Effect of proton bombardment on InAs dots and wetting layer in laser structures

O'Driscoll, I.; Blood, P.; Smowton, Peter M.; Sobiesierski, Angela; Gwilliam, R.

doi:10.1063/1.4730964

Cited by 8 publications

(7 citation statements)

References 7 publications

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“…23. The absorption peak was not shifted by bombardment, and transmission electron microscopy showed the integrity of the dots was retained.…”

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confidence: 86%

“…Time-resolved luminescence showed a factor ten faster decay at the transition energy, and analysis in Ref. 23 shows that defects are also introduced into the wetting layer, so at low temperatures, carriers can also be lost by tunnelling to nearby defect states. 24 Mode-locking was observed in these devices with pulse widths reducing by a factor 29 from 8.4 ps at 250 K to 290 fs at 20 K, and this correlates with the temperature dependence of threshold of the same structures, as shown in Fig.…”

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confidence: 99%

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Femtosecond pulse generation in passively mode locked InAs quantum dot lasers

Finch¹,

Blood²,

Smowton³

et al. 2013

Applied Physics Letters

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Optical pulse durations of an InAs two-section passively mode-locked quantum dot laser with a proton bombarded absorber section reduce from 8.4 ps at 250K to 290 fs at 20 K, a factor of 29, with a corresponding increase in optical bandwidth. Rate equation analysis of gain and emission spectra using rate equations suggests this is due to the very low emission rate of carriers to the wetting layer in the low temperature, random population regime which enables dots across the whole inhomogeneous distribution to act as independent oscillators. (C) 2013 AIP Publishing LLC

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“…23. The absorption peak was not shifted by bombardment, and transmission electron microscopy showed the integrity of the dots was retained.…”

mentioning

confidence: 86%

mentioning

confidence: 99%

Femtosecond pulse generation in passively mode locked InAs quantum dot lasers

Finch¹,

Blood²,

Smowton³

et al. 2013

Applied Physics Letters

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“…In the saturable absorber, the main mechanism by which carriers are lost from the dot at low temperatures is emission to the wetting layer [10] and this becomes very slow below about 225 K [11]. We have therefore bombarded the absorber sections with protons, with energy of 250 keV and dose of 1 × 10 12 cm −2 , to introduce nonradiative recombination centers and increase the recombination rate to reduce the recovery time.…”

Section: Device Structures and Experimental Detailsmentioning

confidence: 99%

Improving the Optical Bandwidth of Passively Mode-Locked InAs Quantum Dot Lasers

Finch

Hutchings

Blood

et al. 2015

IEEE J. Select. Topics Quantum Electron.

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We examine in detail the relation between the optical gain spectra, mode-locked optical emission spectra, and temporal optical pulse widths as a function of temperature between 80 and 300 K in passively mode-locked InAs quantum dot lasers. By increasing the length of the active region, we can decrease the threshold gain requirement for mode locking. At 300 K, where the dot states and wetting layer are close to thermal equilibrium, the bandwidth of the optical emission spectra and temporal optical pulse width remain largely unaffected when the threshold gain requirement is reduced. At 80 K, where the dots are randomly populated, there is a near doubling of the optical bandwidth for the same reduction of the threshold gain requirement and a corresponding decrease in the temporal optical pulse width. Rate equations, which take explicit account of the photon density in the cavity, are used to qualitatively highlight the key parameters, which are responsible for increasing the optical bandwidth in the random population regime.

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“…A few research groups have reported encouraging results of QD lasers showing enhanced resistance to radiation damage [1][2][3], but complete understanding of physical mechanisms leading to this enhancement is still lacking. Also, it is well known that point defects induced by proton irradiation behave as nonradiative recombination centers (NRCs), but the role that NRCs play in reliability and degradation mechanisms in QD lasers is not well understood.…”

Section: Introductionmentioning

confidence: 96%