Polarized spectroscopy and SESAM mode-locking of Tm,Ho:CALGO.

A Tm,Ho:CALGO laser passively mode-locked by a GaSb-based SESAM generated pulses as short as 52 fs at a central wavelength of 2015 nm with a broad spectral bandwidth of 82 nm (full width at half maximum) owing to the combined gain profiles of both dopants for σ-polarized light. The average output power reached 376 mW at a repetition rate of 85.65 MHz.

Fractal dimension and directional analysis of elastic and collagen fiber arrangement in unsectioned arterial tissues affected by atherosclerosis and aging.

Structural proteins like collagen and elastin are major constituents of the extracellular matrix (ECM). ECM degradation and remodeling in diseases significantly impact the microorganization of these structural proteins. Therefore, tracking the changes of collagen and elastin fiber morphological features within ECM impacted by disease progression could provide valuable insight into pathological processes such as tissue fibrosis and atherosclerosis.

Diode-pumped 45 fs Yb:CALGO laser oscillator with 1.7 MW of peak power.

A high-power sub-50 fs diode-pumped Yb:CALGO laser oscillator is demonstrated. The peak power achieved for 45 fs pulses directly from the oscillator was 1.7 MW.

Broadband and efficient adiabatic three-wave-mixing in a temperature-controlled bulk crystal.

Nonlinear interactions are commonly used to access to wavelengths not covered by standard laser systems. In particular, optical parametric amplification (OPA) is a powerful technique to produce broadly tunable light. However, common implementations of OPA suffer from a well-known trade-off, either achieving high efficiency for narrow spectra or inefficient conversion over a broad bandwidth.

Femtosecond Alexandrite laser passively mode-locked by an InP/InGaP quantum-dot saturable absorber.

An Alexandrite laser passively mode-locked using an InP/InGaP quantum-dot semiconductor saturable absorber mirror (QD-SESAM) was demonstrated. The laser was pumped at 532 nm and generated pulses as short as 380 fs at 775 nm with an average output power of 295 mW. To the best of our knowledge, this is the first report on a passively mode-locked femtosecond Alexandrite laser using a SESAM in general and a QD-SESAM in particular.

High-power diode-pumped Kerr-lens mode-locked bulk Yb:KGW laser.

A high-power (>1  W) pure Kerr-lens mode-locked bulk Yb:KGW laser with multimode fiber-coupled diode pumping was demonstrated. The laser delivered 240 fs pulses with 2.3 W of average output power at 86.

High peak power ultrafast Yb:CaF oscillator pumped by a single-mode fiber-coupled laser diode.

We demonstrate a high peak power mode-locked Yb:CaF oscillator pumped by a single-mode laser diode. The laser operated in hybrid Kerr-lens and SESAM mode-locked regime. Its performance was optimized by varying the output coupler ratio.

Microchip Yb:CaLnAlO lasers with up to 91% slope efficiency.

Multi-watt continuous-wave (CW) operation of tetragonal rare-earth calcium aluminate Yb:CaLnAlO(Ln=Gd,Y)) crystals in plano-plano microchip lasers was demonstrated with an almost quantum-defect-limited slope efficiency. Pumped at 978 nm by an InGaAs laser diode, a 3.4 mm long 8 at.

Discretely selectable multiwavelength operation of a semiconductor saturable absorber mirror mode-locked Nd:YVO laser.

We report on a semiconductor saturable absorber mirror mode-locked Nd:YVO laser operating at discretely selectable 1064.0, 1073.0, 1085.

Sellmeier equations, group velocity dispersion, and thermo-optic dispersion formulas for CaLnAlO (Ln = Y, Gd) laser host crystals.

We studied the refractive index and dispersive properties of the tetragonal rare-earth calcium aluminates, CaLnAlO (Ln=Gd or Y). Sellmeier equations were derived for the spectral range of 0.35-2.

Polarization anisotropy of thermal lens in Yb:KY(WO) laser crystal under high-power diode pumping.

Thermal lensing was studied in an N-cut monoclinic Yb:KY(WO) (Yb:KYW) laser crystal under high-power diode pumping at ∼980  nm, for the two principal light polarizations, E||N and E||N. For both polarizations, the thermal lens (TL) was positive. It was found that operation of an Yb:KYW laser with the E||N polarization corresponds to a weaker TL that results in a better quality of the laser beam and superior power scaling capabilities.

Diode-pumped Nd:YVO laser with discrete multi-wavelength tunability and high efficiency.

Selectable and discretely tunable multi-wavelength diode-pumped Nd:YVO laser operating at 1064.0, 1073.1, and 1085.

Multiwatt continuous wave Nd:KGW laser with hot-band diode pumping.

We have demonstrated what we believe is the first continuous wave neodymium-doped potassium gadolinium tungstate crystal (Nd:KGW) laser with hot-band diode pumping at ∼910  nm. This pumping wavelength reduced the quantum defect by >46% as compared to conventional ∼810  nm pumping and resulted in significantly lower thermal lensing. The laser produced 2.

