637 nm Red Guidesman - 201mW Build

[chipdouglas]

the 635's get away from 635nm really quick. there isn't much of a power band that can still lase at 635.

michael

 

[jakeGT]

He wanted to reach 200mW with this diode I do believe. 635nm or 642-650nm

Same thing with the HL6338 diode he wanted to purchase, he wanted to start low, and then push it for power,

I am going to get one of these HL63133DG diodes, and keep it at 300mA, operating current to max is 250-320. So 300mA, with a nice big heatsink on both driver and diode, should keep it at a lower wavelength, is my hopes.

 

[rhd]

^ More or less, yep.

Really, my objective wasn't to obtain any particular wavelength, but rather to obtain the most visible red beam possible. There's obviously a tradeoff in that the higher mW you push, generally, the higher red wavelengths become as a result of heat. But this guy doesn't really get warm, noticeably, at all. So I think that when they talk about the wavelength increase as this heats up, the necessary heat is only going to come into play when you have this diode running for quite a long period of time constant. IE, closer to an hour +.

Though it would be hard to notice a 5nm wavelength shift by colour, it would be relatively easier to notice the shift based on perceived brightness. A 170mw 637 would actually be much brighter than a 200mW 642 (if it really reached 642) Beam: (642nm 200mw) vs. (637nm 170mw) However, that just wasn't the case. The 200mW was noticeably brighter than the 170mW power range. Coupled with my observation that this just doesn't produce much (any) measurable heat in a few minutes of use, and the fact that most datasheets correlate wavelength to temperature not mW optical output, I've come to the conclusion that it isn't shifting wavelengths much (if at all) based on my use.

 

[steviedezie]

thats a nifty program rhd...it gives a good way to calculate apparent brightness. it seems a 300mw 660nm laser would be much brighter than my 800mw 405... by a lot too. thats cool nice work. +1 for that

 

[DJNY]

thats a nifty program rhd...it gives a good way to calculate apparent brightness. it seems a 300mw 660nm laser would be much brighter than my 800mw 405... by a lot too. thats cool nice work. +1 for that

And you needed a calculator for that?


Edit: Sorry, didn´t consider that you may haven´t seen a 300mW red before

 

[rhd]

Thanks stevie. That program has evolved a bunch over time too. The next thing I want to do is make it selectable by day/night vision.

Then once I have day vs night, and beam vs dot, I want to create an "overall" brightness perception mode that synthesizes all 4 possible figures into one indication of all around averaged comparison.

 

[jakeGT]

It says 150mW of 635 should be brighter than 200mW of 642

I think I may try mine at 250mA, and at 320mA, and see which seems brighter

 

[rhd]

It says 150mW of 635 should be brighter than 200mW of 642

I think I may try mine at 250mA, and at 320mA, and see which seems brighter

It should be.

And I already know the answer

No contest, as this diode increased in power, its visibility did too - which is why I'm left believing that the wavelength drift is more of a long term issue, as these diodes are used commercially/industrially in constant on, for long periods of time.

 

[RA_pierce]

A 170mw 637 would actually be much brighter than a 200mW 642 (if it really reached 642) Beam: (642nm 200mw) vs. (637nm 170mw) However, that just wasn't the case. The 200mW was noticeably brighter than the 170mW power range.

Interesting. I find it hard to believe that 200mW is perceptibly brighter than 170mW considering it is a difference of only 30mW or 15% of 200mW.
The difference between 170mW and 200mW of 532nm is hardly noticeable and there is almost no visible difference between 200mW and 300mW of 650nm.
But hey, I've never seen one of these diodes myself...

Coupled with my observation that this just doesn't produce much (any) measurable heat in a few minutes of use, and the fact that most datasheets correlate wavelength to temperature not mW optical output, I've come to the conclusion that it isn't shifting wavelengths much (if at all) based on my use.

