A novel inorganic material of Magnesium Nitrate (Mg(NO3)2) thin film is successfully investigated in the C-band region. The Q-switcher is Mg(NO3)2 thin film. The solvent casting method has been applied to prepare Mg(NO3)2 thin film before being positioned within the fiber ferrule duo to act as a Q-switcher. Thereby, the modulation depth and the saturation intensity of the Mg(NO3)2 thin film exhibit at 32.40% and 0.07 MW/cm2, respectively. It is possible to produce a steady Q-switched pulse fiber laser with a maximum pump power of 403.00 mW, a repetition rate of 72.56 kHz, and a pulse width of 3.00 µs. In addition, the tunable Q-switched pulse fiber laser is also examined using a figure-of-eight cavity design incorporating a tunable bandpass filter (TBF). Consequently, the operating wavelength is changed in the range of 1528 nm to 1552 nm, even while the pump power remains the same at 403.00 mW. During this time, the pulse width and repetition rate shifted from 2.10 µs to 4.10 µs and altered from 67.90 kHz to 35.80 kHz, respectively. Consequently, the Mg(NO3)2 thin film has the opportunity to be an effective saturable absorber for generating pulsed fiber lasers and can be applied in optical communications applications.

• Ahmad, H., Albaqawi, H.S., Yusoff, N., Bayang, L., Kadir, M. Z. B. A., & Yi, C.W. (2020). Tunable passively Q-switched erbium-doped fiber laser based on Ti3C2Tx MXene as saturable absorber. Optical Fiber Technology, 58, Article 102287. https://doi.org/10.1016/jyofte.2020.102287

• Ahmad, H., Ismail, N. N., Aidit, S. N., Yusoff, N., & Zulkifli, M. Z. (2020). Tunable S+/S band Q-switched thulium-doped fluoride fiber laser using tungsten ditelluride (WTe2). Results in Physics, 17, Article 103124. https://doi.org/10.1016/j.rinp.2020.103124

• Ahmad, H., Reduan, S. A., Ruslan, N. E., Lee, C. S. J., Zulkifli, M. Z., & Thambiratnam, K. (2019). Tunable Q-switched erbium-doped fiber laser in the C-band region using nanoparticles (TiO2). Optics Communications, 435, 283-288. https://doi.org/10.1016/j.optcom.2018.11.035

• Ahmad, H., Soltanian, M.R.K., Narimani, L., Amiri, I.S., Khodaei, A., & Harun, S.W. (2015). Tunable S-band Q-switched fiber laser using Bi2Se3 as the saturable absorber. IEEE Photonics Journal, 7(3), 1-8. https://doi. org/ 10.1109/JPHOT.2015.2433020

• Chang, T. G., & Irish, D. E. (1973). Raman and infrared spectra study of magnesium nitrate-water systems. The Journal of Physical Chemistry, 77(1), 52-57. https://doi.org/10.1021/j100620a011

• Chen, Y., Zhao, C., Chen, S., Du, J., Tang, P., Jiang, G., Zhang, H., Wen, S., & Tang, D. (2013). Large energy, wavelength widely tunable, topological insulator Q-switched erbium-doped fiber laser. IEEE Journal of Selected Topics in Quantum Electronics, 20(5), 315-322. https://doi. org/10.1109/JSTQE.2013.2295196

• Cuadrado-Laborde, C., Delgado-Pinar, M., Torres-Peiró, S., Díez, A. & Andrés, M.V. (2007). Q-switched all-fibre laser using a fibre-optic resonant acousto-optic modulator. Optics Communications, 274(2), 407-411. https://doi.org/10.1016/j.optcom.2007.02.032

• Degnan, J. J. (1995). Optimization of passively Q-switched lasers. IEEE Journal of Quantum Electronics, 31(11), 1890-1901. https://doi.org/10.1109/3.469267

