Soliton mode-locked laser in the infrared region using organic thin-film passive saturable absorber for optical communications

A physicist from Universitas Airlangga (Unair) has demonstrated the generation of soliton mode-locked pulses from an erbium-doped fiber laser (EDFL) cavity configured with 8-Hydroxyquinolino cadmium chloride hydrate (8-HQCdCl2H2O) based saturable absorber (SA). The soliton mode-locked laser is operational in the infrared region with the shortest pulse width of 950 fs and it could be applied in optical communications.

In principle, mode-locking is a laser pulsing technique that widely contributes to the field of optical communications due to its ability to produce picosecond and femtosecond pulses. There are two different schemes in the mode-locking technique: active and passive. On the one hand, the active scheme modulates the loss inside the laser cavity by a complex acoustic modulator. On the other hand, the passive scheme normally employs a thin-film SA fabricated by functional materials. Moreover, it has characteristics of simplicity in the design, flexible configuration, and compactness.

In this project, co-led by Prof. Dr. Moh. Yasin, M.Si. and his collaborator from the University of Malaya, Malaysia, organic thin-film based on 8-HQCdCl2H2O was developed, fabricated, and used as passive SA to produce soliton mode-locked pulses in three different EDFL cavities. Soliton pulse with the full-width half-maximum of 950 fs with repetition a repetition rate of 5.6 MHz indicates the presence of Kelly sidebands in the optical spectrum.

Figure 1. (a) Scanning electron microscope image, (b) energy-dispersive X-ray profile, and (c) Fourier-transform infrared spectrum of 8-HQCdCl2H2O.
Figure 2. Mode-locked performance based on different cavities lengths.
Figure 3. Optical spectra from the mode-locked EDFL configured with additional single-mode fiber of (a) 33m, (b) 53 m, and (c) 103 m.

For detailed information, please read:
M. M. Najm, H. Arof, B. Nizamani, A. S. Al-Hiti, P. Zhang, M. Yasin, and S. W. Harun, Journal of Modern Optics 68(5), 237-245, 2021 (

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