VCSEL intrinsic response extraction using T-Matrix formalism

We present a new method to remove the parasitics contribution to the VCSEL chip response, in order to obtain the intrinsic S21 behavior. The on-chip VCSEL is defined as two cascaded two-port subsystems representing the electrical access and the VCSEL optical cavity respectively. S11 and S21 parameters measurements are carried-out using a probe station to characterize the chip response. An electrical equivalent circuit defining the behavior of the electrical access is combined with T-Matrix formalism to remove the parasitics contribution from the measured S21 response. Results allow us to determine the intrinsic 3-dB bandwidth of the VCSEL

Long wavelength VCSEL-by-VCSEL optical injection-Locking

VCSEL-by-VCSEL optical injection-locking to obtain high cut-off frequencies of 1.3 μm Vertical-Cavity Surface-Emitting Lasers (VCSELs) is demonstrated. A detailed physical explanation of the underlying mechanism is presented. VCSELs from the same wafer have been used in a master-follower configuration. Two probe stations are used in this experiment to power-up two VCSELs simultaneously. Polarization insensibility of the injection-locking is demonstrated and a novel architecture is proposed to achieve cut-off frequency doubling. For the first time a high cut-off frequency is achieved through optically injection-locking the satellite mode of a long wavelength VCSEL. Injection-locking spectra with variable injection-powers and variable detuning values have been obtained and methods have been proposed to obtain high cut-off and/or resonance frequencies. A rate-equation based model is presented. Simulations have been carried out using this model. Finally, a linear increases in the follower VCSEL cut-off frequency with increasing injected-power is demonstrated by using a semiconductor optical amplifier

Efficient optoelectronic de-embedding for VCSEL intrinsic response extraction

In this present work, we propose a new method to remove the parasitics contribution to the VCSEL chip response,in order to obtain the intrinsic transmission behavior. It has been observed that the S11 reflection coefficient of the chip is only due to the electrical access to the chip composed by the transmission line and cavity contacts. This allows us to decompose the chip into two cascaded subsystems representing the electrical access and the optical cavity respectively. An equivalent electrical circuit is developed for the electrical access behavior and, combined with the transfer matrix formalism, it becomes possible to remove the parasitics contribution from the measured S21 response. In this way, the intrinsic 3-dB bandwidth of the VCSEL can be determined

1.3μm single-mode VCSEL-by-VCSEL optical injection-locking for enhanced microwave performance

Microwave performance of 1.3μm optically injection-locked single-mode VCSELs functioning at room temperature is presented. The experiment has been performed using two identical unpackaged VCSELs on two separate probe-stations. Three-fold increase in the 3-dB cut-off frequency of S21 spectra have been observed under VCSEL-by-VCSEL optical injection-locking

The impact of membrane protein diffusion on GPCR signaling

This research was carried out as part of the Math-+ excellence cluster (DFG EXC 2046, Project A01-11 [HHB, PA]) and was partially funded by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) through the following grants: Project 421152132 SFB1423 subproject C03 (PA), SFB 1470 subproject A01 (PA) and SFB 1114/2 (SW).Spatiotemporal signal shaping in G protein-coupled receptor (GPCR) signaling is now a well-established and accepted notion to explain how signaling specificity can be achieved by a superfamily sharing only a handful of downstream second messengers. Dozens of Gs-coupled GPCR signals ultimately converge on the production of cAMP, a ubiquitous second messenger. This idea is almost always framed in terms of local concentrations, the differences in which are maintained by means of spatial separation. However, given the dynamic nature of the reaction-diffusion processes at hand, the dynamics, in particular the local diffusional properties of the receptors and their cognate G proteins, are also important. By combining some first principle considerations, simulated data, and experimental data of the receptors diffusing on the membranes of living cells, we offer a short perspective on the modulatory role of local membrane diffusion in regulating GPCR-mediated cell signaling. Our analysis points to a diffusion-limited regime where the effective production rate of activated G protein scales linearly with the receptor–G protein complex’s relative diffusion rate and to an interesting role played by the membrane geometry in modulating the efficiency of coupling.Publisher PDFPeer reviewe

Shedding light on the D1-like receptors : a fluorescence-based toolbox for visualization of the D1 and D5 receptors

