Low-loss edge-coupling thin-film lithium niobate modulator with an efficient phase shifter

Abstract

Thin-film lithium-niobate-on-insulator (LNOI) is a very attractive platform for optical interconnect and nonlinear optics. It is essential to enable lithium niobate photonic integrated circuits with low power consumption. Here we present an edge-coupling Mach–Zehnder modulator on the platform with low fiber-chip coupling loss of 0.5 dB/facet, half-wave voltage V π of 2.36 V, electro-optic (EO) bandwidth of 60 GHz and an efficient thermal-optic phase shifter with half-wave power of 6.24 mW. In addition, we experimentally demonstrate single-lane 200 Gbit/s data transmission utilizing a discrete multi-tone signal. The LNOI modulator demonstrated here shows great potential in energy-efficient large-capacity optical interconnects.

Stable and compact RF-to-optical link using lithium niobate on insulator waveguides

“…The measured coupling losses of approximately 6.2 dB per facet to the waveguides with an air top cladding could be substantially improved by adding a silicon dioxide top cladding at the coupling region and designing on chip couplers acting as mode converters. Using such an approach, impressive results of only 0.5 dB loss per facet have already been achieved with the LNOI platform 34,35 . If adopted here, such a solution would further decrease the laser power required for generating an octave-spanning spectrum and for achieving self-referencing.…”

“…This has been demonstrated over the last years for several different PIC platforms [20][21][22][26][27][28][29][30][31][32] . All these properties, in conjunction with demonstrated techniques for achieving low input coupling losses [33][34][35] , add to the great appeal of the LNOI PIC platform.…”

Spectral control of nonclassical light using an integrated thin-film lithium niobate modulator

“…The total insertion loss was 11 dB, including ber-to-chip coupling loss of ~ 4.5 dB per facet. The coupling and on-chip loss could be reduced to as low as 0.5 dB/facet and 2.7 dB/m by optimized design [45] and fabrication [46]. No increase in insertion loss was observed when turning on RF modulation.…”

Lithium Niobate on Insulator: An Emerging Platform for Integrated Quantum Photonics

“…An alternative approach is based mode converters, which change the geometry of the waveguide to adapt the mode at the edge of a photonic chip to the modes of a butt‐coupled fiber. Such structures, which are conceptually similar to inverse tapers known from silicon photonics, [ 181 ] have been demonstrated in LNOI as well [ 182–186 ] with measured coupling efficiencies close to 90% to tapered or lensed optical fibers. Although these results are encouraging, they still have to be improved to not be a hindrance in the implementation of quantum devices, especially if several photons should be transferred from or to a photonic chip.…”