On-chip optical sensors using ring- and disk-resonators have many potential sensing applications, yet robust and efficient fiber-to-chip coupling and the differing form factor between the two pose deployment challenges. To resolve this, we 3D-printed a ring-resonator onto the tip of a dual-core fiber and demonstrate its use as a remote temperature sensor. The fiber-tip optical circuit is fabricated using direct laser writing (DLW) with two-photon absorption photopolymer material IP-Dip, forming micrometer-scale waveguide cores having a refractive index of 1.53 with a surrounding air cladding. We connect the two-fiber cores by a printed bus-waveguide, utilizing total internal reflection mirrors, allowing light launched into one core to be guided back to the other core. Furthermore, a DLW printed racetrack resonator evanescently coupled to the bus waveguide (Q ∼ 3000) imposes spectral dips on resonance wavelengths. Light sent down into one core is interrogated upon return from the second core, all from the distal end of the sensor. When the sensing end’s temperature is varied, we find a sensitivity of 78 pm/K, due to the polymer’s thermo-optic index variation. The ring-resonator could be functionalized for other sensing applications.

ROADM-on-chip are challenged by waveguide crossings. We present a single multiport AWG demultiplexer that allows wavelength cross-connections without incurring waveguide crossings. The use of thick silicon allows for very low polarization-dependent losses and spectral shifts, in compliance with fiber-communication system requirements.

Abstract Photonic lantern (PL) spatial multiplexers show great promise for a range of applications, such as future high-capacity mode division multiplexing (MDM) optical communication networks and free-space optical communication. They enable efficient conversion between multiple single-mode (SM) sources and a multimode (MM) waveguide of the same dimension. PL multiplexers operate by facilitating adiabatic transitions between the SM arrayed space and the single MM space. However, current fabrication methods are forcing the size of these devices to multi-millimeters, making integration with micro-scale photonic systems quite challenging. The advent of 3D micro and nano printing techniques enables the fabrication of freestanding photonic structures with a high refractive index contrast (photopolymer-air). In this work we present the design, fabrication, and characterization of a 6-mode mixing, 375 µm long PL that enables the conversion between six single-mode inputs and a single six-mode waveguide. The PL was designed using a genetic algorithm based inverse design approach and fabricated directly on a 7-core fiber using a commercial two-photon polymerization-based 3D printer and a photopolymer. Although the waveguides exhibit high index contrast, low insertion loss (−2.6 dB), polarization dependent (−0.2 dB) and mode dependent loss (−4.4 dB) were measured.

The method of spectrophotometry with transmission and reflection spectra recording is used to study the peculiarities of estimating the optical band gap in Ge2Sb2Te5 thin films after annealing at different temperatures, in particular, in the temperature range of the phase transition. A significant influence of the spectrum processing algorithm on the obtained results is found. A comparison of experimental data shows that the sheet reisistance, reflection coefficient, and optical band gap change in different temperature ranges during the crystallization process. In particular, changes in the electrophysical properties continue after the completion of the modification of optical characteristics, which indicates the two-stage nature of the crystallization process in Ge2Sb2Te5 films.

We investigate the taper transition in SiN from strip to subwavelength sampled waveguides and propose an iterative algorithm that converges to optimal transition. The resulting taper length is minimized and its efficiency converges to lossless.

We report initial results of modeling and fabrication of adiabatic mode conversion with subwavelength SiN waveguide sampling for efficient edge fiber coupling. Our calculation show coupling efficiency above 90%.

This paper examines the influence of etching regimes on the reflectance of black silicon formed by Ni-assisted chemical etching. Black silicon exhibits properties of high light absorptance. The measured minimum values of the reflectance (R-min) of black silicon with thickness of 580 nm formed by metal-assisted chemical etching (MACE) for 60 minutes at 460 lx illumination were 2,3% in the UV region (200–400 nm), 0,5% in the visible region (400–750 nm) and 0,3% in the IR region (750–1300 nm). The findings showed that the reflectance of black silicon depends on its thickness, illumination and treatment duration. In addition, the porosity and refractive index were calculated.

Nonuniform thickness of the front transparent conductive oxide (TCO) used for fabrication of thin-film solar module (TFSM) based on micromorphic technology affects P1 laser scribing (P1 scribing on the TCO front layer). A method for improvement of the thickness uniformity of the front TCO using modification of the existing system for gas supply of the LPCVD (TCO1200) vacuum setup with the aid of gasdistributing tubes is proposed. The thickness nonuniformity of the deposition procedure is decreased from 15.2 to 11.4% to improve uniformity of the resistance of the front TCO and light-scattering factor of TFSM. In addition, the number of P1 laser scribes with inadmissible resistance of insulation (less than 2 MΩ) is decreased by a factor of 7. A decrease in the amount of melt at the P1 scribe edges leads to an increase in the TFSM shunting resistance by 56 Ω. The TFSM output power is increased by 0.4 W due to improvement of parameters of the front TCO related to application of gas-distributing tubes.

