scholarly journals Solid cyclooctatetraene-based triplet quencher demonstrating excellent suppression of singlet–triplet annihilation in optical and electrical excitation

2020 ◽  
Vol 11 (1) ◽  
Author(s):  
Van T. N. Mai ◽  
Viqar Ahmad ◽  
Masashi Mamada ◽  
Toshiya Fukunaga ◽  
Atul Shukla ◽  
...  
Keyword(s):  
Continuous Wave ◽  
Fold Increase ◽  
Complete Suppression ◽  
Laser Dye ◽  
Electrical Excitation ◽  
Design And Synthesis ◽  
Cw Operation ◽  
Nanosecond Range ◽  
Organic Laser ◽  
Triplet Excitons

Abstract Triplet excitons have been identified as the major obstacle to the realisation of organic laser diodes, as accumulation of triplet excitons leads to significant losses under continuous wave (CW) operation and/or electrical excitation. Here, we report the design and synthesis of a solid-state organic triplet quencher, as well as in-depth studies of its dispersion into a solution processable bis-stilbene-based laser dye. By blending the laser dye with 20 wt% of the quencher, negligible effects on the ASE thresholds, but a complete suppression of singlet–triplet annihilation (STA) and a 20-fold increase in excited-state photostability of the laser dye under CW excitation, were achieved. We used small-area OLEDs (0.2 mm2) to demonstrate efficient STA suppression by the quencher in the nanosecond range, supported by simulations to provide insights into the observed STA quenching under electrical excitation. The results demonstrate excellent triplet quenching ability under both optical and electrical excitations in the nanosecond range, coupled with excellent solution processability.

scholarly journals Room Temperature CW Operation of GaN-based Blue Laser Diodes by GaInN/GaN optical guiding layers

2000 ◽  
Vol 5 (S1) ◽  
pp. 1-7 ◽  
Author(s):  
Masayoshi Koike ◽  
Shiro Yamasaki ◽  
Yuta Tezen ◽  
Seiji Nagai ◽  
Sho Iwayama ◽  
...  
Keyword(s):  
Room Temperature ◽  
Continuous Wave ◽  
Laser Diodes ◽  
Threshold Current ◽  
Crystal Defects ◽  
Blue Laser ◽  
Buffer Layers ◽  
Continuous Wave Laser ◽  
Cw Operation ◽  
First Time

GaN-based short wavelength laser diodes are the most promising key device for a digital versatile disk. We have been improving the important points of the laser diodes in terms of optical guiding layers, mirror facets. The continuous wave laser irradiation at room temperature could be achieved successfully by reducing the threshold current to 60 mA (4 kA/cm2). We have tried to apply the multi low temperature buffer layers to the laser diodes for the first time to reduce the crystal defects.

New efficient laser dye for pulsed and CW operation in the UV

1980 ◽  
Vol 33 (1) ◽  
pp. 85-88 ◽  
Author(s):  
W. Hüffer ◽  
R. Schieder ◽  
H. Telle ◽  
R. Raue ◽  
W. Brinkwerth
Keyword(s):  
Laser Dye ◽  
Cw Operation

ROLE OF DISLOCATIONS IN InGaN-BASED LEDs AND LASER DIODES

2000 ◽  
Vol 10 (01) ◽  
pp. 271-279 ◽  
Author(s):  
SHUJI NAKAMURA
Keyword(s):  
Quantum Well ◽  
Output Power ◽  
Continuous Wave ◽  
Laser Diodes ◽  
Transverse Mode ◽  
High Current ◽  
Single Quantum Well ◽  
Cw Operation ◽  
Current Operation ◽  
Composition Fluctuations

UV InGaN and GaN single-quantum-well structure light-emitting diodes (LEDs) were grown on epitaxially laterally overgrown (ELOG) and sapphire substrates. When the emission wavelength of UV InGaN LEDs was shorter than 380 nm, the external quantum efficiency (EQE) of the LED on ELOG was much higher than that on sapphire only at high-current operation. At low-current operation, both LEDs had the same EQE. When the active layer was GaN, EQE of the LED on sapphire was much lower than that on ELOG at both low- and high-current operation due to the lack of localized energy states formed by In composition fluctuations. In order to improve the lifetime of laser diodes (LDs), ELOG had to be used because the operating current density of the LDs is much higher than that of LEDs. A violet InGaN multi-quantum-well GaN/AlGaN separate-confinement-heterostructure LD was grown on ELOG on sapphire. The LDs with cleaved mirror facets shows an output power as high as 40 mW under room-temperature continuous-wave (CW) operation. The stable fundamental transverse mode was observed at an output power of up to 40 mW. The estimated lifetime of the LDs at a constant output power of 10 mW was more than 2,000 hours under CW operation at an ambient temperature of 60°C.

scholarly journals Output of [14C]adenine nucleotides and their derivatives from cerebral tissues. Tetrodotoxine-resistant and calcium ion-requiring components

1973 ◽  
Vol 136 (4) ◽  
pp. 893-901 ◽  
Author(s):  
Ian Pull ◽  
Henry McIlwain
Keyword(s):  
Electrical Stimulation ◽  
Calcium Ion ◽  
Adenine Nucleotides ◽  
Fold Increase ◽  
Adenosine Kinase ◽  
Electrical Excitation ◽  
Maximal Increase

