Erbium-doped Waveguide Research Articles

On-Chip Electro-Optic Modulator With Loss Compensation Based on Polymeric Active-Integrated Waveguides

In this paper, an on-chip electro-optic (EO) modulator with loss compensation based on polymeric active-integrated waveguides was demonstrated. An erbium-doped waveguide amplifier was investigated and integrated with the EO modulator to compensate for signal loss. Polymeric active-integrated waveguides were based on the Mach-Zehnder interferometer structure, which consists of an amplified waveguide formed by two symmetric Y-junction branches and an EO waveguide formed by two decoupled waveguide arms. The dimensions of the polymeric active-integrated waveguides and the modulator were carefully designed and simulated. Moreover, a six-level spectroscopic model pumped at 980 nm was presented. The rate equations and propagation equations were solved, and the gain characteristics were simulated. The internal gain of 4.65 dB was achieved when the signal power was 0.1 mW at 1550 nm, the pump power was 100 mW at 980 nm, the Er 3+ concentration was $9.3\times 10^{25}/\text{m}^{3}$ , and the Yb 3+ concentration was $8.6\times 10^{26}/\text{m}^{3}$ in one Y-junction branch with a length of 1.5 cm. With the integrated waveguide amplifier, the loss of the EO modulator can be compensated at 9.3 dB in the two symmetric Y-junction branches. The light output intensity was also statistically presented. The proposed device with active-integrated waveguides could be used in polymer-based photonics integrated circuits.

Storage and Reemission of Heralded Telecommunication-Wavelength Photons Using a Crystal Waveguide

Large-scale quantum networks will employ telecommunication-wavelength photons to exchange quantum information between remote measurement, storage, and processing nodes via fibre-optic channels. Quantum memories compatible with telecommunication-wavelength photons are a key element towards building such a quantum network. Here, we demonstrate the storage and retrieval of heralded 1532 nm-wavelength photons using a solid-state waveguide quantum memory. The heralded photons are derived from a photon-pair source that is based on parametric down-conversion, and our quantum memory is based on a 6 GHz-bandwidth atomic frequency comb prepared using an inhomogeneously broadened absorption line of a cryogenically-cooled erbium-doped lithium niobate waveguide. Using persistent spectral hole burning under varying magnetic fields, we determine that the memory is enabled by population transfer into niobium and lithium nuclear spin levels. Despite limited storage time and efficiency, our demonstration represents an important step towards quantum networks that operate in the telecommunication band and the development of on-chip quantum technology using industry-standard crystals.

Fs-laser-written erbium-doped double tungstate waveguide laser.

We report on the first erbium (Er3+) doped double tungstate waveguide laser. As a gain material, we studied a monoclinic Er3+:KLu(WO4)2 crystal. A depressed-index buried channel waveguide formed by a 60 µm-diameter circular cladding was fabricated by 3D femtosecond direct laser writing. The waveguide was characterized by confocal laser microscopy, µ-Raman and µ-luminescence mapping, confirming that the crystallinity of the core is preserved. The waveguide laser, diode pumped at 981 nm, generated 8.9 mW at 1533.6 nm with a slope efficiency of 20.9% in the continuous-wave regime. The laser polarization was linear (E || Nm). The laser threshold was at 93 mW of absorbed pump power.

Modal properties of an Erbium-doped asymmetric single-mode slab waveguide in the glass-ceramics SnO2-SiO2 system

We investigate the modal properties (effective index and modal gain) of an active, Erbium-doped single-mode slab waveguide made of silica tin-dioxide glass-ceramics on Silica. Completed with a photo-inscribed Bragg grating, such a structure is a good candidate for realizing an optically pumped laser emitter. For total Erbium concentration of 9.84 × 10−4 mol/cm3 and a cross-section (for stimulated transitions) of σ ≈ 2 × 10−25 m2 in a discussed structure, the maximum achievable material gain in DFB with Quarter-Wave phase Shift (QWS-DFB) is σ Ntot ≈ 23 m−1. Taking into account the confinement factor, the maximum achievable modal gain, in complex amplitude, over the length of 10 mm is at about (αmaxL) ≈ 0.09.

