U. Fiedler

Top surface-emitting vertical-cavity laser diodes for 10-Gb/s data transmission

Intensity modulated proton-implanted top surface-emitting vertical-cavity InGaAs QW lasers (VCSELs) with a small-signal modulation bandwidth of 12 GHz butt-coupled to multimode fibers are investigated as light source for optical interconnection. At 10-Gb/s pseudorandom data rates the bit-error rate (BER) remains under 10/sup -11/ after transmission over 500 m of graded index multimode fiber. Optimum transmission behavior is achieved for linearly polarized nearly single-mode laser operation with a side-mode suppression of better than 25 dB under modulation. Spectral characterization indicates that linearly polarized single-mode light output is essential for good BER performance.

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>>

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.

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.

2.5 Gbit/s data rate transmission using low threshold GaAs (/spl lambda/=830 nm) VCSELs

In summary, we have investigated 2.5 Gbit/s PRBS data transmission over 500 m graded index fiber using short wavelength (830 nm) VCSEL transmitters. A BER of 10/sup -11/ is obtained for -21.3 dBm received optical power. Higher data rates can be achieved by reducing the parasitic VCSEL capacitance due to the oxidized layer.

High frequency behavior of oxidized single-mode single polarization VCSELs with elliptical current aperture

For extremely high bit rate data transmission, laser sources with dynamically stable linearly polarized single-mode light output are desirable. We have fabricated oxidized VCSELs with elliptical current aperture for stable linearly polarized single-mode light emission and investigated their RF-behavior. The InGaAs-QW VCSEL structure is grown on <100> GaAs substrate. S-parameter and spectral relative intensity noise measurement give consistent results and yield both a K-factor of 0.468 ns equivalent to 19 GHz intrinsic modulation bandwidth.

Hybrid integrated VCSEL-fiber module for efficient mode-locking

We have fabricated a simple VCSEL-fiber module for stable short pulse generation. The hybrid integration of amplifier and external cavity sections avoids the use of gratings or Fabry Perot etalons for frequency filtering and eases mechanical stability problems. The compact device generates 22 ps mode-locked pulses at a repetition rate of 821 MHz and launches the pulse sequence with timing jitter below 1 ps into a butt-coupled output fiber.

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.