I've seen quite a few data sheets that correlate wavelength with temperature and output power.
For example, the 40mW 635nm we found some time ago.
The data sheet specifies that the diode lases at 635nm at 0C.
It also specifies that at 25C and at only 10mW the diode lases at 640nm.
Even most of the 635nm 5mW diodes don't even lase at 635nm. If you've ever seen a HeNe and compared a 5mW 635nm pointer to it, there is absolutely a difference- although, when the 635nm pointer is stuck in a freezer for a few minutes, the beam becomes much closer to the HeNe.

Also, the wavelength shift is not necessarily dependent on the heat that the diode produces but the temperature that the diode is running at. As I stated above, most (if not all) "635nm" diodes lase at 635nm only when they are near 0C-10C.

I would say that beyond a doubt that this diode shifts in wavelength with temperature and output power whether you can perceive it or not.
I don't mean to burst your bubble but everything I have read and seen tells me that at 200mW & room temperature, your diode is probably closer to 645nm than 637nm.

 

[steviedezie]

only a spectrograph can tell you how far your 635 has shifted when driven to 200mW. I wish I was still in college...theres so many lab stuff there to play with after class...

 

[rhd]

RA:
I had fog in the air, and I was paying close attention to brightness. I also had the laser next to a constant - a 275mW LOC. That also facilitated comparison.

I love the fact that there is so much doubt here Grab one of these diodes and give it a shot yourself. I can only relay my observations, if you want to challenge the technical side of that, it's cool with me - but my eyes are still my eyes - and it's pretty easy to tell when one beam is brighter than another, especially when you've got the subject beam next to a constant.

And where are you getting your data from? You realize that this *isn't* the 40mW eBay diode right? This is the Opnext HL63133DG.

You've mentioned lasing at 640... that just doesn't compute with me. The datasheet on these gives a range of 632 to 643, with 637 being the typical.

You've also suggested that at 200mW this should be lasing closer to 645nm. At 200mW of 645nm, you'd be looking at a beam roughly comparable with 430mW of LOC (658nm). That's just plainly not the case. Putting this guy next to a 330mW LOC, there's absolutely no similarity to their intensity. They're not ballpark the same visibility.. This second photo here is the best illustration. A 275mw LOC next to this guy. If this guy was 200mW of 645, which would roughly equate to 430mW of LOC, then my eyes (or my camera are broken). No way on earth 275 vs 430 looks that clearly different.

 

[DJNY]

rhd, I donate $3 to you if you send it to aryntha/LED_Museum. They both have a spectrometer.

Anyone else want to help?

 

[Prototype]

I didn't think aryntha had a spectrometer? I know Cyparagon does, and he's been active more recently than LED_Museum, so he's a viable choice simply because LED might be harder to contact.

 

[RA_pierce]

I did check the data sheet for this Opnext diode.
I read: Min: 632nm, Typ: 637nm, Max: 643nm.
But these specs are for Po = 170mW.
Also, I said, "Closer to 645nm." I didn't imply that it is 645nm.

The 640nm figure comes from the Sanyo 40mW diode data provided as reference since the Opnext data sheet for this diode does not include a graph (unfortunately). And why can't this diode lase at 640nm? After all, it is in the range of 632-643nm, isn't it?

I am not trying to tell you what wavelength this particular diode is lasing at. I am only pointing out that this diode does shift in wavelength in relation to the operating temperature and increased output power.
How much or how little can only be determined with a spectrometer.

 

[Cyparagon]

Yeah, I check the forums once or thrice a day. I'll put it on the spectrometer if you pay shipping.

It has been my experience that 635s are only 635 if they are 1: low power, or 2: very cold (20F or so).

 

[Trevor]

Really cool build, but you didn't talk about the most interesting part: the TEC regulating the temperature of the laser diode! Impressive how you managed to fit it in such a small build.

Special consideration: Is your LOC really 658nm? It's being run at something like 2x rated pulsed power.

-Trevor