Nonlinear Optics Group - University of St Andrews

Figure 1 . Glavo-mounted etalon E2 with mirror M4 (foreground) and mirror M5 (background) of the idler cavity. The beam cube polariser POL is situated to the left of the picture (refer to figure 2 below for complete layout).

Work towards the line-narrowing of the non-collinear THz OPO is summarized in a submitted paper (the abstract of which appears below).

Abstract: We report the implementation of a technique for line-narrowing the terahertz (THz) radiation produced by devices based on non-collinear phase-matched parametric generation. By incorporating an etalon within the idler-wave cavity of such devices THz radiation may be generated such that (i) its linewidth is reduced to <5GHz compared to a free-running linewidth of 50-100GHz, and (ii) its centre frequency may be smoothly and continuously scanned over a band >100GHz, this band being settable anywhere within the coarse tuning range of the device (1-3 THz). When implemented within an “intersecting” cavity geometry, pulses of THz radiation of duration ~10ns and energy > 4nJ are generated in a compact and portable device.

Submitted publication
	T. Edwards, D.J.M. Stothard, D. Walsh, C. Rae and M. Dunn "Line-narrowed, compact and coherent source of widely tuneable terahertz radiation.," Opt. Express (submitted March 30th 2006).

Figure 2. Layout of the THz parametric generator. A fibre-coupled quasi-cw laser diode (QCW-LD) end-pumps a Nd:YAG laser gain crystal (LG) that forms part of a compact, Q-switched laser. The nonlinear medium (NL) is located inside the laser cavity defined by mirrors M1 & M2. A silicon prism array attached to one side of the nonlinear medium couples the THz output into free-space (large arrow).