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Publications (10 of 21) Show all publications
De Luca, E., Sanatinia, R., Mensi, M., Anand, S. & Swillo, M. (2017). Modal phase matching in nanostructured zincblende semiconductors for second-harmonic generation. In: Optics InfoBase Conference Papers: . Paper presented at CLEO: Applications and Technology, CLEO_AT 2017, 14 May 2017 through 19 May 2017. OSA - The Optical Society
Open this publication in new window or tab >>Modal phase matching in nanostructured zincblende semiconductors for second-harmonic generation
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2017 (English)In: Optics InfoBase Conference Papers, OSA - The Optical Society , 2017Conference paper, Published paper (Refereed)
Abstract [en]

Gallium phosphide nanowaveguide arrays, designed to fulfill the phase matching conditions and field-overlap, are characterized by second-harmonic generation. The bandwidth of 30nm with maximum conversion efficiency of 10-3 is measured for 150fs optical pulses.

Place, publisher, year, edition, pages
OSA - The Optical Society, 2017
Keywords
Gallium phosphide, Harmonic generation, Nonlinear optics, Zinc sulfide, Modal phase matching, Nano-structured, Phase matching conditions, Zincblende semiconductors, Phase matching
National Category
Nano Technology
Identifiers
urn:nbn:se:kth:diva-216568 (URN)10.1364/CLEO_AT.2017.JTu5A.60 (DOI)000427296201312 ()2-s2.0-85020426863 (Scopus ID)9781943580279 (ISBN)
Conference
CLEO: Applications and Technology, CLEO_AT 2017, 14 May 2017 through 19 May 2017
Note

QC 20171108

Available from: 2017-11-08 Created: 2017-11-08 Last updated: 2018-05-30Bibliographically approved
Jaramillo-Fernandez, J., Chavez-Angel, E., Sanatinia, R., Kataria, H., Anand, S., Lourdudoss, S. & Sotomayor-Torres, C. M. (2017). Thermal conductivity of epitaxially grown InP: experiment and simulation. CrystEngComm, 19(14), 1879-1887
Open this publication in new window or tab >>Thermal conductivity of epitaxially grown InP: experiment and simulation
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2017 (English)In: CrystEngComm, ISSN 1466-8033, E-ISSN 1466-8033, Vol. 19, no 14, p. 1879-1887Article in journal (Refereed) Published
Abstract [en]

The integration of III-V optoelectronic devices on silicon is confronted with the challenge of heat dissipation for reliable and stable operation. A thorough understanding and characterization of thermal transport is paramount for improved designs of, for example, viable III-V light sources on silicon. In this work, the thermal conductivity of heteroepitaxial laterally overgrown InP layers on silicon is experimentally investigated using microRaman thermometry. By examining InP mesa-like structures grown from trenches defined by a SiO2 mask, we found that the thermal conductivity decreases by about one third, compared to the bulk thermal conductivity of InP, with decreasing width from 400 to 250 nm. The high thermal conductivity of InP grown from 400 nm trenches was attributed to the lower defect density as the InP micro crystal becomes thicker. In this case, the thermal transport is dominated by phonon-phonon interactions as in a low defect-density monocrystalline bulk material, whereas for thinner InP layers grown from narrower trenches, the heat transfer is dominated by phonon scattering at the extended defects and InP/SiO2 interface. In addition to the nominally undoped sample, sulfur-doped (1 x 10(18) cm(-3)) InP grown on Si was also studied. For the narrower doped InP microcrystals, the thermal conductivity decreased by a factor of two compared to the bulk value. Sources of errors in the thermal conductivity measurements are discussed. The experimental temperature rise was successfully simulated by the heat diffusion equation using the FEM.

Place, publisher, year, edition, pages
ROYAL SOC CHEMISTRY, 2017
Keywords
InP, thermal conductivity
National Category
Chemical Sciences Materials Engineering
Research subject
Materials Science and Engineering
Identifiers
urn:nbn:se:kth:diva-206248 (URN)10.1039/c6ce02642g (DOI)000398401800004 ()2-s2.0-85017004050 (Scopus ID)
Projects
Linnaeus Center in Advanced Optics and Photonics ADOPTVR grant number 349-2007-8664VR grant numbers 2014-5100
Note

