Our group has an extensive experience in nanophotonics with a focus on nanolasers. The quest for an integrated light source that promises high energy efficiency and fast modulation for high-performance photonic circuits has led to the development of room-temperature telecom wavelength metallo-dielectric nanolasers. These nanolasers are uniquely suitable for dense integration due to their lower optical loss and nanoscale dimensions. Currently, nanolasers are routinely fabricated by our team, leveraging our experience and expertise in this area. Our team is now focusing on their dynamic properties.
Coherence and Dynamics of a High-spontaneous emission factors Nanolasers
Metallo-dielectric nanolasers with high spontaneous emission factors (β) represent a class of ultra-compact light emitters with applications in fiber-optic communications, hybrid and all optical computing, imaging and sensing. In-depth studies on both the coherence and dynamical properties of these emitters are necessary before practical applications can be realized. However, the coherence characterization of a high-β nanolaser using the conventional measurement of output light intensity versus input pump intensity (L-L curve) is inherently difficult due to the diminishing kink in the measurement curve. We conducted the second order intensity correlation measurement, or g2(τ) — a more definitive method to confirm coherence — on a high-β metallo-dielectric nanolaser under nanosecond optical pulse pumping. Our result indicates that full coherence is achieved at three times the threshold conventionally defined by the kink in the L-L curve. Additionally, we observed that the g2(τ) peak width shrinks below and broadens above threshold. Rate-equation analyses reveal that the above-threshold broadening is due to the delayed threshold phenomenon, providing the first observation of dynamical hysteresis in a nanolaser. We propose that this dynamical phenomenon can be exploited to determine the lasing regimes of a unity-β nanolaser, whose threshold is inherently ambiguous and difficult to observe.
Low Resistance Tunnel Junctions for Efficient Electrically Pumped Nanolasers
Extremely compact nanoscale devices such as electrically pumped nanolasers are difficult to operate at room temperature due to the high electrical resistance inherent to small cavities. As a consequence, large voltages are necessary to reach the lasing threshold, which generates heat and reduces device efficiency. The poor heat sinking of small devices makes matters worse, dramatically reducing the laser efficiency. Instead of looking for solutions to dissipate heat from small structures more efficiently, designing nanolasers to produce less heat in the first place is an important goal. Here we propose and theoretically analyze the effect of adding an InGaAsP tunnel junction for efficient carrier injection in metallo-dielectric nanolasers. With our theoretical model we show that the device resistance is reduced by a factor of ∼6.5. The applied voltage at the room temperature lasing threshold is reduced from 3.05 to 1.35 V, a reduction of 69% in heat generation, whereas the Q-factor and gain threshold of the cavity are not degraded.