Gradient Index Research Articles

Calculation of zonal power and astigmatism of a freeform gradient index lens with freeform surfaces.

Freeform gradient index (F-GRIN) lenses have been recently shown to enable compact optical design. However, aberration theory is only fully developed for rotationally symmetric distributions with a well-defined optical axis. The F-GRIN has no well-defined optical axis, and rays are continuously perturbed along their trajectory. Optical performance can be understood without abstracting optical function to numerical evaluation. The present work derives freeform power and astigmatism along an axis through a zone of an F-GRIN lens with freeform surfaces. Zonal power and astigmatism can be assessed without tracing any rays, capturing mixed contributions of the F-GRIN and freeform surface. Theory is compared with a commercial design software numerical raytrace evaluation. The comparison shows that the raytrace-free (RTF) calculation represents all raytrace contributions within a margin of error. In one example, it is demonstrated that linear terms of index and surface alone in an F-GRIN corrector can correct the astigmatism of a tilted spherical mirror. Accounting for the induced effects of the spherical mirror, RTF calculation provides the amount of astigmatism correction of the optimized F-GRIN corrector.

Accretion of aerodynamically large pebbles

ABSTRACT Due to their aerodynamical coupling with gas, pebbles in protoplanetary discs can drift over large distances to support planet growth in the inner disc. In the past decade, this pebble accretion has been studied extensively for aerodynamically small pebbles (Stokes number St < 1). However, accretion can also operate in the St > 1 mode, e.g. when planetesimals collisionally fragment to smaller bodies or when the primordial gas disc disperses. This work aims to extend the study of pebble accretion to these aerodynamically loosely coupled particles. We integrate the pebble’s equation of motion, accounting for gas drag, stellar and planetary gravity, in the mid-plane of a laminar disc. The accretion probability (ϵ) is calculated as function of Stokes number, disc pressure gradient index, planet mass, and eccentricity. We find that for Stokes number above unity ϵ(St) first rises, due to lower drift and aided by a large atmospheric capture radius, until it reaches a plateau where the efficiency approaches 100 per cent. At high St, the plateau region terminates as particles become trapped in resonance. These results are well described by a semi-analytical ‘kick-and-drift’ model and we also provide fully analytical prescriptions for ϵ. We apply our model to the accretion of ${\sim }30\, \mu \mathrm{m}$ dust particles in a dispersing protoplanetary and secondary (CO-rich) debris disc. It shows that such physically small particles are mainly accreted as aerodynamically large Stokes number pebbles during the debris disc phase. Earth-mass planets may obtain ∼25 per cent of their heavy elements through this late accretion phase.

A novel dose fall-off index and preliminary application in brain and lung stereotactic radiotherapy.

Stereotactic radiotherapy (SRT) has been widely used for the treatment of brain metastases and early stage non-small-cell lung cancer (NSCLC). Excellent SRT plans are characterized by steep dose fall-off, making it critical to accurately and comprehensively predict and evaluate dose fall-off. A novel dose fall-off index was proposed to ensure high-quality SRT planning. The novel gradient index (NGI) had two different modes: NGIx V for three-dimensions and NGIx r for one-dimension. NGIx V and NGIx r were defined as the ratios of the decreased percentage dose (x%) to the corresponding isodose volume and equivalent sphere radii, respectively. A total of 243 SRT plans at our institution between April 2020 and March 2022 were enrolled, including 126 brain and 117 lung SRT plans. Measurement-based verifications were performed using SRS MapCHECK. Ten plan complexity indexes were calculated. Dosimetric parameters related to radiation injuries were also extracted, including the normal brain volume exposed to 12 Gy (V12 ) and 18 Gy (V18 ) during single-fraction SRT (SF-SRT) and multi-fraction SRT (MF-SRT), respectively and the normal lung volume exposed to 12 Gy (V12 ). The performance of NGI and other common dose fall-off indexes, gradient index (GI), R50% and D2cm were evaluated using Spearman correlation analysis to explore their correlations with the PTV size, gamma passing rate (GPR), plan complexity indexes and dosimetric parameters. There were statistically significant correlations between NGI and PTV size (r = -0.98, p < 0.01 for NGI50 V and r = -0.93, p < 0.01 for NGI50 r), which were the strongest correlations compared with GI (r = 0.11, p = 0.13), R50% (r = -0.08, p = 0.19) and D2cm (r = 0.84, p < 0.01). The fitted formulas of NGI50 V = 23.86V-1.00 and NGI50 r = 113.5r-1.05 were established. The GPRs of enrolled SRT plans were 98.6 ± 1.7%, 94.2 ± 4.7% and 97.1 ± 3.1% using the criteria of 3%/2 mm, 3%/1 mm and 2%/2 mm, respectively. NGI50 V achieved the strongest correlations with various plan complexity indexes (|r| ranged from 0.67 to 0.91, p < 0.01). NGI50 V also showed the highest r values with V12 (r = -0.93, p < 0.01) and V18 (r = -0.96, p < 0.01) of the normal brain during SF-SRT and MF-SRT, respectively and V12 (r = -0.86, p < 0.01) of the normal lung during lung SRT. Compared with GI, R50% and D2cm , the proposed dose fall-off index, NGI, had the strongest correlations with the PTV size, plan complexity and V12 /V18 of the normal tissues. These correlations established on NGI are more helpful and reliable for SRT planning, quality control and reducing the risk of radiation injuries. This article is protected by copyright. All rights reserved.