QC 20170512

Available from: 2017-05-12 Created: 2017-05-12 Last updated: 2018-01-16Bibliographically approved
De Luca, E., Sanatinia, R., Srinivasan, A. & Swillo, M. (2016). Focused ion beam milling of gallium phosphide nanostructures for photonic applications. Optical Materials Express, 6(2), 587-596
Open this publication in new window or tab >>Focused ion beam milling of gallium phosphide nanostructures for photonic applications
2016 (English)In: Optical Materials Express, ISSN 2159-3930, E-ISSN 2159-3930, Vol. 6, no 2, p. 587-596Article in journal (Refereed) Published
Abstract [en]

We report on the fabrication of gallium phosphide (GaP) nanowaveguides of controlled dimensions, as small as 0.03 μm and aspect ratio in excess of 20, using focused ion beam (FIB) milling. A known limitation of this fabrication process for photonic applications is the formation of gallium droplets on the surface. We demonstrate a post-fabrication step using a pulsed laser to locally oxidize the excess surface gallium on the FIB milled nanostructures. The process significantly reduces the waveguide losses. The surface optical quality of the fabricated GaP nanowaveguides has been evaluated by second-harmonic generation experiments. Surface and bulk contributions to second-order optical nonlinearities have been identified by polarization measurements. The presented method can potentially be applied to other III-V nanostructures to reduce optical losses.

Place, publisher, year, edition, pages
Optical Society of America, 2016
National Category
Nano Technology
Identifiers
urn:nbn:se:kth:diva-182213 (URN)10.1364/OME.6.000587 (DOI)000372039500032 ()2-s2.0-84957555940 (Scopus ID)
Note

QC 20160322

Available from: 2016-02-18 Created: 2016-02-18 Last updated: 2017-11-30Bibliographically approved
Sanatinia, R., Anand, S. & Swillo, M. (2015). Experimental quantification of surface optical nonlinearity in GaP nanopillar waveguides. Optics Express, 23(2), 756-764
Open this publication in new window or tab >>Experimental quantification of surface optical nonlinearity in GaP nanopillar waveguides
2015 (English)In: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 23, no 2, p. 756-764Article in journal (Refereed) Published
Abstract [en]

We report on surface second-order optical nonlinearity in single GaP nanopillars (nanowaveguides). The relative contribution of optical nonlinearity from the surface and the bulk is resolved by mode confinement analysis and polarization measurements. By investigating the thickness of nonlinear region at the surface of nanopillars, we estimated the nonlinear coefficient to be similar to 15 times higher at the surface with respect to the bulk. The presented results are interesting both from the fundamental aspects of light-matter interaction and for future nonlinear nanophotonic devices with smaller footprint.

Keywords
Gallium alloys, Nanostructures, Confinement analysis, Light-matter interactions, Nanophotonic devices, Nonlinear coefficient, Optical nonlinearity, Polarization measurements, Relative contribution, Second order optical nonlinearity
National Category
Nano Technology Atom and Molecular Physics and Optics
Research subject
Physics; Materials Science and Engineering
Identifiers
urn:nbn:se:kth:diva-155198 (URN)10.1364/OE.23.000756 (DOI)000349166100016 ()2-s2.0-84921719961 (Scopus ID)
Funder
Swedish Research Council, 349-2007-8664Swedish Research Council, 621-2013-5811EU, FP7, Seventh Framework Programme, 248855
Note

QC 20150312. Updated from manuscript to article in journal.

Available from: 2014-11-03 Created: 2014-11-03 Last updated: 2017-12-05Bibliographically approved
Dev Choudhury, B., Sahoo, P. K., Sanatinia, R., Andler, G., Anand, S. & Swillo, M. (2015). Surface second harmonic generation from silicon pillar arrays with strong geometrical dependence [Letter to the editor]. Optics Letters, 40(9), 2072-2075
Open this publication in new window or tab >>Surface second harmonic generation from silicon pillar arrays with strong geometrical dependence
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2015 (English)In: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794, Vol. 40, no 9, p. 2072-2075Article in journal, Letter (Refereed) Published
Abstract [en]

We present experimental demonstration and analysis of enhanced surface second harmonic generation (SHG) from hexagonal arrays of silicon pillars. Three sets of Si pillar samples with truncated cone-shaped pillar arrays having periods of 500, 1000, and 2000 nm, and corresponding average diameters of 200, 585 and 1550 nm, respectively, are fabricated by colloidal lithography and plasma dry etching. We have observed strong dependence of SHG intensity on the pillar geometry. Pillar arrays with a 1000 nm period and a 585 nm average diameter give more than a one order of magnitude higher SHG signal compared to the other two samples. We theoretically verified the dependence of SHG intensity on pillar geometry by finite difference time domain simulations in terms of the surface normal E-field component. The enhanced surface SHG light can be useful for nonlinear silicon photonics, surface/interface characterization, and optical biosensing.

