end of single/multimode fibers. Opt Photon 2005;5874.
Maxim Fadel received his Dipl.-Ing. in 2001 from the Universität Dortmund, Germany. Since then he is a Ph.D. student at the High-Frequency Institute of the University Dortmund. Currently he is working in the field of SiON/SiO2 waveguides on silicon. Research interests are optical waveguide fabrication and measurement.
Roland B. Gentemann received his masters degree in 2002 from the University of Leeds, England and 2003 the Dipl.-Ing. from the University Dortmund, Germany. Since then he is a Ph.D. student at the High-Frequency Institute of the Universität Dortmund. Currently he is working in the field of assembly technologies for fibre-optical components. Research interests are silicon micromachining, optical fibre assembly automation and vision systems.
Coupling tolerances of high-index silicon-oxynitride waveguides with small bending radii Maxim Fadel∗ , Roland B. Gentemann University of Dortmund, High Frequency Institute, Friedrich-Woehler-Weg 4, D-44221 Dortmund, Germany Received 13 September 2006; received in revised form 2 November 2006 Dedicated to Professor Edgar Voges on the occasion of his 65th birthday
Abstract Silicon-oxynitride waveguides gained by plasma-enhanced chemical vapour deposition are very attractive for the fabrication of passive optical components used in optical networks. The low-loss and compact devices with small bending radii are achieved with a new high-index waveguide design. At the same time this feature increases the requirements on the fibreto-chip coupling compared to common fibre-matched waveguides. In this paper, we discuss the junction of the high-index optical components to fibre systems and their coupling tolerances. The presented solution is based on using high numerical aperture fibres. Furthermore, the option of higher automation and reliability is given by the coupling with tapered fibres because they allow better positioning tolerances. 䉷 2007 Elsevier GmbH. All rights reserved. Keywords: Optical waveguide; Silicon-oxynitride; Small bending radii; Fibre-to-chip coupling
1. Introduction The waveguide design made by silicon oxide on silicon is commonly mode-matched to telecom fibre systems. It could have large core dimension with a low refractive index contrast [1] like in Fig. 1a or a high index waveguide with a small core [2] like in Fig. 1b. However, it is not possible to fabricate small optical circuits by minimizing the optical paths with this kind of waveguide because of high losses due to small bending radii. The new waveguide design in Fig. 1c combines a thick core layer with high index contrast [3,4]. This gives the feature of high mode guidance, and the bending losses can be minimized. At the same time the coupling efficiency to standard telecom fibre will decrease.
∗ Corresponding author.
E-mail address: [email protected] (M. Fadel). 1434-8411/$ - see front matter 䉷 2007 Elsevier GmbH. All rights reserved. doi:10.1016/j.aeue.2006.12.007
In this paper, we introduce possibilities in order to improve the optical interconnection of high guidance waveguides to standard telecom fibres.
2. Waveguide technology A system plasma-enhanced chemical vapour deposition (PECVD) with the process gases SiH4 , N2 O and NH3 is used for the deposition of the silicon oxide and oxynitride layers on 4 inch silicon {1 0 0}-wafers. The deposition parameter settings were optimized to get homogenous and low-loss optical layers to suit the high requirements for optical applications. The hydrogen content in the layer that will cause optical losses has been reduced. Nevertheless, a high-temperature annealing treatment is still necessary to break the hydrogen bonds and to achieve low-loss devices. At the same time, the stress caused by the different thermal
M. Fadel, Roland B. Gentemann / Int. J. Electron. Commun. (AEÜ) 61 (2007) 168 – 171
169
Fig. 1. Fibre-matched waveguides are fabricated as a channel core with low-n (a) or as a ridge core with high-n (b). With the design in (c) much smaller bending radii are possible.
and used as a mask for a dry reactive ion etching step with CHF3 . Finally, the SiO2 cover layer is deposited [see Fig. 2(a)]. The facets of the waveguides are prepared with a special polishing saw disc with a grit size of about 3 m so they can directly be butt coupled. The residual roughness of the waveguide facets is lower than 3 m and has no effect when using an index-matched fluid or adhesive during the butt coupling. The transmitted power by a butt coupling scan with a high numerical aperture (UHNA) fibre is presented in Fig. 2(b). The coupling efficiency and the mode field diameter (MFD) of the waveguide will be discussed next.
