Co-doped Waveguide Amplifiers Research Articles

Design of an on-chip wavelength conversion device assisted by an erbium-ytterbium co-doped waveguide amplifier

In current documented studies, it has been observed that wavelength converters utilizing AlGaAsOI waveguides exhibit suboptimal on-chip wavelength conversion efficiency from the C-band to the 2 μm band, generally falling below −20.0 dB. To address this issue, we present a novel wavelength conversion device assisted by a waveguide amplifier, incorporating both AlGaAs wavelength converter and erbium-ytterbium co-doped waveguide amplifier, thereby achieving a notable conversion efficiency exceeding 0 dB. The noteworthy enhancement in efficiency can be attributed to the specific dispersion design of the AlGaAs wavelength converter, which enables an upsurge in conversion efficiency to −15.54 dB under 100 mW of pump power. Furthermore, the integration of an erbium-ytterbium co-doped waveguide amplifier facilitates a loss compensation of over 15 dB. Avoiding the use of external optical amplifiers, this device enables efficient and high-bandwidth wavelength conversion, showing promising applications in various fields, such as optical communication, sensing, imaging, and beyond.Graphical

On-chip integrated few-mode erbium–ytterbium co-doped waveguide amplifiers

We propose for the first time, to the best of our knowledge, an on-chip integrated few-mode erbium–ytterbium co-doped waveguide amplifier based on an 800 nm thick Si3N4 platform, which demonstrates high amplification gains and low differential modal gains (DMGs) simultaneously. An eccentric waveguide structure and a co-propagating pumping scheme are adopted to balance the gain of each mode. A hybrid mode/polarization/wavelength-division (de)multiplexer with low insertion loss and crosstalk is used for multiplexing and demultiplexing in two operation wavebands centered at 1550 nm and 980 nm, where the light in these two bands serves as the signal light and pump light of the amplifier, respectively. The results demonstrate that with an input signal power of 0.1 mW, TE0 mode pump power of 300 mW, and TE1 mode pump power of 500 mW, the three signal modes (TE0/TM0/TE1) all exhibit amplification gains exceeding 30 dB, while maintaining a DMG of less than 0.1 dB.

Performance Enhancement of Er–Yb: Co-doped Waveguide Amplifier Employing Backward Pumping in the Presence of Energy Transfer Upconversion

Performance Enhancement of Er–Yb: Co-doped Waveguide Amplifier Employing Backward Pumping in the Presence of Energy Transfer Upconversion

Gain optimization of an erbium-ytterbium co-doped amplifier via a Si3N4 photonic platform.

Erbium-doped waveguide amplifiers enable the integration of various active functions on a silicon platform. Er3+ can provide the basis for efficient optical amplification of photonic integrated circuits, but the gain is limited by cooperative upconversion leading to doping concentration limitations and insufficient optimization of the waveguide structure. In this paper, an erbium-ytterbium co-doped Al2O3 amplifier has been innovatively implemented on a low loss Si3N4 waveguide by careful design and optimization with the finite difference method. A more accurate and comprehensive theoretical model of erbium-ytterbium co-doping is established, with consideration of upconversions, energy transfer, amplified spontaneous radiation and propagation loss to perform optimization of the high-gain erbium-ytterbium co-doped waveguide amplifier. The optimized waveguide amplifier achieves a small-signal gain of more than 36 dB at 1550 nm under Er3+ concentration of 3 × 1020 cm-3 and Yb3+ concentration of 3 × 1021 cm-3. Endowing Si3N4 photonic integrated circuits with gain can enable the miniaturization of various on-chip based active devices.

Design of a Few-Mode Erbium-Ytterbium Co-Doped Polymer Optical Waveguide Amplifier With Low Differential Modal Gain

Mode-division multiplexing (MDM) is a new method of space-division multiplexing (SDM) that can break through the limitation of single-mode transmission capacity and greatly improve the capacity of optical fiber communication. In the case of a few-mode (FM) system, it is possible that each mode can carry its own data steam and transmit long distances owing to a few-mode erbium-doped fiber amplifier (FM-EDFA). In addition, an Er3+-Yb3+ co-doped waveguide amplifier (EYCDWA) based on polymer materials has numerous advantages of miniaturization and flexibility in planar integrated optics compared with the EDFA. This study explored the theory of a few-mode Er3+-Yb3+ co-doped waveguide amplifier (FM-EYCDWA) and established a theoretical model of an FM-EYCDWA with a novel modified overlap integral factor. The differential modal gain (DMG) of the FM-EYCDWA can be reduced or even eliminated by equalizing the modified overlap integral factor of each signal mode. An unprecedented doping configuration adapted to the fabrication process of an optical waveguide was proposed to fill the gap between modal gains, which can be optimized by a genetic algorithm (GA). We investigated two optimization cases of three-mode and five-mode group FM-EYCDWAs to verify the validity of the theoretical model; both cases were optimized to minimize the DMGs under the same limitations, and excellent performance was presented, which demonstrated that the design method of the few-mode amplifiers we presented can offer a referable guideline.

