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We present a cylindrical rod of single-crystal Nd:YAG fabricated from a bulk crystal using femtosecond laser-induced preferential etching. The rod is pumped at 808 nm, and the laser characteristics at 1064 nm emission and the thermal stability are investigated. The slope efficiency was determined with a maximum optical-to-optical efficiency of 7.9%±0.29% and a FWHM linewidth of 299 ± 63 pm. The etched rod shows parameters consistent with existing Nd:YAG gain crystals. This fabrication technology will find use in composite micro-optical devices where microfluidics, active and passive optics, and structures can be etched out of many different materials and combined into a single device.

We present results from our recent development of a multi-beam Doppler lidar system for accurate 3-dimensional wind measurements. The eye-safe all-fibre system consists of a single seed laser that is amplified in multiple stages and shared between the three emitters. Steps towards wind turbine blade integration will be outlined.

Supercontinuum from 2.5 to 6.5 μm has been generated in ULI waveguides pumped with femtosecond pulses centered at 4.6 μm. Dispersion measurements show the zero dispersion wavelength for the waveguides to be around 5.3 μm.

Ultrafast laser inscription (ULI) allows the fabrication of compact, highly-efficient and robust laser sources over a broad range of crystalline, ceramic and glass gain media. For instance, subsurface waveguides can be formed by the stress induced refractive index modification effect which takes place between two parallel modified regions referred to as “Type II” guiding [1]. Previously, a family of laser hosts known as sesquioxides, namely Lu 2 O 3 , Sc 2 O 3 and LuScO 3 , have been shown to demonstrate efficient, high-power and tunable laser operation around the 2 μm region in both continuous-wave and pulsed regimes when doped with Tm3+ [2, 3]. Combining the Tm3+-doped sesquioxide material properties with the ULI waveguide laser geometry provides a means to produce compact, low-threshold and efficient laser sources near 2 μm with the potential for high pulse repetition rate ultrafast operation. Here we report, to the best of our knowledge, the first demonstration of a ceramic Tm:Lu 2 O 3 waveguide laser source fabricated by ULI.

In this paper we report a two octave spanning supercontinuum generation in a bandwidth of 700–3000 nm in a single-mode photonic crystal fiber made of lead-bismuth-gallate glass. To our knowledge this is the broadest supercontinuum reported in heavy metal oxide glass based fibers. The fiber was fabricated using an in-house synthesized glass with optimized nonlinear, rheological and transmission properties in the range of 500–4800 nm. The photonic cladding consists of 8 rings of air holes. The fiber has a zero dispersion wavelength (ZDW) at 1460 nm. Its dispersion is determined mainly by the first ring of holes in the cladding with a relative hole size of 0.73. Relative hole size of the remaining seven rings is 0.54, which allows single mode performance of the fiber in the infrared range and reduces attenuation of the fundamental mode. The fiber is pumped into anomalous dispersion with 150 fs pulses at 1540 nm. Observed spectrum of 700–3000 nm was generated in 2 cm of fiber with pulse energy below 4 nJ. A flatness of 5 dB was observed in 950–2500 nm range.

The use of confocal Raman microscopy is applied to the study of whey-protein-stabilized oil-in-water emulsions. The stability of emulsions is an important parameter for many applications and is dependent on several factors including protein content and particle size. Emulsions were prepared with varying particle size ranging from 0.8 to 10.0 µm. Changes in sample volume due to laser-induced heating were monitored and correlated to protein content in samples and to particle diameters. It was found that samples with the lowest protein content and larger particle diameters experienced the largest volume changes. The newly developed approach is of a potential predictive use. Copyright © 2013 John Wiley & Sons, Ltd.

In this paper we report on successful supercontinuum generation extending from the near to the mid-infrared region in the range 700–2500 nm in a micro-structured fiber made of lead-bismuth-galate glass and pumped in the femtosecond regime with a wavelength of 1540 nm. The flatness of 5 dB is observed in most of the registered spectrum 1000 – 2500 nm. The improved spectral and thermo-physical properties of this custom made lead-bismuth-galate glass against tellurite and commercially available heavy oxide SF-57 glasses are presented.

