Er3+ doped Silica-on-Silicon using fs-laser doping process for Integrated Waveguide Amplifier Platforms

Rare earth doped waveguide amplifier (EDWA) on silica-on-silicon (SOS) platform are area of great interest for silicon integrated photonics. We report the fabrication of erbium doped silica-on-silicon (SOS) wafer-scale platforms for integrated waveguide amplifier and laser application. We used a method named- ultrafast laser plasma doping (ULPD) process on silica- on-silicon substrates using erbium doped zinc-sodium tellurite glasses (TZN) as targets. The influence of laser energy on the doping process was studied in terms of the refractive index of the waveguides formed and their photoluminescence properties. Planar slab waveguides of refractive index1.64 at 633 nm and characteristic photoluminescence lifetimes of erbium at 1535 nm wavelength emission, varying from 13.38 ms to 10.52 ms were obtained. We used higher repetition rate (10 kHz) amplified Ti-Sapphire laser with pulse duration of 45 fs for faster and efficient growth of active waveguide layer in this research

Phase changeable vanadium dioxide (VO₂) thin films grown from vanadium pentoxide (V₂O₅) using femtosecond pulsed laser deposition

There are significant challenges accompanied by fabricating a pure crystalline VO₂ (M1) thin film with an abrupt metal to insulator phase change properties. Most fabrication methods yield an amorphous VO₂ thin film that requires a post-annealing process to be converted into crystalline VO₂ (M1). Hence, the thickness of VO₂ (M1) films produced is very limited. In this work, we report the growth of pure VO₂ (M1) crystalline thin films onto a sapphire substrate in an oxygen atmosphere by the femtosecond pulsed laser deposition technique and using vanadium pentoxide (V₂O₅) as an ablation target. The thin films were deposited at substrate temperatures of 25 °C, 400 °C, and 600 °C, which reveal the crystallized structures of VO₂ (M1) without post-annealing. The thin film deposited at a substrate temperature of 600 °C exhibits a sharp and an abrupt metal-to-insulator transition (MIT) at a temperature of 66.0 ± 2.5 °C with nearly four orders of magnitude of the resistivity change (3.5 decades) and a narrow MIT hysteresis width of 3.9 °C. Furthermore, the influence of the substrate temperature, nanoparticle or grain size, and film thickness on the MIT parameters such as sharpness of the transition temperature, hysteresis width, and amplitude are discussed for potential applications of tunable antennas, terahertz planar antennas, and RF-microwave switches

Femtosecond Laser Deposition of Germanium Selenide onto Silicon Platform at Different Substrate Temperatures

Germanium selenide (GeSe) thin films were fabricated by employing femtosecond pulsed-laser deposition (fs-PLD) on silicon (100) substrates at various substrate temperatures, ranging from 25 °C to 600 °C. The thin films’ surface morphology qualities and optical properties were studied by utilising transmission electron microscopy (TEM) and X-ray diffraction (XRD). The X-ray diffraction result signifies that the thin films deposited on the silicon at a substrate temperature below 400 °C were amorphous Ge-Se. In contrast, those grown at 400 °C and above exhibited crystallised peaks of Ge-Se orthorhombic and tetragonal structures. The deposition growth rate of the thin films was also found to decrease substantially with increasing substrate temperature. These results show that the fs-PLD process has great potential for fabricating good quality Ge-Se thin film. This technique could enable the manufacture of modern optoelectronic devices for applications in optical communication, sensing, and ovonic threshold switching for the high-density crossbar memory array

