lab grade laser differences

[MacGyver404]

I was wondering if you guys could tell me the differences between Lab grade lasers, portable lasers and laser pointers. Next i would like to know what it would take to make a lab grade laser built around a I'd like the one from an hd-dvd player. I should probably post this in my profile details but i will tell you here. I am an electronics hobbyist, as i am sure many of you are as well. I was going to college for a degree in telecommunications electronics, so what you guys tell me doesn't have to be really simplified.

 

[daguin]

Pointer

Portable

Lab style

Peace,
dave

 

[Laser_Ben]

That is for sure NOT lab quality! :

 

[daguin]

That is for sure NOT lab quality!  :

No. That is lab style.

How about this one then

Peace,
dave

 

[rocketparrotlet]

That's about as easy and simple an answer I could ask for!

-Mark

 

[Cyparagon]

Unlike portables, lab modules can be on at full power indefinitely, generally have modulation capabilities, are larger, require mains power, and are far more stable.

 

[MacGyver404]

so what would i have to do to turn a LD from say a HD-DVD player into a lab grade laser?

 

[MTWallet]

so what would i have to do to turn a LD from say a HD-DVD player into a lab grade laser?

This http://www.laserpointerforums.com/forums/YaBB.pl?num=1221888056 will show you how to build a lab style laser.

 

[Achro]

I am a relative newby here at the forum, but not new to lasers.

Cyparagon is pretty spot on in his assessment. I would add to this that commercial lab lasers are designed for many and varied purposes. They are generally designed to operate stably for long periods of time without mode shifts, at stable power so that they can perform in a variety of demanding tasks with little maintainence. Some lab lasers may be purpose designed for a narrow research purpose. Depending on the end use, they may even allow access to the inside of the resonator cavity to permit tuning or tinkering the optical path inside the resonator. What you want to design all depends upon your end use. Do you want to do experimentation with optical physics and materials? Holography? scanning and light shows? welding and cutting? or just popping balloons and lighting matches? Depending on your use, you may want linear or random polarization, clean TEM00 mode, continuous or pulsed operation, long life, or long coherence length.

Some applications require very stable laser, others are not so critical. For stability, control of the temperature of the various elements is especially important, hence the big heatsinks. Temperature will affect the dimensions of the resonator, the mobility of carriers in the semiconductor and the properties of the lasing transitions within the lasing medium. Control of the power output is not too difficult for diode lasers by using active optical feedback and/or active temperature control as long as the laser is operated well under it's maximum rating and held at a stable operating temp. If you just want short term stability, you can operate most diodes with (a moderate) constant drive current or constant drive power, and a big heatsink. If you know some electronics, this should be no problem - you will need to avoid overcurrent, current overshoot, esd, transients, and reverse current at all costs or you will make a crappy LED out of your laser diode.

Lasers such as the diode pumped 532nm greens use additional elements such as Yag and KTP crystals to convert a high power IR diode laser output (808nm) to a usable frequency to pump the YAG (1064nm), then double the frequency to get 532nm green. Stable green lasers are much more difficult to design as a result.

You may want to peruse Sams laser faq - just google [sams laser faq diode laser]. Also, you might want to download and read through some laser diode specs - they all operate pretty similarly, basically a forward biased diode junction, albeit at different threshold currents and operating points. Like blue leds, shorter wavelengths laser junctions operate at higher bandgap energies, hence need higher forward voltages to get to the operating current level. You can google GH04P21A2GE and find a high power violet diode datasheet to study at the Sharp microelectronics website. High power reds or IR's operate at lower forward voltage drops but may have much higher currents depending on power.

< I've been doing this for stuff for 30 years and you asked for not "really simple" >

be afraid - be careful!

 

[MacGyver404]

I went and looked at the page for the DIY labby that MTWallet pointed out (thanks) and i would like to use the feedback from the LD, except i have noticed that all of the drivers i have found links to so far don't use the feed back. I would also like to have the option for modulation, i have found one or two drivers that can do this but they don't use feedback. Also how would i go about making it temperature controlled, obviously i will be using a TEC and a thermistor. Is there a simple analog circuit i can use for this?

 

[GooeyGus]

get a pic based tec controller and a solid state relay... that will control your tec easily.

You cant use feedback with the blu-ray diodes because most of them do not have built in photo diodes. SOOO... you could do it but it would be much more complex. You will need to use an external photo diode as well as a clear piece of glass at a 45 degree angle. This will take a small portion of the beam and reflect it into the photo diode. The you would need to build some sort of circuit to raise and lower diode current based on what voltage that photo diode sees.

 

[Achro]

You could use almost any constant current driver, such as the LM317 circuit or the Rckstr circuit to set the maximum diode current. Then, just connect a shunt transistor such as an npn or an nfet to steer some of the diode current to ground in order to control the current/light output. You could amplify a photodiode for negative feedback. Use a summing amp / integrator (proportional and integral controller ) to drive the shunt. In this manner, when your photodiode exceeds a set reference level, the shunt sinks current, reducing drive to the LD, closing the loop to stabilize the output.