Modeling of Yb3+-sensitized Er3+-doped silicawaveguide amplifiers

A model for Yb³⁺-sensitized Er³⁺-doped silica waveguide amplifiers is described and numerically investigated in the small-signal regime. The amplified spontaneous emission in the ytterbium-band and the quenching process between excited erbium ions are included in the model. For pump wavelengths between 860 and 995 nm, the amplified spontaneous emission in the ytterbium-band is found to reduce both the gain and the optimum length of the amplifier significantly. The achievable gain of the Yb³⁺-sensitized amplifier is found to be higher than in an Er³⁺-doped silica waveguide without Yb ³⁺ (18 dB versus 9 dB for a pump power of 100 mW). However, it is important to optimize the Yb-concentration according to the choice of pump wavelength     

Modeling and optimization of short Yb3+-sensitized Er3+-doped fiber amplifiers

Short high-concentration Yb³⁺-sensitized Er³⁺-doped fiber amplifiers are modeled and numerically investigated in the small-signal domain. Concentration quenching is included with a term quadratic in the concentration of excited Er³⁺ . We find that for fibers shorter than 1 m, the small-signal gain can be larger for sensitized fibers than for non-sensitized ones (31 dB gain vs. 22 dB at 5 cm). Without concentration quenching (e.g. for long fibers), Yb³⁺-free amplifiers have a higher small-signal gain. The achievable gain of the sensitized amplifier is independent of the pump laser wavelength, if the Yb-concentration is correspondingly optimized. However, restrictions on allowable Yb-concentrations imply that for a specific pump wavelength, a finite range of amplifiers lengths is suitable     

Er3+-doped Al2O3 thin films byplasma-enhanced chemical vapor deposition (PECVD) exhibiting a 55-nmoptical bandwidth

We report the first deposition of Er³⁺-doped aluminum oxide thin-film optical waveguides by plasma-enhanced chemical vapor deposition (PECVD). The aluminum and erbium precursors used for the deposition of the thin films were trimethyl-aluminum and Er tri-chelate of 2,2,6,6-tetramethylheptane-3,5 dione respectively. The samples show broad, room-temperature photoluminescence at λ=1.533 μm. The Er³⁺ concentration ranged from 0.01-0.2 at%. The full width half maximum (FWHM) of the Er³⁺ emission spectrum is 55 nm, considerably broader than in silica glass. The radiative lifetime has been measured at 50-mW pump power     

中频溅射技术制备镱铒共掺Al2O3光波导

在硅单晶(100)衬底上用热氧化法氧化一层SiO₂做缓冲层,在高纯铝靶上镶嵌金属Yb,Er,然后用中频磁控溅射法制备了镱铒共掺杂氧化铝薄膜。讨论了靶电压及沉积速率随氧流量的变化的磁滞回线效应,分析得出了沉积氧化物薄膜的最佳氧流量。在室温下检测到了薄膜的位于1535nm的很强的光致发光光谱(PL),并在光学掩模下用BCl₃离子束对薄膜样品进行刻蚀,得到条形光波导。     

Performance of high-concentration Er3+-doped phosphatefiber amplifiers

The performances of high-concentration Er³⁺-doped phosphate fiber amplifiers are reported. The amplifiers are characterized in terms of gain, noise figure, and signal saturation power in a co-propagating pump configuration. A net gain of 21 dB and a gain per unit length 3 dB/cm are achieved in a 71-mm Er³⁺-doped phosphate fiber     

Concentration-dependent luminescence properties in Er3+-doped TeO2-ZnO-La2O3 glasses

Erbium-doped tellurite-based glasses(Er3+:TeO2-ZnO-La2O3) are prepared by the conventional melt-quenching technique,and concentration-dependent luminescence properties of Er3+ are investigated.A significant spectral broadening of the 1.53 μm fluorescence corresponding to 4I13/2 →4I15/2 transition is observed,and the fluorescence decaying becomes a nearly exponential way with the increasing Er3+concentration.Radiation trapping is evoked to explain the broadening of 4I13/2 → 4I15/2 emission line of Er3+ ions.The optimum doping content of Er2O3 for 1.53 μm fluorescence emission is about 1.5 mol%.     