Erbium-doped polymer waveguide amplifiers for PCB-integrated optical links

Optical technologies are increasingly considered for use in high-performance electronic systems to overcome the performance bottleneck of electrical interconnects when operating at high frequencies and provide high-speed communication between electronic chips and modules. Polymer waveguides are leading candidates for implementing board-level optical interconnections as they exhibit favourable mechanical, thermal and optical properties for direct integration onto conventional printed circuit boards (PCBs). Numerous system demonstrators have been reported in recent years featuring different types of polymer materials and opto-electronic (OE) PCB designs. However, all demonstrated polymer-based interconnection technologies are currently passive, which limits the length of the on-board links and the number of components that can be connected in optical bus architectures. In this paper therefore, we present work towards the formation of low-cost optical waveguide amplifiers that can be readily integrated onto standard PCBs by combining two promising optical technologies: siloxane-based polymers and ultra-fast laser plasma implantation (ULPI). Siloxane-based waveguides exhibit high-temperature resistance in excess of 300°C and low loss at different wavelength ranges, while ULPI has been demonstrated to produce very high dopant concentrations in glass thin films with values of 1.63×1021 cm-3 recently reported in Er-doped silica layers. Here we present detailed simulation studies that demonstrate the potential to achieve a internal gain of up to 8 dB/cm from such structures and report on initial experimental work on Er-doped films and waveguides demonstrating photoluminescence and good lifetimes

Phase evolution, morphological, optical and electrical properties of femtosecond pulsed laser deposited TiO₂ thin films

In this paper, we report anatase and rutile titanium oxide (TiO2) nanoparticulate thin films fabricated on silica and Indium Tin Oxide (ITO) substrates using femtosecond pulsed laser deposition (fs-PLD). Depositions were carried-out at substrate temperatures of 25 °C, 400 °C and 600 °C from anatase and rutile phase target materials. Effect of substrate temperature on the surface morphology, microstructural, optical, and electrical properties of these films were systematically investigated by using various range of measurements such as scanning electron microscopy, (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Raman spectroscopy, Ultraviolet–visible-near infrared (UV–Vis–NIR) spectroscopy, and Hall Effect measurements. It is observed that the TiO2 thin films surface are predominated with nanoparticulates of diameter less 35 nm, which constitute about ~ 70%; while the optical bandgaps and electrical resistivity decrease with increasing substrate temperature. A mixed-phase (anatase/rutile) TiO2 thin film was produced at a substrate temperature of 400 °C when samples are fabricated with anatase and rutile target materials. The results of this study indicate that the structural and crystallinity, optical, and electrical properties can be controlled by varying fs-PLD process parameters to prepare TiO2 thin films, which are suitable for applications in photovoltaics, solar cells, and photo-catalysis

Examination of Combustion-Generated Smoke Particles from Biomass at Source: Relation to Atmospheric Light Absorption

The formation of carbonaceous aerosols from biomass combustion is associated with a high degree of uncertainty in global climate models. In this work, soot samples were generated from the combustion of pine wood, wheat straw and barley straw in a fixed bed stove; as well as from the combustion of biomass pyrolysis model compounds. Samples were collected on filters, which were used for the determination of Absorption Angstrom Exponent (AAE). In addition, the content and composition of elemental carbon (EC) and organic carbon (OC) were determined, and the interrelationships between these and the AAE were examined. It was found that the spectroscopic signature of samples with high ‘brown carbon’ emissions was comparable to that of many PAH and polyphenols, with AAE ranging from 1.0–1.2 for model compounds to 0.5–5.7 for biomass. In addition to the filter samples, particles were collected directly onto microscopy grids and analysed by transmission electron microscopy–electron energy loss spectroscopy (TEM-EELS) in order to determine structural characteristics. This was used to examine the impact of combustion conditions and flue gas dilution on particle structure. Smouldering phase and diluted particles were found to be less graphitic and twice as oxygenated as undiluted flaming phase particles. The results are interpreted to better understand the impact of combustion processes on soot formation from biomass combustion. Abbreviations: AAE: absorption angstrom exponent; ATN: light attenuation; AToFMS: aerosol time of flight mass spectrometer; BC: black carbon; BrC: brown carbon; C:O: carbon to oxygen ratio; CPD: cyclopentadienyl radical C5H5; DMS: differential mobility spectrometer; EC: elemental carbon; EELS: electron energy loss spectroscopy; HACA: hydrogen abstraction carbon addition; MCE: modified combustion efficiency; OA: organic aerosols; OC: organic carbon; PM: particulate matter; POM: primary (particulate)organic matter; Py-GC/MS: pyrolysis gas chromatography/mass spectrometry; sp2: amount of sp2 orbital hybridisation in atomic structure; SSA: single scattering albedo; TC: total carbon (BC+OC) or (EC+OC); TEM: transmission electron microscope; TGA: thermogravimetric analysis

