ABSTRACT
Focused femtosecond laser pulses have been used to modify the optical properties of glass doped with CdSxSe1-x nanocrystals. Large positive refractive index changes have been observed and exploited for the fabrication of photonic devices. In particular, we report on highly confining optical waveguides and single and multi-layer volume diffraction gratings.
ABSTRACT
We report on a source of ultrabroadband self-phase-stabilized near-IR pulses by difference-frequency generation of a hollow-fiber broadened supercontinuum followed by two-stage optical parametric amplification. We demonstrate energies up to 200 microJ with 15 fs pulse width, making this source suited as a driver for attosecond pulse generation.
ABSTRACT
Harmonic radiation generated in a neon gas jet by sub-10-fs laser pulses was investigated both experimentally and theoretically. The spectral profile of the harmonics with respect to the order, their intensity and relative spectral shifts were measured as a function of the position of the gas jet. The results point out spectral features typical of the quasi-single-cycle excitation regime. A nonadiabatic three-dimensional numerical model was developed, which provides harmonic spectra in remarkable agreement with the experiments.
ABSTRACT
We produce ultrabroadband self-phase-stabilized near-IR pulses by a novel approach where a seed pulse, obtained by difference-frequency generation of a hollow-fiber broadened supercontinuum, is amplified by a two-stage optical parametric amplifier. Energies up to 20 microJ with a pulse spectrum extending from 1.2 to 1.6 microm are demonstrated, and a route for substantial energy scaling is indicated.
ABSTRACT
ontinuous-wave laser operation of bulk Er:Yb:phosphate glass pumped at 980 nm by an InGaAs index-guided diode laser has been achieved for the first time to our knowledge, with 2 mW of output power obtained at 1.54 microm. To optimize pumping conditions and to investigate the effects of pump wavelength, the Er(3+):Yb(3+) glass disk has also been pumped by a Ti:Al(2)O(3) laser at 960 and 980 nm, and we obtained high output power (70 mW) and the highest slope efficiency (21% for 980-nm pumping) reported to date for a bulk Er:glass laser.
ABSTRACT
An output coupler with radially variable reflectivity, based on a Fabry-Perot interferometer made of two suitable spherical mirrors, is proposed. Application to a pulsed Nd:YAG laser with an unstable resonator has produced diffraction-limited output beams with energy up to 300 mJ.
ABSTRACT
A bulk erbium:ytterbium:phosphate glass laser has been actively mode locked at the third-order harmonic by a bulk lithium niobate phase modulator. Light pulses of 9.6-ps duration, 2.5-GHz repetition rate, and 3-mW average power at 1530-nm wavelength have been obtained.
ABSTRACT
We report on intensity noise suppression in a diode-pumped, single-frequency erbium bulk-glass laser codoped with ytterbium. Using an optoelectronic feedback circuit, we acheived a 30-dB reduction of the relaxation oscillation peak, at 160-kHz frequency, to a relative intensity noise of 2114 dByHz. A useful output power of 15 mW at 1533-nm wavelength was obtained.
ABSTRACT
The modes of a stable laser resonator containing, near one mirror, an absorbing mask with two apertures have been calculated on the basis of scalar diffraction theory and experimentally observed in a pulsed Nd:YAG laser. The mode structure has been investigated as a function of the mask geometry, and an interpretation in terms of supermodes is provided.
ABSTRACT
Analysis of dispersion produced by a lambda/4 multilayer dielectric mirror as a function of its construction parameters is presented. The amount of dispersion can be estimated from a careful inspection of the measured reflectivity curve. In some cases, which seem to be of practical relevance, the value of dispersion is such as to prevent pulses shorter than ~50 fsec from being produced in the mode-locked laser cavity.
ABSTRACT
Single-mode operation of a continuous-wave Er:Yb:phosphate glass laser pumped at 980 nm by a InGaAs index-guided diode laser has been achieved for what is to our knowledge the first time. The maximum output power obtained at 1540 nm is 10 mW, and the width of the spectral line is less than 15 kHz.
