Sub-Picosecond Pulse Generation using Fast Saturable Absorption in AlGaInAs/InP Quantum Wells
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Transcript of Sub-Picosecond Pulse Generation using Fast Saturable Absorption in AlGaInAs/InP Quantum Wells
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