Erbium-doped polymer waveguide amplifiers for board-level optical interconnects

Optical interconnects have an important role to play in next-generation high-performance electronic systems by enabling power-efficient high-speed board-level communication links. Polymer-based optical waveguides is a leading technology for integrating optical links onto standard printed circuit boards as it is sufficiently low cost and enables cost-effective manufacturing and assembly. Various polymer-based optical backplanes have been reported in recent years enabling different on-board interconnection architectures. However, all currently demonstrated systems are purely passive, which limits therefore the reach, complexity and functionality of these on-board systems. Here, we present recent simulation and experimental studies towards the development of Er-doped polymer-based waveguide amplifiers. Two different approaches to integrate Er-doped materials in siloxane polymer are investigated: (i) ultrafast laser plasma implantation of Er-doped glasses and (ii) solution-based dispersion of Er-doped nanoparticles. Experimental and simulation results on the achievable performance from such waveguide amplifiers are presented focusing on impact of the waveguide loss and upconversion on the gain figure.The authors would like to acknowledge Dow Corning for the provision of the polymer samples and the UK EPSRC for supporting this work through the Seamatics research grant (EP/M015165/1) and IPES CDT (EP/L015455/1)

Tm³⁺ Tellurite-Modified-Silica Glass Thin Films Fabricated Using Ultrafast Laser Plasma Doping

Thin glass films have been produced by implanting Tm³⁺ doped and Tm³⁺/Er³⁺ codoped tellurite glasses into silica substrates using ultrafast laser plasma doping for the first time. The resulting glass films had thicknesses of up to 2 µm, refractive indices of 1.5 – 1.65 and exhibited photoluminscence in the 1.5 – 2.1 µm wavelength region when excited with 808 nm and 976 nm laser diodes. The OH⁻ content of the silica glass substrate was also found to have an effect on the Tm³⁺: ³F₄ photoluminescence lifetime in the modified thin glass film layer, with the high OH⁻ containing substrate exhibiting a shorter lifetime. Through optimisation of the femtosecond laser ablation parameters, we have produced crack-free thin films of Tm³⁺ doped tellurite-modified silica glass layers with good thickness uniformities of ±10 nm, and the refractive index of the modified layer is up to 13% higher than the bare substrate material

Chemical and explosive detection with long-wave infrared laser induced breakdown spectroscopy

Conventional laser induced breakdown spectroscopy (LIBS) mostly uses silicon-based detectors and measures the atomic emission in the UV-Vis-NIR (UVN) region of the spectrum. It can be used to detect the elements in the sample under test, such as the presence of lead in the solder for electronics during RoHS compliance verification. This wavelength region, however, does not provide sufficient information on the bonding between the elements, because the molecular vibration modes emit at longer wavelength region. Measuring long-wave infrared spectrum (LWIR) in a LIBS setup can instead reveal molecular composition of the sample, which is the information sought in applications including chemical and explosive detection and identification. This paper will present the work and results from the collaboration of several institutions to develop the methods of LWIR LIBS for chemical/explosive/pharmaceutical material detection/identification, such as DMMP and RDX, as fast as using a single excitation laser pulse. In our latest LIBS setup, both UVN and LWIR spectra can be collected at the same time, allowing more accurate detection and identification of materials