Keywords
Spectroscopy, Nanopillars, Interfaces, Photonics, Harmonics, Boundary
National Category
Atom and Molecular Physics and Optics
Research subject
Physics
Identifiers
urn:nbn:se:kth:diva-168380 (URN)10.1364/OL.40.002072 (DOI)000353924600049 ()2-s2.0-84973601640 (Scopus ID)
Funder
Swedish Research Council, 621-2013-5811 349-2007-8664
Note

QC 20150612

Available from: 2015-06-02 Created: 2015-06-02 Last updated: 2017-12-04Bibliographically approved
Jaramillo-Fernandez, J., Ordonez-Miranda, J., Ollier, E., Sanatinia, R., Kataria, H., Chavez-Angel, E., . . . Sotomayor-Torres, C. M. (2015). Tuning of heat transport across thin films of polycrystalline AlN via multiscale structural defects. In: ECS Transactions: . Paper presented at Symposium on Thermoelectric and Thermal Interface Materials 2 - 228th ECS Meeting, 11 October 2015 through 15 October 2015 (pp. 53-64). Electrochemical Society (9)
Open this publication in new window or tab >>Tuning of heat transport across thin films of polycrystalline AlN via multiscale structural defects
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2015 (English)In: ECS Transactions, Electrochemical Society, 2015, no 9, p. 53-64Conference paper, Published paper (Refereed)
Abstract [en]

The effective thermal conductivity of nanocrystalline films of AlN with inhomogeneous microstructure is investigated experimentally and theoretically. This is done by measuring the thermal conductivity of the samples with the 3-omega method and characterizing their microstructure by means of electron microscopy. The relative effect of the microstructure and the interface thermal resistance on the thermal conductivity is quantified through an analytical model. Thermal measurements showed that when the thickness of an AlN film is reduced from 1460 to 270 nm, its effective thermal conductivity decreases from 8.21 to 3.12 WYm-1?K-1, which is two orders of magnitude smaller than its bulk counterpart value. It is shown that both the size effects of the phonon mean free paths and the intrinsic thermal resistance resulting from the inhomogeneous microstructure predominate for thicker films, while the contribution of the interface thermal resistance strengthens as the film thickness is scaled down. The obtained results demonstrate that the structural inhomogeneity in polycrystalline AlN films can be efficiently used to tune their cross- plane thermal conductivity. In addition, thermal conductivity measurements of epitaxially grown InP layers on silicon using Raman spectroscopy are reported.

Place, publisher, year, edition, pages
Electrochemical Society, 2015
Keywords
Interfaces (materials), Microstructure, Nanocrystals, Thermal conductivity of solids, Thermal insulating materials, Thin films, Effective thermal conductivity, Inhomogeneous microstructure, Interface thermal resistance, Nano-crystalline films, Phonon mean free path, Structural inhomogeneities, Thermal conductivity measurements, Thermal measurements, Thermal conductivity
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:kth:diva-181507 (URN)10.1149/06909.0053ecst (DOI)2-s2.0-84946119769 (Scopus ID)9781607685395 (ISBN)
Conference
Symposium on Thermoelectric and Thermal Interface Materials 2 - 228th ECS Meeting, 11 October 2015 through 15 October 2015
Note

QC 20160307

Available from: 2016-03-07 Created: 2016-02-02 Last updated: 2018-01-16Bibliographically approved
Sanatinia, R., Berrier, A., Dhaka, V., P. Perros, A., Huhtio, T., Lipsanen, H. & Anand, S. (2015). Wafer-Scale Self-Organized InP Nanopillars with Controlled Orientation for Photovoltaic Devices. Nanotechnology, 26(41), Article ID 415304.
Open this publication in new window or tab >>Wafer-Scale Self-Organized InP Nanopillars with Controlled Orientation for Photovoltaic Devices
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2015 (English)In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 26, no 41, article id 415304Article in journal (Refereed) Published
Abstract [en]

A unique wafer-scale self-organization process for generation of InP nanopillars is demonstrated, which is based on maskless ion-beam etching (IBE) of InP developed to obtain the nanopillars, where the height, shape, and orientation of the nanopillars can be varied by controlling the processing parameters. The fabricated InP nanopillars exhibit broadband suppression of the reflectance, 'black InP,' a property useful for solar cells. The realization of a conformal p-n junction for carrier collection, in the fabricated solar cells, is achieved by a metalorganic vapor phase epitaxy (MOVPE) overgrowth step on the fabricated pillars. The conformal overgrowth retains the broadband anti-reflection property of the InP nanopillars, indicating the feasibility of this technology for solar cells. Surface passivation of the formed InP nanopillars using sulfur-oleylamine solution resulted in improved solar-cell characteristics. An open-circuit voltage of 0.71 V and an increase of 0.13 V compared to the unpassivated device were achieved.

