Sonia M. García-Blanco

Giant Optical Gain in a Rare‐Earth‐Ion‐Doped Microstructure

Modal gain per unit length versus launched pump power is predicted and measured in a 47.5 at.% Yb(3+) -doped potassium double tungstate channel waveguide. The highest measured gain exceeds values previously reported for rare-earth-ion-doped materials by two orders of magnitude.

Thulium channel waveguide laser in a monoclinic double tungstate with 70% slope efficiency

Laser experiments were performed on buried, ridge-type channel waveguides in an 8 at. % thulium-doped, yttrium-gadolinium-lutetium codoped monoclinic double tungstate. A maximum slope efficiency of 70% and output powers up to 300 mW about 2.0 μm were obtained in a mirrorless laser resonator, by pumping with a Ti:sapphire laser near 800 nm. To the best of our knowledge, this result represents the most efficient 2 μm channel waveguide laser to date. Lasing is obtained at various wavelengths between 1810 nm and 2037 nm.

Loss compensation in long-range dielectric-loaded surface plasmon-polariton waveguides

Loss compensation in long-range dielectric-loaded surface plasmon-polariton waveguides is theoretically analyzed when rare-earth-doped double tungstate crystalline material is used as the gain medium in three different waveguide configurations. We study the effect of waveguide geometry on loss compensation at the telecom wavelength of 1.55 μm, and demonstrate that a material gain as small as 12.5 dB/cm is sufficient for lossless propagation of plasmonic modes with sub-micron lateral confinement when using waveguide ridges with gain.

Erbium-doped spiral amplifiers with 20 dB of net gain on silicon

Spiral-waveguide amplifiers in erbium-doped aluminum oxide on a silicon wafer are fabricated and characterized. Spirals of several lengths and four different erbium concentrations are studied experimentally and theoretically. A maximum internal net gain of 20 dB in the small-signal-gain regime is measured at the peak emission wavelength of 1532 nm for two sample configurations with waveguide lengths of 12.9 cm and 24.4 cm and concentrations of 1.92 × 10(20) cm(-3) and 0.95 × 10(20) cm(-3), respectively. The noise figures of these samples are reported. Gain saturation as a result of increasing signal power and the temperature dependence of gain are studied.

Low-loss sharp bends in polymer waveguides enabled by the introduction of a thin metal layer

Embodying a thin metallic layer underneath the core of a sharply bent polymer waveguide is shown in this work to considerably reduce the total losses of both the quasi-transverse-electric and quasi-transverse-magnetic modes. The computational results show a total loss as low as ~0.02 dB/90° for the quasi-transverse-electric mode for radii between 6 and 13 µm at the wavelength of 1.55 µm, which corresponds to a 10-fold improvement over the purely dielectric counterpart. The radii range exhibiting such low total loss can be tuned by properly selecting the parameters of the structure. For the quasi-transverse-magnetic mode, the metal layer reduces the total losses modestly for radii ranging from 3 to 10 µm. Simulation results for different structural parameters are presented.

Design, manufacturing, and qualification of an uncooled microbolometer focal plane array–based radiometric package for space applications

Uncooled microbolometer detectors are well suited for space applications due to their low power consumption while still exhibiting adequate performance. Furthermore, the spectral range of their response could be tuned from the mid- to the far-infrared to meet different mission requirements. If radiometric measurements are required, the radiometric error induced by variation of the temperature of the detector environment must be minimized. In a radiometric package, the detector environment is thermally stabilized by means of a temperature-controlled radiation shield. The radiation shield must be designed to prevent stray radiation from reaching the detector. A radiometric packaging technology for uncooled microbolometer FPAs is presented. The selection of materials is discussed and the final choices presented based on thermal simulations and experimental data. The radiometric stability with respect to stray light and variation of the temperature of the environment as well as the different noise components studied by means of the Allan variance are presented. It is also shown that the device successfully passed the prescribed environmental tests without degradation of performance.