Gradient index effect assisted anisotropic broadband absorption in α-MoO3 metamaterial.

As an excellent natural hyperbolic material (HM), α-M o O 3 has a larger hyperbolic bandwidth and longer polariton lifetime than other HMs, which makes it an ideal candidate for broadband absorbers. In this work, we theoretically and numerically investigated the spectral absorption of an α-M o O 3 metamaterial using the gradient index effect. The results show that the absorber has an average spectral absorbance of 99.99% at 12.5-18µm at transverse electric polarization. When the incident light is transverse magnetic polarization, the broadband absorption region of the absorber is blueshifted, and a similar strong absorption is achieved at 10.6-12.2µm. By simplifying the geometric model of the absorber using equivalent medium theory, we find that the broadband absorption is caused by the refractive index matching of the metamaterial to the surrounding medium. The electric field and power dissipation density distributions of the metamaterial were calculated to clarify the location of the absorption. Moreover, the influence of geometric parameters of pyramid structure on broadband absorption performance was discussed. Finally, we investigated the effect of polarization angle on the spectral absorption of the α-M o O 3 metamaterial. This research contributes to developing broadband absorbers and related devices based on anisotropic materials, especially in solar thermal utilization and radiation cooling.

Additional Error of Optical Path Measurement Caused by Radial GRIN Lens With Mispositioned Sample

Radial gradient index (GRIN) lens is widely used in optical path measurement based on white light interferometry (WLI), yet the additional error caused by the GRIN lens when the sample under test (SUT) is not at the ideal position has rarely been discussed. To deal with this problem, a ray-tracing model is established to reveal the influence of angular tilt and axial offset of SUT when GRIN lens is applied. Simulations based on WLI are done using the parameters of a real GRIN lens. The results show that the maximum additional optical path change is as larger as 0.99μm within the range of ±0.1° angular tilt and ±2000μm axial offset of SUT, which can be regarded as additional error if the influence of GRIN lens is ignored. Experimental results of optical path change and insertion loss at different tilt angles of SUT simultaneously agree well with one set of simulation.

3D‐printed GRIN tools for synchrospeed polishing

AbstractAdditive technologies allow the flexible production of gradient index (GRIN) polishing tools with specifically adaptable removal functions. These were successfully developed and investigated for synchrospeed polishing.

Enabling High Precision Gradient Index Control in Subsurface Multiphoton Lithography.

Multiphoton lithography inside a mesoporous host can create optical components with continuously tunable refractive indices in three-dimensional (3D) space. However, the process is very sensitive at exposure doses near the photoresist threshold, leading previous work to reliably achieve only a fraction of the available refractive index range for a given material system. Here, we present a method for greatly enhancing the uniformity of the subsurface micro-optics, increasing the reliable index range from 0.12 (in prior work) to 0.37 and decreasing the standard deviation (SD) at threshold from 0.13 to 0.0021. Three modifications to the previous method enable higher uniformity in all three spatial dimensions: (1) calibrating the planar write field of mirror galvanometers using a spatially varying optical transmission function which corrects for large-scale optical aberrations; (2) periodically relocating the piezoelectrically driven stage, termed piezo-galvo dithering, to reduce small-scale errors in writing; and (3) enforcing a constant time between each lateral cross section to reduce variation across all writing depths. With this new method, accurate fabrication of optics of any index between n = 1.20 and 1.57 (SD < 0.012 across the full range) was achieved inside a volume of porous silica. We demonstrate the importance of this increased accuracy and precision by fabricating and characterizing calibrated two-dimensional (2D) line gratings and flat gradient index lenses with significantly better performance than the corresponding control devices. As a visual representation, the University of Illinois logo made with 2D line gratings shows significant improvement in its color uniformity across its width.

