Andrey Okhrimchuk

Depressed cladding, buried waveguide laser formed in a YAG:Nd 3+ crystal by femtosecond laser writing

Depressed cladding waveguides have been formed in laser crystals by a tightly focused beam of a femtosecond laser. A laser based on a depressed cladding waveguide in a neodymium-doped YAG crystal has been demonstrated for what is believed to be the first time.

Low loss depressed cladding waveguide inscribed in YAG: Nd single crystal by femtosecond laser pulses

A depressed cladding waveguide with record low loss of 0.12 dB/cm is inscribed in YAG:Nd(0.3at.%) crystal by femtosecond laser pulses with an elliptical beam waist. The waveguide is formed by a set of parallel tracks which constitute the depressed cladding. It is a key element for compact and efficient CW waveguide laser operating at 1064 nm and pumped by a multimode laser diode. Special attention is paid to mechanical stress resulting from the inscription process. Numerical calculation of mode distribution and propagation loss with the elasto-optical effect taken into account leads to the conclusion that the depressed cladding is a dominating factor in waveguide mode formation, while the mechanical stress only slightly distorts waveguide modes.

Cascaded nonlinear absorption of femtosecond laser pulses in dielectrics

We investigated the energy deposition process leading to the waveguide inscription in transparent dielectrics both experimentally and theoretically. Parameters of multiphoton absorption process and inscription thresholds were measured in a range of materials including YAG, ZnSe, RbPb2Cl5 crystals, and in fused silica and BK7 glasses.

Waveguide-saturable absorber fabricated by femtosecond pulses in YAG:Cr4+ crystal for Q-switched operation of Yb-fiber laser

A waveguide-saturable absorber with low propagation loss is fabricated by femtosecond pulses in YAG:Cr(4+) crystal. Q-switch operation of a Yb fiber laser with the new saturable absorber having absorption saturation parameters similar to the bulk YAG:Cr(4+) crystal is demonstrated.

Dy 3+ and Pr 3+ doped crystals for mid-IR lasers

Here is presented a review of rare-earth doped crystals wherein mid-IR oscillation is demonstrated. Advantages and disadvantages of low phonon matrixes are examined.

Up-Conversion Processes Accompanying the 2.5 μm Oscillation in the RbPb 2 Cl 5 :Pr 3+ Crystal

Up-conversion processes detrimental to oscillation on the 3F3 - 3H5 transition in RbPb2Cl5:Pr3+ crystal is investigated in order to optimize the dopant ions concentration and the pump wavelength.

Single shot laser writing with sub-nanosecond and nanosecond bursts of femtosecond pulses

A method is proposed for efficient laser modification of fused silica and sapphire by means of a burst of femtosecond pulses having time separation in the range 10–3000 ps. Modification enhancement with the pulse separation increase in the burst was observed on the tens picoseconds scale. It is proposed that accumulated transient tensile strain in the excitation region plays a crucial role in modification by a sub-nanosecond burst.

The time and spatial dynamics of the YAG:Nd3+/YAG:Cr4+ microchip laser emission

Dynamics of the Q-switched microchip lasers pulse was investigated in experiment with high space and time resolution. It was found that spatial dynamics of the YAG:Nd3+/YAG:Cr4+ microchip laser emission could not be described by traditional formalism of transverse cavity modes. An alternative theoretical approach based on solution of the Maxwell scalar wave equation is presented. In our model we take into account the D2d local symmetry of the Cr4+ ions and the corresponding two types of saturable transitions.

Author Correction: Single shot laser writing with sub-nanosecond and nanosecond bursts of femtosecond pulses

A correction to this article has been published and is linked from the HTML and PDF versions of this paper. The error has not been fixed in the paper.

Laser writing with sub-nanosecond burst of femtosecond pulses using strain accumulation

Femtosecond laser direct writing and micromachining attract considerable interest for a variety of applications ranging from integrated optics and microfluidics to printable flat optics and multi-dimensional optical data storage. A regular train of femtosecond pulses generated by femtosecond oscillator or regenerative amplifier does commonly used in laser material processing. Micromachining with sub-microsecond bursts of femtosecond pulses has been applied for morphology control of structures generated via accumulation and regulation of a heat deposition [1, 2]. In addition to heating a pressure wave and rarefaction in the modified zone are important factors determining the laser induced structural changes [3]. However there is a lack of laser processing experiments with a burst exploiting accumulation of the rarefaction.