Crossing Total Occlusions Using a Hydraulic Pressure Wave: Development of the Catheter.

With the ongoing miniaturization of surgical instruments, the ability to apply large forces on tissues for resection becomes challenging and the risk of buckling becomes more real. In an effort to allow for high force application in slender instruments, in this study, we have investigated using a hydraulic pressure wave (COMSOL model) and developed an innovative 5F cardiac catheter ( = 1,000 mm) that allows for applying high forces up to 9.0 ± 0.

Flexible impulse transfer using a Newton's Cradle-inspired catheter: A feasibility study.

A major challenge during minimally invasive surgery is transfer of high forces through small, flexible instruments, such as needles and catheters, because of their low buckling resistance. In this study, we determined the feasibility of using a Newton's Cradle-inspired catheter (patented) to transfer high-force impulses. Exerting a high-force impulse on the tissue increases the critical buckling load and can prevent buckling.

Actuation profiles to form Zernike shapes with a thermal active mirror.

In EUV lithography, the absorption of EUV light causes wavefront distortion that deteriorates the imaging process. An adaptive optics system has been developed ["Adaptive optics to counteract thermal aberrations," Ph.D.

Validation of separated source frequency delivery for a fiber-coupled heterodyne displacement interferometer.

The use of optical fibers presents several advantages with respect to free-space optical transport regarding source-frequency delivery to individual heterodyne interferometers. Unfortunately, fiber delivery to individual coaxial heterodyne interferometers leads to an increase of (periodic) nonlinearity in the measurement, because transporting coaxial frequencies through one optical fiber leads to frequency mixing. Coaxial beams thus require delivery via free-space transportation methods.

Heterodyne displacement interferometer, insensitive for input polarization.

Periodic nonlinearity (PNL) in displacement interferometers is a systematic error source that limits measurement accuracy. The PNL of coaxial heterodyne interferometers is highly influenced by the polarization state and orientation of the source frequencies. In this Letter, we investigate this error source and discuss two interferometer designs, designed at TU Delft, that showed very low levels of PNL when subjected to any polarization state and/or polarization orientation.

Relative optical wavefront measurement in displacement measuring interferometer systems with sub-nm precision.

Many error sources can affect the accuracy of displacement measuring interferometer systems. In heterodyne interferometry two laser source frequencies constitute the finally detected wavefront. When the wavefronts of these source frequencies are non-ideal and one of them walks off the detector, the shape of the detected wavefront will vary.

Fiber-coupled displacement interferometry without periodic nonlinearity.

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.

Frequency stabilized three mode HeNe laser using nonlinear optical phenomena.

Accurate and traceable length metrology is employed by laser frequency stabilization. This paper describes a laser frequency stabilization technique as a secondary standard with a fractional frequency stability of 5.2x10(-10) with 2 mW of power, suitable for practical applications.

High resolution heterodyne interferometer without detectable periodic nonlinearity.

A high resolution heterodyne laser interferometer without periodic nonlinearity for linear displacement measurements is described. It uses two spatially separated beams with an offset frequency and an interferometer configuration which has no mixed states to prevent polarization mixing. In this research, a simple interferometer configuration for both retroreflector and plane mirror targets which are both applicable to industrial applications was developed.

Balanced interferometric system for stability measurements.

We describe two different, double-sided interferometer designs for measuring material stability. Both designs are balanced interferometers where the only optical path difference is the sample and the reference beams are located within the interferometer. One interferometer is a double-pass design, whereas the other is a single-pass system.

Simple heterodyne laser interferometer with subnanometer periodic errors.

We describe a simple heterodyne laser interferometer that has subnanometer periodic errors and is applicable to industrial fields. Two spatially separated beams can reduce the periodic errors, and the use of a right-angle prism makes the optical configuration much simpler than previous interferometers. Moreover, the optical resolution can be enhanced by a factor of 2, because the phase change direction is opposite between reference and measurement signals.