InGaAs/InGaAsP Quantum-Well Engineering for Multiple Regrowth MOVPE Process
- PDF / 187,761 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 50 Downloads / 210 Views
0891-EE03-09.1
InGaAs/InGaAsP Quantum-Well Engineering for Multiple Regrowth MOVPE Process Hans-Joerg Lohe1, Emilio Gini2, Riccardo Scollo1, Franck Robin1 and Heinz Jaeckel1 1 Electronics Laboratory, ETH Zurich, Gloriastr. 35, CH-8092 Zurich 2 FIRST Center for Micro and Nano Science, ETH Zurich, CH-8093 Zurich ABSTRACT For the heterogeneous integration of several layer structures for absorber, gain and passive waveguide sections in a monolithically-integrated mode locked laser diode, the bandgap of the absorber section has to be matched to the emission wavelength of the gain section. Because of the use of a multiple regrowth process for optical butt-coupling, the first grown multiple quantum-well gain material undergoes a quantum-well intermixing process, resulting in a blue shift of the emitting optical wavelength. Experimental results show, that the blue shift is dependent on the process details and cannot be investigated by simple thermal cycling of unprocessed quantum well-structures. With the introduction of an effective quantum-well width computed from the emission wavelength we found a linear relationship between the effective quantum well width shrinkage and the cumulated regrowth heating time of 8.3Å/h at a growth temperature of 630°C. Therefore knowing the cumulated regrowth time for a laser fabrication, we could successfully design the initial quantum well thickness that yields the targeted emitting wavelength and excellent matching to the absorber bandedge.
INTRODUCTION Mode-locked laser diodes (MLLDs) are attractive optical pulse sources for miscellaneous applications for optical communication networks, THz sources or for clock distribution [1]. To use MLLDs as a pulse source in Tbit/s optical networks, a pulse duration below 1 ps is required. So far this pulse width has only been demonstrated for MLLDs at very high repetition rates beyond the bandwidth of electronic microwave sources [1]. Thus these lasers cannot be locked to an electronic clock. To achieve pulses with sub-pico-second duration in a MLLD with repetition rate of 10-40 GHz simulations show [1,2] that an absorber material with a recovery time constant faster than that achieved in a reverse-biased amplifier section is needed. We have proposed and demonstrated the use of a so-called uni-travelling-carrier structure (UTC) [2,3]. The optical active layer of the UTC-absorber is p-doped and therefore the absorber recovery time is no longer limited by slow hole diffusion but responds with the femto-second dielectric relaxation time constant while the electrons drift-diffuse from the absorbing layer into a collecting layer. Pump-probe measurements show absorption recovery times below one pico-second for UTC absorbers [7]. For MLLDs the monolithic integration of this new absorber structure together with a multiple quantum well (MQW) active (gain) structure and a passive waveguide structure is required. Up to now a electronically isolated reverse-biased active section was used as absorber. For this task we use a butt-coupling process as described
Data Loading...