We present measurements of the anisotropy of the nonlinear absorption of a silica matrix doped with aligned spheroidal silver nanoparticles, produced by a double ion-implantation process of silver nanoparticles followed by an irradiation with Si ions. The nonlinear response was studied using the z-scan technique with fs pulses at 530 nm, which lies very close to the surface-plasmon absorption peak of the sample. The observed saturable absorption is studied for different angles of the input linear polarization of the pulses, showing a strong anisotropy, which is consistent with the fact that the nanorods are aligned.

Ultrafast Laser Inscription (ULI) of waveguides and Z-scan measurements have been performed in Ge 22 As 20 Se 58 glass (GASIR-1). Light guiding at 2.45 μm and 2.9 μm is shown, demonstrating the potential of GASIR-1 for Mid-IR integrated optics.

A series of xAs40Se60·(100 - x)As40S60 glasses, where x = 0, 25, 33, 50, 67, 75 and 100 mol% As40Se60, has been studied using neutron and X-ray total scattering, Raman spectroscopy and (77)Se MAS-NMR. The results are presented with measurements of non-linear refractive indices, n2, and densities. There is no evidence for the formation of homopolar bonds in these glasses, but neutron correlation functions suggest that there is a non-random distribution of sulfur and selenium atoms in sulfur-rich glasses. The average number of sulfur atoms at a distance of 3-4 Å from a selenium atom, nSeS, deviates from a linear variation with x in glasses containing50 mol% As40Se60; n2 for these glasses also varies non-linearly with x. Importantly, a direct comparison of n2 and nSeS gives a linear correlation, suggesting that n2 may be related to the distribution of chalcogen atoms in the glasses.

We describe the first implementation of narrow-band coherent Rayleigh scattering (CRS) for high spectral resolution of CRS line shapes. Using intensities in the 109 W/cm2 range we find that the measured line shapes of CO2, N2 and Xe gases at room temperature are in good agreement with a CRS model that assumes weakly perturbing fields. We compare our results with broadband CRS and discuss the importance of phase-matching requirements for narrow-band CRS. Finally, we show that a spectral narrowing in the CRS profile is predicted at intensities that are approximately an order of magnitude greater than those used in our experiments. Copyright © 2006 John Wiley & Sons, Ltd.

We present the results of optical-characterization experiments conducted on optically active erbium-doped waveguides. Using selected characterization results presented in this paper and a simple analysis, the device operation is evaluated. Each of the core and the cladding layers were individually fabricated using a single sol-gel deposition. These are, to the best of our knowledge, the first optically active waveguides to be fabricated in such a way. Characterization results include gain, fluorescence-lifetime, waveguide-loss, polarization-dependent-loss (PDL), and erbium-absorption measurements. Relative gains of over 1 dB/spl middot/cm/sup -1/ were measured. Fluorescence lifetimes of the /sup 4/I/sub 13/2/ /spl rarr/ /sup 4/I/sub 15/2/ transition as high as 5.6 ms were observed. Waveguide losses as low as 0.13 dB/spl middot/cm/sup -1/ were measured.

The output characteristics of a dual-channel gain-switched laser system are studied with respect to the gain-switch frequency and power. InGaAsP laser diodes operating at 1548 and 1549 nm are gain-switched at 1 GHz and the spectral and temporal profiles of the pulses are investigated. The development of a pump–probe system with the use of in-line amplifiers and amplified spontaneous emission filtering is detailed.

Tellurite glasses are low phonon energy optical materials suitable for the development of optical devices in the near to mid-IR wavelength region. An additional interesting property is their high nonlinearity, which offers the possibility to fabricate specialty core-clad optical fibres for the development of compact supercontinuum sources characterized by high compactness, stability, and efficiency. We will report the recent progress in the development of a new tellurite glass composition with higher mechanical properties, better transparency in the mid-IR and purity in terms of OH- group content. Its thermal and optical properties, including dispersion in the mid-IR, will be illustrated.

We respond to the comment submitted by Xian Feng on our recent Letter, Opt. Lett.38, 4679 (2013). The comment addressed the attenuation of our oxide tellurite glass labeled TWPN/I/6. We provide the originally measured absorbance spectrum of the glass and correct values of its mid-infrared attenuation.