3. Mode field and coupling efficiency
Fig. 2. The principal waveguide design is shown in (a). A lateral offset scan of the transmitted power is shown in (b). Here we butt couple the waveguide to a special high numerical aperture fibre.
expansion coefficients between the material systems SiO2 /Si could lead to layer cracking at high temperature. To avoid that, the stress and the hydrogen content of the deposited layer should be controlled within the given parameter area. With new parameter settings, robust and low-loss optical layers were deposited. After the annealing treatment at about 1150 ◦ C they show losses between 0.2 and 0.05 dB/cm within the C-band (1530–1565 nm). Besides a very reproducible and homogeneous layer thickness and refractive index were achieved. The refractive index contrast of the core to the undoped cover layer can be tuned from 0 to 0.08. Based on these oxide layers, waveguides are fabricated on 4 inch silicon wafers with 10 m thermal oxide. The core layer of 2 m is deposited and annealed. A negative resist is structured by UV photolithography
Compared to common fibre-matched waveguides the high guidance waveguides increase the optical coupling losses to fibre systems because their mode shape is much smaller than that of the standard single-mode fibre (SSMF). Thus, a mode size adaptation is required. This problem is already known from the packaging of laser diodes, because of their small spot size. The most widely used solution is based on lensed fibre systems. But here the spot focusing on the waveguide facet needs an alignment in the optical z-axes, which will be very difficult in case of multichannel interconnection. So we preferred first to use Ultra-High-NA-fibre (or UHNAfibre) [5] with a small MFD. This will increase the coupling efficiency to the waveguide. On the other side, this UHNAfibre has the feature of low-loss splicing to the SSMF. By using special splice parameters, causing thermal diffusion of the core doping material during splicing, the small MFD is extended to fit that of the SSMF. The losses are optimized below 0.2 dB per splice. It is important to study the coupling efficiency and tolerances between the waveguide and the UHNA-fibre because they are crucial for the characterisation and packaging of optical circuits. An analysis will follow now. We set the assumption that the modes of lightguiding structure are regarded as transversal electromagnetic waves (TEM), and they can be approximated by a Gaussian beam. The spot size w is defined as the distance from the mode summit at which the field amplitude is 1/e = 0.37 and the intensity 1/e2 = 0.135. The MFD is twice the spot size w. Streckert [6] introduced a practical definition for the spot size that could be easily measured
170
M. Fadel, Roland B. Gentemann / Int. J. Electron. Commun. (AEÜ) 61 (2007) 168 – 171
Fig. 4. The longitudinal shift measurement and calculation of SSMF, UHNA and a waveguide are presented. Table 1. Losses caused by misalignments between waveguide and UHNA-fibre
Fig. 3. A lateral offset measurement by butt coupling of a UHNA-fibre to another one (—) and to a waveguide (− · −) is shown.
with a transverse offset scan of two identical fibres. So ws is now defined as the distance from the best coupling position at which the normalized transmitted power is 1/e = 0.37. Fig. 3 shows such a butt coupling scan measurement of a UHNA-fibre to another one and to a waveguide. The good agreement of the transmitted power shape depending on the lateral misalignment presumes an excellent mode match between the UHNA-fibre and the waveguide. The coupling efficiency factor k is given for a lateral misalignment as [7] k =
21 2 21 + 22
2
2x 2 exp − 2 1 + 22
,
(1)
where 1,2 are the spot sizes of the coupling partner, and x is the lateral distance of their axes. The first part describes the misalignment caused by different spot sizes (x = 0). In the case of coupling the UHNA to the SSMF the losses will be −3.5 dB/facet, which also have been measured. Furthermore, it is possible to estimate the spot size of a waveguide from a coupling scan measurement with a nearly identical fibre and well-known spot size. So from Eq. (1) we obtain 2 − 2 . 2 = 2x1/e (2) 1 This definition works also for elliptical modes. From Fig. 3 (top) we read x1/e = 1.88 m and y1/e = 1.7 m. This results for the fabricated waveguides in wg,x = 1.9 m and wg,y = 1.5 m. In case of elliptical modes we are able to calculate the coupling losses between the UHNA and the
Lateral distance x (m) Measurement (dB) ±0.2 dB Calculation (dB) (w1 = w2 = 1.9 m); Eq. (1) Longitudinal distance (m) Measurement (dB) ±0.2 dB (normalized) Calculation (dB); Eq. (4) (normalized)
0.6 −0.5 −0.43
1 −1.5 −1.2
1.5 −3 −2.7
1 −0.4
3 −0.9
8 −2.9
−0.3
−0.8
−2.3
waveguides by using the equation [7]: 4 ((1,x /2 ) + (2 /1,x )) · ((1,y /2 ) + (2 /1,y )) ≈ 0.03 (≈ −0.12 dB). (3)
k =
The total attenuation caused by the optical interconnection waveguide/UHNA and UHNA/SSMF is about 0.35 dB. This is an excellent coupling efficiency of an optical device to the standard telecom fibre. But unfortunately small modes require a high-precision positioning and tighter tolerances than modes of large diameter. Especially the longitudinal offset, the distance between fibre and waveguide, is crucial. Fig. 4 shows the attenuation above the distance z of the fibre and/or waveguide facets as well as a calculation and measurement. It is clear, that the alignment precision relaxes for larger modes (see in Fig. 4 – SSMF vs. SSMF). The equation describing the pure longitudinal losses is written as follows [7]: k =
4(2 /1 )1/2 (z/na 21 )2 + ((2 /1 )2 + 1)2
.
