Sub-Picosecond Pulse Generation using Fast Saturable Absorption inAlGaInAs/InP Quantum WellsM. 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

10GHz Pulses 2.5ps

CW Tunable Laser

Polarisation Controller

BPF

DCA Oscilloscope(85 GHz BW)

50um long cavity3.5um deep etched side wallsR1 = 30% (etched facet),R2 = 2% (10° tilted facet)5 InAlGaAs quantum wells EDFA

EDFA

V

+

-

R2

R1

λS =1570nm

λP = varied λP

Stark Shift of Reflected Signal

Device reflectivity at different VSA

Recovery Times in AlGaInAs/InP MQWs

(Input pulse recovery ~ 3ps)

Measured τa verses reverse bias Voltage

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 τa verses reverse bias Voltage

Mode Locking in InAlGaAs/InP

n-InP substrate

MQW-GRINSCH

AlGaInAs dry etch stop layer

Ti/Pt/Au

SiO2

Total Length = 1070 umAbsorber Length = 20um50:1 Ratio

Mode Locking Results

Autocorrelation Trace

IGain = 40mAVSA = -3V

Mode Locking Results

Pulse Width Measurement

Δt = 600 fsΔt = 848 fsΔt = 777 fs

Mode Locking Results

LI plots at different VSA

Optical Spectrum and RF Spectrum

Optical Spectrum RF 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.)

Acknowledgements