Emission and excitation spectra of Er-doped YAP crystals reveal a broad emission band in the eyesafe region with peaks
around 1545-nm and 1608-nm and pump-bands suitable for common 800-nm and 970-nm diode lasers, suggesting YAP
as a candidate crystalline host for diode-pumped laser in the 1.5-μm eyesafe regime. Erbium-doped YAP-crystal results
are comparable with analogous measurements on Er:Yb:YAG, which has already demostrated efficient lasing action in
the eyesafe region.
Diode-pumping with appropriately modulated pulses is used to expose subtle input / output pulse-timing characteristics
of Er<sup>3+</sup>:Yb<sup>3+</sup>-codoped systems, particularly Er<sup>3+</sup>:Yb<sup>3+</sup>:glass and Er<sup>3+</sup>:Yb<sup>3+</sup>:YAG, and study their relation to laser
efficiency. In free-running operation, these systems may persist to lase for uncommonly long time periods (up to a ms)
after the pump stops. In Q-switched operation, maximum laser output is obtained only if Q-switching is purposely
delayed for some significant additional time (typically 50-500μs) following the end of the pump pulse. Furthermore,
pump-pulse duration affects profoundly the Er<sup>3+</sup>:Yb<sup>3+</sup>-laser output performance, especially in Q-switched mode.
Numerical modeling simulations are presented, accounting for the observed effects and extrapolating them to novel
regimes of Er<sup>3+</sup>:Yb<sup>3+</sup>-laser operation.
We present LIBS experimental results that demonstrate the use of a newly compact, versatile pulsed laser source in
material analysis in view of research aiming at the development of portable LIBS instrumentation. LIBS qualitative
analyses were performed on various samples and objects, and spectra were recorded in gated and non-gated modes. The
latter is important because of advantages arising from size and cost reduction when using simple, compact spectrograph-CCD detection systems over the standard ICCD-based configurations. The new Nd<sup>3+</sup>:YAG laser source exhibited very
reliable performance in terms of laser pulse repeatability, autonomy and interface. Indeed, it can deliver a 45 mJ for 4.5 ns
pulse and work at 1 Hz. Having the ability to work in double-pulse mode, it provided versatility in the measurements
leading to increased LIBS signal intensities, improved the signal noise ratio and stabilized spectra. The first test results are
encouraging and demonstrate that this new laser is suitable for integration in compact, portable and low cost LIBS sensors
with a wide spectrum of materials analysis applications.
Q-switched operation of a novel transversely-diode-pumped bulk 1.65μm Er:Yb:YAG laser is demonstrated using a piezoelectric "FTIR" type of Q-switch. Typical output pulses of approximately 12mJ energy and 4011s duration have been obtained, suitable for telemetry and other applications. The material is transversely pumped using quasi-cw 960-nm laser-diode arrays. In Q-switched mode, lasing threshold lies in the range of 0.5-1.4J, depending on pumping conditions and output coupling, while optical slope efficiencies in the order of 1% were measured with respect to the incident pump energy. The reported system represents a rare-earth crystalline laser with superior active material and optical qualities, to challenge the established glass-host materials in the 1.6μm eyesafe wavelength region.
Pulsed Er<sup>3+</sup>:Yb<sup>3+</sup>:YAG is a novel crystalline diode-pumped laser capable of delivering high pulse energies in the 1.5-
1.7μm "eye-safe" region. This work reports efficient lasing in long-pulse and in Q-switched mode, with pulse energies in
the order of 10's of mJ, employing standard 960-nm quasi-cw semiconductor laser arrays in a direct transverse diodepumping
configuration. In free-running mode, 83mJ output, 15% slope efficiency and 0.24J pump threshold have been
attained. Q-switched operation was realized with a "frustrated total internal reflection (FTIR)" device, yielding 12.5mJ
single pulses of 41-ns FWHM duration with smooth temporal and spatial profiles. Pump temperature-tuning and pulse
duration effects on laser performance were also investigated, whereas pumping parameters optimizing pulse energy and
efficiency were determined.
We demonstrate efficient lasing of bulk diode-pumped Er3+:Yb3+:YAG at 1.645 µm. The material is transversely pumped using three quasi-cw 960-nm laser diode arrays in a simple arrangement. In the free-running mode of operation, an output pulse energy of 79 mJ is obtained at 4.7 J of incident optical pump energy. The lasing threshold lies in the range 1.0 to 1.9 J in long-pulse operation, depending on pumping conditions, and optical slope efficiencies of 2.2% to 3.4% were measured with respect to the incident pump energy. Furthermore, initial Q-switching experiments with a Co:MALO saturable absorber yielded pulses of 1.7-mJ energy and 340-ns FWHM duration. As the reported laser setup also has an uncomplicated and compact design, it represents a good crystalline rare-earth candidate system with superior material qualities to compete against the established glass-host materials in the eye-safe wavelength range.
Efficient lasing at 1.645mm of bulk diode-pumped Er<sup>3+</sup>:Yb<sup>3+</sup>:YAG is demonstrated. The material is transversely pumped using three quasi-cw 960-nm laser-diode arrays in a simple arrangement. In free-running mode of operation, output pulse energy of 79mJ is obtained at 4.7J of incident optical pump energy. Lasing threshold lies in the range of 1.0-1.9J in long-pulse operation, depending on pumping conditions, while optical slope efficiencies of 2.2-3.4% were measured with respect to the incident pump energy. Furthermore, initial Q-switching experiments with a Co:MALO saturable absorber yielded pulses of 1.7mJ energy and 340ns FWHM duration. As the reported laser setup is also characterized by an uncomplicated and compact design, it represents a good crystalline rare-earth candidate system with superior material qualities to compete against the established glass-host materials in the eyesafe wavelength range.
Under pulsed nanosecond laser irradiation of type I pure collagen over the 760 - 1070 nm spectral range, optical up- conversion of the incident radiation is observed. More specifically irradiation of collagen at 1064, 901, 892, 828, 785 and 766 nm produces monochromatic second harmonic signals at half the original wavelengths i.e. 532, 451, 446, 414, 393 and 383 nm respectively. The dependence of the second harmonic signal on the excitation intensity was found to be quadratic [log(I<SUB>532</SUB>) equals 1.92*log(I<SUB>1064</SUB>]. A weaker third harmonic signal was also observed from collagen at 355 nm when irradiated by 1064 nm nanosecond pulses. This signal was found to bear a near cubic dependence upon the irradiation intensity ]log(I<SUB>356</SUB>) equals 2.53*log(I<SUB>1064</SUB>)]. The polar distribution of the second harmonic radiation was recorded for both pure fibrous collagen as well a for collagen diluted in acetic acid and forming a semitransparent dry film. In the latter case, significant optical behavior was demonstrated, potentially important for further studies of these nonlinear phenomena and for novel applications.