Funding: Universitat de Barcelona; Fonds der Chemischen Industrie. Grant Number: 661688; University of Regensburg graduate school “Receptor Dynamics: Emerging Paradigms for Novel Drugs. Grant Number: K-BM-2013-247; Elite Network of Bavaria Deutsche Forschungsgemeinschaft. Grant Numbers: 421152132, SFB1423, SFB1470; Spanish MCIN/AEI/10.13039/501100011033. Grant Number: PID2021-126600OB−I00; European Union Next Generation EU/PRTR.Dopamine D1-like receptors are the most abundant type of dopamine receptors in the central nervous system and, even after decades of discovery, still highly interesting for the study of neurological diseases. We herein describe the synthesis of a new set of fluorescent ligands, structurally derived from D1R antagonist SCH-23390 and labeled with two different fluorescent dyes, as tool compounds for the visualization of D1-like receptors. Pharmacological characterization in radioligand binding studies identified UR-NR435 (25) as a high-affinity ligand for D1-like receptors (pKi (D1R) = 8.34, pKi (D5R) = 7.62) with excellent selectivity towards D2-like receptors. Compound 25 proved to be a neutral antagonist at the D1R and D5R in a Gs heterotrimer dissociation assay, an important feature to avoid receptor internalization and degradation when working with whole cells. The neutral antagonist 25 displayed rapid association and complete dissociation to the D1R in kinetic binding studies using confocal microscopy verifying its applicability for fluorescence microscopy. Moreover, molecular brightness studies determined a single-digit nanomolar binding affinity of the ligand, which was in good agreement with radioligand binding data. For this reason, this fluorescent ligand is a useful tool for a sophisticated characterization of native D1 receptors in a variety of experimental setups.Publisher PDFPeer reviewe

Shedding Light on the D1‐Like Receptors: A Fluorescence‐Based Toolbox for Visualization of the D1 and D5 Receptors

Dopamine D1-like receptors are the most abundant type of dopamine receptors in the central nervous system and, even after decades of discovery, still highly interesting for the study of neurological diseases. We herein describe the synthesis of a new set of fluorescent ligands, structurally derived from D1R antagonist SCH-23390 and labeled with two different fluorescent dyes, as tool compounds for the visualization of D1-like receptors. Pharmacological characterization in radioligand binding studies identified UR-NR435 (25) as a high-affinity ligand for D1-like receptors (pKi (D1R)=8.34, pKi (D5R)=7.62) with excellent selectivity towards D2-like receptors. Compound 25 proved to be a neutral antagonist at the D1R and D5R in a Gs heterotrimer dissociation assay, an important feature to avoid receptor internalization and degradation when working with whole cells. The neutral antagonist 25 displayed rapid association and complete dissociation to the D1R in kinetic binding studies using confocal microscopy verifying its applicability for fluorescence microscopy. Moreover, molecular brightness studies determined a single-digit nanomolar binding affinity of the ligand, which was in good agreement with radioligand binding data. For this reason, this fluorescent ligand is a useful tool for a sophisticated characterization of native D1 receptors in a variety of experimental setups

Fluorescent Tools for the Imaging of Dopamine D2‐Like Receptors

The family of dopamine D2-like receptors represents an interesting target for a variety of neurological diseases, e. g. Parkinson's disease (PD), addiction, or schizophrenia. In this study we describe the synthesis of a new set of fluorescent ligands as tools for visualization of dopamine D2-like receptors. Pharmacological characterization in radioligand binding studies identified UR-MN212 (20) as a high-affinity ligand for D2-like receptors (pKi (D2longR)=8.24, pKi (D3R)=8.58, pKi (D4R)=7.78) with decent selectivity towards D1-like receptors. Compound 20 is a neutral antagonist in a Go1 activation assay at the D2longR, D3R, and D4R, which is an important feature for studies using whole cells. The neutral antagonist 20, equipped with a 5-TAMRA dye, displayed rapid association to the D2longR in binding studies using confocal microscopy demonstrating its suitability for fluorescence microscopy. Furthermore, in molecular brightness studies, the ligand's binding affinity could be determined in a single-digit nanomolar range that was in good agreement with radioligand binding data. Therefore, the fluorescent compound can be used for quantitative characterization of native D2-like receptors in a broad variety of experimental setups