Abstract
Cs+ ion exchange in RbTiOPO4 and (Yb,Nb):RTP/RTP(001) has been used to locally increase the refractive indices for waveguide circuit fabrication. Ti masks were fabricated on RTP samples by conventional photolithography. Cs+ exchange was done using a CsNO3 melt at 698 K during 2 h. Elemental analysis confirms an Cs+ profile with a variable depth. Apparently the Cs+ exchange is disfavored in the doped epitaxial sample. The refractive index variation is higher for nz than for nx,y. Near-field images of the guided modes at 633, 1064 and 1520 nm were recorded. The optical characterization shows propagation losses of 5 dB/cm at 1520 nm.
Highlights
KTiOPO4 (KTP) and its isostructural RbTiOPO4 (RTP) are well known crystalline dielectric materials with excellent properties for non-linear optical applications
RTP bulk crystal domain map: We have studied the ferroelectric domain structures in an RTP bulk single crystal
In summary, waveguides based on Cs+ exchange in RbTiOPO4(001) and (Yb,Nb):RbTiOPO4 have been fabricated in different configurations: straight, S-bend and Mach-Zehnder structures (MZ)
Summary
KTiOPO4 (KTP) and its isostructural RbTiOPO4 (RTP) are well known crystalline dielectric materials with excellent properties for non-linear optical applications. RTP has similar non-linear optical coefficients to KTP [2], a higher laser damage threshold (~2 times larger than that of KTP) [3, 4], a wide range of wavelength and angular acceptance for frequency doubling, high chemical stability, and low photorefractive damage susceptibility [5]. The doping couple (Yb,Nb) doesn’t change the ionic conductivity along the c direction in comparison with RTP, but interestingly it increases significantly the ionic conductivity along a crystallographic direction [17], so the (Yb,Nb) codoping is not expected to favor the unidirectional exchange process. The motivation of the current work is to demonstrate the Cs+ exchange process for fabricating integrated optic devices such as Y-splitters and Mach-Zehnder structures (MZ) on RTP (001) substrates and (Yb,Nb):RTP epitaxial layers, and to optically characterize the WG structures obtained
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