Ultrahigh intensity laser System

1
Ultra-high intensity laser System
K-state Light Source Chun Wang
2
Whats a laser?

• Laser Stands for Light Amplification by
  stimulated Emission of Radiation

3

• Laser Oscillator
• To generate light
• Essential elements
• Gain medium atoms with desired energy levels
• Pumping source to excite atoms into higher
  energy levels
• Feedback system
• Laser Amplifier
• To get powerful light
• Essential elements
• Gain medium atoms with desired energy levels
• Pumping source to excite atoms into higher
  energy levels

4
(No Transcript)
5
(No Transcript)
6
How to get High Intensity?

• IP/S W/cm2
• 1. Decrease the beam size
• Dgt 1um
• 2. Increase the power
• Increase pulse energy
• Shorten the pulse duration

7
Why do we build this Amplifier?

• AMO experiment need
• Commercial product
• long pulse duration 50-100fs
• lower pulse energy 1 mJ
• expensive

8
What is CPA?
Schematic of the technique of chirped pulse
amplification.

• The CPA technique takes advantage of the
  fact that very short laser pulses have a large
  bandwidth . Direct amplification of these pulses
  would lead to damage in the amplifying medium. In
  order to avoid this damage, the pulse peak
  intensity must be reduced in the laser. Passing
  pulses through a dispersive delay-line temporally
  stretches them, reducing the peak intensity and
  allowing safe amplification. A conjugate
  delay-line is used after amplification to
  compress the pulses back to their original
  duration.

9
Constitution of laser amplifier

• Oscillator
• Stretcher
• Amplifier
• Compressor

10
Oscillator

• Pulse duration 20fs
• Spectral width 50nm
• Output power (average) 350mW
• Repetition Rates 75 MHz
• Pump power _at_ 532 nm 5W

11
Oscillator
12
Stretcher

• Laser pulse comprises many frequencies,
• different frequencies take different paths,
  and Experience different distances
• the chirped pulse duration is about 120ps.

13
Stretcher
14
(No Transcript)
15
Characterize Chirped Pulse
Chirped Pulse cut by ionizing air
Compressor
Chirped Pulse
Spectrum / Time
Spectrometer
Delay
Compressed Pulse
Chirped Compressed Pulse
16
Cut Chirped Pulse by Laser Scissors
17
Chirp Parameter
18
Chirped-pulse amplifier
Average power 6W Pulse Duration 120ps
19
Amplifier and compressor
20
Compressor

• the amplified (chirped) pulse must be compressed
  to remove the chirp and regain the short pulse in
  time.
• The compressor consists of a pair of gratings.
  It shortens the duration of the pulse by
  typically some 20,000 times, and multiplies its
  peak intensity by the same factor

21
(No Transcript)
22
Results

• Pulse duration 25fs
• Bandwidth 40nm
• Average power 3.3W
• Peak power 1.3x1011
• Pulse energy 3.3mJ

23
(No Transcript)
24
What is new in our laser system?

• Use LN2 to cool the laser Crystal to minimize the
  thermal effect
• Stable
• Spatial Mode
• Use Long Cavity to increase the beam size in
  crystal to increase the damage threshold
• High power 1mJ/pulse 3.3mJ/pulse

25
Where will we go?

• 1. Increase the power to 6W
• 2. Shorten the pulse duration through SPM
• get high power and high intensity
• 3. OPA
• To tune the wavelength to satisfy the demand
  of the AMO Experiment