@misc{polash_smirnov_vashaee_2023, title={Electron spin resonance in emerging spin-driven applications: Fundamentals and future perspectives}, volume={10}, ISSN={["1931-9401"]}, url={https://doi.org/10.1063/5.0072564}, DOI={10.1063/5.0072564}, abstractNote={Spin, the intrinsic angular momentum of an electron, is increasingly being recognized as a versatile tool in the development of next-generation technologies, including quantum computing, sensing, and communication, which exploit quantum phenomena. The burgeoning theoretical understanding coupled with technological advancements have catalyzed research efforts aimed at controlling and manipulating the optical, electrical, magnetic, and thermal properties of materials through the modulation of spin states. Among the myriad of techniques available for investigating these spin-dependent properties, Electron Spin Resonance (ESR), sometimes referred to as electron paramagnetic resonance, stands out as one of the most direct and potent methods to probe electron spin dynamics irrespective of the material environment. ESR furnishes insightful data on the states of individual spins and clusters, spin coherence via relaxation time measurements, and inter-spin distances from spin–spin interaction measurements. Additionally, ESR facilitates the manipulation of spin systems by tailoring the Zeeman energy through the modulation of the external magnetic field, and critically, by the remote manipulation of spins via the application of microwave pulses at resonance frequencies. Modern ESR experimental setups are versatile and can be employed across a wide temperature spectrum—from a few Kelvin, where quantum effects are pronounced, to room temperature and beyond. This adaptability enhances the utility of ESR in investigating the spin-dependent properties in condensed matter systems. Notwithstanding the tremendous potential and advantages that ESR offers, it remains underutilized, especially when compared to inelastic neutron scattering (INS) and nuclear magnetic resonance, despite the latter being more expensive and INS being less accessible. In this review, we elucidate the fundamental principles of ESR, with an emphasis on magnetic and spin interactions in solids, and explore the potential of ESR in advancing the understanding of spin properties across a diverse array of materials science disciplines. We commence with a concise introduction to spin-related physics, followed by the application of ESR in characterizing spin systems. As such, this review aims to serve as a valuable resource for a broad audience, ranging from novices to experts, who are keen on unraveling spin phenomena and dynamics in materials science and condensed matter physics.}, number={4}, journal={APPLIED PHYSICS REVIEWS}, author={Polash, Md Mobarak Hossain and Smirnov, Alex I. and Vashaee, Daryoosh}, year={2023}, month={Dec} }
 @article{moseley_taddei_yan_mcguire_calder_polash_vashaee_zhang_zhao_parker_et al._2022, title={Giant doping response of magnetic anisotropy in MnTe}, volume={6}, ISSN={["2475-9953"]}, url={https://doi.org/10.1103/PhysRevMaterials.6.014404}, DOI={10.1103/PhysRevMaterials.6.014404}, abstractNote={The authors show that minuscule amounts of Li suffice to tune antiferromagnetic MnTe from an easy-plane to easy-axis material. Upon heating towards the N\'eel temperature of 307 K, the spins do not gradually rotate back to a planar orientation, and instead maintain their axial orientation up to a relatively high temperature of 260 K, before quickly switching back to a planar orientation and crossing into the paramagnetic phase. Calculations indicate MnTe bears two competing magnetic ground states which can be manipulated by slightly shifting the Fermi level via Li-doping. Easy manipulation of the spins in MnTe could have significant implications for future spintronic devices and materials.}, number={1}, journal={PHYSICAL REVIEW MATERIALS}, author={Moseley, Duncan H. and Taddei, Keith M. and Yan, Jiaqiang and McGuire, Michael A. and Calder, Stuart and Polash, M. M. H. and Vashaee, Daryoosh and Zhang, Xiaofan and Zhao, Huaizhou and Parker, David S. and et al.}, year={2022}, month={Jan} }
