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Nonlinear Properties of III-V Semiconductor Nanowaveguides
KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
2019 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Nonlinear optics (NLO) plays a major role in the modern world: nonlinear optical phenomena have been observed in a wavelength range going from the deep infrared to the extreme ultraviolet, to THz radiation. The optical nonlinearities can be found in crystals, amorphous materials, polymers, liquid crystals, liquids, organic materials, and even gases and plasmas. Nowadays, NLO is relevant for applications in quantum optics, quantum computing, ultra-cold atom physics, plasma physics, and particle accelerators. The work presented in the thesis is limited only to the semiconductors that have a second-order optical nonlinearity and includes two phenomena that use second-order nonlinearity: second-harmonic generation (SHG) and spontaneous parametric down-conversion (SPDC). Among the many options available, the investigation presented concerns gallium phosphide (GaP) and gallium indium phosphide (Ga0.51In0.49P), two semiconductors of the group III-V with the ¯43m crystal symmetry.

However, some of the results found can be generalized for other materials with ¯43m crystal symmetry.

In the thesis, the fabrication of GaP nanowaveguides with dimensions from 0.03 μm and an aspect ratio above 20 using focused ion beam (FIB) milling is discussed. The problem of the formation of gallium droplets on the surface is solved by using a pulsed laser to oxidize the excess surface gallium locally on the FIB-milled nanowaveguides. SHG is used to evaluate the optical quality of the fabricated GaP nanowaveguides. Additionally, a theoretical and experimental way to enhance SHG in nanowaveguides is introduced. This process uses the overlap of interacting fields defined by the fundamental mode of the pump and the second-order mode of the SHG, which is enhanced by the longitudinal component of the nonlinear polarization density. Through this method, it was possible to obtain a maximum efficiency of 10−4, which corresponds to 50 W−1cm−2. The method can be generalized for any material with a ¯43m crystal symmetry. Furthermore, SHG is used to characterize the nonlinear properties of a nanostructure exposed for a long time to a CW laser at 405 nm to reduce the photoluminescence (PL) of Ga0.51In0.49P. The PL was reduced by -34 dB without causing any damage to the nanostructures or modifying the nonlinear properties. The fabrication process for obtaining the nanowaveguide is interesting as well, since the fabricated waveguide in Ga0.51In0.49P, whose sizes are 200 nm thick, 11 μm wide and 1.5 mm long, was transferred on silicon dioxide (SiO2). This type of nanowaveguide is interesting for SPDC, since it satisfies the long interaction length necessary for an efficient SPDC. Finally, a configuration consisting of illuminating the top surface of a nanowaveguide with a pump beam to generate signal and idler by SPDC is presented. These fabricated nanostructures open a way to the generation of counter-propagating idler and signal with orthogonal polarization. By using a different cut of the crystal, i.e. [110], it makes possible to obtain degenerate wavelength generation, and in certain conditions to obtain polarization-entangled photons or squeezed states.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2019. , p. 97
Series
TRITA-SCI-FOU ; 2019:45
National Category
Other Physics Topics
Research subject
Physics, Optics and Photonics
Identifiers
URN: urn:nbn:se:kth:diva-260068ISBN: 978-91-7873-318-7 (print)OAI: oai:DiVA.org:kth-260068DiVA, id: diva2:1354474
Public defence
2019-10-23, FA32, AlbaNova universitetscentrum, Roslagstullsbacken 21, Stockholm, 10:00 (English)
Opponent
Supervisors
Available from: 2019-09-27 Created: 2019-09-25 Last updated: 2019-10-08Bibliographically approved
List of papers
1. Focused ion beam milling of gallium phosphide nanostructures for photonic applications
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: 2019-09-25Bibliographically approved
2. Modal phase matching in nanostructured zinc-blende semiconductors for second-order nonlinear optical interactions
Open this publication in new window or tab >>Modal phase matching in nanostructured zinc-blende semiconductors for second-order nonlinear optical interactions
Show others...
2017 (English)In: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 96, no 7, article id 075303Article in journal (Refereed) Published
Abstract [en]

