Ultra Laser 120mW DPSS Green Laser Pointer Mode Change

This is a 120mW double AAA powered 523nm laser pointer that has been cooled down to about 20C. The beam goes through a lens system to spread the beam out so that the effect is pronounced at shorter distance, here about 1.5m to the wall.

At the start of the video the camera first adjusts to the brightness of the laser. After about 40 seconds you can see what appears to be a mode change from TEM00 to TEM01. Then, the laser is pulsed on and off showing the quick transition from TEM00 to TEM01... I think.

Is this what is really going on?

so after doing some experiments last night i think i understand. these lasers, whether they be the Ultra Lasers specifically or all DSPP laser pen types, have a narrow peak operating range. if the laser is out of this range, hot or cold, the laser will go into what looks like a TEM01 mode and power diminishes. With in the narrow operating range, there is peak power and TEM00.

My laser, if out of range on the cold end, will sometimes not switch to TEM00 while on continuous wave. It will need to be turned off and then on again to switch to TEM00. Then after around 20-40 seconds depending on ambient temp it will switch to TEM01 over about 5 seconds. Then it needs to cool off.

I am only saying TEM00 and TEM01 because thats what it looks like but it might be some other mechanism that is creating what looks like two dots butted up against each other.

What would be nice is a temperature sense circuit that is set to illuminate an LED green when the laser is in operating temp. This way when you turn it on you know if you should let it cool or warm up. and while its on you can see when it goes in and out of range. stock there is no way to tell other than do what i do: shine it on my hand and if it stings in about 1s its in range, if not its out of range.

Category:

Science & Technology

Tags:

• laser
• pointer
• green
• 532nm
• 120mW
• 100mW
• DPSS
• IR
• TEM00
• mode

[skaplan1995]

@jacobssandy I'm pretty sure this is projected onto a wall and not straight into the camera aperture :O

[jacobssandy]

I don't mean to be rude, but you should never ever look directly into the beam of a laser pointer. It can cause permanent damage to your eye.

[rachm06]

This depends largely on the peak power inside the crystal, and its orientation. The 808 nm beam must be focused with a lens on the yvo/ktp, or if it is without a lens, the crystals must be very near to the diode with metallic cover removed.

The best temperature for the SGH in the KTP is around 35° C