B. Weigl

High-performance oxide-confined GaAs VCSELs

We present GaAs based selectively oxidized VCSELs with record high 57% wallplug efficiencies emitting in the 820-860-nm wavelength regime. Solid source molecular beam epitaxy with carbon as p-type dopant is used for crystal growth. Multimode devices show continuous-wave (CW) output powers up to 42 mW and stable operation from -80/spl deg/C up to +185/spl deg/C. Efficient single-mode output power of some milliwatts is maximized by controlling optical waveguiding that depends on the position of the 30-nm thin oxide aperture. Elliptically shaped current apertures are applied to stabilize output polarization.

Efficient single-mode oxide-confined GaAs VCSEL's emitting in the 850-nm wavelength regime

Single- and multimode vertical-cavity surface-emitting lasers (VCSELs) with three unstrained GaAs quantum wells (QWs) and emission wavelengths around 850 nm have been fabricated using molecular beam epitaxy (MBE) for crystal growth. Wet chemical etching and subsequent selective oxidation are applied for current confinement. The influence of oxide layer position on lateral index guiding is studied in detail in order to increase maximum single-mode output power. A device of 3-/spl mu/m active diameter and reduced index guiding shows maximum single-mode output power of 2.25 mW with a side-mode suppression ratio (SMSR) of more than 30 dB for high-efficiency oxidized VCSELs.

High-power selectively oxidized vertical-cavity surface-emitting lasers

Summary form only given. Vertical-cavity surface-emitting lasers (VCSELs) emitting around 980 nm wavelength are of much interest for short distance, high-data-rate optical interconnects. Recently, VCSELs with record high conversion efficiencies of 50% and record low threshold currents of 9 /spl mu/A have been reported, employing selective oxidation of AlAs for current confinement and MOCVD growth with carbon as p-type dopant. In these small diameter devices, the maximum output power was emitted to a few milliwatts. We have fabricated MBE-grown oxidized VCSELs using beryllium as p-type dopant. Nonheatsinked 25 /spl mu/m active diameter lasers with 82% differential quantum efficiency reach maximum output powers of 47 mW and wallplug efficiencies up to 42%.Summary form only given. We have demonstrated MBE-grown oxidized InGaAs QW VCSELs combining both high output power and high conversion efficiency. Applications for these devices are foreseen in large two-dimensional arrays for optical pump sources.

Spectrally resolved near‐field mode imaging of vertical cavity semiconductor lasers

The transversal mode properties of vertical cavity surface emitting lasers (VCSELs) are studied by spectrally resolved scanning near‐field optical microscopy. In contrast to classical optical microscopy techniques, our method is able to simultaneously decompose lasing transversal modes by their wavelength with lateral superresolution. As the tip‐sample distance is controlled by the well‐established shear‐force detection, additional topographical information showing the surface structure of the laser is provided. Therefore, near‐field spectroscopy allows the detailed analysis of the spatial light distribution emitted by the laser with respect to the current injection contact, making it a promising tool for the characterization and optimization of VCSELs.

Bias-free 1-Gb/s data transmission using top vertical-cavity surface-emitting laser diodes

Slightly elliptically shaped high-performance InGaAs (/spl lambda/=980 mn) oxide-confined, top vertical-cavity surface-emitting lasers (VCSELs) with stable linearly polarized output are used to transmit 1 Gb/s pseudorandom bit sequences with 2/sup 31/-1 wordlength under bias-free current modulation over 1.5 km of graded index multimode fiber. Although a turn-on delay of 400 ps is observed the received power for a bit-error rate of 10/sup -11/ is as low as -27 dBm including 2 dB penalty due to fiber dispersion.

Stable linearly polarized light emission from VCSELs with oxidized elliptical current aperture

Summary form only given. We have fabricated oxidized InGaAs MQW VCSELs with elliptical current aperture. The lasers emit linearly polarized light up to thermal roll over. The polarization extinction ratio of better than 20 dB is also maintained under 2.5 Gbit/s large signal amplitude modulation.

High power top-surface emitting vertical-cavity lasers

Summary form only given. We have fabricated top-emitting VCSELs grown by solid source MBE. Emission wavelength is about 990nm. The optimized p-type Be modulation doped Bragg-reflector consists of 24 pairs of quarter wavelength thick AlGaAs-GaAs layers, the n-Bragg-reflector is built of 30 pairs of AlAs-GaAs layers. The 3 active InGaAs quantum wells are embeded in GaAs barriers. Lateral current confinement is achieved by selective oxidation of a single 30 nm thick AlAs layer just above the active layers.

Highly efficient selectively oxidized GaAs (/spl lambda/=830 nm) vertical-cavity lasers

We have fabricated MBE grown, selectively oxidized multi-mode GaAs QW VCSELs with 730 /spl mu/A threshold, 8.5 mW output power and 40.3% conversion efficiency. Single-mode devices show 1.2 mW output power and better than 30 dB side mode suppression.

High power and high efficiency GaAs based VCSELs

Summary form only given. The realization of optimized vertical-cavity laser diodes with conversion efficiencies over 55% at 850 nm wavelength and top surface emitted output powers in excess of 100 mW in cw and 1.5 W in pulsed operation at 980 nm is reported.

Modal noise in 2.5 Gbit/s data links with oxidized VCSELs

The highest bit rate transmitted to date using VCSELs has been achieved when operating the devices in the transverse single-mode linearly polarized regime. On the other hand it has been shown at 500 Mbit/s that transverse multi-mode InGaAs VCSELs are less sensitive to mode selective loss (MSL) due to their low coherence. In this contribution we study the effect of MSL in graded index multi-mode fiber of 50 /spl mu/m core diameter at 2.5 Gbit/s data rates. We investigate both, transverse single-mode and transverse multi-mode VCSEL transmitters.