G. Lescroart

Theoretical modelling and design of a Tm:YVO4 microchip laser

Abstract We present theoretical investigations concerning the output power and mode size of a Tm:YVO 4 microchip laser in which the crystal is uniformly cooled on the rear face and the cavity has the capability to store the pump light in order to increase pump intensity inside the amplifier medium. Good agreement with experimental results has been found.

Experimental investigations and theoretical modeling of a Tm:YVO4 microchip laser

We present experimental results on a Tm:YVO4 microchip laser pumped by a Ti:Sa laser. These results are compared with a theoretical model which is based on the thermal guiding of the emitted laser mode and a rate equation model which includes the pump beam parameters. The efficiency of the laser does not depend on the pump beam waist if its location is adapted.

Phase coupling of a linear array of 9 square CO2 cw wave guide lasers by intra-cavity spatial filtering

An experimental study of phase coupling of a linear array of 9 CO2 waveguide lasers by an intra-cavity spatial filter is presented. First the results obtained in a simple two-mirror cavity are shown. Both, theoretically and experimentally, the ability to improve the coupling efficiency by using a three-mirror cavity is shown.

Spectral characteristics of 2 μm microchip Tm:YVO4 and Tm,Ho:YLF lasers

In this paper, we present experimental results concerning the spectral emission obtained with two microchip lasers emitting in the 2 μm range. We show that high efficiency is achieved in both cases at room temperature. Nevertheless, while Tm:YVO4 oscillates always on longitudinal modes and may easily be single frequency with high power, Tm:Ho:YLF is always emitting several transverse modes for any pumping conditions with temperatures between 13°C and 35°C. This result is interpreted considering the gain of these two amplifier media and the mode guiding resulting from the thermal properties of the two host materials.

Theoretical modelling of mode formation in Tm3+:YVO4 microchip lasers

Abstract Theoretical investigations of mode formation in a Tm3+:YVO4 microchip laser are presented. Based on these new computations, we find a fair agreement between theoretical and experimental results obtained within a large pump power range and for two different pump beam sizes.

Phase filter design for efficient side lobe suppression in phase coupled CO2 waveguide lasers array

Abstract This paper deals with far field side lobes suppression of the emission of a linear array of phase coupled lasers using phase filter outside the cavity. In a first part, we numerically investigate the optimal parameters for three shapes of the phase filter versus the filling factor of the array. We report after experimental results obtained by using a linear array of nine CO 2 square waveguide lasers. Experimental results agree well with the numerical simulations.

Effects of binary phase plates on the far field diffraction pattern of an out of phase coupled linear array of waveguide lasers

In this paper we study the use of a binary phase plate for transforming the double-lobed far-field diffraction pattern of an array oscillating on the out-of-phase mode into a single-lobed pattern. We analyse, versus the filling factor of the array and the distance between the array and the phase filter, the amount of the emitted energy contained in the main lobe. We then compare, in terms of the power concentrated in the central lobe, various configurations of a linear array phase-coupled by the Talbot effect.

Phase-coupled CO2 laser array performance and lossless beam shaping

Phase coupling of medium power high beam quality lasers are of great interest for achieving high power diffraction limited beam with high gain lasers. This make it possible to set up compact and efficient sources. In this paper, we review the work performed in our laboratory concerning the coherent array of CO2 waveguide lasers. We report the various techniques used for phase coupling like Talbot effect, intra-cavity spatial filtering and anti-guiding effect and we give the relevant performances in terms of beam quality and efficiency. After, we discuss the advantages and drawbacks brought by each one. The far field diffraction pattern supplied by a series of coherent independent lasers is made of several asymmetric lobes. We then present lossless techniques making it possible to convert this multilobe asymmetric far field diffraction patterns into a single lobe symmetric beam. Last, we discuss the capability of slab CO2 laser with a graded-phase mirror cavity for generating large stable mode and, then, improving the energy extraction efficiency.

Performance and efficiency of 2-μm Tm:YVO4 and Tm,HO:YLF microchip lasers

In this paper, we present the experimental results obtained with Tm:YVO4 and Tm,Ho:YLF active medium pumped in an active mirror configuration. Optical to optical efficiency, beam quality and spectral characteristics obtained for both crystals are compared. Extensive research is being devoted to the development of solid state lasers emitting in the eye safe spectral range with the possibility of efficient diode-pumped sources. There is a promising range of applications foreseen for such devices including LIDAR, metrology and medical applications. The microchip concept, where the mirrors are coated directly on the crystal faces polished parallel, allows to set up in very compact sources with high spatial quality beams. Resulting from the compactness of the cavity, these lasers are very stable. We present in this paper the results obtained in our laboratory for both Tm:YVO4 and Tm,Ho:YLF microchip lasers.

Lossless generation of a single-lobe symmetric beam from the output of a CO2 waveguide laser array

The undesired side lobes in the far field emission of a linear array of phase coupled lasers can be reduced by using a phase correcting mirror outside the laser array cavity. Even in that case the beam has strong asymmetry and astigmatism, that can be corrected by an off-axis spherical mirror. In this Letter we show the beam obtained experimentally with this kind of correction. The global optical set-up consists of three reflective optical elements producing a nearly lossless transformation of the field distribution from a periodic repetition of small highly divergent sources to a quasi-Gaussian symmetric beam.