Loss compensation in metal-loaded hybrid plasmonic waveguides using Yb 3+ potassium double tungstate gain materials

The compensation of propagation losses of plasmonic nanowaveguides will constitute an important milestone towards the widespread use of these structures as enabling components for highly dense, fast, on-chip nanophotonic circuitry. Rare-earth doped double tungstate gain materials can not only provide elevated modal gain per unit length, but are capable of the amplification of very high rate signals, making them excellent potential candidates for such application. In this paper, a model that permits simulating plasmonic structures in rare-earth doped potassium double tungstates is described. The model is applied to study the achievable net gain in metal-loaded hybrid plasmonic waveguides with different structural parameters.

Low-Loss Highly Tolerant Flip-Chip Couplers for Hybrid Integration of Si 3 N 4 and Polymer Waveguides

In this letter, low-loss and highly fabrication-tolerant flip-chip bonded vertical couplers under single-mode condition are demonstrated for the integration of a polymer waveguide chip onto the Si₃N₄/SiO₂ passive platform. The passively aligned vertical couplers have a lateral misalignment between polymer and Si₃N₄ waveguide cores of ±1.25 μm. Low-loss operation has been experimentally demonstrated over a wide spectral window of 1480-1560 nm, with measured coupler losses below 0.8 dB for Si₃N₄ taper angles below 1.2°, in good agreement with the calculated values. Furthermore, thermal shock test results show less than 0.1 dB degradation, indicating a robust coupling performance.

Low-loss sharp bends in low contrast polymer hybrid metallic waveguides

Surface plasmons polaritons have drawn significant attention in recent years not only thanks to their capability of confining the field in the dielectric/metal interface, but also thanks to their potential to produce highly efficient thermooptical or electro-optical devices such as modulators and switches due to the presence of the metal layer amidst the electromagnetic field. However, the high confinement comes at the cost of high propagation losses due to the metal’s highly absorptive nature at visible and near-IR wavelengths. In order for plasmonic devices to find a widespread use in integrated optics, an advantage over dielectric waveguides needs to be found that justifies their utilization. In this work, we present an application in which metallic waveguides perform better than their dielectric counterparts. By adding a thin metallic layer underneath the waveguide core, the total bend losses (dB/90° are reduced with respect to the bend losses of the equivalent dielectric structure without the metallic layer for a range of radii from 35 µm down to 1 µm. The results show a dramatic reduction of total bend losses in TE-polarization with values as low as 0.02 dB/90° bend for radii between 6 and 13 µm. The mechanism for the reduction of bend losses is the shielding action of the metal layer, which prevents the field to leak into the substrate. In this paper, both detailed theoretical calculations as well as experimental results for SU-8 channel waveguides will be presented.

Erbium-doped spiral amplifiers with 20 dB gain on a silicon chip

We report the fabrication and optical characterization of long, spiral-shaped erbium-doped aluminum oxide (Al2O3:Er3+) channel waveguides for achieving high overall signal amplification on a small footprint. Al2O3:Er3+ films with Er3+ concentrations in the range between 0.44−3.1×1020 cm-3 were deposited by reactive co-sputtering onto standard, thermally oxidized silicon substrates. Spiral-shaped waveguides were designed and structured into the films by chlorinebased reactive ion etching. In the current design, each spiral waveguide occupies an area of 1 cm2. Typical background propagation losses near 1500 nm are (0.2±0.1) dB/cm. A commercially available, pigtailed diode laser at 976 nm was employed as the pump source. The erbium-doped waveguide amplifiers were characterized in the small-signal-gain regime at the peak-gain wavelength (λ = 1532 nm) of Al2O3:Er3+. A maximum of 20 dB of internal net gain was measured for a 24.5-cm-long spiral waveguide with an Er3+ concentration of 0.95×1020 cm-3. Similar results were obtained for a shorter spiral with an Er3+ concentration about twice as high. Samples with lower concentration exhibited lower gain because of insufficient pump absorption, while samples with higher concentration showed less gain because of migration-accelerated energy transfer up-conversion and, more importantly, a fast quenching process.