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1.
Eur J Paediatr Dent ; 16(2): 159-62, 2015 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-26147825

RESUMO

AIM: To examine the nature of dental anxiety in paediatric patients, and to identify factors relevant to paediatric dental anxiety in a sample of 5 to 17 year-old children residing in Cairns, Australia. MATERIALS AND METHODS: A convenient sample of 125 children, their parents and corresponding student practitioners were selected. Each was assessed with questionnaires. RESULTS: A higher level of dental anxiety was seen in children who were subject to radiographic examination as part of their treatment (b=0.462; p=0.012). Similarly, children of Asian ethnicity showed higher dental anxiety levels than their Caucasian counterparts (b=1.187; p=0.010). Finally, the childrens' overall dental anxiety levels decreased after being treated by student practitioners (t=2.311;df=124; p=0.022). CONCLUSION: Children experienced greater anxiety before receiving dental treatment than after. Treatment involving radiographic examination exacerbated dental anxiety and children of Asian descent were more anxious prior to receiving treatment. Further investigation is indicated.


Assuntos
Ansiedade ao Tratamento Odontológico/psicologia , Adolescente , Criança , Comportamento Infantil , Pré-Escolar , Clínicas Odontológicas , Feminino , Humanos , Masculino , Relações Profissional-Paciente , Queensland/etnologia , Radiografia Interproximal/psicologia , Radiografia Panorâmica/psicologia , Estudantes de Odontologia , /psicologia
2.
Opt Lett ; 40(11): 2529-32, 2015 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-26030549

RESUMO

We report a high-power synchronously pumped femtosecond Raman fiber laser operating in the normal dispersion regime. The Raman laser is pumped by a picosecond Yb(3+)-doped fiber laser. It produces highly chirped pulses with energy up to 18 nJ, average power of 0.76 W and 88% efficiency. The pulse duration is measured to be 147 fs after external compression. We observed two different regimes of operation of the laser: coherent and noise-like regime. Both regimes were experimentally characterized. Numerical simulations are in a good agreement with experimental results.

3.
Opt Lett ; 40(9): 2033-6, 2015 May 01.
Artigo em Inglês | MEDLINE | ID: mdl-25927777

RESUMO

We present the design and operation of an all-fiber, synchronously pumped, bidirectional optical parametric oscillator (OPO) for precision sensing applications. The fiber-based OPO (FOPO) generates two frequency combs with identical repetition rates but different carrier offset frequencies. A narrow beatnote was observed with full-width at half-maximum (FWHM) linewidth of <10 Hz when the two frequency combs were overlapped on a photodetector. The all-fiber design removes the need for free-space alignment and adjustment. In addition, an external delay line to overlap the two pulse trains in time on the detector is not needed since our unique design provides automatic delay compensation. We expect the novel FOPO to find important applications in precision measurements including rotation sensing with ultra-large sensing area and sensitivity.

4.
Opt Express ; 22(13): 15992-9, 2014 Jun 30.
Artigo em Inglês | MEDLINE | ID: mdl-24977855

RESUMO

Diatoms are a renewable (biologically reproducible) source of three-dimensional (3-D) nanostructured silica that could be attractive for a variety of photonic devices, owing to the wide range of quasi-periodic patterns of nano-to-microscale pores available on the silica microshells (frustules) of various diatom species. We have investigated the optical behavior of the silica frustule of a centric marine diatom, Coscinodiscus wailesii, using a coherent broadband (400-1700 nm) supercontinuum laser focused to a fine (20 µm diameter) spot. The C. wailesii frustule valve, which possessed a quasi-periodic hexagonal pore array, exhibited position-dependent optical diffraction. Changes in such diffraction behavior across the frustule were consistent with observed variations in the quasi-periodic pore pattern.