ABSTRACT
A single-frequency, diode-pumped, Er-Yb:glass microchip laser at a 1530-nm wavelength has been designed and operated. An output power of greater than 25 mW, a linewidth narrower than 1 kHz, and a slope efficiency of 22% have been obtained.
ABSTRACT
A new class of tapered reflectivity mirrors with a super-Gaussian profile R infinity exp(-kr(n)) is introduced, and a geometrical-optics approach for analysis and design of unstable resonators made with these mirrors is presented. A super-Gaussian mirror, built by a special evaporation technique, has been tested in an unstable resonator of a pulsed Nd:YAG laser, demonstrating its effectiveness in generating diffraction-limited beams.
ABSTRACT
Percutaneous transluminal balloon angioplasty (PTA) is being currently used in patients with coronary artery disease. Laser irradiation (LI) has been effective in vaporizing atherosclerotic plaques. The purpose of this work was twofold: to compare PTA and LI techniques in the recanalization of experimental obstructive arterial lesions, and to evaluate the possibility of reducing the failures and local complications and increasing the success rate of PTA by the combined use of LI. Atherosclerotic iliac stenoses were induced in 27 rabbits; lesions were evaluated angiographically before and after intervention and were studied histologically and by electron microscopy. Argon-ion LI delivered through microlens-tip optic fibers reduced the stenotic area from 64.2 +/- 21.8% to 40.3 +/- 10.7% (n = 10, P less than .01) and PTA from 60.7 +/- 15.9% to 30.4 +/- 7.7% (n = 9, P less than .01). However, percentage reduction was higher in PTA-treated stenoses (48.4 +/- 10.1% vs 34.5 +/- 13.5%, P less than .0125). In eight more rabbits, low power LI (4.55 +/- 1.25 J) was delivered after PTA in dilated segments. Post-PTA LI further decreased stenoses (from 31.2 +/- 7.8% to 29.1 +/- 8.1%, P less than .0125); laser-irradiated segments showed diffuse carbonization of the disrupted intimal layer. The normalized transtenotic pressure gradient decreased significantly in all groups: LI reduced the gradient from .40 +/- .25 to .17 +/- .07 (P = .005); PTA from .37 +/- .14 to .11 +/- .04 (P = .001); LI after PTA from .40 +/- .16 to .12 +/- .06 (P = .001). Thus, LI is effective (less than PTA) in relieving experimental atherosclerotic stenoses and seems useful when combined with PTA.
Subject(s)
Angioplasty, Balloon , Arteriosclerosis/therapy , Iliac Artery , Laser Therapy , Animals , Arteriosclerosis/surgery , Combined Modality Therapy , Diet, Atherogenic , Male , RabbitsABSTRACT
High-energy light pulses that are tunable from 1.1 to 2.6 mum, with a duration as short as 14.5 fs were generated in a type II phase-matching beta-BaB(2)O(4) traveling-wave parametric converter pumped by 18-fs pulses obtained from a Ti:sapphire laser with chirped-pulse amplification, followed by a hollow-fiber compressor.
ABSTRACT
A nanometric source of second-harmonic (SH) light with unprecedented efficiency is demonstrated; it exploits the grazing-incidence illumination of a metal tip, which is conventionally used for atomic force microscopy, by 25-fs laser pulses of a high-energy Ti:sapphire oscillator. Tip scanning around the beam focus shows that the SH generation is strongly localized at its apex. The polarization dependence of the SH light complies with the model of an on-axis nonlinear oscillating dipole.
ABSTRACT
Continuous-wave mode-locking operation of a bulk Er:Yb:phosphate glass laser, pumped by either a Ti:sapphire or an InGaAs diode laser, is reported for what is to our knowledge the first time. Pulses with a 90-ps duration, a 100-MHz repetition rate, and as much as 7-mW average power have been obtained.