Igor Kudryashov

110W(0.9J) pulsed power from resonantly diode-laser-pumped 1.6-μm Er:YAG laser

110W pulse power and 0.93J pulse energy have been obtained with direct resonant pumping of a 1.6-μm Er3+-doped bulk solid-state laser with two-dimensional stacks of 1.5μm InGaAsP∕InP diode lasers.

Resonantly diode laser pumped 1.6-μm-erbium-doped yttrium aluminum garnet solid-state laser

We report direct resonant diode pumping of a 1.6-μm-Er3+-doped bulk solid-state laser. Using a 1470-nm-single-mode diode laser module to pump the Er:YAG rod, an absorbed photon conversion efficiency of 26% has been obtained in this initial experiment. Analysis of the diode-pumped solid-state laser input–output characteristics suggests that the obtained slope efficiency can be doubled through the reduction of intracavity losses and pumping efficiency improvement.

Surface nanostructuring of borosilicate glass by femtosecond nJ energy pulses

We report on a feature, that of hillock-shaped damage, formed on a glass surface by femtosecond pulses of tp=180 fs [full width at half maximum (FWHM) value] duration produced by a recording beam focus with energy of 5 nJ/pulse at 800 nm wavelength (the corresponding irradiance of about 7.6 TW/cm2 was evaluated for a 0.68 μm FWHM spot size). Single hillocks of 40–50 nm height were recorded reproducibly in single-pulse irradiation. Surface nanopatterning over a large, curved area (over 200 μm2) can be achieved by implementing a confocal surface curvature tracking method that utilizes the reflection of a supplementary cw-laser beam. The ablation pattern achieved by this method is consistent with that of a Coulomb explosion.

Resonant pumping and upconversion in 1.6 μm Er 3+ lasers

A four-level, plane wave model is proposed for a resonantly pumped 1.6 μm Er3+ laser, including the effect of upconversion. A mean population approximation leads to analytical expressions for the threshold and slope efficiency that are highly accurate compared to the numerical solution. Using the beam area as an adjustable parameter, the threshold and slope efficiency agree well with data obtained using a 1% Er:YAG crystal, pumped at 1470 nm, lasing at 1617 nm, in the range 0-100°C. According to the model for this laser, the slope efficiency versus absorbed pump power is unaffected by upconversion, but the threshold is increased by a factor of 2-3. The results are important for choosing the optimum doping level and fiber or rod length.

Glass cutting by femtosecond pulsed irradiation

We report on quartz and glass cutting by a lateral scanning of femtosecond pulses (150 fs at 1 kHz repetition rate) of 800 nm wavelength at room and low pressure (5 Torr) air ambience. Pulses were focused by a low numerical aperture (NA0.1) objective lens. Optimization of fabrication conditions: pulse energy and scanning speed were carried out to achieve large-scale (millimeter-to-centimeter) cutting free of microcracks of submicron dimensions along the edges and walls of the cut. Cutting through out the samples of 0.1-0.5 mm thickness was successfully achieved without apparent heat affected zone. At low air pressure (5 Torr) ambience, redeposition of ablated material was considerably reduced. It is demonstrated that the damage on the rear surface was induced by the stress waves, which originated from the plasma ablation pressure pulse. The mechanism of femtosecond-laser cutting of transparent materials at high irradiance and the influence of stress waves generated by plasma plume are discussed.

Micro-Character Printing on a Diamond Plate by Femtosecond Infrared Optical Pulses

Processing of less than 400 nm has been performed on the surface of a diamond plate by means of a femtosecond infrared pulse laser. Various characters with a size of about 1 µm were drawn by the femtosecond pulse laser system in conjunction with a microscope equipped with a precisely controlled piezo-stage. The tightly focused laser light on the flat surface of the diamond made it possible to minimize the light-induced graphitization. The surface of the diamond plate after laser machining was analyzed by micro-Raman measurements to estimate the graphitization effect induced by laser irradiation. The obtained results indicate that graphitization increased with the number of irradiated laser pulses.

Single-frequency, Yb-free, resonantly cladding-pumped large mode area Er fiber amplifier for power scaling

We report results for a single-frequency (SF) resonantly cladding-pumped Yb-free large mode area (LMA) erbium-doped fiber amplifier (EDFA) with nearly 50% slope efficiency based on a commercial 20∕125μm Er-doped double-clad LMA fiber with a core numerical aperture of 0.07. We believe that this is the original demonstration of a SF resonantly cladding-pumped LMA EDFA. We obtained a diffraction-limited SF output of 9.3W, which is also a record power output obtained for resonantly cladding-pumped LMA EDFA.

1645-nm Q-switched Er:YAG laser with in-band diode pumping

In this work, resonant diode pumping has been demonstrated for Q-switched and CW Er:YAG solid state lasers (SSLs) at eye-safe wavelengths. Resonant pumping was realized by using high spectral brightness 1470 nm laser diodes. An efficient 1645 nm CW laser with output power >5 W in the TEM00 mode was demonstrated. Total optical-to-optical efficiency was >19%. More than 11 mJ of output pulse energy and an output peak power of ~400 kW have been achieved in the TEM00 mode for Q-switched operation.

Modeling of the type-II InGaAs/GaAsSb quantum well designs for mid-infrared laser diodes by k•p method

Different type-II InGaAs/GaAsSb quantum well design structures on InP substrate for mid-infrared emission has been modeled by six band k•p method. The dispersion relations, optical matrix element, optical gain and spontaneous emission rate are calculated. The effects of the parameters of quantum wells (thickness, composition) and properties of cladding layers were investigated. For injected carrier concentration of 5×1012 cm-2, peak gain values around 2.6-2.7 μm wavelengths of the order of 1000 cm-1 can be achieved, which shows that type-II InGaAs/GaAsSb quantum wells are suitable for infrared laser operation beyond 2μm at room temperature.

Q-switched resonantly diode-pumped Er:YAG laser

In this work, resonant diode pumping has been demonstrated for Q-switched and CW Er:YAG solid state lasers (SSLs) at eye-safe wavelengths. Resonant pumping was realized by using high spectral brightness 1470 nm laser diodes. An efficient 1645 nm CW laser with output power >3.5 W in the TEM00 mode was demonstrated. More than 11 mJ of output pulse energy in the TEM00 mode has been achieved for Q-switched operation at 20Hz repetition rate. M2 of the output beam was better than 1.5 over the entire range of output pulse energies. We achieved an output peak power of ~400 kW.