Jae Tae Seo

Visible Laser Action of Dy3+ Ions in Monoclinic KY(WO 4) 2 and KGd(WO 4) 2 Crystals under Xe-Flashlamp Pumping

Pulsed laser action in the novel visible laser channels 4F9/2→6H13/2 (at ≈0.57 µm) and 4F9/2→6H11/2 (at ≈0.66 µm) of Dy3+ ions in monoclinic KY(WO4)2 and KGd(WO4)2 single crystals at nitrogen cryogenic temperature under Xe-flashlamp pumping is excited for the first time. All observed lasing emissions are identified. Some spectroscopic characteristics of the investigated crystals are also presented.

Optical nonlinearities of Au nanoparticles and Au/Ag coreshells

Au nanoparticles exhibited both negative and positive nonlinear absorptions with ground-state plasmon bleaching and free-carrier absorption that could be origins of the saturable and reverse-saturable optical properties. Au/Ag coreshells displayed only positive nonlinear absorption and reverse-saturable optical properties as a function of excitation intensity at the edge of surface-plasmon resonance, which implies no ground-state plasmon bleaching and the existence of two-photon absorption.

Thermal Quenching of Photoluminescence from Er-Doped GaN Thin Films

Abstract The green (537 and 558 nm) and near infrared (1.54 μm) photoluminescence (PL) spectra of Er-doped GaN thin films have been investigated as a function of temperature, excitation wavelength, and pump intensity. Thermal quenching measurements showed that the integrated green Er 3+ PL intensity ( 4 S 3/2 / 2 H 11/2 → 4 I 15/2 ) remained nearly constant up to 150 K, but decreased at higher temperatures due to a less efficient Er 3+ excitation. The integrated infrared Er 3+ PL intensity ( 4 I 13/2 → 4 I 15/2 ) was found to be temperature-independent up to 250 K, but decreased slightly at higher temperatures due to the onset of non-radiative decay. Pump intensity PL studies revealed that the above-gap excitation cross-section is more than two orders of magnitude greater than the below-gap excitation cross-section. Within a simplified three-level model, the above-gap excitation cross-section was estimated to be ∼10 −16 cm 2 . This result indicates that Er 3+ ions can be excited efficiently through carrier-mediated processes in a forward-biased GaN:Er light emitting device.

Near infrared (1.54 μm) luminescence properties of erbium doped gallium nitride

Abstract The photoluminescence (PL) properties of in-situ Er doped GaN prepared by metalorganic molecular beam epitaxy (MOMBE) have been investigated. The GaN:Er films were grown on sapphire or silicon substrates. The oxygen and carbon background concentrations in the films were measured to be in the order of ∼10 20 and ∼10 21 cm −3 , respectively. Both types of GaN:Er samples showed intense 1.54 μm PL at room temperature under below-gap optical excitation. For above-gap excitation, a greatly reduced Er 3+ luminescence intensity was observed. Pump intensity dependent PL studies revealed that the Er 3+ excitation efficiency under above-gap excitation is roughly a factor of ∼30 smaller compared to below-gap excitation. Based on the efficient Er 3+ below-gap excitation process a hybrid GaN:Er/sapphire/InGaN LED was developed.

Slow and Fast Light Using Stimulated Rayleigh-Wing Scattering

Stimulated Rayleigh-Wing Scattering has been found to be a perfect way for group velocity controlling. The velocity of a pulse can be exactly controlled by tuning the wavelength and intensity of a strong CW beam.

Controlling of the Group Velocity Using Third-Order Nonlinearity

Third-order nonlinearity of optical material has been found to be very useful for group velocity controlling. The velocity of a pulse may be changed by tuning its intensity or using an extra CW pump.

Near IR and visible photoluminescence from Er doped III-nitride semiconductors

Summary form only given. We present new spectroscopic results from MOMBE grown Er doped GaN. An overview of the PL from GaN:Er/sapphire observed under below-gap (442 nm) pumping is given. The near infrared PL peaking at 1.54 /spl mu/m is assigned to the intra-4f-subshell Er transition /sup 4/I/sub 13/2//spl rarr//sup 4/I/sub 15/2/. The red emission line at 668 nm is attributed to the Er/sup 3+/ transition /sup 4/F/sub 9/2//spl rarr//sup 4/I/sub 15/2/.