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Review of the Directly-Injected 505nm Bluish-Green ("Mint Green") Laser Pen

The_LED_Museum

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DIRECTLY-INJECTED 505nm BLUISH-GREEN ("MINT GREEN") LASER PEN, retail $79.00

Manufactured by (Unknown)
Last updated 09-09-18




This is a bluish-green-emitting diode laser in a fat pen-style body.

But it's not DPSS (Diode-Pumped Solid State) like those now-common green laser pens, pointers, and portable lasers -- no, this one uses a new technological advancement that allows bluish-green laser radiation to be produced directly, without the need for those messy, fragile nonlinear crystals!

Laser diodes like the one in this unit that do not rely on frequency doubling or tripling crystals to produce their output are known as directly-injected diode lasers.

This is the first of these bluish-green lasers to have been mass-produced in a totally self-contained "pen" format -- that I'm aware of anyway.

It's rated to produce 5mW of laser radiation at 505nm in the bluish-green part of the spectrum (these values were measured at 58mW with a wavelength of 507.2nm).

Because this is a laser, you should not shine it into your eyes, other people's eyes, pet's eyes, etc. Just use a little common sense here, k? (It's significantly over spec anyway -- you definitely DO NOT want to use this as a cat toy!
)





To use your Directly-Injected 505nm Bluish-Green Diode Laser Pen, just press the rubbery purple button on the tailcap until it clicks & then release it.

To neutralise the laser, just perform the exact same action.

The laser's focus can be adjusted from infinity (extremely narrow spot even at some distance) to a medium, oblong spot by rotating the bezel (head).


To change the battery in this laser, unscrew & remove the tailcap, and set it aside.

Tip the used 18650 cell out of the barrel and into your hand, and recharge it.

Insert a freshly-charged 18650 cell into the barrel, flat-end (-) negative first. This is the opposite of how batteries are installed in most flashlights, so please pay attention to polarity here.

Screw the tailcap back on, and be done with it.

Current consumption measures 322mA on my DMM-BLE-2x01A "Mooshimeter".


The Directly-Injected 505nm Bluish-Green Diode Laser Pen is water-resistant (actually submersible to 5 meters {~16.4 feet}). So you need not worry about carrying and using the laser in rain or snow -- but if you really do get the business-end soiled, you'll have to douche it off with cool water from the faucet (tap) and dry the AR window with a microfiber cleaning cloth.

The hosel for the laser diode and collimating lens has a female threaded receptacle; though I have no idea what it is designed to be used for.
Closer examination reveals that an AR (Anti-Reflective) coated window blocks access to the threaded portion, so I'd probably not worry about it at all.

Laser speckle appears to be more tightly spaced than I've seen in red-emitting laser diodes; however this is not a significant issue for the vast majority of potential purchasers of this laser; only a true laserist (not a false laserist!) is likely to even notice something like this.

This laser has a published duty cycle of 1 minute on, and 10 seconds off to allow for cooling of the laser diode and its driver circuit.




Power output peaks at 47mW (power output peaked at 58mW when I was performing the stability analysis).


Post-long term stability analysis power output test.
Power output peaks at 50mW.


Long-term laser stability cum battery discharge analysis (in violation of the published duty cycle recommendation) of this unit. As you can see, it ran for 3:04 before it started to peter out.

Test was conducted using a generic (unlabelled) 2000mAh 18650 Li:ION cell.

Laser's case temperature over the lasing portion measured 83°F (28.4°C) at 3:00 into the test. Ambient temperature was 71°F (21.6°C) as measured using a CEM DT-8810 Noncontact IR Thermometer.
I measured the laser temperature a number of times, and it never exceeded 83°F (28.4°C). This tells me that (with the amount of electrical current being sunk) the heatsinking of the laser diode is either quite excellent or very lousy; though considering that the output power remains relatively stable, I'd go for "quite excellent".

The power generation curve of this lithium ion cell (well, all lithium cells & batteries actually) is known to be fairly uniform; only dropping off sharply near the end like somebody slammed the toliet seat onto its head. So it was no big surprise to me that this laser remained relatively stable (varying in output power by 6mW or less) for as long as it did.
I judge overall stability to be excellent considering that this a very low priced (for this unusual wavelength) consumer-grade laser!

VERY IMPORTANT!!! That "spike" at 1:15 was generated by me closing and then opening the display on my laptop computer; this caused the flimsy little table that I have everything set up on to jiggle; I quickly repositioned the laser and the LPM's sensor and allowed the test to continue.

The stability analysis (tab-delimited that can be loaded into Excel) is at 505nm.txt


Repeat long-term laser stability cum battery discharge analysis of this unit. As you can see, it ran for 2:21 before it started to very rapidly peter out.

Retest was conducted using the same cell (a generic (<i>unlabelled</i>) 2000mAh 18650 Li:ION cell).

