Boller, Klaus J.

Epping, J.P.

Garcia Porcel, M.A.

Heideman, Rene

Hoekman, M.

Leinse, Arne

van der Slot, Petrus J.M.

English

University of Twente Research Information

Inducing second-order susceptibility in amorphoussilicon nitride waveguidesMarco A. G. PORCEL1*, Jörn P. EPPING2, Marcel HOEKMAN2, Arne LEINSE2, René G.HEIDEMAN2, Peter J. M. VAN DER SLOT1, Klaus-J. BOLLER11Laser Physics and Nonlinear Optics Group, MESA+ Institute for Nanotechnology, University ofTwente, P.O. Box 217, Enschede 7500 AE, The Netherlands2LioniX International B.V., PO Box 456, Enschede 7500 AL, The Netherlands*m.a.garciaporcel@utwente.nlOptical  waveguides  based  on  stoichiometric  silicon  nitride  (Si3N4)  grown  via  low-pressure  chemical  vapor  deposition  (LPCVD)  provide  a  reliable  photonics  platformcharacterized by low loss and a spectrally broad transparency ranging from the visibleto the mid-infrared. Engineering the waveguide dispersion is of special interest since itallows  phase-matching of  third-order  nonlinear optical  processes  such as four-wavemixing, supercontinuum and frequency comb generation.Second-order  nonlinear  processes  such  as  second  harmonic  generation  (SHG)  havebeen observed already in other types of silicon nitride that cannot offer such low loss,such as grown via RF-sputtering. As in such amorphous materials there should be nobulk nonlinear second-order response,  χ(2),  fabrication imperfections such as strainedmicro-crystalline silicon or at the free nitrogen dangling bonds were suggested as theorigin [1].  Field enhancement in Si3N4 ring resonators and Bragg gratings have beenused to increase the efficiency for SHG, with a maximum conversion efficiency of 0.14%[2].Here,  we  present  for  the  time  SHG  in  stoichiometric  Si3N4 waveguides  grown  withLPCVD.  Fig.  1  shows  the  modal  dispersion  vs.  waveguide  width  which  implies  thatphase-matching should  only occur at  a certain waveguide width.  However,  SHG wasFig.1. Effective refractive index of the different guidedmodes for IR and its SH in waveguides of 1 µm by width.observed with various different  waveguide widths.  Secondly,  the output was seen togrow vs. time as shown in Fig. 2, when injecting the pump pulses from a mode-lockedlaser (6 ps pulses at 1064 nm with a 20 MHz repetition rate) with a constant averagepump power.. These results show that the pump radiation induces a temporally growingnonlinear coefficient in the waveguides with a spatially periodic pattern that providesquasi-phase  matching.  The  maximum conversion efficiency  achieved  so far  is  0.5%,corresponding to 50 µW of 532 nm radiation with 10 mW of IR input radiation.References[1]   Dianov, E.M., Starodubov, D.S.,  Quant.Electron. 22, 419-432, 1995[2]   Miller et al.,  Opt.Express 22, 26517-26525, 2014 Fig. 2. Generation of photoinduced χ(2) in four waveguide widths, w, and lengths 60, 74, 74,and 22 mm respectively.

Inducing second-order susceptibility in amorphous silicon nitride waveguides

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Inducing second-order susceptibility in amorphous silicon nitride waveguides

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