Reflection Amplitude Research Articles

Dual high-Q bound states in the continuum based Fano resonances in bulk WS2 meta-lattice

Abstract Bound states in the continuum (BICs) play a promising role in enhancing light–matter interaction with a high quality (Q) factor in transition metal dichalcogenides (TMDCs). In this work, a structured meta-lattice of bulk tungsten disulfide (WS2), a well-known material of TMDCs, with double high-Q resonances governed by quasi-BIC is presented. Two types of quasi-BIC are exploited simultaneously by rotational and longitudinal asymmetries of WS2 rods, acting as the meta-atoms. These Fano line shaped quasi-BIC resonances have a very high quality factor of 1.6×104 with a reasonable asymmetric parameter of 1%. Although, tuning the asymmetric parameter changes the linewidth of the resonances and the resulting Q-factor, for all values of these parameters the amplitude of reflection remains constant at one. In addition to exploring and analysing two quasi-BICs, strong coupling between exciton and quasi-BICs is illustrated with Rabi splitting of 116.6meV and 54.2meV for rotational and longitudinal asymmetries, respectively. These findings show promise for the development of high-Q photonic devices and applications in polaritonics.

Stratigraphic and Structural Features of The Sinop Basin Close to The Mid Black Sea Ridge Using Multi-Channel Seismic and Multi-Beam Bathymetric Data

Focal mechanism solutions of the earthquakes that occurred in the Black Sea in the last 100 years show that thrust and strike-slip faults are predominantly active in the region. One of these clusters is developing off the coast of Samsun where the submarine Sinop basin is located. In order to investigate the seismic sources of earthquakes in this area, high-resolution multi-channel seismic sections and multi-beam bathymetric data were processed and evaluated. The oldest seismic stratigrafic units (U4) is referred to as acoustic basement with wavy reflectors, while its top is marked by high amplitude reflection indicating an unconformity. This uniconformity is overlain by parallel or less parallel Unit 3 deposits. Upper surface of Unit 2 is marked by an erosional surface which is overlain by the parallel reflector of Unit 1. Unit 1 is the youngest sediments and truncated by Yeşilırmak canyon. Three fault types of different ages were determined. The oldest fault could reach only top of unit 4 has been interpreted as inactive fault. Faults that border the Sinop basin and reach the sea floor by cutting all seismic units are considered in the active fault class. However, the faults that remain within Unit 1 and do not reach the seafloor are considered as faults that are coeval with sedimentation. According to these data, faulting in the Central/Eastern Pontide structural block should be reconsidered in the context of the seismic activity of the region and re-evaluated as an earthquake hazard that will pose a risk in the future.

A dual-frequency reflective coding metasurface achieving independent amplitude-phase control and its application for reflectarray

ABSTRACT This letter proposes a novel dual-frequency reflective coding metasurface (CMS) composed of two types of improved C-shaped resonators. By loading a microstrip line and a ring, the electromagnetic (EM) coupling between the resonators is significantly reduced. Also, the microstrip line helps to improve reflection amplitude in the high band. As a result, the proposed CMS can independently control the amplitude and phase of cross-polarized waves in the frequency ranges of 8.6–9.4 GHz and 16.3–17.1 GHz. Based on this CMS, a bifocal metalens and a reflectarray (RA) antenna operating in the bands are designed, and the latter is fabricated and tested. The measured peak gains of the RA antenna are 21.6 dBi in 9.0 GHz band and 22.7 dBi in 16.8 GHz band. The aperture efficiencies are 30.7% and 22.8%, respectively.

Scattering of Transverse Electric and Transverse Magnetic Waves and Quantum Dynamics Generated by non-Hermitian Hamiltonians

Abstract The study of the scattering of electromagnetic waves by a linear isotropic medium with planar symmetry can be reduced to that of their transverse electric (TE) and transverse magnetic (TM) modes. For situations where the medium consists of parallel homogeneous slabs, one may use the standard transfer matrix technique to address the scattering problem for these modes. We extend the utility of this technique to inhomogeneous permittivity and permeability profiles by proposing a dynamical formulation of the scattering of TE and TM waves in which the transfer matrix for the medium is given in terms of the evolution operator for an effective nonunitary quantum system. This leads to a system of dynamical equations for the reflection and transmission amplitudes. Decoupling these equations, we reduce the solution of the scattering problem for TE and TM modes to that of an initial-value problem for a Riccati equation. We discuss the application of this observation in identifying media that do not reflect TE or TM waves with a given wavenumber and incidence angle.

