Diode Laser

What does a diode laser module add to a diode laser? A voltage regulator or current limiter?

Reply to
Jon Slaughter
Loading thread data ...

or

A laser diode usually has a built in photodiode for constant power control. A simple module would provide the trans-impedance amplifier in a loop with the laser to provide a voltage in to light power out conversion. More complex modules would have additional features like temperature control.

Reply to
Wanderer

So when exact intensity control is not needed one can simply use a resistor a.k.a. the basic method used for current limiting led's?

Reply to
Jon Slaughter

or

Yup, a current source will work fine. I don't think module is well defined when it comes to diode lasers. I would assume that the module has the collimating lense. Where a bare diode would not.

Speaking of diode lasers we just made a 'lifetime' buy of DL-7140's from Sanyo, last production run. These lase near 780nm are are great for Rubidium stuff.

George H.

Reply to
George Herold

or

There are two reasons. The first one is that laser diodes are rather fragile components. Now, it depends on the particular laser diode you are using, but the situation was way worse in the past. The second reason is that the lasing threshold is very much temperature dependent and if the system is exposed to temperature changes. For example, the current which provides the nominal output power let's say at 25=B0C can be dangerous at a lower temperature, since the threshold has decreased in the meanwhile. I have seen a resistor (or even the internal resistance of the batteries) limiting the current in very cheap laser pointers but I would not go on that system for any serious laser use.

Reply to
Darwin

or

If you're just working with one laser yes. You need to set the current above the threshold. But the power output will vary a lot from laser to laser and with temperature. Odds are the laser will get hot and die. The voltage drop of a laser diode is very temperature sensitive. The TIA circuit is very simple you can do it with one dual opamp. One opamp act as the TransImpedance Amplifier and the other act as a difference circuit. I don't know what laser you are trying to use but for many of the smaller ones available at digikey an LF353 is good choice for this circuit. If you need more current you can add a transistor to the driver.

Reply to
Wanderer

That's all cheap laser pointers have, but I'd reccomend a decent current regulator circuit - as someone else pointed out, lasers can be a bit fragile.

Reply to
ian field

Lol.

Last one I did a driver for datasheet rated maximum power 10mW, absolute maximum power 11mW for 10uS.

Reply to
nospam

Current regulation is very important.

Reply to
Jamie

Not temperature control itself but they contain a thermistor, typically a 10k version.

--
Regards, Joerg

http://www.analogconsultants.com/
 Click to see the full signature
Reply to
Joerg

Here, the beast of choice is the EU38 for learning.

We really do prefer constant current sources, laser diodes respond very well to transients on resistor only supplies, often blowing the faucet off the face of the laser diode/ diode and turning it into a weak led.

formatting link

formatting link

A fellow I know has a patent on, and makes these, to protect the LD against static

formatting link

Lasorbs are NOT snake oil, they do what they claim.

Steve

Reply to
osr

Appointech sells us nice diode lasers and detectors. I don't know if they do 780.

John

Reply to
John Larkin

Oh yeah. I prefer current sources as well. For hobbyists the LM317 rigged as a current source should do quite well. It's a well-behaved regulator.

Although I often couldn't live with the large capacitance. So far I have not destroyed one, and I've worked with quite a few including some in the four-digit a piece price range. As long as the current source can never ever spike and there's a reverse diode protection most situations are ok.

--
Regards, Joerg

http://www.analogconsultants.com/
 Click to see the full signature
Reply to
Joerg

:

istor

Thanks John, these were just the bare diode used in Cd players. We get them for ~$15 each. If we every run out of the 300 we have on hand and the 400 we have on order then I'll have to go searching.

George

Reply to
George Herold

How do I determine the working current from the datasheet? I have an OPV322 that I ran from about 3mA to 5mA. The datasheet says the max is 12mA(Maximum Forward Peak Continuous Current) and the threshold is 3mA. It says the min total power output is 1.5mW at If=7mA.

So I take it that the operating range is 3mA to 12mA with average of 7mA?

What I don't understand is that mouser listed this as a 5mW part and on the datasheet it has the warning box which says 10mW and the spec says 1.5mW.

In any case it does work but I would like to get about 80-90% of the maximum which I'm figuring is about 10mA.

Reply to
Jon Slaughter

Lousy data sheet!

I've had weird experiences with Optek lasers. And their applications engineers don't seem to know much about their own parts. I think they buy chips in rainy back alleys in Singapore or something.

And they keep changing the recipes. Different batches seem to be different parts.

What are you doing with them?

John

Reply to
John Larkin

or=20

Most often, an optical interface with a connector.

Reply to
JosephKK

Dang sticker power is always at least twice the rated power, it is the theoretical max power before the part would incinerate itself and allows for a wide safety margin.

Steve

Reply to
osr

Just playing around with some night vision stuff. I got it to 10mA and it didn't burn up so I figure that is probably the max I'll take it. It's nothing serious. Main thing I need to deal with is the optics. Essentially trying to build an infrared flashlight to replace one that used an IR led and was terrible. Nothing serious though and just for fun. Main thing I gotta worry about is not doing self-lasik ;)

Basically 6V's got me 1.7V across the diode at 10mA(had 430Ohms in series). Thats 17mW which far exceeds the spec if they are 5mW's unless I'm missing something.

Reply to
Jon Slaughter

You are missing that the spec is for the *optical power output*, but you are measuring the power input!

The failure mechanism for laser diodes is usually excessive optical output power, so it is this that you must constrain,

But your 10mA is just about within the 12mA @25'C rating, so that is why it has not blown up.

Careful - laser diodes are normally very sensitive to even very short overloads (microseconds-nanoseconds). You may already have blown it up. It would still take current but the output will be down to almost nothing (it turns into a weak LED). You need to be careful with ESD.

Having said that this one accepts a 48mA 1us pulse so it is not as sensitive as some.

--

John Devereux
Reply to
John Devereux

ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.