Diode lasers have become quite popular last decade.

The reason is simple – the technology is not that easy to manufacture a laser diode. And even now there are just a few suppliers who make high quality laser diodes at the moment.

One of it is NICHIA (Japan).

The quality is an essential for all laser types but when we talk about laser diodes they have a multi layer structure in a VERY SMALL piece that makes manufacturing process uneasy.

Structure of a laser diode

If you take a look at wiki diagram you will notice that multi-layer system is quite complexed https://upload.wikimedia.org/wikipedia/commons/thumb/c/c6/Simple_sch_laser_diode.svg/800px-Simple_sch_laser_diode.svg.png

The big problem and a certain limitation is a heat conductivity. While a laser diode generates photons (light) it create a lot of heat as well, so that heat has to be distributed and that is why there are not so many powerful laser diodes on the market. The max by NICHIA NUBM44 / 47 has only 7 watt optical power output in CW mode.

Of course, you can run it up to 10 watt in impulse mode but that is almost its physical limit.

Applications of laser diodes

The most common application for laser diode depends on a wavelength. For example 808 nm is commonly used for pumping DPSS (Diode-pumped solid-state) laser modules on Nd:YAG crystals. A lot of laser diodes are used in LED projectors.

There is a big application field of a spectrography as well as medicine.

On research gate portal https://www.researchgate.net/ you can find a lot if interesting research papers where scientists publish articles and white papers.

Advantage

The biggest advantage for a laser diodes is their size. For example 7 watt NUBM44 from NICHIA  is only 9 mm. For example if you want to get 10 watt out of Nd:YAG you have to build a pretty big and complexed machine that is why diode lasers are getting more and more popular.

Disadvantage

One of the biggest disadvantage of a diode laser is a beam quality. Most of quite powerful laser diodes with optical power more than 1000 mW (1W) have a pretty low beam quality that make it difficult to focus.  For example, a single-mode radiation you can focus as small as a wavelength but you have a multi-mode radiation then it might be quite tricky to focus to a really tiny spot.

CW vs. impulse mode

Many laser diodes work great in CW mode. For some applications that is very necessary. While total power can reach a few watts an energy of a single pulse is very tiny.

Laser engraving and cutting abilities

Some powerful lasers in 405 / 445 nm wavelength became quite popular tools for engraving and cutting among makers and hobbyists.

The thing is that with 5-7 watt optical laser power you can easily cut up to 8 mm of acrylic and 6 mm of wood and plywood  https://www.youtube.com/watch?v=7wN1fUY6KKE

http://endurancelasers.com/all-you-need-to-know-about-wood-and-plywood-laser-cutting/

For better engraving and cutting process you can use and air pump with an air assist and get a pretty decent results.

The good thing about diode laser that it is quite affordable tool and can be installed on almost any 3D printer or a CNC router. There are a few companies that provide a pretty reliable and endurable laser tools but stay away from Chinese fake lasers. They will not give you anything but bad emotions and full disappointment https://endurancelasers.com/my-experience-with-non-branded-chinese-made-lasers/ First of all because of a 0 support.

If you are an experienced  electrical engineer or you have plenty of time you can build you own laser based on an open-source technology.

https://endurancelasers.com/diy-laser-kit/

In general diode lasers are quite universal and can be applied for engraving and cutting almost all materials except transparent and metallic.

The thing is that for metal cutting you need high pulse energy that is impossible to get in a CW mode that is why for metal cutting mostly used high power Co2, Fiber or DPSS laser modules.

Co2 vs. diode

Learn more about it >>> https://endurancelasers.com/diode-lasers-vs-co2-laser-tubes/

Interesting facts.

Do you know that?! 10 watt diode laser 445 nm wavelength

The amount of photons: 2.24 x 10^19

Total momentum: 2.24 x 10(^19) x 1.48 x 10(^-33)=  3,31 x 10(^-14)

Pulse energy in 1ms duration = 10/1000 = 0.01J

Pulse energy in 1uM = 10/1*10^6 = 0.01mJ

Pulse energy in 1ns 10/1*10^9 = 0.01uJ

Force created = 10000 / 299 720 000 = 3.335*10^-5 N

Pressure created = 3.335*10^-5 / (100*100 uM minimum laser spot) 10*10^-10 =  333kPa

A video footage explaining how the diode lasers works

https://www.youtube.com/watch?v=b1glooiyUq4

About diode lasers applications >>> https://endurancelasers.com/about-some-interesting-applications-of-diode-lasers/

More about diode lasers >>> https://endurancelasers.com/about-diode-solid-state-lasers/

Explore about different types of lasers >>> https://endurancelasers.com/comparison-of-a-different-types-of-lasers-and-different-wavelength/