High optical gain in erbium-doped potassium double tungstate channel waveguide amplifiers.

We report on the optical-gain properties of channel waveguides patterned into lattice-matched KGdxLuyEr1-x-y(WO4)2 layers grown onto undoped KY(WO4)2 substrates by liquid phase epitaxy. A systematic investigation of gain is performed for five different Er3+ concentrations in the range of 0.75 to 10at.% and different pump powers and signal wavelengths. In pump-probe-beam experiments, relative internal gain, i.e., signal enhancement minus absorption loss of light propagating in the channel waveguide, is experimentally demonstrated, with a maximum value of 12 ± 5 dB/cm for signals at the peak-emission wavelength of 1534.7 nm.

Efficient ridge waveguide amplifiers and lasers in Er-doped lithium niobate by optical grade dicing and three-side Er and Ti in-diffusion

Highly efficient erbium-doped titanium in-diffused ridge waveguide optical amplifiers and lasers in x-cut congruent LiNbO3 pumped at 1486 nm have been developed. A total internal gain of 14 dB has been achieved in 4.6 cm-long waveguides for a coupled pump power of 200 mW. We demonstrated a laser operating at 1561 nm with a slope efficiency of 33% exceeding the best literature values for Er:Ti:LiNbO3 waveguide lasers. To improve the amplifier/laser performance, our novel fabrication technique of three-side Er and Ti in-diffusion into pre-defined ridges was used.

Er:Ti:LiNbO3 ridge waveguide optical amplifiers by optical grade dicing and three-side Er and Ti in-diffusion

Erbium-doped titanium in-diffused ridge waveguide optical amplifiers in x-cut congruent LiNbO3 substrates pumped by a 1486 nm laser diode are reported for the first time. High internal gain of 2.7 dB/cm has been demonstrated in 2.5 cm long waveguides for the coupled pump power 200 mW exceeding the best literature values reported for Er:Ti:LiNbO3 channel waveguides. For gain improvement, we have developed a novel technique which is comprised of ridge definition using diamond blade dicing followed by three-side erbium (Er) and titanium (Ti) layer deposition and high-temperature diffusion. Thereby both higher Er concentrations with more symmetric diffusion profiles and lower scattering losses due to the high-temperature smoothened waveguide side walls have been obtained.

Resonant pumped erbium-doped waveguide lasers using distributed Bragg reflector cavities.

This Letter reports on an optical pumping scheme, termed resonant pumping, for an erbium-doped distributed feedback (DFB) waveguide laser. The scheme uses two mirrors on either side of the DFB laser, forming a pump cavity that recirculates the unabsorbed pump light. Symmetric distributed Bragg reflectors are used as the mirrors and are designed by matching the external and internal quality factors of the cavity. Experimental demonstration shows lasing at an optical communication wavelength of around 1560 nm and an improvement of 1.8 times in the lasing efficiency, when the DFB laser is pumped on-resonance.

Preparation and Characterization of Thermally Stable Silicon-Containing Fluoropolymer Matrix for Application to Erbium-Doped Waveguide Amplifiers

This study focuses on the fabrication of fluoropolymer films as erbium(Er3+) host material with a goal of achieving sufficient thermal stability, optical clarity in the optical communication region and a chemical resistance to withstand typical fabrication processing and operation conditions. To satisfy the demands mentioned above, acrylo-polyhedral oligomeric silsesquioxane as heat-resistance improver, 2,2,3,3,4,4,5,5-octafluoropentyl acrylate as fluorinated acrylic monomer, tetrahydrofurfuryl acrylate as solubility enhancer, 3-(trimethoxysilyl)propyl methacrylate as both a silane coupling agent and another heat-resistance improver and Darocur 4265 as photoinitiator were used. Various compositions were evaluated to obtain high quantity of Er3+ ions in the polymer matrix, high thermal stability and high transparency.

