This week, a new goodie for my laser collection arrived. I always wanted to own a 473nm laser because of the awesome, azure blue light. In comparison to this, the 445nm Nichia Diodes almost look violet.
Despite many of the units, which are apparently pulled from medical equipment, suffer from power and mode fluctuations, mine arrived lasing in a nice TEM00 mode out of the box.
The divergence is not that good, but I guess a bit of realignment should do the trick. As mine arrived without the power supply, I had a bit of fun figuring out the power supply lines on the D-SUB connector.
It turned out that pins 5&9 on the standard DB9-Pinout are connected to VDD, and pins 1,2&6 to GND. Pin 4 is the TTL modulation input, the laser will fire when this pin is pulled high. The driver board must be connected to a 5V supply with a nominal current rating of at least 4A.
Opening the top cover reveals the guts of this neat CNI-made setup. It consists of (from right to left)
Pump Diode->Collimating Optics->Anamorphic Prism Pair->Focusing Optics->Crystal Assembly
The crystal assembly is protected by a plastic cover. Removing this allows a look into the resonant cavity. Dominant is the big Lithium triborate (LiB3O5) crystal used for the generation of the second harmonic. The two aluminium parts hold the cavity optics (Output coupler and High reflector), the Nd:YVO4 crystal sits near the black focusing optic in the brazen plate.
Using feedback from a photodiode, these units were stabilized for 10mW optical output. When I find some more spare time, I will try to realign the cavity and focusing optics and perhaps install a higher powered pump diode. Let’s see if I can push more than 50mW of stable power out of it. 😉