The THz Photonics Group is dedicated to integrated photonics and nonlinear optical effects like stimulated Brillouin scattering. We are interested in all kinds of integrated photonics, but our focus is mainly directed to ultra-broadband photonic signal processing in the THz range for communication systems, microwave photonics and photonic sensors.
Head of the Group
Prof. Dr. rer. nat. Thomas Schneider
Dr.-Ing. Stefan Preußler
Ranjan Das, Ph.D.
Cheng Feng, M.Sc.
Younus Mandalawi, M.Sc.
Janosch Meier, M. Sc.
Arijit Misra, M.Sc.
Jaffar Kadum, M.Sc.
Karanveer Singh, M.Sc.
NyPhE - Nyquist Silicon Photonics Engine
Silicon photonics opens up the possibility of co-integrating highly complex photonic and electronic functionalities on a single substrate while simultaneously producing large quantities at low cost. The aim of the project is to realize an integrated 400 Gbit/s transceiver with the help of a signal transmission based on Nyquist pulses, which enables the bandwidth of the input signals to be multiplied. In addition to the optical transmitters and receivers, the chip also includes the electronic components for driving the modulators, for predistortion and for amplifying the electrical signals. The result is a low-cost, highly integrated transceiver that can be flexibly positioned in a standardized connector or on a circuit board.
The conversion from digital to analog signals (DAC) is one of the most important basic functions of signal generation, limited by the speed of the electronics. This limit can be overcome easily by the use of optical technologies. The aim of the project is to develop a photonic DAC concept based on the generation and temporal interleaving of broadband, sinc-shaped Nyquist pulses. With the BiCMOS technology of the IHP a fully integrated photonic DAC chip will be realized, which reaches a multiple of the bandwidth of today's electronic systems. The research project is being carried out jointly with the University of Paderborn and funded by the German Research Foundation (DFG) within the priority program SPP 2111 Electron-Photonic Integrated Systems for Ultrafast Signal Processing.
Meteracom - Metrology for THz Communications
In information technology, data transfer rates are rising steadily as the need for fast wireless data communication is also growing rapidly. In order to reach transmission speeds of 100 gigabits per second and higher, a new approach in communications technology is needed. This topic is the subject of the research group "Metrology for THz Communications". The focus is on communication technology with very high data rates for the still untouched terahertz frequency range (THz) above 300 GHz. Terabit per second could be transmitted in this frequency range in the future. However, it faces today's communication technology with enormous challenges. The research group Meteracom is working on the metrology for the THz communication systems and will, among other things, design measurement methods that help to predict the performance of THz communication in real environments.
Optical Sampling without Optical Pulse Source
Sampling is the first step to convert analog into digital signals (ADC) and therefore one of the basic concepts of modern communication. For sampling an analog time signal gets multiplied with a pulse train, so that the pulses are weighted with signal values at certain times. Afterwards, the heights of the pulses will be converted to digital values to build up the digital signal. The main bottleneck of this concept is the speed of nowadays electronics. This can be easily overcome by optical technologies. Within our project we are using Mach-Zehnder modulators driven with electrical multitone signals, leading to optical combs in the frequency domain and periodical sinc sequences in the time domain. These sinc sequences are especially advantageous due to their mathematical properties and allow an almost ideal sampling for bandwidth limited signals. Furthermore, this method based on Mach-Zehnder modulators enables a sampling without an optical pulse source like a mode-locked laser, so that it can be realized integrated on optical chips, enabling manifold higher bandwidths with respect to nowadays electronics.
Fiber Sensors - Brillouin Optical Time Domain Analysis
Distributed sensors can retrieve sensing information with a low spatial resolution along kilometers of length. Especially fiber optic sensor can offer an attractive solution for many industrial applications like health monitoring of large structures such as oil and gas pipeline leak detection and long high-tension transmission lines and railways. The most promising Brillouin optical time-domain analysis utilizes stimulated Brillouin scattering, which is done by a local interaction of an intense pump pulse with a weak counter-propagating CW probe signal. By recording the gain experienced by the probe at each location in dependence on the frequency-shift, the temperature or strain distribution along the fiber can be measured. Our aim is to develop optical sensing systems that can meet the industrial measurement requirement in term of long-range deployment, measurement accuracy and high spatial resolution.
Silicon-on-Insulator Frequency Combs
The precision provided by high-quality frequency-comb sources is of great interest for numerous applications including spectroscopy, precision frequency metrology and optical clocks. Besides several complex methods for comb generation, various micro resonator structures have been proposed recently. The main aspect of the project is the investigation of integrated comb sources with actively and fast controllable comb parameters, reaching a minimum free spectral range of 10 GHz and a maximum bandwidth of 10 THz at center wavelengths in the telecom range. Since different applications from the microwave up to the optical range are envisaged, two new designs for comb structures, namely a ring based and a modulator-in-a-cavity structure, implemented on a mix between silicon Nitride and Silicon are utilized.
iBONT - Integrated Blocks for Optical Sinc-Shaped Nyquist Pulse Transmission
Nyquist pulses enable zero inter-symbol interference, which makes them very attractive for communication systems since they maximize the spectral efficiency of data transmission. Almost all pulse shaping methods reported so far have remained rather complex, they cannot be integrated and do not led to ideal sinc pulses. The aim of this project is the investigation of compact and simple optical setups for the generation of close-to perfect sinc-shaped Nyquist pulse sequences of arbitrary bandwidth up to 300 GHz, duration and repetition rates up to 50 times the pulse bandwidth, with potential for future device-level integration. Additionally, the concept will be implemented in a chalcogenide-on-SOI platform and incorporated with up to 8 WDM channels, leading to transmission experiments of TDM-WDM Nyquist super-channels based on sinc-shaped pulses.
Within the research line Quantum and Nanometrology (QUANOMET), researchers in Braunschweig and Hannover are working on the cross-thematic focus on NanoLight as well as the main focuses of NanoParticles andQuantum Techniques.