Imperial College London

Emeritus ProfessorRaymondMurray

Faculty of Natural SciencesDepartment of Physics

Visiting Professor
 
 
 
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Contact

 

+44 (0)20 7594 7578r.murray

 
 
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Location

 

913Blackett LaboratorySouth Kensington Campus

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Summary

 

Publications

Publication Type
Year
to

170 results found

Konishi T, Clarke E, Burrows CW, Bomphrey JJ, Murray R, Bell GRet al., 2017, Spatial regularity of InAs-GaAs quantum dots: quantifying the dependence of lateral ordering on growth rate, SCIENTIFIC REPORTS, Vol: 7, ISSN: 2045-2322

Journal article

Brossard FSF, Reid BPL, Nuttall L, Lenon S, Murray R, Taylor RAet al., 2016, Barrier engineering of a photonic molecule in a photonic crystal waveguide, Conference on Lasers and Electro-Optics (CLEO), Publisher: IEEE, ISSN: 2160-9020

Conference paper

Pieczarka M, Marynski A, Podemski P, Misiewicz J, Spencer PD, Murray R, Sek Get al., 2016, Energy Transfer Processes in InAs/GaAs Quantum Dot Bilayer Structure, 44th Jaszowiec International School and Conference on the Physics of Semiconductors (IS and CPS), Publisher: Polish Academy of Sciences, Pages: A59-A61, ISSN: 0587-4246

We investigate double layer InAs/GaAs quantum dots grown in the Stransky-Krastanov mode by molecular beam epitaxy. The sample consists of two layers of InAs quantum dots separated by 10 nm thick GaAs layer, where the top quantum dot layer of an improved homogeneity is covered by an InGaAs cap. This configuration has allowed for the extension of the dots' emission to longer wavelengths. We probed the carrier transfer between the states confined in a double quantum well composed of InGaAs cap and the quantum dots wetting layer to the states in the quantum dots by means of photoluminescence excitation and photoreflectance spectroscopies. Efficient emission from quantum dots excited at the double quantum well ground state energy was observed. There is also presented a discussion on the carrier injection efficiency from the capping layer to the quantum dots.

Conference paper

Taylor MW, Spencer P, Murray R, 2015, Negative circular polarization as a universal property of quantum dots, APPLIED PHYSICS LETTERS, Vol: 106, ISSN: 0003-6951

Journal article

Murray R, Brossard F, Spencer P, 2014, The influence of an optical well in controlling the mode splitting in a photonic molecule, Transparent Optical Networks (ICTON), ISSN: 2162-7339

Conference paper

Shahid H, Childs DTD, Majid MA, Kennedy K, Airey R, Hogg RA, Clarke E, Spencer P, Murray Ret al., 2014, Gain spectrum measurement using the segmented contact method with an integrated optical amplifier, Journal of Applied Physics, Vol: 115, Pages: 163105-163105, ISSN: 1089-7550

The measurement of optical gain utilising a segmented contact and integrated optical amplifier isreported. We show that in a direct comparison of methods, the use of the integrated amplifierallows the gain spectrum to be deduced over wider spectral ranges and to lower carrier densities, ascompared to the conventional segmented contact technique.

Journal article

Spencer P, Clarke E, Murray R, 2014, Carrier Escape and the Ideality Factor in Quantum Dot p-n Junctions, IEEE JOURNAL OF QUANTUM ELECTRONICS, Vol: 50, Pages: 213-219, ISSN: 0018-9197

Journal article

Daskalakis KS, Maier SA, Murray R, Kena-Cohen Set al., 2014, Nonlinear interactions in an organic polariton condensate, NATURE MATERIALS, Vol: 13, Pages: 272-279, ISSN: 1476-1122

Journal article

Daskalakis KS, Maier SA, Murray R, Kéna-Cohen Set al., 2014, Nonlinear interactions in an organic polariton condensate

We demonstrate an organic polariton condensate that exhibits nonlinear interactions at room-temperature. Upon reaching threshold, we observe a superlinear power dependence, a power-dependent blueshift and the emergence of long-range spatial coherence resulting from polariton interactions. © 2014 OSA.

Conference paper

Daskalakis KS, Maier SA, Murray R, Kena-Cohen Set al., 2014, Nonlinear interactions in an organic polariton condensate, Conference on Lasers and Electro-Optics (CLEO), Publisher: IEEE, ISSN: 2160-9020

Conference paper

Taylor MW, Spencer P, Clarke E, Harbord E, Murray Ret al., 2013, Tuning exciton g-factors in InAs/GaAs quantum dots, JOURNAL OF PHYSICS D-APPLIED PHYSICS, Vol: 46, ISSN: 0022-3727

Journal article

Majid MA, Childs DTD, Kennedy K, Airey R, Hogg RA, Clarke E, Spencer P, Murray Ret al., 2013, Absorption and single-pass gain measurements in bilayer quantum dot laser structure

In this paper we report on the absorption and single-pass gain analysis of molecular beam epitaxy (MBE) grown bilayer quantum dot (QD) laser material using multi-section method. The measurement allowed us to exclude unguided spontaneous emission and measure the internal optical loss accurately. © 2013 IEEE.

