Optical gain and stimulated emission in silicon nanocrystals

2002 ◽  
Vol 738 ◽  
Author(s):  
L. Dal Negro ◽  
M. Cazzanelli ◽  
Z. Gaburro ◽  
P. Bettotti ◽  
L. Pavesi ◽  
...  
Keyword(s):  
Silicon Nanocrystals ◽  
Chemical Vapour ◽  
Optical Gain ◽  
Pump Intensity ◽  
Stimulated Emission ◽  
Thin Layers ◽  
Threshold Behaviour ◽  
Time Resolved ◽  
Emission Signal ◽  
Length Measurements

ABSTRACTTime-resolved luminescence measurements on silicon nanocrystal waveguides have revealed a fast recombination dynamics, related to population inversion which leads to net optical gain. The waveguide samples were obtained by thermal annealing of plasma enhanced chemical vapour deposited thin layers of silicon rich oxide Variable stripe length measurements performed on the fast emission signal have shown an exponential growth of the amplified spontaneous emission, with net gain values of about 10 cm-1. Both the fast component intensity and its temporal width revealed threshold behaviour as a function of the incident pump intensity. A modelling of the decay dynamics is suggested within an effective four level rate equation treatment including the delicate interplay among stimulated emission and Auger recombinations.

Pump-Probe Measurements Using Silicon Nanocrystal Waveguides

2003 ◽  
Vol 770 ◽  
Author(s):  
Nathanael Smith ◽  
Max J. Lederer ◽  
Marek Samoc ◽  
Barry Luther-Davies ◽  
Robert G. Elliman
Keyword(s):  
Probe Beam ◽  
Time Resolution ◽  
Pump Beam ◽  
Silicon Nanocrystals ◽  
Continuous Wave ◽  
Optical Gain ◽  
Optical Pump ◽  
Time Resolved ◽  
Pump Probe ◽  
Probe Measurements

AbstractOptical pump-probe measurements were performed on planar slab waveguides containing silicon nanocrystals in an attempt to measure optical gain from photo-excited silicon nanocrystals. Two experiments were performed, one with a continuous-wave probe beam and a pulsed pump beam, giving a time resolution of approximately 25 ns, and the other with a pulsed pump and probe beam, giving a time resolution of approximately 10 ps. In both cases the intensity of the probe beam was found to be attenuated by the pump beam, with the attenuation increasing monotonically with increasing pump power. Time-resolved measurements using the first experimental arrangement showed that the probe signal recovered its initial intensity on a time scale of 45-70 μs, a value comparable to the exciton lifetime in Si nanocrystals. These data are shown to be consistent with an induced absorption process such as confined carrier absorption. No evidence for optical gain was observed.

Time-resolved measurements of optical gain and photoluminescence in silicon nanocrystals

2010 ◽  
Vol T141 ◽  
pp. 014011 ◽  
Author(s):  
K Dohnalová ◽  
K Kůsová ◽  
O Cibulka ◽  
L Ondič ◽  
I Pelant
Keyword(s):  
Silicon Nanocrystals ◽  
Optical Gain ◽  
Time Resolved ◽  
Time Resolved Measurements

Grains of Porous Silicon Embedded in SiO2:Studies of Optical Gain and Electroluminescence

2004 ◽  
Vol 99-100 ◽  
pp. 31-36 ◽  
Author(s):  
K. Dohnalová ◽  
K. Luterová ◽  
J. Valenta ◽  
Jiří Buršík ◽  
M. Procházka ◽  
...  
Keyword(s):  
Porous Silicon ◽  
Silicon Nanocrystals ◽  
Visible Region ◽  
Optical Gain ◽  
Intrinsic Property ◽  
Stimulated Emission ◽  
Silicon Nanostructures ◽  
Porous Si ◽  
Si Nanocrystals ◽  
Excitation Spot

Recent reports on experimental observation of optical gain in silicon nanostructures in the visible region, performed at several laboratories all over the world, have triggered an extraordinary surge of interest in silicon lasing. However, attempts aimed at reproducing the red stimulated emission from „standard“silicon nanocrystals (sized 3-5 nm) at some other laboratories either failed, or. did not come to definite conclusions. Therefore, more detailed measurements of optical gain in a wider variety of samples containing Si nanocrystals are required in order to unravel whether or not the observation of optical gain is an intrinsic property of Si nanocrystals. We have performed a detailed study of optical gain in layers of densely packed Si nanocrystals in SiO2, prepared on the basis of porous Si, using the variable-stripe-length (VSL) method in combination with the shifted-excitation-spot (SES) method. In selected samples we have observed a distinct difference in behaviour between VSL and SES curves, indicating the occurrence of positive optical gain of ~ 24 cm-1. Preliminary reports on transport and electroluminescence measurements in thin films of SiO2 doped with porous silicon grains, prepared by spin-coating technique, are also discussed.

