arXiv subjects

Ting Ji

Publications and source records attributed to Ting Ji.

4 recordsLinked to original sources

arXiv2026

A Simple and Powerful Diagnostic Test for Binary Choice Models

Conventional binary choice models, such as probit and logit, impose thin-tailed errors, and that tail determines whether the parameters of a binary choice model can be estimated at the regular rate. We test the restriction on observables, asking whether the conditional choice probability decays at a polynomial rate in a covariate. Identification of tail heaviness requires no independence, no linear index, and no homoskedasticity. The test is simple to implement and attains nearly the point-optimal power envelope among invariant tests. An application to firm innovation decisions rejects the thin tail.

econ.EM↗

arXiv2021

High-responsivity, High-detectivity Photomultiplication Organic Photodetector Realized by a Metal-Insulator-Semiconductor Tunneling Junction

Organic photodetectors (OPDs) possess bright prospects in applications of medical imaging and wearable electronics due to the advantages such as low cost, good biocompatibility, and good flexibility. Photomultiplication OPDs (PM-OPDs) enabled by the trap-assisted carrier tunneling injection effect exhibit external quantum efficiencies far greater than unity, thus the acquired responsivities are extremely high. However, the reported PM-OPDs with high responsivity performances are all accompanied by high dark currents due to the introduction of carrier traps, which inevitably results in inferior detectivities. In this work, we modify a P3HT:PCBM donor-rich PM-OPD by introducing an atomically thin Al2O3 interfacial layer through the ALD technique, obtaining a high responsivity of 8294 A/W and high detectivity of 6.76*10^14 Jones, simultaneously, both of which are among the highest reported for bulk heterojunction PM-OPDs. Ascribed to the introduction of the atomically thin Al2O3 layer, the metal-insulator-semiconductor (MIS) tunneling junction is formed, which brings forward a suppressed dark current along with an increased amounts of holes tunneling under forward bias. Meanwhile, the weak light detection limit of the modified PM-OPD within the linear response range reaches the level of nW/cm2. Based on the proposed PM-OPD, a proof-of-concept image sensor with 26*26 pixels is demonstrated, which can respond to both ultraviolet light and visible light. The PM-OPD based sensor arrays can find broad applications for medical imaging, wearable electronics, etc.

physics.app-ph↗

arXiv2016

Tungsten based Anisotropic Metamaterial as an Ultra-broadband Absorber

The trapped rainbow effect has been mostly found on tapered anisotropic metamaterials (MMs) made of low loss noble metals, such as gold, silver, etc. In this work, we demonstrate that an anisotropic MM waveguide made of high loss metal tungsten can also support the trapped rainbow effect similar to the noble metal based structure. We show theoretically that an array of tungsten/germanium anisotropic nano-cones placed on top of a reflective substrate can absorb light at the wavelength range from 0.3 micrometer to 9 micrometer with an average absorption efficiency approaching 98%. It is found that the excitation of multiple orders of slow-light resonant modes is responsible for the efficient absorption at wavelengths longer than 2 micrometer, and the anti-reflection effect of tapered lossy material gives rise to the near perfect absorption at shorter wavelengths. The absorption spectrum suffers a small dip at around 4.2 micrometer where the first order and second order slow-light modes get overlapped, but we can get rid of this dip if the absorption band edge at long wavelength range is reduced down to 5 micrometer. The parametrical study reflects that the absorption bandwidth is mainly determined by the filling ratio of tungsten as well as the bottom diameter of the nano-cones and the interaction between neighboring nano-cones is quite weak. Our proposal has some potential applications in the areas of solar energy harvesting and thermal emitters.

physics.optics↗

arXiv2013

Efficient multiband absorber based on 1D periodic metal-dielectric photonic crystals with a reflective substrate

We propose an efficient multiband absorber comprising a truncated one-dimensional periodic metal-dielectric photonic crystal and a reflective substrate. The reflective substrate is actually an optically thick metallic film. Such a planar device is easier to fabricate compared with the absorbers with complicated shapes. For a 4-unit cell device, all of the four absorption peaks can be optimized with efficiencies higher than 95%. Moreover, those absorption peaks are insensitive to both polarization and incident angle. The influences of the geometrical parameters along with the refractive index of the dielectric on the device performance are discussed as well. Furthermore, it is found that the number of absorption peaks within each photonic band exactly corresponds to the number of the unit cells because the truncated photonic crystal lattices have the function of selecting resonant modes. It is also displayed that the total absorption efficiency gradually increases when there are more metal-dielectric unit cells placing on top of the metallic substrate. Our work is expected to have some potential applications in the areas of solar energy harvesting and thermal emission tailoring.

physics.optics↗