Proposal and numerical study of ultra-compact active hybrid plasmonic resonator for sub-wavelength lasing applications

We design an ultra-compact active hybrid plasmonic ring resonator for lasing applications at deep sub-wavelength scale. The combined contributions of hybrid plasmonic mode, circular-shaped cross section of nanowire, and ring resonator structure with round-trip whispering-gallery cavity, benefit reduced metallic absorption loss, tight mode confinement, enhanced cavity feedback, achieving high quality factor (Q), small mode volume (V), high Purcell factor (Fp), low threshold gain (Gth), and ultra-small footprint with sub-micron size. The performance dependence on the geometrical parameters, including gap height (Hg), cross section radius (Rc), and ring radius (Rr), are comprehensively analyzed, showing high Q factor of 1650 (Hg = 30 nm, Rc = 100 nm, Rr = 800 nm), ultra-small mode volume of 0.0022 μm(3) (Hg = 5 nm, Rc = 100 nm, Rr = 800 nm), cut off of all photonic modes for pure plasmonic mode lasing with Rc<70 nm (Hg = 10 nm, Rr = 800 nm), maximum Purcell factor of 813 and minimum threshold gain of 1407 cm(-1) (Hg = 5 nm, Rc = 50 nm, Rr = 400 nm). The general design rules of the presented hybrid plasmonic ring resonator provide the potential to further extend ultra-compact sub-micron lasing applications (i.e. different lasing wavelength band) with proper choice of gain materials and geometric structures.