Femtosecond Kerr-lens mode-locked Alexandrite laser.

The generation of 170 fs pulses at 755 nm from a Kerr-lens mode-locked Alexandrite laser was demonstrated. The laser was pumped at 532 nm and produced 780 mW of average output power with 9.8% of optical-to-optical efficiency.

High efficiency passively mode-locked Nd:YVO laser with direct in-band pumping at 914 nm.

We report on the performance of a semiconductor saturable absorber mirror passively mode-locked Nd:YVO laser with in-band pumping at 914 nm and with the highest slope efficiency to date among the mode-locked Nd-lasers. The laser produced 6.7 W of output power with repetition rate of 87 MHz and pulse duration of 16 ps.

High-power continuous-wave dual-wavelength operation of a diode-pumped Yb:KGW laser.

High-power dual-wavelength diode-pumped Yb:KGW laser using a single birefringent filter plate was demonstrated. Two oscillating wavelengths maintained the same polarization and stable dual-wavelength operation at 1014.6 and 1041.

Megawatt peak power level sub-100 fs Yb:KGW oscillators.

We report on the first demonstration, to the best of our knowledge, of sub-100 fs pulses directly from the diode-pumped mode-locked Yb:KGW bulk oscillators operated at a low repetition rate. The 36 MHz oscillator delivered 78 fs pulses with pulse energy of 50 nJ and peak power of 0.65 MW.

Dynamic characterization of intracavity losses in broadband quasi-three-level lasers.

We present a simple, fast and accurate technique to characterize intracavity losses in broadband quasi-three-level lasers based on spectroscopic gain analysis. The technique is based on spectral gain measurement and potentially can be used at any laser output power levels, thus allowing a dynamic optimization of laser performance. Successful experimental demonstration was carried out with a diode-pumped Yb:KGW continuous wave oscillator.

Quantitative nonlinear optical assessment of atherosclerosis progression in rabbits.

Quantification of atherosclerosis has been a challenging task owing to its complex pathology. In this study, we validated a quantitative approach for assessing atherosclerosis progression in a rabbit model using a numerical matrix, optical index for plaque burden, derived directly from the nonlinear optical microscopic images captured on the atherosclerosis-affected blood vessel. A positive correlation between this optical index and the severity of atherosclerotic lesions, represented by the age of the rabbits, was established based on data collected from 21 myocardial infarction-prone Watanabe heritable hyperlipidemic rabbits with age ranging between new-born and 27 months old.

Powerful 67 fs Kerr-lens mode-locked prismless Yb:KGW oscillator.

We report on the generation of 67 fs pulses from a diode pumped Kerr-lens mode-locked Yb:KGW bulk laser. The average output power reached 3 W, corresponding to >38 nJ of pulse energy and >570 kW of peak power. The mode locking was initiated by a semiconductor saturable absorber.

Collagen morphology and texture analysis: from statistics to classification.

In this study we present an image analysis methodology capable of quantifying morphological changes in tissue collagen fibril organization caused by pathological conditions. Texture analysis based on first-order statistics (FOS) and second-order statistics such as gray level co-occurrence matrix (GLCM) was explored to extract second-harmonic generation (SHG) image features that are associated with the structural and biochemical changes of tissue collagen networks. Based on these extracted quantitative parameters, multi-group classification of SHG images was performed.

Nonlinear optical microscopy in decoding arterial diseases.

Pathological understanding of arterial diseases is mainly attributable to histological observations based on conventional tissue staining protocols. The emerging development of nonlinear optical microscopy (NLOM), particularly in second-harmonic generation, two-photon excited fluorescence and coherent Raman scattering, provides a new venue to visualize pathological changes in the extracellular matrix caused by atherosclerosis progression. These techniques in general require minimal tissue preparation and offer rapid three-dimensional imaging.

Evaluation of texture parameters for the quantitative description of multimodal nonlinear optical images from atherosclerotic rabbit arteries.

The composition and structure of atherosclerotic lesions can be directly related to the risk they pose to the patient. Multimodal nonlinear optical (NLO) microscopy provides a powerful means to visualize the major extracellular components of the plaque that critically determine its structure. Textural features extracted from NLO images were investigated for their utility in providing quantitative descriptors of structural and compositional changes associated with plaque development.

Differential microscopy for fluorescence-detected nonlinear absorption linear anisotropy based on a staggered two-beam femtosecond Yb:KGW oscillator.

We present a new laser system and nonlinear microscope, designed for differential nonlinear microscopy. The microscope features time-correlated single photon counting of multiphoton fluorescence generated by an alternating pulse-train of orthogonally polarized pulses. The generated nonlinear signal is separated using home-built electronics.

Efficient frequency doubling of a femtosecond Yb:KGW laser in a BiB3O6 crystal.

Efficient frequency doubling of a high-power femtosecond Yb:KGW laser in a nonlinear BiBO crystal is demonstrated. Green second harmonic generation with more than 1.1 W of average power and 41% conversion efficiency was achieved using a single-pass configuration.