Displacement interferometry is widely used for accurately characterizing nanometer and subnanometer displacements in many applications. In many modern systems, fiber delivery is desired to limit optical alignment and remove heat sources from the system, but fiber delivery can exacerbate common interferometric measurement problems, such as periodic nonlinearity, and account for fiber-induced drift. In this Letter, we describe a novel, general Joo-type interferometer that inherently has an optical reference after any fiber delivery that eliminates fiber-induced drift. This interferometer demonstrated no detectable periodic nonlinarity in both free-space and fiber-delivered variants.@en

In this article we describe a new and easy way to implement a measurement tool that can vary the size of the measurement area and the phase resolution without the need for changing hardware. It can evaluate wavefronts at high repeatability before as well as after an interferometer without a decrease in measurement performance and it can be applied for both homodyne and heterodyne interferometer systems. The wavefront measurement method presented is an interferometer itself, where a sample of a small area in the wavefront is taken by an optical multimode fiber and compared with a reference. It allows for measuring phase differences with a resolution of ~90µrad or ~10pm (¿=633nm) at a repeatability better than 1nm over one week. 3D wavefront reconstructions are obtained by combining multiple measurements.@en

This paper describes the design of a compact, lightweight CT-compatible, drill-press that is designed to be used in either a hand-held or stand-alone mode to assist with percutaneous bone based interventions. Previous medical drilling tools that have been developed have a metal structure and typically have one actuator for advancing the drill (feed) and another for rotating it (speed). After defining the device's functional requirements and specifications, a deterministic design process was followed to generate several design concepts that were then evaluated based on their ability to satisfy the functional requirements. A final concept that uses a custom screw-spline to achieve helical motion of a shaft that is attached to a standard orthopedic drill was selected for prototyping. The design uses a single actuator to drive both the screw and spline nuts through two different gear ratios, resulting in a fixed ratio between the feed and speed. Apart from the motor which is placed away from the central drill axis, the device is largely made from plastic materials. A custom experimental setup was developed that enabled drilling into bone inside a CT scanner to be examined. Results showed that the device was successfully able to penetrate thick cortical bone and that its structure did not appreciably distort the medical images. Keywords: medical robotics, computed tomography, X-ray, drill, interventional radiology, bone@en

IC-production processes are among the most demanding ones when it comes to high-precision positioning. For most systems performing long-range measurements, sub-micrometer resolutions and displacement accuracies over long strokes are common. Now the semiconductor industry pushes its demands to the extreme with the advent of Extreme Ultraviolet Lithography (EUV). Accelerations and velocities are high in these systems (120 m/s² for the reticle and 30 m/s² for the wafer stage), whereas the required position measurements have to be performed with resolutions and accuracies in the order of sub-nanometers over a measurement range of a few decimeters. Delft University of Technology (TU Delft) has introduced a new heterodyne interferometer concept using spatially separated optical input beams to address this challenge.@en

Displacement interferometers are widely used in precision engineering and metrology applications. For multi-axis systems, free space delivery of the optical beams requires high tolerance pointing stability and couples the source to the interferometer location. Fiber delivery is desired to decouple the source and interferometer but configurations which have to be used for this, contribute typical errors such as periodic nonlinearity. In this paper, we describe a fiber-coupled Joo-type interferometer. Spatial separation of the input beams in this type of interferometer eliminate periodic nonlinearities. This is contrasted by typical heterodyne interferometer systems which have two orthogonal, coaxial beams with a difference frequency. We present the interferometer design, discuss the fiber deployment, and compare free-space and fiber-coupled versions. The results indicate that fiberinduced disturbances are rejected as theory predicts and no periodic nonlinearity was detected.@en

The Earth's magnetosphere is formed as a consequence of the interaction between the planet's magnetic field and the solar wind, a continuous plasma stream from the Sun. A number of different solar wind phenomena have been studied over the past forty years with the intention of understandingand forcasting solar behavior and space weather. In particular, Earth-bound interplanetary coronal mass ejections (CMEs) can significantly disturb the Earth's magnetosphere for a short time and cause geomagnetic storms. We present a mission concept consisting of six spacecraft that are equally spaced in a heliocentric orbit at 0.72 AU. These spacecraft will monitor the plasma properties, the magnetic field's orientation and magnitude, and the 3D-propagation trajectory of CMEs heading for Earth. The primary objective of this mission is to increase space weather forecasting time by means of a near real-time information service, that is based upon in-situ and remote measurements of the CME properties. The mission secondary objective is the improvement of scientific space weather models. In-situ measurements are performed using a Solar Wind Analyzer instrumentation package and flux gate magnetometers. For remote measurements, coronagraphs are employed. The proposed instruments originate from other space missions with the intention to reduce mission costs and to streamline the mission design process. Communication with the six identical spacecraft is realized via a deep space network consisting of six ground stations. This network provides an information service that is in uninterrupted contact with the spacecraft, allowing for continuos space weather monitoring. A dedicated data processing center will handle all the data, and forward the processed data to the SSA Space Weather Coordination Center. This organization will inform the general public through a space weather forecast. The data processing center will additionally archive the data for the scientific community. This concept mission allows for major advances in space weather forecasting and the scientific modeling of space weather. @en

Heterodyne interferometry is a widely applied technique for length and displacement measurements in precision systems. Free-space optical beam delivery couples the source directly to the interferometer location. Conversely, fiber delivery is desired to decouple the source and interferometer. Drawbacks to using fibers are either time consuming alignment (PM fiber) or time varying polarization output (MM fiber). Jones matrices were used to analyze Joo-type interferometers to simulate the effects of using MM fiber inputs. The results showed loss of interference at some instances from the rotating polarization states. Measurements with a MM fiber coupled interferometer showed minimal polarization rotation and no interference loss.@en

We show the latest progress towards establishing a solid-state, metropolitan quantum link, consisting of two remote Nitrogen Vacancy (NV)-centers and a central measurement station. The entanglement is generated by converting single emitted photons to the same frequency in the telecom L-band, guiding them to a central beamsplitter, where a joint Bell-state measurement projects the NV-centre spins in an entangled state.@en