Stimulated Emission at 258 nm in AlN/AlGaN Quantum Wells Grown on Bulk AlN Substrates

2003 ◽  
Vol 764 ◽  
Author(s):  
R. Gaska ◽  
Q. Fareed ◽  
G. Tamulaitis ◽  
I. Yilmaz ◽  
M.S. Shur ◽  
...  
Keyword(s):  
Quantum Wells ◽  
Emission Intensity ◽  
Chemical Vapour ◽  
Pump Intensity ◽  
Stimulated Emission ◽  
Structural Quality ◽  
Multiple Quantum ◽  
Sample Edge ◽  
Intensity Saturation ◽  
Stripe Length

AbstractWe report on observation of stimulated emission at 258 nm in AlN/AlGaN multiple quantum wells. The structures were grown over Al-face single crystal bulk AlN substrates. AlN/AlGaN structures with 50% of Al in the well material were grown using low-pressure metalorganic chemical vapour deposition. Characterization by using X-ray, AFM, SEM, and photoluminescence techniques indicated high structural quality of the structures. The stimulated emission was measured using the variable stripe length method under excitation by 4-ns-long pulses of the fifth harmonic of Nd:YAG laser radiation at 213 nm (5.82 eV). The stimulated emission exhibited a characteristic superlinear dependence of emission intensity on the pump intensity as well as an exponential increase of the sample-edge emission intensity with increasing stripe length up to ∼430 μm and the intensity saturation beyond this range. The observation of stimulated emission at 258 nm is very promising for the future development of III-nitride-based deep-UV laser diodes on bulk AlN substrates.

Time-Resolved Gain Dynamics in Silicon Nanocrystals

2003 ◽  
Vol 770 ◽  
Author(s):  
L. Dal Negro ◽  
M. Cazzanelli ◽  
N. Daldosso ◽  
L. Pavesi ◽  
F. Priolo ◽  
...  
Keyword(s):  
Silicon Nanocrystals ◽  
Optical Pumping ◽  
Chemical Vapor ◽  
Stimulated Emission ◽  
Threshold Behavior ◽  
Pumping Power ◽  
Time Duration ◽  
Modal Gain ◽  
Time Resolved ◽  
Level Model

AbstractTime-resolved variable stripe length (VSL) experiments on a set of silicon nanocrystal waveguides obtained by plasma enhanced chemical vapor deposition (PECVD) have revealed a fast recombination dynamics (20 ns) related to population inversion under 6 ns optical pumping at 355 nm. Modal gain values about 10 cm-1 have been measured at 760 nm by VSL technique for the fast recombination component while optical losses about 15 cm-1 are measured for the integrated signal in the slow (lifetime of about 10 μs) recombination tail. Threshold behavior in the emission intensity together with a pumping length and pumping power dependence of both the intensity and the time duration of the fast recombination component has been observed. These results are explained within an effective four level model to describe the strong competition among different Auger processes and stimulated emission.

scholarly journals Silicon Nanocrystals: Fundamental Theory and Implications for Stimulated Emission

2008 ◽  
Vol 2008 ◽  
pp. 1-32 ◽  
Author(s):  
V. A. Belyakov ◽  
V. A. Burdov ◽  
R. Lockwood ◽  
A. Meldrum
Keyword(s):  
Energy Transfer ◽  
Silicon Nanocrystals ◽  
Light Emission ◽  
Theoretical Calculations ◽  
Energy Levels ◽  
Optical Gain ◽  
Stimulated Emission ◽  
Recombination Rates ◽  
Physical Mechanisms ◽  
Gain Profile

