Vertical cavity surface emitting laser based optoelectronic asynchronous transfer mode switch

Abstract

Large broadband asynchronous transfer mode (ATM) switching nodes require novel hardware solutions that could benefit from the inclusion of optical interconnect technology, since electronic solutions are limited by pin out and by the capacitance/inductance of the interconnections. We propose, analyze and demonstrate a new three stage free space optical switch that utilizes vertical cavity surface emitting lasers (VCSELs) for the optical interconnections, a liquid crystal spatial light modulator (SLM) as a reconfigurable shutter and relatively simple optics for fan out and fan in. A custom complementary metal oxide semiconductor (CMOS) chip is required to introduce a time delay in the optical bit stream and to drive the VCSELs. Analysis shows that the switch should be scalable to 1024ϫ1024, which would require 2048 ϳ2 mW VCSELs.

InP-based wavelength tunable vertical cavity surface emitting laser structures

“…Such high reflectivity values can be obtained if one uses DBRs consisting of a high number of 1/4-λ pairs alternating two materials of low and high refractive index. The detailed theory of Bragg mirrors used in VCSEL structures is beyond the scope of this paper, and is presented in many books and references [1][2][3]24].…”

“…One of the first approaches consisted in p-doping and n-doping the top and bottom mirror, respectively, and localizing current injection with ion implantation [1,9]. However, highly doped mirrors, especially p-doped mirrors, present higher optical losses than undoped mirrors, mainly due to free carrier absorption [1][2][3], which reduce the effective mirror reflectivity. Also p-doped mirrors often present rather high resistivity due to the lower mobility in p-doped materials.…”

“…VCSELs are Fabry-Pérot (F-P) type lasers that are intrinsically single-mode and present a very high mode selectivity, due to the very short cavity length and large longitudinal mode spacing. Moreover, the small active volume of a VCSEL enables it to operate at sub-mA laser threshold currents [1][2][3].…”