Mr. Tawsif Ibne Alam Profile

Tawsif Ibne Alam

Ph.D Student at Hong Kong Polytechnic Univ

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Proceedings Article | 12 March 2024 Presentation + Paper

Nonlinear optical responses of ternary 2D GeSeTe nanosheets in NIR regime

Sumaiya Umme Hani, Safayet Ahmed, Tawsif Ibne Alam, Yuen Hong Tsang

Proceedings Volume 12888, 1288809 (2024) https://doi.org/10.1117/12.3015104

KEYWORDS: Lithium, Graphene, Applied physics

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Ternary 2D materials, potential candidates for next generation technology showcase boundless opportunities by providing greater degree of freedom through integration of various elements with compositional variety. GeSeTe is a chalcogenide compound with great environmental stability and phase changing feature, making it eligible for many advanced photonics and optoelectronics devices such as ultrafast optical switching, optical modulator, parametric amplifier to name some. In this work, Ternary 2D GeSeTe nanosheets were synthesized employing facile LPE method, followed by extensive characterization have been conducted to comprehend various features of the prepared nanosheets such as thickness, optical absorption etc. Then, the NLO responses of the prepared nanosheets under NIR regime have been realized employing Zscan methods. The obtained nonlinear absorption coefficient varies from -73 ~ -4.5 cm/GW and -220 ~ -35 cm/GW at 1062 nm and 1560 nm wavelengths respectively indicating superior SA characteristics of GeSeTe nanosheets. The sample nanosheets switched its nonlinear absorption from SA to RSA with increased input intensity enabling potential opportunities for GeSeTe in optical limiting devices. Furthermore, the nonlinear refraction n₂ was recorded to be -9.5×10^{- 4} cm²/GW and -5×10^-4 cm²/GW at 1062 nm and 1560 nm respectively. To the authors' best knowledge, it is the very first time the NLO responses of GeSeTe nanosheets have been investigated and the achieved responses confirms the superior NLO features of GeSeTe that could be widely utilized in various photonics and optoelectronics devices.

Proceedings Article | 12 March 2024 Presentation + Paper

All van der Waals photodetector for ultralow dark current

Tawsif Alam, Sumaiya Hani, Safayet Ahmed, Y. Tsang

Proceedings Volume 12888, 128880A (2024) https://doi.org/10.1117/12.3017997

KEYWORDS: Photodetectors, Dark current, Light sources and illumination, Heterojunctions, Ultraviolet radiation, Photocurrent, Signal detection, Metals, Graphene

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Modern optoelectronic technologies rely heavily on UV photodetectors, which transform UV light stimuli into electrical signals and are used to measure UV radiation levels useful in military communication, medicine and biology. In this work, we report a novel approach to mitigate dark current in Gr-GaS heterojunction by utilizing van der Waals contacted Au electrodes. The all van der Waals photodetector shows self-powered characteristics with rectification ratio of ~10², sub femto ampere dark currents and excellent photo response properties under illumination at 375nm. With detection ability of sub microwatt per square centimeter light of 375 nm at zero bias voltage, the device shows a self-powered responsivity of 16.21mA/W and specific detectivity of 2.12X10¹² Jones with appreciable response times (rise/ fall) of 201.99ms/220.44ms with a linear dynamic range of 53.15dB. Such high-performance Gr-GaS-Au all van der Waals UV photodetector presented in this work is comparable to previously reported results, suggesting that it has great potential for UV-A band detection for weak light signals.

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