Papers - Ota, Yasutomo

Measuring the second-order coherence of a nanolaser by intracavity frequency doubling

Ota Y., Watanabe K., Iwamoto S., Arakawa Y.

Physical Review A Atomic Molecular and Optical Physics 89 ( 2 )  2014.02

Research paper (scientific journal), Joint Work, Accepted,  ISSN  10502947

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We measured the second-order coherence at zero time delay, g(2)(0), of a high-Q photonic crystal nanocavity quantum dot laser below and above the lasing threshold, via detecting visible emission originated from the second harmonic generation (SHG) occurring within the laser cavity. The efficiency of the nonlinear frequency conversion process, defined by SHG intensity divided by the square of laser output intensity, is shown to be proportional to g(2)(0), and hence is used for the measurement. The obtained g(2)(0) values show good agreement with those measured by a Hanbury Brown-Twiss interferometer equipped with ultrafast superconducting single-photon detectors. © 2014 American Physical Society.

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Cavity quantum electrodynamics in quantum dot-photonic crystal nanocavity coupled system with large G/k

Iwamoto S., Ota Y., Takagi H., Takamiya D., Arakawa Y.

Conference on Lasers and Electro Optics Europe Technical Digest 2014-January 2014

Research paper (international conference proceedings), Joint Work, Accepted

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We report experimental progresses in cavity quantum electrodynamics using H1 and H0-type photonic crystal nanoacvities embedding single quantum dots. Strong coupling and enhanced optical Stark effect in these systems with large g/kwill be discussed.

Measurement of the second order coherence of a nanolaser through its intra-cavity second harmonic generation

Ota Y., Watanabe K., Iwamoto S., Arakawa Y.

Optics Infobase Conference Papers  2014

Research paper (international conference proceedings), Joint Work, Accepted

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We measured the second order coherence of a photonic crystal nanolaser through measuring frequency doubling occurring within the laser nanocavity. This method enables investigation of the intensity noise properties even far below the lasing threshold. © 2014 OSA.

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Measurement of the second order coherence of a nanolaser through its intra-cavity second harmonic generation

Ota Y., Watanabe K., Iwamoto S., Arakawa Y.

Conference on Lasers and Electro Optics Europe Technical Digest 2014-January 2014

Research paper (international conference proceedings), Joint Work, Accepted

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We measured the second order coherence of a photonic crystal nanolaser through measuring frequency doubling occurring within the laser nanocavity. This method enables investigation of the intensity noise properties even far below the lasing threshold.

Cavity quantum electrodynamics in quantum dot-photonic crystal nanocavity coupled system with large g/KΚ

Iwamoto S., Ota Y., Takagi H., Takamiya D., Arakawa Y.

Optics Infobase Conference Papers  2014

Research paper (international conference proceedings), Joint Work, Accepted

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We report experimental progresses in cavity quantum electrodynamics using H1 and H0-type photonic crystal nanoacvities embedding single quantum dots. Strong coupling and enhanced optical Stark effect in these systems with large g/KΚ will be discussed. © 2014 OSA.

Self-frequency summing in quantum dot photonic crystal nanocavity lasers

Ota Y., Watanabe K., Iwamoto S., Arakawa Y.

Applied Physics Letters 103 ( 24 )  2013.12

Research paper (scientific journal), Joint Work, Accepted,  ISSN  00036951

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We demonstrate self-frequency summing in photonic crystal nanocavity lasers with quantum dot gain. Two dipole modes and a hexapole mode, supported in the cavity, simultaneously showed lasing oscillation in the near infrared wavelength region under optical carrier injection. Meanwhile, within the same laser cavity, the internally generated three laser fields are up-converted to exhibit sharp visible emission lines via intra-cavity nonlinear frequency summing (and doubling) processes. This self-frequency summing process in active nanocavities will pave the way for developing nanoscale nonlinear optical light sources. © 2013 AIP Publishing LLC.

