Multi-Emitter Fiber Coupling Diode Laser Construction
Time2020-3-23 15:03:00 visits：
1.Multi-emitter structure Multi-emitter structure is to shape, re-arrange, and combine the beams emitted by semiconductor lasers into a single optical fiber, thereby increasing the output power of the laser. Because discrete semiconductor laser chips must be mounted on a heat sink with a certain size, if the output beams of multiple semiconductor lasers are directly aligned and focused, coupling is usually limited by the volume of each chip and its heat sink. It is difficult to obtain high-fiber coupling output with small core diameter. In order to reduce the volume of the combined beam, certain measures must be taken. To this end, the multi-emitter structure is developed.Using a stepped heat sink, a focusing lens, a coupling fiber, and a unique installation method. The optical path design simplifies the complexity of the structure, reduces the volume of the component, and greatly improves the output power of the laser, while ensuring a reasonable operating temperature, as shown below:
The aging and screening test for every single laser chip can be performed before coupling to ensure the reliability. The random failure characteristics of a single tube are independent. Compared with Bar bars and stacked arrays, which have no thermal effect interference, the replacement of a single tube also increases its durability and has a higher cost advantage.
In order to achieve high brightness and high power output, the number of single-coupled semiconductor lasers can be increased at the same time to ensure high output power, but three conditions must be met to couple the combined laser beam into a single fiber: one is the light spot The largest diameter is smaller than the core diameter of the fiber; the second is that the divergence angle of the beam is smaller than the angle corresponding to the numerical aperture of the fiber; the third is the beam parameter product of the fast and slow axes is less than Fiber beam parameter product(BPP, the product of the beam waist radius and the half angle of the divergence angle).
However, in practical applications, only the square area in the center of the fiber is an available area, as shown below:
Fiber usable area when fiber is coupled
For a fiber with a core diameter of 200 μm and a numerical aperture of 0.22, its BPP value is 22 mm mad, and the maximum BPP of a semiconductor laser beam that can be coupled is:
Taking the laser beam data output from a single chip of a 9xxnm semiconductor laser as an example, the diameter of the slow-axis beam waist is 95 μm and the half-angle of the divergence angle is 10 ° (99% of energy). 1.5μm, divergence angle 39 ° (99%), beam parameter product is about 0.51mm mrad. After software simulation, theoretically, 28 laser beams can be coupled in a 200 μm / 0.22 NA optical fiber. At present, after years of technical accumulation, BrandNew 9xxnm high-brightness fiber-coupled semiconductor lasers can be coupled to a maximum of 20 semiconductor lasers.