Application of Ground Penetrating Radar in the Assessment of Aged Roads: Focus On Complex Structures Under Different Weather Conditions

Ground penetrating radar (GPR) has been widely used to assess asphalt and pavement, especially in quality testing for newly constructed roads. However, its usage has been limited in regard to aged roads. Thus, this study focuses on the applicability of GPR to extract diverse information regarding structure, thickness, and various conditions, including the moisture content of an aged road section that has undergone repeated renewals. First, two methods were employed to calculate the thickness and dielectric values; the reflection amplitude and ground truth methods. The analysis was done by RADAN 7 software. Based on the findings, the average error of thickness on the same day between continuous GPR and the core data were 2.87% and 8.72%, respectively. Second, dielectric analysis of three structural units was performed under different moisture conditions. As a result, the average dielectric values of macadam (3, 3.3, and 4), surface asphalt layer (4, 7.06, and 8.31), and cement-treated base (4.83, 10.88, and 11.88) were determined under dry, medium-wet, and wet conditions, respectively. The volumetric water difference (f) within the pavement was also estimated. As for the asphalt, macadam, and cement-treated base, the difference in the volume fraction of water (f) was 0.06, 0.01, and 0.1, respectively, under dry and wet conditions, and 0.04, 0.004, and 0.09, respectively, under dry and medium-wet conditions. Overall, the findings demonstrate that reasonably accurate assessments of the pavement thickness, structure, dielectric values, and amplitude of aged roads can be achieved by using a GPR survey under various conditions.

Programmable metasurface based phase-modulating reflector for 2.4 GHz wireless communications

Abstract This paper presents an innovative programmable metasurface structure that achieves precise phase control within the 2–2.7 GHz frequency range by adjusting the state of varactor diodes embedded in the unit cells. The design employs a single diode, which simplifies the structure, reduces manufacturing costs, and minimizes reflection loss. At 2.4 GHz, the metasurface achieves 1-bit phase responses of 0° and 180°, with a reflection amplitude exceeding 0.72, demonstrating excellent reflective performance. Moreover, as the 2.4 GHz frequency is closely related to wireless communication bands, this programmable metasurface shows significant potential in the field of wireless communication encryption. By integrating dual varactor diodes, the design enables 2-bit phase control with reflection phase angles of 0°, 90°, 180°, and 270°. To validate the design, a 1-bit metasurface structure was fabricated and tested, with experimental results showing a high degree of consistency with simulations, highlighting the potential of this structure in enhancing wireless communication security.

New integrable RG flows with parafermions

We consider irrelevant deformations of massless RSOS scattering theories by an infinite number of higher [TT¯]s operators which introduce extra non-trivial CDD factors between left-movers and right-movers. It is shown that the resulting theories can be UV complete after bypassing typical Hagedorn-like singularities if the coefficients of the deformations are fine-tuned. By classifying all integrable cases, we have discovered a new UV complete QFT associated to the Mp (p ≥ 3) minimal CFT based on the integrable structure of the RSOS scattering theory. This new theory is the massless ℤp−1 parafermionic sinh-Gordon (PShG) model with a self-dual coupling constant. This correspondence is confirmed by showing that the scale-dependent vacuum energies computed by the thermodynamic Bethe ansatz derived from the S-matrices match those from the quantization conditions for the PShG models using the reflection amplitudes.

Complex Reflectivity Modulation Characteristics at Visible Wavelength Using Liquid Crystal on a Metasurface Device

Active metasurface device capable of complex modulation in the visible light range is demonstrated. To realize complex modulation, a liquid crystal (LC) of twisted nematic mode on a plasmonic antenna metasurface, where resonance wavelength is sensitive to its geometry and nearby optical environment, is integrated. For the LC process on the metasurface, the alignment characteristics of the material exposed to the LC on the metasurface are first identified and the polyimide alignment layer is omitted. The LC works in twisted nematic mode to enhance complex modulation characteristics. The complex reflectivity coefficient is measured while varying the voltage applied to both the antenna and metal electrode in the visible light region. Complex reflectivity into a doughnut shape with a small voltage variation of 3.1 V on the antenna electrode and 2.5 V on the metal electrode is successfully modulated. The largest complex modulation is achieved at a wavelength of 660 nm, with phase and reflectivity amplitude modulations of 0–2π radian in a doughnut shape and 0.3 and 0.6, respectively. So far true holographic experience is limited by high‐order overlapping and twin images. Through this approach, a technical method is suggested for overcoming such obstacles and accomplishing advanced holographic display.

