Extracting more light for vertical emission:high power continuous wave operation of 1.3-μm quantum-dot photonic-crystal surface-emitting laser based on a flat band

For long distance optical interconnects,1.3-μm surface-emitting lasers are key devices.However,the low output power of several milliwatts limits their application.In this study,by introducing a two-dimensional photonic-crystal and using InAs quantum dots as active materials,a continuous-wave,13.3-mW output power,1.3-μm wavelength,room-temperature surface-emitting laser is achieved.In addition,such a device can be operated at high temperatures of up to 90℃.The enhanced output power results from the flat band structure of the photonic crystal and an extra feedback mechanism.Surface emission is realized by photonic crystal diffraction and thus the distributed Bragg reflector is eliminated.The proposed device provides a means to overcome the limitations of low-power 1.3-μm surface-emitting lasers and increase the number of applications thereof.

Vertical-cavity surface-emitting lasers for data communication and sensing

Vertical-cavity surface-emitting lasers(VCSELs) are the ideal optical sources for data communication and sensing.In data communication, large data rates combined with excellent energy efficiency and temperature stability have been achieved based on advanced device design and modulation formats. VCSELs are also promising sources for photonic integrated circuits due to their small footprint and low power consumption. Also, VCSELs are commonly used for a wide variety of applications in the consumer electronics market. These applications range from laser mice to three-dimensional(3 D) sensing and imaging, including various 3 D movement detections, such as gesture recognition or face recognition. Novel VCSEL types will include metastructures, exhibiting additional unique properties, of largest importance for next-generation data communication, sensing, and photonic integrated circuits.

Demonstration of electrically injected vertical-cavity surface-emitting lasers with post-supported high-contrast gratings

We experimentally demonstrate for the first time to our knowledge electrically injected vertical-cavity surfaceemitting lasers(VCSELs) with post-supported high-contrast gratings(HCGs) at 940 nm. The HCG-VCSELs have two posts to support the air-suspended HCGs, which are realized by simple fabrication without critical point drying. The HCG-VCSEL achieves a threshold current of about 0.65 m A and a side-mode suppression ratio of 43.6 d B under continuous-wave operation at 25℃. Theoretically the HCG-VCSEL with a λ∕2-cavity for the transverse magnetic polarization has a smaller effective mode length of 1.38 ·(λ∕n). Thus, the relaxation resonance frequency can be increased by 16% compared with that of the conventional VCSEL. The modulation speed of 100 Gbit/s for the HCG-VCSEL is expected in the on–off keying modulation format. Our easy design of HCGVCSELs has great potential for applications in optical interconnects, sensing, illumination, and so on.

Structural and compositional analysis of(InGa)(AsSb)/GaAs/GaP Stranski-Krastanov quantum dots

We investigated metal-organic vapor phase epitaxy grown(InGa)(AsSb)/GaAs/GaP Stranski–Krastanov quantum dots(QDs)with potential applications in QD-Flash memories by cross-sectional scanning tunneling microscopy(X-STM)and atom probe tomography(APT).The combination of X-STM and APT is a very powerful approach to study semiconductor heterostructures with atomic resolution,which provides detailed structural and compositional information on the system.The rather small QDs are found to be of truncated pyramid shape with a very small top facet and occur in our sample with a very high density of∼4×10^(11) cm^(−2).APT experiments revealed that the QDs are GaAs rich with smaller amounts of In and Sb.Finite element(FE)simulations are performed using structural data from X-STM to calculate the lattice constant and the outward relaxation of the cleaved surface.The composition of the QDs is estimated by combining the results from X-STM and the FE simulations,yielding∼In_(x)Ga_(1−x)As_(1−y)Sb_(y),where x=0.25–0.30 and y=0.10–0.15.Noticeably,the reported composition is in good agreement with the experimental results obtained by APT,previous optical,electrical,and theoretical analysis carried out on this material system.This confirms that the InGaSb and GaAs layers involved in the QD formation have strongly intermixed.A detailed analysis of the QD capping layer shows the segregation of Sb and In from the QD layer,where both APT and X-STM show that the Sb mainly resides outside the QDs proving that Sb has mainly acted as a surfactant during the dot formation.Our structural and compositional analysis provides a valuable insight into this novel QD system and a path for further growth optimization to improve the storage time of the QD-Flash memory devices.

Highly-efficient VCSEL breaking the limit

VCSELs have become indispensable in the realms of datacenter networks and three-dimensional sensing thanks to their high-energy efficiencies,low-cost and the scalability of their two-dimensional arrays.VCSELs boast high energy-efficiency,exceeding 50%at low bias currents,superiority over edge-emitting lasers,particularly for optical interconnects within datacenter networks.However,there has been no breakthroughs in the efficiency of VCSELs for over a decade.