Alena Zavadilová

Mode locked Nd:YVO4 laser with intracavity synchronously pumped optical parametric oscillator

The motivation of this work is the development of laser sensor and gyroscope based on short pulse solid state ring laser. In comparison with regular ring laser containing the gain medium and saturable absorber, where counterpropagating pulses overlap, a ring synchronously pumped optical parametric oscillator, in which the pulse crossing point is controlled externally by the time of arrival of the pump pulses, is the ideal source for short pulse laser sensor. The optimum configuration is a synchronously pumped parametric oscillator inserted inside the optical resonator of the diode pumped mode-locked solid state laser. We are developing a such system, as a first step we have demonstrated operation of a diode pumped Nd:YVO4 passively mode-locked laser using semiconductor saturable absorber with synchronously pumped intracavity optical parametric oscillator in linear configuration. The repetition rate of the pump laser was 132 MHz and the pulse duration of 15 ps. Parametric oscillator was based on 20 mm long Brewster cut single grating (with poling periode of 30.3 μm) periodically poled magnesium doped lithium niobate (MgO:PPLN) crystal. The temperature tuning of parametric luminescence from the crystal with peak wavelength at 1537 nm - 1550 nm for temperature variation from 30 °C to 57 °C was observed.

Pulse repetition rate multiplication in an intracavity synchronously pumped ring optical parametrical oscillator

The possibility of pulse repetition rate multiplication by a high factor was demonstrated in a ring optical parametrical oscillator intracavity synchronously pumped by a picosecond modelocked Nd:YVO4 laser. The multiplication factor was controlled and scaled up to 26 by an optical parametrical oscillator and pump cavity length detuning. A pulse repetition rate of 2.12 GHz was achieved at a wavelength of 1.54 μm and an improvement of the coupled laser stability was observed. This system can be of interest for sensing applications.

Optimization of erbium-ytterbium fibre laser with simple double-clad structure

The paper deals with optimization of fibre laser based on experimental erbium- and ytterbium-doped fibre with simple double-clad structure pumped by multimode laser diode in 980 nm band. Fibre preparation and its characteristics are described. Different resonator configurations were investigated for the laser optimization, including high reflectivity fibre loop mirror. Experimental optimization ofthe pump wavelength, fibre length and output coupler ratio were carried out. The results obtained under the cladding pumping are compared with those measured with a fibre ring laser containing the same fibre single-mode pumped at 1060 nm.

The matrix influence on the determination of low uranium concentrations by laser induced fluorescence method

A measurement technique enabling the determination of low uranium concentration utilizing system used for time resolved laser induced fluorescence spectroscopy (TRLFS), based on a commercially available kinetic phosphorescence analysis method has been developed. The effect of the matrix, complexing agent, and the level of acidification on the fluorescence spectra and integral intensity was studied. The method is highly influenced by the sample matrix; particularly if different starting uranium salts are in the calibration solutions and in the samples. In the initial study of these effects, TRLFS measurements have been used in order to clarify this behavior.

Mode-locking of Pr:YAlO 3 laser by nonlinear mirror

We report on first nonlinear mirror mode-locked praseodymium based solid-state laser. As an active medium, the Pr:YAlO3 crystal was used. For mode-locking, a nonlinear BBO crystal together with a properly designed dichroic mirror were employed to form an output coupler with intensity dependent reflection. Using 1W InGaN pump laser diode, 22 mW of mean output power with pulse duration and repetition rate of ~250ps and 105 MHz, respectively, was demonstrated at 747 nm wavelength.