Tellurite glass photonic crystal fibers (PCF) offer a large potential for broadband supercontinuum generation with bandwidths of 4000 nm demonstrated in suspended-core tellurite PCFs under pumping at 1500-1600 nm. We fabricated a hexagonal-lattice, tellurite PCF with lattice constant Λ = 2 μm, linear filling factor d/Λ=0.75 μm, and a solid core with 2.7 μm diameter. Dispersion, calculated from SEM image of drawn fiber, has ZDW at 1500 nm and 4350 nm with a maximum of 193 ps/nm/km at 2900 nm. Under pumping with 150 fs / 36 nJ / 1580 nm pulses, supercontinuum in a bandwidth from 800 nm to over 2500 nm was measured in a 2 cm long PCF sample. Measured coupling efficiency was 8%. Dispersive and nonlinear length scales are 52 cm and 0.2 mm respectively, yielding nonlinearity-dominant propagation regime in the fiber. Numerical analysis of measured supercontinuum spectrum using NLSE, enabled identification of soliton fission and their subsequent red-shifting, dispersive wave generation across first ZDW, as well as FWM among the red-shifted spectral components. FWM phase-matching condition in the fiber is satisfied in a broad range from 1500 nm to 4000 nm with roughly 900 nm bandwidth around the signal wavelength. Developed model is in good agreement with experimental results. Model is used to estimate supercontinuum bandwidth for other experimental conditions with pump pulse lengths up to 1 ps and PCF lengths up to 10 cm.

High-refractive index chalcogenide and heavy-metal oxide glasses have been developed recently for their application as all-optical switching devices in telecommunication networks. Depending upon the nature of electromagnetic phenomena, the switching speed may vary between milliseconds in a rare-earth doped glass and femtoseconds for surface plasmon relaxation in a nano-scale dispersion of metal particles in glasses.

We demonstrate laser action from a waveguide fabricated in an Er:Yb-doped silicate glass using femtosecond laser inscription. Waveguides were fabricated using a diode-pumped Yb:glass oscillator at a 600-kHz repetition rate. The multiscan technique was used to control the waveguide cross section. Textbook threshold characteristics are observed for both 980 nm and dual-wavelength excitation.

A low insertion loss waveguide is fabricated in z-cut lithium niobate using femtosecond laser waveguide inscription. To fabricate a waveguide exhibiting both low propagation and coupling losses, we used the multiscan fabrication technique to control the size of the waveguide cross section. A minimum insertion loss of only 3.5 dB at 1550 nm was measured for the 18-mm-long waveguide when directly coupled to Corning SMF-28 fibers. Of this 3.5dB, we attribute 2.1 dB to coupling losses, 1.1 dB to propagation losses, and 0.3 dB to Fresnel reflections

A channel waveguide is fabricated inside an erbium-doped oxyfluoride silicate glass sample using femtosecond pulses in the low repetition rate regime. The waveguide cross section is controlled using the multiscan fabrication technique. The 1.85-cm-long waveguide exhibits a total background insertion loss of 4.3 dB when coupled to Corning SMF-28 fibers. Under the maximum available pump power, the device exhibits an internal gain of 1.7 dB at 1537 nm.

We report the fabrication and characterisation of rare-earth-doped multicore optical fiber with the aim to develop multi-band optical fiber laser sources and amplifiers to exploit future novel multicore fiber laser and amplifiers.

Two dimensional interferometric trapping of multiple microspheres and Escherichia coli has been demonstrated using a multicore fiber lensed with an electric arc fusion splicer. Light was coupled evenly into all four cores using a diffractive optical element. The visibility of the fringes and also the appearance of the lattice can be altered by rotating a half wave-plate. As a result the particles can be manipulated from one dimensional trapping to two dimensional trapping or a variety of different two dimensional arrangements. The ability to align bacterial populations has potential application for quorum sensing, floc and biofilm and, metabolic co-operation studies.

A lensed multicore fiber trapping probe has been fabricated using a fusion splicer. One and two dimensional trapping has been demonstrated for particles and Escherichia coli using a DOE or a fully integrated fan-out device.