1. Neocortical tissues, exposed briefly to [14C]adenine and containing over 98% of their14C as adenine nucleotides, when superfused with glucose–bicarbonate salines released about 0.1% of their14C content/min to the superfusate. 2. Addition of unlabelled adenosine to the superfusing fluid increased the14C output three- to four-fold; half-maximal increase was given by about 40μm-adenosine, and reasons are adduced for considering the activity of adenosine kinase to be a major factor in conditioning the14C output. Adenosine similarly increased the enhanced14C output caused by electrical excitation of the superfused tissue; it brought about only a small increase in tissue glycolysis. 3. Output of14C from the [14C]adenine-labelled tissues was increased when Ca2+was omitted from the superfusing fluids, but electrical stimulation did not then liberate more14C. Nevertheless, such tissues still responded to electrical stimulation by increased glycolysis, and their14C output again became susceptible to increase by electrical stimulation when Ca2+was restored. 4. The six-fold increase in tissue glycolysis caused by electrical excitation was almost completely inhibited by tetrodotoxin at 0.1μm and above, but this was associated with about 50% inhibition only in the output of14C from tissues preincubated with [14C]adenine. The14C-labelled compounds of which output was most inhibited by tetrodotoxin were adenosine, inosine and hypoxanthine whereas output in a nucleotide fraction was little affected.

scholarly journals Излучательные характеристики мощных полупроводниковых лазеров (1060 нм) с узким мезаполосковым контактом на основе асимметричных гетероструктур AlGaAs/GaAs с широким волноводом

2020 ◽  
Vol 54 (4) ◽  
pp. 408
Author(s):  
И.С. Шашкин ◽  
А.Ю. Лешко ◽  
Д.Н. Николаев ◽  
В.В. Шамахов ◽  
Н.А. Рудова ◽  
...  
Keyword(s):  
Peak Power ◽  
Continuous Wave ◽  
Optical Power ◽  
Maximum Efficiency ◽  
Thermal Heating ◽  
Cw Operation ◽  
Power Profile ◽  
Low Efficiency ◽  
Narrow Stripe ◽  
A Current

Light characteristics of narrow-stripe lasers (5.5 m) based on asymmetric AlGaAs/GaAs heterostructures are studied. It was shown that the maximum optical power achieved under continuous-wave (CW) operation is limited by thermal heating and reaches 1695 mW at a current of 2350 mA at +25°C, and the maximum efficiency reaches 54.8 %. By reducing the operating temperature to -8°C, we were able to increase the maximum power to 2 W. A peak power of 2930 mW was obtained under pulsed operation (pulse width 240 ns, amplitude 4230 mA). It is shown there is a region of an “optical dip” in the power profile with a low-efficiency lasing of a train of pulses of sub-ns duration under pulsed operation.

scholarly journals Adenosine as a constituent of the brain and of isolated cerebral tissues, and its relationship to the generation of adenosine 3′:5′-cyclic monophosphate

1977 ◽  
Vol 164 (1) ◽  
pp. 131-137 ◽  
Author(s):  
Michael Newman ◽  
Henry McIlwain
Keyword(s):  
Electrical Stimulation ◽  
Cyclic Amp ◽  
Guinea Pig ◽  
Room Temperature ◽  
Fold Increase ◽  
Electrical Excitation ◽  
Adenosine Concentration ◽  
The Brain ◽  
Guinea Pig Brain

1. Adenosine was determined in rapidly frozen rat and guinea-pig brain and in guinea-pig cerebral tissues after incubation in vitro. Adenosine concentrations were approx. 2nmol/g wet wt. in frozen tissue, diminished at room temperature, and returned to 2nmol/g on incubation in oxygenated glucose/salines. 2. Superfusion with noradrenaline then increased the tissue's adenosine concentration 2.5-fold, and hypoxia caused an 8-fold increase. 3. Electrical stimulation alone or in the presence of noradrenaline or histamine increased the tissue's adenosine and cyclic AMP, but adenosine concentrations reached their peak later and were maintained for longer than those of cyclic AMP. 4. Superfusion with l-glutamate with and without electrical excitation raised adenosine concentrations to 15–34nmol/g. The increases in cyclic AMP on electrical stimulation, superfusion with glutamate or a combination of these treatments were diminished by addition of adenosine deaminase or theophylline. 5. It is concluded that adenosine can be produced endogenously in cerebral systems, in sufficient concentrations to accelerate an adenosine-activated adenylate cyclase, and by this route can contribute to the cerebral actions of electrical stimulation and of the neurohumoral agents. In certain instances cyclic AMP as substrate contributes to an increase in adenosine.

scholarly journals Novel Schemes for Compact FELs in the THz Region

2019 ◽  
Vol 4 (4) ◽  
pp. 90
Author(s):  
Andrea Doria ◽  
Gian Piero Gallerano ◽  
Emilio Giovenale
Keyword(s):  
Pulse Duration ◽  
Free Electron ◽  
Continuous Wave ◽  
Industrial Applications ◽  
Wide Frequency Range ◽  
Free Electrons ◽  
Cw Operation ◽  
Power Peak ◽  
Compact Sources ◽  
Radiation Time

The rapid advance of terahertz technologies in terms of radiation generators, systems, and scientific or industrial applications has put a particular focus on compact sources with challenging performances in terms of generated power (peak and/or average), radiation time structure, and frequency band tunability. Free electron laser (FEL)-based sources are probably the best candidates to express such a versatility; there are a number of schemes that have been investigated over the years to generate coherent radiation from free electrons in the mm-wave and terahertz regions of the spectrum, covering a wide frequency range from approximately 100 GHz to 10 THz. This paper proposes novel schemes for exploring the limits in the performance of radio frequency-driven free-electron devices in terms of ultrashort pulse duration, wide bandwidth operation, and energy recovery for near continuous wave (CW) operation. The aim of the present work is to demonstrate the feasibility of an FEL achieving performance comparable to a conventional photoconductive THz source, which is commonly used for time-domain spectroscopy (TDS), in terms of bandwidth and pulse duration. We will also demonstrate that a THz FEL could be very powerful and flexible in terms of tailoring its spectral features.

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