Hybrid electro-optic modulator combining silicon photonic slot waveguides with high-k radio-frequency slotlines

Abstract

Electro-optic (EO) modulators rely on interaction of optical and electrical signals with second-order nonlinear media. For the optical signal, this interaction can be strongly enhanced by using dielectric slot-waveguide structures that exploit a field discontinuity at the interface between a high-index waveguide core and the low-index EO cladding. In contrast to this, the electrical signal is usually applied through conductive regions in the direct vicinity of the optical waveguide. To avoid excessive optical loss, the conductivity of these regions is maintained at a moderate level, thus leading to inherent RC-limitations of the modulation bandwidth. In this paper, we show that these limitations can be overcome by extending the slot-waveguide concept to the modulating radio-frequency (RF) signal. Our device combines an RF slotline that relies on BaTiO3 as a high-k dielectric material with a conventional silicon photonic slot waveguide and a highly efficient organic EO cladding material. In a proof-of-concept experiment, we demonstrate a 1 mm-long Mach-Zehnder modulator that offers a 3 dB-bandwidth of 76 GHz and a 6 dB-bandwidth of 110 GHz along with a small π-voltage of 1.3 V (UπL = 1.3 V mm). To the best of our knowledge, this represents the largest EO bandwidth so far achieved with a silicon photonic modulator based on dielectric waveguides. We further demonstrate the viability of the device in a data transmission experiment using four-state pulse-amplitude modulation (PAM4) at line rates up to 200 Gbit/s. Our first-generation devices leave vast room for further improvement and may open an attractive route towards highly efficient silicon photonic modulators that combine sub-1 mm device lengths with sub-1 V drive voltages and modulation bandwidths of more than 100 GHz.

Design Methodologies for Integrated Quantum Frequency Processors

“…The construction of high-speed and low-loss phase modulators has remained an enduring challenge in integrated photonics, complicated by the lack of an efficient electro-optic effect in silicon. Recent developments in thin-film lithium niobate [42], [43] and CMOS-compatible silicon-organic hybrid modulators [44]- [47] appear particularly promising to supplant the lossy plasma-dispersion modulators standard in silicon photonics [48], [49]. Yet because modulator performance depends heavily on aspects such as material platform, doping, and device geometry-with CMOS foundries often providing black-box elements as part of their process design kits-for our purposes here we assume the availability of a linear EOM imparting the desired phase shifts without appreciable voltage-dependent loss.…”

Optically Enabled ADCs and Application to Optical Communications

“…Spectral slicing of the input signal is an alternative approach to time interleaving that has been applied to highspeed data conversion, both in all-electrical and optically enabled ADCs. The optically enabled, spectrally-sliced ADC presented in this section is based on the combination of an ultra-broadband EOM [17], [18], employed to convert the RF input signal into the optical domain, and an ePIC implementing spectral slicing and coherent detection of the aforementioned modulated signal. Electronic-photonic integration combines high scalability and low cost and enables scaling of spectrally sliced data converters to achieve large analog bandwidths with high ENOB.…”

“…In this paper, we review some of our recent work on chipscale integrated time-interleaved and spectrally-sliced photonically enabled ADCs, with a particular focus on the integration of optical filters with electronic receiver and sampling circuits in electronic-photonic integrated circuits (ePICs). Work on in-package integration of ultra-broadband modulators [17], [18] by means of multi-chip assemblies as well as miniaturization of low jitter comb sources is also under way, but not covered here in details. After covering time-interleaved and spectrally-sliced ADCs in Sections II and III, as well as a use case of frequency stitching in broadband coherent receivers utilizing the nonlinear Fourier transform (NFT) in Section IV, we give an outlook on optically enabled ADCs in optical communications in Section V.…”

Design and synthesis of chromophores with enhanced electro-optic activities in both bulk and plasmonic–organic hybrid devices

“…This journal is © The Royal Society of Chemistry 2022 computing, sensor technology, and ultra-broadband signal processing at GHz-THz bandwidths. [1][2][3][4][5][6] Over the past decade, considerable progress has been made with respect to plasmonic-organic hybrid (POH) 2,3,5,[7][8][9] and silicon-organic hybrid (SOH) [10][11][12][13][14][15][16][17][18][19] technologies affording higher bandwidth (4500 GHz), 20 smaller footprints (o20 mm 2 ), better energy efficiency (o100 attojoule/bit), 10,21 as well as dramatically lower V p L (the p-voltage-length product). 5,22 State-of-the-art POH and SOH platforms combine the high intrinsic EO activity of organic chromophores with the tight confinement and improved overlap of electrical and optical fields achievable in nanophotonic devices, enabling ultra-compact, low-voltage devices permitting chip-scale integration with CMOS electronics.…”