Simplifying complex fault data for systems-level analysis: Earthquake geology inputs for U.S. NSHM 2023.

As part of the U.S. National Seismic Hazard Model (NSHM) update planned for 2023, two databases were prepared to more completely represent Quaternary-active faulting across the western United States: the NSHM23 fault sections database (FSD) and earthquake geology database (EQGeoDB). In prior iterations of NSHM, fault sections were included only if a field-measurement-derived slip rate was estimated along a given fault. By expanding this inclusion criteria, we were able to assess a larger set of faults for use in NSHM23. The USGS Quaternary Fault and Fold Database served as a guide for assessing possible additions to the NSHM23 FSD. Reevaluating available data from published sources yielded an increase of fault sections from ~650 faults in NSHM18 to ~1,000 faults proposed for use in NSHM23. EQGeoDB, a companion dataset linked to NSHM23 FSD, contains geologic slip rate estimates for fault sections included in FSD. Together, these databases serve as common input data used in deformation modeling, earthquake rupture forecasting, and additional downstream uses in NSHM development.

Tunable Broadband Radiation Generated Via Ultrafast Laser Illumination of an Inductively Charged Superconducting Ring.

An electromagnetic transmitter typically consists of individual components such as a waveguide, antenna, power supply, and an oscillator. In this communication we circumvent complications associated with connecting these individual components and instead combine them into a non-traditional, photonic enabled, compact transmitter device for tunable, ultrawide band (UWB) radiation. This device is a centimeter scale, continuous, thin film superconducting ring supporting a persistent super-current. An ultrafast laser pulse (required) illuminates the ring (either at a point or uniformly around the ring) and perturbs the super-current by the de-pairing and recombination of Cooper pairs. This generates a microwave pulse where both ring and laser pulse geometry dictates the radiated spectrum's shape. The transmitting device is self contained and completely isolated from conductive components that are observed to interfere with the generated signal. A rich spectrum is observed that extends beyond 30 GHz (equipment limited) and illustrates the complex super-current dynamics bridging optical, THz, and microwave wavelengths.

Tunable narrow band difference frequency THz wave generation in DAST via dual seed PPLN OPG.

We report a widely tunable narrowband terahertz (THz) source via difference frequency generation (DFG). A narrowband THz source uses the output of dual seeded periodically poled lithium niobate (PPLN) optical parametric generators (OPG) combined in the nonlinear crystal 4-dimthylamino-N-methyl-4-stilbazolium-tosylate (DAST). We demonstrate a seamlessly tunable THZ output that tunes from 1.5 THz to 27 THz with a minimum bandwidth of 3.1 GHz. The effects of dispersive phase matching, two-photon absorption, and polarization were examined and compared to a power emission model that consisted of the current accepted parameters of DAST.

Experimental verification of sparse frequency linearly frequency modulated ladar signals modeling.

We present the results of an experiment designed to verify the results of a previously published theoretical model that predicts the range resolution and peak-to-side lobe ratio of sparse frequency linearly frequency modulated (SF-LFM) ladar signals. We use two ultra stable diode lasers which are frequency locked and can be current tuned in order to adjust the difference frequency between the two lasers. The results of the experiment verify the previously developed model proving that SF-LFM ladar signals have the ability to increase the range resolution of a ladar system without the need for larger bandwidth modulators. Finally we simulate a target at a range of approximately 150 meters through the use of a fiber optic delay line, and demonstrate the ability of SF-LFM ladar signals to detect a target at range.

Vectorial fiber laser using intracavity axial birefringence.

In this paper we investigate the polarization properties of a fiber laser with an intracavity c-cut calcite crystal that is capable of producing reconfigurable vectorial output modes. Vectorial modes with radial, azimuthal and generalized cylindrical vector polarizations can be generated by translating one lens within the laser cavity. Detailed studies of the mode polarization evolution show that the modes inside the laser cavity can be spatially homogeneously polarized in one section of the cavity while being spatially inhomogeneously polarized in another section of the cavity, which opens the opportunities for many potential new fiber laser design possibilities and applications. Furthermore, more complicated vectorial vortex output modes are also observed by purposefully introducing angular misalignments.

Sparse frequency LFM ladar signals.

Through modeling we explored the possibility of utilizing a sparse frequency linear frequency modulation (LFM) signal for laser radar (ladar) applications. We propose a potential transmit and receive experiment utilizing the superposition of two LFM laser sources with a known difference frequency to provide the necessary segmented bandwidth. Finally we analyzed the signal performance of the proposed system showing that the range resolution of the signal can be improved by two to three times while utilizing the same modulator bandwidth as that of a continuous LFM signal.

Optical characterization of wiregrid micropolarizers designed for infrared imaging polarimetry.

We report the optical characterization of a metal wiregrid micropolarizer array for IR imaging polarimetry. The micropolarizers are designed for operation in the 1.5-5.0 microm band with a specially designed thin SiO(2) layer between the silicon substrate and the wiregrids to improve the performance at the shorter wavelengths. Deep-UV projection lithography is used to fabricate 140-nm-deep wiregrids with a 400 nm period. The extinction ratio and the transmission coefficient are measured with a tunable IR laser. A TM transmission coefficient greater than 70% with an extinction ratio greater than 10(4) is achieved for the midwave-IR region while maintaining an extinction ratio better than 10(2) for the near-IR region above 1.5 microm.

Optical temperature sensor and thermal expansion measurement using a femtosecond micromachined grating in 6H-SiC.

