Q-switched tunable fiber laser with aluminum oxide saturable absorber and Sagnac loop mirror
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ORIGINAL PAPER
Q-switched tunable fiber laser with aluminum oxide saturable absorber and Sagnac loop mirror S F S M Noor1, N F Zulkipli2, T F T M N Izam2, H Ahmad3, M Yasin4* and S W Harun2* 1
Photonics Engineering Laboratory, Department of Electrical Engineering, University of Malaya, 50603 Kuala Lumpur, Malaysia 2
Department of Electrical Engineering, University of Malaya, Lembah Pantai, 50603 Kuala Lumpur, Malaysia 3
Department of Physics, Faculty of Science, University of Malaya, 50603 Kuala Lumpur, Malaysia 4
Department of Physics, Faculty of Science, Airlangga University, Surabaya, Indonesia Received: 14 May 2019 / Accepted: 14 May 2020
Abstract: A Q-switched erbium-doped fiber laser with tunable output wavelength was demonstrated by utilizing aluminum oxide saturable absorber in conjunction with Sagnac loop mirror (SLM) filter. As the SLM temperature was increased from 30 to 70 °C, the laser operation can be tuned from 1568 to 1556 nm. At 1568 nm operation, the laser pulse frequency can be raised from 13.66 to 26.25 kHz by increasing the pump power from the threshold of 53 to 87 mW. With the increase in temperature, it is found that the pump threshold for the Q-switching increased, while the laser operation shifted to a shorter wavelength. Keywords: Q-switching operation; Fiber lasers; Temperature tuning; Sagnac loop mirror
1. Introduction Q-switched fiber lasers operating at 1.5 lm have attracted huge interest in recent years due to their ability to produce high pulse energy through the modulation of optical losses in the laser cavity. In contrast to mode-locked fiber lasers, the Q-switched fiber lasers are typically able to generate much higher energy. This type of laser is also more favorable from the efficiency, cost, and ease of construction perspectives. Furthermore, dispersion and nonlinearity characteristics need to be balanced in the mode-locked fiber lasers. This can only be achieved by the optimization and careful design of the cavity parameters. The Q-switched lasers have many potential applications in various fields, especially in areas where high pulse duration is important or ultrashort pulses are not required, such as environmental sensing, LIDAR, medical fields, and material processing [1–4]. They can be realized by using various approaches including the passive techniques based on saturable absorbers (SAs). These SAs can be developed for
*Corresponding author, E-mail: [email protected]; [email protected]
laser generation by using several types of materials and construction techniques. Semiconductor SA mirrors (SESAMs) were widely used for Q-switching pulses generation [5]. However, SESAMs have a limited operational bandwidth and complicated fabrication process. Throughout the past decades, many types of nanomaterials such as carbon nanotubes (CNTs) [6], graphene [7], transition metal dichalcogenide (TMD) [8, 9], topological insulators (TIs) [10], and recently transition metal oxides (TMOs) have been fabricated and investigated as the alternative SAs. TMO nanomaterials such as Zn
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