Decreasing driver current to a laser diode ?

Thread Starter

Externet

Joined Nov 29, 2005
1,960
Hi.
If the current is decreased; does the beam get dimmer or stops lasing ? Is there plotted curves current vs. light or power output to learn how it behaves ?
 

Boggart

Joined Jan 31, 2022
67
Unlike LEDs, laser diodes need a specified minimum current to lase, often called the threshold current. For example, a Rohm RLD65PZB5 has a typical threshold current of 60mA and operating current of 150mA. Interestingly, some laser diodes, such as the Sony SLD3135VL, list the threshold and operating currents as the same (15mA in the case of that Sony diode).
 

Tonyr1084

Joined Sep 24, 2015
7,199
I've had coin cell operated laser pointers (cat toy) that get dim as the batteries wear down. As Ohm's law predicts, reduce the voltage to a resistive circuit and the amperage will drop.
 

MisterBill2

Joined Jan 23, 2018
13,754
My experience with small 630nm lasers is that over some range the intensity varies with current, but below that point they do not emit light. Those were lasers in the 2 to 5 milliwatt power level. Never did try overdriving them, they were not cheap.
Those were from "Creative Technology" aka "Laser66". No clue if they are still in business.
 

Ya’akov

Joined Jan 27, 2019
6,856
I just did a quick experiment with a generic red laser module and it continued to emit detectable light down to .09mA! It dimmed (apparently) linearly with current.
 

MisterBill2

Joined Jan 23, 2018
13,754
I have not checked them recently, and so I wonder if they have started opening the emails that they get. I used their laser packages in one product line and they worked rather well, except that the lasers get week after 8 years of constant operation. The techs at that client were too lay to switch the devices off at the end of the day. And the last time I sent an email identifying the model that was used originally, and asking for a price of an order for 64 more of them, they did not respond to several requests.
So that was the end of dealing with them.
 

Thread Starter

Externet

Joined Nov 29, 2005
1,960
Hi. Am I reading this correctly ?

1666994561380.png
At above 120 μJ the emission changes from flourescence spontaneous emission to stimulated lasing emission ?

Is the spontaneous emission also lasing + monochromatic + directional + coherent + polarized + high energy + speckle or which of these are not ?
 
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