Se-Young Seo

Optical gain at 1.54 μm in erbium-doped silicon nanocluster sensitized waveguide

Optical gain at 1.54 μm in erbium-doped silicon-rich silicon oxide (SRSO) is demonstrated. Er-doped SRSO thin film was fabricated by electron-cyclotron resonance enhanced chemical vapor deposition of silicon suboxide with concurrent sputtering of erbium followed by a 5 min anneal at 1000 °C. Ridge-type single mode waveguides were fabricated by wet chemical etching. Optical gain of 4 dB/cm of an externally coupled signal at 1.54 μm is observed when the Er is excited via carriers generated in the Si nanoclusters by the 477 nm line of an Ar laser incident on the top of the waveguide at a pump power of 1.5 W cm−2.Optical gain at 1.54 μm in erbium-doped silicon-rich silicon oxide (SRSO) is demonstrated. Er-doped SRSO thin film was fabricated by electron-cyclotron resonance enhanced chemical vapor deposition of silicon suboxide with concurrent sputtering of erbium followed by a 5 min anneal at 1000 °C. Ridge-type single mode waveguides were fabricated by wet chemical etching. Optical gain of 4 dB/cm of an externally coupled signal at 1.54 μm is observed when the Er is excited via carriers generated in the Si nanoclusters by the 477 nm line of an Ar laser incident on the top of the waveguide at a pump power of 1.5 W cm−2.

Coefficient determination related to optical gain in erbium-doped silicon-rich silicon oxide waveguide amplifier

Gain-determining coefficients in Er-doped, nanocrystal-Si (nc-Si) sensitized silica waveguide amplifiers are investigated. Single-mode, Er-doped silica waveguides with nc-Si embedded in them were prepared by electron cyclotron resonance plasma-enhanced chemical vapor deposition of Er-doped a-Si:Ox (x<2) followed by a high-temperature anneal to precipitate nc-Si. Exciting the Er ions via nc-Si by pumping the waveguide from the top with the 477 nm line of an Ar laser resulted in an enhancement of the transmitted 1535 nm signal of up to 14 dB/cm, indicating a possible net gain of up to 7 dB/cm. From the dependence of the signal enhancement upon the pump power, an emission cross section of 2×10−19 cm2 at 1535 nm and an effective excitation cross section of ⩾10−17 cm2 at 477 nm is obtained.

Composition dependence of room temperature 1.54 μm Er3+ luminescence from erbium-doped silicon:oxygen thin films deposited by electron cyclotron resonance plasma enhanced chemical vapor deposition

The composition dependence of room temperature 1.54 μm Er3+ photoluminescence of erbium-doped silicon:oxygen thin films produced by electron cyclotron resonance plasma enhanced chemical vapor deposition of SiH4 and O2 with concurrent sputtering of erbium is investigated. The Si:O ratio was varied from 3:1 to 1:2 and the annealing temperature was varied from 500 to 900 °C. The most intense Er3+ luminescence is observed from the sample with a Si:O ratio of 1:1.2 after a 900 °C anneal and the formation of silicon nanoclusters embedded in the SiO2 matrix. The high active erbium fraction, efficient excitation via carriers, and high luminescence efficiency due to the high quality SiO2 matrix are identified as key factors in producing the intense Er3+ luminescence.

Intense blue–white luminescence from carbon-doped silicon-rich silicon oxide

The effect of carbon doping on the enhancement of visible luminescence from silicon-rich silicon oxide (SRSO), which consists of Si nanoclusters embedded inside a SiO2 matrix, is investigated. C-doped SRSO films were fabricated by electron cyclotron resonance-plasma enhanced chemical vapor deposition method using SiH4, O2, and CH4 source gases followed by a high-temperature anneal. Intense blue-white visible luminescence, visible to the naked eye under daylight conditions, was observed from the film with a nearly equal amount of C and excess Si (∼16 at. %) after an anneal at 950 °C. Furthermore luminescence could be tuned from 1.8 to 2.5 eV by controlling the C to excess Si ratio, the C content, and the anneal temperature. Taken together with the infrared absorption spectra, these results indicate that the luminescence is attributed to exciton recombination in C-incorporated Si nanoclusters.

