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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. Contents. Absorber Dynamics – Carrier lifetimes, pulse widths.
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Sub-Picosecond Pulse Generation using Fast Saturable Absorption inAlGaInAs/InP Quantum Wells M. Haji, L. Hou, A. E. Kelly, R. G. Green, G. Mezosi, J. Javaloyes, A. C. Bryce, J. M. Arnold
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.
Absorber Dynamics K. A. Williams, M. G. Thompson and I. H. White, New Journal of Physics, 6 (2004) 179.
Loss Recovery Times in AlGaInAs Absorbers Polarisation Controller - 10GHz Pulses 2.5ps R1 V + λS =1570nm R2 EDFA CW Tunable Laser 50um long cavity 3.5um deep etched side walls R1 = 30% (etched facet), R2 = 2% (10° tilted facet) 5 InAlGaAs quantum wells BPF λP λP = varied EDFA DCA Oscilloscope (85 GHz BW)
Stark Shift of Reflected Signal Device reflectivity at different VSA
Recovery Times in AlGaInAs/InP MQWs Measured τa verses reverse bias Voltage (Input pulse recovery ~ 3ps)
Recovery Times in AlGaInAs/InP MQWs Measured τa verses reverse bias Voltage K. Nishimura et al., IEEE J. Select. Top. Quant. Electron., vol. 11, no. 1, pp 278-284 (2005) .
Mode Locking in InAlGaAs/InP Ti/Pt/Au SiO2 AlGaInAs dry etch stop layer MQW-GRINSCH n-InP substrate Total Length = 1070 um Absorber Length = 20um 50:1 Ratio
Mode Locking Results Autocorrelation Trace IGain = 40mA VSA = -3V
Mode Locking Results Pulse Width Measurement Δt = 600 fs Δt = 848 fs Δt = 777 fs
Mode Locking Results LI plots at different VSA
Optical Spectrum and RF Spectrum RF Spectrum Optical Spectrum
Pulse Width Mode locking region and Measured Pulse Widths
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.)