A hybrid system for simultaneous velocity and distance measurements in dynamic experiments.

The accurate measurement of an object's motion requires knowledge of both its position and its velocity. The commonly used photonic Doppler velocimetry and broadband laser ranging techniques are ideal for conducting simultaneous dynamic experiments. Instead of employing two distinct measurement systems, we developed a hybrid system that can simultaneously measure velocity and distance in dynamic experiments.

Dual-channel Faraday rotation measurement for pulsed magnetic field.

The immunity and survivability in a strong electromagnetic environment make the Faraday Rotation (FR) method irreplaceable for measuring pulsed magnetic fields. We present a dual-channel FR method that achieves more stable and precise measurement and more applicable magnetic field types than the conventional FR method. By splitting the modulated light into two components, the ratio of the two components is transformed into a tangent function with two analyzers at a relative 45°.

A multi-spot laser induced breakdown spectroscopy system based on diffraction beam splitter.

A quick simultaneous multispot laser induced breakdown spectroscopy (LIBS) system has been proposed. The basic idea is to combine the Diffraction Beam Splitter (DBS) with the linear-to-linear fiber bundle. The DBS divided the incident laser beam into five sub-beams, and then, a lens focused the incident sub-beam to produce a plasma array, where the distance between the neighbor subplasma was constant and the plasma emission was imaged on the fiber bundle.

Influence of probe pressure on the pulsatile diffuse correlation spectroscopy blood flow signal on the forearm and forehead regions.

In a pilot study of 11 healthy adults (24 to 39 years, all male), we characterize the influence of external probe pressure on optical diffuse correlation spectroscopy (DCS) measurements of pulsatile blood flow obtained on the forearm and forehead. For external probe pressure control, a hand inflatable air balloon is inserted between the tissue and an elastic strap. The air balloon is sequentially inflated to achieve a wide range of external probe pressures between 20 and 250 mmHg on the forearm and forehead, which are measured with a flexible pressure sensor underneath the probe.

Multi-reference broadband laser ranging to increase the measuring range.

Broadband laser ranging (BLR) is an appropriate method to obtain absolute distance in dynamic experiments. In this article, we first analyze the performance limit for BLR and indicate that the measuring range can be hardly increased while keeping the distance or time resolution unchanged. Then, multi-reference BLR is proposed, which can break this limit and greatly increase the measuring range.

Bi-fiber quasi-axis probe for photonic Doppler velocimetry for shock physics experiments.

Photonic Doppler velocimetry (PDV) has become a major domain velocity measurement technique for shock physics experiments. In this study, we propose and validate a bi-fiber quasi-axis probe for PDV that consists of a multimode source fiber and a single-mode detection fiber. This structure makes the received light by the probe totally reflected or scattered from the target, and, therefore, is free from the influence of unwanted return light.

Ultrasensitive specific terahertz sensor based on tunable plasmon induced transparency of a graphene micro-ribbon array structure.

We proposed an ultrasensitive specific terahertz sensor consisting of two sets of graphene micro-ribbon with different widths. The interference between the plasmon resonances of the wide and narrow graphene micro-ribbons gives rise to the plasmon induced transparency (PIT) effect and enables ultrasensitive sensing in terahertz region. The performances of the PIT sensor have been analyzed in detail considering the thickness and refractive index sensing applications using full wave electromagnetic simulations.

Purified frequency modulation of a quantum cascade laser with an all-optical approach.

Purified frequency modulation (FM) is demonstrated in a standard middle-infrared quantum cascade laser by illuminating its front facet with two near-infrared (NIR) lasers. A 2 mW laser at 1550 nm is utilized to modulate the amplitude and frequency of a quantum cascade laser, and the associated amplitude modulation (AM) is suppressed by a 1.85 mW laser at 850 nm.

All-optical coaxial framing photography using parallel coherence shutters.

An all-optical framing camera has been developed to obtain serial images of high temporal and spatial resolution with identical spatial benchmark, identical temporal benchmark, and identical chromatic benchmark in a single shot. A train of laser probe pulses with identical wavelength coaxially illuminate the target and form sequentially timed images by means of parallel coherence shutters. A coherence shutter only selects one of the probe pulses to form a nonmultiplexing hologram.

Time-resolved single-shot terahertz time-domain spectroscopy for ultrafast irreversible processes.

Pulsed terahertz spectroscopy is suitable for spectroscopic diagnostics of ultrafast events. However, the study of irreversible or single shot ultrafast events requires ability to record transient properties at multiple time delays, i.e.

X-ray backlighting of imploding aluminium liners on PTS facility.

The x-ray backlighting systems, including a 1.865 keV (Si He line) spherically bent crystal imaging system and an ∼8.3 keV (Cu He line) point-projection imaging system, newly fielded on the Primary Test Stand facility are introduced and its preliminary experimental results in radiography of the aluminium (Al) liners with seeded sinusoidal perturbations are presented.

Research on the fiber Bragg grating sensor for the shock stress measurement.

A fiber Bragg grating (FBG) sensor with an unbalanced Mach-Zehnder fiber interferometer for the shock stress measurement is proposed and demonstrated. An analysis relationship between the shock stress and the central reflection wavelength shift of the FBG is firstly derived. In this sensor, the optical path difference of the unbalanced Mach-Zehnder fiber interferometer is ~3.

K-shell emission x-ray imaging of Z-pinch plasmas with a pinhole and a logarithmic spiral crystal.

An in-chamber, mini x-ray imaging instrument employs a pinhole and a logarithmic spiral crystal has been developed for obtaining K-shell line images of the imploding aluminum wire array on the "Yang" accelerator. The logarithmic spiral crystal acts as a monochromator and a non-dispersive mirror that reflects the pinhole image to a x-ray film detector with a very narrow photon energy bandwidth (<1 eV, mainly determined by the width of rocking curve of the crystal). Two imaging configurations with the use of Quartz (10 ̅10) crystal and Mica (002) crystal are designed, respectively, to image the Al Ly(α2) line (1727.

Analysis of photonic Doppler velocimetry data based on the continuous wavelet transform.

The short time Fourier transform (STFT) cannot resolve rapid velocity changes in most photonic Doppler velocimetry (PDV) data. A practical analysis method based on the continuous wavelet transform (CWT) was presented to overcome this difficulty. The adaptability of the wavelet family predicates that the continuous wavelet transform uses an adaptive time window to estimate the instantaneous frequency of signals.

Research on the magneto-optic current sensor for high-current pulses.

A new magneto-optic current sensor with a dual-orthogonal configuration is proposed and demonstrated, which can resolve the problem which value of high-current pulses is ambiguous from the Faraday rotation in the conventional magneto-optic current sensor. In this dual-orthogonal configuration, the transmission axis of the polarizer makes two given angles, which are 0 degrees and 45 degrees , with the orientation of the s-polarized lights of two polarizing cube beam splitters. If the intrinsic linear birefringence of the sensing element is one-fourth less than the Faraday rotation generated from the high-current pulse, the measurement current influenced by it can be ignored and four outputs of the magneto-optic current sensor are in quadrature.

Four-point bisensitivity velocity interferometer with a multireflection etalon.

A four-point bisensitivity velocity interferometer system for any reflector (VISAR) with a renovative delay etalon is proposed and demonstrated. In this interferometer, we introduce a new film-coating strategy to accurately measure small velocity with relatively short and cheap etalon. Laser pointing to the etalon is split into two beams with different incident angles with each beam going through the etalon in different path.