Seismic geomorphology and evolution of Mid-Late Miocene deepwater channels offshore Taranaki basin, New Zealand

Deepwater channels play a significant role in deep marine environments by transporting sediments to deep marine environments, but they are also hydrocarbon reservoirs. In contrast, traditional seismic interpretation techniques have provided insights into these features; intricate channel-fill heterogeneities present challenges in revealing small features or associated elements. This study integrates high-resolution 3D seismic data, relative time geologic models (RGT), spectral decomposition, and geobody to identify the Middle-late Miocene submarine channels, their evolution, and their associated deposition elements. The geomorphologic and stratigraphic analysis results have revealed four depositional elements in the study area. These include (1) channel complexes, (2) distributary channels, (3) frontal splay channel complexes, and (4) crevasse splays. However, the channels lack constructional levee development outside the channel banks, which is linked to the limited sediment supply to deep areas. The identified channels are characterized by a narrow to wide width (0.37 km–1.92 km), a low to high degree of sinuosity, medium incision depths, and lateral migration. The channel fill geometries are highly variable, displaying horizontal to sub-horizontal, lateral accretion, divergent, and inclined reflection packages. Most channels originate as large and wide channels from the northeast and prograde southwest direction of the Taranaki coastline, and they have evolved differently at different development stages. The channel fills exhibit a variable basal amplitude reflection, ranging from medium to high, indicating the presence of sand-prone and mixed facies, such as sand and mudstone. The spectral decomposition maps show variable color intensity, which implies different facies associations within the channels. The channel evolution is likely to be controlled by the interplay of sediment discharge, faults, sea level changes, variable gravity flow strength, and the type of materials supplied from the shelf edge.

Silicon rich nitride: a platform for controllable structural colors

Abstract High refractive index dielectric materials like silicon rich nitride (SRN) are critical for constructing advanced dielectric metasurfaces but are limited by transparency and complementary metal oxide semiconductor (CMOS) process compatibility. SRN’s refractive index can be adjusted by varying the silicon to nitride ratio, although this increases absorption, particularly in the blue spectrum. Dielectric metasurfaces, which utilize the material’s high dielectric constant and nano-resonator geometry, experience loss amplification due to resonance, affecting light reflection, light transmission, and quality factor. This study explores the impact of varying the silicon ratio on structural color applications in metasurfaces, using metrics such as gamut coverage, saturation, and reflection amplitude. We found that a higher SRN ratio enhances these metrics, making it ideal for producing vivid structural colors. Our results show that SRN can produce a color spectrum covering up to 166 % of the sRGB space and a resolution of 38,000 dots per inch. Fabricated samples vividly displayed a parrot, a flower, and a rainbow, illustrating SRN’s potential for high-resolution applications. We also show that SRN can provide a better CIE diagram coverage than other popular metasurfaces materials. These findings highlight the advantages of SRN for photonic devices, suggesting pathways for further material and application development.

Reflection and transmission amplitudes in a digital quantum simulation

In this paper we show how to measure in the setting of digital quantum simulations the reflection and transmission amplitudes of the one-dimensional scattering of a particle with a short-ranged potential. The main feature of the protocol is the coupling between the particle and an ancillary spin-1/2 degree of freedom. This allows us to reconstruct tomographically the scattering amplitudes, which are in general complex numbers, from the readout of one qubit. Applications of our results are discussed.

Geological characteristics and seismic identification of reservoirs in the Colorado Basin off the Atlantic coast of Argentina

Abstract The Colorado Basin is a hot exploration frontier basin conjugated with the southwest coast of Africa which has undergone four evolutionary stages: Carboniferous-Jurassic pre-rift, Jurassic-Early Cretaceous rift, Late Cretaceous transition and passive marginal drift since Paleocene. Major oil and gas discoveries have been made in the conjugated Orange Basin in recent years, including the Graff field and Venus field discovered in 2022 with recoverable reserves of 550 Mboe and 2.3 Bboe, respectively. This indicates that the basin has good oil and gas exploration potential. Based on the analysis of drilling data and seismic data, it is concluded that the basin has a mature oil-gas generation system and better reservoir conditions. The pre-rift and syn-rift source rocks are confirmed by 5 Wells with oil and gas shows in the shallow water shelf, and all have entered the hydrocarbon generation threshold. Reservoir distribution and trap-sealing conditions have become key factors in oil and gas exploration. this paper describes the reservoir characteristics in the drilling data, and extrapolates the seismic reflection characteristics of the same strata, and predicts the reservoir distribution in the unexplored area of the basin. The reservoir lithology and sedimentary facies are analyzed based on the gamma logging curves. Reservoir identification and reasonable prediction on seismic profile are mainly determined by seismic reflection amplitude and horizon calibration. The basin has three sets of reservoirs, namely, pre-rift Permian underwater fan sandstone, Lower Cretaceous alluvial fan sandstone of syn-rift period and Upper Cretaceous Colorado Formation shallow marine sandstone of transitional period. Among them, Colorado Formation sandstone reservoir has the best physical property conditions, with a maximum porosity of 32% and a thickness of 1000m. The Cretaceous and Paleogene turbidite sandstone of slope fan facies are potential reservoir in the deep waters, which mainly form litho-stratigraphic traps in the continental slope.

