Blue Lasers Based on Semiconductor Laser Diodes

What is a Blue Laser?


A blue laser is a light emitting device that emits a light beam in the wavelength range between 400 nm and 500 nm. It is a coherent beam of light, consisting of a single wavelength and has applications in numerous fields. Different blue lasers are predominantly based on different gain media and their properties.

Blue lasers originally came into existence as a laboratory curiosity and were based on a helium-cadmium, argon or krypton gas. At that point, blue lasers were capable of lasing only 130 mW of optical power, while wasting a kilowatt of energy in the form of heat. Nevertheless, the situation changed with the discovery of edge emitting blue semiconductor laser diodes. Soon after, it was evident that blue lasers could potentially feature favourable electrical to optical power conversion.

The appearance of Blu-Ray technology and high-power projectors created the very first major market for blue laser diodes. This accelerated the development of new and improved varieties of blue laser diodes. Although blue lasing is achievable with miscellaneous types of lasers (such as ion lasers, dye lasers, semiconductor laser  diodes and diode-pumped solid state lasers [DPSS]), it is semiconductor blue laser diodes that are dominating the market. This is due to the uniformly good optical efficiencies of blue laser diodes, typically of the order of 50%, but sometimes 60 or even 70%, being second only to Yb:YAG thin disc lasers that were shown to reach 77% efficiency. Yb:YAG lasers typically lase in the IR, at 1030 nm and 1050 nm, with well above 1 kW diffraction-limited output with high beam quality, and even greater powers with non-diffraction-limited quality of the beam. Nevertheless, unlike blue laser diodes, Yb:YAG lasers are quite bulky and costly. Furthermore, it is advantageous to use a blue laser instead of an IR (or CO2) one, as a result of a smaller beam waist, high reliability and the possibility to efficiently process various metals, such as, for example, copper. Interestingly, copper can only absorb 5% of the incident IR light, but 65% of the incident blue laser light at room temperature.



The Competitive Edge of Blue Semiconductor Laser Diodes


Generally, blue lasers are typically sold in the form of blue semiconductor laser diodes with different substrates involved. The substrate of choice sets the intrinsic properties of the blue laser beam produced. Every blue laser diode has a slightly different divergence, wavelength, operating current and efficiency. For instance, InGaN blue lasers with a GaN substrate, lasing at 445-450 nm, are immensely popular thanks to their compact size, great cost-efficiency, wide range of applications, operating temperatures up to 65°C and an ever-improving performance. A single blue  semiconductor laser diode can achieve a power up to 6W. An example of such a diode is NUBM44, which is offered by Opt Lasers in our laser heads. It boasts an unprecedented 20 000 hours operating lifetime and is the highest power blue laser diode available on the market. Recently, companies such as OSRAM and Sharp, have also developed 5W blue laser diodes, which offer a competitive edge.

Significantly, blue laser diodes can operate in relatively high operating temperatures while keeping their long lifetime. Moreover, the output power achievable by the blue laser diodes is significantly higher compared to other laser diodes from the visible spectrum. In addition to that, due to diffraction limitations, blue laser diodes can focus the beam into a smaller beam waist compared to near-IR and IR lasers. Finally, thanks to the boom for blue laser diodes in the blue-ray, automotive and projector industry, the recent generations of blue laser diodes have become remarkably inexpensive and cost-efficient. As a result, blue semiconductor laser diodes have become well-known for their robustness, reliability, cost-efficiency and high output power density.

Nevertheless, the price for robustness, cost-efficiency and reliability is paid in the beam quality, which is lower for blue laser diodes than for other alternatives. What’s more, the blue laser diode emitter is in a single mode in one axis and in a multimode in the other one, resulting in a rectangular-elliptical shape of the beam waist. Also, the divergence in one of the axes is a few times higher than in the other. Consequently, the engineering of a laser system might prove a challenge as every axis needs to be analyzed and designed separately. Thankfully, Opt Lasers offers professionally designed blue laser heads that utilize blue laser diodes that can save you all the trouble. Furthermore, as more complex systems require selecting the right laser diodes, our team is here to answer all your questions and can even build a customized design of your choice in as little as 5 weeks.



