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Review of the Directly-Injected 488nm Greenish-Blue Laser Pen

The_LED_Museum

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DIRECTLY-INJECTED 488nm GREENISH-BLUE ("CYAN") LASER PEN, retail $66.98

Manufactured by (Unknown)
Last updated 09-13-18




This is a greenish-blue-emitting diode laser in a fat pen-style body.

But it's not DPSS (Diode-Pumped Solid State) like those now-common green and light blue (473nm) laser pens, pointers, and portable lasers -- no, this one uses a new technological advancement that allows greenish-blue 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 greenish-blue lasers to have been mass-produced in a totally self-contained "pen" format -- that I'm aware of anyway.

It's rated to produce 1mW of laser radiation at 488nm in the greenish-blue part of the spectrum (these values were measured at 75mW with a wavelength of 488.7nm).

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!
)

This is listed as being model # 488T-60-F-W but I was still not able to find the product's OEM on the web.




To use your Directly-Injected 488nm Greenish-Blue 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 488nm Greenish-Blue 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.

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.

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 is likely to even notice something like this.

Does this evaluation look an awful lot like the one that I made for the Directly-Injected 5mW 505nm Bluish-Green Laser Pen?
Thought that you'd say so.
That's because these lasers are physically and electrically almost identical, so I could use the 505nm laser's eval. as a template for this one.




Power output peaks at 68mW.


Post-long term stability analysis power output test.
Power output peaks at 70mW.


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 2:50 before it started to peter out.
This is actually a retest; approx. 1.5 hours into the first one, I accidentally bumped something that I shouldn't have and subsequently queered the test; so I recharged the cell and started a second test. :-/

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

Laser's case temperature over the lasing portion measured 82°F (27.8°C) at 2:20 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 82°F (27.8°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 less than 4mW -- maybe 5mW) 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!

The stability analysis (tab-delimited that can be loaded into Excel) is at 488nm.txt.


Repeat long-term laser stability cum battery discharge analysis of this unit. As you can see, it ran for 2:34 before it started to very rapidly go down the tube.

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

Laser's case temperature over the lasing portion measured 87°F (30.6°C) at 1:43 into the test. Ambient temperature was 77°F (25°C).
I measured the laser temperature a number of times, and it never exceeded 88°F (31.2°C).

The stability analysis (tab-delimited that can be loaded into Excel) is at 488nm2.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 doen't exist in the actual beam.


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 doen'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 outdoors; photo was taken at 8:57pm PDT on 08-21-18 in Shelton WA. USA.


Photograph showing the beam from this laser and the Directly-Injected 5mW 505nm Bluish-Green 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 505nm Bluish-Green Laser Pen directed toward an interior door.<BR>


Photograph showing the beam from this laser and the Directly-Injected 5mW 505nm Bluish-Green Laser Pen with the lasers positioned a distance away from the camera.


Photograph showing this laser's radiation reflecting off an interior window.


Photograph showing this laser's beam crossing a room.
Taken with photoflash.


Photograph of the square artifact just outside (but very closely intersecting) the laser's beam. This pic was taken by irradiating a plastic bag hanging on the doorknob in such a manner that the artifact continued unabated so that it struck a white surface behind the bag; the bag itself absorbed the vast majority of the laser's energy.


A look "under the hood" as it were; this allows you to see the laser diode itself.
It's that small silvery-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 WC 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 475nm and 495nm to pinpoint wavelength, which is 488.7nm.


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 488point.txt


Spectrographic analysis of this laser taken after ~five (5) hours of continuous operation to check for spectral drift; spectrometer's response narrowed to a band between 475nm and 495nm to pinpoint wavelength, which is 488.370nm.



The raw spectrometer data (tab-delimited that can be loaded into Excel) is at 488poin2.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 486nm and 491nm to pinpoint wavelength, which is 488.7nm..

Spectrographic data file (tab-delimited that can be loaded into Excel) is at 488nm9.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 483nm and 490nm to pinpoint wavelength, which is 487nm.

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 488cold.txt

USB2000 Spectrometer graciously donated by P.L.

Spectral line halfwidth (FWHM) of this laser was measured at 2.1nm.


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 pooped out. Notice that it blinks rapidly instead of staying in CW (Continuous Wave) mode.

The music that you hear is zax from the coin-op arcade video game, "Afterburner ][" by Sega from 1987.
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 8,713,315 bytes in size; dial-up users please be aware.



Another 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.

The music that you hear is zax called, "Narrow+" from the Commodore 64 computer demo, "Pyromania" by the C=64 demo group Arson.
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 38,816,017 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 2:22pm PDT on 08-21-18.


