Laser diode based THz-TDS system with 133 dB peak signal-to-noise ratio at 100 GHz.

Terahertz time-domain spectroscopy (THz-TDS) has emerged as a powerful and versatile tool in various scientific fields. These include-among others-imaging, material characterization, and layer thickness measurements. While THz-TDS has achieved significant success in research environments, the high cost and bulky nature of most systems have hindered widespread commercialization of this technology.

Repetition frequency tunability and stability of BH InAs/InP QD and InGaAsP/InP QW two-section mode-locked laser diodes.

Ultra-high repetition rate (UHRR) mode-locked laser diodes (MLLD) have shown promising results for applications based on optical sampling such as asynchronous optical sampling (ASOPS), optical sampling by repetition-rate tuning (OSBERT), and optical ranging. Important metrics to consider are the repetition frequency (RF) and the RF linewidth. Here, we compare two monolithically integrated MLLDs.

Group velocity dispersion in high-performance BH InAs/InP QD and InGaAsP/InP QW two-section passively mode-locked lasers.

High-performance buried heterostructure (BH) C-band InAs/InP quantum dot (QD) and L-band InGaAsP/InP quantum well (QW) two-section passively mode-locked lasers (MLLs) are investigated. From the irregularity of the longitudinal mode spacing in the comb spectra, we confirm that under stable passive mode locking, both devices have strong group velocity dispersion (GVD) and corresponding GVD-induced pulse width broadening. After compensation with anomalous dispersion fibers (SMF-28), short pulse trains with sub-ps pulse widths are achieved for both devices.

Ultra-High Repetition Rate Terahertz Time-Domain Spectroscopy for Micrometer Layer Thickness Measurement.

Terahertz time-domain spectroscopy systems driven by monolithic mode-locked laser diodes (MLLDs) exhibit bandwidths exceeding 1 THz and a peak dynamic range that can compete with other state-of-the-art systems. Their main difference compared to fiber-laser-driven systems is their ultra-high repetition rate of typically dozens of GHz. This makes them interesting for applications where the length of the terahertz path may not be precisely known and it enables the use of a very short and potentially fast optical delay unit.

Wideband Beam Steering Concept for Terahertz Time-Domain Spectroscopy: Theoretical Considerations.

Photonic true time delay beam steering on the transmitter side of terahertz time-domain spectroscopy (THz TDS) systems requires many wideband variable optical delay elements and an array of coherently driven emitters operating over a huge bandwidth. We propose driving the THz TDS system with a monolithic mode-locked laser diode (MLLD). This allows us to use integrated optical ring resonators (ORRs) whose periodic group delay spectra are aligned with the spectrum of the MLLD as variable optical delay elements.

Repeatability of material parameter extraction of liquids from transmission terahertz time-domain measurements.

Recently, many research groups worldwide have reported on the THz properties of liquids. Often these parameters, i.e.

System-theoretical modeling of terahertz time-domain spectroscopy with ultra-high repetition rate mode-locked lasers.

Terahertz time-domain spectroscopy (THz-TDS) systems based on ultra-high repetition rate mode-locked laser diodes (MLLDs) and semiconductor photomixers show great potential in terms of a wide bandwidth, fast acquisition speed, compactness, and robustness. They come at a much lower total cost than systems using femtosecond fiber lasers. However, to date, there is no adequate mathematical description of THz-TDS using a MLLD.

Terahertz Beam Steering Concept Based on a MEMS-Reconfigurable Reflection Grating.

With an increasing number of applications of terahertz systems in industrial fields and communications, terahertz beamforming and beam steering techniques are required for high-speed, large-area scanning. As a promising means for beam steering, micro-electro-mechanical system (MEMS)-based reflection gratings have been successfully implemented for terahertz beam control. So far, the diffraction grating efficiency is relatively low due to the limited vertical displacement range of the reflectors.

Application of a robotic THz imaging system for sub-surface analysis of ancient human remains.

We used a robotic-based THz imaging system to investigate the sub-surface structure of an artificially mummified ancient Egyptian human left hand. The results obtained are compared to the results of a conventional CT and a micro-CT scan. Using such a robotic THz system promises new insights into the sub-surface structure of human remains.

Enhancing the performance of THz quasi time-domain spectroscopy systems by low duty cycle laser operation.

We investigate the performance of terahertz (THz) quasi time-domain systems (QTDS) driven by electrically pulsed multi-mode laser diodes operating at 659 nm. We show that at the same average output power, a reduced duty cycle considerably increases the obtained bandwidth. In the presented experiment, the high frequency performance is improved by 50 dB/THz.

Effect of Atrial Fibrillation and Mitral Valve Gradients on Response to Percutaneous Mitral Valve Repair With the MitraClip System.

Both pre-existing atrial fibrillation (AF) and mitral valve pressure gradients (MVPG) created by MitraClip implantation have demonstrated predictive power for unfavorable outcomes. Therefore, we aimed to assess the impact of MVPG following MitraClip on outcomes in patients with and without AF. A total of 200 patients who underwent MitraClip implantation in our institution were enrolled.

Acute reverse annular remodeling during MitraClip therapy predicts improved clinical outcome in heart failure patients: a 3D echocardiography study.

Background: Transcatheter mitral valve repair (TMVR) has been shown to have acute effects on mitral valve geometry in patients with functional mitral regurgitation (FMR). This study investigates the impact of MitraClip therapy-induced annular remodeling on clinical outcome and mitral regurgitation in heart failure patients.