Silicon nanocrystals (NCs) represent one of the most promising material systems for light emission applications in microphotonics. In recent years, several groups have reported on the observation of optical gain or stimulated emission in silicon NCs or in porous silicon (PSi). These results suggest that silicon-NC-based waveguide amplifiers or silicon lasers are achievable. However, in order to obtain clear and reproducible evidence of stimulated emission, it is necessary to understand the physical mechanisms at work in the light emission process. In this paper, we report on the detailed theoretical aspects of the energy levels and recombination rates in doped and undoped Si NCs, and we discuss the effects of energy transfer mechanisms. The theoretical calculations are extended toward computational simulations of ensembles of interacting nanocrystals. We will show that inhomogeneous broadening and energy transfer remain significant problems that must be overcome in order to improve the gain profile and to minimize nonradiative effects. Finally, we suggest means by which these objectives may be achieved.

Spontaneous and Stimulated Recombination in the Nitrides

1996 ◽  
Vol 449 ◽  
Author(s):  
A. Hangleiter ◽  
F. Scholz ◽  
V. Härle ◽  
J. S. Im ◽  
G. Frankowsky
Keyword(s):  
Quantum Wells ◽  
Room Temperature ◽  
Optical Gain ◽  
Stimulated Emission ◽  
Time Resolved ◽  
Double Heterostructures ◽  
Bulk Gan ◽  
Photoluminescence Studies ◽  
Excitonic Effects ◽  
Time Resolved Photoluminescence

ABSTRACTBoth spontaneous and stimulated emission processes are essential ingredients for constructing a laser from the nitrides. Based on our picosecond time-resolved photoluminescence studies we show that spontaneous radiative recombination is strongly influenced by excitonic effects, both in bulk GaN and in quantum wells. Particularly in quantum wells, localization of excitons plays an important role. We have studied the optical gain spectra in GaInN/GaN and GaN/AlGaN double heterostructures and quantum wells, grown by LP-MOVPE, using the stripe excitation method. Both room temperature and low temperature measurements were performed. Based on our results, we discuss the physical mechanism of optical gain in the nitrides as well as consequences for laser operation. We show that localization or, equivalently, the formation of quantum dot like structures, governs the optical gain mechanism in the nitrides.

Stimulated emission in plasma-enhanced chemical vapour deposited silicon nanocrystals

2003 ◽  
Vol 16 (3-4) ◽  
pp. 297-308 ◽  
Author(s):  
L. Dal Negro ◽  
M. Cazzanelli ◽  
N. Daldosso ◽  
Z. Gaburro ◽  
L. Pavesi ◽  
...  
Keyword(s):  
Silicon Nanocrystals ◽  
Chemical Vapour ◽  
Stimulated Emission

Reduction of carbon impurities in aluminium nitride from time-resolved chemical vapour deposition using trimethylaluminum

2020 ◽  
Author(s):  
Polla Rouf ◽  
Pitsiri Sukkaew ◽  
Lars Ojamäe ◽  
Henrik Pedersen
Keyword(s):  
Chemical Vapour Deposition ◽  
Vapour Deposition ◽  
Chemical Vapour ◽  
Aluminium Nitride ◽  
Methyl Groups ◽  
Time Resolved ◽  
Thermally Induced ◽  
Light Emitting ◽  
Carbon Impurities ◽  
Wide Range

<p>Aluminium nitride (AlN) is a semiconductor with a wide range of applications from light emitting diodes to high frequency transistors. Electronic grade AlN is routinely deposited at 1000 °C by chemical vapour deposition (CVD) using trimethylaluminium (TMA) and NH<sub>3</sub> while low temperature CVD routes to high quality AlN are scarce and suffer from high levels of carbon impurities in the film. We report on an ALD-like CVD approach with time-resolved precursor supply where thermally induced desorption of methyl groups from the AlN surface is enhanced by the addition of an extra pulse, H<sub>2</sub>, N<sub>2</sub> or Ar between the TMA and NH<sub>3</sub> pulses. The enhanced desorption allowed deposition of AlN films with carbon content of 1 at. % at 480 °C. Kinetic- and quantum chemical modelling suggest that the extra pulse between TMA and NH<sub>3</sub> prevents re-adsorption of desorbing methyl groups terminating the AlN surface after the TMA pulse. </p>

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