Claudius Weimann

Silicon-organic hybrid (SOH) frequency comb sources for terabit/s data transmission

We demonstrate frequency comb sources based on silicon-organic hybrid (SOH) electro-optic modulators. Frequency combs with line spacings of 25 GHz and 40 GHz are generated, featuring flat-top spectra with less than 2 dB power variations over up to 7 lines. The combs are used for WDM data transmission at terabit/s data rates and distances of up to 300 km.

Silicon-Organic Hybrid (SOH) and Plasmonic-Organic Hybrid (POH) Integration

Silicon photonics offers tremendous potential for inexpensive high-yield photonic-electronic integration. Besides conventional dielectric waveguides, plasmonic structures can also be efficiently realized on the silicon photonic platform, reducing device footprint by more than an order of magnitude. However, neither silicon nor metals exhibit appreciable second-order optical nonlinearities, thereby making efficient electro-optic modulators challenging to realize. These deficiencies can be overcome by the concepts of silicon-organic hybrid (SOH) and plasmonic-organic hybrid integration, which combine SOI waveguides and plasmonic nanostructures with organic electro-optic cladding materials.

Flexible terabit/s Nyquist-WDM super-channels using a gain-switched comb source

Terabit/s super-channels are likely to become the standard for next-generation optical networks and optical interconnects. A particularly promising approach exploits optical frequency combs for super-channel generation. We show that injection locking of a gain-switched laser diode can be used to generate frequency combs that are particularly well suited for terabit/s super-channel transmission. This approach stands out due to its extraordinary stability and flexibility in tuning both center wavelength and line spacing. We perform a series of transmission experiments using different comb line spacings and modulation formats. Using 9 comb lines and 16QAM signaling, an aggregate line rate (net data rate) of 1.296 Tbit/s (1.109 Tbit/s) is achieved for transmission over 150 km of standard single mode fiber (SSMF) using a spectral bandwidth of 166.5 GHz, which corresponds to a (net) spectral efficiency of 7.8 bit/s/Hz (6.7 bit/s/Hz). The line rate (net data rate) can be boosted to 2.112 Tbit/s (1.867 Tbit/s) for transmission over 300 km of SSMF by using a bandwidth of 300 GHz and QPSK modulation on the weaker carriers. For the reported net data rates and spectral efficiencies, we assume a variable overhead of either 7% or 20% for forward- error correction depending on the individual sub-channel quality after fiber transmission.

Second-order nonlinear silicon-organic hybrid waveguides

We describe a concept for second-order nonlinear optical processes in silicon photonics. A silicon-organic hybrid (SOH) double slot waveguide is dispersion-engineered for mode phase-matching (MPM). The proposed waveguide enables highly efficient nonlinear processes in the mid-IR range. With a cladding nonlinearity of χ(2) = 230 pm/V and 20 dBm pump power at a CW wavelength of 1550 nm, we predict a gain of 14.7 dB/cm for a 3100 nm signal. The suggested structure enables for the first time efficient second-order nonlinear optical mixing in silicon photonics with standard technology.

Ultrafast optical ranging using microresonator soliton frequency combs

Miniaturized optical ranging and tracking Light detection and ranging systems are used in many engineering and environmental sensing applications. Their relatively large size and cost, however, tend to be prohibitive for general use in autonomous vehicles and drones. Suh and Vahala and Trocha et al. show that optical frequency combs generated by microresonator devices can be used for precision ranging and the tracking of fast-moving objects. The compact size of the microresonators could broaden the scope for widespread applications, providing a platform for miniaturized laser ranging systems suitable for photonic integration. Science, this issue p. 884, p. 887 Optical microresonators can be used for light detection and ranging as well as tracking fast-moving objects. Light detection and ranging is widely used in science and industry. Over the past decade, optical frequency combs were shown to offer advantages in optical ranging, enabling fast distance acquisition with high accuracy. Driven by emerging high-volume applications such as industrial sensing, drone navigation, or autonomous driving, there is now a growing demand for compact ranging systems. Here, we show that soliton Kerr comb generation in integrated silicon nitride microresonators provides a route to high-performance chip-scale ranging systems. We demonstrate dual-comb distance measurements with Allan deviations down to 12 nanometers at averaging times of 13 microseconds along with ultrafast ranging at acquisition rates of 100 megahertz, allowing for in-flight sampling of gun projectiles moving at 150 meters per second. Combining integrated soliton-comb ranging systems with chip-scale nanophotonic phased arrays could enable compact ultrafast ranging systems for emerging mass applications.

