Hello,

when talking about efficiency there is no ways to do lamp efficient. The reason why they are still used is high energy of single flash. All CW lasers nowadays operate on laser diodes. Only systems that require high energy pulses and low repetition rate uses flashlamps.

Assume you are building pulsed laser. With wavelength selection there is nothing to do. Xenon emits as it emits and Nd absorbs as it absorbs. There is moderate overlap of Xe line emission and Nd absorption. However, if current density is extremely high lamps gas starts act more like black body rather line emission. Here first tip - keep energy moderate in range of 10-20 J/cm3 of lamps gas per single flash.

The second, you need to match pump pulse duration to laser material decay time. Formally excitation should be as short as possible, but that would kill lamps. Lifetime of lamp depends in 6 order of current. Shorter flash (electrical) pulse - shorter lifetime of lamp. Typically it is recommended to keep excitation pulse duration ~ 0.5 of laser material decay. For Nd:Yag this would be ~30us. Longer pulses would lead to better lifetime of lamps, but slightly lower efficiency.

Third, is a reflector. It is strongly recommended to use silver-all mirror coated, close to elliptical reflector with blue absorption. This makes energy coupling most efficient and removing blue prevents heating of laser material by unnecessary radiation which have low impact on excitation.

Finally, there are lamps in production. You need just approximately take a reference like this - lamps gas gap should be ~1cm longer as rod and gas channel diameter also similar to diameter of the rod. If you rod is 10mm in diameter and 150mm long choose lamp with similar parameters like gas diameter 8-10mm and ~160-170mm gap. If rod is 4x60, lamp should be like 4-5mm gas diameter and 65-75mm gap. First one produces enormous energy and low rep rate (

You can use the filters around the flashlamp and to let passing only main frequency to excitation ( around 800 nm).

In other away you can use the IR laser (same the TV remote control) with adequate power.

ROS

Hello,

when talking about efficiency there is no ways to do lamp efficient. The reason why they are still used is high energy of single flash. All CW lasers nowadays operate on laser diodes. Only systems that require high energy pulses and low repetition rate uses flashlamps.

Assume you are building pulsed laser. With wavelength selection there is nothing to do. Xenon emits as it emits and Nd absorbs as it absorbs. There is moderate overlap of Xe line emission and Nd absorption. However, if current density is extremely high lamps gas starts act more like black body rather line emission. Here first tip - keep energy moderate in range of 10-20 J/cm3 of lamps gas per single flash.

The second, you need to match pump pulse duration to laser material decay time. Formally excitation should be as short as possible, but that would kill lamps. Lifetime of lamp depends in 6 order of current. Shorter flash (electrical) pulse - shorter lifetime of lamp. Typically it is recommended to keep excitation pulse duration ~ 0.5 of laser material decay. For Nd:Yag this would be ~30us. Longer pulses would lead to better lifetime of lamps, but slightly lower efficiency.

Third, is a reflector. It is strongly recommended to use silver-all mirror coated, close to elliptical reflector with blue absorption. This makes energy coupling most efficient and removing blue prevents heating of laser material by unnecessary radiation which have low impact on excitation.

Finally, there are lamps in production. You need just approximately take a reference like this - lamps gas gap should be ~1cm longer as rod and gas channel diameter also similar to diameter of the rod. If you rod is 10mm in diameter and 150mm long choose lamp with similar parameters like gas diameter 8-10mm and ~160-170mm gap. If rod is 4x60, lamp should be like 4-5mm gas diameter and 65-75mm gap. First one produces enormous energy and low rep rate (

The question is whether you are interested in CW or pulsed laser. For pulsed laser, the best pumping source to pump a Nd:YAG laser is Xenon flash lamps which are available from different suppliers or you can get these from Spectra Physics, USA or Quantel, France; these are not very expensive. However, it also depends what kind of cavity you are using and what is the dimensions of the Nd:YAG rod.

For the CW operation you can use high power diode lasers which are now a days available form China.

You need not to optimize such flash lamps as they emit quite broad; around 800 nm which lies very close to the absorption of Nd:YAG crystal and the lasing is achieved at 1064 nm.

have fun.

Aslam

Dear Gintaras,

First of all, Thank you so much for clear answer and I am sorry to answer back late.

I have some questions about your answer, you mentioned that we should keep moerate energy in the range of 10-20 J/cm3, and excitation pulse duration is typically ~ 0.5 of laser material decay time, do you have some references related to these interesting comments?