Intracavity interferometry using synchronously pumped OPO

The concept of system for intracavity interferometry based on the beat note detection in subharmonic synchronously intracavity pumped optical parametrical oscillator (OPO) is presented. The system consisted of SESAM-modelocked, picosecond, diode pumped Nd:YVO4 laser, operating at wavelength 1.06 μm and tunable linear intracavity pumped OPO based on MgO:PPLN crystal, widely tunable in 1.5 μm able to deliver two independent trains of picosecond pulses. The optical length of the OPO cavity was set to be exactly twice the pumping cavity length. In this configuration the OPO produces signal pulses with the same repetition frequency as the pump laser but the signal consists of two completely independent pulse trains. For purpose of pump probe measurements the setup signal with half repetition rate and scalable amplitude was derived from the OPO signal using RF signal divider, electropotical modulator and fiber amplifier. The impact of one pump beam on the sample is detected by one probing OPO train, the other OPO train is used as a reference. The beat note measured using the intracavity interferometer is proportional to phase modulation caused by the pump beam. The bandwidth of observed beat-note was less than 1 Hz (FWHM), it corresponds to a phase shift measurement error of less than 1.5 × 10-7 rad without any active stabilization. Such compact low-cost system could be used for ultra-sensitive phase-difference measurements (e.g. nonlinear refractive index measurement) for wide range of material especially in spectral range important for telecom applications.

Pump/Signal Beam Overlap Influence on Generation of Synchronously Intracavity Pumped OPO

The setup of intracavity pumped OPO, generating two independent trains of pulses at 1540 nm was improved. The laser beam astigmatism was reduced and the optimal overlap of pump and OPO beam was investigated.

Dual pulse operation of 1.5 μm picosecond intracavity synchronously pumped optical parametric oscillator

Singly resonant optical parametric oscillators (OPO) are most promising approach to sensors in which two pulses circulate independently in a cavity. The OPO should be pumped intracavity, not only to access the high intracavity power of the pump laser, but also because the two signal pulses share the same mode. The first synchronously pumped OPO were pumped intracavity by a mode-locked dye laser. Subsequent implementation with solid-state pump lasers has been plagued by a tendency to Q-switching, as well as competition between the two pulses generated in the signal cavity. In this contribution we report the improved and optimized experimental setup of an intracavity synchronously pumped OPO based on a periodically poled LiNbO3 crystal (PPLN) and of the pumping resonator of passively mode locked Nd:YVO4 laser from the point of view of achievability of stable mode-locking and compensation of the astigmatism caused by Brewster angle cut PPLN. This resulted in higher conversion efficiency due to the good overlap of pump and signal beam.

Characterization of Uranium Behavior in the Ruprechtov Site (CZ)

The Ruprechtov natural analogue site is being studied because its geological and geochemical conditions resemble sedimentary sequences which can cover potential host rocks for underground waste repositories. The uranium content, sorption and isotopic exchange were studied on five selected rock samples that represented i) layers with higher content of uranium and ii) neighboring layers with practically no uranium content with the aim to discuss processes influencing transport of uranium in the body. In addition, the titration curves of rock samples were determined and modeled by SCM and so called GC and CA approaches.

Intracavity synchronously pumped PPLN picosecond optical parametric oscillator

The goal of our work is the development of intracavity synchronously pumped optical parametrical oscillator (OPO), generating two trains of picosecond pulses inside a single cavity. These trains have the same repetition rate but they are independent and can differ in phase and carrier frequency. They can interfere on a detector, producing a beat note at the carrier frequency difference. This allows to determine very precisely the phase difference between them which is possible to use in all sensor applications where the measured physical quantity is converted into phase difference between two counter-circulating pulses. We designed a synchronously pumped OPO with nonlinear crystal (MgO:PPLN) for parametric generation inserted inside a linear resonator of a modelocked diode pumped Nd:YVO4 laser. This configuration ensures the same way for signal and pumping waves through the crystal and reduces the dead-band of the beat signal. We observed that the OPO could generate in three regimes: the desired dual pulse operation when the pump pulse produces parametric waves during both forward and return passes through PPLN crystal. Two single pulse OPO operations are possible when parametric interaction occurred only during one pass of the pump pulse through the PPLN crystal in forward or backward direction.