Transcript Gain Shaping of Mode Locked Oscillations

Shaping Pulses
Before They are Born
Avi Pe’er
Physics Department and BINA center for nano-technology,
Bar Ilan University
Shai Yefet,
Naaman Amer
Kahn Foundation ,ISF - ₪
FRISNO 11
Outline
Why pulse shaping
 Standard techniques

◦ Mode locked oscillator cavity
◦ Extra-cavity shaping
Intra cavity shaping – why not ?
 Gain shaping concept
 Results
 Conclusions

Pulse Shaping In Optics
Control a pulse shape in time / spectrum
 Coherent quantum control
 Precision spectroscopy using frequency comb

PRL 98, 113004 (2007)

Time domain picture
Label free Fluorescence
microscopy with
Pump
Dump
t
τvib
Stimulated Raman
0 t    0 t   2
0 t 
Science 322, 1857-1860(2008).
rep
Frequency domain picture
Ed  
Dump
E p  
Pump
Standard Mode Locked Cavity (Ti:S)
OC
HR
gain
medium
Pump source
@ 532 nm
Mode competition
(Gain, Loss, Dispersion)
No knob on spectrum
Kerr Lens Mode Locked Cavities
1st stability limit - Telescope
2nd stability limit
Pulse Shaping (Extra-Cavity)
SLM
Phase modulation: Simple, lossless
 Amplitude modulation: Lossy !

Intra Cavity Pulse Shaper ?
OC
HR
gain
medium
Pump source
@ 532 nm
In cavity phase = frequency shift
No phase shaping !
Amplitude shaping = loss shaping
Mode competition !
Two Colors – Impossible !
Two-Colors so far ?

Active locking of independent lasers
Opt. Lett. 27, 312 (2002)

Passive Locking – shared Kerr medium
Opt. Lett. 29, 629 (2004)
OPO – signal and idler
 Synchronously pumped OPOs
 Time lens technique - Active modulation of
a CW laser

Optics Express 18, 24019 (2010)
Gain Shaping
OC
HR
1st gain
medium
Beam
splitter
2nd gain
medium
Spatial
shaper
Pump source @
532 nm
Spatial shape of pump = Spectral shape of gain
Power (a.u.)
100
Results I
80
60
40
20
0
680
745
765
840
Wavelength (nm)
930
Results II
Conclusions
Multi lobed spectra in mode locked
oscillators are important for many applications
 No easy solution so far – Synchronization of
independent sources
 Gain shaping allows for arbitrary control of
the oscillation spectrum.