Place, publisher, year, edition, pages
Institute of Physics Publishing (IOPP), 2015
National Category
Nano Technology
Identifiers
urn:nbn:se:kth:diva-155199 (URN)10.1088/0957-4484/26/41/415304 (DOI)000363433700008 ()26403979 (PubMedID)2-s2.0-84947475230 (Scopus ID)
Funder
EU, FP7, Seventh Framework Programme, 248855Swedish Research Council, 349-2007-8664Swedish Research Council, 621-2014-5078
Note

Updated from manuscript to article in journal.

QC 20160203

Available from: 2014-11-03 Created: 2014-11-03 Last updated: 2017-12-05Bibliographically approved
Sanatinia, R., Westendorp, S., Anand, S. & Swillo, M. (2014). Enhanced second-harmonic generation in GaP nanopillars arrays by modal engineering. In: Optics InfoBase Conference Papers: . Paper presented at CLEO: Science and Innovations, CLEO_SI 2014, 8 June 2014 through 13 June 2014, San Jose, CA.
Open this publication in new window or tab >>Enhanced second-harmonic generation in GaP nanopillars arrays by modal engineering
2014 (English)In: Optics InfoBase Conference Papers, 2014Conference paper, Published paper (Refereed)
Abstract [en]

Second harmonic generation from GaP nanopillars with optimized mode field overlap is analyzed and experimentally demonstrated. We present dispersion engineering in arrays of nanopillars to satisfy modal phase matching.

Series
Optics InfoBase Conference Papers, ISSN 2162-2701
Keywords
Dispersions, Gallium alloys, Nonlinear optics, Dispersion engineering, Modal phase matching, Mode fields, Nanopillars, Nanopillars array, Second-harmonic, Nanostructures
National Category
Atom and Molecular Physics and Optics
Identifiers
urn:nbn:se:kth:diva-167543 (URN)2-s2.0-84906871479 (Scopus ID)9781557529992 (ISBN)
Conference
CLEO: Science and Innovations, CLEO_SI 2014, 8 June 2014 through 13 June 2014, San Jose, CA
Note

QC 20150609

Available from: 2015-06-09 Created: 2015-05-22 Last updated: 2016-12-05Bibliographically approved
Sanatinia, R. (2014). Ensemble and Individual III-V Semiconductor Nanopillars: Optical Properties and Applications. (Doctoral dissertation). Stockholm: KTH Royal Institute of Technology
Open this publication in new window or tab >>Ensemble and Individual III-V Semiconductor Nanopillars: Optical Properties and Applications
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Optical properties of semiconductor nanowires (NWs)/nanopillars (NPs), as individual or ensemble, have attracted significant research interest in recent years. Their potential applications range from solid-state lighting, photovoltaics, lasing and nonlinear optics to sensing and life sciences. Many of III-V NWs/NPs are particularly interesting for optoelectronic and photovoltaic applications, because of their direct band gap, high refractive index and superior electrical properties. These properties are beneficial for use in next generation solar cells by reducing the active cell thickness, while maintaining high efficiency. Furthermore, high second order nonlinearity coefficients of many III-V materials, for example GaAs and GaP, enhanced electric fields and tight confinement of optical modes make nanowaveguide geometries ideal for nonlinear effects.

The focus of this thesis is on the fabrication of III-V NPs, their optical properties and applications. Different methods for fabrication of NPs (top-down approach) are proposed. The fabricated NPs show a broadband suppression of reflectance, which is particularly an interesting feature for photovoltaic applications. The effect of the shape and geometry of GaAs NPs on their reflectance spectra is investigated and the experimental data show a very good agreement with the simulations. In order to decrease surface recombination in the fabricated GaAs NPs, a sulfur-based chemical passivation method was used, resulting in the recovery of photoluminescence (PL) linewidth and enhancing the PL intensity for more than an order of magnitude. Moreover, a unique wafer-scale self-organization process for generation of InP NPs is demonstrated. As a proof of concept, the self-organized InP NPs were used to fabricate solar cell devices. For fabrication of InP NP solar cells, epitaxial overgrowth of NPs arrays was used to realize p-n junctions. A significant increase in the open circuit voltage (0.13 V) of the NP solar cell was obtained after surface passivation.

