Nonlinear Optics Group - University of St Andrews

In an intra-cavity OPO (IC-OPO), the nonlinear crystal is situated inside the cavity of the pump laser, allowing the large circulating laser field to be accessed and hence reducing the external pump threshold. The group's, research into IC-OPOs initially concentrated on the Ti:Sapphire intra-cavity system, shown right. The tunability of the Ti:sapphire laser is transferred to the OPO through non-critical phasematching and quasi-phasematching. These devices are capable of delivering over 500 mW of tunable infrared radiation.

Working with nonlinear crystals such as lithium niobate, RTA and KTP, much experimental and theoretical work has been done, helping to gain a greater understanding of these devices. Currently, our research in this area involves IC-OPOs based inside diode-pumped solid-state lasers such as Nd:YAG and Nd:YVO4. The compact nature of these devices makes them particularly viable as widely-tunable, mid-infrared sources for several applications.

Diode-Pumped Solid-State Intra-Cavity OPO (click for larger image).

In particular, our recent IC-OPO work has addressed one of the inherent problems with the intra-cavity configuration - relaxation oscillations. Compact systems, such as the one pictured on the right, have been developed for commercial gas-imaging systems. We have also implemented devices using several of the newer nonlinear crystals (such as the arsenate-based compounds) into the intra-cavity configuration.

Work on THz parametric generation has followed on from much of the group's intracavity OPO research. The THz parametric generator has a completely independent OPO cavity and as such is more accurately described as an "intersecting cavity OPO". The benefits of internal laser pumping are still readily apparent.

Publication Records
OPTICS EXPRESS	2010
Intracavity parametric generation of nanosecond terahertz radiation using quasi-phase-matching Walsh DA, Browne PG, Dunn MH, Rae CF,
Applied Physics Letters	2008
Line-narrowed, compact, and coherent source of widely tunable terahertz radiation Stothard DJM, Edwards TJ, Walsh D, Thomson CL, Rae CF, Dunn MH, Browne PG,
Optics Express	2006
Compact source of continuously and widely-tunable terahertz radiation Edwards TJ, Walsh D, Spurr MB, Rae CF, Dunn MH, Browne PG,
Optics Letters	2003
Compact, continuous-wave, singly resonant optical parametric oscillator based on periodically poled RbTiOAsO4 in a Nd : YVO4 laser Carleton A, Stothard DJM, Lindsay ID, Ebrahimzadeh M, Dunn MH,
JOSA B - Optical Physics	2003
Comparison of continuous-wave optical parametric oscillators based on periodically poled LiNbO3 and periodically poled RbTiOAsO4 pumped internal to a high... Stothard DJM, Fortin PY, Carleton A, Ebrahimzadeh M, Dunn MH,

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