Mode Locking

1
Mode Locking
Multimode lasing
Random phases
2
Locked phases
Field envelope
Period repetition rate
Equal amplitudes and phases
3
Mode-locked pulse
Speak
Peak power
Minima
?p
Pulse energy
4
Theory of Mode Locking
Homogeneous broadening
5
Theory of Mode Locking
6
Pulse length
Number of lasing modes
7
Side mode generation
For power
8
Mode locking by phase modulation
9
Chirped pulse
10
Group velocity dispersion
What if nn(?)?
11
GVD implications
12
Pulse distortion
Power
Time
13
Passively mode-locked NdYLF lasers
SESAM Semiconductor Saturable Absorber Mirror
14
Passive Mode-locking
Pulse gets shorter
15
Pulse length in passive mode-locking
In active mode-locking
Passive mode-locking leads to shorter pulses
16
Development of pulses
495 ps
2 ps
N2000
N1000
Signal Power (a.u.)
N500
N100
1400
0
200
400
600
800
1000
1200
Time (ps)
17
Passively Mode-locked fiber laser
18
Kerr Lens mode locking
High Loss
Low Loss
19
Kerr Lens Mode Locked Femtosecond laser
Rep rate 70-140MHz
Pulse Length lt100fs
20
Passive mode-locking using nonlinear
polarization rotation