Blue Laser Diodes vs IR Lasers


While blue laser diodes have smaller (rectangular) beam waists compared to IR lasers (which have circular beam waists), they feature much higher power density. Furthermore, even though a blue laser diode's beam spot is smaller in one dimension than in gas lasers, the beam can be used much more effectively. This is due to the blue laser’s light beam’s power density and high absorption rate. It is a huge advantage in case of many engraving applications. Depending on the axes’ choice, you can achieve either wider engravement or a deeper and narrower one if the outline for the engravement is rotated by 90 degrees. Blue lasers can effectively process a wide range of materials, such as titanium, copper, or gold, as well as natural materials like wood.

Blue Laser Absorption Characteristics

For instance, as shown in the graph above, the 445 nm (0.445 um) blue laser diode features significantly higher absorption rate than Nd:YAG (1064 nm) and CO2 (10600 nm) lasers. At the same time, blue lasers are capable of achieving 50% higher power density. This means a blue laser can discharge between several and almost 20 times more energy at the illuminated material at the same power level compared to CO2 and Nd:YAG lasers.

Opt Lasers' uSpot Blue Laser HeadTop Manufacturer's Nd:YAG LaserTop Manufacturer's Yb:YAG LaserTypical CO2 Laser Head
Wavelength [nm] 445 1064 1030 10600
Average Power [W] 6 25 140 75
Beam Wiast Size [cm] 0.0219 x 0.0004 0.135 0.0656 0.236
Average Power Density [kW/cm2] 680 0.434 10.36 430
Peak (Pulse) Power [kW] N/A 2083 11667 N/A
Peak Power Density 680 2448 28317 N/A
Absorption on Copper [%] 65 5 5 <1
Absorbed Power Density of Copper [kW/cm2] 442 0.0217 0.518 N/A
Lifetime [h] 30 000 833 830 (lamp) 2 000
Visibility Visible Invisible Invisible Invisible

Dimensions [cm]

4 x 5.5 x 10.5 30.6 x 50.8 117.2 20.5 x 36.9 x 100.3 4 x 6 x 16.6
Unit Weight [kg] 0.22 84 70 1
Price [thousands of USD] 1 100 100 1.5
Cost per kW of Average Power [k$] 166.7 4000 714.3 3.18
Cost per kW of Peak Power [k$]  166.7 0.048 0.0086 3.18
Cost per kW of Power Density [$] 1.47 230629 9648 2.6
Cost per kW of Peak Power Density [$] 1.47 40.9 3.53 2.6
Cost per kW of Absorbed Peak Power Density on Copper [$] 2.3 817.2 70.6 N/A



Fiber-coupled Blue Lasers


A blue laser beam can also be modified by coupling the output beam produced by a laser diode into an optical fiber with an aspherical lens between them. This kind of system is called a fiber-coupled (or fiber-integrated) diode laser and it does have several advantages over alternative solutions:

  1. Fiber-coupled blue diode lasers have a good beam waist quality. The blue laser beam waist is symmetrical, homogenous and circular.
  2. Fiber optics can easily be installed on many CNC machines.
  3. It doesn’t inhibit the high-speed operation of the CNC machine since the fiber is lightweight.

Consequently, this makes fiber-coupled blue laser systems an interesting option for material processing techniques such as cutting and engraving.



