Population inversion in electrically and optically pumped graphene

2007 ◽  
Vol 40 (2) ◽  
pp. 317-320 ◽  
Author(s):  
Maxim Ryzhii ◽  
Victor Ryzhii
Keyword(s):  
Population Inversion ◽  
Optically Pumped

Stress-controlled phonon-impurity resonances in terahertz silicon lasers

2009 ◽  
Vol 1221 ◽  
Author(s):  
Sergey G. Pavlov
Keyword(s):  
Ground State ◽  
Population Inversion ◽  
Silicon Crystal ◽  
Shallow Donor ◽  
Uniaxial Deformation ◽  
Optically Pumped ◽  
Energy Gaps ◽  
Donor States ◽  
And Shifts ◽  
Silicon Lasers

AbstractOptically pumped terahertz silicon lasers utilize transitions between shallow donor states at low lattice temperatures. Population inversion in these lasers is built-up due to selective relaxation routes of optically excited electrons into impurity ground state. Each relaxation step of the electron occurs under assistance of intervalley and intravalley phonons with energies approaching the particular energy gaps between interacting excited donor states. These impurity phonon interactions determine, at the end, the lifetimes of the laser levels, and, therefore, efficiency of intracenter silicon lasers. Deformation of silicon crystal is a classical example of controllable influence on energy spectrum of shallow donor levels due to specific splitting and shifts of conduction band valleys. Using moderate (up to 400 MPa) external uniaxial deformation of a crystal, one can radically modify the impurity spectra while the phononic spectra remain almost unchanged. We have demonstrated significant improvement of efficiency for intracenter silicon lasers followed by changes of lifetime for the upper and the lower laser levels due to moving the impurity levels either into or out of resonance with corresponding intervalley phonon frequencies.

Graphene Terahertz Lasers: Injection versus Optical Pumping

2013 ◽  
Vol 1505 ◽  
Author(s):  
Taiichi Otsuji ◽  
Akira Satou ◽  
Maxim Ryzhii ◽  
Vladimir Mitin ◽  
Victor Ryzhii
Keyword(s):  
Spectral Range ◽  
Population Inversion ◽  
Optical Pumping ◽  
Optically Pumped ◽  
Dynamic Conductivity ◽  
Graphene Layers ◽  
Nonequilibrium States ◽  
Injection Type ◽  
Terahertz Lasers ◽  
Graphene Structures

ABSTRACTIn this paper we demonstrate that graphene is one of the best materials for new types of terahertz lasers as optical and/or injection pumping of graphene can exhibit negative-dynamic conductivity in the terahertz spectral range. We analyze the formation of nonequilibrium states in optically pumped graphene layers and in forward-biased graphene structures with lateral p-i-n junctions and consider the conditions of population inversion and lasing. The latter provides a significant advantage of the injection pumping in realization of graphene terahertz lasers. We benchmark graphene as a prospective material for injection-type terahertz lasers.

INFLUENCE OF ELECTRON TEMPERATURE ON POPULATION INVERSION AMONG ELECTRONIC SUBBANDS IN OPTICALLY PUMPED SEMICONDUCTOR QUANTUM WELLS

1996 ◽  
Vol 10 (27) ◽  
pp. 1323-1331 ◽  
Author(s):  
W. XU ◽  
C. ZHANG
Keyword(s):  
Quantum Wells ◽  
Electron Temperature ◽  
Population Inversion ◽  
Laser System ◽  
Far Infrared ◽  
Double Quantum ◽  
Hot Electron ◽  
Optically Pumped ◽  
Scattering Rate ◽  
Double Quantum Well

A detailed theoretical study on population inversion among different electronic subbands, induced by hot-electron interactions with LO-phonons and with photons, is presented for an optically pumped AlGaAs-GaAs double quantum well system which may behave as a 3-level far-infrared laser generator. The influence of electron temperature and pumping intensity on the population inversion in this laser system proposed very recently, has been studied through calculating the inter-subband electronic scattering rate caused by electron-LO-phonon interactions and by optical absorption scattering. Theoretical results obtained from this study indicate that at a fixed pumping intensity, the population inversion among different electronic subbands can be tuned by varying electron temperature through, e.g. applying an in-plane electric field.

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