Highly stable graphene-assisted tunable dual-wavelength erbium-doped fiber laser

A highly stable tunable dual-wavelength fiber laser (TDWFL) using graphene as a means to generate a highly stable output is proposed and generated. The TDWFL comprises a 1 m long, highly doped erbiumdoped fiber (EDF) acting as the linear gain medium, with a 24-channel arrayed waveguide grating acting as a wavelength slicer as well as a tuning mechanism to generate different wavelength pairs. The tuned wavelength pairs can range from 0.8 to 18.2 nm. A few layers of graphene are incorporated into the laser cavity to induce the four-wave-mixing effect, which stabilizes the dual-wavelength output by suppressing the mode competition that arises as a result of homogenous broadening in the EDF. © 2013 Optical Society of Americ

Ultraviolet generation in step index optical fibres and microfibres

Coherent ultraviolet (UV) generation has various applications in a large number of fields, such as stand-off explosive detection, enhanced Raman scattering and photolithography, to name a few. Typically, the generation of coherent UV light relied on frequency doubling with nonlinear crystals and relatively complicated free space optics, on toxic gases (excimers) and low power UV diodes. In this thesis, the use of solid core step-index optical fibre for the generation of coherent UV radiation is investigated. Here, wavelength conversion in optical microfibres (OMFs) via nonlinear processes is considered. Firstly, efficient generation of UV radiation via intermodal third harmonic generation (THG) in fibres is first studied. While THG is potentially efficient in OMFs, it is not feasible in optical fibres with large numerical apertures. Detuning is found to be a critical parameter which determines the overall efficiency, thereby making the OMF diameter control crucial. Initial experiments indicate that the quasi-continuous wave (CW) sources with long pulses (a few ns) and high peak powers (∼ kW) are the most suitable for intermodal THG in OMFs, as detrimental nonlinear effects become dominant with ultrashort pulses. However, further theoretical investigations show that intermodal THG is fundamentally limited by the intrinsic surface roughness of the silica OMFs, restricting the maximum efficiency to ∼ 10-3. This leads to the investigation of four wave mixing (FWM), where both parametric amplification and wavelength generation are theoretically investigated. A quasi-CW source working in conjunction with a periodically poled silica fibre (PPSF) is employed to investigate this experimentally, and it is shown that a scheme employing two OMFs allowed the generation of coherent UV radiation down to 0:31 µm, with fundamental limitations being imposed from losses due to the oxygen-deficiency centre inherent to the fibre

Tuning the near-infrared absorption of aromatic amines on tapered fibers sculptured with gold nanoparticles

We discover an unexpected enhancement of the absorption of near-infrared light by aromatic amine overtones on photonic microfibers sculptured with gold nanoparticles. The adsorbed nanoparticles make the near-infrared spectroscopy of aromatic amines on microfibers feasible despite the small absorption cross-section of the molecular vibration overtones. We demonstrate that in the presence of gold nanomediators, the absorption of light by weak overtone transitions in N-methylaniline as a model analyte is dramatically enhanced. We attribute this effect to the increase of the mean trajectory of light in a microfiber due to its resonant scattering on metallic nanoparticles. The spectrally integrated transmittance scales with the concentration of nanoparticles to the power 1/6 - the phenomenon of diffusive propagation of light. Practical applications of the discovered effect will include the detection of aromatic amines for efficient treatment of metabolic disorders resulting from the amino acids deficiency, research in biomedicine, and a number of bedside applications.</p

Tuning the near-infrared absorption of aromatic amines on tapered fibers sculptured with gold nanoparticles

We discover an unexpected enhancement of the absorption of near-infrared light by aromatic amine overtones on photonic microfibers sculptured with gold nanoparticles. The adsorbed nanoparticles make the near-infrared spectroscopy of aromatic amines on microfibers feasible despite the small absorption cross-section of the molecular vibration overtones. We demonstrate that in the presence of gold nanomediators, the absorption of light by weak overtone transitions in N-methylaniline as a model analyte is dramatically enhanced. We attribute this effect to the increase of the mean trajectory of light in a microfiber due to its resonant scattering on metallic nanoparticles. The spectrally integrated transmittance scales with the concentration of nanoparticles to the power 1/6 - the phenomenon of diffusive propagation of light. Practical applications of the discovered effect will include the detection of aromatic amines for efficient treatment of metabolic disorders resulting from the amino acids deficiency, research in biomedicine, and a number of bedside applications.</p

