Optics & Laser Technology 33 (2001) 455–459 www.elsevier.com/locate/optlastec Fourlayerpolymericmodepolarizationlterforintegratedoptics G.K.Singh,V.K.Sharma,A.Kapoor,K.N.Tripathi ∗ Department of Electronic Science, University of Delhi, South Campus, Benito Juarez Road, New Delhi-110021, India Received 6 March 2001; received in revised form 2 July 2001; accepted 3 July 2001 Abstract We report on our systematic study of fabrication and characterization of four-layer polymer waveguides. Various optical properties (such as refractive index, birefringence, and propagation loss) of polycarbonate and polystyrene waveguides are presented. The thin lm structure consisting of glass= polycarbonate= polystyrene= air has been used for demonstrating polarization lter action because the two polymersarequitedierentwithrespecttotheiropticalanisotropy.ModalelectriceldplotsforbothTEandTMaregeneratedtosupport the observed behavior. It is also observed that the four-layer lightguide exhibits relatively low loss values compared to the monolayer conguration. c  2001 Elsevier Science Ltd. All rights reserved. Keywords: Polymer waveguide; Birefringence; Polarization lter 1. Introduction Integratedoptics(IO)isexpectedtodevelopopticalcom- munication and optical sensing due to its high bandwidth and high resistibility of electromagnetic interference. Many waveguiding devices have been investigated for fabricating optical integrated circuits that are expected to play an im- portant role in the realization of the electro-optic devices. Devices such as directional coupler, modulators, electric eld sensors and non-linear devices (such as second har- monicgeneration)fabricationfrominorganicmaterialslike LiNbO 3 havebeenextensivelyinvestigatedasactivedevice [1].Incontrasttotheinorganicmaterials,electro-optic(EO) polymershavealsobeeninvestigatedduetotheiradvantages such as large optical non-linear coecients, fast response times,lowdielectricconstants,simplefabricationprocesses andeasyfabricationofmultilayerstructures[1–5].Thekey reasonfordevelopingpolymersforopto-electronicapplica- tionsistheirexibility.Thereisalsoexibilityinthesense that polymers are used as spun-on layers that are compati- blewithmanysubstratematerialslikeglass,siliconandInP. Further, as material properties can be tailored for specic application, polymers are an important class of materials foradvancedsensorphotonics[5].Inparticular,polystyrene * Corresponding author. Tel.: +91-11-688-9750; fax: +91-11- 614-5040. E-mail address: gh shyam 99@yahoo.com (K.N. Tripathi). (PS)andpolycarbonate(PC)havehightransparency(more than89%),easyprocessingandhighphysical,chemical,me- chanicalandthermalstability,goodluminoustransmittance, andaremechanicallystrongandcanthereforebeprotably usedinmanyintegratedopticaldevices.Thesematerialsare compatiblewithmanysubstratematerialslikeglass,silicon, GaAs,etc.andarebasicallyusedasspinordip-coatedlay- ers. However, PC has birefringence higher than that of PS and this dierent anisotropic property is used to fabricate a mode polarization lter. 2. Guide preparation and characterization To prepare thin lms, a clear solution (15% weight= volume) of PC was made in the analyzed reagent-grade di-oxane and that of polystyrene in chlorobenzene. A large number of waveguides in PC and PS was fabricated by a dip-coating technique on clean microscopic glass slides at 35 ◦ C (because best guiding results are found at around 35 ◦ C) [6,7]. The speed of drawing is maintained such that about3–6modesaresupportedbythelms.Theguidewas driedat60 ◦ Ctoevaporatetheexcesssolvent.Theguidepa- rameters (refractive index and thickness) were determined by prism coupling technique. A TE= TM polarized He–Ne laser (0:6328 m) was coupled into these lms using a dense int glass prism of refractive index 1.717. 0030-3992/01/$-see front matter c  2001 Elsevier Science Ltd. All rights reserved. PII:S0030-3992(01)00058-5