Laser's case temperature over the lasing portion measured 81°F (26.7°C) at 2:14 into the test. Ambient temperature was 73°F (22.8°C).<BR>
I measured the laser temperature a number of times, and it never exceeded 82°F (27.8°C).

The stability analysis (tab-delimited that can be loaded into Excel) is at 505nm2.txt.



Third long-term laser stability cum battery discharge analysis of this unit. As you can see, it ran for 2:47 before the power output started to very rapidly go down the toliet.

Retest of the retest was conducted using the same cell (a generic (unlabelled) 2000mAh 18650 Li:ION cell).

Laser's case temperature over the lasing portion measured 83°F (28.4°C) at 2:33 into the test. Ambient temperature was 72°F (22.2°C).<BR>
I measured the laser temperature a number of times, and it never exceeded 83°F (28.4°C).

The stability analysis (tab-delimited that can be loaded into Excel) is at 505nm3.txt

These tests were conducted on a LaserBee 2.5W USB Laser Power Meter w/Thermopile.




Beam terminus photograph on a framed picture (laser was discharged onto the white portion) at ~12".
Beam image bloomed quite a bit; it also shows a lot of white that doesn't exist in the actual beam.

I DO NOT HAVE A 532nm GREEN DPSS LASER TO COMPARE THIS ONE WITH, SORRY!!! :(


Beam terminus photograph on a door at ~15 feet.
As with the above photo, the beam image bloomed quite a bit; it also shows a lot of white that doesn't exist in the actual beam.
You should also be able to see the beam itself; this is in large part due to Rayleigh scattering.


Photograph of the laser's actual beam ootdoors; photo was taken at 11:09pm PDT on 08-18-18 in Shelton WA. USA.


Photograph showing the beam from this laser and the Directly-Injected 5mW 488nm Greenish-Blue ("cyan") Laser Pen outdoors at night. Photograph was taken at 9:42pm PDT on 08-22-17.


Photograph showing the beam from this laser and the Directly-Injected 5mW 488nm Greenish-Blue ("cyan") Laser Pen directed toward an interior door.<BR>


Photograph showing the beam from this laser and the Directly-Injected 5mW 488nm Greenish-Blue ("cyan") Laser Pen with the lasers positioned a distance away from the camera.



A look "under the hood" as it were; this allows you to see the laser diode itself.
It's that small brass-colored can-shaped structure near the center of this pic.


Here's proof that I really performed, "The Toliet Test" on it.
Needless to say, it passed this test with flying colors (colours)!
Considering that this laser is advertised to have a 5 meter submersibility rating, it had better pass!!!

PLEASE NOTE that this test was conducted in the cistern (toliet tank); the water in this part of the loo is actually potable (drinkable) so I did not have to sterilise the laser after this test; I only needed dry it with a bit of bungwipe and I was good to go.


Spectrographic analysis of this laser.


Spectrographic analysis of this laser; spectrometer's response narrowed to a band between 500nm and 520nm to pinpoint wavelength, which is 507.2nm.


Spectrographic analysis of this laser; spectrometer's response narrowed to a band between 800nm and 874nm to check for the presence of a pump laser (why bother when I know that a longer wavelength pump laser does not exist?) -- as you can plainly see, it really, truly doesn't exist!!! (I irradiated the spectrometer's sensor quite well in effort to capture this!)

The raw spectrometer data (tab-delimited that can be loaded into Excel) is at 505point.txt



Spectrographic analysis of this laser taken after ~three (3) hours of continuous operation to check for spectral drift; spectrometer's response narrowed to a band between 500nm and 520nm to pinpoint wavelength, which is 505.4nm.

The raw spectrometer data (tab-delimited that can be loaded into Excel) is at 505poin2.txt


Spectrographic analysis of this laser after 25 minutes of continuous operation (laser was not neutralised before taking this spectrum!)
My CEM DT-8810 Noncontact IR Thermometer is not capable of measuring the temperature of something as small as this laser diode.

Spectrometer's response narrowed to a band between 504nm and 509nm to pinpoint wavelength, which is 506.1nm.

Spectrographic data file (tab-delimited that can be loaded into Excel) is at 505nm9.txt




Spectrographic analysis of this laser taken after one (1) hour exposed to a relatively cold temperature; measuring 15°F (-9.4°C) -- this was the temperature of our household freezer.
Spectrometer's response narrowed to a band between 500nm and 510nm to pinpoint wavelength, which is 504.4nm.

Given that the laser junction (the area that produces laser radiation) is exceptionally small -- approximately the size of a bacterium -- I honestly didn't expect to see any significant spectral shift.

The raw spectrometer data (tab-delimited that can be loaded into Excel) is at 505cold.txt


USB2000 Spectrometer graciously donated by P.L.