Conference paper

Brossard FSF, Reid BPL, Chan CCS, Xu XL, Griffiths JP, Williams DA, Murray R, Taylor RAet al., 2013, Confocal microphotoluminescence mapping of coupled and detuned states in photonic molecules, OPTICS EXPRESS, Vol: 21, Pages: 16934-16945, ISSN: 1094-4087

Journal article

Taylor MW, Spencer P, Clarke E, Harbord E, Murray Ret al., 2013, Resolving Zeeman splitting in quantum dot ensembles, APPLIED PHYSICS LETTERS, Vol: 102, ISSN: 0003-6951

Journal article

Daskalakis KS, Eldridge PS, Christmann G, Trichas E, Murray R, Iliopoulos E, Monroy E, Pelekanos NT, Baumberg JJ, Savvidis PGet al., 2013, All-dielectric GaN microcavity: Strong coupling and lasing at room temperature, APPLIED PHYSICS LETTERS, Vol: 102, ISSN: 0003-6951

Journal article

Harbord E, Iwamoto S, Arakawa Y, Spencer P, Clarke E, Murray Ret al., 2012, Influence of p-doping on the temperature dependence of In As/GaAs quantum dot excited state radiative lifetime, APPLIED PHYSICS LETTERS, Vol: 101, ISSN: 0003-6951

Journal article

Brossard FSF, Reid BPL, Chan CCS, Williams DA, Murray R, Taylor RAet al., 2012, MODE MAPPING OF COUPLED CAVITIES IN PHOTONIC CRYSTAL WAVEGUIDES, International Conference on Optical MEMS and Nanophotonics (OMN), Publisher: IEEE, Pages: 5-+

Conference paper

Majid MA, Childs DTD, Shahid H, Chen S, Kennedy K, Airey RJ, Hogg RA, Clarke E, Howe P, Spencer PD, Murray Ret al., 2011, Toward 1550-nm GaAs-Based Lasers Using InAs/GaAs Quantum Dot Bilayers, IEEE JOURNAL OF SELECTED TOPICS IN QUANTUM ELECTRONICS, Vol: 17, Pages: 1334-1342, ISSN: 1077-260X

Journal article

Majid MA, Childs DTD, Kennedy K, Airey R, Hogg RA, Clarke E, Spencer P, Murray Ret al., 2011, O-band excited state quantum dot bilayer lasers, APPLIED PHYSICS LETTERS, Vol: 99, ISSN: 0003-6951

Journal article

Majid MA, Childs DTD, Airey R, Kennedy K, Hogg RA, Clarke E, Spencer P, Murray Ret al., 2011, Strain engineered bilayers for extending the operating wavelength of quantum dot lasers, Conference on Semiconductor and Integrated Optoelectronics (SIOE 2010), Publisher: Institution of Engineering and Technology (IET), Pages: 100-104, ISSN: 1751-8768

The analysis of molecular-beam epitaxy (MBE) grown bilayer quantum dot (QD) laser material is reported here.Specifically, gain characteristics of 5× ‘bilayer’ QDs with GaAs caps and 5× ‘single’ QD layers with InGaAs caps werestudied experimentally. A transition of lasing from the ground state to lasing via the first excited state, and subsequently thesecond excited state is observed with increasing threshold gain for both the laser structures. A 50% increase in saturatedmodal gain is observed for bilayer laser as compared to single-layer samples. Further analysis of the bilayer sample using themulti-section technique allows the gain and absorption spectrum to be obtained.

Conference paper

Spencer P, Clarke E, Murray R, Groom KM, Alexander RR, Hogg RAet al., 2011, Subthreshold diode characteristics of InAs/GaAs quantum dot lasers, PHYSICAL REVIEW B, Vol: 83, ISSN: 1098-0121

Journal article

Usman M, Heck S, Clarke E, Spencer P, Ryu H, Murray R, Klimeck Get al., 2011, Experimental and theoretical study of polarization-dependent optical transitions in InAs quantum dots at telecommunication-wavelengths (1300-1500 nm), Journal of Applied Physics, Vol: 109, ISSN: 1089-7550