 @article{polash_vashaee_2021, title={Anomalous Thermoelectric Transport Properties of Fe-Rich Magnetic FeTe}, volume={15}, ISSN={["1862-6270"]}, url={https://doi.org/10.1002/pssr.202100231}, DOI={10.1002/pssr.202100231}, abstractNote={The interplay between magnetism and quantum effects has motivated several thermoelectric studies on iron‐telluride yet with little insight on the anomalous features in transport properties near magnetostructural transition temperature (≈70 K). A detailed investigation is carried out on Fe1.1Te by characterizing magnetic, heat capacity, galvanomagnetic, and thermoelectric transport properties to understand the electronic, magnetic, and structural origin of those anomalies. The magnetic susceptibility indicates a bicollinear stripe and short‐range ordering in the antiferromagnetic and paramagnetic domains, respectively. Hall conductivity and transverse magnetoresistance reveal a multicarrier transport impacted by spin fluctuations and magnons. Contributions from phonon‐drag and magnon‐drag are evaluated to understand the origin of the broad peak in antiferromagnetic thermopower. The peak at ≈50 K and the insignificant entropy contribution from the magnonic heat capacity support the phonon‐drag as the origin. The field‐dependent enhancement of thermal conductivity must be associated with field‐dependent spin‐phonon coupling modification. The field‐induced thermopower reduction can be attributed to the suppression of magnons or paramagnons, as evidenced by the magnetic susceptibility data. Above 70 K, the thermal conductivity drops sharply due to the structural change modifying phonon modes. Understanding these properties originated from the spin, and quantum effects are instrumental for designing high‐performance spin‐driven thermoelectrics.}, number={10}, journal={PHYSICA STATUS SOLIDI-RAPID RESEARCH LETTERS}, publisher={Wiley}, author={Polash, Md Mobarak Hossain and Vashaee, Daryoosh}, year={2021}, month={Aug} }
 @article{polash_biswas_alam_2021, title={Comprehensive optimization of electronic and optical properties of polar III-nitride laser}, volume={127}, ISSN={["1432-0649"]}, url={https://doi.org/10.1007/s00340-021-07578-w}, DOI={10.1007/s00340-021-07578-w}, number={3}, journal={APPLIED PHYSICS B-LASERS AND OPTICS}, publisher={Springer Science and Business Media LLC}, author={Polash, Md Mobarak Hossain and Biswas, Saumya and Alam, M. Shah}, year={2021}, month={Mar} }
 @article{polash_vashaee_2021, title={Erratum: Magnon-bipolar carrier drag thermopower in antiferromagnetic/ferromagnetic semiconductors: Theoretical formulation and experimental evidence [Phys. Rev. B 102, 045202 (2020)]}, url={https://doi.org/10.1103/PhysRevB.103.039902}, DOI={10.1103/PhysRevB.103.039902}, abstractNote={Received 1 January 2021DOI:https://doi.org/10.1103/PhysRevB.103.039902©2021 American Physical SocietyPhysics Subject Headings (PhySH)Research AreasAntiferromagnetismFerromagnetismMagnonsSpin caloritronicsSpin relaxationThermoelectric effectsCondensed Matter, Materials & Applied Physics}, journal={Physical Review B}, author={Polash, Md Mobarak Hossain and Vashaee, Daryoosh}, year={2021}, month={Jan} }
 @article{polash_vashaee_2021, title={Infinite-stage Nernst-Ettingshausen Cryocooler for Practical Applications}, volume={15}, ISSN={["2331-7019"]}, url={https://doi.org/10.1103/PhysRevApplied.15.014011}, DOI={10.1103/PhysRevApplied.15.014011}, abstractNote={Recent developments in Nernst-Ettingshausen (NE) physical phenomena combined with advances in the performance of rare-earth permanent magnets make thermomagnetic (TM) cryocoolers well suited for practical applications. The device performance of a NE cryocooler depends on both the material and the geometric shape of the device. Despite continued progress in TM materials, the optimum shape is still based on a simplified infinite-stage model derived in 1963 by Harman [Adv. Energy Convers. 3(4), 667--676 (1963)]. Harman's model assumes several nonrealistic assumptions, such as temperature-independent material properties and constant current density. We relax such assumptions and derive a fully-temperature-dependent numerical model to accurately solve for the thermomagnetic features of a NE cooler with arbitrary geometry. We correct Harman's analytical function and compare its performance with the performance of devices of various shapes. The corrected shape has a higher coefficient of performance (COP) at higher temperature differentials, which indicates that when the material resistivity is a strong function of the temperature, the corrected infinite-stage device can provide better performance than Harman's geometry. Moreover, the corrected infinite-shape device can provide higher heat flow density under a similar optimum-COP condition. A case study based on a state-of-the-art TM material, $\mathrm{Bi}$-$\mathrm{Sb}$ alloy, is presented, and the critical parameters for designing an efficient thermomagnetic cooler are discussed in detail.}, number={1}, journal={PHYSICAL REVIEW APPLIED}, author={Polash, M. Mobarak Hossain and Vashaee, Daryoosh}, year={2021}, month={Jan} }