Effect of nitride passivation on the visible photoluminescence from Si-nanocrystals

The effect of nitride passivation on the visible photoluminescence from nanocrystal Si (nc-Si) is investigated. Silicon-rich silicon nitride (SRSN) and silicon-rich silicon oxide (SRSO), which consist of nc-Si embedded in silicon nitride and silicon oxide, respectively, were prepared by reactive ultrahigh vacuum ion beam sputter deposition followed by a high temperature anneal. Both SRSN and SRSO display photoluminescence peaks after high temperature annealing, coincident with the formation of Si nanocrystals, and similar changes in the peak luminescence position with the excess Si content. However, the luminescence peak positions from SRSN are blueshifted by about 0.6 eV over that of comparable SRSO such that its luminescence peaks in the visible range. The results demonstrate that control of the surface passivation is critical in controlling the nc-Si luminescence, and indicate the possibility of using nitride-passivated nc-Si for visible luminescence applications including white luminescence.

Electron temperature control with grid bias in inductively coupled argon plasma

The mechanism of controlling electron temperature with grid-biased voltage is studied experimentally and the relevant physics is discussed in an inductively coupled Ar discharge. To obtain the electron density and electron temperature, the electron energy distribution functions (EEDFs) are measured with a Langmuir probe. As the grid voltage decreases negatively, the effective electron temperature is controlled from 2.0 to 0.6 eV and the electron density changes from 3×1010 to 2×1010 cm−3 in the diffusion region, while the effective electron temperature and electron density are not changed in the source region. The dependence of such various parameters, as electron density, electron temperature, plasma potential in each region, and so on, on the applied voltage, is presented. The functional relations between the measured physical quantities are well explained based on a global particle and energy balance relations.

Indirect excitation of Er3+ in sol-gel hybrid films doped with an erbium complex

Transparent sol-gel hybrid films doped with erbium tris 8-hydroxyquinoline were prepared using methyltriethoxysilane, vinyltriethoxysilane, and phenyltrimethoxysilane as precursors. We obtain a strong 1.53-μm Er3+ luminescence with a wide full width at half-maximum and no thermal quenching. Comparison of absorption of the film with the pump wavelength dependence of Er3+ luminescence intensity indicates the presence of an efficient indirect excitation path for Er3+ via organic ligands.

The Nd-nanocluster coupling strength and its effect in excitation/de-excitation of Nd3+ luminescence in Nd-doped silicon-rich silicon oxide

The Nd-nanocluster Si (nc-Si) coupling strength and its effect in excitation/de-excitation of Nd3+ luminescence in Nd-doped silicon-rich silicon oxide (SRSO) is investigated. Nd-doped SRSO thin films, which consist of nc-Si embedded inside a SiO2 matrix, were prepared by electron-cyclotron-resonance plasma-enhanced chemical vapor deposition of SiH4 and O2 with cosputtering of Nd and subsequent anneal at 950 °C. Efficient Nd3+ luminescence with moderate temperature quenching is observed. Based on an analysis of the temperature dependence of Nd3+ luminescence lifetime, we find a coupling strength between nc-Si and Nd that is strong enough to result in efficient excitation of Nd3+ via quantum-confined excitons, while weak enough to result in a small back-transfer rate is identified as the key to Nd3+ luminescence.

Exciton–erbium coupling and the excitation dynamics of Er3+ in erbium-doped silicon-rich silicon oxide

The exciton–erbium coupling and the excitation dynamics of Er3+ in erbium-doped silicon-rich silicon oxide are investigated using time-resolved measurements of Er3+ luminescence. The dependence of the Er3+ luminescence on the pump power and duration indicates that the exciton–erbium coupling is dominant over carrier–exciton coupling. The results further support the idea that the luminescent Er3+ ions are not in the Si nanoclusters but in the interface region surrounding the nanoclusters.

Photoluminescence of mesoporous silica films impregnated with an erbium complex

This work was supported by the Korea Science and Engneering Foundation(KOSEF, Grant No. R01-2000-000-00224-0)and by the Brain Korea 21 project.