Single-mode Nd3+-doped graded-index polymer waveguideamplifier

The first graded index (GRIN) polymer waveguide amplifier working at 1.06 μm wavelength has been realized, using a Nd³⁺: photolime gel material combination. Throughput intensity of 3.8 mW at 1.06 μm, corresponding to 8.5 dB gain, was observed when employing a 40 mW pumping laser beam operating at 790 nm. The gain medium is a 2.2 cm waveguide active region with Nd³⁺ concentration of 1.03×10²⁰/cm³. The GRIN characteristic of the photolime gel thin film provides a universal means for implementing polymer-based photonic integrated circuits (PICs) on any substrate of interest     

1.55 μm波段聚合物光波导放大器的研究

合成了铒镱共掺的三元配合物［Er1/2Yb1/2(HFA)3(TPPO)2］,并将其掺杂在聚甲基丙烯酸甲酯(PMMA)中,制备了铒镱共掺的聚合物光波导有源材料,对材料的吸收、发射特性进行了表征。在980 nm抽运光激发下,该配合物在1535 nm波长处的荧光半峰全宽为80 nm。针对该材料,建立了980 nm抽运光激发下的原子速率方程和光功率传输方程,理论计算了铒离子掺杂浓度、重叠积分因子、信号光发射截面等参数对铒镱共掺聚合物光波导放大器性能的影响。计算表明,当材料中铒离子的掺杂浓度为0.3×1020 cm-3时,在2 cm长的波导中可获得1.87 dB的光增益。     

Reliable Low-Cost Fabrication of Low-Loss $hbox{Al}_{2}hbox{O} _{3}{:}hbox{Er}^{3+}$ Waveguides With 5.4-dB Optical Gain

A reliable and reproducible deposition process for the fabrication of Al₂O₃ waveguides with losses as low as 0.1 dB/cm has been developed. The thin films are grown at ~ 5 nm/min deposition rate and exhibit excellent thickness uniformity within 1% over 50times50 mm² area and no detectable OH^- incorporation. For applications of the Al₂O₃ films in compact, integrated optical devices, a high-quality channel waveguide fabrication process is utilized. Planar and channel propagation losses as low as 0.1 and 0.2 dB/cm, respectively, are demonstrated. For the development of active integrated optical functions, the implementation of rare-earth-ion doping is investigated by cosputtering of erbium during the Al₂O₃ layer growth. Dopant levels between 0.2-5times10²⁰ cm^-3 are studied. At Er³⁺ concentrations of interest for optical amplification, a lifetime of the ⁴I_13/2 level as long as 7 ms is measured. Gain measurements over 6.4-cm propagation length in a 700-nm-thick Al₂O₃:Er³⁺ channel waveguide result in net optical gain over a 41-nm-wide wavelength range between 1526-1567 nm with a maximum of 5.4 dB at 1533 nm.     

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     

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     

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     

Improved gain performance in Yb3+-sensitized Er3+-doped alumina (Al2O3) channel opticalwaveguide amplifiers

Small-signal amplification in short, Yb³⁺-sensitized, Er³⁺-doped alumina (Al₂O₃) channel optical waveguides with high Er³⁺ concentrations is analyzed. Taking into account uniform up conversion, excited state absorption (ESA) from the Er³⁺ metastable level (⁴I_13/2 ), and Yb³⁺→Er³⁺ energy transfer by cross relaxation, the obtainable gain improvements compared to Yb³⁺ -free Er³⁺-doped Al₂O₃ optical waveguides are investigated. The amplifier model is based on propagation and population rate equations and is solved numerically by combining finite elements and the Runge-Kutta algorithm. The analysis predicts that 5-cm long Yb³⁺/Er³⁺ co-doped Al₂O ₃ waveguides show 13-dB net signal gain for 100 mW pump power at λ_p=980 nm     

Fiber-compatible K+-Na+ ion-exchanged channelwaveguides: fabrication and characterization

A systematic study of waveguides fabricated by K⁺-Na ⁺ exchange in soda-lime silicate and BK7 glasses is presented. The measured K⁺ concentration profile, the refractive index profile, and the diffusion profile obtained by solving the one-dimensional diffusion equation are correlated to explain the differences in the index profiles in the two glasses. The mobility of the potassium ions was measured by fabricating waveguides using electromigration. Surface waveguides formed by diffusion from a molten KNO₃ salt bath were buried by applying an electric field. Single-mode channel waveguides for operation at a wavelength of 1.3 μm that exhibit excellent mode matching with conventional optical fibers, achieving a fiber-waveguide insertion loss of less than 1 dB for a 20-mm-long waveguide, have been obtained     