 @article{polash_mohaddes_rasoulianboroujeni_vashaee_2021, title={Magnon-drag thermopower in antiferromagnets versus ferromagnets (vol 8, pg 4049, 2020)}, volume={9}, ISSN={["2050-7534"]}, DOI={10.1039/d1tc90030g}, abstractNote={Correction for ‘Magnon-drag thermopower in antiferromagnets versus ferromagnets’ by Md. Mobarak Hossain Polash et al., J. Mater. Chem. C, 2020, 8, 4049–4057, DOI: 10.1039/C9TC06330G.}, number={8}, journal={JOURNAL OF MATERIALS CHEMISTRY C}, author={Polash, Md. Mobarak Hossain and Mohaddes, Farzad and Rasoulianboroujeni, Morteza and Vashaee, Daryoosh}, year={2021}, month={Feb}, pages={2978–2978} }
 @article{polash_vashaee_2021, title={Spin fluctuations yield zT enhancement in ferromagnets}, volume={24}, ISSN={["2589-0042"]}, url={https://doi.org/10.1016/j.isci.2021.103356}, DOI={10.1016/j.isci.2021.103356}, abstractNote={Thermal fluctuation of local magnetization intercoupled with charge carriers and phonons offers a path to enhance thermoelectric performance. Thermopower enhancement by spin fluctuations (SF) has been observed before. However, the crucial evidence for enhancing thermoelectric-figure-of-merit (zT) by SF has not been reported until now. Here we report that the SF leads to nearly 80% zT enhancement in ferromagnetic CrTe near and below TC ∼ 335 K. The ferromagnetism is originated from the collective electronic and localized magnetic moments. The field-dependent transport properties demonstrate the profound impact of SF on the electrons and phonons. Under an external magnetic field, the enhancement in thermopower is suppressed, and the thermal conductivity is enhanced, evidencing the existence of a strong SF. The anomalous thermoelectric transport properties are analyzed based on theoretical models, and a good agreement with experimental data is found. This study contributes to the fundamental understanding of SF for designing high-performance spin-driven thermoelectrics.}, number={11}, journal={ISCIENCE}, publisher={Elsevier BV}, author={Polash, Md Mobarak Hossain and Vashaee, Daryoosh}, year={2021}, month={Nov} }
 @misc{polash_yalameha_zhou_ahadi_nourbakhsh_vashaee_2021, title={Topological quantum matter to topological phase conversion: Fundamentals, materials, physical systems for phase conversions, and device applications}, volume={145}, ISSN={["1879-212X"]}, url={https://doi.org/10.1016/j.mser.2021.100620}, DOI={10.1016/j.mser.2021.100620}, abstractNote={The spin-orbit coupling field, an atomic magnetic field inside a Kramers’ system, or discrete symmetries can create a topological torus in the Brillouin Zone and provide protected edge or surface states, which can contain relativistic fermions, namely, Dirac and Weyl Fermions. The topology-protected helical edge or surface states and the bulk electronic energy band define different quantum or topological phases of matters, offering an excellent prospect for some unique device applications. Device applications of the quantum materials rely primarily on understanding the topological properties, their mutual conversion processes under different external stimuli, and the physical system for achieving the phase conversion. There have been tremendous efforts in finding new topological materials with exotic topological phases. However, the application of the topological properties in devices is still limited due to the slow progress in developing the physical structures for controlling the topological phase conversions. Such control systems often require extreme tuning conditions or the fabrication of complex multi-layered topological structures. This review article highlights the details of the topological phases, their conversion processes, along with their potential physical systems, and the prospective application fields. A general overview of the critical factors for topological phases and the materials properties are further discussed to provide the necessary background for the following sections.}, journal={MATERIALS SCIENCE & ENGINEERING R-REPORTS}, publisher={Elsevier BV}, author={Polash, Md Mobarak Hossain and Yalameha, Shahram and Zhou, Haihan and Ahadi, Kaveh and Nourbakhsh, Zahra and Vashaee, Daryoosh}, year={2021}, month={Jul} }
 @article{polash_moseley_zhang_hermann_vashaee_2021, title={Understanding and design of spin-driven thermoelectrics}, volume={2}, ISSN={["2666-3864"]}, url={https://doi.org/10.1016/j.xcrp.2021.100614}, DOI={10.1016/j.xcrp.2021.100614}, abstractNote={While progress in thermoelectric materials based on the engineering of electronic and phononic characteristics is reaching a plateau, the addition of the spin degree of freedom has the potential to open a new landscape for alternative thermoelectric materials. Here, we present the concepts, current understanding, and guidelines for designing spin-driven thermoelectrics. We show that the interplay between the spin and heat currents in entropy transport via charge carriers can offer a path to enhance the electronic thermopower. The classical antiferromagnetic semiconductor manganese telluride (MnTe) is chosen as the case study due to its significant spin-mediated thermoelectric properties. We show that, although the spin-disorder scattering reduces the carrier mobility in magnetic materials, spin entropy, magnon, and paramagnon carrier drags can dominate and significantly enhance the thermoelectric power factor, and hence zT. Finally, several guidelines are drawn based on the current understanding for designing high-performance spin-driven thermoelectric materials.}, number={11}, journal={CELL REPORTS PHYSICAL SCIENCE}, publisher={Elsevier BV}, author={Polash, Md Mobarak Hossain and Moseley, Duncan and Zhang, Junjie and Hermann, Raphael P. and Vashaee, Daryoosh}, year={2021}, month={Nov} }
