Imperial College London

DrDhruvSaxena

Faculty of Natural SciencesDepartment of Physics

Research Associate
 
 
 
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816Blackett LaboratorySouth Kensington Campus

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Summary

 

Publications

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20 results found

Ta VD, Saxena D, Caixeiro S, Sapienza Ret al., 2020, Flexible and tensile microporous polymer fibers for wavelength-tunable random lasing, Nanoscale, Vol: 12, Pages: 12357-12363, ISSN: 2040-3364

Polymer micro-/nanofibers, due to their low-cost and mechanical flexibility, are attractive building blocks for developing lightweight and flexible optical circuits. They are also versatile photonic materials for making various optical resonators and lasers, such as microrings, networks and random lasers. In particular, for random lasing architectures, the demonstrations to-date have mainly relied on fiber bundles whose properties are hard to tune post-fabrication. Here, we demonstrate the successful implementation of an inverted photonic glass structure with monodisperse pores of 1.28 μm into polymer fibers with diameter ranging from 10 to 60 μm. By doping organic dye molecules into this structure, individual fibers can sustain random lasing under optical pulse excitation. The dependence of lasing characteristics, including lasing spectrum and lasing threshold on fiber diameter are investigated. It is found that the lasing emission red-shifts and the threshold decreases with increasing fiber diameter. Furthermore, owing to the mechanical flexibility, the lasing properties can be dynamically changed upon stretching, leading to a wavelength-tunability of 5.5 nm. Our work provides a novel architecture for random lasers which has the potential for lasing tunability and optical sensing.

Journal article

Septiadi D, Barna V, Saxena D, Sapienza R, Genovese D, De Cola Let al., 2020, Biolasing from individual cells in a low-Q resonator enables spectral fingerprinting, Advanced Optical Materials, Vol: 8, Pages: 1-8, ISSN: 2195-1071

Lasing from cells has recently been subject of thorough investigation because of the potential for sensitive and fast biosensing. Yet, lasing from individual cells has been studied in high‐quality resonators, resulting in limited dependence of the lasing properties on the cellular microenvironment. Here, lasing is triggered by cells floating in a low quality factor resonator composed of a disposable poly(methyl methacrylate) (PMMA) cell counting‐slide, hence in absence of conventional high‐reflectivity optical cavities. The exceptional spectral narrowing and the steep slope increase in the input–output energy diagram prove occurrence of laser action in presence of cells. The observed biolasing is an intrinsically dynamic signal, with large fluctuations in intensity and spectrum determined by the optical properties of the individual cell passing through the pump beam. Numerical simulations of the scattering efficiency rule out the possibility of optical feedback from either WGM (whispering gallery mode) or multiple scattering within the cell, and point to the enhanced directional scattering field as the crucial contribution of cells to the laser action. Finally, principal component analysis of lasing spectra measured from freely diffusing cells yields spectral fingerprints of cell populations, which allows discriminating cancer from healthy Rattus glial cells with high degree of confidence.

Journal article

Zhang Y, Davis G, Fonseka HA, Velichko A, Gustafsson A, Godde T, Saxena D, Aagesen M, Parkinson PW, Gott JA, Huo S, Sanchez AM, Mowbray DJ, Liu Het al., 2019, Highly Strained III-V-V Coaxial Nanowire Quantum Wells with Strong Carrier Confinement., ACS Nano, Vol: 13, Pages: 5931-5938

Coaxial quantum wells (QWs) are ideal candidates for nanowire (NW) lasers, providing strong carrier confinement and allowing close matching of the cavity mode and gain medium. We report a detailed structural and optical study and the observation of lasing for a mixed group-V GaAsP NW with GaAs QWs. This system offers a number of potential advantages in comparison to previously studied common group-V structures ( e. g., AlGaAs/GaAs) including highly strained binary GaAs QWs, the absence of a lower band gap core region, and deep carrier potential wells. Despite the large lattice mismatch (∼1.7%), it is possible to grow defect-free GaAs coaxial QWs with high optical quality. The large band gap difference results in strong carrier confinement, and the ability to apply a high degree of compressive strain to the GaAs QWs is also expected to be beneficial for laser performance. For a non-fully optimized structure containing three QWs, we achieve low-temperature lasing with a low external (internal) threshold of 20 (0.9) μJ/cm2/pulse. In addition, a very narrow lasing line width of ∼0.15 nm is observed. These results extend the NW laser structure to coaxial III-V-V QWs, which are highly suitable as the platform for NW emitters.

