Leonid Kravchik

Passively Q-switched diode-pumped Yb:YAG laser using Cr4+-doped garnets

Abstract We investigate the repetitive modulation in the kHz frequency domain of a passively Q-switched, diode-pumped Yb:YAG laser, by Cr 4+ :YAG, Cr 4+ :LuAG, and Cr 4+ :GSGG saturable absorbers. The results presented here are focused towards the design of a passively Q-switched Yb:YAG microlaser. The free-running performance of both rod and a disk Yb:YAG is characterized and experimental parameters such as gain and loss are evaluated. These values, together with the value of the stimulated emission cross-section, e.g. σ em =3.3×10 −20 cm 2 were found to fit between our experimental results and an existing numerical model which relates the experimental and physical parameters to the minimal threshold pumping power. Q-switched pulses with maximum peak power of ≈10.4 kW, with energy of ≈0.5 mJ/pulse, were extracted with 30% extraction efficiency.

Performance of diode-end-pumped Cr4+, Nd3+:YAG self-Q-switched and Nd: YAG/Cr4+:YAG diffusion bonded lasers

Abstract Self-passively Q-switching of a diode-pumped Cr,Nd:YAG, where the Cr4+ is used as a saturable absorber for the 1064 nm laser emission is reported. The maximum average output power was obtained using an output coupler of R=86%. The self-Q-switched diode pumped laser yielded 1.86-W average output power with low threshold pumping power (≈1.7-W), average slope efficiency of ≈34%, pulse duration of about 14–16 ns, and modulation frequency ranging from 2.4 to 73 kHz, depending on the input pumping power. These results are the highest reported for self-Q-switched lasers. Higher slope efficiency (42%) and shorter Q-switched pulses were obtained for a Q-switched Nd:YAG/Cr4+:YAG diffusion bonded laser. A comparison of the codoped Cr,Nd:YAG laser performance, with that of a diffusion bonded laser is reported and analyzed.

Passive Q-switched cw diode-pumped Nd-doped YAG and YVO4 lasers

CW diode pumped solid state lasers have sought for various scientific, medical and military applications, where compact reliable, stable, and highly efficient sources are desirable. There are several applications such as fiber- optic sensing or range finding which require short bursts of high peak power densities at multi-kilohertz repetition rates, and with a good beam quality. An extensive research on the properties of passively Q-switched, CW diode-pumped, ND-lasers has been conducted. We have used various pumping schemes to diode pump the Q-switched Nd:YAG and Nd:YVO4 laser crystals. Such schemes are transverse pumping by a cylindrical microlens-coupled diode array or longitudinally pumping by a fiber-coupled diode array. The passive Q- switching elements were Cr4+:YAG (polished, uncoated) and Cr4+:GGG (polished, coated), which were inserted inside the laser resonator. The 1.06 micrometers laser emission shows a repetitive modulation in the kHz frequency domain, and temporal bandwidth, full width at half maximum, in the range of 50 - 600 nsec. The modulation frequency and bandwidth depend on the characteristics of the Q-switching material (e.g. Cr4+ concentration, sample thickness) and on the input power level of the diode array used. We shall report design parameters and performance of various types of passively Q-switched and free-running diode pumped Nd-lasers. We shall present and discuss methods to increase the efficiency of Q-switched solid state lasers.

Gain mode and laser mode matching in side-pumped Nd:YVO4 and Nd:YAG lasers

Abstract We have used diode arrays in a linear configuration to side-pump both Q-switched and free-running Nd:YAG and Nd:YVO4 lasers. The gain modes of the high absorption YVO4 and the low absorption YAG were analyzed and compared. The gain distribution found was used to evaluate the pump power density, which in turn, was used to calculate the dependence of the laser pulse width on the pumping power. The theoretical Q-switch pulse width was compared with the experimental.