 @article{influence of the order of fabrication sequences on the thermoelectric properties of skutterudite cosb3–cu0.6ni0.4 nanocomposites_2020, url={http://dx.doi.org/10.1016/j.jallcom.2020.156188}, DOI={10.1016/j.jallcom.2020.156188}, abstractNote={Nanocomposite samples of CoSb3-xCu0.6Ni0.4 (x = 1, 3.5, 6, and 9 wt%) were fabricated through two different approaches to understand the influence of fabrication processes on the thermoelectric properties of CoSb3 skutterudite. CoSb3 matrix and Cu0.6Ni0.4 nanoalloy were synthesized separately via hydrothermal procedures. The mixtures of as-hydrothermally synthesized powders were prepared and annealed in the first method, while in the second fabrication route, CoSb3 powders were initially annealed, followed by mixing with Cu0.6Ni0.4 and annealing of the composite at the same conditions. The results showed improved electrical conductivity of CoSb3 compounds, which is consistent with the systematic increase of the carrier concentration upon increasing the Cu0.6Ni0.4 content. The grain boundary potential barrier mechanism was used to describe the influence of Cu0.6Ni0.4 nanoalloy on the height of the energy barrier of CoSb3-xCu0.6Ni0.4, as compared with that of pristine CoSb3 synthesized using the similar hydrothermal method. The onset of bipolar thermopower reduction is shifted to higher temperatures; however, the room temperature thermopower is reduced upon increasing the content of Cu0.6Ni0.4 nanoinclusions. The sample containing 1 wt% of Cu0.6Ni0.4 fabricated through the first fabrication procedure showed the highest zT value at ∼550 K.}, journal={Journal of Alloys and Compounds}, year={2020}, month={Dec} }
 @article{polash_rasoulianboroujeni_vashaee_2020, title={Magnon and spin transition contribution in heat capacity of ferromagnetic Cr-doped MnTe: Experimental evidence for a paramagnetic spin-caloritronic effect}, url={https://doi.org/10.1063/5.0011887}, DOI={10.1063/5.0011887}, abstractNote={We present experimental evidence for the simultaneous existence of the magnons and spin-state transition contributions to the heat capacity in ferromagnetic (FM) Cr-doped MnTe (Tc ∼ 280 K), where the magnon heat capacity is attributed to the observed magnon-bipolar carrier-drag thermopower. The pristine antiferromagnetic (AFM) MnTe shows only a magnon-induced peak in the heat capacity near the Néel temperature, TN ∼ 307 K. However, Cr-doped MnTe shows a magnon-contributed heat capacity peak at ∼293 K with an additional peak in the deep paramagnetic domain near 780 K. Temperature-dependent magnetic susceptibility reveals that Cr-doping initially creates low-spin (LS) state Mn2+ ions into MnTe near and below TN due to a higher crystal field induced by Cr ions. Above 400 K, LS Mn2+ ions start converting into high-spin (HS) Mn2+ ions. The LS-to-HS transition of Mn2+ leads to an excess entropy and hence excess heat capacity contribution in the system. Temperature-dependent X-ray diffraction (XRD) and magnetic field-dependent susceptibility (M-H) confirmed no presence of any structural changes and magnetic polaron, respectively. Both XRD and M-H ensure that the peak of the heat capacity in the paramagnetic domain is originated solely by the spin-state transition. The heat capacity vs temperature was calculated to explain the contribution of each component, including the ones due to the phonons, magnons, spin-transition, Schottky anomaly, and lattice dilation. With the recent advances in spin-caloritronics extending the spin-based effects from magnetic to paramagnetic materials, the data from the heat capacity can play a crucial role to probe the presence of different phenomena, such as paramagnon-carrier-drag and spin-entropy thermopowers.}, journal={Applied Physics Letters}, author={Polash, Md Mobarak Hossain and Rasoulianboroujeni, Morteza and Vashaee, Daryoosh}, year={2020}, month={Jul} }