© Ф.С. Егоров, А.В Кукин, Е.И. Теруков, А.С. Титов 3,4,¶ 1 ООО ” Хевел“, 429952 Новочебоксарск, Россия 2 Чувашский государственный университет им. И.Н. Ульянова, 428000 Чебоксары, Россия 3 ООО ” Научно-технический центр тонкопленочных технологий в энергетике“, 194064 Санкт-Петербург, Россия 4 Физико-технический институт им. А.Ф. Иоффе РАН, 194021 Санкт-Петербург, Россия ¶ e-mail: titovoz@gmail.com

The introduction of nanocrystals plays an important role in improving the stability of the amorphous silicon films and increasing the carrier mobility. Here we report results of the study on the photoluminescence and its dynamics in the films of amorphous hydrogenated silicon containing less than 10% of silicon nanocrystals. The comparing of the obtained experimental results with the calculated probability of the resonant tunneling of the excitons localized in silicon nanocrystals is presented. Thus, it has been estimated that the short lifetime of excitons localized in Si nanocrystal is controlled by the resonant tunneling to the nearest tail state of the amorphous matrix.

The photoinduced degradation of photovoltaic converters based on an a-Si:H/µc-Si:H tandem structure under a standard illuminance of 1000 W/m2 is studied. The spectral and current–voltage characteristics of specially fabricated samples with various degrees of crystallinity of the intrinsic layer in the lower (microcrystalline) cascade are measured in the course of the tests.

Crystallization of thin films of amorphous hydrogenated silicon under the irradiation of femtosecond laser pulses has been studied. It was found that the crystallization has a clearly pronounced threshold nature and depends on the laser emission wavelength. As shown the best results are achieved in crystallization at the laser wavelength range of 740–760 nm.

Big size ( ~1,4 m 2 ) silicon-based thin-film solar module ( SM ) consists of elements connected between each other in such a way as to get maximum efficient solar energy conversion. The technological process of separating single elements in solar modules production is made by laser scribing. As a result, the SM area will consist of «active area», where the photo effect occurs, providing the conversion of the incoming radiation energy, and «dead zone», which does not participate in photo-electric current generation, but is regarded as an element necessary for effective commutation of separate elements. The research includes the analysis of possibility to decrease the «dead zone» and to increase the SM characteristics in terms of the produced electric energy. This can be achieved both by decreasing the width of scribes, and by optimizing the commutative connections of SM elements. The quality and types of scribes in terms of quality and precision depend on laser irradiance parameters used in the technological process of dividing the whole SM area into separate elements.

We have studied structural, electrical and photoluminescence properties of hydrogenated nanocrystalline silicon films with different crystalline volume fractions (from 0-pristine amorphous silicon-to 55%). The crystalline volume fraction and the average diameter of Si nanocrystals were estimated using the position and the intensity of the peaks in Raman spectra of the samples. The photoluminescence spectra exhibit distinct features related to recombination in amorphous silicon (peak energy near 1.35 eV) and in silicon nanocrystals (peak near 1.52 eV). When the crystalline volume fraction approaches 55%, photoluminescence disappears. This was due to the appearance of the percolation path consisting of Si nanocrystals. Photoluminescence spectroscopy was proposed as a non-destructive method for determining of a small volume fraction of Si nanocrystals embedded in amorphous silicon.

The spectral characteristics of the photoresponse of heterostructures with layers of densely packed amorphous silicon nanoparticles produced by laser electrodispersion are studied. The structures exhibit rectifying properties. Annealing in air results in the appearance of silicon oxide nanoparticles in the layers and, in addition, there occurs partial crystallization of the nanoparticles. The spectral characteristics of the photoresponse of the heterostructures have a number of specific features. Compared with standard silicon photodiodes, the sensitivity spectra of the structures under study are shifted to shorter wavelengths, with the shift becoming more pronounced upon annealing. The structures with an annealed layer of nanoparticles exhibit sensitivity in the spectral range 350–600 nm, which exceeds by more than an order of magnitude the sensitivity of unannealed structures. This effect can be attributed to a transistor-like effect in the structure.

After modification of standard "Oerlikon" thin film solar cells producing technology we have managed to fabricate two experimental (10x10 cm(2)) semitransparent solar modules based on amorphous and microcrystalline silicon with efficiency 6.5% and 6.7% and transparency about 20% and 9% in the visible range.

Experimental results on the electron relaxation time and diffusion coefficient in hydrogenated amorphous silicon films that exhibit intrinsic and electronic conductivity at room temperature are reported. It is found that, for these two types of films, the relaxation times are 1 ns and 465 ps and the diffusion coefficients are 0.54 and 0.83 cm2 s−1. It is established that, as the pulse intensity is increased, the decay time of the induced-grating signal shortens.

Surface effects, in particular oxygen passivation, are known to have drastic influence on emission spectra of semiconductor nanoclusters. The goal of this work was to obtain light emission from amorphous silicon nanoclusters by means of oxygen passivation. Granulated films of amorphous silicon nanoclusters were fabricated by the laser electrodispersion technique, which allows obtaining nanoclusters of uniform sizes. Two methods were applied in order to incorporate oxygen into the films, and both result in improvement of the luminescent properties of the films. The role of oxygen passivation as well as the effect of thermal annealing is considered. (C) 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim