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Edit: Laser diode info page

I have a basic question about laser diodes. For a 14-pin butterfly package as shown below. I know that I need to control the current going in to the laser diode, but I don't know about the voltage. Should the voltage on anode(11,13) to cathode(3,12) be regulated? Or is it okay if the voltage is below the maximum ratings after the current is limited? Thanks in advance.

type2biast absolute ratings

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    \$\begingroup\$ Just FYI, note that "Absolute Maximum Ratings" which you currently have shown in your question, has a specific meaning (search for previous questions mentioning that phrase). They are not the maximum values which you should expect to use in normal operation. If you edit your question to add a link to your specific datasheet, you might get more advice. \$\endgroup\$
    – SamGibson ♦
    Commented Sep 29, 2018 at 21:18
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    \$\begingroup\$ Check out the action over at Why is a lab PSU not suitable for driving a laser LED directly?. \$\endgroup\$
    – Transistor
    Commented Sep 30, 2018 at 9:10
  • \$\begingroup\$ No, you do not as long as you are below the maximum rated voltage. \$\endgroup\$
    – winny
    Commented Sep 30, 2018 at 9:19

2 Answers 2

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The LD voltage must stay below the max rated voltage for the laser diode. It will if you control the current to the LD and the laser isn't damaged.

Usually you monitor the voltage, and the current and control on the photodiode (which is power output) and shut things down if the voltage or the current approach the maximums.

You'll likely need a controller on the TEC as the laser needs to be cooled and the wavelength dependence is about 0.3 nm per degree C.

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  • \$\begingroup\$ So I understand the forward voltage that is referred as "2 V" at max does not require any control. It is enough when the input of the laser diode is below 2V with control of the current going in to the laser diode. \$\endgroup\$
    – Zed K.
    Commented Sep 30, 2018 at 12:12
  • \$\begingroup\$ Yes. Your laser should be shipped with a test datasheet. You'll see what the V I relationship of your laser is. Run the laser at low power, confirm that you see the same characteristics and you'll be ok. \$\endgroup\$
    – D Duck
    Commented Sep 30, 2018 at 22:16
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The PD is used to regulate lasing current in the LASER diode and the TEC current is regulated by temp using the thermistor to minimize junction temp rise assuming more than adequate heat transfer in the design.

Ultra low ESL due to -2V abs damage threshold for diode max. It is improved by reducing slew rate of current during shut down.

PD=Photo Diode= " Monitor Diode" used for regulation of intensity. Peltier cooler (PEC and thermistor for Thermal negative feedback for temp regulation. If these are foreign to you, better master these, before trying a LASER like this.

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    \$\begingroup\$ Word sallad! Did op ask about either PD, TEC, ESL or slew rate? No. No, he did not. \$\endgroup\$
    – winny
    Commented Sep 30, 2018 at 9:18
  • \$\begingroup\$ @winny et al (2) Let me remind you , when you think word salad, ask yourself , Why do you not understand?. Do your re-search. This is critical. ALL OF THE ABOVE is necessary to control V and I for a simple laser as shown in the diagram. You have a lot to learn. \$\endgroup\$
    – D.A.S.
    Commented Sep 30, 2018 at 10:47
  • \$\begingroup\$ PD=Photo Diode= " Monitor Diode" used for regulation of intensity. Peltier cooler (PEC and thermistor for Thermal negative feedback for temp regulation. This is the correct short Answer. Read more , doubt less. and dont worry about my typos like your "sallad." \$\endgroup\$
    – D.A.S.
    Commented Sep 30, 2018 at 10:51
  • \$\begingroup\$ The clarification in the comment is a big help, @Tony. Why not add them into your answers as standard. It would really help the quality of your answers which while they may be technically excellent are very tough reading, particularly for novices. If you're under time pressure then just answer fewer questions. You could also create a wiki page for all your favourite initialisations and acronyms. I think there are a few of us prompting you but reception seems to be filtered out somewhere. \$\endgroup\$
    – Transistor
    Commented Sep 30, 2018 at 13:03
  • \$\begingroup\$ You only need to read the datasheets not come here to ask. I give hints that can be time consuming to explain to the novice. But this redundant if it must be clearly defined in App Notes and Datasheets. I only suggested the acronyms in the image to imply the servo loops that control LASER power. This forum will never become like Wiki without major front end changes and professional peer review. perhaps an automated Wiki link suggestion popup could save time to insert definitions of terms might be added to the site's javascripting \$\endgroup\$
    – D.A.S.
    Commented Sep 30, 2018 at 13:13

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