A passive Q-switched pulsed laser at 1.5 m region incorporating graphene nanoplatelets (GnPs) embedded in Polyvinyl Alcohol (PVA) is demonstrated. A surfactant is used to aid the dispersion of the GnPs before it is mixed with PVA to develop a GnPs-PVA film based SA. The SA is integrated into the laser cavity by attaching a cut of the GnPs-PVA film in between two fiber ferrule of the laser ring cavity.The proposed GnPs-PVA film based passive Q-switched laser was able to operate as the input pump power was increased from 39 mW up to a maximum of 148 mW before diminishing. The laser obtained operated with a central wavelength of 1530.76 nm. Repetition rates were obtained at 33 kHz to 91.5 kHz, throughout the tunable input pump power with the shortest pulse width of 2.42 s. Maximum attainable peak power and pulse energy of 1.2 mW and 5.9 nJ, respectively, was recorded, accompanied by a signal to noise ratio (SNR) of 28 dB.
Accurate value of absorption cross section is required for correct measurement of ozone concentration. Measurement of ozone has been done at different altitude and pressure. However, previous work has failed to establish significant relation between pressure and ozone absorption cross section. Therefore, this work aims to establish relation between pressure and maximum ozone absorption cross section via spectralcalc.com gas cell simulator. Simulation results show maximum absorption cross section 1.148×10-21 m2 molecule-1 and maximum absorption wavelength 255.442 nm are independent of pressure changes from 0.1 atm to 3.0 atm. Thus, measurement of ozone concentration at maximum absorption wavelength is strongly recommended due to negligible pressure dependence.
A tapered silica optical fiber (SOF) coated with graphene oxide is proposed and demonstrated as a humidity sensor. In order to reduce the diameter of the optical fiber from 125 μm to 26.9 μm as the sensing region, the flamebrushing technique was used to taper the fiber with the tapering length is about 30 mm. To increase the optical sensitivity, the tapered region was coated with graphene oxide, which will interact with the changes of humidity and affect the evanescent field in the tapered region. In this work, the proposed optical sensor works in the range of the humidity from 40% to 60%. The comparison was made between uncoated tapered fiber with the graphene oxide coated optical fiber and the experimental works reveal that the tapered fiber coated with graphene oxide gave better result compared to bare tapered optical fiber. It is showed that the tapered SOF with graphene oxide enables to increase the sensitiveness of the fiber to sense relative humidity.
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