Enhancement of fluorescence emission and signal gain at 1.53 µm in Er3+/Ce3+ co-doped tellurite glass fiber

Er3+/Ce3+ co-doped tellurite glasses with composition of TeO2-GeO2-Li2O-Nb2O5 were prepared using conventional melt-quenching technique for potential applications in Er3+-doped fiber amplifier (EDFA). The absorption spectra, up-conversion spectra and 1.53 µm band fluorescence spectra of glass samples were measured. It is shown that the 1.53 µm band fluorescence emission intensity of Er3+-doped tellurite glass fiber is improved obviously with the introduction of an appropriate amount of Ce3+, which is attributed to the energy transfer (ET) from Er3+ to Ce3+. Meanwhile, the 1.53 µm band optical signal amplification is simulated based on the rate and power propagation equations, and an increment in signal gain of about 2.4 dB at 1 532 nm in the Er3+/Ce3+ co-doped tellurite glass fiber is found. The maximum signal gain reaches 29.3 dB on a 50 cm-long fiber pumped at 980 nm with power of 100 mW. The results indicate that the prepared Er3+/Ce3+ co-doped tellurite glass is a good gain medium applied for 1.53 µm broadband and high-gain EDFA.     

Thin Film Filter for Broadband IR Integrated Waveguide Amplifiers

A new S-type of IR integrated waveguide amplifiers, based on erbium-ytterbium co-doped phosphate glass integrated with medium thin film filter, is proposed. The intrinsical gain spectrum of the proposed amplifier is obtained by solving rate and power propagation equations, a thin film filter flattening this intrinsical gain spectrum is designed by genetic algorithm, and fabricated. An average gain >10dB is obtained between 1530nm and 1560nm, and the average gain about 18dB between 1531nm and 1550nm with gain difference of <3dB is achieved.     

A high-gain monolithic D-band InP HEMT amplifier

This paper describes a three-stage monolithic amplifier that exhibits a small-signal gain of 30 dB at 140 GHz. The amplifier employs AlInAs/GaInAs/InP high electron mobility transistor devices with 0.1×150 μm² gate periphery, is implemented with coplanar waveguide circuitry fabricated on an InP substrate, and occupies a total area of 2 mm². Gain exceeding 10 dB was measured on-wafer from 129 to 157 GHz. This is the highest reported gain per stage for a transistor amplifier operating at these frequencies     

Er3+-doped fiber amplifier pumped by 0.98 μm laserdiodes

The performance of an Er³⁺-doped fiber amplifier pumped by 0.98 μm InGaAs laser diodes (LDs) is reported. By using a fiber with low Er³⁺ content and optimizing the fiber length, a maximum signal gain of 37.8 dB at 30-mW pump power was realized at a signal wavelength of 1.536 μm. A maximum gain coefficient of 1.9 dB/mW at 14 mW pump power was achieved. It was found that the fiber amplifier pumped by the 0.98-μm LDs is twice as efficient as that pumped by 1.48-μm LDs, from the viewpoint of both required fiber length and the attained gain     

Numerical simulation of ion-exchange in glass for integratedoptical components

A numerical model based on the finite-element method for solving the nonlinear diffusion equation of ion-exchange in glasses is presented. The model is applied to the calculation of the concentration profile for a Ag⁺-Na⁺ ion-exchanged channel waveguide. The calculated concentration profile is in good agreement with a measured refractive-index profile of a waveguide fabricated with the same parameters as used in the calculations     

On the Temperature-Dependent Gain and Noise Figure Analysis of C-Band High-Concentration EDFAs With the Effect of Cooperative Upconversion

We present an efficient temperature-dependent analysis to study the effect of cooperative upconversion on the temperature-dependent gain (TDG) performance of the C-band erbium-doped fiber amplifier (EDFA) at high-concentration. The influence of cooperative upconversion on the TDG is examined by using a set of temperature-dependent rate and light propagation equations. In the analysis given, the amplified spontaneous emission (ASE), as well as the excited state absorption (ESA) are also considered. In the forward pumping configuration at a signal wavelength of 1547 nm and in the temperature range of - 40degC to + 80degC, the variations of the TDG and the noise figure (NF) are about 1.7 and 0.9 dB, respectively. Numerical analysis results show that, with 260-mW/1480-nm pump power, an erbium-doped fiber amplifier having a doping concentration of 4.4 times 10²⁶ ion/m³ and optimum length of 9.2 cm may reach a signal gain of 44.6 dB and a noise figure of 3.9 dB at room temperature.     

