Characterization of field-effect mobility at optical frequency by microring resonators

A novel characterization method is proposed to extract the optical frequency field-effect mobility ($μop,FE$) of transparent conductive oxide (TCO) materials by a tunable silicon microring resonator with a heterogeneously integrated titanium-doped indium oxide$(ITiO)/SiO2/silicon$metal–oxide–semiconductor (MOS) capacitor. By operating the microring in the accumulation mode, the quality factor and resonance wavelength shift are measured and subsequently used to derive the$μop,FE$in the ultra-thin accumulation layer. Experimental results demonstrate that the$μop,FE$of ITiO increases from 25.3 to$38.4 cm2⋅V−1⋅s−1$with increasing gate voltages, which shows a similar trend as that at the electric frequency.

Authors:
; ; ;
Publication Date:
NSF-PAR ID:
10219707
Journal Name:
Photonics Research
Volume:
9
Issue:
4
Page Range or eLocation-ID:
Article No. 615
ISSN:
2327-9125
Publisher:
Optical Society of America
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2. Materials with strong second-order ($χ<#comment/>(2)$) optical nonlinearity, especially lithium niobate, play a critical role in building optical parametric oscillators (OPOs). However, chip-scale integration of low-loss$χ<#comment/>(2)$materials remains challenging and limits the threshold power of on-chip$χ<#comment/>(2)$OPO. Here we report an on-chip lithium niobate optical parametric oscillator at the telecom wavelengths using a quasi-phase-matched, high-quality microring resonator, whose threshold power ($∼<#comment/>30µ<#comment/>W$) is 400 times lower than that in previous$χ<#comment/>(2)$integrated photonics platforms. An on-chip power conversion efficiency of 11% is obtained from pump to signal and idler fields at a pump power of 93 µW. The OPO wavelength tuning is achieved by varying the pump frequency and chip temperature. With the lowest power threshold among all on-chip OPOs demonstrated so far, as well as advantages including high conversion efficiency, flexibility in quasi-phase-matching, and device scalability, the thin-film lithium niobate OPO opens new opportunities for chip-based tunable classical and quantum light sources and provides a potential platform for realizing photonic neural networks.
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4. Properly interpreting lidar (light detection and ranging) signal for characterizing particle distribution relies on a key parameter,$χ<#comment/>p(π<#comment/>)$, which relates the particulate volume scattering function (VSF) at 180° ($β<#comment/>p(π<#comment/>)$) that a lidar measures to the particulate backscattering coefficient ($bbp$). However,$χ<#comment/>p(π<#comment/>)$has been seldom studied due to challenges in accurately measuring$β<#comment/>p(π<#comment/>)$and$bbp$concurrently in the field. In this study,$χ<#comment/>p(π<#comment/>)$, as well as its spectral dependence, was re-examined using the VSFs measuredin situat high angular resolution in a wide range of waters.$β<#comment/>p(π<#comment/>)$, while not measured directly, was inferred using a physically sound, well-validated VSF-inversion method. The effects of particle shape and internal structure on the inversion were tested using three inversion kernels consisting of phase functions computed for particles that are assumed as homogenous sphere, homogenous asymmetric hexahedra, or coated sphere. The reconstructed VSFs using any of the three kernels agreed well with the measured VSFs with a mean percentage difference$<<#comment/>5%<#comment/>$at scattering angles$<<#comment/>170∘<#comment/>$. At angles immediately near or equal to 180°, the reconstructeddepends strongly on the inversion kernel.$χ<#comment/>p(π<#comment/>)$derived with the sphere kernels was smaller than those derived with the hexahedra kernel but consistent with$χ<#comment/>p(π<#comment/>)$estimated directly from high-spectral-resolution lidar andin situbackscattering sensor. The possible explanation was that the sphere kernels are able to capture the backscattering enhancement feature near 180° that has been observed for marine particles.$χ<#comment/>p(π<#comment/>)$derived using the coated sphere kernel was generally lower than those derived with the homogenous sphere kernel. Our result suggests that$χ<#comment/>p(π<#comment/>)$is sensitive to the shape and internal structure of particles and significant error could be induced if a fixed value of$χ<#comment/>p(π<#comment/>)$is to be used to interpret lidar signal collected in different waters. On the other hand,$χ<#comment/>p(π<#comment/>)$showed little spectral dependence.
5. The use of multispectral geostationary satellites to study aquatic ecosystems improves the temporal frequency of observations and mitigates cloud obstruction, but no operational capability presently exists for the coastal and inland waters of the United States. The Advanced Baseline Imager (ABI) on the current iteration of the Geostationary Operational Environmental Satellites, termed the$R$Series (GOES-R), however, provides sub-hourly imagery and the opportunity to overcome this deficit and to leverage a large repository of existing GOES-R aquatic observations. The fulfillment of this opportunity is assessed herein using a spectrally simplified, two-channel aquatic algorithm consistent with ABI wave bands to estimate the diffuse attenuation coefficient for photosynthetically available radiation,$Kd(PAR)$. First, anin situABI dataset was synthesized using a globally representative dataset of above- and in-water radiometric data products. Values of$Kd(PAR)$were estimated by fitting the ratio of the shortest and longest visible wave bands from thein situABI dataset to coincident,in situ$Kd(PAR)$data products. The algorithm was evaluated based on an iterative cross-validation analysis in which 80% of the dataset was randomly partitioned for fitting and the remaining 20%more »