Methods: TMVR was performed successfully in 45 patients with FMR.

Terahertz quasi time-domain spectroscopy based on telecom technology for 1550 nm.

We present a fiber-coupled terahertz quasi time-domain spectroscopy system driven by a laser with a central wavelength of 1550 nm. By using a commercially available multimode laser diode in combination with state-of-the-art continuous wave antennas, a bandwidth of more than 1.8 THz is achieved.

Femtosecond semiconductor laser system with resonator-internal dispersion adaptation.

We present a femtosecond laser diode system that is capable of autonomously adjusting itself to compensate for the external dispersion in an arbitrary application. The laser system contains a spatial light modulator inside the cavity which is controlled by an evolutionary algorithm in order to allow for phase and amplitude shaping of the laser emission. The cavity-internal dispersion control is shown to be much more efficient than an external control with a pulse shaper.

Periodic sampling errors in terahertz time-domain measurements.

An extensive investigation of the origin and the impact of periodic sampling errors of terahertz time-domain spectroscopy systems is given. We present experimental findings and compare them to a theoretical model which is developed in this work. Special attention is given to the influence on the extraction of the refractive index from measurements.

Deep sedation Vs. general anesthesia in 232 patients undergoing percutaneous mitral valve repair using the MitraClip system.

Objectives: To investigate in a series of 232 patients whether the MitraClip procedure can be performed safely using deep sedation (DS) without general anesthesia (GA).

Background: Transcatheter mitral valve repair using the MitraClip system is a safe and effective therapy for severe mitral regurgitation (MR) in patients who are at high operative risk or are unsuitable for surgery. For these patients, avoidance of GA might be beneficial.

Left Atrial and Left Ventricular Function and Remodeling Following Percutaneous Mitral Valve Repair.

Background: Mitral regurgitation causes left atrial (LA) and left ventricular (LV) dysfunction, dilatation, and remodeling. Following percutaneous mitral valve repair (PMVR) using the MitraClip® approach, reverse cardiac remodeling is desirable. To date, the influence of PMVR on LA and segmental LV function and remodeling has not been investigated in detail.

Optimal C-arm angulation during transcatheter aortic valve replacement: Accuracy of a rotational C-arm computed tomography based three dimensional heart model.

Aim: To investigate the accuracy of a rotational C-arm CT-based 3D heart model to predict an optimal C-arm configuration during transcatheter aortic valve replacement (TAVR).

Methods: Rotational C-arm CT (RCT) under rapid ventricular pacing was performed in 57 consecutive patients with severe aortic stenosis as part of the pre-procedural cardiac catheterization. With prototype software each RCT data set was segmented using a 3D heart model.

Development of a multi-channel time-to-space terahertz spectrometer.

We present a compact sensor head for a multi-channel terahertz (THz) spectroscopy system. A THz pulse generated by a photoconductive antenna is split into spatially separated sub-pulses, which have different transit times. The time-dependent order of the sub-pulses can be translated into a spatial resolution.

Hybrid Imaging in the Catheter Laboratory: Real-time Fusion of Echocardiography and Fluoroscopy During Percutaneous Structural Heart Disease Interventions.

Percutaneous catheter-based techniques for the treatment of structural heart disease are becoming more complex, and current imaging techniques have limitations: while fluoroscopy gives poor visualisation of cardiac anatomical structures, echocardiography is limited in its ability to detect the position of catheters and devices. The EchoNavigator® (Philips) live image guidance tool is a novel system that integrates real-time echocardiography with fluoroscopic X-ray imaging, optimising the guidance and positioning of devices. Use of the EchoNavigator system facilitates improved understanding of anatomical structures while showing enhanced visualisation of catheter and device movements.

Comparison of Manual and Automated Preprocedural Segmentation Tools to Predict the Annulus Plane Angulation and C-Arm Positioning for Transcatheter Aortic Valve Replacement.

Background: Preprocedural manual multi-slice-CT-segmentation tools (MSCT-ST) define the gold standard for planning transcatheter aortic valve replacement (TAVR). They are able to predict the perpendicular line of the aortic annulus (PPL) and to indicate the corresponding C-arm angulation (CAA). Fully automated planning-tools and their clinical relevance have not been systematically evaluated in a real world setting so far.

Percutaneous Mitral Valve Repair in Mitral Regurgitation Reduces Cell-Free Hemoglobin and Improves Endothelial Function.

Background And Objective: Endothelial dysfunction is predictive for cardiovascular events and may be caused by decreased bioavailability of nitric oxide (NO). NO is scavenged by cell-free hemoglobin with reduction of bioavailable NO up to 70% subsequently deteriorating vascular function. While patients with mitral regurgitation (MR) suffer from an impaired prognosis, mechanisms relating to coexistent vascular dysfunctions have not been described yet.

Left Atrial Appendage Closure Guided by Integrated Echocardiography and Fluoroscopy Imaging Reduces Radiation Exposure.

Aims: To investigate whether percutaneous left atrial appendage (LAA) closure guided by automated real-time integration of 2D-/3D-transesophageal echocardiography (TEE) and fluoroscopy imaging results in decreased radiation exposure.

Methods And Results: In this open-label single-center study LAA closure (AmplatzerTM Cardiac Plug) was performed in 34 consecutive patients (8 women; 73.1±8.