A negative value for the nonlinear refraction in graphene is experimentally observed and unambiguously verified by performing a theoretical analysis arising from the conductivity of the graphene monolayer. The nonlinear optical properties of multi-layer graphene are experimentally studied by employing the Z-scan technique. The measurements are carried out at 1150, 1550, 1900 and 2400 nm with a 100-femtosecond laser source. Under laser illumination the multi-layer graphene exhibits a transmittance increase due to saturable absorption, followed by optical limiting due to two-photon absorption. The saturation irradiance Isat and the two-photon absorption coefficient β are measured in the operating wavelength range. Furthermore, an irradiance-dependent nonlinear refraction is observed and discriminated from the conventional nonlinear refraction coefficient n2, which is not irradiance dependent. The values obtained for the irradiance-dependent nonlinear refraction are in the order of ∼10−9 cm2W−1, approximately 8 orders of magnitude larger than any bulk dielectrics.

A multicore all-fiber probe is demonstrated that has been fabricated using an electric arc fusion splicer. Interference of the fiber output when coherent light is coupled into two cores is investigated. The properties of the fringes created when the fiber is probing different media were found to be in general agreement with a beam propagation method simulation. Optical manipulation of microspheres near to the end of the probe is examined and the potential for controlled trapping explored. Polymer microspheres with diameters of 2 microns were formed into regular patterns due to the presence of the interference fringes.

Recent results from our work using ultrafast laser writing to fabricate waveguides and on-chip devices inside sulphide chalcogenide glasses are presented in this paper. Low loss single-mode (SM) and multi-mode (MM) waveguide arrays were successfully laser fabricated, for the first time to our knowledge, for operation in the whole near-IR (NIR) to mid- IR (MIR) range (1 to 11 μm wavelengths). These waveguides are demonstrated to have numerical apertures (NA) which can exceed NA=0.2, therefore also allowing for low bend losses as well as direct coupling to QC lasers. We also demonstrate the control over the waveguide mode field diameters (MFDs) (at 1/e2) by changing the waveguide core sizes and index contrasts, achieving typical values of 44 μm at 10.6 μm, down to 6 μm for telecom 1.55 μm light. The optical nonlinear properties of these waveguides have also been preliminarily investigated. Using a femtosecond (fs) optical parametric amplifier system, the optical nonlinearity of bulk gallium lanthanum sulphide (GLS) glass was first measured at 2.5 μm. The upper limits for the nonlinear properties of the laser modified material could be estimated based upon the nonlinear spectral broadening of a 2.5 μm fs pulse train coupled into SM waveguides. Further work includes the demonstration of on-chip three dimensional (3D) beam combiners for the MIR range (10.6 μm in this work), for near future implementation in astronomical observatories for stellar interferometry.

In this paper we report a two octave spanning supercontinuum generation in the range 750-3000 nm with a newly developed photonic crystal fiber. The fibre is fabricated using an in-house synthesized lead-bismuth-galate glass PBG08 with optimised rheological and transmission properties in the range 500-4800 nm. The photonic cladding consists of 8 rings of air holes with a fibre core diameter of 3 μm and a lattice constant of 2.2 μm. The dispersion characteristic is determined mainly by the material dispersion and the first ring of holes in the cladding with a filling factor of 0.68. The filling factor of the remaining 7 rings is 0.45 which allows single mode performance of the fibre in the infrared range. The fibre has a zero dispersion wavelength of 1490 nm which allows the use of 1550 nm wavelength as an efficient pump in the anomalous dispersion regime. The 2 cm long sample of photonic crystal fiber is pumped in the femtosecond regime with a pulse energy of 10 nJ at a wavelength of 1550 nm. A flatness of 5 dB is observed in the spectral range 950-2500 nm.

We have fabricated lensed multi-core fiber using a fusion splicer. The fiber end-shaping was studied and interference between diagonal cores of the four-core singlemode probe was examined for interferometric optical tweezing applications.

A lensed four core fiber has been fabricated using a fusion splicer. The interference in the far field between the cores of the singlemode probe was examined for optical trapping in one and two dimensions.

