Marcel Zeiler

Modeling TID Effects in Mach-Zehnder Interferometer Silicon Modulator for HL-LHC Data Transmission Applications

High-speed Mach-Zehnder interferometer silicon modulators were exposed to a total ionizing dose of 1.3 MGy, levels comparable to the worst radiation levels for a tracking detector after 10 years of operation at the High-Luminosity LHC, show a sensitivity to ionizing radiation after exposure to a dose of a few hundred kGy. A physical model to describe the effect of ionizing radiation on the modulators has been developed and is used to predict whether a more radiation-hard modulator can be designed to survive the harshest radiation environments expected at the HL-LHC.

Neutron and X-ray irradiation of silicon based Mach-Zehnder modulators

We report on our recent investigation into the potential for using silicon-based Mach-Zehnder modulators in the harshest radiation environments of the High-Luminosity LHC. The effect of ionizing and non-ionizing radiation on the performance of the devices have been investigated using the 20 MeV neutron beam line at the Cyclotron Resource Centre in Louvain-La-Neuve and the X-ray irradiation facility in the CERN PH department. The devices were exposed to a total fluence and ionizing dose of 1.2×1015 n cm−2 and 1.3 MGy respectively.

A system-level model for high-speed, radiation-hard optical links in HEP experiments based on silicon Mach-Zehnder modulators

Silicon Mach-Zehnder modulators have been shown to be relatively insensitive to displacement damage beyond a 1-MeV-equivalent neutron fluence of 3⋅1016n/cm2. Recent investigations on optimized device designs have also led to a high resistance against total ionizing dose levels of above 1 MGy. Such devices could potentially replace electrical and/or optical links close to the particle interaction points in future high energy physics experiments. Since they require an external continuous-wave light source, radiation-hard optical links based on silicon Mach-Zehnder modulators need to have a different system design when compared to existing directly modulated laser-based optical links. 10 Gb/s eye diagrams of irradiated Mach-Zehnder modulators were measured. The outcomes demonstrate the suitability for using these components in harsh radiation environments. A proposal for the implementation of silicon Mach-Zehnder modulators in CERNs particle detectors was developed and a model to calculate the system performance is presented. The optical power budget and the electrical power dissipation of the proposed link is compared to that of the upcoming Versatile Link system that will be installed in 2018.

Data Acquisition at CERN: A Future Challenge

How did the universe look in the first moments after the Big Bang? Why does matter dominate over antimatter? What are the fundamental particles that make up the world as we see it today? To find answers to those and similar questions, the European Organization for Nuclear Research (CERN) is operating the worlds largest particle accelerator, the Large Hadron Collider (LHC). The LHC accelerates protons to a velocity close to the speed of light and makes hundreds of them collide. The circumstances shortly after those collisions are representative to the universes conditions only moments after the Big Bang. By analyzing thousands of such collisions, a steps can be made toward answering the previous questions.

Radiation Damage in Silicon Photonic Mach–Zehnder Modulators and Photodiodes

Radiation-hard optical links are the backbone of read-out systems in high-energy physics (HEP) experiments at CERN. The optical components must withstand large doses of radiation and strong magnetic fields and provide high data rates. Radiation hardness is one of the requirements that become more demanding with every new generation of HEP experiment. Previous studies have shown that vertical cavity surface emitting lasers, on which the current optical links are based, will not be able to withstand the expected radiation levels in the innermost regions of future HEP experiments. Silicon photonics (SiPh) is currently being investigated as a promising alternative technology to address this challenge. We irradiated SiPh Mach-Zehnder modulators (MZMs) with different design parameters to evaluate their resistance against ionizing radiation. We confirm that SiPh MZMs with a conventional design do not show a phase shift degradation when exposed to a 20-MeV neutron fluence of

Radiation hardness evaluation and phase shift enhancement through ionizing radiation in silicon Mach-Zehnder modulators

3\cdot 10^{16}~{\rm n/cm^{2}}

Comparison of the radiation hardness of silicon Mach-Zehnder modulators for different DC bias voltages

. We further demonstrate that custom-designed MZMs with shallow etch optical waveguides and high doping concentrations in their p-n junctions exhibit a strongly improved radiation hardness over devices with a conventional design when irradiated with X-rays. We also found that MZMs withstood higher radiation levels when they were irradiated at a low temperature. In contrast, larger reverse biases during irradiation led to a faster device degradation. Simulations indicate that a pinch-off of holes is responsible for the device degradation. Photodiodes (PDs) were also tested for their radiation hardness as they are needed in silicon photonic transceivers. X-ray irradiation of building-block germanium-silicon PDs showed that they were not significantly affected.

Effect of Radiation on a Mach–Zehnder Interferometer Silicon Modulator for HL-LHC Data Transmission Applications

Data acquisition systems in High Energy Physics (HEP) experiments rely on tens of thousands of radiation hard optical links based on high data rate, low power transmitters which also have to be able to withstand high levels of different types of radiation. Radiation hardness is one of the requirements that becomes more demanding with every new generation of experiment. Previous studies have shown that there is currently no qualified technology for optical transmitters able to withstand operation in the innermost regions of upgraded LHC experiments at CERN. Silicon photonic Mach-Zehnder Modulators (MZMs) are being investigated as one of the promising technologies to address this challenge. We designed MZMs with different design parameters and exposed them to ionizing radiation in order to assess how their performance changes. We demonstrate that the etch depth of the MZM waveguides and the doping concentration in the waveguides strongly impact the response of the MZMs. In particular, a shallow etch depth and increased doping concentrations help to mitigate the detrimental effects of ionizing radiation. MZMs fabricated with these design parameters are found to show a post-irradiation phase shift enhancement compared to the pre-irradiation values. The improved radiation resistance is high enough that such devices could potentially be installed in future HEP experiments or in other fields of application sensitive to radiation.

Design of Si-photonic structures to evaluate their radiation hardness dependence on design parameters

Radiation hard optical links are the backbone of read-out systems in high-energy physics experiments at CERN. The optical components have to withstand large doses of radiation and provide high data rates. Silicon photonics is currently being considered a promising technology to replace electrical and optical links in future experiments. It has already been demonstrated that integrated silicon Mach-Zehnder modulators can withstand a high neutron fluence and large total ionizing doses. Before read-out systems based on these components can be taken into consideration, it has to be determined how biasing affects their radiation hardness. For this reason we prepared bonded and fiber-pigtailed prototypes and irradiated them with x-rays. We found that under reverse-bias the radiation hardness of the tested components is reduced in comparison to un-biased samples. However, we were able to show that one device type can withstand the radiation without phase shift degradation up to 1 MGy despite the accelerated degradation due to biasing.