My Lasers

       I like to play with lights since I was a kid, when I grew older, Lasers fascinated me so I like to collect them.

       Here are some of my surviving and recently acquired laser pointers and modules.

7mW 532nm Green
150mW 405nm Violet
70mW 532nm Green Lab style
DIY Laser Power meter
150mW 405nm Violet V2
57mW 450nm blue pen style pointer
1W 1.7W 445nm Blue Burner
190mW 635nm Opnext rebuild (LPF)
100mW Osram 520nm single 14500 build (LPF)
Fan cooled 9mm diode build (LPF)

This green laser is a few years old. I have two of this. One is installed on my airsoft gun since it is quite visible in the day. Output was measured at about 10mW using my DIY Ophir LPM. One of it no longer works. Output dropped to a few mW even with about 300mA input with a very bad beam profile. Something degraded badly inside:

I took out the old green module and rebuilt this using a 635nm red module from DTR. [Link]

I got this module (below my older laser) from eBay. It is advertised as a 405nm 150mW module. Input is about 3-5VDC. I measured its output at 233mW using my DIY Ophir LPM. It is focusable but only uses a plastic uncoated lens. Can burn stuff when the beam is focused to a point. I used a broken green laser host similar to the one above as a battery holder with switch:

Here is a recently completed lab style laser module. It was advertised as a 50-70mW unit with automatic temperature control. Fan runs only when the laser head gets warm. I measured this to be about 77mW using my DIY Ophir LPM.

Lab style lasers usually have a separate laser head and driver module since they are intended to be installed in equipments. I made a metal base plate to keep them together as one unit making it more portable.

Medicine bottle rubber plug makes a convenient dust cover:

Back side showing DC input jack:

The front piece is made from polycarbonate sheet. With clever use of the micro mill, I was able to make round shapes and mill a round hole on the inside to accept the bottle bung. No CNC's here! I also added an O-ring between the laser head and the front piece to seal it against dust.:

The hole was made intentionally small, just enough for the beam to come out so that dust will not easily get in and also keep fingers out from touching the lens:

An external DIY 3S2P 18650 Li-Ion battery pack power this laser for portable use:

No beam shots yet since it is still bright:

       This project has been superseded by my new Ophir 20C-A-1-Y based laser power meter.

       This is how I measure the output power of my lasers. I found a schematic for a thermal laser power meter using easily obtained components and a DVM as a display. I would not think it to be very accurate but gives a decent ballpark figure to estimate laser power output. With the sensor protected from ambient airflow, I find the measurements are repeatable and very consistent. I later found out that as is, the circuit from the link has an upper limit of around 620mW then the op amp output cannot go any higher. Replacing the two 220K resistor for 68K decreased gain and allowed more output swing to get to around 2W but the target might get too hot or even burn up at that temp.

DIY laser power meter:

I built it using SMD components as I have many in stock:

SMD resistor with leads attached to be used as
calibration heater and laser target:

Back of SMD resistor painted with matte black heat resistant paint
as laser absorber:

sensor diode in contact with resistor with silicone grease in between:

Laser target painted black to absorb the laser radiation:

The acrylic enclosure is not exactly my best work but it works very well
for the purpose of preventing ambient airflow affecting the measurements:

DVM probes attached ready to measure:

Shoot laser here:

       26 Jan 2013:

I wanted to make the 200mW 405nm laser more 'handy'. To do that, I wanted to combine the battery and laser head as one.

Start by cutting lexan offcuts to size:

Drill two holes - one for the laser head and another for the battery:

Here is how I milled round shapes on the micro mill:

And carefully lower the mill bit and rotate the piece:

Two pieces partially completed:

Now, to smoothen the sides:

An hour later and we test fit the pieces:

The front piece milled to accept the button and tact switch:

Milling makes a lot of dust:

Finished parts ready to assemble:

Solder new wires to the laser head:

Run the wire through holes drilled for it:

Solder and position the switch:

And it works - burning a piece of heatshrink (smoke not visible in the camera):

A couple shots of the completed laser:

       24 Mar 2013:

       My first blue laser. This one is built about 2 weeks ago so that I have something I can use for presentations without burning the screen or blinding the audience. No build pictures as I didn't have access to a camera at the time but I had to fix an intermittent problem so here are a few shots. It uses the 3.8mm Osram PL450B diode running at 100mA. Power source is 2xAAA or 1x10440 Li-ION + dummy spacer. Output power is measured at around 5-13mW depending on battery voltage when using 2xAAA and a steady 57mW with a 3.7V 10440 battery. Lens is 3 element glass for 398-480nm. Host was bought from ePay for pen style lasers but the front part is different as it was originally intended for 5.6mm diodes so I had to make my own. Even at 5mW, the beam is visible at night when pointing at the sky. I love the 3 element lens with this diode. At about 60ft, the dot is still about the same size as when it came out of the laser pointer!