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Giant optical rotation in a three-dimensional semiconductor chiral photonic crystal

Takahashi S., Tandaechanurat A., Igusa R., Ota Y., Tatebayashi J., Iwamoto S., Arakawa Y.

Optics Express 21 ( 24 ) 29905 - 29913 2013.12

Research paper (scientific journal), Joint Work, Accepted

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Optical rotation is experimentally demonstrated in a semiconductor-based three-dimensional chiral photonic crystal (PhC) at a telecommunication wavelength. We design a rotationally-stacked woodpile PhC structure, where neighboring layers are rotated by 45° and four layers construct a single helical unit. The mirror-asymmetric PhC made from GaAs with sub-micron periodicity is fabricated by a micro-manipulation technique. The linearly polarized light incident on the structure undergoes optical rotation during transmission. The obtained results show good agreement with numerical simulations. The measurement demonstrates the largest optical rotation angle as large as ~ 23° at 1.3 μm wavelength for a single helical unit. © 2013 Optical Society of America.

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Enhancement of valence band mixing in individual InAs/GaAs quantum dots by rapid thermal annealing

Harbord E., Ota Y., Igarashi Y., Shirane M., Kumagai N., Ohkouchi S., Iwamoto S., Yorozu S., Arakawa Y.

Japanese Journal of Applied Physics 52 ( 12 )  2013.12

Research paper (scientific journal), Joint Work, Accepted,  ISSN  00214922

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We measure polarization resolved photoluminescence from excitonic complexes in tens of single InAs/GaAs quantum dots (QDs) over a wide range of energies in two samples: one as-grown, the other subjected to rapid thermal annealing (RTA). Using the linear polarization of the X⁺ emission as a probe of the valence band mixing (VBM), we find that RTA enhances QD VBM, attributed to the increase in QD height. We complement our measurements with 8-band k · p calculations, which suggest the increase in height on annealing is responsible for this enhancement. © 2013 The Japan Society of Applied Physics.

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Multi-color visible light generation by self-frequency doubling in photonic crystal nanocavity quantum dot lasers

Ota Y., Watanabe K., Iwamoto S., Arakawa Y.

CLEO Science and Innovations CLEO Si 2013  2013.11

Research paper (international conference proceedings), Joint Work, Accepted

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We report multi-color visible light generation from photonic crystal nanocavity lasers exhibiting broadband quantum dot gain in the near infrared. The visible emission is produced though self-frequency doubling, which efficiently occurs within the high Q nanocavities. © OSA 2013.

Growth of high-quality InAs quantum dots embedded in GaAs nanowire structures on Si substrates

Kwoen J., Watanabe K., Ota Y., Iwamoto S., Arakawa Y.

Physica Status Solidi C Current Topics in Solid State Physics 10 ( 11 ) 1496 - 1499 2013.11

Research paper (scientific journal), Joint Work, Accepted,  ISSN  18626351

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We present the growth of InAs quantum dots (QD) embedded in GaAs nanowires (NW) on silicon and demonstrate clear single photon emission. Sharp excitonic emission (linewidth of 162 μeV) and the generation of single photons (g⁽²⁾(0) = 0.18) was observed by low temperature photoluminescence measurements, suggesting a high optical quality which can be attributed to the high crystal quality of the QD structure. It is believed that the crystal quality is high due to the Stranski-Krastanov (S-K) mode of the growth. This structure may open new ways for the integration of such photon emitters into future 'on-silicon' quantum optical circuits. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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Large vacuum Rabi splitting in an H0 photonic crystal nanocavity-quantum dot system

Takamiya D., Ota Y., Ohta R., Takagi H., Kumagai N., Ishida S., Iwamoto S., Arakawa Y.

Pacific Rim Conference on Lasers and Electro Optics CLEO Technical Digest  2013.10

Research paper (international conference proceedings), Joint Work, Accepted

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We demonstrate a large vacuum Rabi splitting in an H0 photonic crystal nanocavity-quantum dot system. The nanocavity with an ultra-small mode volume enabled us to observe the largest splitting ever reported using single InAsquantum dots. © 2013 IEEE.

