Tunable SNAP microresonators via internal ohmic heating.

We demonstrate a thermally tunable surface nanoscale axial photonics (SNAP) platform. Stable tuning is achieved by heating a SNAP structure fabricated on the surface of a silica capillary with a metal wire positioned inside. Heating a SNAP microresonator with a uniform wire introduces uniform variation of its effective radius which results in constant shift of its resonance wavelengths.

Polarization maintaining single-mode low-loss hollow-core fibres.

Hollow-core fibre (HCF) is a powerful technology platform offering breakthrough performance improvements in sensing, communications, higher-power pulse delivery and other applications. Free from the usual constraints on what materials can guide light, it promises qualitatively new and ideal operating regimes: precision signals transmitted free of nonlinearities, sensors that guide light directly in the samples they are meant to probe and so on. However, these fibres have not been widely adopted, largely because uncontrolled coupling between transverse and polarization modes overshadows their benefits.

Higher-order mode fiber enables high energy chirped-pulse amplification.

Energy scaling of femtosecond fiber lasers has been constrained by nonlinear impairments and optical fiber damage. Reducing the optical irradiance inside the fiber by increasing mode size lowers these effects. Using an erbium-doped higher-order mode fiber with 6000 µm(2) effective area and output fundamental mode re-conversion, we show a breakthrough in pulse energy from a monolithic fiber chirped pulse amplification system using higher-order mode propagation generating 300 µJ pulses with duration <500 fs (FWHM) and peak power >600 MW at 1.

Low-loss hollow-core fibers with improved single-modedness.

Hollow-core fibers (HCFs) are a revolution in light guidance with enormous potential. They promise lower loss than any other waveguide, but have not yet achieved this potential because of a tradeoff between loss and single-moded operation. This paper demonstrates progress on a strategy to beat this tradeoff: we measure the first hollow-core fiber employing Perturbed Resonance for Improved Single Modedness (PRISM), where unwanted modes are robustly stripped away.

Optical parametric oscillator based on four-wave mixing in microstructure fiber.

We demonstrate, for the first time to our knowledge, optical parametric oscillation based on four-wave mixing in microstructure fiber. The measured wavelength-tunability range of the device (40 nm) and the threshold-pump peak power (34.4 W) are in good agreement with the theory of four-wave mixing in optical fibers.

Long-term carrier-envelope phase coherence.

The carrier-envelope phase of the pulse train emitted by a 10-fs mode-locked laser has been stabilized such that carrier-envelope phase coherence is maintained for at least 150 s (measurement limited). The phase coherence time was measured independently of the feedback loop.

Frequency-resolved optical gating and single-shot spectral measurements reveal fine structure in microstructure-fiber continuum.

Cross-correlation frequency-resolved optical gating with an angle-dithered nonlinear-optical crystal permits measurement of the intensity and the phase of the ultrabroadband (as much as 1200 nm wide) continuum generated from microstructure optical fiber. Retrieval revealed fine-scale structure in the continuum spectrum. Simulations and single-shot spectrum measurements confirmed that the fine structure does exist on a single-shot basis but washes out when many shots are averaged.

Polarization mode dispersion and vectorial modulational instability in air-silica microstructure fiber.

The birefringence of an air-silica microstructure fiber has been studied by measurement of the fiber polarization mode dispersion (PMD) over the wavelength range 545-640 nm. The experimental results are shown to be in good agreement with vectorial numerical calculations, assuming an elliptical core with an eccentricity of 7%. We also report controlled experiments studying nonlinear vectorial modulation instability in the fiber, yielding 3.

Soliton squeezing in microstructure fiber.

We demonstrate, for the first time to our knowledge, the generation of squeezed light by means of soliton self-phase modulation in microstructure fiber. We observe and characterize the formation of solitons in the microstructure fiber at 1550 nm. A maximum squeezing of 2.

Nonlinear phase noise generated in air-silica microstructure fiber and its effect on carrier-envelope phase.

We present measurements of the nonlinear phase noise that is due to amplitude-to-phase conversion in air-silica microstructure fiber that is utilized to broaden the frequency comb from a mode-locked femtosecond laser to an optical octave. When the octave of the continuum is employed to phase stabilize the laser-pulse train, this phase noise causes a change in the carrier-envelope phase of 3784-rad/nJ change in pulse energy. As a result, the jitter on the carrier-envelope phase that is due to fiber noise, from 0.

First international comparison of femtosecond laser combs at the International Bureau of Weights and Measures.

The first international comparison of femtosecond laser combs has been carried out at the International Bureau of Weights and Measures (BIPM). Three comb systems were involved: BIPM-C1 and BIPM-C2 from the BIPM and ECNU-C1 from the East China Normal University (ECNU). The agreement among the three combs was found to be on the subhertz level in the vicinity of 563 THz.

Optical frequency synthesis and comparison with uncertainty at the 10(-19) level.

A femtosecond laser-based optical frequency synthesizer is referenced to an optical standard, and we use it to demonstrate the generation and control of the frequency of electromagnetic fields over 100 terahertz of bandwidth with fractional uncertainties approaching 1 part in 10(19). The reproducibility of this performance is verified by comparison of different types of femtosecond laser-based frequency synthesizers from three laboratories.

Ultrahigh-resolution optical coherence tomography by broadband continuum generation from a photonic crystal fiber.

We have developed an ultrahigh-resolution optical coherence tomographic system in which broadband continuum generation from a photonic crystal fiber is used to produce high longitudinal resolution. Longitudinal resolution of 1.3-microm has been achieved in a biological tissue by use of continuum light from 800 to 1400 nm.

Influence of scattering on transmission through long-period fiber gratings and tunable microstructure fibers.

Controlled optical scattering within or around an optical fiber provides a potentially useful mean for adjusting its transmission characteristic. This approach can complement conventional methods based on the establishment of well-defined variations in the index of refraction of the core or the cladding of the fiber. We describe the use of a highly scattering submonolayer of nanoparticles deposited onto the fiber surface for adjusting the resonance wavelength, depth, and width of an in-fiber long-period grating filter.

Dispersion measurement of tapered air-silica microstructure fiber by white-light interferometry.

Dispersion properties of novel, tapered, air-silica microstructure fibers are measured between 1.3 and 1.65 microm by white-light interferometry.