Pen style laser pointer:

Driver board top side:

Driver board bottom side:
The metal band is the positive contact to the body of the host.

Business end: (3 Element glass lens)

Blue dot!:

Making an endcap from a blown electrolytic capacitor:

Using my mill, a tungsten carbide V cutter and a dividing attachment
to cut a smooth round hole with beveled edge at the end:

Using a very sharp tungsten carbide bit makes nice smooth burr free cuts:

Nice cleaner look than the bare brass end:

Here is the battery I use for this laser. 2X paralleled 10440 cells.
A single cell and a dummy cell would work just as well but I didn't like the idea of having wasted space
- plus you get double the runtime with 2 cells in parallel:

       Since I used the 3 element glass lens in the other laser, I'm currently using an acrylic lens in this one. And with the new dual 10440 battery setup, I decided to measure its power output just for curiosity's sake. It maxed out at 111mW using my DIY Ophir LPM!

       Disclaimer: I don't recommend soldering directly onto Lithium Ion cells as they can burst into flames or explode. At the very least, reduced capacity due to heat damage as these types of batteries are very sensitive. For those brave enough to try, first, ensure both cells are at exactly the same state of charge - this is very important. Then, I suggest using good quality leaded solder (lower melting point) and a hot temp controlled iron with a high heat capacity tip. This allows quick spot heating of the ends. Touch the tip just long enough to tin solder to the ends then let cool, then reflow tinned copper tape onto the tinned parts on the battery. Use Kapton tape to insulate the copper foils and to bind the cells together.

       This will be my second blue laser. I'm still waiting for the 12mm module with 3 element glass lens from DTR. The host is available online for a few $$ and is intended to be focusable. I chose the host for the keyswitch interlock and side momentary button. A momentary button is inherently safer as it turns off when you let go or accidentally drop it. I ordered a 600mW module that lasted less than a week The beam was fine but had large divergence and left the laser at an angle. Lens was plastic and output power peaked at only 520mW. It wasn't focusable without slight disassembly but fit the housing and powered by two 16340 cells in series and lasted just enough to be played with for a bit until it broke haha.

Disassembled housing - from left to right:
18650 battery, tailcap with keyswitch, battery extension (without this, one 16340 battery fits in the housing), main barrel, end cap:

Disassembled main barrel - from left to right:
driver pill, machined polycarbonate button, heatsink with brass threaded insert:

Driver closeup: this driver is based on LTC1700 datasheet application circuit so much so that the parts designators also match. Output is constant voltage at 5.1V with a 1 ohm current limiting resistor (R4 - removed on mine) in series with the positive output. I have read reports of it smoking, ofcourse you'll get smoke - when you try to dissipate 1W on a 1/4W 1206 SMD resistor!

Other side: You can see the new bigger R4. The switch along with a mosfet and an LED controls pin4 of the LTC1700 to enable momentary mode. When the keyswitch is on, The LTC1700 goes to standby mode (pin4 shorted to ground by FDV301 mosfet connected across C4) pressing the button turns mosfet off, powers up the boost converter with soft start and lights up the diode.

Machined button and threaded ring. The aluminum ring came with the host and is a perfect fit but I needed a thread to screw in the 12mm module. The brass insert was from the barrel of the broken 600mW module and press fit into the aluminum ring. Thread is M11x0.5mm which is the same as the back threads of the 12mm module arriving soon.

Waiting for the diode module....

Why not use the included aluminum button? I made a transparent button for the indicator light. The button lights up when the keyswitch is ON and the driver in standby mode, ready to shoot beams of 1W blue light.

       Some reading on the internet led me to these posts about this driver when it first came out.
New at AixiZ driver and lens for 1 watt 445 builds
O-Like New 1W 445nm diode / 200mW 405nm laser diode driver.!
Unsure about new O-Like 445/405nm driver
which led me to post my findings about this driver.

