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We use optical, thermal, and electrical simulation to evaluate the effects of using varying amounts of undercut etch on wavelength-scale and subwavelength metal-clad semiconductor nanolasers (MCSELs). We find that as MCSEL diameter decreases, the optical performance becomes more sensitive to slight amounts of sidewall tilt. A modest amount of undercut (25%) dramatically improves the optical performance, reducing modal threshold gain to 100 cm-1 or less for lasers with core radius of 225, 550, or 775 nm, even in the presence of significant sidewall tilt (20° gain sidewall or ±8° pedestal sidewall tilt). Finally, we examine the effects of the increased undercut on nanolaser thermal performance and find that the increased resistive heating is insignificant near threshold, even for subwavelength nanolasers. [ABSTRACT FROM AUTHOR]

We analyze amorphous Al2O3 (α-Al2O3) for use as a thick thermally conductive shield in metallo-dielectric semiconductor nanolasers, and show that the use of α-Al2O3 allows a laser to efficiently dissipate heat through its shield. This new mechanism for thermal management leads to a significantly lower operating temperature within the laser, compared with lasers with less thermally conductive shields, such as SiO2. We implement the shield in a continuous wave electrically pumped cavity, and analyze its experimental performance by jointly investigating its optical, electrical, thermal, and material gain properties. Our analysis shows that the primary obstacle to room temperature lasing was the device's high threshold gain. At the high pump levels required to achieve the gain threshold, particularly at room temperature, the gain spectrum broadened and shifted, leading to detrimental mode competition. Further simulations predict that an increase in the pedestal undercut depth should enable room temperature lasing in a device with the same footprint and gain volume. Through the integrated treatment of various physical effects, this analysis shows the promise of α-Al2O3 for nanolaser thermal management, and enables better understanding of nanolaser behavior, as well as more informed design of reliable nanolasers. [ABSTRACT FROM AUTHOR]

We demonstrate an optically pumped hybrid III-V/Si distributed feedback laser with a small footprint, using sidewall modulated Bragg gratings for optical feedback. Our approach provides high overlap between lasing mode and gain medium and may enable hybrid lasers with improved efficiency, reduced threshold, and minimal size. We fabricate the structure using plasma-assisted wafer bonding, followed by self-aligned lithography and etching. The latter allows us to avoid alignment errors. This approach is a promising avenue toward ultracompact, energy efficient, and scalable monolithically integrated photonic circuits. [ABSTRACT FROM AUTHOR]

The article focuses on chances of increase of perceptual experiences in mammals from patterns of neural circuit activity in cerebral cortex and mentions electrical micro stimulation has been reported to visual percepts such as patterns, motions and colors. Topics discussed incldue technological advances that together enable writing neural activity, approaches of mapping of cell numbers, network dynamics and layers and use of sequence based phylogeny.