Prof. Wu Xiang, Prof. Lu Ming, and Department of Light Sources and Lighting Engineering Associate Professor Zhang Shuyu from the Department of Light Science and Engineering at Fudan University have successfully developed the world's first all-silicon laser based on the high-gain silicon nanocrystalline film developed. This result was recently reported by Science Bulletin in the form of a bulletin.
(a) Optical pumping and emission diagrams for DFB-all-silicon lasers; Inset: Photographs of DFB laser devices; (b) Variation of PL spectra of samples with pump power; Background: Cross-sectional SEM images of DFB structures
Integrated silicon optoelectronics combines the best of today's two pillar industries - microelectronics and optoelectronics - and is expected to bring new technological revolutions in communications, sensing, lighting, display, imaging, and detection.
Silicon lasers are the key to implementing integrated silicon optoelectronics. Due to the indirect bandgap structure of silicon, the optical gain of silicon is still 1-2 orders of magnitude larger than that of the conventional III-V laser material. In order to avoid this bottleneck, the mature III-V lasers are prepared on the silicon substrate in the world and become a hybrid silicon-based laser. The all-silicon laser with silicon itself as the gain medium can better match the existing silicon process, greatly improving the reliability of the device, and its development is not only a scientific and technical challenge, but also a necessity for integrating silicon optoelectronics.
In order to significantly increase the optical gain of silicon, the cooperation team of Prof. Wu Xiang, Prof. Lu Ming and Associate Professor Zhang Shuyu of Fudan University first learned and developed a high-density silicon nanocrystalline film growth technology, thereby significantly improving the luminous intensity of the silicon luminous layer. Later, in order to overcome the problem that normal hydrogen passivation cannot fully saturate dangling bond defects, they developed a new type of high-pressure, low-temperature hydrogen passivation method that enables the optical gain of a silicon light emitting layer to reach the typical III-V laser material at one stroke. (such as GaAs, InP, etc.) on the basis of this; they designed and prepared the corresponding distributed feedback (DFB) resonant cavity, and ultimately successfully obtained optically pumped DFB-type silicon laser. The successful development of optically pumped silicon lasers also provides a reference for the development of electric pumped silicon lasers.
It has been found through experiments that as the high-pressure and low-temperature hydrogen passivation progresses, the optical gain of the silicon light emitting layer continues to increase, eventually reaching the levels of GaAs and InP. In the experiment, all the criteria for satisfying the laser generation conditions were also observed: threshold effect, sharp narrowing of spectral lines, polarization effect, and directional emission. The lasing peak is 770nm. Then they repeated the preparation of four lasers with the same structure. Since the effective refractive index of each light emitting layer is slightly different, the four peak wavelengths obtained are distributed in the range of 760-770 nm, and the full width at half maximum (FWHM) is reduced from about 120 nm before the lasing to 7 nm after the lasing. The project is supported by the National Natural Science Foundation of China (No.,,,) and Shanghai Yangfan Plan (16YF1400700).
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