40 Gbit/s electroabsorption modulators with impedance-controlled electrodes

Over 67 GHz bandwidth hybrid silicon electroabsorption modulator with asymmetric segmented electrode for 13 μm transmission

“…A segmented electrode with low impedance active modulation segments and high impedance passive transmission line (TL) segments being alternately cascaded emerges to be a better method regarding the overall consideration of the modulation bandwidth, the microwave reflection and the modulation efficiency. The segmented electrode was first proposed as an impedance-controlled electrode in [14] and then extended to the case with multiple active segments in [15]. Here, due to the use of a short active length, we use the configuration with only one active segment to avoid additional optical loss [15].…”

“…In this paper, we will report a distributed hybrid silicon modulator designed for a higher speed and a longer transmission distance. The improvement mainly comes from two aspects: first, an asymmetric segmented transmission line has been designed as the distributed electrode configuration [11,[14][15][16] to reduce the microwave reflection and improve the modulation bandwidth; second, we utilize a new InAlGaAs quantum well stack and shift the operation wavelength of the modulator to the 1.3 μm transmission window for datacom applications. 1 shows the detailed structure of the III-V epitaxy stack and the SOI wafer used for our fabrication.…”

Low-Power-Driven and Low-Optical-Loss 40-Gb/s Electroabsorption Modulator Using Self-Aligned Two-Step Undercut-Etched Waveguide

“…Several groups have involved in such EAMs or DFB-laser-integrated EAMs for above-40-Gb/s applications [4]- [9]; however, up to date, high driving power levels are still needed. Using segmented electrodes to enhance waveguide microwave properties, such as impedance, 100-Gb/s performances from EAM [5] and DFBlaser-integrated EAM [6] have been demonstrated. By defining a short waveguide to reduce the parasitic capacitance, highspeed 40-Gb/s data modulation has been shown in several works [4]- [9].…”

“…In our previous work, using a new scheme of waveguide by selective undercut-etching method, low electrical loss of a waveguide has been demonstrated from low capacitance as well as low cladding layer impedance, thus leading to high-speed modulation in a long waveguide [11], [12]. One of the main physical limits affecting high-bit-rate modulation of EAM is high-speed properties of waveguides [6], [11]- [13]. Due to high parasitics in EAM waveguides (p-i-n heterostructure), high-frequency electrical properties are restricted by long charging time in loaded capacitance and high current resistance in the cladding layer, leading to high electrical loss.…”

High-speed traveling-wave electro-absorption modulators

“…Their epitaxial structure makes monolithic integration with continuous-wave (CW) lasers possible and they can be designed to require voltages and currents that can be provided by electronics based on emerging transistor technologies even for speeds above 40Gb/s. Distributed high-speed EAMs with travelling-wave (TW) electrodes overcome the RC limitation due to the junction capacitance [1][2][3][4][5]. However, the characteristic impedance of the electrodes is normally only 20-25Ω for devices with good optoelectronic modulation efficiency, resulting in relatively large electrical reflections in high-speed circuits with a standard 50Ω impedance level.…”