[15a-B414-1~8] 3.2 Equipment optics and materials

▲ [15a-B414-8] Directional lasing emission based on self-organized photonic crystals with helical nanostructures

〇(D)SeongYong Cho¹, Hiroyuki Yoshida¹, Masanori Ozaki¹ (1.Osaka Univ.)

Keywords:Beam steering lasers, Photonic crystal lasers, Cholesteric liquid crystals

Photonic crystal (PC) lasers that enable the arbitrary control of the beam direction have attracted interest for various potential applications such as optical communications and holography [1]. Here, we present a self-organized PC band-edge laser that ena bles manipulation of the beam direction, based on a photo-patterned cholesteric liquid crystal (ChLC). A ChLC in which molecules are self-assembled into a periodic anisotropic structure with a helical modulation is regarded as a one-dimensional PC structure, giving a photonic band gap [2, 3]. In experiment, we artificially introduced a periodic modulation of the dielectric constant in the Γ–X direction with a periodicity of Λ. The PC structure enables the photonic band-edge to be moved away from the Γ point, causing the direction of the output beam to be shifted from the surface normal. We clearly see that the lasing emission from the device, where the red lasing beam is observed at a distance of 5.8 cm from the zero-order pump light, corresponding to an emission angle of 30°. In addition, because the PC structure can be easily modulated by exploiting the external-stimulus responsivity of LCs, we show that the device can also steer the output beam angle by controlling the helical pitch of the ChLC. The device proposed here will provide a new frontier in compact PC lasers without any complex fabrication process.
[1] Kurosaka, Y. et al. Nat. Photon. 4, 447-450 (2010).
[2] Yoshida, H. et al. Adv. Mater. 19(9), 1187-1190 (2007).
[3] Coles, H. & Morris, S. Nat. Photon. 4(10), 676 (2010).