铒镱共掺磷酸盐玻璃波导放大器及上转换性质

研究了采用离子交换和电场辅助退火法制作的铒镱共掺磷酸盐波导放大器的增益特性,测量了Er2O3,Yb2O3掺杂浓度分别为2.2wt%和4.7wt%,长度为1.2cm的器件增益,在130mW,976nm泵浦光泵浦下,输入信号光功率小于1mW时,在1535nm处得到8.5dB的小信号相对增益;当泵浦功率为30mW时,可观测到绿色的上转换辐射光,发光强度随泵浦功率增加而增大;通过单色仪和光电倍增管接收此光,确定是铒粒子由2H11/2和4S3/2能级分别跃迁至基态的上转换辐射光.     

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     

Compact high gain erbium-ytterbium doped waveguide amplifier fabricated by Ag-Na ion exchange

A report is presented on an erbium-ytterbium doped waveguide amplifier fabricated by Ag-Na ion-exchange in a commercial phosphate glass substrate. The 31 mm-long active waveguide provides a maximum internal gain of 5.3 dB/cm at 1534 nm. The amplifier was fully characterised in terms of gain spectrum, noise figure, pump efficiency and gain saturation.     

A Packaged and ESD-Protected Inductorless 0.1–8 GHz Wideband CMOS LNA

In this letter, an inductorless 0.1-8 GHz wideband CMOS differential low noise amplifier (LNA) based on a modified resistive feedback topology is proposed. Without using any passive inductors, the modified resistive feedback technique implemented with a parallel R-C feedback, an active inductor load, and neutralization capacitors achieves high gain, low noise, and good return loss over a wide bandwidth. To ensure the robustness in the system integration, electro-static discharge diodes are added to the radio frequency pads. The LNA was fabricated using a digital 90 nm CMOS technology. It achieves a 3 dB bandwidth of 8 GHz with a 16 dB voltage gain, noise figures from 3.4 dB to 5.8 dB across the whole band, and an input third-order intermodulation product (IIP3) of -9 dBm. The active area of the chip is 0.034 mm². The chip was packaged and tested on an FR4 PCB using the chip-on-board approach.     

1.3μm高增益偏振无关应变量子阱半导体光放大器

采用低压金属有机化学气相外延法 (LP MOVPE)生长并制作了 1 3μm脊型波导结构偏振无关半导体光放大器 (SOA) ,有源区为基于四个压应变量子阱和三个张应变量子阱交替生长的混合应变量子阱 (4C3T)结构 ,压应变阱宽为 6nm ,应变量 1 0 % ,张应变阱宽为 11nm ,应变量 - 0 95 % ;器件制作成 7°斜腔结构以有效抑制腔面反射。半导体光放大器腔面蒸镀Ti3 O5/Al2 O3 减反 (AR)膜以进一步降低腔面剩余反射率至 3× 10 -4以下 ;在 2 0 0mA驱动电流下 ,光放大器放大的自发辐射 (ASE)谱的 3dB带宽大于 5 0nm ,光谱波动小于 0 4dB ,半导体光放大器管芯的小信号增益近 30dB ,在 12 80～ 1340nm波长范围内偏振灵敏度小于 0 6dB ,饱和输出功率大于 10dBm ,噪声指数 (NF)为 7 5dB。     

Design and Application of Compact and Highly Tolerant Polarization-Independent Waveguides

In this paper, the design, fabrication, and application of a highly tolerant polarization-independent optical-waveguide structure suited for operation in the third communication window is presented. The waveguide structure has been optimized toward minimized sensitivity to technological tolerances and low fabrication complexity. The tolerance analysis has been based on the typical processing tolerances of the widely applied silicon-oxynitride technology, being plusmn3times10 ^-4 in refractive index, plusmn1% in thickness, and plusmn0.1 mum in channel width. The optimized waveguide design fulfills the criterion of a channel birefringence within 5times10^-5, including processing tolerance. It also enables a fiber-to-chip coupling loss below 1 dB/facet and is suited for the realization of low-loss bends with a radius down to 600 mum. Based on this waveguide design, a passband-flattened optical wavelength filter with 50-GHz free spectral range has been realized and tested. The measured TE-TM shift of 0.03 nm confirms the polarization dependence of the optical waveguides being as low as 3times10^-5