The influence of nonlinear spectral bandwidth on single longitudinal mode intra-cavity second harmonic generation (original) (raw)
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Optik - International Journal for Light and Electron Optics, 2013
An understanding of performance of a laser system in terms of design parameters is of the great importance to the engineer who is designing a laser system. This manuscript describes a theoretical report on the optimum design key parameters of an intracavity frequency doubled end-pumped solid-state laser based on the combination of space-dependent rate equations and nonlinear coupled-wave analysis of second-harmonic generation. The theoretical framework along with the results presenting the effect of various parameters such as pump beam characteristics, gain medium and nonlinear crystal properties to optimize the SHG efficiency has been investigated. By considering the optimized root mean square of pump beam radius as the effective value of pump spot size in the gain medium and perfect phase matching between fundamental and second harmonic waves,optimum nonlinear crystal's length, optimum mode size and second harmonic output power are derived as a function of pump-beam characteristics, and properties of the nonlinear and gain medium crystals. The results show that the optimum nonlinear crystal's length depends not only on the nonlinear coefficient and spot radius of laser beam but also on the pump beam properties and gain medium characteristic. In addition, the effect of pump and gain medium properties on the optimal fundamental beam by taking into account thermal aberration are investigated. The obtained results give useful guidelines for choosing the suitable active and nonlinear crystals for a given pump source and allow the straightforward evaluation of laser parameters for efficient intracavity doubling in end-pumped solid-state lasers.
Performance optimization of an external enhancement resonator for optical second-harmonic generation
Journal of the Optical Society of America B, 2002
We study the factors that ultimately limit the performance of an external enhancement resonator for optical second-harmonic generation (SHG). To describe the resonant SHG process we introduce a theoretical model that accounts for the intensity-dependent cavity loss that is due to harmonic generation and that also includes a realistic assumption about the shape and the frequency width of the laser mode. With the help of this model we optimized the performance of a doubling cavity based on a lithium triborate (LBO) crystal. This cavity was used for frequency doubling the output of a single-frequency titanium-doped sapphire laser at 850 nm. We were able to push the total second-harmonic conversion efficiency to 53% (a 1.54-W pump resulted in 820 mW of second-harmonic light), which to our knowledge is the best result ever reported for a LBO-based doubling cavity.
Optimization of laser intracavity second-harmonic generation by a linear dispersion element
Journal of the Optical Society of America B, 1999
Changing the relative phase ⌬ between the fundamental and harmonic waves produces periodic power modulation of a laser intracavity second-harmonic generated wave. The periodic power modulations of the two counterpropagating second-harmonic waves are at exactly opposite phases. This behavior is different from that in the case of intracavity second-harmonic generation in a passive cavity. A phenomenological numerical model developed for a laser consists of double-pass second-harmonic generation. The steady-state plane-wave model incorporates second-order nonlinear interaction, laser gain, and linear dispersion that contribute to the phase difference ⌬. The model predictions are in good agreement with the experimental results. The model is useful for optimization of laser intracavity second-harmonic generation, and it may be applied to different types of intracavity nonlinear interaction.
Dynamics of cw intra-cavity second harmonic generation by PPKTP
Optics Communications, 2004
We report on quasi-phase matched intra-cavity doubling of a cw 1064 nm Nd:YVO 4 laser. In a laser pumped by a 14 W fiber coupled laser diode array, and containing a periodically poled KTP (PPKTP) doubling crystal we obtain more than 2.3 W of 532 nm radiation. The second harmonic generation (SHG) is stable for short and long times with less then 5% intensity noise (RMS). SHG in PPKTP was measured for both extra-cavity and intra-cavity configurations and it was found that intra-cavity SHG vs. temperature allows for a wider temperature range, as compared with the extracavity SHG. In addition, the intra-cavity SHG curve shows an abrupt decrease in second harmonic intensity and hysteresis as a function of the crystal temperature. This observation can be explained by self-suppression of mode hopping that exists in intra-cavity SHG systems. The broadening and hysteresis are due to the laser locking in on a particular wavelength at the fundamental although the loss is increased. Because of self-suppression mode hopping to a neighborhood longitudinal mode does not occur until the optimum phase matching wavelength is detuned by several tens of nm from the peak of the gain curve. When the jump in lasing wavelength finally occurs the detuning is much larger than the longitudinal mode spacing, so that the generated green power is very low corresponding to the abrupt decrease in SHG.
Optical and Quantum Electronics, 2003
Frequency doubling of spatially limited laser beams in nonlinear crystals is investigated theoretically. It was shown that the major factor, which reduces the second harmonic generation (SHG) efficiency in this case, is a diaphragm aperture effect, caused by influence of extraordinary polarized laser beams. In that case a spatial shift of mutually orthogonally polarized beams of the incident waves relative to each other in perpendicular direction of wave transmission at the entry to crystals lead to increase the efficiency of SHG of limited beams.
Quasi-phase-matched second-harmonic generation at vacuum ultraviolet 193 nm
CLEO: 2011 - Laser Science to Photonic Applications, 2011
By successful fabrication of fine twin structure, QPM SHG at 193 nm is achieved in crystalline quartz. Mechanical module suppressing switch back of twins enables stable wavelength conversion for all-solid-state compact vacuum-ultraviolet laser.
Conversion efficiency for second-harmonic generation in photonic crystals
Journal of The Optical Society of America B-optical Physics, 2001
ABSTRACT We derive an analytical expression for the conversion efficiency of second-harmonic generation (SHG) in a photonic crystal. The results obtained for the undepleted-pump limit allow us to describe the role played by the feedback and dispersion introduced by the photonic crystal and hence to optimize the SHG process.
Applied Physics B, 2002
We report an experimental study of the second harmonic generated in type I interaction by a Ti:Sa laser operating in the picosecond regime at 786 nm in LBO crystals. A joint characterization of the dependence of conversion efficiency and spatial beam quality on crystal length and degree of pump focusing is given. A simple heuristic formula, reproducing over a broad range of parameters the predictions of classical Boyd-Kleinman theory, is derived and compared with the experimental results. The conditions for the optimization of the generation process using an elliptically focused pump beam are quantitatively evaluated.
IEEE Journal of Quantum Electronics, 2000
An analysis model of an intracavity optical secondharmonic generation in a vertical-external-cavity surface-emitting laser (VECSEL) is presented. The model is based on the conventional semiconductor rate equations for the carrier and the photon combined with the second harmonic generation process. The parameters used in the model are obtainable from experimental data such as power transfer curves, output spectrum, and cavity configuration. The accuracy of our model is confirmed by comparing experimental and theoretical results. The influences of physically adjustable parameters in the VECSEL on both the lasing performance and the second harmonic generation were thoroughly investigated by utilizing the proposed analysis model.