Erbium-doped slot waveguides containing size-controlled silicon nanocrystals

Silicon based slot waveguides with a slot containing Si nanocrystals (Si-nc) and Erbium ions (Er3+) inside a silica matrix were prepared using sputter deposition and low-energy ion implantation. This sequence enabled independent optimization of nanocrystal formation and Er3+ incorporation parameters. Using a superlattice approach, the size of the Si-nc inside the slot could be controlled and optimized for maximum Er3+ luminescence yield at 1.54 μm. Er3+ is found to be efficiently pumped by Si-nc of sizes around 3 to 4 nm. Increasing Er3+ photoluminescence at 1.54 μm with increasing post-implantation annealing temperatures up to 1000 °C is attributed to annealing of matrix or Si-nc interface defects mainly. Additionally, a dependence of the Er3+ luminescence intensity on both the excitation and emission linear polarization orientation is shown, which demonstrates efficient field enhancement in sputtered slot waveguide structures.

Internal gain in Er-doped As₂S₃ chalcogenide planar waveguides.

Low-loss erbium-doped As₂S₃ planar waveguides are fabricated by cothermal evaporation and plasma etching. Internal gain in the telecommunications band is demonstrated for the first time in any chalcogenide glass and additionally in a thin film planar waveguide amplifier configuration.

Hybrid erbium-doped DFB waveguide laser made by wafer bonding of two ion-exchanged glasses

Er-doped and Er/Yb-codoped glasses have a key role in the production of lasers and amplifiers for optical communication systems and eye-safe sensors operating at wavelengths around 1550nm. Ion-exchanged waveguides on Er/Yb-codoped phosphate glass allow implementing quite compact and efficient active devices. Unfortunately, these wafers are not compatible with the integration of passive functions since unpumped erbium ions absorb 1550nm signal. Hence, an efficient monolithic co-integration of passive and active optical functions requires hybridizing doped and undoped glasses. In this paper, we present the realization of a fully encapsulated three-dimensional distributed feedback (DFB) hybrid laser obtained by the wafer bonding of two ion-exchanged substrates. On the first one, an undoped silicate glass, a selectively buried channel core waveguide is made by a Ag+/Na+ exchange and a field-assisted burial. A Bragg grating is then etched on the wafer surface. On the second wafer, an Er/Yb-codoped phosphate glass, a slab core waveguide is obtained by a Ag+/Na+ exchange. The two wafers are finally bonded together yielding to a DFB laser: the interaction between the guided light and the doped glass provides the amplification, while the Bragg grating supplies the feedback. With this fully encapsulated device, (420±15)µW laser emission has been observed at 1534nm for (390±20)mW injected pump power, while its input and output are totally insulated from the doped wafer.

硫系掺铒光波导在光通信的研究进展

硫系掺铒光波导在光通信的研究进展

Potential for large optical gain improvement of erbium-doped slot waveguide amplifiers in silicon photonics

The potential for on-chip optical amplification at λs=1530 nm in silicon photonics using erbium-doped rich polymers integrated in silicon-slot waveguides is investigated by using a four-level spectroscopic model and a pumping wavelength of 1.48 μm. It is shown that the key parameter driving the whole amplification efficiency is the slot waveguide linear loss level, while optimization of the hollow core waveguide cross section leads to a slot width around 130 nm. Our investigations show that an on-chip optical gain of about 10 dB can be obtained with 7 dB/cm loss slot waveguides. Such a propagation loss is directly sustained by experimental results obtained for photonic structures fabricated using silicon technology. Due to the likelihood of improved technological processes in the near future, the slot waveguide loss level was swept in the 3–10 dB/cm range, showing that on-chip optical gain up to 30 dB can be seriously envisaged for slot waveguides with optimized optical losses around 3 dB/cm.

Excitation cross section of erbium-doped GaN waveguides under 980 nm optical pumping

Excitation cross section of erbium-doped GaN waveguides is measured to be approximately 2.2×10−21cm2 at 980 nm pumping wavelength. This cross section value is found relatively insensitive to the crystalline quality of epilayers. However, spontaneous emission carrier lifetimes in these waveguides are directly related to both the crystalline quality and the optical loss, and thus can be used as a material quality indicator.

