Spontaneous emission

About: Spontaneous emission is a research topic. Over the lifetime, 12855 publications have been published within this topic receiving 323684 citations.

Optical spectroscopy and diode-pumped laser performance of Nd/sup 3+/ in the CNGG crystal

Abstract: We have exploited the broad absorption and emission bandwidth of the laser crystal Ca/sub 3/(NbGa)/sub 2-x/Ga/sub 3/O/sub 12/ doped with Nd/sup 3+/ to develop a tunable and mode locked diode-pumped 1.06 /spl mu/m laser. We also present the fluorescence and excitation spectra at different crystal temperatures from 10 to 298 K. The spontaneous transition probabilities, the branching ratios, and the radiative lifetime are calculated by means of the Judd-Ofelt theory and compared with the experimental results. The stimulated emission cross-sections of the most important transitions have been calculated and compared with laser results. Employing a 2-W laser diode as a continuous-wave pump source, we have been able to tune the emission wavelength in the range 1053-1074 nm. Active mode-locking yielding pulses of 9.6, 18, and 19.7 ps at the three main emission peaks of 1058.6, 1061.2, and 1065.3 nm, respectively. was also demonstrated.

Elimination of Hole–Surface Overlap in Graded CdSxSe1–x Nanocrystals Revealed by Ultrafast Fluorescence Upconversion Spectroscopy

Abstract: Interaction of charge carriers with the surface of semiconductor nanocrystals plays an integral role in determining the ultimate fate of the excited state. The surface contains a dynamic ensemble of trap states that can localize excited charges, preventing radiative recombination and reducing fluorescence quantum yields. Here we report quasi-type-II band alignment in graded alloy CdSxSe1–x nanocrystals revealed by femtosecond fluorescence upconversion spectroscopy. Graded alloy CdSxSe1–x quantum dots are a compositionally inhomogeneous nano-heterostructure designed to decouple the exciton from the nanocrystal surface. The large valence band offset between the CdSe-rich core and CdS-rich shell separates the excited hole from the surface by confining it to the core of the nanocrystal. The small conduction band offset, however, allows the electron to delocalize throughout the entire nanocrystal and maintain overlap with the surface. Indeed, the ultrafast charge carrier dynamics reveal that the fast 1–3 ps ho...

Radiative recombination in CuInSe2 thin films

Abstract: We perform a detailed analysis of the radiative recombination processes in CuInSe2 thin films grown by multisource physical vapor deposition The photoluminescence and photoluminescence excitation spectra are investigated as a function of stoichiometry, temperature and excitation intensity Using samples with a large composition gradient, we are able to obtain a coherent picture of the optical transitions in the films The broad–band photoluminescence spectrum typical for In–rich films breaks into a number of well–defined emission lines in Cu–rich CuInSe2 At low temperatures, emission peaks due to free–exciton, bound–exciton, and free–to–bound recombination are identified in Cu–rich films The spectra of In–rich films tend to be dominated by donor–acceptor transitions From the optical spectra, exciton ionization energies and the temperature dependence of the band gap are determined The observed optical transitions are related to intrinsic defectsWe perform a detailed analysis of the radiative recombination processes in CuInSe2 thin films grown by multisource physical vapor deposition The photoluminescence and photoluminescence excitation spectra are investigated as a function of stoichiometry, temperature and excitation intensity Using samples with a large composition gradient, we are able to obtain a coherent picture of the optical transitions in the films The broad–band photoluminescence spectrum typical for In–rich films breaks into a number of well–defined emission lines in Cu–rich CuInSe2 At low temperatures, emission peaks due to free–exciton, bound–exciton, and free–to–bound recombination are identified in Cu–rich films The spectra of In–rich films tend to be dominated by donor–acceptor transitions From the optical spectra, exciton ionization energies and the temperature dependence of the band gap are determined The observed optical transitions are related to intrinsic defects

Low-threshold lasing of InGaN vertical-cavity surface-emitting lasers with dielectric distributed Bragg reflectors

Abstract: Lasing action is achieved in InGaN vertical-cavity surface-emitting lasers (VCSELs) with dielectric distributed Bragg reflectors (DBRs). We fabricated III-nitride VCSELs by removing a SiC substrate from a III-nitride cavity with a dry etching technique and then wafer bonding the cavity and SiO2/ZrO2 DBRs. These VCSELs have a high quality factor of 460 and a spontaneous emission factor of 10−2. We observed lasing at a wavelength of 401 nm at room temperature with optical pumping. This lasing action was demonstrated at a low threshold of 5.1 mJ/cm2 by using a high-quality crystalline cavity and quantum-well layers without surface roughening or cracking.

Multifrequency room‐temperature continuous diode and Ar* laser‐pumped Er3+ laser emission between 2.66 and 2.85 μm

Abstract: cw pumped laser emission on six different wavelengths is obtained for the first time in a LiYF4:15% Er3+ crystal at room temperature under diode laser excitation for 2.66, 2.716, 2.81 μm emissions and under argon ion laser excitation for 2.77, 2.81, 2.84, 2.85 μm emissions. Threshold of 5 mW absorbed power at 0.795 μm (diode) is obtained for the 2.81 μm wavelength. Time and power evolution of the laser emissions are presented. The type of up‐conversion taking place during 2.81 μm laser emission is shown to be of the addition of photons by energy transfer (APTE) type involving a two‐photon summation which depopulates the 4I11/2 rather than the 4I13/2 state as up to now believed.