ABSTRACT
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 82â nm (full width at half maximum) owing to the combined gain profiles of both dopants for σ-polarized light. The average output power reached 376â mW at a repetition rate of 85.65â MHz. In the continuous-wave regime, the laser was power scaled up to 1.01 W at 2080.6 nm with a slope efficiency of 32.0%, a laser threshold of 155 mW and π-polarized emission. Polarized spectroscopic properties of Ho3+ ions in singly doped and codoped CALGO crystals were revisited to explain the observed laser performance.
ABSTRACT
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. This shortcoming can be addressed using adiabatic processes. Here, we demonstrate a novel technique towards this direction, based on a temperature-controlled phase mismatch between the interacting waves. Using this approach, we demonstrate, by tailoring the temperature profile, an increase in conversion efficiency by 21%, reaching a maximum of 57%, while simultaneously expanding the bandwidth to over 300 nm. Our technique can readily enhance the performances of current OPA systems.
ABSTRACT
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. To the best of our knowledge, this is the highest peak power in the sub-50 fs pulse regime that has ever been produced directly from any diode-pumped Yb-ion-doped laser oscillator to date. The shortest generated pulses were 38 fs long with 187 kW of peak power.
ABSTRACT
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.
ABSTRACT
We demonstrate a high peak power mode-locked Yb:CaF2 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. Pulses as short as 65 fs were generated with 0.4% transmission. Employing 5% output coupler enabled generation of 77 fs pulses with 46 kW of peak power (262 mW of average output power). We believe that such high peak powers can open a way to practical applications of single-mode diode-pumped ultrafast ytterbium lasers.
ABSTRACT
Selectable and discretely tunable multi-wavelength diode-pumped Nd:YVO4 laser operating at 1064.0, 1073.1, and 1085.2 nm was demonstrated using a single intracavity birefringent plate. Under 11.2 W of absorbed pump power, the maximum output power of more than 3.8 W for any of the three wavelengths was achieved with slope and optical-to-optical efficiencies of more than 45% and 35%, respectively.
ABSTRACT
We report on a semiconductor saturable absorber mirror mode-locked Nd:YVO4 laser operating at discretely selectable 1064.0, 1073.0, 1085.1 nm wavelengths with the average output powers of more than 2.2 W at each of the three wavelengths. The optical-to-optical efficiencies and the slope efficiencies were larger than 19% and 29% for each of the three wavelengths, and the pulse durations at the highest output powers were 13.1, 10.3, and 8.4 ps, respectively.
ABSTRACT
We studied the refractive index and dispersive properties of the tetragonal rare-earth calcium aluminates, CaLnAlO4 (Ln=Gd or Y). Sellmeier equations were derived for the spectral range of 0.35-2.1 µm. The group velocity dispersion (GVD) in CaGdAlO4 is positive at â¼1 µm, 95 fs2/mm and negative at â¼2 µm, -40 fs2/mm. The GVD values for CaYAlO4 are similar. In addition, thermo-optic coefficients, dn/dT, and thermal coefficients of the optical path were determined for CaYAlO4. dn/dT is negative at â¼1 µm, dno/dT=-7.8, and dne/dT=-8.7×10-6 K-1. Thermo-optic dispersion formulas were constructed. The obtained data are of key importance to the design of high-power mode-locked oscillators at â¼1 and â¼2 µm based on such laser hosts.
ABSTRACT
Multi-watt continuous-wave (CW) operation of tetragonal rare-earth calcium aluminate Yb:CaLnAlO4(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. % Yb:CaGdAlO4 laser generated 7.79 W at 1057-1065 nm with a slope efficiency of η=84% (with respect to the absorbed pump power). An even higher η=91% was achieved with a 2.5 mm long 3 at. % Yb:CaYAlO4 laser, from which 5.06 W were extracted at 1048-1056 nm. Both lasers produced linearly polarized output (σ-polarization) with an almost circular diffraction-limited beam (Mx,y2<1.1). The output performance of the developed lasers was modeled, yielding an internal loss coefficient as low as 0.004-0.007 cm-1. In addition, their spectroscopic properties were revisited.
ABSTRACT
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 86.8 MHz, corresponding to 97 kW of peak power and 26 nJ of pulse energy. The shortest generated pulse duration was 120 fs with 1.2 W of output power. The self-starting regime was also observed with a background continuous-wave component. The laser exhibited more than an order of magnitude higher output power when compared to the previously reported bulk Yb-ion-doped lasers with multimode laser diode pumping systems.
ABSTRACT
Thermal lensing was studied in an Ng-cut monoclinic Yb:KY(WO4)2 (Yb:KYW) laser crystal under high-power diode pumping at â¼980 nm, for the two principal light polarizations, E||Nm and E||Np. For both polarizations, the thermal lens (TL) was positive. It was found that operation of an Yb:KYW laser with the E||Np polarization corresponds to a weaker TL that results in a better quality of the laser beam and superior power scaling capabilities. The sensitivity factors of the TL in this case were M=0.37 and 0.57 m-1/W for the mg and pg principal meridional planes, respectively, and the astigmatism degree was as low as S/M=35% (for a pump beam radius of wp=175 µm). The photoelastic terms, fractional heat loading, and generalized thermo-optic coefficients were evaluated.
ABSTRACT
We report on the performance of a semiconductor saturable absorber mirror passively mode-locked Nd:YVO4 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. The slope efficiency of 77.1% and the optical-to-optical efficiency of 60.7% were achieved.
ABSTRACT
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. To the best of our knowledge, these are the shortest pulses that have been produced from a mode-locked Alexandrite laser to date.
ABSTRACT
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 1041.3 nm (7.57 THz of frequency offset) with 3.4 W of average output power and a diffraction-limited beam profile was obtained. Dual-wavelength laser operation at shorter- or longer-wavelength pairs with lower average output power could also be realized for other output-coupling transmissions.
ABSTRACT
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 â¼910 nm. This pumping wavelength reduced the quantum defect by >46% as compared to conventional â¼810 nm pumping and resulted in significantly lower thermal lensing. The laser produced 2.9 W of average output power at 1067 nm in a diffraction-limited beam for an absorbed pump power of 8.3 W. The slope efficiency and optical-to-optical efficiency were found to be 43% and 35%, respectively. Significant reduction of quantum defect offered by this pumping wavelength and availability of suitable high-power laser diodes opens up an attractive way to further power and efficiency scaling of Nd:KGW lasers.
ABSTRACT
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. The same optical index also accurately identified high-risk locations for atherosclerotic plaque formation along the entire aorta, which was validated by immunohistochemical fluorescence imaging.
Subject(s)
Atherosclerosis/pathology , Optical Imaging/methods , Plaque, Atherosclerotic/pathology , Animals , Atherosclerosis/complications , Disease Models, Animal , Disease Progression , Hyperlipidemias/complications , Microscopy, Fluorescence/methods , Myocardial Infarction/etiology , Nonlinear Dynamics , Plaque, Atherosclerotic/complications , RabbitsABSTRACT
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. The cavity was extended by inserting a 1:1 imaging telescope, allowing 85 fs pulses to be generated at a repetition rate of 18 MHz. The pulse energy up to 83 nJ was reached, corresponding to a peak power as high as 1 MW. Sub-100 fs regime was achieved by dual action of the Kerr-lens and saturable absorber (KLAS) mode locking.
ABSTRACT
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. A comparison with traditional Findlay-Clay analysis and numerical modeling was also made.
ABSTRACT
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. To the best of our knowledge, this is the highest average output power produced to date from Yb-ion based bulk lasers with such a short pulse duration.
ABSTRACT
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.