Novel Field Emission Organic Light Emitting Diodes

Yokoyama, M.; Li, Chi-Shing; Su, Shui‐Hsiang

doi:10.1587/transele.e94.c.307

Cited by 5 publications

(8 citation statements)

References 14 publications

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“…This rescales the experimental data to 0 Ͻ g,e ͑t͒ Ͻ 1 and results in a significant difference in g,e ͑0͒ for different voltages. = w0 exp͑−V / V 0 ͒, where w0 = 18 ps and V 0 Ϸ −2 V. Very similar results with w0 Ϸ 20 ps were reported for the recovery of QW based structures 9 and successfully used in the modeling. 10 The exponential dependence on applied voltage results from a thermally activated rate process, as introduced in Ref.…”

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confidence: 80%

Intradot dynamics of InAs quantum dot based electroabsorbers

Piwoński

Pulka

Madden

et al. 2009

Applied Physics Letters

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The carrier relaxation and escape dynamics of InAs/GaAs quantum dot waveguide absorbers is studied using heterodyne pump-probe measurements. Under reverse bias conditions, we reveal differences in intradot relaxation dynamics, related to the initial population of the dots' ground or excited states. These differences can be attributed to phonon-assisted or Auger processes being dominant for initially populated ground or excited states, respectively. © 2009 American Institute of Physics. ͓DOI: 10.1063/1.3106633͔The physics of quantum dot ͑QD͒ based optical devices has been studied intensively due to their interesting blend of atomic and solid state properties.1 Recently, attention has been focused on their absorption properties and has led to QD materials finding favor in such applications as monolithic mode-locked lasers, 2 electroabsorption modulators, 3 and saturable absorber mirrors. 4 Time-resolved pump-probe spectroscopy is a very useful technique to investigate the fundamental timescales and underlying dynamical processes occurring in such absorbers; a notable example being the demonstration of the dynamical role of different carrier types for QW devices. 5 More recently, similar techniques were applied to QD structures to explain the nature of tunneling processes at high reverse bias voltages 6 and to demonstrate the electroabsorption properties of a bilayer QD waveguide. 7In this letter, the nonlinear recovery of QD based reversed-biased waveguide absorbers is analyzed using a single color pump-probe technique. Either the dots' ground state ͑GS͒ or excited state ͑ES͒ is initially populated thus increasing the transmission, and the resulting absorption recovery dynamics is recorded. The recovery dynamics is observed to be dependent on the initial population of the dots' energy states. The difference in recovery dynamics can be understood by the ES to GS carrier relaxation process being phonon assisted when the dots are initially populated in the GS, while it is Auger related when the dots' ES is initially populated.In our experiments, we study intradot relaxation processes as a function of reverse bias using time-resolved spectroscopy. The QD waveguide absorber was 1 mm long, had 4 m width ridges together with tilted, antireflection coated facets. It was fabricated from a material that included six stacks of InAs/GaAs QDs in a dots-in-a-well structure, grown by Zia Inc. ͑see Ref. 8 for further details of the material and experimental technique͒. To summarize, the GS and ES peaks appear at 1320 and 1250 nm, respectively. The pump-probe differential transmission was measured using a heterodyne detection technique. Pulses of about 600 fs width at either 1320 or 1250 nm were obtained from a titaniumsapphire pumped, optical parametric oscillator and split into three beams: reference, pump, and probe ͑260 fJ pump pulse energy, 13 fJ probe pulse energy͒. After propagation through the waveguide absorber with suitable delays, the frequency shifted probe and reference beams were overlapped on a detector, and the amp...