Actually I am going to select a Xenon linear flashlamp as the Nd:YAG rod optical source. I know that some parameters like inside bore diameter, arc length and optical emitted power are all very important to know, so base on these input parameters I wish to select the most perfect Xe flashlamp to have high optical efficiency. I found some interesting information in these attached cataloges, however, I am a little confusing to match all the parameters especially optical power of the lamp to other parameters. The Xenon flashlamp in which I am interested in is highlighted in both files, but I don't know how can I make myself sure that this is a good selection. (In CatalogueVQF pdf, page 12) and in the (High Performance Flash and Arc Lamps pdf, page 25) are highlighted.   

Dear Gintaras,

First, thank you for your answer. I am interested pulse regime of Nd:YAG laser. I followed some cataloges, but I am not able to match all the necessary parameters in the cataloges to make myself sure about lamp selection.    

 Best

Davood Danaei

Hello,

sorry for not reading your comments. I just not on computer these days.

Regarding VQ catalog information; there are quick explanations about pulsed operation. Your highlight in page 6 is related to the pump supply where energy storing capacitor and pulse extending inductor takes place. By removing L you would shorten electric discharge and significantly increase current density. However these parameters have indirect link to pumping efficiency (some degradation of IR line emission). C is as it is in the supply but L you can mount any you want. Thus you can make electric discharge duration as needed. Actually current pulse (p. 6) is well proportional to momentary optical power of the lamp. Thus you can model how pump energy will be emitted. And absorbed with material saturation and spontaneous decay. What all this about? There is not mentioned how laser material is involved. When you have some optical power like spectrum of the lamp at certain conditions you can overlap it with Nd absorption and start to calculate how pump energy is deposited. So, emission and absorption spectra do not overlap well. Anyway due to huge energy of the lamp Nd starts to be excited. Excited ions do not absorb anymore. Material starts to be transparent till spontaneous emission starts. That means loss of energy stored by laser material. But Nd once again starts to absorb. Actually I never saw well modeled excitation by computer. But I remember practical measurements a bit. So, there is nightmare of optimizing everything (laser material birefringence, thermal lensing, crack power, cooling requirements, excess heat due to absorption in vis uv, ...) especially when you need flash lamp to operate as long as possible. And when lamps emission depends on current. Empiric recommendation was to keep optical-electrical pulse about half of material decay time. And that worked for decades. Lower current densities associated with more efficient lines in IR emission. So, you may like two lamps with lower current for one rod. But that is pricy and pump supply should be able to fire two.

Ok, about practical use. Lamps you selected looks good for application. There is no one best of bests. We used different manufactures and bit different specifications but everything worked well (with Nd:glass of various doping, diameters, rep rates). The same lamps for everything. We even used same lamps (looong time ago) for Nd:YAG and Nd:YLF with good results. I have an impression that there will be no drastic difference between similarly (closely) specified lamps in practice. Not so much that you would not compensate by tuning pump voltage knob a bit. The problem you may find is more related to housing. You can mount different diameter lamps with different size O-rings if there is enough space. Actually single lamp is not devilishly expensive. By one, make a laser "sketch" and take a look what pump power you need for the result. Which yet is not well specified by you. Then make a decision does you need thinner one if pump voltage too low or thicker (and bigger C) if it is too high (or maybe two lamps). Most probably you will fit lamp into same housing just with different O-rings.

Finally, VQ page 12 specified Max.Power is electrical power.

Take a look also at www.heraeus-noblelight.com

These comments are messy, but things which you can really influence and which are more linked to efficiency are laser cavity design, elimination of parasitic losses, good optical couple of lamp and rod and proper cooling. These should gain more for the output like very very well selected lamp.

Good luck,

Gintaras

Dear Gintaras,

Again tank you for answer.

Actually I am interested in match a particular Xenon flashlamp with these present information.

Bore diameter=6 mm, Current density=2400 A/cm^2- Gas fill Pressure=500 torr, optical pulse widths=500 us, electrical energy to fire=195 J (This energy is needed to produce optical power, we calculated this energy base on the efficiency of lamp to produce electrical power to optical power) 

Arc length=minimum present arc length around 100 mm to match to other parameters,

However the maximum achievable frequency of any kind of flashlamp does not mentioned in cataloge specifications, it seems that we can calculate this frequency base on electrical energy, electrical pulse width and average maximum power.

Base on above information, dose my lamp in which I selected is suitable? 

Best regards,

Davood Danaei