Yu Chen, Tiu Zian Cheak, Lip Zhan Hong, Tan Sin Jin, Cheng Xiau San, Masruroh, Sulaiman Wadi Harun
A harmonic mode-locked pulse train is generated in a thulium-doped fiber laser (TDFL) operating in the 2-µm wavelength region using polyacrylonitrile (PAN) as a saturable absorber (SA). The PAN SA was fabricated as a thin film by embedding the material in a PVA host matrix and inserting it into a ring laser cavity. With the incorporation of the PAN film, the TDFL achieves stable high-frequency pulsed operation at approximately 163 MHz. As the pump power is increased from 380 mW to 534 mW, harmonic mode-locking is maintained with a constant repetition rate and pulse width, accompanied by a signal-to-noise ratio of 50.1 dB and supermode suppression level of 36.7 dB, indicating good operational stability. The maximum average output power reaches 7.0 mW at the highest pump level. These results confirm that the PAN thin film functions effectively as a SA and represents a promising candidate for ultrafast pulse generation in the mid-infrared spectral region. © 2026 Elsevier Inc.
Chongqing Vocational Institute of Engineering, No.1, North and South Avenue, Binjiang New City, Jiangjin District, Chongqing, 402260, China; School of Engineering & Computing, MILA University, No 1, Persiaran MIU, Putra Nilai, Negeri Sembilan, Nilai, 71800, Malaysia; Faculty of Engineering, UOW Malaysia KDU University College, Selangor, Shah Alam, 40150, Malaysia; Department of Physics, Faculty of Mathematics and Natural Sciences, Universitas Brawijaya, Malang, 65145, Indonesia; Photonics Engineering Laboratory, Department of Electrical Engineering, University of Malaya, Kuala Lumpur, 50603, Malaysia