Dose Planning Evaluation of Intensity-Modulated Proton Therapy (IMPT) Technique Based on In-House Dynamic Thorax Phantom

One of the drawbacks of the Intensity Modulated Radiation Therapy (IMRT) technique is that the absorbed dose in healthy tissue is relatively high. Proton beam has characteristics that can compensate for these drawbacks. The Bragg peak characteristic of a proton beam allows the administration of high radiation doses to the target organ only. Non-Small Cell Lung Cancer (NSCLC) cases are located in the vicinity of many vital organs, so radiation doses that exceed a certain limit will have a significant impact on these organs. Proton is a heavy particle that exhibits interaction patterns with tissue heterogeneity that differ from that of photon. This study aims to determine the distribution of proton beam planning doses in the NSCLC cases with the Intensity Modulated Proton Therapy (IMPT) technique and compare its effectiveness with the IMRT technique. Treatment planning was done by using TPS Eclipse on the water phantom and on the in-house thorax dynamic phantom. The water phantom planning parameters used are one field at 0° and three fields at 45°, 135°, and 225°. In this study, a single, sum, and multiple field techniques on the in-house thorax dynamic phantom were used. The evaluation was performed by calculating Conformity Index (CI), Homogeneity Index (HI), and Gradient Index (GI) parameters for each treatment planning. As a result, a bit of difference in the CI the HI values are shown between IMPT and IMRT planning. The GI values of IMPT planning are in the range between 4.15-4.53, while the GI value of IMRT is 7.89. The histogram results of the planar dose distribution show that the IMPT treatment planning provides fewer off-target organ doses than the IMRT planning. Evaluation was also carried out on the IMPT treatment planning of target organs in five areas of interest and four OAR positions. The evaluation results were then compared with the IMRT measurement data. As a result, the value of the point doses at the target organ did not differ significantly. However, the absorbed dose with the IMPT technique at four OAR positions is nearly zero, which had a large difference compared to the IMRT technique.

Clinical Feasibility of Using Single-isocentre Non-coplanar Volumetric Modulated Arc Therapy Combined with Non-coplanar Cone Beam Computed Tomography in Hypofractionated Stereotactic Radiotherapy for Five or Fewer Multiple Intracranial Metastases

AimsTo evaluate the clinical feasibility of single-isocentre non-coplanar volumetric modulated arc therapy (NC-VMAT) with non-coplanar cone beam computed tomography (NC-CBCT) in hypofractionated stereotactic radiotherapy (HSRT) for five or fewer multiple brain metastases. Materials and methodsTen patients with multiple brain metastases who underwent single-isocentre NC-VMAT HSRT with limited couch rotations (within ±45°) and NC-CBCT with a limited scanning range (150–200°) were included in the current analysis. Conventional single-isocentre coplanar VMAT (C-VMAT) plans were generated and compared with NC-VMAT plans. The intracranial response and toxicities of single-isocentre NC-VMAT HSRT were also evaluated. ResultsCompared with C-VMAT, NC-VMAT generated better target conformity (P < 0.05), a lower gradient index (P < 0.05) and better normal brain tissue sparing, especially for volume ≥12 Gy, with a median reduction of 12.65 cm3. For 45° couch rotation, NC-CBCT produced sufficient image quality to differentiate bony anatomy, even with a 150° scanning range, which could be successfully used for patient set-up correction. After NC-CBCT, 57.1% of the measured non-coplanar set-up errors exceeded the threshold value. The median gamma passing rate of NC-VMAT was higher than that of C-VMAT plans (P < 0.05). The non-coplanar beam of NC-VMAT with NC-CBCT corrections exhibited superior gamma passing rate to that without NC-CBCT corrections. The intracranial objective response rate and disease control rate for all patients were 80% (8/10) and 100% (10/10), respectively, and the most common toxicities were headache (20%) and dizziness (20%). ConclusionNC-VMAT with limited couch rotation (within ±45°) combined with NC-CBCT with a limited scanning range (150–200°) markedly improves the plan quality and set-up accuracy in single-isocentre multiple-target HSRT.