 @article{polash_vashaee_2020, title={Magnon-bipolar carrier drag thermopower in antiferromagnetic/ferromagnetic semiconductors: Theoretical formulation and experimental evidence}, url={https://doi.org/10.1103/PhysRevB.102.045202}, DOI={10.1103/PhysRevB.102.045202}, abstractNote={Quantized spin-wave known as magnon, a bosonic quasiparticle, can drag electrons or holes via s-d exchange interaction and boost the thermopower over the conventional diffusive thermopower. P-type magnon-drag thermopower has been observed in both ferromagnetic and antiferromagnetic metallic and degenerate semiconductors. However, it has been less reported for intrinsic or $n$-type magnetic semiconductors; therefore, the impact of magnon-bipolar carrier drag on thermopower has remained unexplored. Here, a theoretical model for magnon-bipolar carrier drag thermopower is derived based on the magnon-carrier interaction lifetimes. The model predicts that the bipolar carrier drag thermopower becomes independent of both the carrier and magnon relaxation times. A proof of concept experiment is presented that confirms this prediction. We also report the observation of magnon-carrier drag thermopower in n-type and intrinsic ferromagnetic semiconductors experimentally. The p-type antiferromagnetic MnTe is doped with different amounts of Cr to produce nondegenerate and n-type semiconductors of various carrier concentrations. Cr dopants have a donor nature and create ferromagnetic-antiferromagnetic clusters due to the $\mathrm{C}{\mathrm{r}}^{3+}$ oxidation state. Heat capacity measurements confirm the presence of magnons in Cr-doped MnTe. It is shown that the magnon-drag thermopower is significantly reduced for 3%--5% Cr-doped samples due to bipolar drag effects and becomes negative for 14% and 20% Cr-doped MnTe due to dominant magnon-electron drag thermopower.}, journal={Physical Review B}, author={Polash, Md Mobarak Hossain and Vashaee, Daryoosh}, year={2020}, month={Jul} }
 @article{polash_mohaddes_rasoulianboroujeni_vashaee_2020, title={Magnon-drag thermopower in antiferromagnets versus ferromagnets}, volume={8}, url={https://doi.org/10.1039/C9TC06330G}, DOI={10.1039/C9TC06330G}, abstractNote={Multi magnon interaction with carriers limits the magnon lifetime in FMs compared to AFMs. The longer lifetime, double degeneracy, and higher group velocity of magnons in AFMs generally lead to higher first-order magnon-carrier drag thermopower.}, number={12}, journal={Journal of Materials Chemistry C}, publisher={Royal Society of Chemistry (RSC)}, author={Polash, Md. Mobarak Hossain and Mohaddes, Farzad and Rasoulianboroujeni, Morteza and Vashaee, Daryoosh}, year={2020}, pages={4049–4057} }
 @misc{nozariasbmarz_collins_dsouza_polash_hosseini_hyland_liu_malhotra_ortiz_mohaddes_et al._2020, title={Review of wearable thermoelectric energy harvesting: From body temperature to electronic systems}, volume={258}, ISSN={["1872-9118"]}, url={https://publons.com/publon/30967440/}, DOI={10.1016/j.apenergy.2019.114069}, abstractNote={Global demand for battery-free metrics and health monitoring devices has urged leading research agencies and their subordinate centers to set human energy harvesting and self-powered wearable technologies as one of their primary research objectives. After an overview of wearables market trends, different active and passive methods of body energy harvesting for powering low-consumption electronic devices are introduced, and challenges of device fabrication are discussed. The discussion continues with the primary emphasis on thermoelectric generators for body heat harvesting. The physiological aspects of the human body involved in heat generation are elaborated. System requirements and the influence of different parameters on the performance of thermoelectric generators are studied at the material, device, and system levels. Finally, the advancements in the development of rigid and flexible thermoelectric generators for wearable and textile integration are presented.}, journal={APPLIED ENERGY}, author={Nozariasbmarz, Amin and Collins, Henry and Dsouza, Kelvin and Polash, Mobarak Hossain and Hosseini, Mahshid and Hyland, Melissa and Liu, Jie and Malhotra, Abhishek and Ortiz, Francisco Matos and Mohaddes, Farzad and et al.}, year={2020}, month={Jan} }
 @article{zheng_lu_polash_rasoulianboroujeni_liu_manley_deng_sun_chen_hermann_et al._2019, title={Paramagnon drag in high thermoelectric figure of merit Li-doped MnTe}, volume={5}, ISSN={["2375-2548"]}, url={https://doi.org/10.1126/sciadv.aat9461}, DOI={10.1126/sciadv.aat9461}, abstractNote={Neutrons spot magnetic fluctuations that propel charges in a novel class of paramagnetic thermoelectrics.}, number={9}, journal={SCIENCE ADVANCES}, publisher={American Association for the Advancement of Science (AAAS)}, author={Zheng, Y. and Lu, T. and Polash, Md M. H. and Rasoulianboroujeni, M. and Liu, N. and Manley, M. E. and Deng, Y. and Sun, P. J. and Chen, X. L. and Hermann, R. P. and et al.}, year={2019}, month={Sep} }
