Semiconductor laser chip
A laser diode chip is a semiconductor-based laser that consists of a P-N structure and is powered by current. The laser diode package is a complete device that is assembled and packaged together in a sealed package housing to form a semiconductor laser chip that emits coherent light, a monitoring photodiode chip for feedback control of power output, a temperature sensor chip for temperature monitoring, or an optical lens for laser collimation.
The semiconductor materials used to make light-emitting P-N junction diodes today are: gallium arsenide, indium phosphide, gallium antimonide, and gallium nitride.
In order to protect the laser diode material or any laser device from any mechanical and thermal stress, almost every diode laser or any other laser device requires laser packaging, because laser materials such as gallium arsenide are very fragile. You can imagine the laser diode as a pizza, then the package base acts as a pizza box, and the pizza (i.e. laser diode) is placed inside. In addition, the sealed packaging method prevents dust or other contaminants from entering the laser; smoke, dust or oil can cause immediate or permanent damage to the laser. Most importantly, with the advancement of technology, the emergence of high-power diode lasers requires sophisticated packaging design to help dissipate the heat generated during operation through the base and the installed heat sink. Semiconductor laser chips are packaged in a variety of forms, and different packaging methods are suitable for different application scenarios to meet specific performance requirements, heat dissipation needs and cost considerations.
TO (Transistor Outline) package
This is a very traditional packaging form, widely used in various electronic components, including semiconductor lasers. The TO package usually has a metal shell that can provide good thermal conductivity and is suitable for scenarios that require good heat dissipation. Common models include TO-39, TO-56, etc. The laser in Figure 2 below is directly packaged inside the TO tube shell, and the output light power is monitored by the photodetector PD behind the laser. The heat of the laser is directly guided out of the tube shell through the heat sink for heat dissipation, and no temperature control is required.
Butterfly package
The butterfly package is a standard package for optical communication transmission and laser pump diodes. It is a typical 14-pin butterfly package, in which the laser chip is located on an aluminum nitride (AlN) base. The AlN base is mounted on a thermoelectric cooler (TEC), which is connected to a substrate made of copper tungsten (CuW), Kovar or copper molybdenum (CuMo).
The butterfly package structure has a large internal space, which makes it easy to mount the semiconductor thermoelectric cooler, thereby realizing the corresponding temperature control function. The related laser chips, lenses and other components are easy to layout inside the body, making the laser structure more compact and reasonable. The tube legs are distributed on both sides, which makes it easy to connect and control with external circuits. These advantages make it applicable to more types of lasers.