We report on vertical cavity surface emitting lasers (VCSELs) having a -3dB modulation bandwidth above 30 GHz and a narrow spectrum down to single mode (SM) operation. The 850 nm and 910 nm SM VCSELs in combination with the IN5612 VCSEL driver from Inphi Corporation allowed to reach 106 Gb/s PAM4 with the TDECQ values of only 1.5 dB. For the multimode VCSELs, TDECQ of ~2.6 dB were achieved in combination with the same driver chip. VCSELs with the reduced spectral width allow to cover transmission distance over multimode fiber reaching 1.0-2.5 km at 50 Gbaud. Furthermore, reduction of the aperture size to a certain limit allows to reach ultimate modulation bandwidths at the same current density as applied in the large aperture VCSELs but at lower total currents and thus much lower current-induced overheating. The latter enables a significant improvement in the reliability of the devices and stimulates further research in novel types of VCSEL-based devices.
In this paper, we perform a comparison of three modulation formats: NRZ, duo binary and DMT in combination with the state of the art 850 and 910nm VCSELs for their application in short reach high speed optical links. The system for NRZ and DB utilizes feasible for deployment equalization including a 9-tap finite impulse response filter and raised cosine filtering in the transmitter and a 7-tap UI-spaced feed forward equalizer in the receiver. The 100 Gbit/s net link with DB modulation can be realized without applying receiver equalization. For DMT the highest gross data rate of 224 Gbit/s/lambda is achieved.
New applications in sensing, automotive and on-board applications require vertical-cavity surface-emitting lasers (VCSELs) operating at high data rates up to very high ambient temperatures. We study temperature stability of the 850 nm Quantum-Dot (QD) VCSELs and benchmark them to Quantum-Well (QW) VCSELs of similar design.
QD VCSELs enable extension of the temperature stability and demonstrate threshold currents below 1 mA for operation range from 30°C to 200°C. The role of gain to cavity detuning is discussed in details. 25 Gbit/s NRZ multi-mode fiber transmission with QD VCSELs is realized at temperatures up to 180°C. Pulsed operation of QD VCSELs with 8 μm oxide aperture diameter is studied at temperatures from 30°C to 125°C and 1 W peak power is realized on 100 ns pulses at room temperature.
We report high-frequency polarization self‐modulation (PSM) in high speed vertical-cavity surface emitting lasers (VCSELs) connected to the stress-induced birefringence in oxide-confined aperture VCSELs. Polarization oscillations up to 45 GHz were captured. We analyze the far and the near field of the device and show how the fiber-coupling conditions induce optical feedback, affect emission properties of the device and influence the polarization switching phenomenon. In conditions where the PSM was suppressed, we demonstrate NRZ high-speed multi-mode fiber data transmission up to 90 Gbit/s.