Spectral line halfwidth (FWHM) of this laser was measured at 2.8nm.


A beam cross-sectional analysis would normally appear here, but my ProMetric 8 Beam Cross-Sectional Analyser that I use for that test was destroyed by an almost-direct lightning strike in mid-July 2013.



In leiu of a beam cross-sectional analysis, I present to you this photograph that shows the ovoid beam profile, which is characteristic of a diode laser -- this clearly shows that it has fast and slow axes.
The collimating lens (*NOT*, "lense"
) was removed from the laser for this photograph.



Brief video showing how this laser behaves when the battery is just about petered out. Notice that it blinks rapidly instead of staying in CW (Continuous Wave) mode. I looped it two times to accomodate the length of the music.

The music that you hear is zax from the Commodore 64 computer game, "Master of the Lamps" by Activision from 1984.
This product is not audio (sound)-sensitive in any manner; the music may safely be ignored or even muted if it piddles you off.

This video is 60,996,775 bytes in size; dial-up users please be aware.



TEST NOTES:
Test unit was purchased on Ebay on 08-08-18, and was received at 12:02pm PDT on 08-17-18.


UPDATE: 09-09-18
Found a duty cycle recommendation for this laser; 60 seconds on 10 seconds off.


PROS:
Very unique beam color -- 505nm is very radiant and unusual for a portable laser.
Beam is clean with few unwanted artifacts and no 'dirty lens' speckling in it.
Uses a rechargeable cell -- never have to buy disposables for it.
Unit is SIGNIFICANTLY overspec!

NEUTRAL:
There is a rather minor "halo" visible WAY OUTSIDE the main beam

CONS:
CDRH warning label states wavelength incorrectly (as 460nm which is actually quite forgiveable considering how new 505nm lasers are) and none of the, "maximum power output" boxes at all are checked.
Does not have CDRH-mandated safety features required of a Class IIIb laser in the United States (keyed interlock, beam shutter, emissions indicator, delayed laser emissions). But coming from a Chinese manufacturer and very likely not intended for USA use, these can be somewhat overlooked; that's the primary reason why I still awarded it five stars.


MANUFACTURER: Unknown
PRODUCT TYPE: Fat "pen"-style portable laser
LAMP TYPE: Directly-injected bluish green-emitting laser diode
No. OF LAMPS: 1
BEAM TYPE: Adjustable from very narrow spot to medium oblong spot
REFLECTOR TYPE: N/A
SWITCH TYPE: Rubbery "reverse clickie" on/off button on tailcap
CASE MATERIAL: Metal
BEZEL: Metal; laser diode, collimating lens and AR-coated window recessed into deep hosel for them
BATTERY: 1x 18650 Li:ION rechargeable cell
CURRENT CONSUMPTION: 322mA
WATER-RESISTANT: Yes
SUBMERSIBLE: Yes, to 5M (~16.4')
ACCESSORIES: Dual-slot battery charger
SIZE: 193mm L x 14.50mm Dia.
WEIGHT: 164g (5.79 oz.) empty -- 206.70g (7.290 oz.) incl. battery
COUNTRY OF MANUFACTURE: China
WARRANTY: 1 year

PRODUCT RATING:




UPDATE 08-25-18: Performed a long-term stability analysis cum battery discharge analysis.

UPDATE 08-26-18: Performed post-stability analysis spectroscopy to check for wavelength drift.

UPDATE 08-27-18: Performed a second long-term stability analysis cum battery discharge analysis.

UPDATE 08-28-18: Took a post-stability analysis output power measurement.

UPDATE 08-29-18: Performed spectroscopy after ~25 mins. continuous operation to check for wavelength drift.

UPDATE 08-30-18: Performed narrowband spectroscopy at relatively cold temps to check for wavelength shift.

UPDATE 08-31-18: Performed a third long-term stability analysis cum battery discharge analysis.

UPDATE 09-01-18: Added a pair of indoor "beam" photographs.

UPDATE 09-08-18: Added a brief video showing how this laser performs in LVC.

UPDATE 09-09-18: Found a duty cycle recommendation for this laser.
 
Last edited:



Cyparagon

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Re: Review of the Directly-Injected 505nm Bluish-Green Laser Pen

Where HAVE you been, sir? This is the detail I like to see in a review. None of that 3-sentence "Feels good in the hand. Very bright. Here's a picture" rubbish. Excellent work as always.
 
