Recent progress of vertical-cavity surface emitting lasers: wavelength engineering and new functions

Abstract

Vertical cavity surface emitting lasers (VCSELs) have been extensively developed and are now key devices in local area networks based on multi-mode optical fibers. Long wavelength VCSELs are currently attracting much interest for use in single-mode fiber metropolitan area and wide area networks. Also, parallel data links including board-to-board interconnections with low threshold VCSEL arrays are also under development. Low threshold single-mode VCSEL arrays will enable us to realize parallel optical interconnects with low power consumption. We have developed highly strained GaInAs/GaAs QW VCSELs emitting at 1.1-1.2 mm band. Excellent temperature characteristics have been realized. We present long wavelength GaInAs VCSELs on GaAs substrates, enabling uncooled operation for high speed data transmission in single-mode fibers. Also, we will discuss a possibility of isolator-free operations of single-mode VCSELs. In addition, we demonstrated a single-mode multiple-wavelength VCSEL array on a patterned GaAs substrate for the wavelength engineering of VCSELs. The maximum lasing span of arrays is over 190 nm. Densely integrated multi-wavelength arrays are presented. Tunable micromachined VCSELs are also attracting much interest for WDM networking, because micromachined tunable VCSELs enable wide continuous tuning. We proposed and demonstrated a micromachined tunable vertical cavity with a strain control layer, which gives us novel functions including temperature insensitive operation, thermal wavelength tuning, and so on. We also propose and demonstrate injection-locked VCSELs for all-optical signal processing. Some results on optical inverters, optical bistable devices and optical regenerators will be reported. Toward other applications including optical storages and sensing, we will describe metal nano-aperture VCSELs for near-field optics.