We present experimental results on 40 Gb/s large-signal modulation performance of 1.31μm monolithic integrated laser-modulator in the InGaAlAs/InP material system, exploiting the gain and absorption properties of an identical multiple quantum well (MQW) active layer. In continuous wave operation, at 15°C, the devices achieved threshold currents < 28 mA, fiber coupled optical power levels up to +0.4 dBm. The measured small-signal modulation bandwidth was about 32 GHz. An air-cavity based Fabry-Perot interferometer has been realized to characterize the spectral chirp of the integrated structures in the time domain up to 40 Gb/s.
We present first experimental results of the successful transfer of our monolithic integrated double-stack multi quantum well laser-modulator approach from the traditional InGaAsP/InP to the more promising InGaAlAs/InP material system. In continuous wave operation at room temperature, the devices achieved threshold currents of <21 mA, fiber coupled optical power levels up to 570 μW and static extinction ratios in the range of 15 dB/V. The measured small-signal modulation bandwidth of about 10 GHz is capacitance limited due to a conservative device layout.
We compare various approaches aiming at large-area high-power single-mode oxidized VCSELs. Stable and reproducible single-mode emission with SMSR (side-mode suppression ratio) greater than 30dB and output powers well above 5mW are reported for the long monolithic cavity and self-aligned shallow surface etching approaches, both of which are suitable for commercial production. Additionally, Photonic Crystal Surface-Emitting Lasers (PCSELs) are introduced, which enable advanced mode control by novel transverse optical guiding techniques.
We present top surface emitting two- and three-stage bipolar
cascade vertical cavity surface emitting lasers (VCSELs) for
continuous wave (cw) operation at room temperature. The results
are compared with a conventional VCSEL grown under identical
growth conditions for reference. The improvement of both threshold
current density and differential quantum efficiency can be clearly
shown in structures with unchanged top mirror reflectivities (19
pairs). To further increase the differential quantum efficiency, a
device with only 14 p-type top mirror pairs is fabricated,
yielding an efficiency of 130% for cw room temperature
operation. From noise measurements, we extract a modulation
efficiency of 8.2 GHz/sqrt(mA}, indicating favorable dynamic
properties of these VCSEL.
Oxide-confined vertical cavity surface-emitting laser diodes (VCSELs) are fabricated for applications in chip-level optical interconnects. 980 nm wavelength devices in arrays with 4 by 8 elements are investigated. Threshold voltages of 1.5 V and operation voltages below 2V of submilliamp threshold current lasers are fully comparable to 3.3 V CMOS technology. Modulation bandwidths of 9.5 GHz at 1.8 mA laser current with a modulation current efficiency factor of 10 GHz/(root)mA is demonstrated for 3 micrometers diameter VCSELs. No error floors are observed down to bit error rates of 10-11 at 12.5 Gb/s data transmission. VCSEL based top illuminated resonant cavity enhanced photodetectors show peak efficiencies of 50 percent combined with full spectral half-widths of 5 nm.