The refractive index profile, or cross-section, of an optical waveguide is its most defining property. It directly determines the number of transverse modes supported by the waveguide and the properties of these modes. Proper control of the waveguide cross-section is therefore essential if the performance of the waveguide, or waveguide device, is to be optimised. This chapter describes how the waveguide cross-section affects the properties of the guided modes, why it is important to control the waveguide cross-section from a device engineering point of view and the various experimental techniques that have been developed to control the cross-section of ultrafast laser inscribed waveguides.

We report observation of four- and five-photon absorption in the chalcogenide glasses at the telecommunication wavelengths. The nonlinear refractive index is sufficiently large that the optical switching criterion is satisfied.

We report the successful fabrication of a low-loss near-IR waveguide in polycrystalline ZnSe using ultrafast laser inscription. The waveguide, which was inscribed using the multiscan fabrication technique, supported a well-confined mode at 1.55 μm. Propagation losses were characterized at 1.55 μm using the Fabry-Perot technique and found to be 1.07 dB · cm(-1) ± 0.03 dB · cm(-1).

We describe the fabrication of optical waveguides in polycrystalline ZnSe using ultrafast laser inscription. The optimum waveguide, characterized at 800 nm, exhibited a propagation loss of 0.5 dB·cm−1.

We have fabricated three Tm3+ and Yb3+ co-doped air-clad fibres with varying Yb:Tm ratio. We have studied the 2 µm lasing in a simple cavity and have shown improved performance for increased Yb:Tm ratio.

Spectral broadening spanning 850 nm (−15 dB points) was observed in an ultrafast laser inscribed gallium lanthanum sulphide waveguide under excitation of femto-second laser radiation with a central wavelength of 2.35 µm.

We have shown a novel technique for producing composite materials containing deformed metallic nanoparticles that are placed at random but aligned in a given direction. This is achieved by a double ion-implantation technique; the first implantation produces the nanoparticles, while the second elongates them in a given direction. The resulting composite material has polarization dependent absorption spectra, due to a split of the surface plasmon resonance into two bands. Because of the alignment of the particles in a preferential direction, the material also presents strong birefringence, which has been characterized by a relatively simple ellipsometric technique. We have also studied the nonlinear optical properties of these highly anisotropic nanocomposites in the femtosecond and picosecond regimes. In the femtosecond regime we find a mainly absorptive nonlinearity for wavelengths close to the surface plasmon resonance for polarization parallel to the long axis of the nanoparticles. The nonlinearity, studied using the z-scan technique, was found to consist of saturable absorption which was also polarization dependent, and this dependence was fitted reasonably well by a simple two-level model for anisotropic particles. In the picosecond regime, the resonant nonlinear response was studied using the selfdiffraction and ‘P-scan’ techniques. In this case the anisotropy of the nonlinear response was used to determine the different tensorial elements of (3)ijkl, and to resolve the absorptive and refractive contributions to the nonlinearity. For these experiments, although significant nonlinear absorption was observed, the nonlinear response was shown to be dominated by nonlinear refraction, which was attributed to strong intra- and inter-band transitions induced by the resonant radiation. The capability of tailoring their linear and nonlinear optical properties by the precise control of particle size, density, shape, and alignment, achievable with the implantation technique shown, makes these aligned nanostructured materials very interesting for applications in

Strain and thermal sensitivities of germanate and tellurite glass fibres were measured using a fibre Fabry-Perot (FFP) interferometer and fibre Bragg gratings (FBG). The strain phase sensitivity for germanate and tellurite fibre were 5900×103 rad/m and 5600×103 rad/m respectively at a central wavelength of 1540nm using FFP interferometer, which is consistent with the value of 1.22pm/µepsilon obtained for a germanate fibre FBG. The Young's modulus for germanate and tellurite fibre were also measured to be 58GPa and 37GPa. The thermal responses of germanate fibre were examined as 24.71 and 16.80 pm/°C at 1540nm and 1033nm wavelength using the FBG.