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Nonlinear photonics in single quantum dot-photonic crystal nanocavity couples systems

Iwamoto S., Ota Y., Takagi H., Kumagai N., Arakawa Y.

Pacific Rim Conference on Lasers and Electro Optics CLEO Technical Digest  2013.10

Research paper (international conference proceedings), Joint Work, Accepted

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We will present our recent advances on single quantum dot-photonic crystal nanocavity coupled systems. Cavity enhanced two-photon emission and large optical Stark effect with extremely low control power in these systems will be mainly discussed. © 2013 IEEE.

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Self-frequency summing in photonic crystal nanocavity quantum dot lasers

Ota Y., Watanabe K., Iwamoto S., Arakawa Y.

Pacific Rim Conference on Lasers and Electro Optics CLEO Technical Digest  2013.10

Research paper (international conference proceedings), Joint Work, Accepted

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Self-frequency summing processes in photonic crystal nanocavity quantum dot lasers are observed. High quality factors and small mode volumes of the nanocavities facilitate efficient nonlinear frequency summing processes, generating a variety of visible emission lines. © 2013 IEEE.

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Nanocavity-based self-frequency conversion laser

Ota Y., Watanabe K., Iwamoto S., Arakawa Y.

Optics Express 21 ( 17 ) 19778 - 19789 2013.08

Research paper (scientific journal), Joint Work, Accepted

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Self-frequency conversion (SFC), where both laser oscillation and nonlinear frequency conversion occurs in the same laser crystal, has been used to efficiently extend the operational wavelength of lasers. Downsizing of the cavity mode volume (V) and increasing the quality factor (Q) could lead to a more efficient conversion process, mediated by enhanced n-th order nonlinearities that generally scale as (Q/V)ⁿ. Here, we demonstrate nanocavity-based SFC by utilizing photonic crystal nanocavity quantum dot lasers. The high Q and small V supported in semiconductorbased nanocavities facilitate efficient SFC to generate visible light, even with only a few photons present in the laser cavity. The combined broadband quantum dot gain and small device footprint enables the monolithic integration of 26 different-color nanolasers (spanning 493-627 nm) within a micro-scale region. These nanolasers provide a new platform for studying few-photon nonlinear optics, and for realizing full-color lasers on a single semiconductor chip. ©2013 Optical Society of America.

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Formation and optical properties of multi-stack InGaAs quantum dots embedded in GaAs nanowires by selective metalorganic chemical vapor deposition

Tatebayashi J., Ota Y., Ishida S., Nishioka M., Iwamoto S., Arakawa Y.

Journal of Crystal Growth 370   299 - 302 2013.05

Research paper (scientific journal), Joint Work, Accepted,  ISSN  00220248

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We report formation and optical properties of site-controlled, multi-stack InGaAs/GaAs quantum dots (QDs) embedded in GaAs nanowires (NWs) by selective metalorganic chemical vapor deposition. InGaAs/GaAs QDs are realized in GaAs NWs grown on patterned GaAs(111)B substrates in the form of InGaAs/GaAs heterostructures and identi.ed by structural analyses and photoluminescence characterization. Optical characterization at 10 K corroborates formation of high-quality, multi-stack InGaAs/GaAs QD-in-NWs up to 50-stack without degradation of PL intensities. In addition, light emission at room temperature from multi-stack InGaAs/GaAs QDs embedded in GaAs NWs is realized. These results would enable the realization of high-performance IBSCs based on site-controlled QD-in-NWs utilizing existing, well-established NW growth technologies on a GaAs platform. © 2012 Elsevier B.V. All rights reserved.

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Electro-mechanical Q factor control of photonic crystal nanobeam cavity

Ohta R., Ota Y., Takagi H., Kumagai N., Tanabe K., Ishida S., Iwamoto S., Arakawa Y.

