High-contrast gratings for WDM VCSEL arrays
Conference poster, 2014

Vertical-cavity surface-emitting lasers (VCSELs) have become the workhorse of short-reach optical interconnects in datacenters and supercomputers. The last few years have seen an impressive increase in VCSEL modulation bandwidth, enabling record-high single-channel data rates exceeding 60 Gbit/s [1]. In addition to higher single-channel rates, interconnect capacity may be enhanced by employing multiplexing techniques such coarse wavelength division multiplexing (WDM). WDM VCSEL arrays can be designed using a high-contrast grating (HCG) as top mirror instead of a distributed Bragg reflector (DBR) [2]. The HCG consists of a subwavelength grating of high refractive index material (GaAs) surrounded by low refractive index material (air), see figure 1. The result is a thin, broad-band and highly reflective mirror. The reflection from the HCG has a varying phase depending on grating geometry. This can be used to set the HCG-VCSEL wavelength in a post-growth process by fabricating gratings with different period and duty-cycle. A first proof of concept has been realized and HCG-VCSELs showing resonances covering a span exceeding 20 nm have been demonstrated. Figure 1: Top: schematic figure of HCG-VCSEL array. Left: Top and cross-sectional SEM image of HCG. Right: Simulated and experimental HCG-VCSEL resonance wavelength for different duty cycles and periods (p) measured by electroluminescence. References [1] D. Kuchta et al., “64Gb/s Transmission over 57m MMF using an NRZ Modulated 850nm VCSEL,” OFC 2014 [2] V. Karagodsky et al., “Monolithically integrated multi-wavelength VCSEL arrays using high-contrast gratings,” Opt. Express, 18(2), 2010

VCSEL

optical interconnect

WDM

HCG

high-contrast grating

Author

Erik Haglund

Chalmers, Microtechnology and Nanoscience (MC2), Photonics

Johan Gustavsson

Chalmers, Microtechnology and Nanoscience (MC2), Photonics

Åsa Haglund

Chalmers, Microtechnology and Nanoscience (MC2), Photonics

Jörgen Bengtsson

Chalmers, Microtechnology and Nanoscience (MC2), Photonics

Anders Larsson

Chalmers, Microtechnology and Nanoscience (MC2), Photonics

Optics & Photonics in Sweden, 11-12 Nov. 2014, Göteborg

Areas of Advance

Information and Communication Technology

Nanoscience and Nanotechnology (2010-2017)

Subject Categories

Telecommunications

Nano Technology

Infrastructure

Nanofabrication Laboratory

More information

Created

10/7/2017