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BowtieGuy

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Re: Review of the Directly-Injected 505nm Bluish-Green Laser Pen

Glad to see you posting again; another fine review as usual, I always like seeing your spectro results! :yh:
:gj:
 

diachi

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Re: Review of the Directly-Injected 505nm Bluish-Green Laser Pen

Have to agree with Cyp, what an excellent review! Very refreshing, lots of detail and well written. :beer:
 

The_LED_Museum

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Re: Review of the Directly-Injected 505nm Bluish-Green Laser Pen

Where HAVE you been, sir? This is the detail I like to see in a review. None of that 3-sentence "Feels good in the hand. Very bright. Here's a picture" rubbish. Excellent work as always.
Sorry about my extended absence. :(
I simply haven't had any lasers to evaluate since the Skytech 520nm jobbie from last year.

Thank you for your compliments regarding my reviewing format and details that I add (I believe that you are referring specifically to the spectrographic analyses, power output measurement, current consumption, etc.) :D
Receiving accolades for any of my work is always well appreciated!
 

hakzaw1

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Re: Review of the Directly-Injected 505nm Bluish-Green Laser Pen

Where HAVE you been, sir? This is the detail I like to see in a review. None of that 3-sentence "Feels good in the hand. Very bright. Here's a picture" rubbish. Excellent work as always.
Glad to see you posting again; another fine review as usual, I always like seeing your spectro results! :yh:
:gj:
Have to agree with Cyp, what an excellent review! Very refreshing, lots of detail and well written. :beer:
^^^ ALL these posts well worth while quoting- these are the reviews worth reading and 'attempting' to emulate in your reviews +rep for LED M.

welcome home rep!!

hak :wave:;)
 
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paul1598419

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Re: Review of the Directly-Injected 505nm Bluish-Green Laser Pen

Very good review of this laser. However, the diode used in these are from a series of Sharp single mode laser diodes that have been released since about a year ago with some attempts at making a 488nm that turned out to center at 473nm. I have one in a build that measured 477nm. There have been several releases since then with these 505nm diodes coming in at different iterations that I have logged over my efforts to document the wavelengths of each diode. If you look closely at the metal around the diode's window you may see an SB number. I documented six of these starting with SB1473N91 which came in between 502.4nm to 503.5nm. SB147EC91 which came in at 507.9nm to 509.8nm. SB1573N91; 502.0nm to 503.8nm. SB217HL91; 501.7nm to 502.5nm. one SB217N91 at 505.3nm. SB147EB91; 508.0nm to 509.8nm.
 

The_LED_Museum

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Re: Review of the Directly-Injected 505nm Bluish-Green Laser Pen

Bumpity bump bump: Performed a long-term stability analysis cum battery discharge analysis.
 

The_LED_Museum

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Re: Review of the Directly-Injected 505nm Bluish-Green Laser Pen

Bumpity-bump bump: Performed post-stability analysis spectroscopy to check for wavelength drift.
 

paul1598419

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Re: Review of the Directly-Injected 505nm Bluish-Green Laser Pen

I have noticed no drift among my Sharp diode lasers either. They are all well heat sinked, so I actually set my spectrometer to read the wavelength continuously over a ten minute cycle. Of the ones I tested like this, they remained rock steady where they started. Not surprising considering they are all very well heat sinked.
 

Cyparagon

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Re: Review of the Directly-Injected 505nm Bluish-Green Laser Pen

I have noticed no drift among my Sharp diode lasers either. They are all well heat sinked
Drive current is a much bigger contributor to wavelength changes than temperature is, when it comes to these indium-based diodes (violet through green). It's the reds and infrareds that shift rather drastically with temperature.
 

paul1598419

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Re: Review of the Directly-Injected 505nm Bluish-Green Laser Pen

Drive current is a much bigger contributor to wavelength changes than temperature is, when it comes to these indium-based diodes (violet through green). It's the reds and infrareds that shift rather drastically with temperature.
They do drift with temperature. I have watched it myself many times when allowing the diodes to increase in temperature by 40* C. They will climb by as much as 4nm from 20* C to 60* C. Current does cause an increase in wavelength, but it remains steady there as long as the temperature is regulated.
 

The_LED_Museum

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Re: Review of the Directly-Injected 505nm Bluish-Green Laser Pen

Bumpity bump bump: Performed a second long-term stability analysis cum battery discharge analysis.
 

The_LED_Museum

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Re: Review of the Directly-Injected 505nm Bluish-Green Laser Pen

BTTT: Took a post-stability analysis output power measurement.
 

Benm

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Re: Review of the Directly-Injected 505nm Bluish-Green Laser Pen

So it shifted down about 2 nm after 3 hours of operation. I'm not sure about any points in between, but i'd guess that it shifts down most within the first 10-20 minutes or so and then thermal equilibrium is reached.

0.2nm/K is a fairly typical shift value for diode lasers, so that'd correspond with just 10 degrees of temperature change between start and final measurement - fairly impressive for something that small, yet the power dissipation isn't that large either. If you's put a 1 watt 445 in there it would move a lot more, but then again the batteries wouldn't last 3 hours by any chance ;)
 




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