Efficient wavelength conversion with high-power passivelyQ-switched diode-pumped neodymium lasers

Powerful CW diode-pumped Nd:YAG and Nd:YVO4 lasers Q-switched by Cr:YAG saturable absorbers demonstrate efficient (30%-60%) harmonic and parametric conversion, generating hundreds of milliwatts from ultraviolet to mid-infrared     

Amplification of a low-power picosecond Nd:YVO/sub 4/ laser by a diode-laser side-pumped grazing-incidence slab amplifier

An optimized diode-laser side-pumped grazing-incidence Nd:YVO/sub 4/ amplifier was used to increase the power of a 50-mW 150-MHz continuous-wave (CW)-pumped mode-locked oscillator up to 6.1 W in single pass, with 22% optical-to-optical efficiency, or up to 8.4 W in double pass, with 30% efficiency. Both beam quality (M/sup 2/<1.4 from TEM/sub 00/ seed pulses) and pulse duration (7.5 ps from 6.9 ps) were preserved. Single- or double-pass small-signal gain greater than 40 dB was achieved. These experimental results have been corroborated by a numerical model analysis of the amplifier.     

Optical spectroscopy and diode-pumped laser performance ofNd3+ in the CNGG crystal

We have exploited the broad absorption and emission bandwidth of the laser crystal Ca₃(NbGa)_2-xGa₃O₁₂ doped with Nd³⁺ to develop a tunable and mode locked diode-pumped 1.06 μm laser. We also present the fluorescence and excitation spectra at different crystal temperatures from 10 to 298 K. The spontaneous transition probabilities, the branching ratios, and the radiative lifetime are calculated by means of the Judd-Ofelt theory and compared with the experimental results. The stimulated emission cross-sections of the most important transitions have been calculated and compared with laser results. Employing a 2-W laser diode as a continuous-wave pump source, we have been able to tune the emission wavelength in the range 1053-1074 nm. Active mode-locking yielding pulses of 9.6, 18, and 19.7 ps at the three main emission peaks of 1058.6, 1061.2, and 1065.3 nm, respectively. was also demonstrated     

Low misalignment sensitivity Kerr-lens mode-locked femtosecond Cr/sup 4+/:Forsterite laser for nonlinear microscopy

We optimized a Kerr-lens mode-locked (KLM) femtosecond Cr/sup 4+/:forsterite laser using a five-mirror cavity, taking advantage of its peculiar low misalignment sensitivity and using an effective KLM mapping technique. A simple scanning nonlinear microscope based on this laser source has been developed and second harmonic images of the layered structure of a microchip are presented.     

Spectroscopic analysis and diode-pumped laser results of Nd:BaY/sub 2/F/sub 8/

Single crystals of monoclinic BaY/sub 2/F/sub 8/, doped with different Nd/sup 3+/ concentrations, were successfully grown by means of the Czochralski method. Here, we present a polarized infrared (IR) spectroscopic investigation and diode-pumped continuous-wave laser results in the 1 /spl mu/m wavelength region. Moreover for the first time 1.3 /spl mu/m laser emission has been characterized. Q-switching results in the 1-/spl mu/m region are also presented.     

Design and characterization of a diode-pumped, single longitudinal and transverse mode, intracavity-doubled cw Nd:YAG laser

We report on the experimental results of a diode-pumped, intracavity-doubled cw Nd:YAG laser, pumped by a 10-W fiber-coupled semiconductor laser at 808 nm and emitting as much as 600 mW in a stable single longitudinal mode and TEM(00) spatial mode. We discuss the main issues of the resonator design and the optimization of the intracavity second harmonic conversion by interpreting our results using simple models. Improvements for the current project are also discussed.     

High-Repetition-Rate Q-Switched Diode-Pumped Nd:YAG Laser at 1.444 mum

A diode-pumped Q-switched Nd:YAG laser that operates at the eye-safe 1444 nm wavelength has been developed. When pumped by a 10-W fiber-coupled array at 808 nm, it generated 1 W in cw operation and 560 mW at 20-kHz repetition rate with active Q-switching. Design issues such as thermal lensing characterization and beam quality are discussed.     

Diode-pumped neodymium lasers repetitively Q-switched by Cr4+:YAG solid-state saturable absorbers

We report on the experimental results of a continuously diode-laser pumped Nd:YAG laser, operating at 1064 nm and repetitively Q-switched by a Cr⁴⁺:YAG solid-state saturable absorber. End-pumping the Nd:YAG with a 10-W fiber-coupled diode-laser we could either optimize the energy or the average output power, depending on the choice of the saturable absorber and the output coupler. The maximum energy was ≈200 μJ in single TEM₀₀, 17 ns pulses at 6 kHz, whereas a maximum average power of ≈2 W with 32-ns pulses at 20 kHz was obtained. We also present preliminary results of a repetitively Q-switched Nd:YVO₄ laser at 1064 nm. The repetitive Q-switching operation is described by an improved model, which accounts for the behavior of both the active medium and the solid-state saturable absorber. The results of the model agree fairly well with the experimental data. Experimental results of second harmonic conversion are also reported and interpreted using a depleted pump model     

Picosecond pulse generation and its simulation in a nonlinear optical mirror mode-locked laser

A nonlinear mirror composed of a lithium triborate crystal and a dichroic output coupler is used to passively mode lock an Nd:YVO4 laser that is pumped by a diode laser array. A mode-locked output power of 3.2 W, a repetition rate of 178 MHz, a pulse width of 8.4 ps, and a beam quality parameter (M2) of 1.27 are obtained at 1064 nm for a pump power of 10.0 W. The numerical simulation for the steady-state pulse width agrees well with the bandwidth-limited value. A double-pass average gain g(ave) is defined by considering the constancy of the output energy. In the simulation g(ave) is kept as a free parameter, and its value required for the bandwidth-limited pulse is found to be 0.047, whereas its calculated value, based on our definition, is 0.057.     

Optimizing Single‐Walled‐Carbon‐Nanotube‐Based Saturable Absorbers for Ultrafast Lasers

The application of single‐walled carbon nanotubes (SWCNTs) as saturable absorbers (SA) in a Nd:glass femtosecond laser is verified as a promising alternative to traditional semiconductor saturable‐absorber mirrors (SESAMs). The shortest laser pulses achieved with a SWCNT‐SA fabricated by the slow‐evaporation method are reported herein. Nearly Fourier‐limited 288 fs pulses are obtained with negative‐dispersion soliton mode‐locking. The importance of the properties of the starting material, such as the degree of purity and the chirality, and the successive slow‐evaporation deposition method is proven by using a multitechnique approach based on X‐ray diffractometry, scanning electron microscopy, and μ‐Raman spectroscopy. The high degree of nanotube alignment on the glass substrate and also the slight metallic character due to electron transfer between the glass matrix and the nanotubes themselves are identified as the main features responsible for the good laser response.