Towards high-power MOPA architectures in single-mode fibers for mid-IR mode-locked operation.

We report on a master oscillator power amplifier (MOPA) system at 2.8 µm to achieve an average power of 10.28 W with a pulse energy and peak power of 403 nJ and 5.

Portable System for In-Clinic Differentiation of Skin Cancers from Benign Skin Lesions and Inflammatory Dermatoses.

The exquisite sensitivity of Raman spectroscopy for detecting biomolecular changes in skin cancer has previously been explored; however, this mostly required analysis of excised tissue samples using bulky, immobile laboratory instrumentation. In this study, the technique was translated for clinical use with a portable Raman system and customized fiber optic probe and applied to differentiation of skin cancers from benign lesions and inflammatory dermatoses. The aim was to provide an easy-to-use, easy-to-manage assessment tool for clinicians to use in their daily patient examination routine to perform rapid Raman measurements of skin lesions in vivo.

Raman spectroscopy and mass spectrometry identifies a unique group of epidermal lipids in active discoid lupus erythematosus.

Discoid lupus erythematosus (DLE) is the most common form of cutaneous lupus. It can cause permanent scarring. The pathophysiology of is not fully understood.

Raman spectroscopy system for real-time diagnosis of clinically significant prostate cancer tissue.

Prostate cancer (PCa) is a significant healthcare problem worldwide. Current diagnosis and treatment methods are limited by a lack of precise in vivo tissue analysis methods. Real-time cancer identification and grading could dramatically improve current protocols.

Classification of Preeclamptic Placental Extracellular Vesicles Using Femtosecond Laser Fabricated Nanoplasmonic Sensors.

Placental extracellular vesicles (EVs) play an essential role in pregnancy by protecting and transporting diverse biomolecules that aid in fetomaternal communication. However, in preeclampsia, they have also been implicated in contributing to disease progression. Despite their potential clinical value, current technologies cannot provide a rapid and effective means of differentiating between healthy and diseased placental EVs.

Raman spectroscopy reveals age- and sex-related differences in cortical bone from people with osteoarthritis.

Bone strength in human cortical bone is determined by the composition and structure of both the mineral and collagen matrices and influenced by factors such as age, gender, health, lifestyle and genetic factors. Age-related changes in the bone matrix are known to result in loss of mechanical strength and increased fragility. In this study we show how Raman spectroscopy, with its exquisite sensitivity to the molecular structure of bone, reveals new insights into age- and sex-related differences.

Femtosecond lasers for high-precision orthopedic surgery.

Laser micromachining with ultrashort pulses has shown great promise for clean, safe surgical treatment of bone tissue. However, comparisons of performance and development of "best practice" have been hampered by the difficulty of comparing results across a wide variety of experimental approaches and under surgically irrelevant conditions (e.g.

Raman rogue waves in a partially mode-locked fiber laser.

We report on an experimental study of spectral fluctuations induced by intracavity Raman conversion in a passively partially mode-locked, all-normal dispersion fiber laser. Specifically, we use dispersive Fourier transformation to measure single-shot spectra of Raman-induced noise-like pulses, demonstrating that for low cavity gain values Raman emission is sporadic and follows rogue-wave-like probability distributions, while a saturated regime with Gaussian statistics is obtained for high pump powers. Our experiments further reveal intracavity rogue waves originating from cascaded Raman dynamics.

Coherence and shot-to-shot spectral fluctuations in noise-like ultrafast fiber lasers.

We report on experimental studies of coherence and fluctuations in noise-like pulse trains generated by ultrafast fiber oscillators. By measuring the degree of first-order coherence using a Young's-type interference experiment, we prove the lack of phase coherence across the seemingly regular array of pulses. We further quantify the pulse-to-pulse fluctuations by recording the single-shot spectra of the megahertz pulse train, and experimentally demonstrate the existence of spectral fluctuations that remain unresolved in conventional time-averaged ensemble measurements.

Raman-driven destabilization of mode-locked long cavity fiber lasers: fundamental limitations to energy scalability.

We report on the destabilization of the mode-locking operation of a long cavity fiber laser. We show that the destabilization is accompanied by the abrupt emergence of a strong frequency-downshifted Stokes signal, and simultaneously, we find that the laser output displays characteristics typical of noise-like pulses. We use numerical simulations to illustrate how the Stokes signal grows from stimulated Raman scattering and plays a key role in the destabilization of the laser output.

Environmentally stable all-PM all-fiber giant chirp oscillator.