Japanese Journal of Applied Physics 52 ( 4 PART 2 )  2013.04

Research paper (scientific journal), Joint Work, Accepted,  ISSN  00214922

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We design and demonstrate a photonic crystal nanobeam cavity with a Q factor controllable by a micro-electro-mechanical system (MEMS). The cavity is evanescently coupled to an adjacent nanobeam waveguide, and its Q factor is controlled by electro-mechanically adjusting the gap distance between them. We experimentally demonstrate control of the Q factor from 2,250 to 2,750, by applying voltage from 0 to 11 V. © 2013 The Japan Society of Applied Physics.

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Multi-color visible light generation by self-frequency doubling in photonic crystal nanocavity quantum dot lasers

Ota Y., Watanabe K., Iwamoto S., Arakawa Y.

2013 Conference on Lasers and Electro Optics CLEO 2013  2013

Research paper (international conference proceedings), Joint Work, Accepted

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We report multi-color visible light generation from photonic crystal nanocavity lasers exhibiting broadband quantum dot gain in the near infrared. The visible emission is produced though self-frequency doubling, which efficiently occurs within the high Q nanocavities. © 2013 The Optical Society.

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Formation of a single in(Ga)As/GaAs quantum dot embedded in a site-controlled GaAs nanowire by metalorganic chemical vapor deposition for application to single photon sources

Tatebayashi J., Ota Y., Karunathillake D., Ishida S., Nishioka M., Iwamoto S., Arakawa Y.

Materials Research Society Symposium Proceedings 1439   115 - 119 2012.12

Research paper (international conference proceedings), Joint Work, Accepted,  ISSN  02729172

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We report the formation and optical properties of site-controlled InAs/GaAs quantum dots (QDs) embedded in GaAs nanowires (NWs) by selective metalorganic chemical vapor deposition for application to single photon sources. InAs/GaAs QD-in-NWs with various InAs thicknesses are realized on patterned GaAs(111)B substrates in the form of InAs/GaAs heterostructures and identified by structural analyses using scanning transmission electron microscopy and photoluminescence characterization. Sharp excitonic emission peaks at 10 K from single QD-in-NWs with the narrowest exciton linewidth of 87 μe V are observed. Light emission from the single QD-in-NW shows photon antibunching which evidences single photon emission from high-quality QD-in-NWs. © 2012 Materials Research Society.

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High Q H1 photonic crystal nanocavities with efficient vertical emission

Takagi H., Ota Y., Kumagai N., Ishida S., Iwamoto S., Arakawa Y.

Optics Express 20 ( 27 ) 28292 - 28300 2012.12

Research paper (scientific journal), Joint Work, Accepted

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We report on newly-designed H1-type photonic crystal (PhC) nanocavities that simultaneously exhibit high Q factors, small mode volumes, and high external coupling efficiencies (η) of light radiated above the PhC membrane. Dipole modes of the H1 PhC nanocavities, which are doubly-degenerate and orthogonally-polarized in theory, are investigated both by numerical calculations and experiments. Through modifying the sizes and positions of the air-holes near to the defect cavity, a Q factor of 62,000 is achieved, accompanied with an improved η of 0.38 (assuming an objective lens with a numerical aperture of 0.65). A further increase of η to more than 0.60 is observed at the expense of slight degradation of Q factor (down to 50,000). We further experimentally confirm the increase of both Q and η, using micro-photoluminescence measurements, and demonstrate high Q factors up to 25,000: the highest value ever reported for dipole modes in H1 PhC nanocavities. © 2012 Optical Society of America.

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Intra-cavity frequency doubling in photonic crystal nanocavity quantum dot lasers

Ota Y., Watanabe K., Iwamoto S., Arakawa Y.

2012 IEEE Photonics Conference IPC 2012    610 - 611 2012.12

Research paper (international conference proceedings), Joint Work, Accepted

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We report visible light generation via intra-cavity frequency doubling in photonic crystal nanocavity quantum dot lasers. A strong field enhancement in the nanocavity enables the efficient conversion process, even with only a few intra-cavity photons. © 2012 IEEE.

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