Martin Schell - IEEE Xplore Author Profile

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We analyze the system performance of a large bandwidth photonic THz transmitter based on a WR3 coupled photodiode. Employing probabilistic constellation shaping (PCS) alongside a 64-QAM base constellation, we achieve net data rates of up to 76.8 Gbit/s at 32 GBd. The system's performance is evaluated across various symbol rates and shaping entropies, with bit-error rates (BER) analyzed in relation...Show More
We present a fiber-coupled terahertz (THz) time-domain spectrometer with InGaAs photoconductive membranes (PCM) antennas on silicon as emitter and receiver. With these novel antennas we achieve a very high peak dynamic range of 115 dB and a record bandwidth of 10 THz. This represents an increase of 3.5 THz compared to state-of-the art photoconductive antennas (PCAs), which are restricted by THz ab...Show More
We present the first photonic integrated terahertz spectrometer that is able to cover the tuning bandwidth of state-of-the-art continuous wave (cw) terahertz (THz) antennas. The dedicated photonic integrated circuit (PIC) based on two widely tunable sampled grating DBR (SG-DBR) lasers allows for the generation of up to 5 THz optical difference frequency for THz spectroscopy. With an integrated pha...Show More
We present a novel waveguide-integrated photoconductive antenna as heterodyne receiver for THz wireless links. The receiver features 20 dB higher conversion gain and 4 GHz higher IF bandwidth compared to the best top-illuminated photoconductive heterodyne receiver demonstrated so far. With this detector, we are able to extend the current data rate records for full photonic THz links by a factor of...Show More
Optoelectronic continuous-wave THz generation by photomixing is an established tool for table-top spectrometers inside and outside of scientific laboratories. We present newly developed emitters based on ultrafast PIN photodiodes featuring 3 dB overall increased output power. At frequencies beyond 3 THz, the output power is up to >18 dB higher due to the reduced substrate thickness, i.e., internal...Show More
We present sparse sensing with only four terahertz (THz) frequencies enabling fast THz measurement at 1 kHz measurement rate. This is based on a novel method for amplitude and phase determination in homodyne terahertz (THz) spectrometers. Our technique utilizes direct frequency modulation of a distributed feedback laser to precisely measure phase without the need for moving parts or additional pha...Show More
Terahertz (THz) time-domain spectroscopy (TDS) offers considerable potential for a wide range of industrial applications, including thickness determination and defect identification through imaging. Fiber-coupled THz TDS systems are particularly promising due to their flexible and robust operation in a variety of environments. However, increasing the THz power of these systems remains a critical c...Show More
Complex coupled distributed feedback (DFB) lasers and sampled grating distributed Bragg reflector (SGDBR) lasers under optical injection locking are investigated to determine lowest noise operation. A noise reduction (frequency and intensity combined) of up to 15 dB was measured utilizing detuned optical injection locking at the relaxation oscillation frequency. Furthermore, 4 dB improvement in fr...Show More
A novel 16×4 crossing-free waveguide routing network on four layers of polymer-based stacked waveguides is presented. The design combines in-plane passive waveguide devices with vertical multimode interference couplers (1×1 3D MMIs) to connect two adjacent waveguide layers. The 16×4 multilayer waveguide routing network (MWRN) is fabricated using multilayer deposition and standard UV contact lithog...Show More
This article highlights recent developments in high-speed photodiodes and their role in efficient data transmission. Design considerations and state-of-the-art performances are presented for waveguide-integrated and vertically illuminated photodiodes. PIN, Uni-traveling carrier (UTC), and avalanche photodiodes (APD) are reviewed in terms of sensitivity and 3-dB bandwidth. Further, a metric for a p...Show More
We present a novel flexible interconnection technology for sub-THz packaging applications. The interconnect consists of a 50 Ω-transmission line, fabricated on polyimide substrate with a single Au conductor layer. It also provides an under-bump-metallization (UBM) to enable flip-chip bonding. A transmission loss of less than 1.7 dB/mm and a reflection coefficient lower than -17 dB at 220 GHz have ...Show More
A lab-on-a-chip multichannel sensing platform for biomedical analysis based on optical silicon nitride (SiNx) microring-resonators (MRR) was established. The resonators were surface functionalized and finally combined with a microfluidic chamber for validation using an avidin-biotin ligand-binding assay. The results with a limit of detection (LOD) of 2.3∙10-5 and a mean intra-assay coefficient of ...Show More