Assuntos
Diatomáceas , Luz , Nanoestruturas , Dióxido de Silício/análise , Animais
5.
Biomed Opt Express ; 4(10): 2187-95, 2013.
Artigo em Inglês | MEDLINE | ID: mdl-24156074

RESUMO

We demonstrate label-free multi-photon imaging of biological samples using a compact Er(3+)-doped femtosecond fiber laser mode-locked by a single-walled carbon nanotube (CNT). These compact and low cost lasers have been developed by various groups but they have not been exploited for multiphoton microscopy. Here, it is shown that various multiphoton imaging modalities (e.g. second harmonic generation (SHG), third harmonic generation (THG), two-photon excitation fluorescence (TPEF), and three-photon excitation fluorescence (3PEF)) can be effectively performed on various biological samples using a compact handheld CNT mode-locked femtosecond fiber laser operating in the telecommunication window near 1560nm. We also show for the first time that chlorophyll fluorescence in plant leaves and diatoms can be observed using 1560nm laser excitation via three-photon absorption.

6.
Opt Lett ; 38(18): 3616-9, 2013 Sep 15.
Artigo em Inglês | MEDLINE | ID: mdl-24104828

RESUMO

We propose and demonstrate a synchronously pumped fiber optical parametric oscillator (FOPO) operating in the normal dispersion regime. The FOPO generates chirped pulses at the output, allowing significant pulse energy scaling potential without pulse breaking. The output average power of the FOPO at 1600 nm was ∼60 mW (corresponding to 1.45 nJ pulse energy and ∼55% slope power conversion efficiency). The output pulses directly from the FOPO were highly chirped (∼3 ps duration), and they could be compressed outside of the cavity to 180 fs by using a standard optical fiber compressor. Detailed numerical simulation was also performed to understand the pulse evolution dynamics around the laser cavity. We believe that the proposed design concept is useful for scaling up the pulse energy in the FOPO using different pumping wavelengths.

7.
Opt Express ; 21(7): 8821-30, 2013 Apr 08.
Artigo em Inglês | MEDLINE | ID: mdl-23571972

RESUMO

We demonstrate a fiber-based slow light system using a carbon disulfide (CS2)) filled integrated liquid-core optical fiber (i-LCOF). Using 1 meter of i-LCOF we were able to delay 18ps pulses up to 34ps; a delay of 188% of the pulse width. This experimental setup serves as a foundation for slow-light experiments in other nonlinear liquids. Numerical simulations of pulse-propagation equations confirmed the observed delay and a simplified method is presented that can be applied to calculate induced delay for non-cw Stokes pulses. The system is all-fiber and compact with delays greater than a pulse width, indicating potential application as an ultrafast controllable delay line for time division multiplexing in multiGb/s telecommunication systems.


Assuntos
Dissulfeto de Carbono/química , Tecnologia de Fibra Óptica/instrumentação , Análise Espectral Raman/instrumentação , Desenho de Equipamento , Análise de Falha de Equipamento , Luz , Espalhamento de Radiação , Integração de Sistemas
8.
Opt Lett ; 38(4): 543-5, 2013 Feb 15.
Artigo em Inglês | MEDLINE | ID: mdl-23455130

RESUMO

We report Brillouin lasing in an integrated liquid-core optical fiber filled with neat CS2. This is the first observation of Brillouin lasing in an optical fiber filled with a liquid, to the best of our knowledge. The linewidth of the single frequency liquid-based Brillouin laser was estimated to be <1 kHz by beating two similar but independent lasers against one another.

9.
Opt Express ; 20(7): 8148-54, 2012 Mar 26.
Artigo em Inglês | MEDLINE | ID: mdl-22453484

RESUMO

We have developed a novel integrated platform for liquid photonics based on liquid core optical fiber (LCOF). The platform is created by fusion splicing liquid core optical fiber to standard single-mode optical fiber making it fully integrated and practical - a major challenge that has greatly hindered progress in liquid-photonic applications. As an example, we report here the realization of ultralow threshold Raman generation using an integrated CS2 filled LCOF pumped with sub-nanosecond pulses at 532 nm and 1064 nm. The measured energy threshold for the Stokes generation is 1nJ, about three orders of magnitude lower than previously reported values in the literature for hydrogen gas, a popular Raman medium. The integrated LCOF platform opens up new possibilities for ultralow power nonlinear optics such as efficient white light generation for displays, mid-IR generation, slow light generation, parametric amplification, all-optical switching and wavelength conversion using liquids that have orders of magnitude larger optical nonlinearities compared with silica glass.


