Abstract- Broadband terahertz anti-reflective structure fabricated by femtosecond laser drilling technique

• Yibin Zhang^a, 
• Minghui Yuan^a, 
• Lin Chen^a, , , 
• Bin Cai^a, 
• Rui Yang^b, 
• Yiming Zhu^a, , 

• ^a Shanghai Key Lab of Modern Optical System, Engineering Research Center of Optical Instrument and System, Ministry of Education, University of Shanghai for Science and Technology, No. 516 JunGong Road, Shanghai, China
• ^b BOCOM Smart Network Technologies, F18-20, Guangqi Mansion, No. 456, Hongcao Road, Shanghai, China

Received 7 July 2015, Revised 22 October 2015, Accepted 25 October 2015, Available online 17 November 2015

http://www.sciencedirect.com/science/article/pii/S0030401815302364

We fabricated several reverse conical holes on high-resistivity silicon substrate with different power and pulse number of femtosecond laser, and investigated their patterns and features by using scanning electron microscope (SEM). Then, we chose one of the experimental parameters prepared a reverse conical anti-reflection structure sample with period of 90 μm. Terahertz Time-domain Spectroscopy (THz-TDS) was used to test its properties. Compared with the nonstructural high-resistivity silicon, the transmission of structural high-resistivity silicon increases by the maximum of 14% in the range 0.32–1.30 THz. Furthermore, we simulated the sample by finite integral method (FIM). The simulated results show good consistency with experimental results. The transmission effect of the reverse conical holes were optimized via simulation. Results show that the related transmission effect can be improved by increasing the pulse numbers and decreasing the spot size of the femtosecond laser. The different transmission window can also be tuned by changing the reverse conical structure of different periods.