Field Calibration of the Optical Properties of Pedestrian Targets in Autonomous Emergency Braking Tests Using a Three-Dimensional Multi-Faceted Standard Body.

To address the growing need for field calibration of the optical properties of pedestrian targets used in autonomous emergency braking (AEB) tests, a novel three-dimensional multi-faceted standard body (TDMFSB) was developed. A camera-based analytical algorithm was proposed to evaluate the bidirectional reflectance distribution function (BRDF) characteristics of pedestrian targets. Additionally, a field calibration method applied in AEB testing scenarios (CPFAO and CPLA protocols) on one new and one aged typical pedestrian target of the same type revealed a 21% decrease in the BRDF uniformity of the aged target compared to the new one, confirming optical degradation due to repeated "crash-scatter-reassembly" cycles.

Sub-millikelvin-resolved superconducting nanowire single-photon detector operates with sub-pW infrared radiation power.

The noise equivalent temperature difference (NETD) indicates the minimum temperature difference resolvable by using an infrared detector. The lower the NETD, the better the sensor can register small temperature differences. In this work, we proposed a strategy to achieve a high temperature resolution using a superconducting nanowire single-photon detector (SNSPD) with ultra-high sensitivity.

Radiometric calibration of a multiphoton microscope capable of measuring absolute photon flux of single photon sources.

Precise photon flux measurement of single photon sources (SPSs) is essential to the successful application of SPSs. In this work, a novel method, to our knowledge, was proposed for direct measurement of the absolute photon flux of single photon sources with a femtosecond laser multiphoton microscope. A secondary 2-mm-diameter aperture was installed under the microscope objective to define the numerical aperture (NA) of the microscope.

Transmission and reflection cloaking by using a zero-refractive-index photonic crystal in the microwave region.

We propose a rectangular column two-dimensional square lattice photonic crystal to realize zero refractive index. Through analysis of the energy band structure of the photonic crystal structure, the lattice constant and side length of the rectangular columns can be optimized, and the Dirac cone dispersion appears at the center of the Brillouin zone. The Dirac cone is formed by the interaction of a monopolar eigenstate and a dipolar eigenstate to form a triple accidental degenerate state.

Design of two invisibility cloaks using transmissive and reflective metamaterial-based multilayer frame microstructures.

Ultrathin metamaterials provide new possibilities for the realization of cloaking devices because of their ability to control electromagnetic waves. However, applications of metamaterials in cloaking devices have been limited primarily to reflection-type carpet cloaks. Hence, a transmissive free-space cloak was developed using a multilayer frame structure, wherein highly transparent metamaterials were used to guide incident waves into propagating around an object.

Miniaturized integrating sphere light sources based on LEDs for radiance responsivity calibration of optical imaging microscopes.

LED-based integrating sphere light sources (LED-ISLSs) in the size of typical microscope slides were developed to calibrate the radiance responsivity of optical imaging microscopes. Each LED-ISLS consists of a miniaturized integrating sphere with a diameter of 4 mm, an LED chip integrated on a printed circuit board, and a thin circular aperture with a diameter of 1 mm as the exit port. The non-uniformity of the radiant exitance of the LED-ISLSs was evaluated to be 0.

Manipulation of the arbitrary scattering angle based on all-dielectric transmissive Pancharatnam Berry phase coding metasurfaces in the visible range.

In order to improve the transmitted efficiency of the metasurface in the visible range, an all-dielectric Pancharatnam-Berry phase unit structure was proposed. Using these Pancharatnam-Berry phase element particles with different rotation angles, all-dielectric encoding metasurfaces can be constructed. The encoding metasurface connects the physical coding particles with digital coding in digital signal processing.

Measurement of the distance between two parallel precision apertures using time-of-flight method for cryogenic radiometry.

Time-of-flight method was adopted to measure the distance between two parallel precision apertures utilized in a vacuum chamber for cryogenic radiometry. The diameters of the apertures are 9 mm and 8 mm, respectively. A 1550-nm femtosecond pulse laser, a 70-GHz photodetector, and a 30-GHz oscilloscope were used to measure the round-trip flight time difference between the flat front surfaces of the two precision apertures.

Enhancement of bandwidth and angle response of metasurface cloaking through adding antireflective moth-eye-like microstructure.

Ultrathin metasurface provides a completely new path to realize cloaking devices on account of their fascinating ability to control electromagnetic wave. However, the conventional cloaking devices are limited by their narrow bandwidth. To overcome this challenge, we present the realization of ultrabroadband and wide angle metasurface cloaking through high refractive index dielectric layer and antireflective "moth-eye-like" microstructure in this work.

Temporal response of laser power standards with natural convective cooling.

Laser power detectors with natural convective cooling are convenient to use and hence widely applicable in a power range below 150 W. However, the temporal response characteristics of the laser power detectors need to be studied in detail for accurate measurement. The temporal response based on the absolute laser power standards with natural convective cooling is studied through theoretical analysis, numerical simulations, and experimental verifications.

Hidden image recovery using a biased photorefractive crystal in the Fourier plane of an optical imaging system.

Self-diffraction can be induced using a biased photorefractive crystal in the Fourier plane of an imaging system where the light beam intensity is naturally high due to the concentration effect of an optical lens. The spatial frequency spectrum of the output image is proportional to the optical power density distribution in the Fourier plane. A photorefractive crystal with small size can be used and hence an reduced amount of biased voltage is needed to obtain significant diffraction effect in the image plane.

Improvement of measurement uncertainties in laser power detector calibration by convolving with the detector's impulse response function.

For the calibration of thermal type laser power detectors with slow response time, instability of the input laser significantly contributes to the measurement repeatability. A convolution method is adopted to reduce the impact of source instability. The equivalent incident power is calculated by convolving the real-time power input and the detector impulse-response function (IRF).