Assuntos
Cristais Líquidos/química , Fibras Ópticas , Desenho de Equipamento , Análise de Falha de Equipamento , Fótons , Integração de Sistemas
10.
Opt Lett ; 37(5): 942-4, 2012 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-22378446

RESUMO

We report on a new platform for all-optical switching based on inverse Raman scattering in liquids. Narrowband switching, which could be suitable for wavelength-division-multiplexed applications, is demonstrated using integrated liquid-core optical fiber infiltrated with both neat liquids (CCl(4) and CS(2)) as well as an organic chromophore (ß-carotene) dissolved in CCl(4). Compared to standard glass optical fibers, these liquids have much larger Raman loss coefficients, which help reduce the pump power by at least an order of magnitude. Further improvements can be expected with the development of highly soluble organic compounds possessing large Raman cross sections.

11.
Opt Express ; 19(12): 11365-74, 2011 Jun 06.
Artigo em Inglês | MEDLINE | ID: mdl-21716366

RESUMO

Micron-sized white light propagation invariant beams generated by a simple and compact fiber device are presented. The all-fiber device is fabricated by splicing a short piece of large-core multimode fiber onto a small-core single mode white light delivery fiber. Because this fiber device offers an inherent spatial coherence, nondiffracting white light beams can be created with a temporally incoherent broadband light source (a halogen bulb) and, most importantly, the surrounding fringes don't fade as the bandwidth of the light source increases because the underlying physics of this fiber device is different from that of the axicon. White light Bessel-like beams have been generated from multimode fibers with core diameters of 50 µm, 105 µm, and 200 µm. The distance of nondiffracting propagation of the white light Bessel beam increases with increasing core size of the multimode fiber. Propagation characteristics of red, green, and blue individual beams are also presented.

12.
Opt Express ; 19(13): 12532-9, 2011 Jun 20.
Artigo em Inglês | MEDLINE | ID: mdl-21716494

RESUMO

We report the observation of Zeno switching through an inverse Raman scattering (IRS) process in an optical fiber. In IRS, light at the anti-Stokes frequency is strongly attenuated in the presence of a pump field, allowing it to be used for all-optical switching and modulation. Our observed level of induced absorption via IRS in the optical fiber is > 20 dB in a time scale of less than 5 ps. The full Raman response spectrum was extracted experimentally and excellent agreement was found between the experimental data and theoretical modeling of IRS.


Assuntos
Lasers , Fibras Ópticas , Análise Espectral Raman/instrumentação , Análise Espectral Raman/métodos , Desenho de Equipamento , Germânio/química , Modelos Teóricos , Processamento de Sinais Assistido por Computador/instrumentação , Dióxido de Silício/química , Telecomunicações/instrumentação
13.
Opt Express ; 19(6): 5313-8, 2011 Mar 14.
Artigo em Inglês | MEDLINE | ID: mdl-21445169

RESUMO

We report on a low noise all-fiber erbium fs frequency comb based on a simple and robust tapered-fiber carbon nanotube (tf-CNT) design. We mitigate dominant noise sources to show that the free-running linewidth of the carrier-envelope offset frequency (fceo) can be comparable to the best reported performance to date for fiber-based frequency combs. A free-running fceo linewidth of ~20 kHz is demonstrated, corresponding to an improvement of ~30 times over previous work based on a CNT mode-locked fiber laser [Opt. Express 18, 1667 (2010)]. We also demonstrate the use of an acousto-optic modulator external to the laser cavity to stabilize fceo, enabling a 300 kHz feedback control bandwidth. The offset frequency is phase-locked with an in-loop integrated phase noise of ~0.8 rad from 10Hz to 400kHz. We show a resolution-limited linewidth of ~1 Hz, demonstrating over 90% of the carrier power within the coherent fceo signal. The results demonstrate that the relatively simple tf-CNT fiber laser design can provide a compact, robust and high-performance fs frequency comb.

