Fabrication of Replicated Polymer Optical Waveguide Yoshitaka TATARA and Hayami HOSOKAWA

Advanced Device Laboratory, Corporate R&D Headquarters, OMRON Corporation, 9-1, KIZUGAWADAI, KIZUGAWA-CITY, KYOTO, 619-0283, JAPAN

Phone: +81-774-74-2013, FAX: +81-774-74-2001, E-mail: yoshitaka_tatara@omron.co.jp 1. Introduction As an optical communication device, the polymer optical waveguide attracts many attention from market by the viewpoint of low cost, recently. The replication process is considered as one of the technique of microfabrication process with polymer materials, and is under development to become as the next generation technology of lithography. In this paper, the manufacturing technology of polymer optical waveguide called SPICA(Stacked Polymer optical IC/Advanced 1-4)) utilizing our unique replication process and the results of the applications are presented. 2. Fabrication process The replication process flow of polymer optical waveguide is shown in Fig.1 and the details are explained as follows. (1) A glass substrate and a stamper for printing is prepared. (2) The UV resin for the under cladding layer is dispensed on the glass substrate. And the resin is pressed by the stamper and cured by UV light to form the under cladding layer. (3) The UV resin for the core which has slightly different refractive index from that of the cladding layer is dispensed on a under cladding layer and cured by UV light to form the core part. (4) Again, the UV resin for the over cladding layer is dispensed on the under cladding layer. And the resin is pressed by the cover glass and cured by UV light to form the over cladding layer. (5) The wafer of implanted polymer optical waveguides is cut by diamond blade to form individual chip.

Fig.1 replication process flow of polymer optical waveguide 3. Manufactured results and basic characteristics Fig.2 is a photograph of the waveguide's cross-section and a white trapezoid part is the core department where is the light is propagated through. And, fig.3 shows the Y-branch part of the 1x8 optical coupler. The fine tip shape of the Y-branch part is confirmed with this photograph. The core size of this waveguide is 5.25um x 5.25um and the refractive index difference is 0.44%. A propagation mode is a single mode, and the propagation losses are 0.2dB/cm at wavelength=1.31um and 0.5dB/cm at wavelength=1.55um respectively. This performance shows that this replicated polymer optical waveguide has reached to the practical use level for the first time.

glass substrate

substrate

(3)core forming(1)preparing substrate And stamper

cover

stamper cover glass waveguide pattern

(4)over cladding layer forming

Under cladding layer

Over cladding layer

core

wafer image

cross-section image

(2)under cladding layer forming

substrate substrate substrate

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Fig.2 cross-section photograph of core Fig.3 Y-branch optical waveguide pattern In addition, about the endurance characteristics that is generally concerned about a polymer waveguide, the test based on Telcordia standard, which is considered as the industry standard, is conducted with our 1x8 optical coupler modules. After the most severe storage test in the high temperature and high humidity (85degree C/85%RH, 2000h), the change of insertion loss was less than 0.3dB, and the practical use level in endurance characteristics is confirmed. 4. Film type optical waveguide The expectation of replacing electrical signal lines in body of mobile devices by optical signal line which can transfer data at very high rate is growing. This expectation is based on the recent progress of the calculation performance and the recent increase of communication density, for instance the handling of graphical data with high quality and resolution. Along with the need of smaller mobile devices, the film optical waveguide for optical signal line is considered as the solution. The flexible film optical waveguide realizes fast data transfer and fit in narrow space of small mobile device. Fig.4 is the photograph of the film waveguide which was fabricated by a replication method. The test result of the propagation loss was less than 0.1dB/cm at wavelength=850nm, and a change of insertion loss was less than 0.2dB at radius of curvature of 1mm. Furthermore, as a result of 1 million times of repeatedly flexural tests at the same radius, a change of insertion loss was less than 0.2dB. With these results, it is confirmed that this film waveguide is also at the practical use level. 5. Conclusion In this paper, our replication process for polymer optical waveguide is presented and the performance of the single mode waveguide and the film type waveguide both at characteristic of a practical use level are discussed. In the future, we would like to contribute to development of networked society as a key device of optical communication by raising technology of stability required a mass production. 6. Reference 1) H. Hosokawa, J. Takagi, N. Horie, S. Aoyama, S. Ogata and T. Yamashita, “Novel single mode channel waveguide fabricated by photopolymerization for integrated optic sensors”, Proc. OFS’89, pp30-35 (1989). 2) N. Yasuda and H. Hosokawa, “Replicated Polymer Optical Waveguides”, Proc. SPIE, 5246, pp.103-111 (2003). 3) Y. Ishida, K. Hayamizu and H. Hosokawa, “Replicated Polymer Waveguides for Access Applications”, Proc. OFC’06, OWF4 (2006). 4) Y. Terakawa and H. Hosokawa, “Replicated Polymer Optical Waveguides and the Application”, Proc. SPIE, 6389, 63890H (2006).

5um Core

Over Cladding Layer

Under Cladding Layer 5um

Fig.4 photograph of film waveguide

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