• Delgado-Pinar, M., Zalvidea, D., Diez, A., Pérez-Millán, P., & Andrés, M. V. (2006). Q-switching of an all-fiber laser by acousto-optic modulation of a fiber Bragg grating. Optics Express, 14(3), 1106-1112. https://doi.org/10.1364/OE.14.001106

• El-Sherif, A. F., & King, T. A. (2003). High-energy, high-brightness Q-switched Tm3+-doped fiber laser using an electro-optic modulator. Optics Communications, 218(4-6), 337-344. https://doi.org/10.1016/s0030-4018(03)01200-8

• Faragl, M. A., El-Okr, M., Mahani, R. M., Turky, G. M., & Afify, H. H. (2014). Investigation of dielectric and optical properties of MgO thin films. International Journal of Advancement in Engineering, Technology and Computer Sciences, 1(1), 1-9.

• Feng, T., Mao, D., Cui, X., Li, M., Song, K., Jiang, B., Lu, H., & Quan, W. (2016). A filmy black-phosphorus polyimide saturable absorber for Q-switched operation in an erbium-doped fiber laser. Materials, 9(11), Article 917. https://doi.org/10.3390/ma9110917

• Feng, X., Tam, H. Y., & Wai, P. K. A. (2006). Stable and uniform multiwavelength erbium-doped fiber laser using nonlinear polarization rotation. Optics Express, 14(18), 8205-8210. https://doi.org/10.1364/OE.14.008205

• Han, Y., Guo, Y., Gao, B., Ma, C., Zhang, R., & Zhang, H. (2020). Generation, optimization, and application of ultrashort femtosecond pulse in mode-locked fiber lasers. Progress in Quantum Electronics, 71, Article 100264. https://doi.org/10.1016/j.pquantelec.2020.100264

• Island, J. O., Steele, G. A., van der Zant, H. S., & Castellanos-Gomez, A. (2015). Environmental instability of few-layer black phosphorus. 2D Materials, 2(1), Article 011002. https://doi.org/10.1088/2053-1583/2/1/011002

• Keller, U., Weingarten, K. J., Kartner, F. X., Kopf, D., Braun, B., Jung, I. D., Fluck, R., Honninger, C., Matuschek, N., & Der Au, J. A. (1996). Semiconductor saturable absorber mirrors (SESAM’s) for femtosecond to nanosecond pulse generation in solid-state lasers. IEEE Journal of selected topics in Quantum Electronics, 2(3), 435-453. https://doi.org/10.1109/2944.571743

• Khaleel, W. A., Sadeq, S. A., Alani, I. A. M., & Ahmed, M. H. M. (2019). Magnesium oxide (MgO) thin film as saturable absorber for passively mode locked erbium-doped fiber laser. Optics & Laser Technology, 115, 331-336. https://doi.org/10.1016/j.optlastec.2019.02.042

• Kim, N., Lee, P., Kim, Y., Kim, J. S., Kim, Y., Noh, D. Y., Yu, S. U., Chung, J., & Kim, K. S. (2014). Persistent topological surface state at the interface of Bi2Se3 film grown on patterned graphene. ACS Nano, 8(2), 1154-1160. https://doi.org/10.1021/nn405503k

• Mao, D., She, X., Du, B., Yang, D., Zhang, W., Song, K., Cui, X., Jiang, B., Peng, T., & Zhao, J. (2016). Erbium-doped fiber laser passively mode locked with few-layer WSe2/MoSe2 nanosheets. Scientific Reports, 6(1), Article 23583. https://doi.org/10.1038/srep23583

• Mia, M. N. H., Pervez, M. F., Hossain, M. K., Rahman, M. R., Uddin, M. J., Al Mashud, M. A., Ghosh, H. K., & Hoq, M. (2017). Influence of Mg content on tailoring optical bandgap of Mg-doped ZnO thin film prepared by sol-gel method. Results in physics, 7, 2683-2691. https://doi.org/10.1016/j.rinp.2017.07.047

