Nanolaser arrays: toward application-driven dense integration

The past two decades have seen widespread efforts being directed toward the development of nanoscale lasers. A plethora of studies on single such emitters have helped demonstrate their advantageous characteristics such as ultrasmall footprints, low power consumption, and room-temperature operation. Leveraging knowledge about single nanolasers, the next phase of nanolaser technology will be geared toward scaling up design to form arrays for important applications. In this review, we discuss recent progress on the development of such array architectures of nanolasers. We focus on valuable attributes and phenomena realized due to unique array designs that may help enable real-world, practical applications. Arrays consisting of exactly two nanolasers are first introduced since they can serve as a building block toward comprehending the behavior of larger lattices. These larger-sized lattices can be distinguished depending on whether or not their constituent elements are coupled to one another in some form. While uncoupled arrays are suitable for applications such as imaging, biosensing, and even cryptography, coupling in arrays allows control over many aspects of the emission behavior such as beam directionality, mode switching, and orbital angular momentum. We conclude by discussing some important future directions involving nanolaser arrays.

Effect of Conical Profile on the Transmission of Elastic Waves From Cylindrical Waveguide to Bulk

This paper studies the transmission of elastic waves into test specimens for cylindrical waveguide-based ultrasonic transducers. However, to achieve better mode focusing, topographical waveguides with conical profiles were studied. Finite element simulations were used to study wave propagation and transmission into specimen samples using such “transmission horns.” Fundamental longitudinal mode L(0,1) was generated in cylindrical rods. Results from both finite element simulations and experiments show that a 50-deg conical transition profile help achieve better transmission and beam directionality into the specimen and also better reception of the back wall reflections at the waveguide as compared to a simple cylindrical rod waveguide.

Wear Resistance of Laser Alloyed ZrB2 Coatings on Mild Steel

Borides are promising materials with good wear and corrosion resistance properties. Boride coatings are expected to perform better where wear and corrosion resistances are simultaneously required. Zirconium diboride is an important emerging material for such applications, due to its high hardness, high melting point, good wear resistance and corrosion as well as high temperature oxidation resistance. Special properties of laser beam like beam directionality, high intensity and spatial resolution makes laser alloying a fast and efficient technique for producing improved wear resistance coatings. In the present work, mild steel was laser alloyed with ZrB2, using "two-stage" technique of laser alloying. These coatings after characterization by optical microscopy, SEM, EDAX and XRD techniques were tested on a "Pin-on-Disk" machine for determining their wear resistance.