Spectral noise figure of Er3+-doped fiber amplifiers

The erbium-doped fiber amplifier noise figure spectrum and its evolution under various pumping regimes is analyzed. The analysis shows that noise figures in the range ±0.15 dB around the 3-dB quantum limit are possible within a spectral band of 50 nm. This demonstrates the possibility of quantum-limited amplification for broadband wavelength-division multiplexed (WDM) signals     

Improved gain characteristics in high-concentrationEr3+/Yb3+ codoped glass waveguide amplifiers

High-concentration Er³⁺/Yb³⁺ codoped glass waveguide amplifiers are analyzed by means of a finite-element-based code. Efficient Yb³⁺ to Er³⁺ energy transfer is shown to be a useful mechanism to reduce performance degradation due to Er³⁺ ion-ion interactions. Numerical calculations based on realistic waveguide parameters demonstrate the possibility of achieving high gain with a short device length     

Diode-array pumping of Er3+/Yb3+ Co-dopedfiber lasers and amplifiers

Single-mode double-clad Er³⁺/Yb³⁺ co-doped fibers are shown to be suitable for diode array pumping at around 960 nm. A fiber laser with 96-W output power at 1.53 μm and a power amplifier exhibiting a small signal gain of 24 dB and a saturated output power of +17 dBm are reported     

掺Er~（3＋）和掺Er~（3＋）／Yb~（3＋）光纤中1313nm到780nm的频率上转换过程

研究了在连续锁模和调Ｑ锁模两种脉冲泵浦条件下，掺Ｅｒ（３＋）和掺Ｅ３＋／Ｙｂ３＋单模ＧｅＯ２／ＳｉＯ２石英光纤中，１３１３ｎｍＮｄ：ＹＬＦ激光到７８０ｎｍ波长的频率上转换过程。Ｅｒ３＋离子在共振吸收两个光子后到４Ｆ９／２态，再经快速的无辐射转移到４Ｉ９／２态．形成７８０ｎｍ辐射。在连续锁模泵浦条件下．１３１３ｎｍ至７８０ｎｍ的转换效率比调Ｑ锁模条件下更高．而后者的峰值功率是前者的几百倍。     

Concentration-dependent 4I13/2 lifetimes inEr3+-doped fibers and Er3+-doped planar waveguides

We report on the concentration- and pump-dependent lifetimes of the spontaneous emission in Er³⁺-doped fibers and Er³⁺ -doped waveguides. In addition, we measure the concentration dependence of the 550-nm fluorescence due to excited state absorption (ESA)     

Temperature dependence of signal gain in Er3+-dopedoptical fiber amplifiers

Temperature-dependent signal gain characteristics at signal wavelengths of 1.536 and 1.552 μm in Er³⁺-doped optical fibers with a temperature range of -40 to 80°C are reported for 0.98 and 1.48 μm pumping. The temperature dependences of signal gain strongly depend on fiber length, pump wavelength, and signal wavelength. The fiber length at which signal gain temperature insensitivity occurs is found for the amplification of a 0.98-μm-pump-1.536-μm-signal, a 0.98-μm-pump-1.552-μm-signal, and a 1.48-μm-pump-1.536-μm-signal. It is confirmed theoretically that the temperature dependences result from linear changes in the fluorescence, and absorption cross sections at the signal and pump wavelengths, and a shift in the effective pump wavelength     

Photoelectrochemical performance of La3+-doped TiO2

La-doped TiO₂ thin films on titanium substrates were prepared by the sol-gel method with titanium tetrachloride as a precursor and La₂O₃ as a source of lanthanum. The heat-treatment temperature dependence of the photoelectrochemical performance of the La-doped TiO₂ film in 0.2 mol/L Na₂SO₄ was investigated by the Mott-Schottky equation, electrochemical impedance spectroscopy, and the open-circuit potential test. The results from the Mott-Schottky curves show that the obtained films all were n-type semiconductors, and the film at 300 ℃ had the highest conduction band position and the widest space charge layer. The electrochemical impendence spectroscopy (EIS) tests of the 300 ℃ film decreased most during the change from illuminated to dark. The potential of the La-TiO₂ thin film electrode was the lowest after the 300 ℃ heat treatment. The open-circuit potential indicated that the photoelectrical performance of the La-TiO₂ films was enhanced with the addition of the La element and the largest decline (837.8 mV) in the electrode potential was achieved with the 300 ℃ heat treatment.     