• Morshed, M., Hattori, H. T., Haque, A., & Olbricht, B. C. (2017). Magnesium diboride (MgB2) as a saturable absorber for a ytterbium-doped Q-switched fiber laser. Applied Optics, 56(27), 7611-7617. https://doi.org/10.1364/AO.56.007611

• Okhotnikov, O., Grudinin, A., & Pessa, M. (2004). Ultra-fast fibre laser systems based on SESAM technology: New horizons and applications. New Journal of Physics, 6(1), Article 177. https://doi.org/10.1088/1367-2630/6/1/177

• Oztas, M., Bedýr, M., Sur, S., & Öztürk, Z. (2012). Influence of an aqueous/ethanolic solution on the structural and electrical properties of polycrystalline ZnS films. Chalcogenide Letters, 9(6), 249-256.

• Płóciennik, P., Guichaoua, D., Zawadzka, A., Korcala, A., Strzelecki, J., Trzaska, P., & Sahraoui, B. (2016). Optical properties of MgO thin films grown by laser ablation technique. Optical and Quantum Electronics, 48, 1-12. https://doi.org/10.1007/s11082-016-0536-8

• Salam, S., Nizamani, B., Yasin, M., & Harun, S. W. (2021). C-band tunable Q-switched fiber laser based on Alq3 as a saturable absorber. Results in Optics, 2, Article 100036. https://doi.org/10.1016/j.rio.2020.100036

• Sulaiman, M., Rahman, A. A., & Mohamed, N. S. (2013). Structural, thermal and conductivity studies of magnesium nitrate–alumina composite solid electrolytes prepared via sol-gel method. International Journal of Electrochemical Science, 8, 6647-6655.

• Sun, Z., Hasan, T., & Ferrari, A. C. (2012). Ultrafast lasers mode-locked by nanotubes and graphene. Physica E: Low-dimensional Systems and Nanostructures, 44(6), 1082-1091. https://doi.org/10.1016/j.physe.2012.01.012

• Sun, Z., Martinez, A., & Wang, F. (2016). Optical modulators with 2D layered materials. Nature Photonics, 10(4), 227-238. https://doi.org/10.1038/nphoton.2016.15

• Xia, F., Wang, H., & Jia, Y. (2014). Rediscovering black phosphorus as an anisotropic layered material for optoelectronics and electronics. Nature Communications, 5(1), Article 4458. https://doi.org/10.1038/ncomms5458

• Yuzaile, Y. R., Awang, N. A., Zalkepali, N. U. H. H., Zakaria, Z., Latif, A. A., Azmi, A. N., & Hadi, F. A. (2019). Pulse compression in Q-switched fiber laser by using platinum as saturable absorber. Optik, 179, 977-985. https://doi.org/10.1016/j.ijleo.2018.11.057

• Zalkepali, N. U. H. H., Awang, N. A., Yuzaile, Y. R., Zakaria, Z., Latif, A. A., Ali, A. H., & Mahmud, N. N. H. E. N. (2019). Indium tin oxide thin film based saturable absorber for Q-switching in C-band region. Journal of Physics: Conference Series IOP Publishing, 1371(1), Article 012018. https://doi.org/ 10.1088/1742-6596/1371/1/012018

• Zalkepali, N. U. H. H., Awang, N. A., Yuzaile, Y. R., Zakaria, Z., Latif, A. A., Ali, A. H., & Mahmud, N. N. H. E. (2021). Tunable indium tin oxide thin film as saturable absorber for generation of passively Q-switched pulse erbium-doped fiber laser. Indian Journal of Physics, 95, 733-739. https://doi.org/10.1007/s12648-020-01738-y

• Zhao, S., Zhao, J., Li, G., Yang, K., Sun, Y., Li, D., An, J., Wang, J. & Li, M. (2006). Doubly Q‐switched laser with electric‐optic modulator and GaAs saturable absorber. Laser Physics Letters, 3(10), 471-473. https://doi.org/ 10.1002/lapl.200610038