Aperiodic multilayer masks for M3D mitigation in high- and hyper-NA extreme ultraviolet lithography

As extreme ultraviolet lithography tools with higher image numerical apertures (NAi) are introduced, the range of angles at the multilayer mask stack is also increased. Lithography systems are designed to fulfill the “abbe sine rule,” where NAm is related to NAi by the reduction factor. As a result, increases in NAi will increase NAm. High-NA and hyper-NA systems will be implemented with anamorphic optics, 4× in “X,” and 8× in “Y” to reduce the necessary angles. Even so, hyper-NA masks may see illumination angles as high as 13.4°, up from 10.8° for 0.33 NA. This represents a challenge for maintaining through-angle mask reflection using the current periodic mask multilayer structures. In addition to the reflectance amplitude, the phase of reflected light, which plays an important role in imaging, is also strongly influenced by increasing angles. The propagation of light through each bilayer in the stack imparts a phase shift based on the incidence angle. This is then accumulated over many layers, inducing phase effects, which are unique to each illumination point. This will become especially true for high-NA and hyper-NA mask applications. While adjustments to the multilayer period are sufficient to achieve acceptable reflectance, periodic multilayers may suffer in normalized image log slope (NILS) and image placement error (IPE) metrics as a result of strong oblique multilayer M3D phase effects. In this work, we present a first principles methodology for the systematic reduction of oblique multilayer M3D effects through the use of aperiodic multilayer design. We find that when used for low-k1, hyper-NA patterning NILS is improved by 40+%, while IPE through pitch is similarly improved. Under high-NA conditions, a 5%–25% NILS gain is found alongside the enhanced depth of focus.

Interdigitated-comb piezoelectric phononic crystals for innovative SAW devices

In this paper, piezoelectric phononic crystals made up of interdigitated combs in floating potential condition are studied. Calculation of the dispersion curves shows that, in addition to Bragg bandgaps due to the presence of periodic electrodes, supplementary bandgaps are present corresponding to electrical resonance/antiresonance of the comb pairs. Calculation of the reflection coefficient of finite-sized mirrors reveals the presence of high amplitude reflection coefficient lobes near these bandgap frequencies. The electrical response of single port resonators using these interdigitated comb mirrors fabricated with Al metallization on LiTaO3 POI substrate is contrasted with that of a resonator with classical mirrors, providing experimental verification of this mechanism for bandgap opening. Possible applications for SAW device design are finally discussed.

Compensating Acquisition Footprint for Amplitude-Preserving Angle Domain Common Image Gathers Based on 3D Reverse Time Migration

Angle domain common image gathers (ADCIGs) play a crucial role in seismic exploration, offering prestack underground illumination information that aids in validating migration velocity and conducting prestack amplitude versus angle (AVA) analysis for reservoir characterization. This paper introduces an innovative approach for compensating amplitude errors caused by irregular seismic acquisition geometries in ADCIGs. By incorporating an angle domain illumination compensation factor, the proposed method effectively modifies these errors, preserving the amplitude of seismic reflectivity in the prestack angle domain. The effectiveness of the proposed approach is validated through comprehensive tests conducted on synthetic and field data examples. The results demonstrate the capability of the method to enhance the quality of ADCIGs derived from 3D reverse time migration (RTM), yielding accurate and reliable amplitude preservation. While the illumination compensation factor assumes a vertically linear velocity model, the method holds promise for extension to more complex media and diverse migration techniques. This suggests its applicability and adaptability beyond the specific assumptions considered in this study. In conclusion, this paper presents an innovative angle domain illumination compensation factor that significantly improves the quality of ADCIGs by addressing amplitude errors arising from irregular seismic acquisition geometries. The experimental validation using synthetic and field data confirms the effectiveness of the proposed method within the context of 3D RTM. Furthermore, the technique holds potential for broader application in more complex subsurface scenarios and various migration methodologies.

