Single Photonic Crystal Cavity Research Articles

Switching of Photonic Crystal Lasers by Graphene.

Unique features of graphene have motivated the development of graphene-integrated photonic devices. In particular, the electrical tunability of graphene loss enables high-speed modulation of light and tuning of cavity resonances in graphene-integrated waveguides and cavities. However, efficient control of light emission such as lasing, using graphene, remains a challenge. In this work, we demonstrate on/off switching of single- and double-cavity photonic crystal lasers by electrical gating of a monolayer graphene sheet on top of photonic crystal cavities. The optical loss of graphene was controlled by varying the gate voltage Vg, with the ion gel atop the graphene sheet. First, the fundamental properties of graphene were investigated through the transmittance measurement and numerical simulations. Next, optically pumped lasing was demonstrated for a graphene-integrated single photonic crystal cavity at Vg below -0.6 V, exhibiting a low lasing threshold of ∼480 μW, whereas lasing was not observed at Vg above -0.6 V owing to the intrinsic optical loss of graphene. Changing quality factor of the graphene-integrated photonic crystal cavity enables or disables the lasing operation. Moreover, in the double-cavity photonic crystal lasers with graphene, switching of individual cavities with separate graphene sheets was achieved, and these two lasing actions were controlled independently despite the close distance of ∼2.2 μm between adjacent cavities. We believe that our simple and practical approach for switching in graphene-integrated active photonic devices will pave the way toward designing high-contrast and ultracompact photonic integrated circuits.

Silicon-based photonic crystal nanocavity light emitters

The authors have demonstrated an up to sevenfold enhancement of photoluminescence from silicon-rich silicon nitride film due to a single photonic crystal cavity. The enhancement is partially attributed to the Purcell effect [Purcell, Phys. Rev. 69, 681 (1946)], which is predicted to be up to 35-fold by finite difference time-domain calculations for emitters spectrally and spatially aligned with the electric field. Experimentally measured cavity quality factors vary in the range of 200–300, showing excellent agreement with calculations. The emission peak can be tuned to any wavelength in the 600–800nm range.

Photonic crystal nanocavity array laser

We demonstrate a new type of laser composed of an array of coupled photonic crystal nanocavities that enables high differential quantum efficiency and output power, together with a low threshold power comparable to those of single photonic crystal cavity lasers. In our experiment, the laser efficiency increases faster than the lasing threshold with an increase in the number of coupled cavities. We observe a single mode lasing and measure the output powers that are two orders of magnitude higher than in single nanocavity lasers. Finally, we study the laser behavior theoretically and show that the benefits resulting from the coupling of cavities are due to strong cavity effects such as the enhanced spontaneous emission rate.