Continuous-wave, singly-resonant optical parametric oscillators pumped internal to Nd:YVO₄ lasers

Optical parametric oscillators;Solid-state lasers

Stothard, David James Mark ; Dunn, Malcolm H. ; Dunn, Malcolm H.

University:University of St Andrews

Department:Physics & Astronomy (School of)

关键词: Optical parametric oscillators;    Solid-state lasers;   

Others  :  https://research-repository.st-andrews.ac.uk/bitstream/handle/10023/15579/DavidStothardPhDThesis.pdf?sequence=2&isAllowed=y

来源: DR-NTU

【 摘 要 】

The advent of new quasi phase matched materials and high spectral/spatial quality pumpsources has led to a renaissance in the development of continuous-wave opticalparametric oscillators for the coherent generation of broadly tunable light in the mid infrared spectral region. This thesis describes a novel technique which overcomes thethreshold constraints of the singly resonant oscillator (SRO) and stability constraints ofthe doubly resonant oscillator (DRO) traditionally associated with these devices byplacing a singly resonant optical parametric oscillator in the high circulating field foundwithin the cavity of a laser: the intracavity optical parametric oscillator.An SRO based upon the nonlinear material periodically poled LiNb0₃ (PPLN) operatinginternal to an all solid state, 1W diode pumped Nd:YV0₄ mini-laser is demonstrated andcharacterised. This system exhibits SRO threshold at only 330mW of external diodepump power, and produced a total of 70mW of extractable idler at 1W diode pumppower. Through multi-parameter tuning of the poled nonlinear material we demonstratebroad tuning of the non-resonant idler through the spectrally important range 3.1 - 4μm.Novel cavity design desensitises the system to the effects of thermal lensing in thenonlinear medium, resulting in stable spatial and mean power outputs. The short termpump field stability is characterised by intensity modulation brought about by the onset ofrelaxation oscillations ; a consequence of placing the SRO within the cavity of the pumplaser.A comparative study of SRO's based upon PPLN and the new material periodically poledRbTi0As0₄ (PPRTA) pumped internal to a high power fibre coupled diode pumpedNd:YV0₄ laser cavity is undertaken and presented. We see that although the nonlinearityand interaction length of the PPRTA is smaller than that of PPLN, the system based uponPPRTA outperforms or is at least comparable with that based upon PPLN in every respectwith the exception of idler tuning range. We attribute this to the reduced sensitivity of thismaterial to the effect of thermal lensing. Up to 440mW of extracted idler was producedby each system. The reduction of interferometric feedback of the pump field by the signalcavity mirror was found to eliminate the onset of relaxation oscillations in the case ofPPRTA but not PPLN, due to thermal air currents dominating the triggering process iniiithis system. Recently published Sellmeier equations and temperature derivatives forPPRTA are compared with the experimentally observed temperature tuning behaviour.The inclusion of an optical parametric oscillator within the cavity of the pump laserimpacts significantly upon the transient dynamics of the pump laser in which it resides.We show experimental evidence of this effect and outline a strategy to minimise theeffects of relaxation oscillations in the context of a simple numerical model which shallbe derived.Possible future avenues of research are discussed in the context of the results andconclusions obtained over the course of this research program.