Scaling of metal-clad InP nanodisk lasers: optical performance and thermal effects

Abstract

A key component for optical on-chip communication is an efficient light source. However, to enable low energy per bit communication and local integration with Si CMOS, devices need to be further scaled down. In this work, we fabricate micro-and nanolasers of different shapes in InP by direct wafer bonding on Si. Metal-clad cavities have been proposed as means to scale dimensions beyond the diffraction limit of light by exploiting hybrid photonic-plasmonic modes. Here, we explore the size scalability of whispering-gallery mode light sources by cladding the sidewalls of the device with Au. The metal clad cavities demonstrate room temperature lasing upon optical excitation for Au-clad devices with InP diameters down to 300 nm, while the purely photonic counterparts show lasing only down to 500 nm. Numerical thermal simulations support the experimental findings and confirm an improved heat-sinking capability of the Au-clad devices, suggesting a reduction in device temperature of 473 K for the metal-clad InP nanodisk laser, compared to the one without Au. This would provide substantial performance benefits even in the absence of a hybrid photonic-plasmonic mode. These results give us insight into the benefits of metalclad designs to downscale integrated lasers on Si.

Single-Mode Emission in InP Microdisks on Si Using Au Antenna

“…However, we cannot experimentally verify this in our devices since the emission peaks are artificially broadened due to the blue shift discussed above and wavelength chirping in modulated semiconductor lasers. This is commonly observed in other devices from our group 18 as well as in demonstrations of pulsed semiconductor lasers from other groups. 46 − 48 …”

“…The blue shift of the resonant mode upon increasing the input power is related to the plasma dispersion effect, 45 a change in refractive index caused by the presence of free carriers, and is commonly observed in III–V semiconductor lasers. 18 , 26 , 46 Interestingly, the blue shift at 2× the threshold is in a comparable range for the different kinds of devices, but it is larger for the bare cavity case than for the antenna-coupled devices at 4× the threshold. This indicates that the antenna effectively clamps the emission wavelength of the resonant mode.…”

Waveguide coupled III-V photodiodes monolithically integrated on Si

“…As the injection current or bias voltage increases, the states with lower energy are occupied and the carriers fill the higher energy states, which results in EL with shorter wavelengths. Increased carrier injection is also predicted to influence the refractive index (plasma dispersion effect) and we observe this in our microdisk lasers [36], but as we here consider an LED without a resonant cavity, the impact of a change in refractive index should be minimal. In addition to the EL blueshift, a temperature dependent redshift of the EL peak was observed when comparing the same injection current, which is due to the bandgap shrinkage of InGaAs as the temperature of the cryostat environment increases.…”

Thermal Simulation and Experimental Analysis of Optically Pumped InP-on-Si Micro- and Nanocavity Lasers

“…In an earlier work, we evaluated the lasing behavior of metal-clad and purely photonic devices and we refer to those studies for more details. 46 The excitation laser is operated by varying the current. To map the average excitation power to driving currents of the source, the power is measured with a power meter.…”