Baoquan Chen

Silicon-organic hybrid (SOH) IQ modulator using the linear electro-optic effect for transmitting 16QAM at 112 Gbit/s

Advanced modulation formats call for suitable IQ modulators. Using the silicon-on-insulator (SOI) platform we exploit the linear electro-optic effect by functionalizing a photonic integrated circuit with an organic χ(2)-nonlinear cladding. We demonstrate that this silicon-organic hybrid (SOH) technology allows the fabrication of IQ modulators for generating 16QAM signals with data rates up to 112 Gbit/s. To the best of our knowledge, this is the highest single-polarization data rate achieved so far with a silicon-integrated modulator. We found an energy consumption of 640 fJ/bit.

Environmental Stress Testing of Electro–Optic Polymer Modulators

Low Vpi electro-optic (EO) polymer modulators were environmental stress tested at both the chip and packaged device level. Different top clad materials showed different results for high-temperature and temperature cycle testing, which is related mostly to coefficient of thermal expansion (CTE) mismatches and/or adhesion properties of the clads related to other materials in the devices stack and to the substrate and electrode materials. With thoroughly compatible cladding, devices that are thermally stable for over 5000 h at 85degC have been achieved. High optical power ( 500 mW @ 1550 nm) tests showed the photochemical stability of the EO polymer material in hermetically sealed packages. The results demonstrate that clad polymers and interactions between devices layers are of concern for achieving environmentally stable EO polymers modulators.

Small form factor thin film polymer modulators for telecom applications

40Gbps Small form factor thin film polymer on silicon (TFPS) EO modulators have been presented. The TFPS modulators have a small size, low Vπ, broad bandwidth and zero chirp, which are desirable for telecom applications.

Material development and processing for electro-optic device systems

New crosslinked clad polymers were developed for electro-optic polymer modulators with special attention paid to properties such as refractive index tunability, optical loss, and conductivity. These cured polymers showed relatively low optical loss at 1550 nm and desirable conductivity. The clads were used to fabricate electro-optic devices having mode profiles closely matched to that of optical fibers in order to reduce insertion loss. A new hardmasking technique was developed to define Mach-Zehnder rib waveguides by photolithography and dry etching with high reliability and surface smoothness. The hardmasking technique demonstrated flexibility in defining waveguides made with electro-optic polymers having different reactivity towards etchant gasses.

Recent advances in commercial electro-optic polymer modulator

We present the state-of-art polymer-based electro-optic modulator, which, for the first time, can be used in real commercial systems. The devices work up to 100 Gbps and possess the Vpi as low as 1.6 V.

Low half-wave voltage modulators using nonlinear optical polymers

The optical and material properties of AJ309 electro-optic (EO) polymer were systematically studied with the objective to fabricate an optimized integrated device. Both bottom and top cladding materials were developed at Lumera to match the processibility of AJ309, and sustain high poling voltage needed for an effective poling process. A device fabrication process is developed. The degree of crosslinking of the EO polymer before poling is minimized by processing the top clad polymer at room-temperature. The UV-curable top clad has shown no detectable chemical damage to the EO polymer after the deposition process of the top clad, thus maintaining the integrity of the interface between top clad and AJ309 core. A 2.1 cm long active length Mach-Zehnder modulator with low half-wave voltage (Vπ) of 1.1 V @1550 nm was fabricated using the AJ309 EO polymer and in-house cladding materials. Other device parameters are also reported.

Development of side-chain NLO polymer materials with high electro-optic activity and long-term stability

The electro-optic coefficient and long-term dipole alignment stability are two major factors in the development of high performance NLO materials for the application of high-speed EO devices. We have developed a high performance non-linear organic chromophore and incorporated it into a crosslinkable side-chain polyimide system. The polymer was synthesized through stepwise grafting of the crosslinker followed by the chromophore onto the polyimide backbone via esterification. Different chromophore loading levels were achieved by adjusting the crosslinker/chromophore feeding ratio. The polyimides films were contact-poled with second-harmonic generation monitoring. A large EO coefficient value was obtained and good long-term thermal stability at 85°C was observed.

High-speed Plasmonic Modulators

Plasmonic modulators integrated with silicon photonic circuits are discussed. First, a 29 μm long phase modulator operating at 40Gbit/s is demonstrated. Then, an absorption modulator is presented exploiting the plasma effect in metal oxide layers.

From silicon-organic hybrid to plasmonic modulation

Organic materials combined with strongly-guiding silicon waveguides have led to a new generation of low-power, high-speed linear-electro optic modulators. In this paper we review the so-called silicon-organic hybrid approach and the more recent plasmonic successor.

Optical Loss Analysis of Electro-Optic Polymers through Two-Layer Measurement

The optical loss of polymeric electro-optic device (~3.0 dB/cm) has been much higher than that of core polymers (<1.8 dB/cm) used, which is related to surface morphology of bottom clad.