The effect of pair-induced energy transfer on the performance ofsilica waveguide amplifiers with high Er3+/Yb3+concentrations

High-concentration Er³⁺/Yb³⁺ co-doped silica waveguide amplifiers are numerically analyzed. With optimized rare-earth concentrations the effect of Er³⁺/Er³⁺ ion-pairs can be neglected and each Er³⁺ ion can be assumed to be paired only to the surrounding Yb³⁺ ions. The rate-equations model includes uniform upconversion mechanisms from ⁴I_13/2 and ⁴I_11/2 erbium levels and an Yb³⁺ to Er³⁺ pair-induced energy transfer process. Numerical results demonstrate the possibility of fabricating short- and high-gain integrated optical amplifiers; it is shown that net gain as high as 3 dB/cm can be obtained     

Stable relaxation-oscillation Er3+-doped fiber laser

We demonstrate a simple method to produce high-energy pulses with peak powers up to 100 times their average power and with duration on the order of 1 μs using the synchronization of relaxation oscillations by drive current modulation of the intracavity pump laser diode. The forced sustained relaxation oscillations are shown to depend on wavelength, and the frequency locking curve exhibits a strong asymmetry with hysteresis behavior     

Yb3+-doped photonic crystal fibre laser

An ytterbium doped core has been incorporated into a photonic crystal fibre (PCF) with anomalous group velocity dispersion at all wavelengths longer than 730 nm. Laser action is observed for the first time in such a fibre. This demonstration of lasing in PCF is a vital step towards realising the huge potential of PCF for fibre laser applications     

Anomalous dispersion in Er3+ and Yb3+-dopedfibers

In experimental and theoretical study of anomalous dispersion in Er³⁺and Er³⁺-Yb³⁺-doped fibers has been developed. Anomalous time delay caused by both absorption and emission at 1.535 μm has been theoretically calculated and experimentally measured. A pump power dependence of anomalous time delay in rare-earth-doped fibers has been theoretically calculated and experimentally investigated. It has been shown that pump power fluctuations lead to propagation time jitter in Er³⁺-doped fiber amplifiers. The pulse interaction due to refractive index change caused by gain saturation is predicted. It has been shown that for Er ³⁺-doped fibers with SiO₂-GeO₂ core composition, the anomalous dispersion per 1-dB gain is twice that of fibers with SiO₂-Al₂O₃ core, which is caused by gain curve form difference. A scheme of mutual compensation of intrinsic fiber dispersion and anomalous dispersion caused by Er³⁺ in the region 1.532-1.537 μm has been suggested     

Optical amplification in Er3+-doped single-mode fluoridefiber

The amplification characteristics at around 1.5 μm of a 0.9-m-long, 1000-p.p.m Er³⁺-doped single-mode fluoride fiber are discussed. By using 1.48-μm laser diodes with 55-mW launched output as a pump source, a gain of 1.75 dB was obtained at 1.530 μm. A broad bandwidth of 40 nm was obtained, which may be suitable for wavelength-division multiplexing (WDM) system use     

Multichannel amplification utilizing an Er3+-doped fiberamplifier

An Er³⁺-doped fiber amplifier for multichannel systems was studied from the viewpoint of clarifying the ultimate capacity of the applicable number of channels. In these experiments, 10-GHz spaced 100-channel common amplification was carried out in a 622-Mb/s frequency-shift-keying (FSK) direct detection scheme, together with measurement of the amplifier characteristics. Bit-error-rate measurements show that the power-penalty characteristics for 100-channel amplification are the same as for one-channel amplification. Based on the experimental results, possible channel capacity is discussed. There are two possible factors limiting channel capacity in multichannel amplification of fiber amplifiers: signal-gain bandwidth and amplifier noise. Calculations using the amplifier parameters obtained during the experiments reveal that signal gain bandwidth is the main factor limiting channel capacity in the amplifier used     

Electrical and interfacial characteristics of nanolaminate (Al2O3/ZrO2/Al2O3) gate stack on fully depleted SiGe-on-insulator

The structural and electrical characteristics of a novel nanolaminate Al₂O₃/ZrO₂/Al₂O₃ high-k gate stack together with the interfacial layer (IL) formed on SiGe-on-insulator (SGOI) substrate have been investigated. A clear layered Al₂O₃ (2.5 nm)/ZrO₂ (4.5 nm)/Al₂O₃ (2.5 nm) structure and an IL (2.5 nm) are observed by high-resolution transmission electron microscopy. X-ray photoelectron spectroscopy measurements indicate that the IL contains Al-silicate without Ge atom incorporation. A well-behaved C–V behavior with no hysteresis shows the absence of Ge pileup or Ge segregation at the gate stack/SiGe interface.