We present the first report on experimental observation of nonlinear spectral broadening in an all-solid photonic band gap Bragg fiber of relatively large mode area approximately 62 microm(2). The theoretically designed Bragg fiber for this specific application was fabricated by the well known MCVD technique. Nonlinear spectral broadening was observed by launching high power femtosecond pulses of 1067 nm pump wavelength. These first results indicate that fabrication of such Bragg fibers, once perfected, should potentially serve as an alternative route for realization of supercontinuum light.

The authors report supercontinuum generation in an ultrafast laser inscribed chalcogenide glass waveguide. The waveguides were fabricated using a Yb:glass cavity-dumped femtosecond oscillator with 600- kHz repetition rate. The waveguides were pumped using an optical parametric amplifier tuned to 1500 nm with a bandwidth of 100 nm. The broadest resulting supercontinuum spanned 600 nm (at -15 dB points) from 1320 to 1920 nm. The supercontinuum was generated in the normal dispersion regime, enhancing stability, and exhibits a smooth spectral shape.

A three-core tellurite glass fiber having different combinations of rare earth oxide dopants in each core has been fabricated using shaped die-extrusion. Three cores, doped with Ho(3+)-Tm(3+)-Yb(3+), Er(3+)-Ce(3+), and Tm(3+)-Yb(3+) respectively, exhibited visible upconversion (blue, green and red) and infrared emissions at 1.4 microm, 1.5 microm, 1.9 microm and 2.05 microm when pumped at a wavelength of 980 nm. The prospects for multi-band amplifiers and lasers are discussed.

The temperature coefficients of optical phase have been measured at 1536 nm wavelength for short fiber Fabry-Perot cavities of tellurite and germanate glass fibers spliced to silica fiber. The results are consistent with the thermal expansion and thermo-optic coefficients of the bulk glasses.

We report on the application of coherent Rayleigh scattering (CRS) to the measurement of temperature in a flame using narrow bandwidth pump and probe fields. High resolution measurements of the line shape were used to derive flame temperature based on fits to the line shape. An uncertainty in the temperature of 3% was determined utilizing a CRS model that includes scattering from a multicomponent gas for the first time. This model was validated at room temperature for a mixture of atomic and molecular species.

The invited paper explains the transmission properties of a range of near-, mid-, and far-IR optical fibres for their applications in chemical and biological sensing. Methods for the fabrication of single and multiple-core mid-IR fibres are discussed in view of controlling the thermal and viscosity properties for fibre drawing. In particular, the need for removing impurity bands in the 5000 to 1000 cm-1 range is explained. The importance of engineering multi-core fibres is also discussed for simultaneous measurements of Raman, IR and surface plasmon enhanced modes together with say, temperature using a mid-IR transmitting tellurite fibre e.g. in a chemical process. The paper explains the principles and advantages of evanescent wave coupling of light at the resonant frequency bands for chemical sensing using a fibre evanescent wave spectroscopic sensor having a GeTeSe chalcogenide fibre. Using fibre based techniques, measurements for Cr6+ ions in solution and As3+ and As5+ in solids have been characterized at visible and mid-IR regions, respectively. In this paper we also explain the importance of using mid-IR fibres for engineering novel laser and broadband sources for chemical sensing.

We report recent developments on rare-earth ion doped heavy metal-oxide glass fibres for engineering lasers and amplifiers, operating in the optical communication window. Special emphasis on rare-earth ion co-doping schemes for controlling the pump excited state absorption process, which is dominant in the single mode fibre geometry, is explained by demonstrating enhanced gain, specially in the 1520 to 1610 nm band, using a 22 cm long Er3+-Ce3+ doped tellurite fibre. Our investigation also demonstrates how a triple core fibre structure with Tm3+-Yb3+, Er3+-Ce3+, and Tm3+-Ho3+-Yb3+ co-doping can be excited with a high-power 980 nm source through cladding pump scheme to generate ASE in the 1500-2050 nm region.

A three dimensional fan-out device has been fabricated using ultrafast laser inscription. The device allows each core of a multicore fibre to be addressed individually by a single mode fiber held in an FVA.

Ultrafast laser inscription has been used to inscribe an optical waveguide in ErYb-doped glass. We demonstrate that the irradiation does not degrade the 4I13/2 lifetime of Er-ions embedded in the modified material.