       The driver is based directly off the LTC1700 application circuit diagram except for the Mosfets and tantalum caps (orange ones) as I'm unsure of the values as they are unmarked. The "driver" is basically a DC-DC converter with an output voltage of 5.1V (measured) and a 1 ohm 1206 size current limiting resistor in series with the positive output. Same thing as adding a resistor in series with an LED to limit current when using a constant voltage supply so it is not a true constant current source. The LTC1700 is a very efficient DC-DC converter as it uses synchronous rectification and uses the Mosfet's Rdson for input current limiting but then this high efficiency is nulled by using a "dropper" resistor to limit current resulting in a average to poor efficiency rating depending on diode Vf. An issue I can see is that once the laser diode heats up, Vf lowers due to the junction temperature coefficient. This will cause the current through the laser diode to increase a bit. Worst case would be thermal runaway of the diode if it is not properly heatsinked. I changed my resistor to 0.47ohm for a measured max current of about ~1.5A with a Vf of 4.3V, well below the 1.8A suggested limit for my diode for some SOA margin as the diode heats up. As I mentioned before, when running this driver for long duty cycles, it is recommended to replace R4 with a separate physically larger wattage resistor for better power handling as it dissipates a bit of power during operation.

       The driver also uses Mosfet reverse polarity protection (no lossy diodes) and during testing, I found it operates well down to about 2V input while still supplying max output current then tapers sharply below that. I used a single IMR18650 and it ran full output down to about 2V battery voltage then dimmed greatly shortly after that. The soft start function is also nice and by using a low current normally closed switch (or normally open sw + mosfet/transistor + pull up resistor) across C4 which shorts the LTC1700 Pin4 to ground setting it to standby mode for intermittent push-on operation but still retaining the soft start functionality and that the switch does not need to handle the full current required by the diode and driver allowing the use of very small tact switches as I did in my host. Another option would be a reverse clicky across C4. This would result in a forward clicky type operation (switch on position = laser diode off) for a combination of momentary/push on-push off switch which I may try in a lab style build in the future.

       26 Mar 2013:

       I finally received the laser diode! Unfortunately, there seemed to be a mistake in my order. I received stock acrylic lenses on the modules where I was supposed to get 3 element glass lenses (correct lenses on the way - thanks Jordan!). I couldn't wait so I installed the diode and took the 3 element lens from the other 450nm laser pointer and it burns! I was worried about the driver putting about 3.7V on the output when in standby (due to the synchronous MOSFET body diode) and the result was that once the key is turned on, the laser glows below threshold making a dim blue glow coming out the front. Once the button is pressed, the laser diode glows with full output. It is nice though with the dim glow acting as an aiming beam when trying to burn stuff.

       27 Mar 2013:

       Finally, here are some completed pictures and beam shots!

Laser diodes in copper modules from DTR:

Laser diode module screwed into aluminum heatsink with thermal grease in the threads then connected to the driver pill:

Press fit in the host:

I had to bore out the inside of the original focus adapter to make room for the module. A foam strip around the small internal focus knob allows enough grip so that turning the host focus ring also turns the lens barrel inside allowing focusing.

Keyswitch in ON position and laser diode glowing below threshold. Battery current is about 15mA:

Pressing the button turns driver ON and provides full current to laser diode:

Beam shot in the workshop:

Another beamshot pointing at the sky and a water tank about 600m away:

       For power output, with about 1.5A across the laser diode with a 3 element glass lens, I'm getting around 970mW output. But a little experiment with the LPM, when the laser and 250mW cal heater turned on, it should display ~1220mW but I'm only getting 1150mW due to nonlinearity at the top end of the thermal sensor range so this laser should be doing around 1W. I'm still contemplating on upping the current. As it is, the host gets pretty warm in a couple of minutes use. Increasing current will reduce the duty cycle even more. I still have two more 445 diodes so maybe do it in a lab build with active cooling.

       13 Apr 2013:

       Since I bought a 3-pack 445nm diode from DTR, I tried an experiment. I've read reports of efficient diodes and... less efficient ones so I decided to see if I got a freak diode in my 3-pack. I removed the diode module in the 1W laser and tied all three diodes in series. Connected it to my bench power supply and increased the current gradually and noticed that they all don't lase at the same current. There were clearly three different threshold currents for all three diodes so I chose the one which lased earliest and installed it into the host. With the previous diode, I measured about 970mW max. Now, using the new diode and same 3 element lens, I was getting 1,172mW easy and the sensor target started smoking! Output current from the driver was measured to be the same. An Ophir sensor is on the way so I can verify the exact power output. Stay tuned.

       30 Apr 2013:

       I've built my new DIY Ophir LPM using an Ophir sensor head and measured this laser to consistently do over 1.4W using a 3 element lens and over 1.7W without a lens. [23 Dec 2013] The laser now does 1.7W with a G2 lens

       09 Aug 2013:

       I bought an ePay 3 pack red/green/violet pointer set to add to my laser collection and made measurements and posted the results in Laser Pointer Forums, check out the link for more information.

Page created and copyright R.Quan © 06 Jan 2013.