We demonstrate enhanced second-harmonic generation in arrays of nanowaveguides satisfying modal-phase-matching condition, both theoretically and experimentally. The overlap of interacting fields defined by the fundamental mode of the pump and the second-order mode of the second-harmonic wave is enhanced by the longitudinal component of the nonlinear polarization density. For guided modes with significant longitudinal electric field components, the overlap of fields is comparable to that obtained in the quasi-phase-matching technique leading to higher conversion efficiencies. Thus, the presented method is preferable to achieve higher conversion efficiency in second-order nonlinear processes in nanowaveguides.

Place, publisher, year, edition, pages
American Physical Society, 2017
National Category
Other Physics Topics
Identifiers
urn:nbn:se:kth:diva-212601 (URN)10.1103/PhysRevB.96.075303 (DOI)000407015600007 ()2-s2.0-85028996573 (Scopus ID)
Funder
Swedish Research Council, 349-2007-8664 621-2013-5811
Note

QC 20170824

Available from: 2017-08-24 Created: 2017-08-24 Last updated: 2019-09-25Bibliographically approved
3. Gallium Indium Phosphide Microstructures with Suppressed Photoluminescence for Applications in Nonlinear Optics
Open this publication in new window or tab >>Gallium Indium Phosphide Microstructures with Suppressed Photoluminescence for Applications in Nonlinear Optics
2019 (English)In: Optics Letters, ISSN 0146-9592, Vol. 44, no 21Article in journal (Refereed) Published
Abstract [en]

Gallium indium phosphide (Ga0.51In0.49P), lattice matched to gallium arsenide, shows remarkable second-order nonlinear properties, as well as strong photoluminescence due to its direct band gap. By measuring the second-harmonic generation from the GaInP microwaveguide (0.2 x 11 x 1300 μm) before and after stimulating intrinsic photobleaching, we demonstrate that the photoluminescence could be strongly suppressed (-34 dB), leaving the nonlinear properties unchanged, making it suitable for low-noise applications.

Place, publisher, year, edition, pages
Optical Society of America, 2019
National Category
Engineering and Technology
Research subject
Physics, Optics and Photonics
Identifiers
urn:nbn:se:kth:diva-260072 (URN)000493940500004 ()
Note

QC 20191001

Available from: 2019-09-25 Created: 2019-09-25 Last updated: 2019-12-03Bibliographically approved
4. Degenerated Spontaneous Parametric Down Conversion in Semiconductor Waveguide with -43m Crystal Symmetry
Open this publication in new window or tab >>Degenerated Spontaneous Parametric Down Conversion in Semiconductor Waveguide with -43m Crystal Symmetry
(English)Manuscript (preprint) (Other academic)
Abstract [en]

In this paper, a configuration consisting in a pump propagating in an orthogonal direction with respect to the surface of a nanowaveguide is studied. It is possible to show that the generation by spontaneous parametric down-conversion of a signal and an idler photons inside the nanowaveguide is strongly dependent on the waveguide thickness, because the high refractive index of the waveguide core creates also an optical cavity for the pump field. Furthermore, it was evaluated the best condition for photon-pair generation in case of a nanowaveguide in gallium indium phosphide, which has a −43m symmetry.For the same waveguide geometry, but orientation parallel to the [110] plane, it is possible to use spontaneous parametric down-conversion to generate counter-propagating photon-pair with the same polarization. When the efficiency of the generated photon-pairs in TM0 and TE0 modes is the same, then it is possible to obtain polarization entangled photons, by using this configuration. Furthermore, by adding a mirror at one of the end of the waveguide, the system can be used to produce a squeezed-state.

National Category
Engineering and Technology
Research subject
Physics, Optics and Photonics
Identifiers
urn:nbn:se:kth:diva-260074 (URN)
Note

QC 20191001

Available from: 2019-09-25 Created: 2019-09-25 Last updated: 2019-10-08Bibliographically approved

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