Femtosecond Pulse Pickers Pismo Questions and Answers

Pismo Pulse Pickers brochure - Pismo 8-1-1 manual - Del Mar Photonics

> (1) Does the unit include the two polarizers and the associated optical mounts, just like the picture shown in the brochure?

The Pulse Picker system include two Glan prisms with mounts, Pockels Cell based on DKDP crystal, control and synchronization unit, fiber and cables.

> (2) What is the optical aperture of this device? The beam size of our laser output is about 2 cm. Is it large enough to let the beam  through without clipping?

Standard clear aperture of Pockels Cell is 5 mm in diameter, but we can made DKDP crystal with 9 mm clear aperture. The 2 cm beam size is very large for Pismo. You will need to reduce beam diameter using mirror telescope, for example.

> (3) What is the damage threshold of this device? Will this device cause serious dispersion problem to our 100-fs laser pulses?

The damage threshold of optical components is enough for working with your source (energy - 3 mJ/pulse, duration - 100 fs, BUT beam diameter - 8 mm). After Pulse Picker system the pulse will be chirped and has duration about 110-120 fs. But you can compensate this chirp increasing the distance between gratings in compressor of your laser system.

> (4) Since our laser wavelength is at 800 nm with a spectral width about 15 nm, what is the operating voltage for us to choose?

The half-wave voltage at 800 nm is about 8 kV for DKDP crystal.

> (5) Based on the standard model provided in your e-mail, it seems that either Pismo 55/1 or Pismo 88/1 is suitable to our applications. Both
> models provides the ability to vary the output frequency from 1 Hz to 1 kHz and variable output pulse duration from 10 to 1250 ns. Of
> course, the operating voltage is dependent on our wavelength. Please help me to identify the right model.

You need the Pismo 8/1 pulse picker. This is model with HV shutter that generate the HV pulse with parameters as following: amplitude -
5-9 kV (adjustable); duration - 10 ns at level 10% of maximum (fixed); repetition rate - 0-1 kHz (adjustable). This is our standard model for single pulse selection with repetition rate up to 1 kHz from femtosecond pulse train (1-80 MHz) and for improvement of contrast ratio after regenerative amplifiers. The Pismo 88/1 is more expensive system. And if you will use pulse picker only for lower repetition rate and for contrast ratio improvement you don't need variable HV pulse duration.
The manual for Pismo 8/1 is attached.
Feel free to ask any questions I would be pleased to to give you a detailed answer.

Regards,
Sergey Tenyakov

Answers was prepared by Project Leader on Amplified Femtosecond Ti:Sapphire Systems Sergey Tenyakov

Complete list of standard Pismo Pulse Pickers:

Components of a standard pulse picker: 1) Pockels cell 2) Control and supply unit 3) Glan prism 4) Glan prism mount 5) Mirror mount 6) Mirror 7) Quarter-wave plate 8) Fiber 9) Fiber holder 10) AC power cord 11) Connection cable 12) Tube (6 m)

Pismo 88/1 Questions and Answers

> I choose the model 88/1, because it will provide us more freedom.
 

We use the BBO crystals in the Pismo 88/1 because its have very low piezoelectric ringing. But maximum clear aperture of BBO that we offer is 4 mm in diameter. This size is small for usage this crystal with 3mJ/100 fs pulses. Certainly we can offer you the Pismo 88/1 pulse picker with DKDP crystal with 9 mm clear aperture but in this case you will have ringing after selected pulses. This effect is important if you will use pulse picker for selecting 20-100 pulses from femtotrain of oscillator (see, for example, picture in attached file). If you will use pulse picker after 1kHz amplifier this effect is negligible. Pismo 8/1 will be work fine with Spitfire (some our customers use this model with Spectra-Physics amplifiers for improvement ns-contrast ratio). Pismo 88/1 is more expensive then Pismo8/1.

Questions about pulse picker for 1550 nm

>(1) Which Pockels crystal type will be suitable for 1550nm? Will it be AR coated for this wavelength?

DKDP crystals, ARC 1500-1600 nm.
 

>(2) Are polarising optics before and after the Pockels cell included in this system?
Yes.
Transmission loses:
DKDP crystal - ~10 %
Glan prism - 8% x 2 = 16 %
Total transmission of the pulse picker system is 70-75%.

Contrast - >1:3000.
Repetition rate - 500 Hz - 25 kHz.
Clear aperture - diameter 5 mm (please, inform if the more aperture will be needed).
Optical scheme - quarter-wave (see manual, l/4 setup).

>(3) Will it be possible to optically trigger the Pockels cell with a sample of the pulse train at 4 MHz?

Yes.

> Otherwise if we need to use our own detector, will it be possible to trigger using the detector output?

Yes, it's possible. But I think, that the most simple variant is to use fiber coupled detector built in Control Unit . ~50 pJ (maximum value) of
pulse energy is needed for stable device operation at repetition rate ~ 70-100 MHz, and <5 mW of average power for 80 MHz repetition rate.

>(4) Is water cooling required for the Pismo unit?

If you work with a repetition rate more than 10 kHz, it is important to chill the Pockels cell (using tube with 6mm outer diameter) with water flow
~ 3 liter/min.

For additional information please review a manual for 25 kHz pulse picker system for 800, 1064 and 1550 nm.

 

Del Mar Photonics