We report on an environmentally stable giant chirp oscillator operating at 1030 nm. Thanks to the use of a nonlinear amplifying loop mirror as the mode-locker, we are able to extract pulse energies in excess of 10 nJ from a robust all-PM cavity with no free-space elements. Extensive numerical simulations reveal that the output oscillator energy and duration can simply be up-scaled through the lengthening of the cavity with suitably positioned single-mode fiber.

Mode-locked femtosecond all-normal all-PM Yb-doped fiber laser using a nonlinear amplifying loop mirror.

We report on a new design for a passively mode locked fibre laser employing all normal dispersion polarisation maintaining fibres operating at 1 μm. The laser produces linearly polarized, linearly chirped pulses that can be recompressed down to 344 fs. Compared to previous laser designs the cavity is mode-locked using a nonlinear amplifying fibre loop mirror that provides an additional degree of freedom allowing easy control over the pulse parameters.

Parabolic and hyper-Gaussian similaritons in fiber amplifiers and lasers with gain saturation.

We present a new asymptotically exact analytical similariton solution of the generalized nonlinear Schrdinger equation for pulses propagating in fiber amplifiers and lasers with normal dispersion including the effect of gain saturation. Numerical simulations are in excellent agreement with this analytical solution describing self-similar linearly chirped parabolic pulses. We have also found that for small enough values of the dimensionless saturation energy parameter the fiber amplifiers and lasers can generate a new type of linearly chirped self-similar pulses, which we call Hyper-Gaussian similaritons.

Quasi-parabolic pulse propagation and breakup in fiber amplifiers with third-order dispersion.

We present an analytical solution for propagating pulses in normal dispersion fiber amplifiers, including the effect of third-order dispersion. The solution of the generalized nonlinear Schrödinger equation is based on asymptotic methods, first-order perturbation theory, and a renormalization procedure and leads to determination of the critical length corresponding to pulse breakup. We have also found and confirmed numerically the condition on the parameters that govern the propagation, as is necessary to ensure a highly accurate analytical description of the pulses and critical lengths in fiber amplifiers with third-order dispersion.

Experimental realization of a mode-locked parabolic Raman fiber oscillator.

We report here the first demonstration of a mode-locked fiber laser delivering parabolic pulses (similaritons) at 1534 nm. The use of a Raman-based gain medium potentially allows its implementation at any wavelength. The 22nJ output similariton pulses have a true parabolic shape both in the time and spectral domains and a linear chirp.

Ultra-wide parametric amplification at 800 nm toward octave spanning.

We report on a significant improvement of the total bandwidth amplified in an optical parametric process. By pumping a parametric amplifier with a broadband pump, we demonstrate amplification of a supercontinuum whose spectrum expands over nearly an octave ranging from less than 600 nm up to 1200 nm. Our amplifier stage is set to provide amplification at degeneracy in the quasi-collinear configuration with a temporally as well as angularly dispersed pump.

Stretcher-free high energy nonlinear amplification of femtosecond pulses in rod-type fibers.

We report on the study of direct amplification of femtosecond pulses in an 80 mum core diameter microstructured Yb-doped rod-type fiber amplifier in the nonlinear regime. The system includes a compact single grating compressor for the compensation of the small dispersion in the amplifier. With a 1250 line/mm (l/mm) grating-based compressor, pulses as short as 49 fs with 870 nJ pulse energy and 12 MW peak power are obtained.

Parametric amplification and compression to ultrashort pulse duration of resonant linear waves.

We report on an optical parametric amplification system which is pumped and seeded by fiber generated laser radiation. Due to its low broadening threshold, high spatial beam quality and high stability, the fiber based broad bandwidth signal generation is a promising alternative to white light generation in bulky glass or sapphire plates. We demonstrate a novel and successful signal engineering implemented in a setup for parametric amplification and subsequent recompression of resonant linear waves resulting from soliton fission in a highly nonlinear photonic crystal fiber.

High repetition rate tunable femtosecond pulses and broadband amplification from fiber laser pumped parametric amplifier.

We report on the generation of high energy femtosecond pulses at 1 MHz repetition rate from a fiber laser pumped optical parametric amplifier (OPA). Nonlinear bandwidth enhancement in fibers provides the intrinsically synchronized signal for the parametric amplifier. We demonstrate large tunability extending from 700 nm to 1500 nm of femtosecond pulses with pulse energies as high as 1.

Ultra-broad bandwidth parametric amplification at degeneracy.

We report on a novel approach of ultra-broad bandwidth parametric amplification around degeneracy. A bandwidth of up to 400 nm centered around 800 nm is amplified in a BBO crystal by using chirped pump pulses with a bandwitdth as broad as 10 nm. A supercontinuum signal is generated in a microstructured fiber, having to first order a quadratic chirp, which is necessary to ensure temporal overlap of the interacting waves over this broad bandwidth.