Gilles Rasigade

40 Gbit/s low-loss silicon optical modulator based on a pipin diode

40 Gbit/s low-loss silicon optical modulators are demonstrated. The devices are based on the carrier depletion effect in a pipin diode to generate a good compromise between high efficiency, speed and low optical loss. The diode is embedded in a Mach-Zehnder interferometer, and a self-aligned fabrication process was used to obtain precise localization of the active p-doped region in the middle of the waveguide. Using a 4.7 mm (resp. 0.95 mm) long phase shifter, the modulator exhibits an extinction ratio of 6.6 dB (resp. 3.2 dB), simultaneously with an optical loss of 6 dB (resp. 4.5 dB) at the same operating point.

Light emission in silicon from carbon nanotubes.

The use of optics in microelectronic circuits to overcome the limitation of metallic interconnects is more and more considered as a viable solution. Among future silicon compatible materials, carbon nanotubes are promising candidates thanks to their ability to emit, modulate, and detect light in the wavelength range of silicon transparency. We report the first integration of carbon nanotubes with silicon waveguides, successfully coupling their emission and absorption properties. A complete study of this coupling between carbon nanotubes and silicon waveguides was carried out, which led to the demonstration of the temperature-independent emission from carbon nanotubes in silicon at a wavelength of 1.3 μm. This represents the first milestone in the development of photonics based on carbon nanotubes on silicon.

Ten Gbit/s ring resonator silicon modulator based on interdigitated PN junctions

10 Gbit/s silicon modulator based on carrier depletion in interdigitated PN junctions is experimentally demonstrated. The phase-shifter is integrated in a ring resonator, and high extinction ratio larger than 10 dB is obtained in both TE and TM polarizations. VπLπ of about 2.5 V × cm and optical loss lower than 1 dB are estimated. 10 Gbit/s data transmission is demonstrated with an extinction ratio of 4 dB.

Low loss 40 Gbit/s silicon modulator based on interleaved junctions and fabricated on 300 mm SOI wafers

We demonstrate high-speed silicon modulators based on carrier depletion in interleaved pn junctions fabricated on 300 mm-SOI wafers using CMOS foundry facilities. 950 µm-long Mach Zehnder (MZ) and ring resonator (RR) modulator with a 100 µm radius, were designed, fabricated and characterized. 40 Gbit/s data transmission has been demonstrated for both devices. The MZ modulator exhibited a high extinction ratio of 7.9 dB with only 4 dB on-chip losses at the operating point.

Ring-Assisted Mach–Zehnder Interferometer Silicon Modulator for Enhanced Performance

A high-speed ring-assisted Mach-Zehnder interferometer (RAMZI) silicon modulator is reported and experimentally demonstrated. The RAMZI optical structure relaxes the optimum coupling condition of the ring without degrading the modulator performance, which therefore improves the modulator robustness against fabrication deviations and could eventually lead to an enhanced modulation bandwidth. Hence, our RAMZI silicon modulator, based on carrier depletion in a pipin active structure, exhibits a 3 dB electro-optical bandwidth of 19 GHz, enabling up to 20 Gbit/s data transmission over a RF/optical interaction length of only ~200 μm.

High extinction ratio 10 Gbit/s silicon optical modulator

High speed and high extinction ratio silicon optical modulator using carrier depletion is experimentally demonstrated. The phase-shifter is a 1.8 mm-long PIPIN diode which is integrated in a Mach Zehnder interferometer. 8.1 dB Extinction Ratio at 10 Gbit/s is obtained simultaneously with optical loss as low as 6 dB.

A 40 Gbit/s optical link on a 300-mm silicon platform

We demonstrated 40 Gbit/s optical link by coupling a silicon (Si) optical modulator to a germanium (Ge) photo-detector from two separate photonic chips. The optical modulator was based on carrier depletion in a pn diode integrated in a 950-µm long Mach-Zehnder interferometer. The Ge photo-detector was a lateral pin diode butt coupled to a silicon waveguide. The overall loss, which is mainly due to coupling (3 grating couplers times ~4 dB) was estimated to be lower than 18 dB. That also included modulator loss (4.9-dB) and propagation loss (<1 dB/cm). Both optoelectronic devices have been fabricated on a 300-mm CMOS platform to address high volume production markets.

Analytical model for depletion-based silicon modulator simulation.

An original method to simulate depletion-based silicon modulators based on an analytical description of the active region is presented. This method is fast and efficient in particular for performance optimization. It is applied for a lateral diode integrated in a rib waveguide, and a comparison is performed with classical 2D numerical simulation. A very good agreement is obtained, showing the accuracy and efficiency of this analytical method.

Recent progress in fast silicon modulators

Impressive progress have been performed on high speed silicon optical modulators for a few years. An overview of recent works will be reported and new results on a lateral pin diode will be presented.

Silicon-based optical modulation within the HELIOS project

The HELIOS project is a European funded program which focuses on the development and integration of the different photonic and electronic building block components required to form high performance photonic circuits with a variety of functionality. One of the key photonic building block components central to most photonic applications is the optical modulator which is required to write data onto an optical carrier. Within the project two designs of carrier depletion based phase modulator are under development, together with a means of enhancing the modulation effect using slow wave and ring resonator based structures. In this work modulation results from the two phase shifters are presented along with passive results from related slow wave and resonator structures.