Fast amplitude modulation up to 1.5 GHz of mid-IR free-space beams at room-temperature.

Applications relying on mid-infrared radiation (λ ~ 3-30 µm) have progressed at a very rapid pace in recent years, stimulated by scientific and technological breakthroughs like mid-infrared cameras and quantum cascade lasers. On the other side, standalone and broadband devices allowing control of the beam amplitude and/or phase at ultra-fast rates (GHz or more) are still missing. Here we show a free-space amplitude modulator for mid-infrared radiation (λ ~ 10 µm) that can operate at room temperature up to at least 1.5 GHz (-3dB cutoff at ~750 MHz). The device relies on a semiconductor heterostructure enclosed in a judiciously designed metal-metal optical resonator. At zero bias, it operates in the strong light-matter coupling regime up to 300 K. By applying an appropriate bias, the device transitions towards the weak-coupling regime. The large change in reflectance is exploited to modulate the intensity of a mid-infrared continuous-wave laser up to 1.5 GHz.

Integrated waveguide PIN photodiodes exploiting lateral Si/Ge/Si heterojunction.

Germanium photodetectors are considered to be mature components in the silicon photonics device library. They are critical for applications in sensing, communications, or optical interconnects. In this work, we report on design, fabrication, and experimental demonstration of an integrated waveguide PIN photodiode architecture that calls upon lateral double Silicon/Germanium/Silicon (Si/Ge/Si) heterojunctions. This photodiode configuration takes advantage of the compatibility with contact process steps of silicon modulators, yielding reduced fabrication complexity for transmitters and offering high-performance optical characteristics, viable for high-speed and efficient operation near 1.55 µm wavelengths. More specifically, we experimentally obtained at a reverse voltage of 1V a dark current lower than 10 nA, a responsivity higher than 1.1 A/W, and a 3 dB opto-electrical cut-off frequency over 50 GHz. The combined benefits of decreased process complexity and high-performance device operation pave the way towards attractive integration strategies to deploy cost-effective photonic transceivers on silicon-on-insulator substrates.

Low voltage 25Gbps silicon Mach-Zehnder modulator in the O-band.

In this work, a 25 Gb ps silicon push-pull Mach-Zehnder modulator operating in the O-Band (1260 nm - 1360 nm) of optical communications and fabricated on a 300 mm platform is presented. The measured modulation efficiency (VπLπ) was comprised between 0.95 V cm and 1.15 V cm, which is comparable to the state-of-the-art modulators in the C-Band, that enabled its use with a driving voltage of 3.3 Vpp, compatible with BiCMOS technology. An extinction ratio of 5 dB and an on-chip insertion losses of 3.6 dB were then demonstrated at 25 Gb ps.

Germanium avalanche receiver for low power interconnects.

Recent advances in silicon photonics have aided the development of on-chip communications. Power consumption, however, remains an issue in almost all integrated devices. Here, we report a 10 Gbit per second waveguide avalanche germanium photodiode under low reverse bias. The avalanche photodiode scheme requires only simple technological steps that are fully compatible with complementary metal oxide semiconductor processes and do not need nanometre accuracy and/or complex epitaxial growth schemes. An intrinsic gain higher than 20 was demonstrated under a bias voltage as low as -7 V. The Q-factor relating to the signal-to-noise ratio at 10 Gbit per second was maintained over 20 dB without the use of a trans-impedance amplifier for an input optical power lower than -26 dBm thanks to an aggressive shrinkage of the germanium multiplication region. A maximum gain over 140 was also obtained for optical powers below -35 dBm. These results pave the way for low-power-consumption on-chip communication applications.

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.

Zero-bias 40Gbit/s germanium waveguide photodetector on silicon.

We report on lateral pin germanium photodetectors selectively grown at the end of silicon waveguides. A very high optical bandwidth, estimated up to 120GHz, was evidenced in 10 µm long Ge photodetectors using three kinds of experimental set-ups. In addition, a responsivity of 0.8 A/W at 1550 nm was measured. An open eye diagrams at 40Gb/s were demonstrated under zero-bias at a wavelength of 1.55 µm.

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.

42 GHz p.i.n Germanium photodetector integrated in a silicon-on-insulator waveguide.

A compact pin Ge photodetector is integrated in submicron SOI rib waveguide. The detector length is reduced down to 15 microm using butt coupling configuration which is sufficient to totally absorb light at the wavelength of 1.55 microm. A -3 dB bandwidth of 42 GHz has been measured at a 4V reverse bias with a responsivity as high as 1 A/W at the wavelength of 1.55 microm and a low dark current density of 60 mA/cm(2). At a wavelength of 1.52 microm, a responsivity of 1 A/W is obtained under -0.5 V bias. The process is fully compatible with CMOS technology.

High speed and high responsivity germanium photodetector integrated in a Silicon-On-Insulator microwaveguide.

We report the experimental demonstration of a germanium metal-semiconductor-metal (MSM) photodetector integrated in a SOI rib waveguide. Femtosecond pulse and frequency experiments have been used to characterize those MSM Ge photodetectors. The measured bandwidth under 6V bias is about 25 GHz at 1.55 microm wavelength with a responsivity as high as 1 A/W. The used technological processes are compatible with complementary-metal-oxide-semiconductor (CMOS) technology.