Novel concepts for ultrahigh-speed quantum-dot VCSELs and edge-emitters

Abstract

Advanced types of QD media allow an ultrahigh modal gain, avoid temperature depletion and gain saturation effects, when used in high-speed quantum dot (QD) vertical-cavity surface-emitting lasers (VCSELs). An anti-guiding VCSEL design reduces gain depletion and radiative leakage, caused by parasitic whispering gallery VCSEL modes. Temperature robustness up to 100°C for 0.96-1.25 m range devices is realized in the continuous wave (cw) regime. An open eye 20 Gb/s operation with bit error rates better than 10-12 has been achieved in a temperature range 25-85°C without current adjustment. A different approach for ultrahigh-speed operation is based on a combination of the VCSEL section, operating in the CW mode with an additional section of the device, which is electrooptically modulated under a reverse bias. The tuning of a resonance wavelength of the second section, caused by the electrooptic effect, affects the transmission of the system. The second cavity mode, resonant to the VCSEL mode, or the stopband edge of the second Bragg reflector can be used for intensity modulation. The approach enables ultrahigh speed signal modulation. 60GHz electrical and 35GHz optical (limited by the photodetector response) bandwidths are realized

Modulation and thermal properties of tunnel-coupled InAs QD 1.13μm VCSELs

“…It was found that the maximum temperature for lasing in our tunnel QDs-QW VCSELs is more than 140 o C. The highest lasing temperature of 150 o C was measured on another device (not shown on Figure 6). The light power reduces by about 50% only at 80 o C, the threshold current increases significantly at temperatures higher than 100 o C. The temperature robustness demonstrated in our VCSELs is comparable to and at some points exceeds characteristics presented by Ledentsov et al [8].…”

“…We measured the temperature stability of our 3x (QWon-QDs) tunnel active media to compare with QDbased media [8] in VCSELs. Figure 6 shows the lightcurrent characteristics at various temperatures from -12 o C to + 140 o C of our 9x9 µm 2 tunnel QDs-QW VCSEL.…”

“…QD-based VCSELs are predicted to have faster direct modulation response and better thermal stability as compared to QW VCSELs. Nevertheless, these advantages were only partially realized in 0.98µm QD VCSELs [7], and modulation bandwidth and thermal stability in the more interesting longwavelength (around 1.3µm) QD VCSELs are still far beyond expectations [6,8].…”

“…There are a variety of advances of QD active medium compared to the quantum well (QW) medium such as ultralow threshold current density [1, 2] (including an important 1.3µm telecommunication wavelength region), high thermal stability [3], and high-speed modulation [4,5]. Recently, a high gain multi-layer QD (MQD) medium in vertical cavity surface emitting lasers (VCSELs) with doped distributed Bragg reflectors (DBRs) was successfully demonstrated [6,7,8,9].…”

High frequency resonance-free loss modulation in a duo-cavity VCSEL

“…Integrated intracavity electrooptical and electroabsorption modulator based devices were attempted as an alternative to current modulated devices due to the increase of bandwidth and lowering of chirp that could be offered [8][9][10][11] but with limited success. It has really been the introduction of a duo-cavity architecture 7,12,13 that drastically improved bandwidth limits. Modulation of the device output in these cases was done by change of the field distribution inside the dual cavity device 12 , or by use of a variable resonance detuning to modulate top cavity transparency 7 .…”