Erbium-ytterbium co-doped aluminium oxide waveguide amplifiers fabricated by reactive co-sputtering and wet chemical etching.

We report on the fabrication and optical characterization of erbium-ytterbium co-doped aluminum oxide (Al2O3:Er3+:Yb3+) waveguides using low-cost, low-temperature deposition and etching steps. We deposited Al2O3:Er3+:Yb3+ films using reactive co-sputtering, with Er3+ and Yb3+ ion concentrations ranging from 1.4-1.6 × 1020 and 0.9-2.1 × 1020 ions/cm3, respectively. We etched ridge waveguides in 85% pure phosphoric acid at 60°C, allowing for structures with minimal polarization sensitivity and acceptable bend radius suitable for optical amplifiers and avoiding alternative etching chemistries which use hazardous gases. Scanning-electron-microscopy (SEM) and profilometry were used to assess the etch depth, sidewall roughness, and facet profile of the waveguides. The Al2O3:Er3+:Yb3+ films exhibit a background loss as low as 0.2 ± 0.1 dB/cm and the waveguide loss after structuring is determined to be 0.5 ± 0.3 dB/cm at 1640 nm. Internal net gain of 4.3 ± 0.9 dB is demonstrated at 1533 nm for a 3.0 cm long waveguide when pumped at 970 nm. The material system is promising moving forward for compact Er-Yb co-doped waveguide amplifiers and lasers on a low-cost silicon wafer-scale platform.

Er–Yb codoped waveguide/Raman hybrid optical amplifier with enhanced gain for DWDM system

A hybrid optical amplifier, using a combination of Er–Yb codoped waveguide amplifier (EYDWA) and Raman amplifier, is presented. The proposed scheme is investigated for 116 × 10 Gb / s dense wavelength-division multiplexed (DWDM) system at 0.2-nm channel spacing. The parameters are optimized using a hybrid genetic algorithm to achieve a flat gain of >25 dB, with a gain ripple of 2.78 dB. This is obtained over a wavelength range of 1539.7 to 1562.7 nm at 1 mW optimum input power per channel, without using any costly gain flattening scheme. An increase in gain ripple from 2.78 to 6.95 dB is observed for higher input powers up to 10 mW. The obtained noise figure (NF) is 10 dB) confirm the feasibility of the proposed amplifier for broadband long-haul DWDM systems.

Achieving high gain using Er-Yb codoped waveguide/fiber optical parametric hybrid amplifier for dense wavelength division multiplexed system

A hybrid optical amplifier is proposed using a combination of Er-Yb codoped waveguide amplifier (EYDWA) and fiber optical parametric amplifier (FOPA). The scheme is investigated for 100 × 40 Gb / s dense wavelength division multiplexed (DWDM) system at 0.2-nm channel spacing. The parameters are optimized to achieve a flat gain of >30.6 dB, with a gain ripple of 2.67 dB. This is obtained over a wavelength range of 1542 to 1562 nm at −10-dBm optimum input power per channel, without using any costly gain flattening scheme. For higher input powers up to 10 dBm, an increase in gain ripple from 2.67 to 6.13 dB is observed. The gain ripple of 2.67 dB of the proposed EYDWA–dual pump FOPA configuration is also much better than 10.32 dB for the hybrid EYDWA–single pump FOPA. The obtained high and flat gain, along with the low noise figure, confirms the usefulness of the proposed amplifier for applications in long-haul DWDM systems.

Cooperative upconversion effects on the characteristics of Er3+ doped and Er3+/Yb3+ co-doped waveguide amplifiers

By solving the rate equations and the propagation equations based on the energy transfer process of Er3+ and Yb3+ ions, the effects of the cooperative upconversion (UC) on the gain and noise characteristics of the Er3+ doped and Er3+/Yb3+ co-doped waveguide amplifiers are analyzed. Comparisons are performed between the amplifiers on waveguide length, pump power, Er3+ ion concentration and ion concentration ratio NYb/NEr, respectively. Results show that it is very necessary to consider the UC in the optimization design and analysis of waveguide amplifiers.