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confidence: 80%

Intradot dynamics of InAs quantum dot based electroabsorbers

Piwoński

Pulka

Madden

et al. 2009

Applied Physics Letters

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“…The output power was obtained from the external mirror. 8) The reflectivity of the external mirror was kept low at 20% in a wavelength of 405 nm to obtain a high-power output. The effective external-cavity length was 150 mm, which was designed for a 1 GHz repetition rate of the optical pulse.…”

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confidence: 99%

Passive and Hybrid Mode-Locking of an External-Cavity GaInN Laser Diode Incorporating a Strong Saturable Absorber

Oki

Saito

Watanabe³

et al. 2010

Appl. Phys. Express

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“…As pointed out in Ref. 7, w = w ͑V͒ can be described as w = w0 exp͑−͉V / V 0 ͉͒, where w0 = 18 ps and V 0 Ϸ −2 V. The same dependence with w0 Ϸ 20 ps was used to describe the recovery of quantum well based structures 10 and used in the modeling. 11 The exponential dependence on the applied voltage has been linked to a thermally activated rate process as introduced in Ref.…”

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confidence: 99%

Recovery time scales in a reversed-biased quantum dot absorber

Viktorov

Erneux

Mandel

et al. 2009

Applied Physics Letters

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The nonlinear recovery of quantum dot based reverse-biased waveguide absorbers is investigated both experimentally and analytically. We show that the recovery dynamics consists of a fast initial layer followed by a relatively slow decay. The fast recovery stage is completely determined by the intradot properties, while the slow stage depends on the escape from the dot to the wetting layer. The physical properties of quantum dot ͑QD͒ based optical devices has been studied intensively in recent years 1 with particular attention given on their absorption properties. This has led to their use as monolithic mode-locked lasers, 2 electroabsorption modulators 3 and saturable absorber mirrors. 4 To explore the underlying carrier dynamics, timeresolved pump-probe spectroscopy has been applied to such QD structures in order to explain the nature of tunneling processes at high reverse bias voltages, 5 to demonstrate the electroabsorption properties of a bilayer QD waveguide, 6 and to illustrate the importance of Auger processes when the dots excited state ͑ES͒ is initially populated.7 In this letter, we investigate the nonlinear recovery of QD based reversebiased waveguide absorbers experimentally, analytically, and numerically. Our study highlights the role of the capture and escape processes in the formation of a fast initial layer followed by a relatively slow relaxation. We show that the fast stage is completely determined by the intradot relaxation properties while the slow recovery stage depends on the escape from the dot to the wetting layer.Our experiment uses time-resolved pump probe spectroscopy to study the nonlinear recovery of QD based reversed-biased waveguide absorbers as a function of reverse bias. The QD waveguide absorber was 1 mm long had a 4 m width ridges together with tilted antireflection coated facets. It was fabricated from material that included six stacks of InAs/GaAs QDs in a dots-in-a-well structure, grown by Zia, Inc. ͑see Ref. 8 for further details of the material and experimental technique͒. Ground state ͑GS͒ and ES appear at 1320 and 1250 nm, respectively. The pumpprobe differential transmission was measured at the dots' GS using a heterodyne detection technique. In reverse bias, the saturation fluence varied from ϳ0.1 J / m 2 at 0 V to 0.6 J / m 2 at 9 V. Pulses of about 600 fs width at either 1320 or 1250 nm were obtained from a titanium-sapphire pumped, optical parametric oscillator and split into three beams: reference, pump, and probe. After propagation through the waveguide absorber with suitable delays, the probe and reference beams were overlapped on a detector. The amplitude of the difference frequency was detected using a high frequency lock-in amplifier. This signal is proportional to the differential transmission ⌬T of a probe pulse at the same wavelength as the pump. The resulting data are normalized to the maximum differential transmission at zero reverse bias T 0 and therefore represented by ⌬T / T 0 .Figure 1 displays such differential transmission dynamics for reverse bias ...

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Novel Field Emission Organic Light Emitting Diodes

Cited by 5 publications

References 14 publications

Intradot dynamics of InAs quantum dot based electroabsorbers

Intradot dynamics of InAs quantum dot based electroabsorbers

Passive and Hybrid Mode-Locking of an External-Cavity GaInN Laser Diode Incorporating a Strong Saturable Absorber

Recovery time scales in a reversed-biased quantum dot absorber

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