Abstract-All-fiber passively Q-switched fiber lasers have been demonstrated by using a graphene oxide (GO) Q-switcher for possible applications in telecommunication, laser processing, fiber sensing and medicine. The GO material was obtained through a modified Hummers method from expanded acid washed graphite flakes and was embedded into a polyvinyl alcohol (PVA) film to form a saturable absorber (SA) device. The Q-switched pulse operates at 1563.3nm with a repetition rate that can be tuned from 44.33kHz to 61.77kHz as the pump power changes from 39mW to 96mW. The highest repetition rate of 61.77kHz is achieved at a pump power of 96mW and it is observed that the Qswitched pulse produced a maximum pulse energy of 0.054nJ and pulse width of 5.57µs at 96mW pump power.Q-switched fiber lasers are gaining great interest for various applications such as medicine, remote sensing, marking and machining. They can be realized using either active or passive techniques [1,2]. Compared with the active method, the passive Q-switching owns the unique advantage of a simple structure in all-fiber designing. The passive Q-switched laser can be realized by adopting a saturable absorber (SA) in the cavity. So far, many kinds of SAs have been reported, such as semiconductor saturable absorber mirrors (SESAMs) [2], carbon nanotubes (CNTs) [3,4] and graphene [5]. SESAM has a narrow wavelength tuning range, and its modulation depth is typically low [2]. The CNTs and graphene are preferable SAs specifically for Q-switching operations because of their advantages including low saturation intensity, low cost and broadband wavelength operation [5].Graphene is a preferable SA to replace the SESAMs. However, the preparation of a high quality graphene film is more difficult and expensive. Furthermore, graphene cannot be dissolved in water so that the efficiency for film fabrication by a graphene aqueous solution is decreased. Graphene oxide (GO) has traditionally served as a precursor for graphene because of its simple fabrication method and low cost [6,7]. In this paper, we demonstrate * E-mail: anasabdullatiff@utem.edu.my a Q-switched Erbium-doped fiber laser (EDFL) using a new GO material as SA. The SA device is fabricated by embedding a GO material into a polyvinyl alcohol (PVA) film. The GO material was obtained from expanded acid washed graphite flakes via a modified Hummers method. The proposed SA can be operated in a broad wavelength range because of its unselective absorption.The GO was synthesized through a modified Hummers method from expanded acid washed graphite flakes, which involves many steps. First, a small amount of graphite powder (5g) was poured into 125ml of H 2 SO 4 . Next, 2.75g NaNO 3 reagents was added into the beaker to start the reaction. The mixture was kept into an ice water bath in order to keep it below 5°C. A small amount of KMnO 4 oxidant (15g) was added in portions into the mixture under continuous stirring. After the addition of the KMnO 4 , the beaker was heated and kept at a temperature of around 30°C by cont...
Ambulance is one the most critical component in healthcare where it must have highest reliability and mobility to ensure minimum travel time of patient to the hospital. In Malaysia, there are significant number of cases where ambulance tend to have breakdown or caught on fire due to electrical current overload which caused by unmanaged electrical usage by medical equipment. To overcome this problem, a smart power management system has been developed by employing Hall-Effect based current sensor replacing conventional fuse. The sensor reading is actively analysed by a microcontroller which will cut off electrical power from over-current equipment. The system also can prioritize some critical equipment to be powered when there are limited current available.
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