 @inproceedings{zheng_lu_polash_rasoulianboroujeni_liu_manley_deng_sun_chen_hermann_et al._2019, title={Paramagnon drag yields a high thermoelectric figure of merit in Li-doped MnTe}, booktitle={APS March Meeting Abstracts}, author={Zheng, Yuanhua and Lu, Tianqi and Polash, Md and Rasoulianboroujeni, Morteza and Liu, Ning and Manley, Michael and Deng, Yuan and Sun, Peijie and Chen, Xiaolong and Hermann, Raphael and et al.}, year={2019} }
 @inproceedings{vashaee_polash_perelygin_rasoulianboroujeni_zheng_lu_liu_manley_hermann_smirnov_et al._2019, title={Spin Effects Making zT > 1}, booktitle={APS March Meeting Abstracts}, author={Vashaee, Daryoosh and Polash, Md Mobarak Hossain and Perelygin, Vladislav and Rasoulianboroujeni, Morteza and Zheng, Yuanhua and Lu, Tianqi and Liu, Ning and Manley, Michael and Hermann, Raphael and Smirnov, Alex and et al.}, year={2019} }
 @article{polash_alam_biswas_2018, title={Design and analysis of InN - In0.25Ga0.75N single quantum well laser for short distance communication wavelength}, volume={57}, ISSN={["1560-2303"]}, url={https://publons.com/publon/17138082/}, DOI={10.1117/1.oe.57.3.036110}, abstractNote={Abstract. A single quantum well semiconductor laser based on wurtzite-nitride is designed and analyzed for short distance communication wavelength (at around 1300 nm). The laser structure has 12 Å well layer of InN, 15 Å barrier layer of In0.25Ga0.75N, and 54 Å separate confinement heterostructure layer of GaN. To calculate the electronic characteristics of the structure, a self-consistent method is used where Hamiltonian with effective mass approximation is solved for conduction band while six-bands Hamiltonian matrix with k  ·  p formalism including the polarization effect, valence-band mixing effect, and strain effect is solved for valence band. The interband optical transition elements, optical gain, differential gain, radiative current density, spontaneous emission rate, and threshold characteristics have been calculated. The wave function overlap integral is found to be 45.93% for TE-polarized structure. Also, the spontaneous emission rate is found to be 6.57  ×  1027  s  −  1 cm  −  3 eV  −  1 at 1288.21 nm with the carrier density of 5  ×  1019  cm  −  3. Furthermore, the radiative current density and the radiative recombination rate are found to be 121.92  A cm  −  2 and 6.35  ×  1027  s  −  1 cm  −  3, respectively, while the TE-polarized optical gain of the structure is 3872.1  cm  −  1 at 1301.7 nm.}, number={3}, journal={OPTICAL ENGINEERING}, author={Polash, Md Mobarak Hossain and Alam, M. Shah and Biswas, Saumya}, year={2018}, month={Mar} }
 @article{characterization of inn-in0.25ga0.n-75 quantum well laser with in(0.4)ai(0.6)n layers for 1300 nm band_2016, url={https://publons.com/publon/30967589/}, DOI={10.1557/ADV.2016.351}, abstractNote={A wurtzite-strained nitride Quantum Well Laser has been characterized for short distance communication wavelength. InN and In_0.25Ga_0.75N have been chosen as well material and barrier material respectively with In_0.4Al_0.6N SCH layers at the end of barrier layers to improve the carrier and photon confinement within the active region. This structure shows less compressive strain (7.33%) with respect to previously proposed structure which makes the structure more suitable for fabrication. To obtain the electronic band structure, self-consistent method with k.p formalism has been performed where valence band mixing effect, strain effect and spontaneous and piezoelectric polarization effect has been included. From the electronic characteristics, the optical properties have been performed with numerical model. From the optical properties, the structure has been found as TE polarized with C1-HH1, C1-LH1, C2-HH1 and C2-LH1 dominating transition elements. From the performance of the numerical model, 4731.98 cm^−1 optical gain for TE polarization at 1315.5 nm emission wavelength and 8.017×10^27 cm^−3s^−1eV^−1 spontaneous emission rate at 1301.7nm wavelength have been found for 12Å well width, 17Å barrier width and 52Å SCH layer width at 5×10^19 cm^−3 carrier density. The obtained properties have been shown a good agreement with previously published works.}, journal={MRS Advances}, year={2016} }
