Del Mar Photonics

>I am interested in your pulse picker system (stand alone) for use with a Spectra Physics Tsunami fs laser with 82 MHz rep rate and output wavelength ~800 nm. Could you please >send technical specifications (e.g. wavelength range, gate pulse width, extinction ratio etc) and price quote.
 

Pulse pickers

The pulse picker consists of the pockels cell, high voltage driver, synchronization and delay generator. It is suitable for single pulse selection from train of femtosecond or picosecond pulses. Also the device is used for pulse slicing in order to increase contrast.

External high-frequency or optical reference High-voltage pulse with adjustable delay High-voltage pulse with adjustable amplitude Two additional sync channels High contrast Low jitter Applications - Pulse selection - Pulse Slicing - Q-switching

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

* - please specify with order
Models Pismo 8/2 and Pismo 12/2 incorporate one Pockels cell and produce two high voltage pulses.
Customer requested high voltage generators up to 50kV are also available.

Pulse shapes from Pismo pulse picker

Del Mar Photonics produce pulse picker systems with repetition rate up to 100 kHz.

We can offer you our standard devices for picking single pulse from femtosecond pulse train with following specification:

New models:

1. Pismo OG8-50-1
Pockels cell crystal: DKDP, 6x6x16 mm3, ARC 700-900 nm (clear aperture – 5 mm), other aperture on request
HV pulse amplitude: up to 8 kV (HV pulse has the amplitude ~8kV with duration 10 ns at level 10% of maximum)
Repetition rate: 1 Hz – 50 kHz
RF source: 30-120 MHz
RF input: optical (internal fiber coupled photodetector with 3m length plastic fiber)
System transmission: >85%
Contrast ratio: >1:1000
Cooling requirements: water flow ~3 l/min


2. Pismo OG8-100-1
Pockels cell crystal: BBO, 4x4x20 mm3, ARC 700-900 nm (clear aperture – 3.5 mm), other aperture on request
HV pulse amplitude: up to 8 kV (HV pulse has the amplitude ~8kV with duration 10 ns at level 10% of maximum)
Repetition rate: 1 Hz – 100 kHz
RF source: 30-120 MHz
RF input: optical (internal fiber coupled photodetector with 3m length plastic fiber)
System transmission: >85%
Contrast ratio: >1:1000
Cooling requirements: water flow ~3 l/min

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

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 Pulse Pickers brochure - Pismo 8-1 manual

Pismo OG8/1-10 pulse picker system Q&A

To the synchronization of Pockels cell with optical pulses. I want to assure, I understand it well. The RF external or Optical input serves for precise synchronization with optical pulses. The External trigger selects when the HV electrical pulse is generated and which pulse from optical train is transmitted.

>>>> Yes, you are correct.

Using delay channels I can delay e.g. external trigger. Am I right? Or is the usage of these channels different?

>>>> Moreover, the device has 4 independent delay channels, and only one of them is used for starting the HV generator. The three other delay channels can be used, for example, for starting other Pockels cells, oscilloscope, amplifier pump laser, streak-cameras etc.

You wrote, it is possible to use RF external. Is there some limitation on pulse duration? Usually pulses from photodetector are very short about 1 ns. Is it enough?

>>>> It is enough if the amplitude of the pulses on the 50 ohm input of the oscilloscope is more than 200 mV.

Pismo OG8 uses DKDP crystal. This crystal is hygroscopic. How is it protected against air humidity?

 >>>> Yes, we are aware of this. The faces of the crystal have special protective coating, and  side surfaces are covered with moisture-resistant coating.

You sent me information about pulse duration. These specifications concerns electrical pulse from High-Voltage generator, isn’t it. How corresponds these times with optical pulse? Are the same? (Assuming I would have CW light).

>>> They are practically the same.

How is defined contrast ratio? 

>>> The contrast is the ratio of the picked pulse intensity to the intensity of neighboring pulses (that are not selected).

How changes the contrast if I would do not compare the Pockels cell open and closed, but I would interest for contrast for voltage at 90% of maximum? Or how changes the contrast during the electrical pulse evolution?

>>>> The contrast ratio does not change while changing the amplitude of the HV pulse in the range of 6-9 kV.

What parameters can you control using Control unit or LabView drivers? 

>>>> Please see the manual.