Highly fluorinated erbium(III) complexes for emission in the C-band

Two highly fluorinated Er3+ complexes with three 6,6,7,7,8,8,8-heptafluoro-2,2-dimethyl-3,5-octanedionate (fod) groups and either bipyridine (bipy) or bathophenantholine (bath) as the ancillary ligand emitting at the C-band (third communication window for fiber transmission) are presented. These complexes are the result of a design process aimed at decreasing the vibrational quenching from high frequency oscillators. The structure of [Er(fod)3(bipy)] has been elucidated by single-crystal X-ray diffraction, while Sparkle/PM6 and Sparkle/PM7 semi-empirical calculations have been used to model the ground state geometry for [Er(fod)3(bath)]. Photoluminescence studies confirm sensitization of the Er3+ ions by antenna effect, leading to NIR emission at 1.53 μm. This energy transfer proves to be more efficient for [Er(fod)3(bath)] as a result of the bulkier and more rigid structure of bath diimide. The good thermal stability of the materials up to over 200 °C allows envisaging their use in erbium-doped waveguides, NIR-OLEDs or other optoelectronic devices.

Erbium-doped waveguide DBR and DFB laser arrays integrated within an ultra-low-loss Si_3N_4 platform

Record low optical threshold power and high slope efficiency are reported for arrays of distributed Bragg reflector lasers integrated within an ultra-low-loss Si(3)N(4) planar waveguide platform. Additionally, arrays of distributed feedback laser designs are presented that show improvements in pump-to-signal conversion efficiency of over two orders of magnitude beyond that found in previously published devices. Lithographically defined sidewall gratings provide the required lasing feedback for both cavity configurations. Lasing emission is shown over a wide wavelength range (1534 to 1570 nm), with output powers up to 2.1 mW and side mode suppression ratios in excess of 50 dB.

Refractive index change of multicomponent glass films for bismuthate erbium-doped waveguide amplifiers prepared by radio-frequency magnetron sputtering under different magnetic fields of cathode

Bismuthate erbium (Er)-doped waveguide amplifiers consist of an Er-doped core surrounded by an Er-free cladding film with lower refractive index. The propagation loss of a waveguide critically depends on both the thickness and the refractive index of its core and cladding films; hence, these two properties of such films must be controlled. We studied the influence of magnetic fields on a batch-to-batch variation of the refractive index of Er-free multicomponent cladding glass films deposited by radio-frequency magnetron sputtering. We successfully controlled the variation in the refractive indices of the films to within 0.001 throughout the lifetime of the target by applying the design techniques of a weak magnetic field and flat magnetic field lines to a magnetic array for sputtering. We also found that the self-bias voltage maintained a high value irrespective of target consumption. This phenomenon is thought to be related to stabilization of the deposition rate and the refractive index of the films under the experimental sputtering conditions.

Correlation between the optical loss and crystalline quality in erbium-doped GaN optical waveguides

Erbium-doped GaN (GaN:Er) epilayers were synthesized by metal organic chemical vapor deposition. GaN:Er waveguides were fabricated based on four different GaN:Er layer structures: GaN:Er/GaN/Al2O3, GaN:Er/GaN/AlN/Al2O3, GaN:Er/GaN/Al(0.75)Ga(0.25)N/AlN/Al2O3, and GaN/GaN:Er/GaN/Al2O3. Optical loss at 1.54 μm in these waveguide structures has been measured. It was found that the optical attenuation coefficient of the GaN:Er waveguide increases almost linearly with the GaN (002) x-ray rocking curve linewidth. The lowest measured loss was ~6 dB/cm.

Dual-Core Leaky Waveguide-Based Filters for Erbium-Doped Waveguide Amplifier

This article gives the design of a gain-flattening filter for an erbium-doped waveguide amplifier using a dual-core resonant leaky waveguide. The spectral variation of leakage loss of the waveguide has been used for gain equalization of the erbium-doped waveguide amplifier in the conventional (C) band. Leakage loss of the structure has been calculated by using the transfer matrix method. Numerical simulation results show a 17.5-dB gain with a gain excursion of ±1.35 dB in the C-band (1,526 nm–1,566 nm) of a typical erbium-doped waveguide amplifier. The study should be useful in designing integrated optic gain-flattening filters.