 @article{characterization of inn - in0.25ga0.75n quantum well laser structure for 1330 nm wavelength_2015, url={https://publons.com/publon/30971214/}, DOI={10.1149/06912.0071ECST}, abstractNote={A nitride based wurtzite-strained QW laser with 12Å InN well layer, 15Å In0.25Ga0.75N barrier layer and GaN SCH layer has been designed and characterized at 1330nm wavelength. To determine the electronic properties, a self-consistent method with 6-bands k.p formalism considering valence-band mixing effect, strain and polarization effect followed by Poisson's equation has been used. The interband momentum matrix elements, optical gain, spontaneous emission rate, and radiative current density have been calculated to analyze the optical properties of the laser. Due to the strain effect, the wave-function overlap integral was obtained as 43.27%. The structure is TE polarized with C1-HH1 and C1-LH1 dominating transitions, while the spontaneous emission rate per energy interval per unit volume was 7.21×1027 s-1cm-3eV-1 at 1329.55nm. Furthermore, the radiative recombination rate and the radiative current density were 7.77×1029 s-1cm-3 and 149.19 Acm-2, respectively. The optical gain of the structure is 5261.52cm-1 at 1336.7nm for TE-polarization.}, journal={ECS Transactions}, year={2015} }
 @inproceedings{investigation of performance characteristics of an al0.8ga0.2n-delta-gan qw laser considering structural parameters_2015, url={https://publons.com/publon/30967569/}, DOI={10.1109/ICTP.2015.7427936}, abstractNote={We have designed Al0.8Ga0.2N-delta-GaN Quantum Well (QW) Laser to investigate the performance characteristics of device like square momentum matrix element at zone center, spontaneous emission rate and optical gain, with structural parameters like delta width, well width, barrier width and injection carrier density. A Self Consistent model using 6-band k.p method incorporating strain effect due to lattice mismatch, valence band mixing effect, carrier screening effect and both spontaneous and piezoelectric polarization effect has been adopted to calculate the electronic properties of the structure. With the variation of the structural parameters, the detail illustration of the variations of the device characteristics are demonstrated in this work. From the investigation, it has been found that the structure shows a maximum optical output of 6636.8 cm-1 at 425nm emission wavelength for 7A delta width, 12A well width, 60A barrier width and 5×1019 cm-3 carrier density at 300K. Detail relationship between the performance parameters of the structure has been elaborated in this work to obtain the conditions for maximum output of the structure. The calculated device properties are compared favourably with the values reported previously in the literature.}, booktitle={IEEE International Conference on Telecommunications and Photonics (ICTP)}, year={2015} }
 @article{optical gain optimization of al0.8ga0.2n-delta-gan quantum well laser in ultraviolet spectra using genetic algorithm_2015, url={https://publons.com/publon/30971212/}, DOI={10.1149/06912.0081ECST}, abstractNote={An AlGaN based quantum well laser with GaN delta layer and AlN barrier layers has been designed and characterized for obtaining electronic and optical characteristics. The band structure was calculated with self-consistent 6-band k.p formalism including valence-band mixing effect, strain and polarization effect. A Genetic Algorithm based optimization has been performed to optimize the optical gain taking well width, delta width and barrier width into consideration. The Optimization of both TE and TM polarized optical gain exhibits good improvement than previously published work. The peak optical gain as obtained in analysis is 3589.5 cm−1 while the peak spontaneous emission rate is 12.94×1028 s-1cm-3eV-1 at 246.89nm for 5×1019cm-3 carrier density. The optimum TE optical gain is found to be 6479.1 cm-1 for 11Å QW with 7Å delta layer at 279nm wavelength and optimum TM gain is found to be 116.95 cm-1 for 20Å QW with 3Å delta layer at 289.8nm wavelength.}, journal={ECS Transactions}, year={2015} }
 @article{design analysis of inn/ingan quantum well laser with gan layers at 1320-1350 nm wavelength_2014, url={https://publons.com/publon/30967570/}, DOI={10.1109/ICEEICT.2014.6919093}, abstractNote={In this work, a nitride based strained single quantum well laser has been designed and characterized at 1330 nm wavelength. Here, InN has been used as well material and InGaN has been used as barrier material along with GaN as separate confinement heterostructure for better carrier and optical confinement. For the analysis of characteristics of the laser system, 6-bands k.p formalism for wurtzite semiconductor has been solved considering band mixing effect, strain due to lattice mismatch, spontaneous and piezoelectric polarization and carrier screening effects. The optical gain and spontaneous emission rate and also the interband momentum matrix elements have been calculated to analyze the optical properties of the designed laser and a good agreement with previously published works is obtained.}, journal={2ND INTERNATIONAL CONFERENCE ON ELECTRICAL ENGINEERING AND INFORMATION COMMUNICATION TECHNOLOGY (ICEEICT)}, year={2014} }