The design of some optical devices, such as semiconductor optical amplifiers for telecommunicationapplications, requires polarization-insensitive optical emission at long wavelengths (1300–1550 nm).Self-assembled InAs/GaAs quantum dots (QDs) typically exhibit ground state optical emissions atwavelengths shorter than 1300 nm with highly polarization-sensitive characteristics, although this canbe modified by the use of low growth rates, the incorporation of strain-reducing capping layers, or thegrowth of closely-stacked QD layers. Exploiting the strain interactions between closely stacked QDlayers also affords greater freedom in the choice of growth conditions for the upper layers, so that botha significant extension in their emission wavelength and an improved polarization response can beachieved due to modification of the QD size, strain, and composition. In this paper, we investigate thepolarization behavior of single and stacked QD layers using room temperature sub-lasing-thresholdelectroluminescence and photovoltage measurements, as well as atomistic modeling with the NEMO3-D simulator. A reduction is observed in the ratio of the transverse electric (TE) to transversemagnetic (TM) optical mode response for a GaAs-capped QD stack as compared to a single QD layer,but when the second layer of the two-layer stack is InGaAs-capped, an increase in the TE/TM ratio isobserved, in contrast to recent reports for single QD layers.

Journal article

Majid MA, Childs DTD, Shahid H, Chen SC, Kennedy K, Airey RJ, Hogg RA, Clarke E, Spencer P, Murray Ret al., 2011, Excited State Bilayer Quantum Dot Lasers at 1.3 mu m, International Conference on Solid State Devices and Materials (SSDM 2010), Publisher: JAPAN SOC APPLIED PHYSICS, ISSN: 0021-4922

Conference paper

Majid MA, Childs DTD, Shahid H, Airey R, Kennedy K, Hogg RA, Clarke E, Spencer P, Murray Ret al., 2011, 1.52 mu m electroluminescence from GaAs-based quantum dot bilayers, ELECTRONICS LETTERS, Vol: 47, Pages: 44-45, ISSN: 0013-5194

Journal article

Majid MA, Chen SC, Childs DTD, Shahid H, Airey RJ, Kennedy K, Hogg RA, Clarke E, Spencer P, Murray Ret al., 2011, Gain and absorption characteristics of bilayer quantum dot lasers beyond 1.3 mu m, Conference on Novel In-Plane Semiconductor Lasers X, Publisher: SPIE-INT SOC OPTICAL ENGINEERING, ISSN: 0277-786X

Conference paper

Majid MA, Childs DTD, Kennedy K, Airey R, Hogg RA, Clarke E, Spencer P, Murray Ret al., 2010, Towards 1.55 μm GaAs based lasers using quantum dot bilayers, Pages: 69-70, ISSN: 0899-9406

This paper reports on the use of quantum dot (QD) bilayers to extend the operating wavelength of GaAs based devices to 1.55 μm. We utilise a number of electrical and spectroscopic techniques to show how QD bilayers allow the realization of high quality laser devices beyond 1.3 μm. The introduction of InGaAs capping to the bilayers allows the further extension of the ground-state peak to 1.45 μm. Under high current densities carrier-carrier interaction broadens this peak, giving positive net modal gain in the 1.55 μm region. ©2010 IEEE.

Conference paper

Majid MA, Childs DTD, Chen S, Groom KM, Kennedy K, Airey R, Hogg RA, Clarke E, Spencer P, Murray Ret al., 2010, Gain spectra analysis of bilayer quantum dot lasers beyond 1.3μm

In this paper we report on the analysis of molecular beam epitaxy (MBE) grown GaAs and InGaAs capping bilayer QD laser material via a number of characterization techniques. The InGaAs capped bilayer QD lasers extends the room temperature lasing wavelength to 1.45μm. The further analysis of the materials using the multisection technique allows the gain and absorption spectrum to be obtained under various CW and pulsed bias conditions and at a range of currents and temperatures. The spectral measurement of gain demonstrates that net modal gain is achieved beyond 1.5μm at room temperature. Analysis of the temperature and current density dependence of gain allows insight into the increase in threshold current around room temperature for a GaAs capped bilayer laser.

Conference paper

Slavcheva G, Roussignol P, 2010, Optical Generation and Control of Quantum Coherence in Semiconductor Nanostructures, Heidelberg, Publisher: Not Avail, ISBN: 9783642124907

The book focuses on recent advances in the optical control of coherence in excitonic and polaritonic systems as model systems for the complex semiconductor ...

Book

Clarke E, Howe P, Taylor M, Spencer P, Harbord E, Murray R, Kadkhodazadeh S, McComb DW, Stevens BJ, Hogg RAet al., 2010, Persistent template effect in InAs/GaAs quantum dot bilayers, JOURNAL OF APPLIED PHYSICS, Vol: 107, ISSN: 0021-8979

Journal article

Majid MA, Childs DTD, Airey R, Kennedy K, Hogg RA, Clarke E, Spencer P, Murray Ret al., 2010, Bilayer for extending the wavelength of QD lasers, Conference on Quantum Dots 2010 (QD2010), Publisher: IOP PUBLISHING LTD, ISSN: 1742-6588

Conference paper

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