Search results for "Lasing threshold"
showing 10 items of 41 documents
Current status of AlInN layers lattice-matched to GaN for photonics and electronics
2007
We report on the current properties of Al1-x InxN (x approximate to 0.18) layers lattice- matched ( LM) to GaN and their specific use to realize nearly strain- free structures for photonic and electronic applications. Following a literature survey of the general properties of AlInN layers, structural and optical properties of thin state- of- the- art AlInN layers LM to GaN are described showing that despite improved structural properties these layers are still characterized by a typical background donor concentration of ( 1 - 5) x 10(18) cm(-3) and a large Stokes shift (similar to 800 meV) between luminescence and absorption edge. The use of these AlInN layers LM to GaN is then exemplified …
Blue lasing at room temperature in high quality factor GaN/AlInN microdisks with InGaN quantum wells
2007
The authors report on the achievement of optically pumped III-V nitride blue microdisk lasers operating at room temperature. Controlled wet chemical etching of an AlInN interlayer lattice matched to GaN allows forming inverted cone pedestals. Whispering gallery modes are observed in the photoluminescence spectra of InGaN/GaN quantum wells embedded in the GaN microdisks. Typical quality factors of several thousands are found (Q>4000). Laser action at similar to 420 nm is achieved under pulsed excitation at room temperature for a peak power density of 400 kW/cm(2). The lasing emission linewidth is down to 0.033 nm.
Multi-line NIR-RGB emission in Nd:LiNbO3 RPE optical waveguides
2007
Simultaneous generation of four spectral emission lines has been achieved in Nd-doped lithium niobate reverse proton exchange optical waveguide cavities. Using a pump at 800 nm, the four lines were found and they are due to lasing at 1.3735 combined with parametric conversion at 0.687, 0.574 and 0.4 mum.
Multi-longitudinal mode emission in a bidirectional laser model
2011
Multi-longitudinal mode emission is a fundamental issue in laser physics. Interestingly enough, the mechanisms responsible for the transition from single- to multi-longitudinal mode emission have not been completely clarified yet. For example, it is well known that in unidirectional ring lasers the Rabi splitting of the lasing transition can lead to multimode emission even in a homogeneously broadened medium, the so called Risken-Nummedal—Graham-Haken instability (RNGHI) [1]. In spite of being known since the late sixties, only in the recent years a couple of experiments have demonstrated “dressed” versions of the RNGHI [2], i.e., up to day there are not clear demonstrations of this basic m…
Evidence for degenerate mirrorless lasing in alkali metal vapor: forward beam magneto-optical experiment
2018
We report an experimental observation of degenerate mirrorless lasing in forward direction under excitation of a dilute atomic Rb vapor with a single linearly polarized cw laser light resonant with cycling Fe > Fg atomic D2 transitions. Light polarized orthogonally to the laser light is generated for the input light intensity exceeding a threshold value of about 3 mW/cm^2. Application of a transverse magnetic field directed along the input light polarization reveals a sharp about 20 mG wide magnetic resonance centered at B = 0. Increasing the incident light intensity from 3 to 300 mW/cm^2, the generated light undergoes rapid amplitude increase followed by a decline and resonance broadeni…
Laser action in electrically driven quantum dot matrix
2007
A lasing system based on electrically driven quantum dot matrix is proposed, where population inversion of the dot matrix is obtained by rapid (nonadiabatic) switching on of in-plane electric field as a pumping force. Numerical analysis of electron-photon system kinetics is performed for various electric fields and temperatures. For parabolic type of confinement in QDs, a convenient amplification of contribution from several levels is indicated. The relevant analysis utilises an exact solution of Cauchy problem for an infinite chain of linear differential equations.
Lasing condition for trapped modes in subwavelength--wired PT--symmetric resonators
2021
The ability to control the laser modes within a subwavelength resonator is of key relevance in modern optoelectronics. This work deals with the theoretical research on optical properties of a PT-symmetric nano-scaled dimer formed by two dielectric wires, one is with loss and the other with gain, wrapped with graphene sheets. We show the existence of two non-radiating trapped modes which transform into radiating modes by increasing the gain–loss parameter. Moreover, these modes reach the lasing condition for suitable values of this parameter, a fact that makes these modes achieve an ultra high quality factor that is manifested on the response of the structure when it is excited by a plane wa…
Transverse effects in ring fiber laser multimode instabilities
2000
We study the influence of the transverse structure of pump and lasing fields and of the width of the doped region on the conditions for the appearance of the multimode instability in an ${\mathrm{Er}}^{3+}$-doped ring fiber laser. We show that the instability can be inhibited while maintaining a large output power when the radius of the doped region is a fraction of the core radius.
Optomechanical systems close to the conservative limit
2017
In dissipative optomechanical systems, the total damping hits negative values at the parametric instability point. This also corresponds to the phonon lasing threshold, where the mechanical resonator enters in the self-induced oscillations regime. This paper shows that the two mentioned phenomena are delayed from each other when the optomechanical systems operate close to their conservative limit, where the mechanical damping is very small. In fact, the total damping can be negative and very small for a while before the phonon lasing happens. As a result, the linearized theory is extended over the negative damping region where the mechanical displacements remain very small. It follows that …
Excitation power dependence of the Purcell effect in photonic crystal microcavity lasers with quantum wires
2013
The Purcell effect dependence on the excitation power is studied in photonic crystal microcavity lasers embedding InAs/InP quantum wires. In the case of non-lasing modes, the Purcell effect has low dependence on the optical pumping, attributable to an exciton dynamics combining free and localized excitons. In the case of lasing modes, the influence of the stimulated emission makes ambiguous the determination of the Purcell factor. We have found that this ambiguity can be avoided by measuring the dependence of the decay time on the excitation power. These results provide insights in the determination of the Purcell factor in microcavity lasers. © 2013 AIP Publishing LLC.