(4)
is the used wavelength and na is the refractive index of the media between the fibres. In Table 1, the alignment tolerances by coupling the waveguides with an UHNA-fibre
M. Fadel, Roland B. Gentemann / Int. J. Electron. Commun. (AEÜ) 61 (2007) 168 – 171
171
presented. Especially the dependence on the longitudinal fibre chip distance increases the demands on the assembly techniques in comparison to SSMF. For measurement purposes tapered fibres were successfully employed for low loss fibre chip coupling. Fibres with a tapered diameter have a focus-point. In our case the focus length is relatively large so that misalignments in z-direction have a smaller effect on the coupling losses. Additionally, the fibres can be aligned by a maximum search algorithm. This speeds up the loss measurement process of optical waveguides.
References
Fig. 5. A longitudinal offset measurement of tapered fibre with different radii. The best coupling efficiency is achieved for a taper radius of about 10 m.
are listed. Because of the extreme high numerical aperture the impact of the angular misalignment stays in this case negligible. The single channel coupling with the purpose of measuring the waveguide chip shows fluctuating coupling losses due to the non-reproducible longitudinal offset between fibre and waveguide facets. For the z-axis the alignment is conducted manually, because an automated positioning procedure like that for the lateral axes is not possible. To reduce the positioning time by automating the alignment of the zaxes we use tapered fibres [8] instead of the UHNA. They show an optimum coupling by approaching to the waveguide where the best spot-size matching occurs. In Fig. 5 the tapered fibre is presented at the top, and the longitudinal offset measurement of different taper radii can be seen at the bottom. The tapered fibre with the lens radius of 10 m shows the best spot size fitting to the waveguide.
4. Conclusion In this paper, coupling tolerances between high-index silicon-oxynitride waveguides and ultra high NA fibres were
[1] Yasu M, Kawachi M. Fabrication of SiO2 /TiO2 glass planar optical waveguides by soot deposition. Trans Inst Electron Commun Eng Japan 1985;J68-C:454–61. [2] Hoffmann M, Kopka P, Voges E. Low-loss fiber-matched lowtemperature PECVD waveguides with small core dimensions for optical communication systems. IEEE Photon Technol Lett 1997;9(9):1238–40. [3] Bona G. Integrated optical planar waveguide components. Microsystem Technol 2003;9(5):291–4. [4] Fadel M, Voges E. Fibre-coupled high-index PECVD siliconoxynitride waveguides on silicon. In: 207th meeting of the electochem society, vol. 9(5). Quebec, Canada; 2005. [5] Nufern: Ultra high NA fibres, 13.09.2006 www.nufern.com. [6] Streckert J. A new fundamental mode field-radius definition usable for non-Gaussian and noncircular field distributions. J Lightwave Technol 1985;LT-3(2). [7] Neumann E-G. Single-mode fibres. Berlin, Heidelberg, New York: Springer; 1988. [8] Windel Th, Fischer UHP. Integrated optical mode field adapters at the end of single/multimode fibers. Opt Photon 2005;5874.
Maxim Fadel received his Dipl.-Ing. in 2001 from the Universität Dortmund, Germany. Since then he is a Ph.D. student at the High-Frequency Institute of the University Dortmund. Currently he is working in the field of SiON/SiO2 waveguides on silicon. Research interests are optical waveguide fabrication and measurement.
Roland B. Gentemann received his masters degree in 2002 from the University of Leeds, England and 2003 the Dipl.-Ing. from the University Dortmund, Germany. Since then he is a Ph.D. student at the High-Frequency Institute of the Universität Dortmund. Currently he is working in the field of assembly technologies for fibre-optical components. Research interests are silicon micromachining, optical fibre assembly automation and vision systems.