Journal article

Zhang Y, Saxena D, Aagesen M, Liu Het al., 2019, Toward electrically driven semiconductor nanowire lasers., Nanotechnology, Vol: 30

Semiconductor nanowire (NW) lasers are highly promising for making new-generation coherent light sources with the advantages of ultra-small size, high efficiency, easy integration and low cost. Over the past 15 years, this area of research has been developing rapidly, with extensive reports of optically pumped lasing in various inorganic and organic semiconductor NWs. Motivated by these developments, substantial efforts are being made to make NW lasers electrically pumped, which is necessary for their practical implementation. In this review, we first categorize NW lasers according to their lasing wavelength and wavelength tunability. Then, we summarize the methods used for achieving single-mode lasing in NWs. After that, we review reports on lasing threshold reduction and the realization of electrically pumped NW lasers. Finally, we offer our perspective on future improvements and trends.

Journal article

Gaio M, Saxena D, Bertolotti J, Pisignano D, Camposeo A, Sapienza Ret al., 2019, A nanophotonic laser on a graph, Nature Communications, ISSN: 2041-1723

Nanophotonic architectures for classical and quantum optical technology canboost light-matter interaction via sculpturing the optical modes, formingcavities and designing long-range propagation channels. Conventional photonicschemes minimise multiple scattering to realise a miniaturised version ofmacroscopic beam-splitters, interferometers and optical cavities for lightpropagation and lasing. Here instead, we introduce a nanophotonic network builtfrom multiple paths and interference, to control and enhance light-matterinteraction via light localisation beyond single scattering. The network isbuilt from a mesh of subwavelength waveguides, and can sustain localised modesand mirror-less light trapping stemming from interference over hundreds ofnodes. When optical gain is added, these modes can easily lase, reaching$\sim$100 pm linewidths. We introduce a graph solution to the Maxwell'sequation which describes light on the network, and predicts lasing action. Inthis framework, the network optical modes can be designed via the networkconnectivity and topology, and lasing can be tailored and enhanced by thenetwork shape. Nanophotonic networks pave the way for new laser devicearchitectures, which can be used for sensitive biosensing and on-chip opticalinformation processing.

Journal article

Alanis JA, Lysevych M, Burgess T, Saxena D, Mokkapati S, Skalsky S, Tang X, Mitchell P, Walton AS, Tan HH, Jagadish C, Parkinson Pet al., 2019, Optical Study of p-Doping in GaAs Nanowires for Low-Threshold and High-Yield Lasing, NANO LETTERS, Vol: 19, Pages: 362-368, ISSN: 1530-6984

Journal article

Parkinson P, Alanis JA, Peng K, Saxena D, Mokkapati S, Jiang N, Fu L, Tan HH, Jagadish Cet al., 2018, Modal refractive index measurement in nanowire lasers-a correlative approach, NANO FUTURES, Vol: 2

Journal article

Alanis JA, Saxena D, Mokkapati S, Jiang N, Peng K, Tang X, Fu L, Tan HH, Jagadish C, Parkinson Pet al., 2017, Large-Scale Statistics for Threshold Optimization of Optically Pumped Nanowire Lasers, NANO LETTERS, Vol: 17, Pages: 4860-4865, ISSN: 1530-6984

Journal article

Saxena D, Jiang N, Yuan X, Mokkapati S, Guo Y, Tan HH, Jagadish Cet al., 2016, Design and Room-Temperature Operation of GaAs/AlGaAs Multiple Quantum Well Nanowire Lasers, NANO LETTERS, Vol: 16, Pages: 5080-5086, ISSN: 1530-6984