Three-dimensional semi-analytical solutions of arbitrary functionally graded piezoelectric doubly curved shell panel under thermo-electric load

In this article, a methodological approach for the three-dimensional (3D) static behavior of functionally graded (FG) thermo-electro-elastic doubly curved shells subjected to a thermal and electrical load is presented. A coupling procedure based on the state space, a multilayered Runge-Kutta and transfer matrix methods is elaborated for numerical solution of the 3D thermo-electro-elastic governing equations. In the thickness direction, recursive relationships using a propagator matrix are elaborated allowing to handle arbitrary functionally graded effects. A global transfer matrix is formulated permitting to investigate the effects of various types of bottom and top surface temperature loads and heat flux. Some benchmark tests are presented to validate the presented approach and to analyze the influence of the material-property gradient index, the curvature radius ratio, the span-to-thickness ratio, the temperature, normal heat flux, and the electric voltage on the mechanic, electric, and thermal variables of doubly curved shells.

3D frictional contact of graded magneto-electro-elastic film-substrate system under electromagnetic fields

The 3D frictional contact model of graded magneto-electro-elastic (MEE) film-substrate system under electromagnetic fields is presented. The semi-analytical method (SAM) is used to solve this multi-physical contact problem. Firstly, the frequency response functions (FRFs) for every layer of MEE material subjected to unit mechanical, electric and magnetic loads are derived. Conjugate gradient method (CGM) is then employed to obtain contact responses with Discrete convolution-fast Fourier transformation (DC-FFT) speeding related calculations. Finally, multilayered model is used to approximate graded film with two types of grads, exponentially varying grad (EVG) and volume-fraction varying grad (FVG), the effects of the type and thickness of graded film and the friction coefficient are investigated. The results show that EVG film with gradient index less than one or FVG film with smaller volume fraction of piezoelectric phase at the surface are preferred for the MEE film-substrate systems.

Inkjet-printed freeform gradient refractive index Alvarez-Lohmann optics for vision correction in respiratory masks

Inkjet-print additive manufactured freeform gradient refractive index representations of an Alvarez-Lohmann lens were developed and optimized for use in vision-correction inserts for respiratory masks. A series of planar 30-mm by 20-mm Alvarez-Lohmann lens pair were printed and characterized. Select lens pairs were mounted with printed mechanical lens mounts and translation guides optimized for vision correction. Metrology showed accurate reproduction of the cubic refractive phase functions. Tests matching simulated performance showed a large diopter adjustment over a large eyebox and a wide gaze angle. The printed optics were environmentally tested and then mounted in a respiratory mask and demonstrated with glove-accessible control electronics. The performance demonstrates the benefits of using printed three-dimensional freeform gradient index optics for implementing complex refractive optical functions for challenging applications including artificial and virtual reality systems.

Finite element analysis of functionally graded magneto-electro-elastic porous cylindrical shells subjected to thermal loads

Functionally graded materials with porosity have received increased application in satellites, space vehicles, aircraft, and other transportation systems. The multi-physics coupled modeling technique for structural response analysis remains a big challenge. This paper develops a finite element formulation based on the first-order shear deformation (FOSD) hypothesis for evaluation of the static and dynamic behavior of functionally graded magneto-electro-elastic porous (FG-MEEP) cylindrical shells under thermal loads. Four types of thermal loads such as uniform, linear, sinusoidal, and heat conduction temperature rise are included in the FE model. Furthermore, FG-U, FG-V, FG-O, and FG-X distributions of porosity is considered. The material parameters of FG-MEEP are obtained by modified power law. Two forms of material gradation in the framework of ‘B’-rich bottom and ‘F’-rich bottom are used. The correctness of the present model is verified by comparing with the results of literature. Finally, parametric studies are adopted to analyze the static and dynamic response of FG-MEEP cylindrical shell by varying functionally graded pattern, gradient index, porosity volume, temperature, porosity distribution, etc. These numerical results can serve as benchmarks for the future study of porous structures in thermal environment.

