In previous attempts to write ultra-fast laser pointer in silicon, the problem that femtosecond lasers cannot structurally process bulk silicon has been broken. The use of extreme NA values allows laser pulses to achieve sufficient ionization to destroy chemical bonds in silicon. Causes permanent structural changes in silicon materials.
Since the late 1990s, researchers have been writing ultrashort pulses of femtosecond lasers into bulk materials with wide band gaps, which are often insulators. But so far, for materials with narrow band gaps, such as silicon and other semiconductor materials, precision ultrafast laser writing has not been possible. People have been working to create more conditions for the application of 3D laser writing in silicon photonics and the study of new physical phenomena in semiconductors, thereby expanding the huge market for silicon applications.
In this experiment, scientists found that femtosecond lasers cannot structurally process bulk silicon even if they increase the laser energy to the technical maximum pulse intensity. However, when replacing a femtosecond laser with an ultrafast green laser pointer, there is no physical limitation in the operation of the induced bulk silicon structure. They also found that laser energy must be transmitted through the medium in a fast manner to minimize the loss of non-linear absorption. The original problem encountered in the previous work originated from the small numerical aperture (NA) of the laser, which is the range of angles that the laser can project when focused. Researchers have solved the numerical aperture problem by using silicon balls as a solid immersion medium. When the laser is focused at the center of the sphere, the silicon sphere completely suppresses refraction and greatly increases the numerical aperture, thereby solving the problem of writing silicon photons.
In fact, in silicon photonic applications, performing 3D laser writing may significantly change the design and preparation methods in the field of silicon photonics. Silicon photonics is regarded as the next revolution in microelectronics, affecting Laser Engraver‘s final data processing speed at the chip level. The development of this 3D laser writing technology opens the door to a new world for microelectronics.