# Laser diode input/output ratio

I am a photo technician working in photographic labs to repair printing machines.

I am trying to better understand how these machines operate.

### Blue laser gun

• Laser gun type = 473 $nm$ blue dpss.
• On label = maximum output 50 $mW$, 473 $nm$, type 3b laser.
• Actual output power according to the manufacturer specification = 102 $\mu W$.
• Now when I read with the power meter = 40.6 $\mu W$.

### Green laser gun

• laser gun type = 532 $nm$ blue dpss.
• on label = maximum output 100 $mW$, 532 $nm$, type 3b laser.
• actual output power according to the manufacturer specification = 706 $\mu W$.
• now when I read with the power meter = 279 $\mu W$.

My questions are:

If a 473 $nm$ dpss module outputs power at the exit window at 102 $\mu W$, what is the power of diode?

If a 532 $nm$ dpss module outputs power at the exit window at 705 $\mu W$, what is the power of diode? You can say approximately, according to your experience, just a starting point to start replacing experiment of laser diodes.

In this dpss laser modules the pump laser diode portion and the frequency doubling crystal portion are separated by a chamber. There is c-mount and to five 9mm laser diodes are used. I know how to replace / align a diode inside the gun.

Now I want to replace the original diodes with the new one for the both modules due to week output. Suppliers discontinue this product and they are not supporting it any more. My question is what is the output power of the diode in side the laser guns? Approximately what is the diode power to start replacing diode?

• Are the lasers CW (continuous wave) or pulsed? If they are pulsed, what is the repetition frequency of the pulses? Jul 6, 2015 at 12:06
• This lasers are CW from good japan's company. Jul 7, 2015 at 15:02

## 1 Answer

Conversion from the diode wavelength to the fundamental wavelength is generally a highly efficient process. Conversion efficiencies in the high 90 percent range isn't unheard of for 1064 nm generation, which is the fundamental wavelength of the green laser. Conversion to 946 nm, the fundamental wavelength of the blue laser, can also be highly efficient but is generally less so than for 1064 nm. To be safe, I would assume an efficiency of 70% for 946 nm and 80% for 1064 nm.

The second harmonic generation process can also be highly efficient when used with pulsed lasers, but is significantly less so with CW lasers. This is especially true for the low powers with which you are working. For your lasers, I would guess the efficiency is something like 5%.

Guestimate Summary

• Blue Laser: $70\% * 5\% = 3.5\%$
• Green Laser: $80\% * 5\% = 4.0\%$