An optical temperature sensor was created using a femtosecond micromachined diffraction grating inside transparent bulk 6H-SiC, and to the best of our knowledge, this is a novel technique of measuring temperature. Other methods of measuring temperature using fiber Bragg gratings have been devised by other groups such as Zhang and Kahrizi [in MEMS, NANO, and Smart Systems (IEEE, 2005)]. This temperature sensor was, to the best of our knowledge, also used for a novel method of measuring the linear and nonlinear coefficients of the thermal expansion of transparent and nontransparent materials by means of the grating first-order diffracted beam. Furthermore the coefficient of thermal expansion of 6H-SiC was measured using this new technique. A He-Ne laser beam was used with the SiC grating to produce a first-order diffracted beam where the change in deflection height was measured as a function of temperature. The grating was micromachined with a 20 microm spacing and has dimensions of approximately 500 microm x 500 microm (l x w) and is roughly 0.5 microm deep into the 6H-SiC bulk. A minimum temperature of 26.7 degrees C and a maximum temperature of 399 degrees C were measured, which gives a DeltaT of 372.3 degrees C. The sensitivity of the technique is DeltaT=5 degrees C. A maximum deflection angle of 1.81 degrees was measured in the first-order diffracted beam. The trend of the deflection with increasing temperature is a nonlinear polynomial of the second-order. This optical SiC thermal sensor has many high-temperature electronic applications such as aircraft turbine and gas tank monitoring for commercial and military applications.

Temperature-dependent refractive index measurements of wafer-shaped InAs and InSb.

An experimental method is introduced to measure the refractive index and its temperature dependence for wafer-shaped infrared materials over a continuous temperature range. Using a combination of Michelson interferometry, Fabry-Perot interferometry, and a temperature-controlled cryostat in a laser micrometer, refractive index values and their temperature coefficients can be measured for any specific temperature within a desired temperature range. Measurements are reported for InAs and InSb for a laser wavelength of 10.59 microm.

Femtosecond micromachining in transparent bulk materials using an anamorphic lens.

A unique anamorphic lens design was applied to a circular 780nm femtosecond laser pulse to transform it into an elliptically shaped beam at focus. This lens was developed to give an alternative method of micromachining bulk transparent materials. The challenge for femtosecond laser processing is to control the nonlinear affect of self-focusing, which can occur when using a fast f-number lens. Once the focused spot is dominated by self-focusing the predicted focused beam becomes a filament inside the bulk, which is an undesirable effect. The anamorphic lens resolves this self-focusing by increasing the numerical aperture (NA) and employing an elliptical beam shape. The anamorphic lens was designed to furnish a 2.5mum by 190mum line at focus. Provided the pulse energy is high enough, transparent bulk material will be damaged with a single femtosecond laser pulse. Damage in this text refers to visual change in the index of refraction as observed under an optical microscope. Using this elliptical shape (or line), grating structures were micro-machined on the surface of SiC bulk transparent substrate. SiC was chosen because it is known for its micromachining difficulty and its crystalline structure. From the lack of self-focusing and using energy that is just above the damage threshold the focused line beam generated from the anamorphic lens grating structures produced a line shape nearly identical to the geometrical approximation. In this paper we discuss a new method of writing gratings (or other types of structures) in bulk transparent materials using a single femtosecond laser pulse. We will investigate the grating structures visually (inspected under an optical microscope) and also by use of an atomic force microscopy (AFM). In addition, we test the grating diffraction efficiency (DE) as a function of grating spacing, d.

Patient preferences for capillary vs. venous INR determination in an anticoagulation clinic: a randomized controlled trial.

BACKGROUND: Patients who are receiving warfarin therapy require frequent blood testing to monitor the intensity of anticoagulation. Although previous studies suggest that capillary blood monitoring of the international normalize ratio (INR) is rapid and reliable, patient preferences for the method of blood drawing have not been investigated. METHODS: We performed a randomized controlled trial of patients attending an anticoagulation clinic in which patients were randomly allocated to undergo capillary or venous INR monitoring. Patient satisfaction with the outpatient visit, pain associated with blood drawing, and time spent in the clinic were assessed for each patient. RESULTS: Sixty patients were studied. Using a 10-point visual analogue scale to quantify patient satisfaction (0-very satisfied; 10-very dissatisfied), patients expressed a strong preference for capillary INR monitoring over venous INR monitoring (1.64 vs. 4.45; P < 0.001). Using a 10-point visual analogue scale to quantify pain with blood sampling (0-no pain; 10-very painful), patients who underwent capillary INR testing had less pain than venous INR testing (0.83 vs. 2.23; P < or = 0.004). Patients spent, on average, 33 fewer minutes in the clinic with capillary INR testing than venous INR testing (P < 0.001). DISCUSSION: Our findings support the routine use of capillary blood testing, using a portable monitor, for the management of patients in outpatient anticoagulation clinics.

Enhanced signal coupling into periodically poled lithium niobate with microlens arrays.

The return signal frequency of an eye-safe ladar system is upconverted from the infrared to the visible through sum-frequency generation by incorporation of periodically poled LiNbO3 into the receiver. A quantitative analysis of the angular acceptance and the quantum efficiency is then presented for a single macroscopic receiver optic and a multiaperture microlens array. Comparing both results, a 6x increase in the receiver field of regard and an 18% increase in beam coupling were realized for the microlens design over the macroscopic system.