Dataset for Harmonic Generation via chi(3) Intermodal Phase Matching in Microfibers

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Embedded AlN/GaN multi-layer for enhanced crystal quality and surface morphology of semi-polar (11-22) GaN on m-plane sapphire

We demonstrate high quality semi-polar (11-22) gallium nitride thin film grown on m-plane sapphire substrate with the insertion of AlN/GaN multi-layer via MOCVD. The influence of three different number of multi-layers AlN/GaN pairs on the crystal quality and surface morphology of semi-polar (11-22) gallium nitride thin film is investigated. The surface morphology analysis strongly suggests that increasing the number of AlN/GaN pairs from 20 to 60 suppresses the arrowhead-like and undulated features. The increase of AlN/GaN pairs also enhanced the surface quality, with the root mean square roughness improving from 16.24 nm to 6.08 nm. The abruptness of the interface between the AlN/GaN pairs was seen to improve significantly upon reaching the 40th pair where a continuous thin layer was clearly observed for each pair. The crystal quality was also observed to be enhanced at higher number of AlN/GaN pairs, where the on- and off-axis X-ray rocking curve showed significant reduction in the full width at half maximum of at least ~10% and 20%. Finally, x-ray reciprocal space mapping analysis further confirms the enhancement of the crystal quality as the diffuse scattering streak was suppressed, which may indicate a significant reduction of the defect density

PMMA Microfiber And Microball Resonator For Fomaldehyde Liquid Sensing

This experiment reports the fabrication of the Polymethyl Methaclyrate (PMMA) Microball Resonator (MBlR) as a liquid sensor tested on various level of concentration of the Formaldedhye liquid. The PMMA MBlR is fabricated via the “dipped and twirl” method to create the sphere-shaped ball with diameter Db = 320um. The MBlR is then optically excited using a 9 μm PMMA microfiber and was found to have a Q Factor of >104. The MBlR was then employed as a liquid sensor with the level percentage range between 0%–4% of Formaldehyde liquid and the performance is compared with a non MBlR microfiber. The MBlR sensor was found to have a sensitivity of 6.94 dB m/%, linearity >90 % and P-value of more than 105. The PMMA MBlR liquid sensor was also found to have a good repeatability and stability over a period of 60 s

Nanosecond pulse generation with a gallium nitride saturable absorber

A mode-locked nanosecond Erbium-doped fiber laser (EDFL) was demonstrated using gallium nitrate (GaN) in the form of a polished crystal as a saturable absorber (SA). The GaN film exhibited a modulation depth of 2% with a saturable optical intensity of 0.46 MW/cm2. The laser directly produced nanosecond pulses with stable mode-locking operation at a pump threshold of 149.51 mW. The generated output pulses operated at a 1562 nm central wavelength with a pulse duration and a repetition rate of 485 ns and 967 kHz, respectively. The average output power was 3.068 mW at a pump power of 182.34 mW, corresponding to 3.1 nJ single pulse energy. These results indicate that GaN material has a promising application in ultrafast light generation. © 2018 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

Effect of size on single and double optical microbottle resonator humidity sensors

An experimental study on the effect of whispering gallery mode (WGMs) on micro-bottle resonator (MBR) and its application on humidity sensing is presented. Different transmission mode spectra observed when the diameter of MBR (Db) change from 130μm to 190μm. The Q-factor for single and double MBRs ware observed >104 for all cases. The size and number of MBRs effecting Q-factor value which are high Q-factor value for smallest size Db=130μm for single MBR and Pair-4 (combination of two biggest MBRs Db=190μm) for double MBRs. Application of single and double MBRs in humidity sensing received various sensing performance. With the highest sensitivity value, linearity >90% and P-value >10-13 make MBR with diameter 130μm to be the best performance as humidity sensor for all cases. Both single and double MBRs are stable over 60 seconds. Overall, the size of the MBR has been shown to be more important than the quantity of MBRs for humidity sensing. Indeed, double MBRs actually perform worse than single MBRs as humidity sensors

Dataset for All-fiber fourth and fifth harmonic generation from a single source

Raw data for figures in Abdul Khudus, Muhammad, Lee, Timothy, De Lucia, Francesco, Corbari, Constantino, Sazio, Pier-John, Horak, Peter and Brambilla, Gilberto (2016) All-fiber fourth and fifth harmonic generation from a single source. Optics Express, 24, (19), 21777-21793. (doi:10.1364/OE.24.021777)</span