1. Sub-Picosecond Pulse Generation using Fast Saturable Absorption in AlGaInAs/InP Quantum Wells M. Haji, L. Hou, A. E. Kelly, R. G. Green, G. Mezosi, J. Javaloyes, A. C. Bryce, J. M. Arnold

2. Contents Absorber Dynamics – Carrier lifetimes, pulse widths. Absorption recovery times in AlGaInAs/InP quantum wells. Ultrashort pulse generation using a mode locked laser in AlGaInAs/InP quantum wells.

3. Absorber Dynamics K. A. Williams, M. G. Thompson and I. H. White, New Journal of Physics, 6 (2004) 179.

4. Loss Recovery Times in AlGaInAs Absorbers 10GHz Pulses 2.5ps CW Tunable Laser Polarisation Controller BPF DCA Oscilloscope (85 GHz BW) 50um long cavity 3.5um deep etched side walls R1 = 30% (etched facet), R2 = 2% (10 ° tilted facet) 5 InAlGaAs quantum wells EDFA V + - R2 R1 λ S =1570nm λ P = varied λPλP

5. Stark Shift of Reflected Signal Device reflectivity at different V SA

6. Recovery Times in AlGaInAs/InP MQWs (Input pulse recovery ~ 3ps) Measured τ a verses reverse bias Voltage

7. Recovery Times in AlGaInAs/InP MQWs K. Nishimura et al., IEEE J. Select. Top. Quant. Electron., vol. 11, no. 1, pp 278-284 (2005). Measured τ a verses reverse bias Voltage

8. Mode Locking in InAlGaAs/InP n-InP substrate MQW-GRINSCH AlGaInAs dry etch stop layer Ti/Pt/Au SiO 2 Total Length = 1070 um Absorber Length = 20um 50:1 Ratio

9. Mode Locking Results Autocorrelation Trace I Gain = 40mA V SA = -3V

10. Mode Locking Results Pulse Width Measurement Δt = 600 fs Δt = 848 fs Δt = 777 fs

11. Mode Locking Results LI plots at different V SA

12. Optical Spectrum and RF Spectrum Optical Spectrum RF Spectrum

13. Pulse Width Mode locking region and Measured Pulse Widths

14. Conclusions Recovery times below 5ps have been obtained on InAlGaAs/InP MQWs. Able to generate femtosecond pulses using a 40 GHz mode- locked laser. Pulse widths are notably shorter than those generated in P- quaternary MQWs. - 860 fs (Lorentzian pulses) @ 21 GHz. (K. Merghem, et al., 2008, Optics Express, Vol. 16, No. 14, pp10675.)

15. Acknowledgements