A numerical method for solving gain characteristics of Er3+/Yb3+ codoped waveguide amplifiers

By means of the interpolation and iteration methods to deal with the rate equations and the light propagation equations for the Er3+/Yb3+ codoped waveguide amplifier (EYCDWA), the gain characteristics in the forward, backward, and bidirectional pumped styles are analyzed. In order to obtain high gain, some parameters such as waveguide length, dopant concentration, pump power, and signal power are optimized. The results show that the pump power and signal power are about 50mW and 1mW, respectively, the gain is about 6.5dB for the 2.0cm-long EYCDWA with an Er3+ ion concentration of 1.5×1026m–3 and Yb3+ ion concentration of 1.9×1027m–3. Moreover, the upconversion is investigated for the designed device.

Gain and noise characteristics of phosphate glass $$\hbox {Er}^{3+}$$ Er 3 + – $$\hbox {Yb}^{3+}$$ Yb 3 + co-doped waveguide amplifiers

Under the conditions of the uniform doping and the steady state, simulation is performed for the phosphate glass $$\hbox {Er}^{3+}$$ – $$\hbox {Yb}^{3+}$$ co-doped waveguide amplifier by using a formulized iteration method to solve the rate equations and the propagation equations. In the simulation, we have considered ion-ion interaction mechanisms including upconversion, cross-relaxation, non-radiation relaxation, and energy transduction between $$\hbox {Yb}^{3+}$$ and $$\hbox {Er}^{3+}$$ ions, as well as the amplified spontaneous emission along the positive and negative directions of the waveguide. The gain and noise characteristics of the device are analyzed and discussed, and some useful results are obtained in three kinds of pump schemes, i.e. the forward-, backward- and bidirectional pump schemes. Simulation results show that by selecting proper parameter values, the output gain can be achieved over 10.3 dB, and the noise figure can be controlled below 3 dB.

Novel Optical Flat-Gain Hybrid Amplifier for Dense Wavelength Division Multiplexed System

For the first time, a novel flat-gain optical amplifier is proposed using a hybrid configuration with an Er-Yb co-doped waveguide amplifier (EYDWA) and a semiconductor optical amplifier (SOA) for 100 × 10-Gb/s dense wavelength division multiplexed system at 0.2 nm interval. With an EYDWA-SOA hybrid amplifier, a flat gain of is obtained across the effective bandwidth with a gain variation of the order of 0.75 dB without using any gain clamping techniques. It is observed that when the proposed hybrid amplifier is used as a booster for hybrid distributed Raman amplifier and erbium doped fiber amplifier, the gain variation is reduced from 2.01 to ~ 1.15 dB efficiently with acceptable bit error rate.

Method for Accurate Gain Calculation of a Highly ${\rm Yb}^{3+}/{\rm Er}^{3+}$-Codoped Waveguide Amplifier in Migration-Assisted Upconversion Regime

The performance of a highly Yb3+/Er3+-codoped phosphate glass femtosecond-laser written waveguide amplifier is numerically analyzed using a macroscopic rate-equation propagation model where concentration-dependent rates for the interatomic migration-assisted energy-transfer mechanisms are considered. The Er3+-upconversion rate is obtained by a rigorous microscopic statistical modeling of the migration-assisted homogeneous upconversion, and the concentration dependence of the experimental Yb3+-sensitization rate utilized reflects the presence of migration among the Yb3+ ions. The results of the amplifier gain dependence on the dopant concentrations illustrate the influence of migration and the need of a careful modeling of interatomic energy-transfer mechanisms for high-concentration rare-earth-doped fiber or waveguide active devices.

Ion-exchanged Er^3+/Yb^3+ co-doped waveguide amplifiers longitudinally pumped by broad area lasers

A multimode pumping scheme for Er(3+)/Yb(3+) co-doped waveguide amplifiers based on broad area lasers at around 980 nm is presented. The proposed amplifier is fabricated by ion-exchange (IE) technique on silicate and phosphate glasses. The highly efficient energy transfer from Yb(3+) to Er(3+) ions, combined with the use of low cost and high power broad area laser, allows the realization of high performance and cost-effective integrated amplifiers. The structure has been designed and numerically studied using a 3D finite element modelling tool, and over 3 dB/cm small signal gain has been predicted for an optimized amplifier. Preliminary characterization of an amplifier structure provides a first experimental evidence of the novel multimode longitudinal pumping.

Demonstration of Optical Gain at 1550 nm in Erbium–Ytterbium Co-Doped Polymer Waveguide Amplifier

A novel solution-processable erbium-ytterbium co-doped complex was successfully synthesized and used to fabricate a waveguide amplifier. The absorption and photoluminescence spectra of the complex were observed. The full width at half maximum (FWHM) was about 80 nm. An embedded waveguide structure was fabricated using the complex as the core layer and SU-8 material as the cladding layers. With an input signal power of 0.2 mW and pump power of 133.6 mW, an optical gain of 4.14 dB at a wavelength of 1550 nm was obtained in a 29 mm-long waveguide.

