High Power Laser Delivery

Optic fiber is the channel for light transmission. When it is developed at the beginning, it is used for communication, that is, the light carries information from one side to another side.

As technology develops, the light can not only carry information, also carry energy from one to the other. When it carries high energy, we said it is high power fiber optic.

What is high power?  As we know in the fiber optic communication, the power is very low. You can see the SFP tx power is less than 10 dBm, and the VFL power is only 30mw. So usually 1W+ power is the high power, currently, the max high power can reach 20000w.

The power is generated through laser. Over their 50-year history, lasers have gone from producing powers of a few hundred watts to greater than a petawatt, or a quadrillion watts.

Laser light has four unique characteristics that differentiate it from ordinary light: these are Coherence, Directionality, Monochromatic, High intensity. These features make the laser to be a good choice for high power applications.

There are several kinds of laser device in the market.

1．Gas Laser

 The typical gas laser is CO2 laser, which with a wavelength of 9-12um (typical wavelength 10.6um) has become a most important and popular gas laser due to its high efficiency, good beam quality, large power range (a few watts to tens of thousands of watts), and its ability to be continuous and pulsed. The C0₂ laser is mainly used in material processing, scientific research, national defence and other aspects. Commonly used forms are sealed-off longitudinal electrically excited carbon dioxide laser, TEA carbon dioxide laser, axial fast flow high power carbon dioxide laser, and cross-flow high power carbon dioxide laser.

2．solid-state laser

ND-YAG laser solid-state laser, working at 1064nm,  is currently the most excellent laser crystal with comprehensive performance. The maximum output power of a continuous laser is 1000W. It is widely used in military, industrial and medical industries. If it is operated in a continuous manner, a multimode output of 400W can be obtained by using the first-stage oscillation. If a laser with an output of one hundred watts is required, a single lamp and a single rod shall be used, and a dual-lamp and single rod structure shall be used for that above 200W. Nd-YAG laser is not only suitable for continuous but also has excellent performance under high repetition frequency. The repetition frequency can reach 100-200 times/s, and the highest average power can be 400w. Multi-stage series connection is used to achieve high power output. At present, the average power can reach up to 600-800 watts, the repetition frequency can reach 80-200 times/s, and the single pulse energy can reach 80J.

3．semiconductor diode laser

The semiconductor diode laser is a device that produces stimulated emission by using a certain semiconductor material as a working substance. Its working principle is to achieve non-equilibrium loading between the energy band of semiconductor material (conduction band and valence band), or between the energy band of semiconductor material and the energy level of impurity (acceptor or donor) through a certain excitation method.

Mainly used in electronic information. Optical fiber communications, optical sensors, optical discs, laser printing, barcode scanning, integrated optics. 400-780nm applications are used for strip scanning, detection, optical storage, laser printing, etc. 790~1020nm is used in barcode scanning, laser printing, optical storage and other fields. In recent years, high-power semiconductor lasers have made great progress. The continuous output power can reach 1-20w. 1300 and 1550 respectively have zero dispersion and minimum loss windows in silicon optical fibers. The corresponding semiconductors are mainly used for long-distance large-capacity trunk optical communications. The output power of 1480, which is between 1300 and 1550, can reach 50-100mw in recent years.

4．dye laser

The outstanding advantage is that the output wavelength is tunable. It can not only obtain a tunable narrow-band high-power laser in the 0.3-1.3um spectrum, but also obtain tunable coherent light from ultraviolet to mid-infrared through mixing technology. Mainly used for spectroscopy research.

5．Fiber laser

Fiber lasers have a wide range of applications, including laser fiber communications, laser space telecommunication, industrial shipbuilding, automobile manufacturing, laser engraving, laser marking, laser cutting, printing rolls, metal and non-metal drilling/cutting/welding, military and national defence security, Medical equipment, large-scale infrastructure, etc. The advantages of miniaturization and intensiveness brought by the low manufacturing cost of glass fiber, mature technology and the flexibility of the fiber; glass fiber does not require strict phase matching like crystals for the incident pump light, which is due to the glass matrix Stark The non-uniform broadening caused by the splitting causes the absorption band to be wider. The glass material has a very low volume-to-area ratio, fast heat dissipation and low loss, so the up-conversion efficiency is high, and the laser threshold is low; the output laser wavelength is large because of the energy of rare-earth ions. The level is very rich and there are many kinds of rare earth ions; the tunability is due to the wide energy level of the rare-earth ions and the broad fluorescence spectrum of the glass fiber. Since the fiber laser has no optical lens in the resonant cavity, it has the advantages of adjustment-free, maintenance-free, and high stability, which is unmatched by traditional lasers. The fiber export makes the laser capable of various three-dimensional arbitrary space processing applications easily, making the design of the mechanical system abundant and simple. Competent in the harsh working environment, with high tolerance to dust, shock, impact, humidity and temperature. No need for thermoelectric cooling and water cooling, just simple air cooling. High electro-optical efficiency The comprehensive electro-optical efficiency is as high as 20% or more, which greatly saves power consumption during work and saves operating costs. With high power, the current commercial fiber laser can reach six dry watts.

The laser was generated in the device, then how to transmit to the destination point.

Fiber is the best choice.  Fiber has good flexibility and high transmission efficiency.

There are two kinds of fiber available for high power transmission. SI(step-index) and GI(Graded Index). The core diameter is 50um~1500um.

SI fiber is suitable for laser welding thin metal plane while GI fiber is good at laser welding thick metal.

The most popular interface for high power is SMA905 and D80.