445nm Dilda Direct Drive .. just for fun

My diodes arrived today .. so I had to test them right ? And I don't have any driver yet .. so I tried direct drive with 4.5V battery. Even if it held the voltage, it should work at about 1W .. but it dropped nicely to 400mA, thus estimated 200-300mW.
I used old broken dilda host, as it is easy to dismantle. I even used the 'red' lens. They actually reflect blue more then usual, but being low power I risked it.

Of course this is just for fun, I HAD to see the color, right ? I love how this blue scatters in the air .. and the purple glow around the dot .. beautiful ! Camera can't quite capture the colors.








Btw. I can confirm that these cheap glasses Focal price anti-green works great even on 445nm. I heard some people received them broken, or did receive different glasses, but if you get the right ones and intact, they just work. Except you won't enjoy the blue ! I must make some 200mW (diffusion safe) variant too.

very nice but very risky, but you should wait on a driver if you want it to live for a long time.

Why risky ? I'm aware of battery voltage peaks and ESD risks .. but I acted to minimize those. I know about back-reflection risk .. but IMHO there is less reflection from 'red' lens at this power then from 'blue' lens at 1.6W. I know about heat risk, but this is bottom of the diode performance envelope, and the host handles 200mW red diode quite nicely.
Did I miss something ?

The 445nm color is quite awesome. It almost appears to be two colors in one (blue and purple). Since the dot is blue, but all the diffuse reflections and beam appear to be purplish.

How well can you pick up the beam with your eyes? For me, the 445nm beam is very visible (even at 65mW during the day in a room). To me, a 50mW greens beam is slightly less 'bright' looking than my 65mW 445 beam.

batteries can become unpredictable i know many people who want to remain nameless that are DD lots of their lasers and i just want to let you know that a battery after every charge if you are direct driving needs to be checked with a load that is not your laser on it to make sure its not doing anything funky.

It's rather visible .. the beam I made was rather thick (like 5mm at the aperture). For sure more bright then 200mW red, which has practically invisible beam. I did not compere it with green ones .. will do next time I feel like running it.
And the color is just cool. Red .. well .. they are cheap and direct .. good burners .. but everybody knows that color from LEDs or cheap 1mW pointers. Green is something special .. but the color is somewhat chemical, aggressive .. but this blue .. it's like from scifi movies.

kiyoukan said:

batteries can become unpredictable i know many people who want to remain nameless that are DD lots of their lasers and i just want to let you know that a battery after every charge if you are direct driving needs to be checked with a load that is not your laser on it to make sure its not doing anything funky.

Click to expand...

I would agree with that. But the battery I used is not even rechargeable. It's not even alkaline battery, and I knew it drops the voltage very fast. I was more afraid it would not lase at all. I discharged possible peak with fingers, and measured the battery several times to check how it holds. And I don't plan to really use it in this configuration.

Thanks for advice anyway !

The main issue with driving direct, is controlling heat. If the diode is not heatsinked very well, it would begin to eat up more current in a form of thermal runaway.

I'm sure DTR knows the risks, but then again these diodes have been proven to be very hardy!

Hmm .. thermal runaway is interesting problem. It would be nice to measure it somehow, so it is predictable. Can this problem be estimated ? Is it worse or better or same as with red diodes for example ? I understand the experience with it must be pretty rare, as few people do direct drive.

this is no fair!!! how come mine died using a driver and 440mA

That sucks man !

I did not kill any diode yet .. but sure I did kill many other sensitive parts. And I never knew what I did wrong. You follow all the rules .. and now it work, now it don't.
Gee I hope I'll not kill the diode with driver too ! Bad driver can be worse then wisely chosen battery.

I tried to put the 445nm diode to the old dilda driver .. it works, but not really well. The driver cannot reach even 400mA, and I have to use rechargables which have larger voltage. I estimate the output under 50mW as it can't burn at all. Still it is nice small package, and I like the color.

EDIT: with fresh batteries is more like 100mW .. beam is nicely visible in dark.