Fiber-coupled terahertz (THz) time-domain spectrometers (TDS) are versatile tools that are used extensively in academia and industry. Here, we compare two different THz sources with the aim to reach the largest spectral bandwidth: A DSTMS crystal and a novel photoconductive membrane emitter. With both sources, we demonstrate record bandwidths around 10 THz. At the same time, the photoconductive em...Show More
We present the first photonic integrated phase control for continuous wave (cw) terahertz (THz) spectroscopy. The dedicated photonic integrated circuit (PIC) allows for amplitude and phase detection without the need of any moving parts like fiber stretchers or free space optics. Our experimental evaluation shows equal performance of the PIC compared to a state-of-the-art fiber-based system. Furthe...Show More
We present continuous-wave terahertz (cw THz) detectors with record high dynamic range of up to 125 dB at 0.12 THz, for the first time. These outstanding detectors are based on rhodium-doped InGaAs. In addition, the rhodium-doped detectors are compared with iron-doped detectors in terms of their electronic, dynamic and THz properties. Overall, the rhodium-doped devices show superior performance, w...Show More
We investigate indium gallium arsenide samples with various doping levels using terahertz (THz) time-domain reflectometry and transmissometry in the near- and far-field. The samples have been grown on indium phosphide substrates by molecular beam epitaxy under different growth conditions yielding a wide range of electrical properties including resistances from 101 to 106 Ohm/sq. We compare THz mea...Show More
We present a fiber-coupled transceiver for terahertz (THz) time-domain spectroscopy in reflection geometry. The monolithically integrated transceiver is based on rhodium (Rh) doped In0.53Ga0.47As (InGaAs:Rh) grown by molecular beam epitaxy, combining emitter and receiver on the same photoconductive chip. A record THz power for transceivers of 106 μW, a maximum spectral bandwidth of 6.5 THz and a p...Show More
Optoelectronic generation and detection of THz signals are well-established in THz-sensing. Beyond sensing, there is great potential for using these photonic devices for wireless communication at (sub-)terahertz carrier frequencies. While photodiode-based emitters are often used in broadband wireless links, receivers based on photoconductive antennas are rarely found due to their limited electrica...Show More
We present a guard-ring free InGaAs/InP single photon avalanche diode with 20 μm diameter for the optical C-band. At 225 K, 25.6 μs dead time and 17% detection efficiency, the dark count rate is 3 kcps with 0.5% afterpulsing probability. This corresponds to a quantum bit error rate of about 1.2% for 625 MHz timebin-phase BB84 QKD over 125 km.Show More
We demonstrate 56 GBaud PAM-4 transmission by using a high-speed waveguide avalanche photodiode (WG APD) and an electro absorption modulated laser (EML). Compared to a PIN photodiode, the WG APD reduces the power budget in a B2B setup by 6 dB.Show More
We demonstrate an EML-array for up to 4x200 Gb/s PAM4 modulation at 45°C. Its single MQW layer stack design allows for low-cost fabrication. The device is optimized for equal performance over four LAN-WDM wavelength channels.Show More
A microwave photonic RF comb generator is presented by combining an fs-pulse laser and a high-speed broadband photodetector module. The subsystem generates pulses with a FWHM of 5.8 ps and a flat RF comb up to 140 GHz. Furthermore, the capability of pulse distribution over fiber is investigated. The dispersion of the single mode fiber is managed by using an optical bandpass filter, because reducin...Show More
We present the introduction of high-speed phase modulators based on the quantum-confined Stark effect to the generic InP foundry platform at Fraunhofer HHI. An overview of the technological integration of the high-speed phase Mach-Zehnder modulators (MZM) to the existing generic foundry process is described. In addition, an electro-optical behavioral model for the high speed MZM, which gives insig...Show More
Optoelectronic technology is expected to be the cornerstone of sub-THz communication systems, enabling access to and use of the vast frequency resources found in this portion of the spectrum. In this work we demonstrate a photonics-enabled sub-THz wireless link operating in real-time settings, using a PIN-PD-based THz emitter, and a THz receiver based on an ultra-fast photoconductor. The real-time...Show More
We demonstrate an EML for 200 Gb/s PAM4 modulation at uncooled conditions. The device has an identical MQW layer stack for the DFB, EAM and SOA section, which allows a simple fabrication process. The EML is designed for balanced performance from 20°C to 85°C.Show More