Journal article

Burgess T, Saxena D, Mokkapati S, Li Z, Hall CR, Davis JA, Wang Y, Smith LM, Fu L, Caroff P, Tan HH, Jagadish Cet al., 2016, Doping-enhanced radiative efficiency enables lasing in unpassivated GaAs nanowires, NATURE COMMUNICATIONS, Vol: 7, ISSN: 2041-1723

Journal article

Saxena D, Wang F, Gao Q, Mokkapati S, Tan HH, Jagadish Cet al., 2015, Mode Profiling of Semiconductor Nanowire Lasers, NANO LETTERS, Vol: 15, Pages: 5342-5348, ISSN: 1530-6984

Journal article

Mokkapati S, Saxena D, Jiang N, Li L, Tan HH, Jagadish Cet al., 2015, An Order of Magnitude Increase in the Quantum Efficiency of (AI)GaAs Nanowires Using Hybrid Photonic-Plasmonic Modes, NANO LETTERS, Vol: 15, Pages: 307-312, ISSN: 1530-6984

Journal article

Gao Q, Saxena D, Wang F, Fu L, Mokkapati S, Guo Y, Li L, Wong-Leung J, Caroff P, Tan HH, Jagadish Cet al., 2014, Selective-Area Epitaxy of Pure Wurtzite InP Nanowires: High Quantum Efficiency and Room-Temperature Lasing, NANO LETTERS, Vol: 14, Pages: 5206-5211, ISSN: 1530-6984

Journal article

Mokkapati S, Saxena D, Jiang N, Tan HH, Jagadish Cet al., 2014, Plasmonic cavities for increasing the radiative efficiency of GaAs nanowires, Conference on Optoelectronic and Microelectronic Materials and Devices (COMMAD), Publisher: IEEE, Pages: 244-245, ISSN: 1097-2137

Conference paper

Mokkapati S, Saxena D, Nian-Jiang, Gao Q, Tan HH, Jagadish Cet al., 2014, III-V semiconductor nanowire lasers, 24th IEEE International Semiconductor Laser Conference (ISLC), Publisher: IEEE COMPUTER SOC, Pages: 217-218, ISSN: 2326-5442

Conference paper

Saxena D, Mokkapati S, Parkinson P, Jiang N, Gao Q, Tan HH, Jagadish Cet al., 2013, Optically pumped room-temperature GaAs nanowire lasers, NATURE PHOTONICS, Vol: 7, Pages: 963-968, ISSN: 1749-4885

Journal article

Tan HH, Jiang N, Saxena D, Lee YH, Mokkapati S, Fu L, Gao Q, Joyce HJ, Jagadish Cet al., 2013, III-V Nanowires for Optoelectronic Applications, Symposium on Semiconductors, Dielectrics, and Metals for Nanoelectronics 11 held during the 224th Meeting of the Electrochemical-Society, Publisher: ELECTROCHEMICAL SOC INC, Pages: 93-98, ISSN: 1938-5862

Conference paper

Tan HH, Jiang N, Lee YH, Saxena D, Parkinson P, Gao Q, Fu L, Jagadish Cet al., 2012, III-V nanowires for optoelectronic applications

The growth of III-V semiconductor core-shell nanowires by Au-catalyzed metal organic chemical vapor deposition is described. The effect of growth conditions on the properties of the nanowires is discussed. Results nanowire solar cells and lasers are also presented. © 2012 IEEE.

Conference paper

Wang H, Parkinson P, Tian J, Saxena D, Mokkapati S, Gao Q, Prasai P, Fu L, Karouta F, Tan HH, Jagadish Cet al., 2012, Optoelectronic properties of GaAs nanowire photodetector, Conference on Optoelectronic and Microelectronic Materials and Devices (COMMAD), Publisher: IEEE, Pages: 139-140, ISSN: 1097-2137

Conference paper

Saxena D, Mokkapati S, Tan HH, Jagadish Cet al., 2012, Designing single GaAs nanowire lasers, Conference on Optoelectronic and Microelectronic Materials and Devices (COMMAD), Publisher: IEEE, Pages: 101-102, ISSN: 1097-2137

Conference paper

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