Laser

1. Fast Axial Flow CW CO2 Laser
Set up the co2 laser project not as easy as electronics or microcontroller project whether 
building the CO2 laser or use it as part of system tool of the project. You may not approve 
to buy the CO2 laser for personnal use. The cost of laser project also high which depend on 
the type of laser and power level. Generally, the CO2 laser project done at research institute, 
universty or company commerce projects. When dealing with laser, it is very important to ensure 
that you are familiar with it characteric, precaution and safety. The CO2 laser is above class 
3b laser and the beam is infared (10.6 micrometer) which invisible for human eye. The system 
use high voltage power supply (can be up to 20KV) to excited the laser medium. It is better had 
some experiance personnal guide you on the CO2 laser project. Here, I will present some 
information on building the CO2 laser but not the full detail. If you had some experiance on 
CO2 laser, it may be useful for you but not for beginner or who start from scratch. This CO2 
laser project is under my Master study at the university of Malaya, Malaysia. I am complete the 
Master study at 1996 (2 year to complete the project). This CO2 laser is Fast axial-flow dc 
excited laser system which start build up from stracth. I has some experiance on building the 
slow axial flow CO2 laser. The set up of slow axial flow CO2 laser is a lot easy compare with 
fast-axial-flow system. The electrical power desinty input to fas-axial-flow CO2 laser is a lot 
more then slow-axial-flow system (can be more than 10 order). The following photo shown the the 
fast-axial-flow CO2 laser which I has been build it during my Master study. The purpose of this 
project is build up the laser and study the factors affecting the efficiency, performance and 
laser power.



This system consists bacically of the following components:
1) discharge channel and optical resonator
2) cooling system
3) vacuum and gas recirculating system
4) gas flow and ducting connecting the mechanical components
5) electrical-power supply
6) measurement unit
7) gas supply unit

Following block diagram show the basic operation of fast-axial-flow CO2 laser. 



After the gas medium is excited using a DC high voltage electrical discharge, the hot gas 
medium will be rapidly removed from the discharge channel by a gas circulating pump. Two 
heat exchargers are used to cool the gas after it is passed through the laser discharge 
region and after its compression by the gas circulating pump. A small amount of the 
recirculating gas will be removed by vacuum pump to the atmosphere and an equal amount is 
injected into the system from the gas supply inlet. This will reduce the gas contamination 
species which are the by-product of chemical reactions during the electrical discharge.
Following schematic show the basic set up of this system.



The circulating pump is a mechanical booster pump or root pump. A variable frequency 
converter is used to protect the root pump motor from overloading/overheating. It is 
also used to control the rotating speed of the root pump, this will also control the 
flow rate of laser gas medium. The high voltage power supply is a simple home built 
3-phase D.C. rectified circuit as show here:High Voltage Circuit. 

A few method has been tested, it was found that a simple washer attached to the side pin 
anode configuration enhanced the discharge stability and enabled the input power to be 
increased. The result of this electrode design had been published at Japanese Journal of
Applied Physics (vol.38, pp.5117-5120, Part 1, No. 9A, September 1999):www.jjap.or.jp. 
The design of this side pin electrode shown here:side pin anode. 
The maximun laser output power of this two discharge tube configuration is around 300W. The 
maximum laser output power raise to around 630W when the system increase to four discharge 
tube configuration. Now, this system had been raise to eigth tube configuration which produce 
the maximum output of around 1.4KW (I am not involve in this project, the most recent progress
not sure). All control/adjustment of system such as pressure, gas inlet/outlet rate, current, 
input power and so on are manually controlled/adjusted. However, the basic safety feature such 
as high voltage over current trip, root blower motor over load trip will automatic activate if 
any abnormal condition occur.The total cost of this project around USD25,000.
Some latest information may direct know from laser laboratory,, Physics Department 
of University Malaya :fizik.um.edu.my/laser/. or more general regarding Physics Department 
of University Malaya at here::fizik.um.edu.my/. 


The introduction of my master project (chapter 1) download here:chapter1.zip

Some teori of this type of laser system (the chapter 2 of my master thesis)
download here:chapter2.zip

Detail of laser design (chapter 3) download here:chapter3.zip

NOTE
1. The mirror alignment is very critical, ensure that the output coupler and back mirror 
   aligned parallel with each other (out of a few micro radial may cause lasing process vanish).

2. Ensure all high voltage point proper insulated either from low voltage side or easy touch by 
   people. Alway discharge the high voltage poit before working with it. 

3. Ensure that no any flame-able or explosive material around the working environment in case
   accidentally fire by laser beam.


The online laser tutorial can find here:
1. www.bithose.com/serfaq/sam/lasersam.htm.
2. www.cord.org/lev3.cfm/48.
You can find a lot of information from this two website such as teori, construction, safety,
frequent ask question and a lot more.

2. Laser cutting and marking sample

The above fast axial flow CO2 laser had been used to cut a few different type of material
such as wood, mould steel, stainless steel, arcylic, paper, plastic, mabble and so on.
The cutting sample shown as following: click photo to enlarge

The laser marking on various metal using copper vapour laser shown on following. This
copper vapour laser is high frequency (10 to 16KHz) pulses laser with maximum output 
power of 2W (use unstable resonator and sealed tube cofiguration). The beam quality 
and divergent of laser is very important in this case. I has experiece the problem
when using stable resonator configuration and unable mark on metal even using the 
20w power of laser (compare the unstable configuration which only need 1.5W). 
The laser beam focusbility depend on beam quality and beam divergent. The unstable
resonator configuration reduce the beam divergent (as telescope principle).

  

3. Suggestion on laser project
The high power laser project may not be suitable as personnal hobby project. However, low 
power laser such as laser diode for pointer may used for certain project. I has an ideal of 
possible project using low power laser as data tranfer tool or communication tool. The ideal 
as following: 

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email: [email protected]