Edgar Krune

High bandwidth, high responsivity waveguide-coupled germanium p-i-n photodiode

A novel waveguide-coupled germanium p-i-n photodiode is demonstrated which combines high responsivity with very high -3 dB bandwidth at a medium dark current. Bandwidth values are 40 GHz at zero bias and more than 70 GHz at -1 V. Responsivity at 1.55 µm wavelength ranges from 0.84 A/W at zero bias to 1 A/W at -1 V. Room temperature dark current density at -1 V is about 1 A/cm2. The high responsivity mainly results from the use of a new, low-loss contact scheme, which moreover also reduces the negative effect of photo carrier diffusion on bandwidth.

Modeling of Mode Coupling in Multimode Fibers With Respect to Bandwidth and Loss

A fast, accurate and simple field coupling model is presented which is capable of describing mode coupling effects due to bends and splices in multimode fibers with parabolic index profile as well as the coupling losses induced by this process. This model is validated numerically by comparing the results to the well-known coupled amplitude theory model yielding the same relative bandwidth increase behavior as long as the coupling losses are the same. It is shown, that the number of discrete segments used in this model can be reduced considerably as long as the coupling losses are kept constant. The effect of mode coupling on the differential group delay, mode dependent loss, bandwidth gain and impulse response width reduction are analyzed. It is shown that the relative bandwidth gain induced in MMF links induced by the coupling process is independent of fiber parameters or number of guided modes; it can be fully characterized by coupling induced losses. The model is compared to well-known results given by power coupling models and a good agreement is observed for high steady state loss values.

High-performance photonic BiCMOS process for the fabrication of high-bandwidth electronic-photonic integrated circuits

An advanced photonic BiCMOS process is demonstrated capable, on the receiver side, for 100 Gb/s optical line rate. Key components of this process are monolithically integrated wave-guide Ge photodiodes showing more than 70 GHz bandwidth and 1 A/W responsivity, and SiGe HBTs with fT/fmax values of 240/290 GHz.

Jitter Analysis of Optical Clock Distribution Networks in Silicon Photonics

The lower limit of timing jitter due to optical and thermal noise is derived for the transmission of pulses as a clock signal. Clock distribution networks are analyzed in silicon photonics in providing pulse trains to electronic circuits. Two photon absorption and free carrier effects in silicon waveguides define maximum output power of the clock distribution network in dependence on pulsewidth and pulse energy. Simulations show that multiple electronic circuits on a silicon chip can be synchronized by optical pulses with femtosecond precision.

High-performance BiCMOS Si photonics platform

Photonic BiCMOS is a novel technology for fabricating electronic-photonic integrated circuits. Broadband silicon photonics devices such as germanium photodiodes and depletion type Mach-Zehnder modulators were monolithically integrated in a high performance SiGe BiCMOS baseline process. Integration aspects and first examples of demonstrator circuits shall be reviewed.

A monolithically integrated opto-electronic clock converter in photonic SiGe-BiCMOS technology

A novel monolithic opto-electronic clock converter integrated in a photonic SiGe-BiCMOS technology is presented, which turns an ultrashort optical pulse train generated by a hybrid mode-locked laser into a low-jitter electrical square wave with sharp transitions. The integrated circuit includes optical waveguides as well as grating couplers, a high-bandwidth (> 30 GHz) Ge-photodiode, a frequency divider-by-two implemented by SiGe bipolar transistors, photodiode characterization circuits and an optical monitoring path. The integrated circuit has been successfully tested at laser pulse repetition rates of up to 10 GHz. At this pulse repetition rate, the generated 5 GHz electrical square wave signal features a wideband phase noise floor <;-160 dBc/Hz and an jitter tj <; 1 fs while integrating the phase noise at offset frequencies between 2 kHz and 30 MHz.

Comparison of the Jitter Performance of different Photonic Sampling Techniques

The jitter performance of different photonic sampling techniques are investigated. Two basic sampling mechanisms are identified. Depending on analog-to-digital converter (ADC) architectures, the sampling instant is defined either by a time instant at the rising edge of the detected pulses or by their center of mass. A generalized noise model is introduced and used for performance analysis. It is shown that using the center of mass of optical pulses for the sampling process is about one order of magnitude more precise in time than using a time instant at the rising edge. But the incThe jitter performance of different photonic sampling techniques are investigated. Two basic sampling mechanisms are identified. Depending on analog-to-digital converter (ADC) architectures, the sampling instant is defined either by a time instant at the rising edge of the detected pulses or by their center of mass. A generalized noise model is introduced and used for performance analysis. It is shown that using the center of mass of optical pulses for the sampling process is about one order of magnitude more precise in time than using a time instant at the rising edge. But the increased timing precision of down to few fs is accompanied by a higher amplitude uncertainty decreasing the photonic ADC resolution to ≈ 9 effective number of bits.reased timing precision of down to few fs is accompanied by a higher amplitude uncertainty decreasing the photonic ADC resolution to ≈ 9 effective number of bits.

BiCMOS silicon photonics platform for fabrication of high-bandwidth electronic-photonic integrated circuits

Photonic BiCMOS is a novel technology for fabricating electronic-photonic integrated circuits. Broadband silicon photonics devices such as germanium photodiodes and depletion type Mach-Zehnder modulators were monolithically integrated in a high performance SiGe BiCMOS baseline process. Integration aspects and examples of demonstrator circuits shall be reviewed.

Timing jitter of optical clock distribution induced by photodetection

Lower limit of the timing jitter in an optical clock distribution network due to shot and thermal noise using a realistic photo detector model is derived and its dependence on received energy is analyzed.

A monolithically integrated, optically clocked 10 GS/s sampler with a bandwidth of >30 GHz and a jitter of <30 fs in photonic SiGe BiCMOS technology

This paper presents an optically clocked 10 GS/s-sampler monolithically integrated in a photonic 0.25 μm SiGe-BiCMOS technology, which uses an ultra-stable optical pulse train generated by a hybrid mode-locked laser to sample an electrical signal. The integrated circuit includes optical waveguides, as well as a grating coupler, Germanium photodiodes with a bandwidth of >50 GHz, and an integrate-and-dump sampler. Experimental results demonstrate an analog bandwidth exceeding 30 GHz, a jitter of <30 fs, as well as a THD of <-33 dB over the entire bandwidth, and a SNR of 35.3 dB.