Second-harmonic generation (SHG) was experimentally observed from GaP NP waveguides (single and in arrays) with vertical geometry. The generated second- harmonic light was analyzed with respect to the size of the NP waveguides and the corresponding effects of surface and bulk nonlinearities. In case of individual NPs, SHG was analyzed considering different modal excitations in GaP NPs. It was demonstrated that by varying the NP diameter and changing the pump polarization, it is possible to alter the field distribution of the radiated SHG light. The importance of tight confinement of the pump in the NP waveguides and consequently the longitudinal component of the electric field in this geometry is shown. A method was proposed to distinguish between surface and bulk contributions in SHG, which also addressed how to employ surface SHG to enhance the generated light. The proposed method was used to estimate the nonlinear coefficient and the effective thickness of the nonlinear region at the surface of GaP NP waveguides. Based on these findings, the corresponding nonlinear coefficient at the surface is estimated to be approximately 15 times higher, compared to the bulk. These findings, suggest that NPs/NWs (in this case GaP NPs) are potential alternatives for future nonlinear nanophotonic devices. Additionally, the SHG light from single GaP NPs are promising candidates for ultrafast light sources at nanoscopic scale, with potential applications in sensing, bio and single cell/ molecular imaging.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2014. p. xiii, 68
Series
TRITA-ICT/MAP AVH, ISSN 1653-7610 ; 2014:14
Keywords
nanopillar, nanowires, nanophotonics, nanofabrication, III-V semiconductors, photovoltaics, second-harmonic generation, top-down approach, colloidal lithography, antireflection, modal dispersion, polarization, nanowaveguide, indium phosphide, gallium arsenide, gallium phosphide
National Category
Nano Technology
Research subject
Physics
Identifiers
urn:nbn:se:kth:diva-155205 (URN)978-91-7595-333-5 (ISBN)
Public defence
2014-11-26, Sal/hall 205, Electrum, KTH-ICT, Kista, 10:00 (English)
Opponent
Supervisors
Note

QC 20141104

Available from: 2014-11-04 Created: 2014-11-03 Last updated: 2014-11-04Bibliographically approved
Sanatinia, R., Anand, S. & Swillo, M. (2014). Modal Engineering of Second-Harmonic Generation in Single GaP Nanopillars. Nano letters (Print), 14(9), 5376-5381
Open this publication in new window or tab >>Modal Engineering of Second-Harmonic Generation in Single GaP Nanopillars
2014 (English)In: Nano letters (Print), ISSN 1530-6984, E-ISSN 1530-6992, Vol. 14, no 9, p. 5376-5381Article in journal (Refereed) Published
Abstract [en]

We report on modal dispersion engineering for second-harmonic generation (SHG) from single vertical GaP nanopillars/nanowaveguides, fabricated by a top-down approach, using optical modal overlap between the pump (830 nm) and SHG (415 nm). We present a modal analysis for the SHG process in GaP nanopillars and demonstrate efficient utilization of the longitudinal component of the nonlinear polarization density. Our SHG measurements show quantitatively the presented model. We experimentally demonstrate that polarization beam shaping and field distribution modification of the radiated SHG light, at nanometer scale, can be achieved by tuning the pillar diameter and linear pump polarization. SHG from single pillars can be used as femtosecond nanoscopic light sources at visible wavelengths applicable for single cell/molecular imaging and interesting for future integrated nanophotonics components. While this work focuses on GaP nanopillars, the results are applicable to other semiconductor nanowire materials and synthesis methods.

Keywords
Nanopillar, second-harmonic generation, modal dispersion, polarization, nanowaveguide, gallium phosphide
National Category
Nano Technology Atom and Molecular Physics and Optics
Identifiers
urn:nbn:se:kth:diva-150121 (URN)10.1021/nl502521y (DOI)000341544500070 ()25157424 (PubMedID)2-s2.0-84914168992 (Scopus ID)
Note

QC 20140919

Available from: 2014-08-30 Created: 2014-08-30 Last updated: 2017-12-05Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-2069-2820

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