14.
Opt Express ; 18(20): 20558-64, 2010 Sep 27.
Artigo em Inglês | MEDLINE | ID: mdl-20940950

RESUMO

We investigate high-Q, small mode volume photonic crystal nanobeam cavities using a curved, tapered optical microfiber loop. The strength of the coupling between the cavity and the microfiber loop is shown to depend on the contact position on the nanobeam, angle between the nanobeam and the microfiber, and polarization of the light in the fiber. The results are compared to a resonant scattering measurement.

15.
Opt Express ; 18(20): 21350-5, 2010 Sep 27.
Artigo em Inglês | MEDLINE | ID: mdl-20941031

RESUMO

We report the design and performance of a high power femtosecond laser source near 1 micron wavelength which is generated from an octave-spanning supercontinuum (SC) pumped by an Er-doped mode-locked laser. The laser system delivers >5W average power at 35MHz repetition rate and 135 fs pulse duration.

16.
Opt Lett ; 34(5): 593-5, 2009 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-19252562

RESUMO

We report a mode-locked fiber laser that exploits dissipative-soliton pulse shaping along with cladding pumping for high average power. The laser generates 31 nJ chirped pulses at 70 MHz repetition rate, for an average power of 2.2 W. After dechirping outside the laser, 80 fs pulses, with 200 kW peak power, are obtained.


Assuntos
Lasers , Desenho de Equipamento , Fibras Ópticas
17.
IEEE Photonics Technol Lett ; 21(3): 128-130, 2009 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-21731403

RESUMO

We report stabilization of a thulium-holmium codoped fiber soliton laser with a saturable absorber based on carbon nanotubes. The laser generates transform-limited 750-fs pulses with 0.5-nJ energy.

18.
J Microsc ; 232(1): 44-55, 2008 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-19017200

RESUMO

This paper deals with the characterization of layered structures sampled with respect to a reference surface. A scheme where thick slabs are sampled perpendicular to a curved surface is considered, resulting in a non-uniform sampling of the structure. We present an estimation procedure based on the Horvitz-Thompson principle. An approximation of the sampling probability is proposed, which depends on the local surface curvatures, on the slab dimensions and on the intensity function of slab anchors. The practical determination of local parameters is detailed for the case of a revolution surface. The procedure is applied to the estimation of surface area density of cell walls in tomato pericarp.


Assuntos
Parede Celular/ultraestrutura , Microscopia Confocal/métodos , /ultraestrutura , Processamento de Imagem Assistida por Computador
19.
Opt Express ; 16(15): 11453-8, 2008 Jul 21.
Artigo em Inglês | MEDLINE | ID: mdl-18648465

RESUMO

Spectral filtering of a chirped pulse can be a strong pulse-shaping mechanism in all-normal-dispersion femtosecond fiber lasers. We report an implementation of such a laser that employs only fiber-format components. The Yb-doped fiber laser includes a fiber filter, and a saturable absorber based on carbon nanotubes. The laser generates 1.5-ps, 3-nJ pulses that can be dechirped to 250 fs duration outside the cavity.


Assuntos
Desenho Assistido por Computador , Tecnologia de Fibra Óptica/instrumentação , Lasers , Modelos Teóricos , Nanotubos de Carbono/química , Simulação por Computador , Desenho de Equipamento , Análise de Falha de Equipamento , Luz , Nanotubos de Carbono/ultraestrutura , Espalhamento de Radiação
20.
J Microsc ; 193(Pt 3): 199-211, 1999 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-10348656

RESUMO

In the present paper, we summarize and further develop recent reseach in the estimation of the variance of sterelogical estimators based on systematic sampling. In particular, it is emphasized that the relevant estimation procedure depends on the sampling density. The validity of the variance estimation is examined in a collection of data sets, obtained by systematic sampling. Practical recommendations are also provided in a separate section.


Assuntos
Microscopia/métodos , Análise de Variância , Matemática , Amostragem
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