Control of Lasing in Biomimetic Structures with Short-Range Order

We demonstrate lasing in photonic amorphous structures that mimic the isotropic nanostructures which produce noniridescent color in nature. Our experimental and numerical studies reveal that lasing becomes most efficient at certain frequencies, due to enhanced optical confinement by short-range order. The optimal lasing frequency can be tuned by adjusting the structure factor. This work shows that lasing in nanostructures may be effectively improved and manipulated by short-range order.

Figure 1

(a) Top-view SEM image of a photonic amorphous structure consisting of a 2D array of air holes in a freestanding GaAs membrane. The lateral dimension of the array is $8.5\mu \mathrm{m}$. There are 1024 air holes with $a=255\mathrm{nm}$ and $r/a=0.3$. The white scale bar is $5\mu \mathrm{m}$. (b) Inset: spatial Fourier spectrum of the structure in (a) displays an isotropic ring pattern. The scale bar is $0.003{\mathrm{nm}}^{-1}$. Main panel: spatial correlation function $C(\Delta r)$ of the structure in (a) exhibits a damped oscillation with spatial separation $\Delta r$.

Figure 2

(a) Measured emission spectrum from a PAS in the GaAs membrane containing InAs QDs. $a=235\mathrm{nm}$, and $r/a=0.3$. The incident pump power $P=16\mu \mathrm{W}$. (b) Emission intensity of a peak at $\lambda =930\mathrm{nm}$ vs $P$. The lasing threshold is $P\sim 8\mu \mathrm{W}$. Inset: an optical image of the lasing mode at $P=16\mu \mathrm{W}$. The blue dashed square marks the border of the PAS with lateral dimension $8.5\mu \mathrm{m}$.

Figure 3

Measured intensities of lasing peaks from three PAS of $a=235\mathrm{nm}$, 255 nm and 275 nm. The filling fraction of air holes $f=0.33$ in (a) and 0.28 in (b). Laser emission intensity reaches the maximum at the normalized frequency $a/\lambda =0.26$ in (a) and 0.24 in (b).

Figure 4

(a) Calculated DOS of an amorphous array (blue solid line) and a periodic array (black dotted line) of air cylinders with $r/a=0.28$ and $n_w=2.83$. (b) $Q$ factor of resonant modes in the PAS whose structural parameters are identical to those of Fig. 3a. (c) Estimated transport mean free path $l_t$ (black solid curve) and the structure factor $S(q=2k)$ (red dashed curve) of the PAS. The blue dotted curve is the total scattering cross section $\sigma$ of a single air cylinder embedded in a dielectric host.