High-Quality Optical Frequency Comb by Spectral Slicing of Spectra Broadened by SPM

This paper introduces a spectral slicing technique that extends the useful spectral range of frequency combs generated through self-phase modulation (SPM) of mode-locked laser pulses. When generating frequency combs by SPM, the spectral range with high-quality carriers is usually limited due to spectral minima carrying too little power. To overcome these limitations, we combine suitable slices of broadened and nonbroadened spectra. The concept was experimentally verified: A total number of 325 consecutive equidistant subcarriers span a bandwidth of 4 THz. All subcarriers have an optical carrier-power-to-noise-power-density ratio (OCNR) larger than 25.8 dB (0.1 nm) and were derived from one mode-locked laser with a mode linewidth of approximately 1 kHz. The signal quality of the comb and in particular of each subcarrier was ultimately tested in a terabit-per-second communication experiment. The comb quality allowed us to transmit 32.5 Tb/s over 225 km with 100 Gb/s dual polarization 16-ary quadrature amplitude modulation (16QAM) signals on each of the subcarriers.

Optical coherence tomography system mass-producible on a silicon photonic chip

Miniaturized integrated optical coherence tomography (OCT) systems have the potential to unlock a wide range of both medical and industrial applications. This applies in particular to multi-channel OCT schemes, where scalability and low cost per channel are important, to endoscopic implementations with stringent size demands, and to mechanically robust units for industrial applications. We demonstrate that fully integrated OCT systems can be realized using the state-of-the-art silicon photonic device portfolio. We present two different implementations integrated on a silicon-on-insulator (SOI) photonic chip, one with an integrated reference path (OCTint) for imaging objects in distances of 5 mm to 10 mm from the chip edge, and another one with an external reference path (OCText) for use with conventional scan heads. Both OCT systems use integrated photodiodes and an external swept-frequency source. In our proof-of-concept experiments, we achieve a sensitivity of -64 dB (-53 dB for OCTint) and a dynamic range of 60 dB (53 dB for OCTint). The viability of the concept is demonstrated by imaging of biological and technical objects.

Microresonator-based optical frequency combs for high-bitrate WDM data transmission

A nonlinear high-Q SiN microresonator is used as a frequency comb generator for data transmission at 170.8 Gbit/s. The main sources for signal impairment are identified. Further dispersion engineering is crucial for Terabit/s transmission.

Coherent terabit communications using a quantum-dash mode-locked laser and self-homodyne detection

We transmit 18 GBd 16QAM signals on 25 spectral lines of a quantum-dash mode-locked laser diode, achieving a 1.562 Tbit/s aggregate data rate. Phase noise is cancelled by self-homodyne detection using LO tones transmitted with the signal.

Terabit/s data transmission using optical frequency combs

Terabit/s interconnects rely on advanced wavelength-division multiplexing (WDM) schemes. However, while efficient photonic-electronic interfaces can be efficiently realized on silicon-on-insulator chips, dense integration of WDM laser sources still represents a major challenge. Chip-scale frequency comb sources are an attractive alternative for providing optical carriers for WDM transmission. In this paper we give an overview on our recent work towards terabit/s data transmission using optical frequency combs. We demonstrate transmission of a 32.5 Tbit/s data stream using a modelocked solid-state laser as an optical source. Our current experiments aim at transmission schemes that exploit Kerr nonlinearities in high-Q microresonators for frequency comb generation.