Size-Dependent Rigid–Flexible Coupling Dynamics of Functionally Graded Rotating Moderately Thick Microplates

Micro air vehicles, which are typical small-sized rotating-motion systems, have seen major advancements in recent years. To provide some theoretical basis for developing and producing micro air vehicles, this study establishes a novel rigid–flexible coupling dynamic model for functionally graded (FG) moderately thick rectangular microplates attached to a central rotating rigid hub based on the modified couple stress theory and first-order shear deformation theory. The proposed model incorporates nonlinear coupling term of in-plane deformation to reflect the dynamic stiffening effect caused by rotational motion. Material characteristics of the FG microplate have a linear power-law distribution along the thickness axis. Further, the discrete form dimensionless coupling dynamic equations and their numerical solutions are obtained by combining the Euler–Lagrange equation and the Chebyshev–Ritz method. Convergence and comparative studies are carried out to demonstrate the accuracy and validity of the proposed model. Thereafter, the influence of material length scale parameter, rotational speed, gradient index, and aspect ratio on the frequency of the microplates is investigated. Numerical results reveal that couple stress and dynamic stiffening effects both enhance the rigidity of the microplates, whereas the gradient index decreases the rigidity. Nonlinear coupling term which leads to significant differences in frequency value and trace line can’t be ignored for rotative structure. In-plane motion and its coupling terms play a significant function for the moderately thick or thick microplates. The increase of rotational speed and gradient index will reduce the size dependency of the microplate. Furthermore, the frequency trajectory steering and corresponding mode transition phenomenon are graphically represented.

Terahertz spoof surface plasmon polariton gradient index lens

Plasmonics takes advantage of surface plasmon polaritons (SPPs), which have the characteristics of strong subwavelength field confinement and enhancement. Plasmonic devices that confine light in regions with dimensions that are smaller than the wavelength have important application prospects in on-chip integrated circuits. Nonetheless, at terahertz frequencies, the weak confinement of SPPs and immature near-field technology hinder the development of related devices. Here, a highly confined SPP mode (spoof SPP) is implemented by structuring metal surfaces. Gradient index lenses with variable indices are constructed by fine-tuning the size of the pillars, and the characteristics of several different lenses are examined and explored by scanning near-field terahertz microscopy. Thus, terahertz waves are regulated and more possibilities are provided for further miniaturization and compactness of THz devices.

OptImal Gamma kNife lIghTnIng sOlutioN (IGNITION) score to characterize the solution space of the Gamma Knife FIP optimizer for stereotactic radiosurgery.

The objective of this study is to evaluate the user-defined optimization settings in the Fast Inverse Planning (FIP) optimizer in Leksell GammaPlan® and determine the parameters that result in the best stereotactic radiosurgery (SRS) plan quality for brain metastases, benign tumors, and arteriovenous malformations (AVMs). Thirty patients with metastases and 30 with benign lesions-vestibular schwannoma, AVMs, pituitary adenoma, and meningioma-treated with SRS were evaluated. Each target was planned by varying the low dose (LD) and beam-on-time (BOT) penalties in increments of 0.1, from 0 to 1. The following plan quality metrics were recorded for each plan: Paddick conformity index (PCI), gradient index (GI), BOT, and maximum organ-at-risk (OAR) doses. A novel objective score matrix was calculated for each target using a linearly weighted combination of the aforementioned metrics. A histogram of optimal solutions containing the five best scores was extracted. A total of 7260 plans were analyzed with 121 plans per patient for the range of LD/BOT penalties. The ranges of PCI, GI, and BOT across all metastatic lesions were 0.58-0.97, 2.1-3.8, and 8.8-238 min, respectively, and were 0.13-0.97, 2.1-3.8, and 8.8-238 min, respectively, for benign lesions. The objective score matrix showed unique optimal solutions for metastatic lesions and benign lesions. Additionally, the plan metrics of the optimal solutions were significantly improved compared to the clinical plans for metastatic lesions with equivalent metrics for all other cases. In this study, FIP optimizer was evaluated to determine the optimal solution space to maximize PCI and minimize GI, BOT and OAR doses simultaneously for single metastatic/benign/non-neoplastic targets. The optimal solution chart was determined using a novel objective score which provides novice and expert planners a roadmap to generate the most optimal plans efficiently using FIP.

