Xiang Wang

Optical-fiber interferometer for velocity measurements with picosecond resolution

The conventional Doppler laser-interference velocimeters are made up of traditional optical elements such as lenses and mirrors and will generally restrict its applications in multipoint velocity measurements. By transfering the light from multimode optical fiber to single-mode optical fiber and using the currently available conventional telecommunications elements, the authors have constructed a velocimeter called all-fiber displacement interferometer system for any reflector. The unique interferometer system is only made up of fibers or fiber-coupled components. The viability of this technique is demonstrated by measuring the velocity of an interface moving at velocity of 2133m∕s with 50ps time resolution. In addition, the concept of optical-fiber mode conversion would provide a way to develop various optical-fiber sensors.

A compact all-fiber displacement interferometer for measuring the foil velocity driven by laser.

A compact all-fiber displacement interferometer (AFDI) system, working at 1550 nm, has been developed and tested, and its working fundamentals will be introduced in this letter. In contrast with other models of fiber-optic velocity interferometer system, AFDI adopts a single-mode optic fiber pigtail as the detect head, diameter of which is only 1 mm, to collect directly the reflect laser beam from the moving surface, which makes this instrument have some unique advantages in observing the point movements of a small flyer. Preliminary experiments using this instrument to measure the velocity history of a small aluminum thin foil driven by a nanosecond pulse laser were conducted successfully, the precise velocity history profile deduced from the sharp interference fringes and the nanometer resolution in displacement gives an eloquent proof of its eminent abilities. The field depth (approximately 2 mm) of our AFDI is a little smaller than the DISAR [Weng et al., Appl. Phys. Lett. 89, 111101 (2006)] system, but its compact structure makes it much convenient to operate. Further applications for multipoints velocity history measurements of small targets are under consideration.

New all-fiber velocimeter

A new all-fiber velocity interferometer system for any reflector (AFVISAR) was developed. It was conceived and realized with the purpose of using it as the basic measuring element of a complete system for multiple point velocity measurements. Its main features are that it works at 532nm and partly adopts the multimode optical fiber. The velocimeter consists of only fibers or fiber coupled components and has no optic elements such as optic lenses or reflectors. It is therefore very compact and easy to operate. Unlike the conventional AFVISAR, which uses single-mode optic fiber components, the laser beam in this new interferometer system arrives at and reflects from the target surface through a multimode optical fiber component, and then enters and interferes in a [3×3] single-mode fiber coupler. Its working principle is elaborated on in this article. Preliminary experiments using a split Hopkins pressure bar (SHPB) device show that the new interferometer can successfully measure the velocity profiles of th...

New kind of spectral analysis instrument for measuring time-resolved spectrum of single-pulse light

A new kind of spectral analytical instrument has been developed for measuring pulse time-resolved spectra. In this instrument, a special light beam modulator translates the time-distribution of optical spectra into the space- distribution of light intensity, and then the time-dependent spectra is detected by an ordinary 2D CCD device. The time resolution of 25 microsecond(s) and the wavelength range of 224-824 nm have been attained in the experiment of a Xe flash-lamp emission.

Study on dynamic compression performance of K9 glass with prefabricated defects

We conducted several planar impact experiments to study dynamic compression properties of K9 glass on powder gun using Photon Doppler Velocimetry (PDV) measure system. Samples are prefabricated some internal meso-defects by laser three-dimensional erosion technique before shock loading. Free surface velocities recorded by high temporal-spatial resolution PDV array or multi-point PDV. All these experimental results show some different properties influenced by evolutions of pre-existed internal defects face on free surface velocity profiles. The critical compression strength and dynamic evolution information of pre-existed internal defects can be derived from the experimental results tentatively.