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


PROS:
Very unique beam color -- 488nm 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 (very dim) square visible just outside the main beam (this is a magnified image of the laser diode's substrate and would be present in most if not all units)

CONS:
No CDRH warning label on product or in packaging materials (this is what nocked that last ½ star from its rating; at least the 505nm laser *HAS* a label)


MANUFACTURER: Unknown
PRODUCT TYPE: Fat "pen"-style portable laser
LAMP TYPE: Directly-injected greenish-blue-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: 295mA
WATER-RESISTANT: Yes
SUBMERSIBLE: Yes, to 5M (~16.4')
ACCESSORIES: Dual-slot battery charger
SIZE: 193mm L x 14.50mm Dia.
WEIGHT: 164.20g (5.79 oz.) empty -- 206.50g (7.280 oz.) incl. battery
COUNTRY OF MANUFACTURE: China
WARRANTY: 1 year

PRODUCT RATING:





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

UPDATE 08-30-18: Ran a repeat long-term laser stability cum battery discharge analysis; also performed spectroscopy after ~25 mins. continuous operation to check for wavelength drift.

UPDATE 08-31-18: Performed narrowband spectroscopy at relatively cold temps to check for wavelength shift.

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

UPDATE 09-05-18: Added a photograph of this laser's radiation reflecting off of an interior window.

UPDATE 09-06-18: Added a brief video showing how this laser performs in LVC.

UPDATE 09-07-18: Added a second brief video showing how this laser performs in LVC.

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

UPDATE 09-13-18: Added a photograph showing this laser's beam crossing a room.
 
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diachi

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Another excellent review, keep it up! :beer:
 

The_LED_Museum

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Added photo of the square artifact next to the main beam (no need to add BTTT to this post) ;)
 

paul1598419

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Yes, a great review. These are more of the Sharp single mode diodes that have been released over the past year. This particular diode has a part number GH04850B2G of which I measured 20+ diodes coming in at 486nm to 493nm basically. Because this narrow part of the visible spectrum is so active, one can see a dramatic change from the lowest to the highest measured wavelengths.

There was another Sharp diode, part number GH04855A2G that measured between 492.2nm and 495.0nm from among 15 diodes tested.
 

paul1598419

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I see you have found the rectangular artifact that we get with many glass lenses. I used the acrylic lens that comes with any module you buy to eliminate it for awhile. That does work well. The artifact is worst when using short focal length single element lenses like the G-2. I purchased a half dozen of DTR's 2 element 520nm AR coated lenses after I was able to confirm it also doesn't have this artifact. I have tried every lens out there and these are the only two, to date, that eliminate it completely.
 
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The_LED_Museum

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

paul1598419

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That was pretty ballsy letting this laser run until the battery discharged. I have never tried that as I don't want to lose any of mine as I worked hard to measure as many as I did and built every one that I have. All of mine are running at 275 mA giving outputs from 120 mW to 135 mW. I know if I used a short focal length aspheric lens for my power tests they would come in higher, but I have lenses on all of mine that eliminate the rectangular artifact, so I felt that my power tests should be done with the lens I use on them.
 
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The_LED_Museum

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That was pretty ballsy letting this laser run until the battery discharged...
I monitored it very closely both for case temperature and laser output; had the case temperature risen too much or if the power output inexplicably dropped, you bet your sweet patootie that I'd have halted the test PRONTO!!!

I'm running the same analyses of the 505nm laser right now; I'm excersizing the same protocols as I did with this laser.
 

paul1598419

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You misunderstand my point. These Chinese lasers are often not directly heat sinked to the outside air, so the temperature of the host may not be a close indicator of the temperature of the diode. Mine are all copper or aluminum and are in contact with the air.
 

The_LED_Museum

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You misunderstand my point. These Chinese lasers are often not directly heat sinked to the outside air, so the temperature of the host may not be a close indicator of the temperature of the diode. Mine are all copper or aluminum and are in contact with the air.
Actually, I understood your point perfectly.

I state in my review (and I quote): "...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"."

I knew full well that heatsinking could suck going in; that's why I watched not only the case temperature but the laser's output power like a hawk -- if I saw the output power inexplicably sag, I would know that this would almost certainly be the result of poor heatsinking and I would then have terminated the test at once. :)
 

paul1598419

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These Sharp diodes are fairly resilient, so that does work in your favor. If you tried this test with a BDR-209 driven at 900 mW, the first inkling something was off would be the diode's failure.
 

The_LED_Museum

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These Sharp diodes are fairly resilient, so that does work in your favor. If you tried this test with a BDR-209 driven at 900 mW, the first inkling something was off would be the diode's failure.
That would have hella sucked; I guess random chance appears to have operated in my favour (luck was on my side) here. :D
 
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paul1598419

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Yeah, we have lost quite a few 405nm diodes around here. At least they weren't expensive diodes.
 




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