Amplifying Characteristics of Er3+/Yb3+ Co-Doped Parallel-Cascaded Double Microring Resonators

In terms of the coupled mode theory, formulas of the transfer function and the output power gain are presented for an Er3+/Yb3+ co-doped parallel-cascaded double microring resonator. Around the pump wavelength of 0.98 μm and the central signal wavelength of 1.55 μm, analysis is performed for the dependence of the output power gain on the pump power, signal power, dopant concentration, amplitude coupling ratio, and ring spacing. The results show that the output power gain of this device is much larger than that of the Er3+/Yb3+ co-doped waveguide amplifier with identical waveguide lengths. In the case of the amplitude coupling ratio κ = 0.064, ring spacing L2 = 10π R, pump power Pp0 = 8 mW, signal power Ps0 = 37.2 μW, Er3+ ion concentration NEr = 1 × 26 m−3, and Yb3+ ion concentration NYb = 3 × 27 m−3, the device can produce higher signal power gain from 11.9 dB even up to 70 dB.

Erbium-ytterbium codoped waveguide amplifier fabricated with solution-processable complex

A solution-processable erbium-ytterbium codoped complex is synthesized. The absorption and photoluminescence spectra of the complex are observed. The full width at half maximum of the emission spectrum is 80 nm around 1530 nm. A structure of embedded waveguide with the complex as core layer is designed. With an input signal power of 0.3 mW, an optical gain of 5.2 dB at a wavelength of 1550 nm is obtained in a 15-mm-long waveguide when the cladding layer is SU-8. When the cladding layer is polymethyl methacrylate, an optical gain of 6.5 dB is obtained in a 12-mm-long waveguide with an input signal power of 1 mW.

Effects of pumped styles on power conversion efficiency and gain characteristics of phosphate glass Er 3+–Yb 3+-co-doped waveguide amplifiers

In order to analyze the power conversion efficiency (PCE) and the gain characteristics of the phosphate glass Er 3+–Yb 3+-co-doped waveguide amplifier (EYCDWA), formulas are derived from the rate equations and the light propagation equations under the uniform dopant and the steady-state conditions. In the derivation of these formulas, we have neglected the amplified spontaneous emission (ASE) and have introduced the initial energy transfer efficiency. By using these formulas, the effects of the pump power, signal power and waveguide length on the PCE and the gain characteristics of the EYCDWA are analyzed, and some useful results are obtained in three kinds of pumped styles, i.e. the forward-, backward- and bidirectional pumped styles.

Theoretical and experimental research on Er-doped and Yb-Er co-doped Al2O3 waveguide amplifiers

The rate equations of Er-doped and Yb-Er co-doped systems pumped at 0.98 mm are presented, with consideration for the upconversion mechanisms such as cooperative upconversion, cross relaxation, and excited state absorption. A multi-theoretical model is founded to analyze the gain characteristics of Er-doped and Yb-Er co-doped Al2O3 waveguide amplifiers by using rate equations, a two-dimension waveguide finite element model and propagation equations with forward and backward amplified spontaneous emission. The dependence of the gain on amplifier length, pump power and doping concentration is obtained. The optimum design curve is given for designing waveguide amplifiers. The new theory is used to analyze the gain performance of a practical Yb-Er co-doped Al2O3 waveguide amplifier, and the analyzed results are in accordance with the experimental data.

Modeling and experiments of packaged Er 3+–Yb 3+ co-doped glass waveguide amplifiers

A full characterization of packaged Er 3+–Yb 3+ co-doped waveguide amplifiers (EYDWAs) fabricated using ion-exchange and field-assisted annealing was reported. The amplifier was modeled using an extended overlapping factors method, and two overlapping factors at the pump and signal wavelengths were introduced to simplify the overlapping integrals between levels’ population densities and mode intensity profiles. The rate equations and the propagation equations depend on one variable: the longitudinal parameter z, and the overlapping integrals have to be carried out once only. The gain and noise characteristics of the EYDWAs were investigated, and there is good agreement between the theoretical and experimental results. With a single 975 nm diode pump of 200 mW power, this packaged ∼4.0 cm long waveguide device delivers a total net gain of ∼12.0 dB peak value at 1.534 μm, and a net gain of ∼8.0 dB and an average noise figure of ∼5.1 dB in the 1530–1560 nm band. The polarization dependent gain of <0.2 dB is also estimated for the device. Comparing to commercially available Er-doped fiber amplifiers, these low cost, high gain pigtailed glass waveguide amplifiers have a great potential to be used in optical access networks.