Repetitive modulation and passively Q-switching of diode-pumped Nd-KGW laser

We report the operation of a passively Q-switched diode end pumped Nd3+:KGW laser, which was obtained by using a Cr4+:YAG or Cr4 GGG saturable absorbers in the multikHz frequency domain. The free-running (with maximum slope efficiency of 46 %), and the passively Q-switched characteristics of Nd:KGW were investigated and the use of Nd:KGW as microlasers will be discussed.

Efficient Diode Pumped Nd:KGW Laser Grown by Top Nucleated Floating Crystal Method: Part II

Diode pumping of a laser-stress-free, Nd( 5 % at.):KGW, grown by top nucleated floating crystal (TNFC) method, is presented. The diode-pumped laser was operated both in the free-running and passively Q-switched operating modes. Under optimized conditions of resonator and optics, the Nd:KGW disk (1.3 mm in thickness), produced at room temperature an efficient free-running, TEM00 output with maximum power of 0.4-W, with 75 % slope efficiency and 51 % total laser efficiency. Under slightly different experimental conditions the laser was passively Q-switched by using Cr4+:YAG as saturable absorber. The passively Q-switched laser produced modulated pulses at average frequencies in the range of 10-20 kHz, with pulsewidth of ≈180 nsec, with an average output power obtained was 30 mW at the maximumpumping power level. The results presented here indicate the potential Nd:KGW crystals grown by TNFC growth method, as candidates for concentrated, stress free diode pumped microlasers in a large variety of wavelengths, including the eye-safe range.

Repetitive modulation and passive Q-switching of diode end-pumped Nd-KGW laser

We report the operation of a passively Q-switched diode end pumped Nd3+:KGW laser, which was obtained by using a Cr4+:YAG or Cr4+:GGG saturable absorbers in the multi-kHz frequency domain. The free-running (with maximum slope efficiency of 46%), and the passively Q-switched characteristics of Nd:KGW were investigated and the use of Nd:KGW as microlasers will be discussed.

Gain- and laser-mode studies of diode-side-pumped Nd-doped lasers

The performance (in terms of output power and slope efficiency) of the passively Q-switched Nd:YAG and Nd:YVO4 lasers, both side pumped and end-pumped, will be reported and compared to our theoretical model. Passive Q- switch operation by a Cr4+:GGG element as a saturable absorber was studied in terms of pulse frequency as a function of pump power.

Efficient diode-pumped Nd:KGd(WO4)2 laser grown by top nucleated floating crystal method

Diode pumping of a stress-free, Nd(5%at.):KGd(WO4)2, grown by top nucleated floating crystal (TNFC) method, is presented. The diode-pumped laser was operated both in the free-running and passively Q-switched operating modes. Under optimized conditions of resonator and optics, the disk (1.3 mm in thickness), produced at room temperature an efficient free-running, TEM00 output with maximum power of 0.4 W, with 75% slope efficiency and 51% total laser efficiency. The results presented here indicate the potential Nd:KGd(WO4)2 crystals grown by TNFC growth method, as candidates for concentrated, stress free diode pumped microlasers in a large variety of wavelengths, including the eye-safe range.

Performance of diode-end-pumped Cr4+, Nd3+:YAG self Q switched and Nd:YAG/Cr4+:YAG diffusion-bonded lasers

Self passively Q-switching of a diode-pumped Cr,Nd:YAG, where the Cr4+ is used as a saturable absorber for the 1064 nm laser emission is reported. The maximum average output power was obtained using an output coupler of R=86%. The self Q-switched diode pumped laser yielded 1.86-W average output power with low threshold pumping power (≈1.7-W), average slope efficiency of ≈34%, pulse duration of about 14-16 nsec, and modulation frequency ranging from 2.4 kHz-73 kHz, depending on the input pumping power. Higher slope efficiency (42%) and shorter Q-switched pulses were obtained for a Q-switched Nd:YAG/Cr4+:YAG diffusion bonded laser. A comparison of the codoped Cr,Nd:YAG laser performance, with that of a diffusion bonded laser is reported and analyzed.