Alexander V. Kir'yanov

Experimental study and modeling of a diode-side-pumped Nd: YVO4 laser

The design of three cavities for a solid-state Nd:YVO4 laser side-pumped by a diode laser is presented as well as the theoretical model and computed simulation developed to describe each system. The computed results are compared with the experiments demonstrating to be in accordance with each other. It is found that an elliptical cavity provides the best balance between the laser output power and quality of a transversal beam profile.

2.05-µm Holmium-doped all-fiber continuous-wave laser at in-core diode pumping at 1.125 µm

We report a Holmium-doped all-fiber laser oscillating in continuous-wave at ~2.05 μm, at in-core pumping by a 1.125-μm laser diode. The active fibers employed are alumino-germano-silicate fibers doped with Ho3+ at concentrations of ~1.2×1019 and ~1.8×1019 cm-3. The laser is implemented in non-optimized Fabry-Perot cavity’s geometry, composed of a couple of fiber Bragg gratings with reflectivity of 99 and 90%. When using the lower doped Holmium-doped fiber of proper length (1.4 m), low threshold (~370 mW) and moderate slope efficiency (~13%) of ~2.05-μm lasing were obtained. High-brightness (laser line’s width is ~60 pm) and good noise-to-signal ratio (<0.006) are the laser’s attractivities. In case of the heavier doped fiber of optimal length (1.2 m), the laser output (threshold of ~430 mW, slope efficiency of ~9%, output power of ~9 mW, laser line’s width of 110 pm, noise-to-signal ratio of <0.009) is worse, with a probable reason being deteriorating Ho3+ concentration effects.

CW 1.06-μm pumped ytterbium-holmium co-doped all-fiber laser for 2.05 μm

An Ytterbium-Holmium co-doped all-fiber CW laser is reported. The fiber used in the laser setup has been fabricated through the conventional MCVD process in conjunction with the SD technique and finally drawn using a standard fiberdraw tower. The laser was built in a linear Fabry-Perot configuration in which two fiber Bragg gratings reflecting at 2.05 μm were used as the cavity couplers. Under 1.06-μm in-core pumping of the fiber, CW lasing at 2.05 μm was provided due to energy transfer Yb3+→Ho3+. The laser demonstrated low threshold (~0.8 W), moderate slope efficiency of lasing (~8.4% when measured vs. pump power launched into the active fiber), and high stability: during 6 hours its output power fluctuated within a 3% range. The laser spectrum width at a 3-dB level using an optical spectrum analyzer with a 37-pm resolution was measured to be ~70 pm.

Modeling, fabrication and characterization of large-mode-area photonic crystal fibers with low bending loss

Large-mode-area photonic crystal fibers with a limited number of air channels in the cladding are investigated theoretically and experimentally. An impact of the relative hole diameter on single-mode operation, the fiber transmission, and bending loss is addressed in detail.

Diode-side-pumped Nd:YVO 4 laser Q-switched with LiF:F 2 - crystal

Passive Q-switching (PQS) of a diode-side-pumped Nd:YVO4 laser using a LiF:F2 - crystal as a saturable absorber is reported. Using the grazing-incidence cavity geometry, we obtain trains of giant pulses of duration as short as ~10 ns and peak power of hundreds of Watts. The laser efficiency and beam quality in the PQS regime are shown to essentially depend on the cavity arrangement and output coupler reflectivity. In particular, maximum output power of 18.5 W at high-quality (TEM00 mode) PQS operation is obtained at pump power of 38 W and asymmetrical cavity with output coupler of reflectivity 30%.

Experimental study and theoretical modeling of a self-Q-switched all-fiber Erbium laser

A self-Q-switched diode-pumped Erbium fiber laser is implemented in an all-fiber configuration. The laser operates in a stable regime of giant pulses in a broad range of pump powers and does not require additional intra-cavity elements except the active fiber and fiber Bragg gratings as output couplers. A modeling of the laser is developed, implying that the mechanism of self-Q-switching is the power-dependent thermo-induced lensing in Erbium active fiber that stems from the excited-state absorption at the laser wavelength.

Study of the absorption saturation mechanism in a YAG:Cr4+ crystal by the Z-scan technique with taking into account of the nonlinear absorption anisotropy

Absorption saturation features and the correspondent nonlinear change of refractive index in a Cr4+:YAG crystal are studied applying the Z-scan technique in steady- state at wavelength 1.06 micrometers with taking into account of the crystal nonlinear absorption anisotropy.

Optical voltage sensing: the influence of photoconductivity on sensor parameters

The influence of photoconductivity upon operation of a Bi12TiO20-based optical voltage sensor is reported. We have demonstrated, that the presence of photoconductivity defines non-uniform sensitivity of the sensor in the cross section of an infrared light beam. The sensitivity of the sensor is shown to depend on the intensity of light as a consequence of photoconductivity of a crystal. An agreement between our theoretical model and experimental results has been demonstrated.