Synergizing deep learning and phase change materials for four-state broadband multifunctional metasurfaces in the visible range

In this article, we report, for the first time, broadband multifunctional metasurfaces with more than four distinct functionalities. The constituent meta-atoms combine two different phase change materials, VO2 and Sb2S3 in a multi-stage configuration. Finite-difference time-domain simulations demonstrate a broadband reflection amplitude switching between the four states in visible range due to the enhanced cavity length modulation effect from the cascaded Fabry–Perot cavities, overcoming the inherent small optical contrast between the phase change material (PCM) states. This, along with the reflection phase control between the four states, allows us to incorporate both amplitude and phase-dependent properties in the same metasurface — achromatic deflection, wavelength beam splitting, achromatic focusing, and broadband absorption, overcoming the limitations of previous functionality switching mechanisms for the visible band. We have used a Tandem Neural network-based inverse design scheme to ensure the stringent requirements of different states are realized. We have used two forward networks for predicting the reflection amplitude and phase for a meta-atom within the pre-defined design space. The excellent prediction capability of these surrogate models is utilized to train the reverse network. The inverse design network, trained with a labeled data set, is capable of efficiently navigating through the vast parametric space to produce the optimized meta-units given the desired figure-of-merits in terms of reflection amplitude and phase for the four states. The optical characteristics of two inverse-designed metasurfaces have been evaluated as test cases for two different sets of design parameters in the four states. Both structures demonstrate the four desired broadband functionalities while closely matching the design requirements, suggesting their potential in visible-range portable medical imaging devices. The findings of this work will open new horizons for active metasurface design with broadband complex multifunctionalities in different spectral bands.

Constraints on fracture connectivity from amplitude variations with incidence angle and azimuth analysis

The analysis of seismic reflection amplitude variations with incidence angle and azimuth (AVAz) is a powerful tool for studying and characterizing fractured formations. There is evidence to suggest that wave-induced fluid pressure diffusion (FPD) within connected fractures can significantly affect the AVAz response. This, in turn, indicates that this seismic attribute may contain information on the connectivity degree of the fracture network, which represents a key hydraulic property of fractured formations. The assessment of the sensitivity of seismic reflectivity with respect to fracture connectivity accounting for FPD effects to date is limited to 2D models, which is mainly due to the complexity and the associated computational cost of modeling the effective properties of the corresponding generically anisotropic 3D media. To overcome these issues, we use a numerical upscaling procedure based on Biot’s theory of poroelasticity that allows us to obtain effective anisotropic representations of 3D fractured formations accounting for the FPD effects. Using these effective properties, we then perform a plane-wave analysis to compute the reflection coefficients at the top of the corresponding fractured formation. The results of our numerical analyses extend the previous 2D studies and demonstrate that seismic reflection coefficients are highly sensitive to the degree of connectivity of the fracture networks. The reflectivity responses of formations comprising connected and unconnected fractures indicate pronounced differences not only with respect to incidence angle but also with respect to azimuth. Quite importantly, our results also demonstrate that crossplots of commonly used AVAz coefficients permit us to identify regions with higher or lower fracture connectivity.

Seismic Inversion Techniques and Attribute Analysis for Accurate Well Placement in Offshore Niger Delta Basin, Nigeria

