Our group works has extensive experience with measurements on integrated optics devices. The lasers that we use are typically tunable semiconductor lasers that operate at telecom wavelengths (around 1550 nm), but other wavelengths are also used. The laser light is sent onto the chips using a fiber array that is positioned above the grating couplers of the device under test. Locating the device and optimizing the position can be done fully automated, enabling rapid, reproducible characterization of the devices. This is aided with sweep lasers, low-noise detectors and fast data acquisition systems. Besides such optical measurements, also electrical signals can be applied to the devices via DC and microwave probes, for example to excite mechanical resonators, or to program an integrated quantum circuit.
The measurements on mechanical systems are typically done in vacuum, to minimize the damping due to the surrounding air. For these, dedicated vacuum chambers with in-situ sample positioning are available, both for on-chip and for 2d optomechanics. Both types of mechanical devices operate at high frequencies (100 kHz - 10 GHz) which requires spectrum and network analyzers that can reach these frequencies. For feedback experiments, a fast lockin amplifier with multi-frequency and real-time options is available.
Our integrated quantum optics chips contain superconducting single-photon detectors which have to be cooled to temperatures close to the absolute zero. This is done in dedicated cryostats with electrical and fiber access. To measure such detectors, fast oscilloscopes and low noise sources are available.
Making state-of-the art chips using advanced nanofabrication techniques is a major part of our research. This is carried out in close collaboration with the Walther Meißner Institute for Low Temperature Research (WMI), the Walter Schottky Institute (WSI), and its Center for Nanotechnology and Nanomaterials (ZNN).
We operate the new reactive-ion etcher (RIE) with an inductivly-coupled plasma (ICP) in the ZNN cleanroom. The Oxford PlasmaPro 80 can be operated in RIE and ICP mode, has a temperature controlled sample platen (0 - 80 oC) and helium backing. The following gasses are installed: CF4, CHF3, SF6, C4F8, O2, Ar, Cl2 and BCl3. The system can in principle etch wafers up to 100 mm, but is designed to work with small samples. Since the etcher is used to create high-quality optomechanical structures and low-loss optical waveguides, not all samples are allowed. Click here for more information.
This system has been purchases with support from the Nanosystems Initiative Munich (NIM) and TUM-IAS.
Thin film measurements are important in the fabrication of our chips. The Quantum Technology Lab operates the Filmetrics F20 microscopic reflectometer in the ZNN cleanroom. With both a halogen as well as a D2 light source it can determine the individual thicknesses of a stack of transparent layers with a resolution down to about a nanometer. The microscope allows to perform these measurements locally on a chip with a spotsize of about 7 micrometer. The system can be used by ZNN users after a short training.
This system has been purchases with support from the MCQST