Welcome to Laser Pointer Forums - discuss green laser pointers, blue laser pointers, and all types of lasers

LPF Donation via Stripe | LPF Donation - Other Methods

Links below open in new window

ArcticMyst Security by Avery

using an heat lamp to heat a copper laser submount

Joined
Sep 23, 2011
Messages
2
Points
0
Hi,

I am trying to build a stage for my laser diodes that will operate at up to 300 Celsius. I would like to use a halogen bulb (and place in a hollowed out copper block) to quickly heat up and cool down the metal ( because I need to be able to take measurements from 20 Celsius to a very high (>200 Celsius).

has anyone here ever tried to do such a thing?

any suggestion would be appreciative, thanks!
 





JLSE

1
Joined
Dec 13, 2007
Messages
3,580
Points
0
Arent the die's on most LD's bonded with indium? If its the case
for the diodes you're using, 300 Celsius may be an issue..
 

Opcom

0
Joined
Oct 19, 2011
Messages
20
Points
0
A lamp is workable but choose it carefully so it can itself do without cooling air. The heating will be slow.

A useful technique for quickly heating your device and avoiding the thermal inertia of a block of metal would be to use a 0.001 to 0.01" thick strip of perhaps copper, or another metal of your own choice that won't reduce or melt with heat, with a cutout for your laser diode's flanges to be mounted to, perhaps with a thin ring clamp top and bottom and very small screws. I say clamp because a solder with a high enough melting point may be too hot the the diode's internal construction materials (as pointed out above). I faced this sort of thing working with down-hole companies and that is one reason they often prefer to buy dice and do their own assembly. A high resistance metal is better because it will take more voltage and less current. Even so, 100-400 Amps of DC current is called for.

Anyway, pass a large current through the copper strip to heat it. A blower could cool it fairly quickly if needed. The thinner the material, the less current required for a given temperature rise. The thicker the material, the more uniform the temperature in the region around the diode. Consider that the case temperature of the diode might not be completely uniform due to radiation and convection.

To make the current, consider a large transformer, 1-3KVA. It is possible to wind 1-2 turns of bus bar and there you have more amps than you need. rectify, filter.. Or use an old fashioned carbon pile and a 2V industrial wet cell such as an old telco battery, or a 6V automotive battery.

Best practice would be to avoid passing current through the metal case/body of the diode. Meaning insulating it electrically and not thermally. At those temperatures it will require a little more work. perhaps a BeO or alumina heat sink insulator, but they are difficult to machine (BeO dust is very hazardous) and not usually found in the right size, most commonly for TO-220 and TO-3, and some newer semiconductor cases. Anyway, find a material for insulating transistor cases from heatsinks yet encourages thermal transfer, that will stand your temperatures. Even so, it might not harm anything to allow some incidental current to pass through the mounting flange as long as the current loops are kept separate.

Thin clamping and tiny hardware to reduce thermal inertia and uneven heating. While you are at it, a slight deformity or a tab in the clamp could hold the thermistor or whatever you are using to measure the laser body temperature.

Regulate the current to help regulate the temperature. Thin metal strips may deform and move about as heated so you may wish to mount the laser itself with ceramic or something that won't suck the heat away but will hold the laser in place well, and use flexible leads such as a fanned out welding cable or even a couple of braids from RG-8 cable to deliver the current to the metal strip.

There are several manufacturers of refractory ceramics that could supply the mounting material, some of which can even be drilled carefully. I assume no responsibility for destructive play.

I was at a solar technology trade show and stopped at the ZRCI booth. Their array of materials and possible shapes was impressive. I was kindly given a piece of silica-based RSLE-57 good to 1100 dec C that I want to try as a beam stop. Its pretty dense but some of the ceramic fiber based materials they supply might be better for your project. Some of the materials are machinable. zrci.com
 
Joined
Dec 29, 2009
Messages
3,136
Points
63
Retarded Posts
^ says the kettle...


What about using power resistors like these:
Aluminum-Cased-Power-Resistor-GR-Series-.jpg
 
Last edited:

Opcom

0
Joined
Oct 19, 2011
Messages
20
Points
0
^ says the kettle...


What about using power resistors like these:
Aluminum-Cased-Power-Resistor-GR-Series-.jpg

What is the temperature rating of those resistors? I think nowhere near the goal. This goal temperature seems unusual. Is the expected result worth what it will cost to do it?
 
Last edited:
Joined
Dec 29, 2009
Messages
3,136
Points
63
Usually these types are wirewound resistors with an aluminum casing. According to a certain encyclopedia-ish source (wiki ;) ), "these (wirewound) resistors can withstand temperatures of up to +450 °C"

Doesn't always mean that they can generate those temperatures, but that's what wiki says. You may pull whatever you want from that wording ;-)

Those particular ones were just what google image search pulled up, but I think generally speaking high wattage resistors with aluminum sinks are wirewound.
 
Last edited:

Opcom

0
Joined
Oct 19, 2011
Messages
20
Points
0
Most of the ones like that i have used are made with a filler in the ends that looks like an epoxy or plastic. Might make a good smell.

It might be as well to strip an old space heater for the nichrome wire, rewind it on a ceramic sheet and use radiant heat to boil up the diode.

The lamp idea is good, but something tells me it is not safe. Can't think of why at the moment.
 
Joined
Sep 23, 2011
Messages
2
Points
0
sorry cyparagon, and others i stopped getting the notifications somehow for this thread.

So to be more precise, the type of laser i'm using is a semiconductor laser (non packaged) which typically has a small footprint about say a 1 mm^2 .

I mount the device to a piece of Au electroplated copper using epoxy that can handle high temperatures (up to about 190 C I believe Silver Epoxy works to before it boils). As of now i've gotten to 160 C using an external heating element (heater tape) and a variable transformer. but it's slow because my heat insulation is poor (and can improve).

I've been talking a few companies about thermoelectric coolers, but nearly all of them fail at 150-225 Celsius (depending on the TEC characteristics) due to the internal solder used.

I appreciate your guys's comments. I am also apprehensive about the lamp idea, as it's not mine and it's a person who has done it before in another context.
 




Top