 @article{design of a low cost pc interface six dof robotic arm utilizing recycled materials_2014, url={https://publons.com/publon/30967493/}, DOI={10.1109/ICEEICT.2014.6919073}, abstractNote={In this work, a PC-interfaced low cost robotic arm has been designed which can be integrated with modern robotic-arm based light weight lifting applications. Both manual and PC-based controlling system have been integrated with the robotic arm to make the manipulator use-worthy in maximum applications. This designed robotic arm has six degree of freedom (DOF) which is modeled as four-link, with each joint connected with suitable DC gear-motor. Available parts from local market as well as used up elements from industrial machines and household appliances have been used for the implementation of the manipulator to lower the cost. For controlling the robotic arm, microcontroller based manual controlling system with PWM speed control along with relays has been used and DC gear motor has been integrated with PC based on parallel communication for PC-based controlling system. The weight of the complete structure is only 7.363 kg which is capable of lifting up to 1.5 kg. This designed robotic arm costs only $125 including all prices of recycled and fresh materials which is considerably lower than commercially developed robotic arm with same specifications.}, journal={2ND INTERNATIONAL CONFERENCE ON ELECTRICAL ENGINEERING AND INFORMATION COMMUNICATION TECHNOLOGY (ICEEICT)}, year={2014} }
 @inproceedings{a generalized model using genetic algorithm for optimization of material gain of the active layer of a mqw edge emitting laser with unequal well width_2013, url={https://publons.com/publon/30967577/}, DOI={10.1109/EICT.2014.6777814}, abstractNote={In this work, a computational model for optimization of material gain of the active region of a multiple quantum well (MQW) edge emitting laser (EEL) using genetic algorithm has been developed. Through this optimization procedure, the values of the width of quantum wells (QW), width of barriers, lattice temperature, injection carrier density and number of QWs which are related to material gain of the active region are optimized for optimizing the design of a MQW EEL. For the above mentioned optimization the numerical simulation of the optical gain expression of MQW EEL along with the solution of the Schrodinger's equation has been performed using MATLAB. The developed optimization based design technique has been applied for the design of (i) a 1550 nm In<sub>0.72</sub>Ga<sub>0.28</sub>As<sub>0.82</sub>P<sub>0.18</sub>/In<sub>0.42</sub>Ga<sub>0.58</sub>As<sub>0.82</sub>P<sub>0.18</sub> MQW EEL having 3 QWs and also (ii) for a 1550 nm In<sub>0.72</sub>Ga<sub>0.28</sub>As<sub>0.82</sub>P<sub>0.18</sub>/In<sub>0.42</sub>Ga<sub>0.58</sub>As<sub>0.82</sub>P<sub>0.18</sub> MQW EEL having 5 QWs for testing the validity. The computation indicates clearly that the optimization based computational model works well and can be easily used for the design of MQW EELs.}, booktitle={International Conference on Electrical Information and Communication Technology (EICT)}, year={2013} }
 @inproceedings{an intra-cavity bottom emitting 1325 nm vcsel using gainas / gainp mqws and algainas / inp dbrs for epitaxial fabrication_2012, url={https://publons.com/publon/30967579/}, DOI={10.1109/EDSSC.2012.6482771}, abstractNote={In this paper, a bottom emitting Ga<sub>0.586</sub>In<sub>0.414</sub>As / Ga<sub>0.252</sub>In<sub>0.748</sub>P MQW Intra-cavity Vertical Cavity Surface Emitting Laser (VCSEL) capable of emitting light output at 1325 nm has been designed. After a number of computations of the material gain and band gap energy it has been found that the ternary compound of Ga<sub>0.586</sub>In<sub>0.414</sub>As as the quantum well material and the lattice matched ternary compound material Ga<sub>0.252</sub>In<sub>0.748</sub>P as the barrier material are suitable for operating at 1325 nm. Ga<sub>0.252</sub>In<sub>0.748</sub>P has been used for the 2 SCH layers which is also lattice matched. Si doped Al<sub>0.6</sub>In<sub>0.4</sub>As has been used as the lattice matched p-cladding material and C doped Al<sub>0.5</sub>In<sub>0.5</sub>As has been used as the n-cladding material. The design has been based on building the laser on an InP substrate which is lattice matched with the bottom DBR layers made of lattice matched Al<sub>0.26</sub>Ga<sub>0.21</sub>In<sub>0.53</sub>As / InP (48 pairs). The top DBR structure has been designed using Al<sub>0.26</sub>Ga<sub>0.21</sub>In<sub>0.53</sub>As / InP (80 pairs) which is also lattice matched with the p-cladding material and the active region material. This design is aimed at fabricating the VCSEL using the widely used epitaxial technologies. The performance characteristics of the designed VCSEL show expected performance.}, booktitle={IEEE International Conference on Electron Devices and Solid-State Circuits (EDSSC)}, year={2012} }