Before this study, simple methods like seismic attribute analysis have often been used for reservoir characterization with successes however, there is still the need to reduce exploration uncertainty to a negligible level and boost investors’ confidence. This study integrated seismic inversion with seismic attribute analysis to better characterize the reservoirs in MTW Field in deep-offshore Niger Delta Basin. Five (5) wells with complete suite of petrophysical logs, three-Dimensional (3-D) seismic data, checkshot and other well information were used. The well data were thoroughly quality checked, reservoirs were litho-stratigraphically delineated and used for petrophysical analysis across the wells. This was followed by seismic-to- well-tie, seismic interpretation, and seismic attribute analysis (Root Mean Square-RMS) generated using depth surface maps. 3-D static reservoir model and volumetric evaluation were carried out. Petrophysical properties were derived and distributed across the 3-D static model using sequential gaussian simulation algorithm to ascertain shale volume spread across the model. To improve the seismic resolution and reduce interpretation uncertainty at greater depth, model- based post-stack seismic inversion was performed to obtain acoustic impedance cube. Litho-stratigraphic and petrophysical analysis result revealed five reservoir sands (A, B, C, D, and E). Reservoir-A was seen to be more viable with a thickness of 13.42 m, high effective porosity of 27%, permeability of 3187.53 mD, low water saturation of 34% and low shale volume of 11% which are indication good reservoir quality and producibility. The seismic interpretation revealed thirty-one (31) growth and antithetic faults oriented in the NE-SW and NW-SE directions, respectively. The RMS result revealed high amplitude reflectivity which is a measure of zone of interest. Based on this, seven (7) prospects and three (3) leads were identified. The seismic inversion result shows a high level of accuracy with a correlation coefficient of 0.997; 0.997; 0.995; and 0.996 in MTW-001, MTW-003ST1, MTW-004ST1 and MTW-005 wells, respectively. The acoustic impedance successfully resolved and improved on the resolution of the seismic stacking velocity especially at reservoir layers and at depth deeper than 3600 ms. Acoustic impedance as a layer property has improved on the lateral and vertical resolutions of the data beyond what the usual seismic interval velocity could image thus, validating some of the prospects and leads identified in this study. This demonstrated that uncertainty can be reduced by a blend of RMS and seismic inversion in identifying reservoir for accurate placement of wells. It is therefore recommended that E and P operators should adopt the technique in their future hydrocarbon exploration endeavor in frontier and matured basins.

WITHDRAWN: Perfect asymmetric transmission for linear polarization in background reflection-free bilayer dielectric metasurfaces

In spite of the importance of asymmetric transmission (AT) with near-unity value and significantly high contrast of transmission, such a perfect AT has not yet been realized in reciprocal systems. For single resonance, it is already known that the upper limit of AT is identical to the background amplitude reflection coefficient. Nevertheless, if multiple resonances simultaneously contribute to AT, their coherent coupling enables us to obtain perfect AT, even when background reflection completely vanishes. Taking bilayer dielectric metasurfaces composed of orthogonal silicon nanorods embedded in silica glass as examples, here we show that perfect AT can be realized for linear polarization with characteristics comparable with bulky optical isolators based on Faraday effect: AT of 0.9994 with dramatically high contrast 35.1dB at telecom wavelength, the spectral position of which is tunable by properly changing the structural parameters. The analytical model based on the quasinormal-mode expansion well agrees with numerical results, revealing the concurrent contributions of multiple resonances. The presented perfect AT has the advantages of excellent performances of AT and compact structures without bulky devices for field bias or temporal modulations, enabling practical applications for optical computing, high-contrast polarization multiplexing and conversion.

Spectroscopic Phenological Characterization of Mangrove Communities

Spaceborne spectroscopic imaging offers the potential to improve our understanding of biodiversity and ecosystem services, particularly for challenging and rich environments like mangroves. Understanding the signals present in large volumes of high-dimensional spectroscopic observations of vegetation communities requires the characterization of seasonal phenology and response to environmental conditions. This analysis leverages both spectroscopic and phenological information to characterize vegetation communities in the Sundarban riverine mangrove forest of the Ganges–Brahmaputra delta. Parallel analyses of surface reflectance spectra from NASA’s EMIT imaging spectrometer and MODIS vegetation abundance time series (2000–2022) reveal the spectroscopic and phenological diversity of the Sundarban mangrove communities. A comparison of spectral and temporal feature spaces rendered with low-order principal components and 3D embeddings from Uniform Manifold Approximation and Projection (UMAP) reveals similar structures with multiple spectral and temporal endmembers and multiple internal amplitude continua for both EMIT reflectance and MODIS Enhanced Vegetation Index (EVI) phenology. The spectral and temporal feature spaces of the Sundarban represent independent observations sharing a common structure that is driven by the physical processes controlling tree canopy spectral properties and their temporal evolution. Spectral and phenological endmembers reside at the peripheries of the mangrove forest with multiple outward gradients in amplitude of reflectance and phenology within the forest. Longitudinal gradients of both phenology and reflectance amplitude coincide with LiDAR-derived gradients in tree canopy height and sub-canopy ground elevation, suggesting the influence of surface hydrology and sediment deposition. RGB composite maps of both linear (PC) and nonlinear (UMAP) 3D feature spaces reveal a strong contrast between the phenological and spectroscopic diversity of the eastern Sundarban and the less diverse western Sundarban.