Beamforming Phased-Array-Fed Lenses With &gt;0.5λ-Spaced Elements

We propose a phased-array-fed lens (PAFL) antenna that is capable of beamforming like a phased array but with array elements spaced beyond <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.5\lambda $ </tex-math></inline-formula> . The PAFL produces high-quality scanned beams using only five active feeds. This architecture represents dramatic cost and power savings over conventional phased arrays while providing many of the features. We present an optimal beamforming method to achieve the maximum gain at any angle using a subset of feeds and a multiobjective optimizer using particle swarm optimization for more granular pattern control. The method is applied to several simulated state-of-the-art lens antennas with good performance confirming the generality of the method. The theory is demonstrated with a prototype PAFL comprising a 4 inch aperture gradient-index (GRIN) lens antenna, an 8-element <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.725\lambda $ </tex-math></inline-formula> -spaced linear patch array operating at 29 GHz, and a commercial Ka-band SATCOM beamformer integrated circuit (IC). The prototype achieves the maximum gain at all angles and improves the scan loss by 4 dB at ±50°.

Inverse design of high-NA metalens for maskless lithography

Abstract We demonstrate an axisymmetric inverse-designed metalens to improve the performance of zone-plate-array lithography (ZPAL), one of the maskless lithography approaches, that offer a new paradigm for nanoscale research and industry. First, we derive a computational upper bound for a unit-cell-based axisymmetric metalens. Then, we demonstrate a fabrication-compatible inverse-designed metalens with 85.50% transmission normalized focusing efficiency at 0.6 numerical aperture at 405 nm wavelength; a higher efficiency than a theoretical gradient index lens design (79.98%). We also demonstrate experimental validation for our axisymmetric inverse-designed metalens via electron beam lithography. Metalens-based maskless lithography may open a new way of achieving low-cost, large-area nanofabrication.

Morphotectonic Analysis of Wadi Al-Batin Alluvial Fan, South of Iraq, Using Remote Sensing and GIS Techniques

This research aimed to know the tectonic activity of the Wadi Al-Batin alluvial fan using hydrological and morphotectonic analyses. Wadi Al-Batin alluvial fan is deposited from Wadi Al-Rimah in Saudi Arabia, which extended to Iraqi and Kuwait international boundaries. The longitudinal and transverse faults that characterize this region were common. The Abu- Jir-Euphrates faults have a significant impact on the region. The faults zone consists of several NW- SE trending faults running from the Rutba in western Iraq to the south along the Euphrates through Kuwait and meeting the Al-Batin fault to the Jal Al-Zor fault. The Hydromorphometric analysis of the present fan shows five watersheds having asymmetry shapes, more elongated and activity from the elongation ratio and asymmetry factor values. In contrast, transverse topographic symmetry and mountain front sinuosity factor have moderate to low activity from the stream length gradient index. The morphotectonic analysis suggests that the Wadi Al-Batin alluvial fan has a moderate tectonic activity due to the tectonic activity of the subsurface lineaments and the oil field activities found in the region.

Morphomertic and neotectonic study of Upper Teesta River basin, Sikkim Himalaya using geospatial techniques

This study is done on the basis of the surface and subsurface faults and active tectonic processes which disrupt the pattern of the drainage system present in the basin. The pattern of the drainages and their morphological features shown in the morphometric drainage basin areas which are used as a sign of neotectonics activity. This study is focused on the Upper Teesta River basin of the Sikkim Himalayan. For the study of the morphometric and morphotectonic analysis of the Upper Teesta River basin, ALOS PALSAR DEM was used to generate the drainage order of the basin with the help of the Arc GIS Software. The estimated drainage order of the basin is 6th. In this study, morphotectonic parameters such as asymmetry factor, elongation ratio, transverse topography asymmetry, mountain-front sinuosity, ratio of valley floor width to valley height, and hypsometric Integral was estimated 45.66, 0.55, 0.25, 1.08, 0.94, 0.44 respectively. These all-parameters value show the Upper Teesta River Basin is tectonically active. The stream gradient index of the basin was calculated >500 indicate the study region tectonically active. This research is validated using 50 years (1971–2020) earthquake data. Therefore, geospatial tool is an important tool to know the area is neo tectonically active.