Blue Lasers Applications


From the point of view of applications of blue laser diodes in photonics, they are profoundly convenient devices due to their practical scope of output powers and easy modulation with high-frequency control current. Applications of blue laser diodes include, among other things, pumping solid state lasers, quantum dots or single quantum emitters (SQEs), laser microscopy, spectroscopy, surface scanning, laser printing, sensors and pumping RBG sources (such as phosphor). For instance, using blue laser sensors is advantageous as they perform better on highly polished and gloss surfaces thanks to their shorter wavelength. By contrast, red light gets distorted by such surfaces, which results in a ‘speckle’ effect. That causes a detector to encounter elevated signal noise, which translates to lowered measurement accuracy. On the other hand, a blue laser sensor can perform extraordinarily efficiently with notably lower amount of speckling. As such, using a blue laser results in lowered noise levels, normally by a factor of two to three as opposed to red laser sensors.

Furthermore, blue lasers can also be used in the textile industry for rapid cutting, decoration and personalization of fabrics such as cotton, polyester, viscose, felt, fleece, leather, upholstery and fiberglass fabrics, among other possibilities. What is more, blue lasers make an excellent and captivating choice for laser shows.
 
Medicine is also known for making an extensive use of blue lasers. The majority of titanium elements placed in a human body during surgeries is marked with blue lasers. Additionally, blue lasers are used as an illumination source in fluorescence  microscopy.
 
On top of that, industrial applications such as heating up materials, cutting and welding benefit from good power absorption. Materials such as titanium, copper or gold are able to absorb about 65-80% energy from a blue laser. This is particularly useful in case of welding, since the low absorption of an IR laser (5%) would lead to a heightened amount of defects across the processed chunks of metal. Conversely, blue lasers are highly apt for situations where thin metals are to be swiftly and reliably joined with little to no defects. The high blue laser beam absorption rate is also capable of speeding up the assemble rate for additive manufacturing for both laser metal deposition and powder bed growth methods. While this depends on the material used, one can expect a speed increase by a factor of three to ten by adopting blue lasers. Besides that, the small focus spot size of a blue laser leads to two additional benefits. First of all, for a set optical system, the beam waist of a 450 nm beam of light is less than half that of a corresponding beam waist of a 1080 nm beam. Thus, using a blue laser beam can improve the feature scaling ability, resolution and precision of the finished product. Moreover, if the same resolution that is possible with an IR beam is applied, a blue laser can supply the same resolution, but for an area four times as large. Clearly, the outstanding potential improvement of manufacturing quality and processing speed can be highly opportune.
 
All in all, blue laser systems are proving very popular with a plentiful amount of tangible applications. They are robust, reliable, time-efficient and cost-effective, just like our PLH3D-6W u-Spot laser head:
 

  • $999.00 In stock

    The youngest and most precise member of our PLH3D family of laser heads. A higher optical performance and energy density with a smaller spot size (compared to other 6 W lasers) gives this laser head faster engraving speeds and allows for the cutting of thin materials like ...

    $999.00
    PCS Add to cart
    In stock

 If you require a higher operating power, we strongly suggest looking at our PLH-12000 Blue Laser Head:
 
  • $1,098.00 $1,220.00 -$122.00 In stock
    Sale!

    This is the PLH - 12000 high-power (12 W) professional engraving laser head with a PLHD-12000 driver, thermal protection and PSU.

    $1,098.00 $1,220.00 -$122.00
    PCS Add to cart
    In stock

 However, if you just want to purchase your first engraving head, you may want to try our Prusa Laser Upgrade Bundle, which includes a 2W blue laser engraving head:

  • $199.00 $359.00 -$160.00 In stock
    Reduced price!

    This kit includes all of the necessary attachments to laser engrave with your Prusa i3 MK3S 3D printer. It includes a PLH3D-2W Laser Head, with which you can equip your Prusa 3D printer with a low-cost laser engraving and cutting module. This engraving laser upgrade kit for ...

    $199.00 $359.00 -$160.00
    SET Add to cart
    In stock

 If you have any questions or would like to discuss an idea for a customized laser head, please feel free to reach out to us. Opt Lasers is a proud Open End Manufacturer that can turn your idea into a ready product in as little as 5 weeks.