Long-Wavelength High-Contrast Grating Vertical-Cavity Surface-Emitting Laser

Abstract

A novel long-wavelength vertical-cavity surface-emitting laser (VCSEL) structure based on a subwavelength high-contrast grating (HCG) as the output mirror has been realized. By design, these devices are highly polarization stable, are single mode at large apertures, and solve the VCSEL-mirror problem at long wavelengths in an elegant way. With cost-effective mass fabrication in mind, the top HCG reflector consists of amorphous silicon on isolator (amorphous silica). The single-mode laser emission is tailored to be around 1320-nm wavelength, targeting applications in high-speed optical data transmission, particularly those for passive optical networks. We report single-mode emission for devices with apertures as large as 11 m operating in continuous wave with output powers in excess of 0.4 mW. Pulsed operation with output powers up to 4 mW at room temperature is demonstrated as well. This is the first electrically pumped VCSEL structure realized in this wavelength regime utilizing an HCG mirror.

High-contrast gratings for integrated optoelectronics

“…A single-layer ultra-thin HCG with broadband high reflectivity for surface-normal incidence was first proposed with numerical simulation [6], followed by experimental demonstration of HCG having reflectivity >98.5% over a wavelength span of Δλ/λ>35% [7]. The HCG is subsequently incorporated as the top mirror in vertical cavity surface emitting lasers (VCSELs) emitting at 850 nm, 980 nm, 1330 nm and 1550 nm wavelength regimes, replacing traditional multi-layer distributed Bragg reflectors (DBR) [17][18][19][20][21][22][23][24][25][26][27][28][29][30]. This HCG top mirror is naturally a microelectromechanical structure (MEMS), and can be electrostatically actuated.…”

State-of-the-art and perspectives for long-wavelength high speed VCSELs

“…Despite polarization-stable operation, future efforts will aim at the improvement of this property by the implementation of high-contrast-gratings as an alternative top-mirror, yielding inherently single-mode and polarization-stable devices with larger active diameters and, therefore, higher output powers [2,11].…”

Air-suspended TiO2-based HCG reflectors for visible spectral range

“…In these experiments, the HCG structures have either been applied as a part of the top reflector, in combination with a couple of DBR pairs, 2,3,4 or as the one and only part of it, fully substituting the top DBR. 5,6 One should also mention an optically pumped VCSEL using two HCGs as the top and the bottom reflectors, which proves the concept of DBR-free VCSELs. 7 In the GaN-based material system, the HCG reflectors are of particular interest since they may potentially solve some of the key challenges regarding VCSELs emitting in the visible.…”