O-band electrically injected quantum dot micro-ring lasers on on-axis (001) GaP/Si and V-groove Si

High-Q and high finesse silicon microring resonator

We demonstrate the design, fabrication, and experimental characterization of a single transverse mode adiabatic microring resonator (MRR) implemented using the silicon-on- insulator (SOI) platform using local oxidation of silicon (LOCOS) approach. Following its fabrication, the device was characterized experimentally and an ultrahigh intrinsic Q-factor of ∼2 million with a free spectral range (FSR) of 2 nm was achieved, giving rise to a finesse of ∼1100, the highest demonstrated so far in SOI platform at the telecom band. We have further studied our device to analyze the source of losses that occur in the MRR and to understand the limits of the achievable Q-factor. The surface roughness was quantified using AFM scans and the root mean square roughness was found to be ∼ 0.32±0.03 nm. The nonlinear losses were further examined by coupling different optical power levels into the MRR. Indeed, we could observe that the nonlinear losses become more pronounced at power levels in the range of hundreds of microwatts. The demonstrated approach for constructing high-Q and high finesse MRRs can play a major role in the implementation of devices such as modulators, sensors, filters, frequency combs and devices that are used for quantum applications, e.g., photon pair generation.

InAs/GaAs quantum dot laser epitaxially grown on on-axis (001) GaAsOI substrate

Quantum dot (QD) laser as a light source for silicon optical integration has attracted great research attention because of the strategic vision of optical interconnection. In this paper, the communication band InAs QD ridge waveguide lasers were fabricated on GaAs-on-insulator (GaAsOI) substrate by combining ion-slicing technique and molecular beam epitaxy (MBE) growth. On the foundation of optimizing surface treatment processes, the InAs/In_0.13Ga_0.87As/GaAs dot-in-well (DWELL) lasers monolithically grown on a GaAsOI substrate were realized under pulsed operation at 20 °C. The static device measurements reveal comparable performance in terms of threshold current density, slope efficiency and output power between the QD lasers on GaAsOI and GaAs substrates. This work shows great potential to fabricate highly integrated light source on Si for photonic integrated circuits.

Quantum-dot microlasers based on whispering gallery mode resonators

The subject of this paper is microlasers with the emission spectra determined by the whispering gallery modes. Owing to the total internal reflection of light on the sidewalls, a high Q-factor is achieved until the diameter is comparable to the wavelength. The light emission predominantly occurs in the plane of the structure, which facilitates the microlaser integration with other elements. We focus on microdisk lasers with various types of the In(Ga)As quantum dots (QDs). Deep localization of charge carriers in spatially separated regions suppresses the lateral diffusion and makes it possible to overcome the undesirable effect of non-radiative recombination in deep mesas. Thus, using conventional epitaxial structures and relatively simple post-growth processing methods, it is possible to realize small microlasers capable of operating without temperature stabilization at elevated temperatures. The low sensitivity of QDs to epitaxial and manufacturing defects allows fabricating microlasers using III-V heterostructures grown on silicon.

InAs/GaAs Quantum Dot Microlasers Formed on Silicon Using Monolithic and Hybrid Integration Methods

An InAs/InGaAs quantum dot laser with a heterostructure epitaxially grown on a silicon substrate was used to fabricate injection microdisk lasers of different diameters (15–31 µm). A post-growth process includes photolithography and deep dry etching. No surface protection/passivation is applied. The microlasers are capable of operating heatsink-free in a continuous-wave regime at room and elevated temperatures. A record-low threshold current density of 0.36 kA/cm² was achieved in 31 µm diameter microdisks operating uncooled. In microlasers with a diameter of 15 µm, the minimum threshold current density was found to be 0.68 kA/cm². Thermal resistance of microdisk lasers monolithically grown on silicon agrees well with that of microdisks on GaAs substrates. The ageing test performed for microdisk lasers on silicon during 1000 h at a constant current revealed that the output power dropped by only ~9%. A preliminary estimate of the lifetime for quantum-dot (QD) microlasers on silicon (defined by a double drop of the power) is 83,000 h. Quantum dot microdisk lasers made of a heterostructure grown on GaAs were transferred onto a silicon wafer using indium bonding. Microlasers have a joint electrical contact over a residual n+ GaAs substrate, whereas their individual addressing is achieved by placing them down on a p-contact to separate contact pads. These microdisks hybridly integrated to silicon laser at room temperature in a continuous-wave mode. No effect of non-native substrate on device characteristics was found.

High-temperature continuous-wave operation of directly grown InAs/GaAs quantum dot lasers on on-axis Si (001)

Laser devices for silicon photonics are expected to be implemented in an integrated environment to complement CMOS devices. For this reason, quantum dot (QD) lasers with excellent thermal properties have been considered as strong candidates for Si photonics light sources. The direct growth of QD lasers on Si (001) on-axis substrates has been garnering attention owing to the possibility of monolithic integration on a CMOS-compatible wafer. In this paper, we report on the high-temperature (over 100°C) continuous-wave operation of an InAs/GaAs QD laser directly grown on on-axis Si (001) substrates through the use of only molecular beam epitaxy.

Self-pulsing in single section ring lasers based on quantum dot materials: theory and simulations

We studied theoretically coherent phenomena in the multimode dynamics of single section semiconductor ring lasers with quantum dots (QDs) active region. In the unidirectional ring configuration our simulations show the occurrence of self-mode-locking in the system leading to ultra-short pulses (sub-picoseconds) with a terahertz repetition rate. As confirmed by the linear stability analysis (LSA) of the traveling wave (TW) solutions this phenomenon is triggered by an analogous of the Risken-Nummedal-Graham-Haken (RNGH) instability affecting the multimode dynamics of two-level lasers.

All MBE grown InAs/GaAs quantum dot lasers on on-axis Si (001)

Directly grown III-V quantum dot (QD) laser on on-axis Si (001) is a good candidate for achieving monolithically integrated Si photonics light source. Nowadays, laser structures containing high quality InAs / GaAs QD are generally grown by molecular beam epitaxy (MBE). However, the buffer layer between the on-axis Si (001) substrate and the laser structure are usually grown by metal-organic chemical vapor deposition (MOCVD). In this paper, we demonstrate all MBE grown high-quality InAs/GaAs QD lasers on on-axis Si (001) substrates without using patterning and intermediate layers of foreign material.