B Moller

Optimization of planar Be-doped InGaAs VCSEL's with two-sided output

Threshold current, output power, wall-plug efficiency and operating voltage of epitaxially grown InGaAs-AlGaAs planar vertical-cavity surface-emitting lasers (VCSELs) are strongly influenced by the electrical and optical properties of the p-doped Bragg reflector. Here we study in some detail the dependence of output behavior on the composition, interface grading, and modulation doping of the Be-doped AlGaAs-GaAs Bragg reflector. Using optimized p-doped mirrors VCSELs with low threshold current densities of 300 A/cm/sup 2/, low driving voltages of 1.6 V and high wall-plug efficiencies of 17.6% are obtained. Transverse single-mode emitting devices show a record low emission linewidth of 30 MHz and a linewidth-power product of 2.2 mW/spl middot/MHz.<<ETX>>

Planar proton implanted VCSEL's and fiber-coupled 2-D VCSEL arrays

Efficient planar proton implanted InGaAs-GaAs MQW vertical-cavity surface-emitting laser diodes (VCSELs) and 2-D arrays are fabricated using molecular beam epitaxy and p-type beryllium doping. Using single-step grading and modulation /spl delta/-doping in the p-type AlGaAs-GaAs Bragg reflectors top surface emitting devices with a maximum wall-plug efficiency of 17.6% and a threshold voltage of 1.8 V are demonstrated. Transverse mode behavior is well described in terms of Laguerre-Gaussian functions. Independently addressable 10/spl times/10 arrays of 12 /spl mu/m diameter VCSELs exhibit electrical 3-dB modulation bandwidths up to 6 GHz. Light from the array is simultaneously launched into a 10/spl times/10 multimode fiber bundle with coupling efficiency above 70% applying a simple butt-coupling technique. >

High speed performance of 2-D vertical-cavity laser diode arrays

We have fabricated and tested 10/spl times/10 independently addressable vertical-cavity surface-emitting laser diode arrays. Arrays with 55 /spl mu/m active diameter devices show an average threshold current density of 590 A/cm/sup 2/ and an excellent homogeneity of the output characteristics over the full array size with maximum CW output powers of 12 mW. Broad area laser diodes with active diameters of 75 /spl mu/m reach output powers of 18 mW for CW operation and 180 mW under pulsed conditions. Small-signal modulation bandwidths are beyond 10 and 8 GHz for the 55 and 75 /spl mu/m devices, respectively.<<ETX>>

Proton implanted VCSEL's for 3 Gb/s data links

Transverse single-mode and multimode intensity modulated butt-coupled InGaAs vertical cavity surface emitting lasers (VCSEL)s are investigated as a light source for optical fiber communication systems. Data transmission at 3 Gb/s with a bit error rate (BER) of less than 10/sup -11/ is reported for both 4.3 km of standard fiber, as well as 0.5 km of multimode graded-index fiber, 10-/spl mu/m active diameter single-mode VCSELs are shown to have lower mode competition noise requiring 3 dB and 6 dB less power at the front end receiver at a BER of 10/sup -11/ compared to 19-/spl mu/m and 50-/spl mu/m active diameter devices, respectively. In data transmission with multimode VCSELs, the dispersion penalty is lower than for single-mode sources since the noise at the receiver is mainly determined by transmitter-mode competition noise.<<ETX>>

Linewidth enhancement factor of vertical-cavity surface-emitting laser diodes

The linewidth enhancement factor /spl alpha/ characterizes the performance of semiconductor lasers, such as spectral linewidth broadening for CW operation and wavelength chirping under high-frequency modulation. We have for the first time determined the /spl alpha/ factor of vertical-cavity surface-emitting lasers from the measured linewidth-power product and more precisely from the frequency to amplitude modulation ratio at high-frequency current modulation. Both methods provide the same /spl alpha/ factor of 3.7. The minimum linewidth was as narrow as 70 MHz and the linewidth-power product was 5.4 MHz/spl middot/mW neglecting the residual linewidth.<<ETX>>

6 GHz modulation of fiber coupled VCSEL arrays

Summary form only given. Fiber coupling of independently addressable 4/spl times/8 vertical-cavity top-surface-emitting InGaAs quantum well laser diode arrays with coupling-efficiency above 70% is reported. Individual lasers show maximum output powers of 1.3 mW and electrical 3 dB modulation bandwidths up to 6 GHz.

Vertical Cavity Laser Diodes and Arrays for Efficient Fiber Coupling and High Speed Data Transmission in Optical Interconnects

Vertical cavity laser diodes (VCSELs) form a new class of semiconductor lasers extremely prospective for a wide range of applications, e.g. in parallel fiber links, optical interconnects and cross connects, bar code scanners, compact optical disk systems and laser printers. Parallel fiber busses using VCSEL transmitters have just entered the market. Compared to conventional edge emitting laser diodes VCSELs have distinct advantages like low divergence, astigmatic-free output beams for efficient fiber coupling or dynamic single-mode emission up to 40 Gbit/s data rates under direct modulation. Two-dimensional independently addressable laser diode arrays are easily produced and may be applied for display or monitoring purposes or coupling to fiber bundles. Like light emitting diodes VCSELs are manufactured on wafer scale and testing is also performed directly on-wafer. This is in contrast to edge emitting lasers where cleaving is required and testing is performed after dicing and facet coating which leads to comparatively high fabrication costs. Moreover, mounting and packaging requirements are expected to be much less for VCSELs than for edge emitters.

Optimization of gain and mode field overlap for efficient proton implanted broad area vertical-cavity laser diodes

Overlap of gain and mode profiles in conventional planar proton implanted VCSELs is measured to be in the order of 10%. The resulting low device efficiency is considerably increased if a beam transforming layer is integrated.