Kevin J. Knopp

Complete polarization mode control of long-wavelength tunable vertical-cavity surface-emitting lasers over 65-nm tuning, up to 14-mW output power

We experimentally demonstrate a stable polarization mode operation in long-wavelength tunable vertical-cavity surface-emitting lasers over a 65-nm tuning range and the entire output power range (< 14.6 mW) at room temperature. The polarization mode control was achieved by utilizing anisotropic gain properties of quantum wells due to the difference in bond lengths between the constituent atoms at the interfaces combined with uni-axial external strain induced by a stressor. The experiments were conducted to verify this newly proposed polarization control scheme based on the spin flip model (SFM) developed to incorporate the detailed gain properties, cavity standing wave effect, self-heating effect, and strain effect. The experimental results on the tuning characteristics of polarization switching behavior and output powers were reproduced in highly agreeable manner by simulations. The relative importance of the external strain, interfacial strain at quantum wells, and the wavelength dependence of gain anisotropy are also discussed. It is also shown that the fast spin relaxation times for InP-based vertical-cavity surface-emitting lasers (VCSELs) was responsible for the inhibition of elliptic polarization states often observed for GaAs-based VCSELs. The effectiveness of the polarization control scheme was highlighted by the observed high polarization suppression ratio of 34 dB maintained for the entire wavelength and pump power ranges during the reliability testing over 2000 h. The influence of the elliptic polarization state for the optical pump laser was detected which could be explained as a memory effect of the spin-polarized electrons, supporting the validity of the SFM.

C-band tunable 6 mW vertical-cavity surface-emitting lasers

We demonstrate micro-electromechanical vertical-cavity surface-emitting lasers (MEM-VCSELs) that couple >6 mW of power into a single-mode fiber. These devices are continuously tunable across the entire c-band and offer error-free transmission over >500 km of single-mode fiber at OC-48 data rates.

Raman amplification using high-power incoherent semiconductor pump sources

We have demonstrated 7 dB of C-band amplification from a DRA; pumped using novel incoherent high-power (>450 mW) semiconductor sources with a broad spectral bandwidth (>35 nm). The low-frequency RIN of these sources can be suppressed below -140 dB/Hz.