You wrote the part of signal is used for proper synchronization. How do I synchronize the pulses with e.g. single shot pulses or 10 Hz pulses.

>>>> You can use external synchronization source by feeding the trigger signal to the BNC input of the control unit. In this case the control unit finds the femtosecond pulse closest to the trigger pulse front. It also generates 4 delay channels that are solidly fixed to the femtosecond pulse train.

Can you adjust the delay between optical end electrical pulse? In what ranges, can you adjust it?

 >>>> You can adjust it in the range of 0 to 5 us with step 20 ps. Or you can use Pump start signal (please see the manual) and adjust the delay in the range of 0 to 500 us.

What is the jitter of the synchronization between optical pulses and maximum Pockels cell opening?

>>>> It is less than 200 ps.

Can you operate the system without synchronization with optical pulses? E.g. in case the beam is weak – there is less than 1-4 mW needed for synchronization.

>>>> The control unit can operate without synchronizing to the femtosecond pulse train if it has the external triggering signal that has been synchronized to the femtosecond pulse train (with jitter <200 ps).

Or you can use the signal from the external photodetector that you may have (the amplitude of the femtosecond pulse train on the 50 ohm oscilloscope input is 300 mV-1 V) by feeding it to the BNC input of the control unit and using it instead of the built-in photodetector. 

In my first e-mail, I asked for system with long or variable opening. Although I claimed it is not so important for us, could you send me price of systems with long (about 50 ns) and variable opening?

>>>> Please find enclosed the quote for the pulse picker with variable HV pulse duration.

In specifications you sent me I found information about HV pulse duration at 10%.

What is rise time 10% - 90 % of that pulse?

The characteristics are as follows:

Level to Pulse duration:

0.9-0.9 – 2.3 ns

0.5-0.5 – 5.5 ns

0.1-0.1 – 8.9 ns

Rise time (0.1-0.9) – 3.3 ns

Fall time (0.9-0.1) – 3.4 ns

Amplitude – 7-9 kV (adjustable)

>>>According to the specification the repetition rate is 1 Hz – 1 kHz. Does 1 Hz mean also single shot repetition rate (e.g. one shot per 10 minutes) or is it really 1 Hz?<<<<

It is actually single-shot, you can open it when necessary.

>>>What is RF source and RF input. What is it used for in this system?<<<

In this case the RF source is the frequency of the optical pulses. For this system it should be in the range of 30-120 MHz for normal operation (so 75MHz in your setup is fine). A part of the optical power (1-4 mW@75 MHz) is routed to the by the fiber into the built-in photodetector for proper synchronization of the Pockels cell with the femtosecond pulse train.

>>> I suppose the polarizers are implemented in the system. And we do not need to buy them alone. Am I right?

Yes, they are included in the system.

>>> If the polarizers are implemented, what type of polarizers is used.

We use Glan-Taylor Calcite Air Spaced Polarizers. On your request we can change them for Rochon Prism Polarizers.

I am interested in Pockels cell for blocking pulses of Ti:Sapphire laser with broad spectrum with central wavelength 805 nm.

We want to use the Pockels Cell to block the pulses in front of detection system.

Only some pulses at single shot repetition rate should be transmitted. 

We want to use it for stretched pulses of Ti:sapphire laser. Duration of these laser pulses is about 300 ps. But the spectrum is about 100 nm FWHM broad, central wavelength is 805 nm.

Repetition rate of laser pulses is 75 MHz.  Average laser power is about 1 mW. So the peak power of one pulse is approximately 40 mW.

But at single shot repetition rate there will be amplified pulse (actually, the repetition rates are 10 Hz or one shot per several minutes). This pulse should be transmitted through PC. The pulse will be about 1000 times amplified.

Is it possible to have repetition rate 10 Hz and single shot together? 

The PC should stay opened for approximately 50 ns.

Is it possible to vary the time, for that it is opened? 

Could you make an offer for beam diameter 5 mm and beam diameter 10 mm? 

How much costs such a Pockels cell and what would be its parameters

(crystal, rise time, spectral transmission,...)? 

Is it possible to use the Pockels cell also for unstretched pulses of Ti:Sapphire laser?

The duration is about 15 fs, repetition rate 75 MHz, average power is about 100 mW, energy per pulse about 2 nJ, peak power about 150 kW beam diameter (1/e2) < 2mm? 

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.