Stable multiwavelength semiconductor optical amplifier-based fiber laser using a 2-mode interferometer

A multiwavelength semiconductor optical amplifier (SOA) fiber laser based on all-fiber two-mode interferometer (TMI) structure is demonstrated. The TMI generates in a comb-like spectrum with a 1-nm wavelength spacing and extinction ratio of 5.7 dB. By incorporating a TMI in the laser cavity, stable multiwavelength operation is obtained with 30 output channels from 1570.8 to 1600.8 nm with peak powers of at least 10 dB from the highest peak. The output comb spectrum and the overall stability of the multiwavelength are also enhanced with by inducing the four-wave-mixing effect in the cavity. The multiwavelength SOA fiber laser shows high operational stability with peak power fluctuations exceeding 1 dB observed only at the 1st, 23rd, 26th, and 30th peaks, which are at the ends of the multiwavelength spectrum

Graphene-PVA saturable absorber for generation of a wavelength-tunable passively Q-switched thulium-doped fiber laser in 2.0 μm

Graphene, a 2D material, has been used for generation of pulse lasers due to the presence of its various fascinating optical properties compared to other materials. Hence in this paper, we report the first demonstration of a thulium doped fiber laser with a wavelength-tunable, passive Q-switched output using a graphene-polyvinyl-alcohol composite film for operation in the 2.0 µm region. The proposed laser has a wavelength-tunable output spanning from 1932.0 nm to 1946.0 nm, giving a total tuning range of 14.0 nm. The generated pulse has a maximum repetition rate and average output power of 36.29 kHz and 0.394 mW at the maximum pump power of 130.87 mW, as well as a pulse width of 6.8 µs at this pump power. The generated pulses have a stable output, having a signal-to-noise ratio of 31.75 dB, and the laser output is stable when tested over a period of 60 min. The proposed laser would have multiple applications for operation near the 2.0 micron region, especially for bio-medical applications and range-finding

1.3 μm dissipative soliton resonance generation in Bismuth doped fiber laser

In this work, a Figure-9 (F9) bismuth-doped fiber laser (BiDFL) operating in the dissipative soliton resonance (DSR) regime is presented. The 1338 nm laser used a BiDF as the active gain medium, while a nonlinear amplifying loop mirror (NALM) in an F9 configuration was employed to obtain high energy mode-locked pulses. The wave breaking-free rectangular pulse widened significantly in the time domain with the increase of the pump power while maintaining an almost constant peak power of 0.6 W. At the maximum pump power, the mode-locked laser delivered a rectangular-shaped pulse with a duration of 48 ns, repetition rate of 362 kHz and a radio-frequency signal-to-noise ratio of more than 60 dB. The maximum output power was recorded at around 11 mW with a corresponding pulse energy of 30 nJ. This is, to the best of the author’s knowledge, the highest mode-locked pulse energy obtained at 1.3 μm as well as the demonstration of an NALM BiDFL in a F9 configuratio

Bismuth oxide nanoflakes for passive Q-switching in a C-band erbium doped fiber laser

In this work, bismuth oxide (Bi2O3) nanoflakes suspended in a polyvinyl alcohol (PVA) host are used as a saturable absorber (SA) in an erbium-doped fiber laser (EDFL). The facile hydrothermal method is employed to synthesize the Bi2O3 nanoflakes as the SA, which provides stable Q-switching at a central wavelength of 1564 nm with a maximum pulse energy of 21.31 nJ. The generated pulses have repetition rates of 28.41–49.51 kHz and pulse widths of 4.9–1.55 µs over the available pump power range. The Bi2O3-PVA based SA also has a high signal-to-noise ratio (SNR) of 51.28 dB, indicating a significantly stable output and demonstrating the high potential of the fabricated Bi2O3-PVA film for practical applications. To the best of the author's knowledge, this is the first report of the use of a Bi2O3-PVA based SA for Q-switching in a C-band EDFL region

85 nm wide-band tunable erbium doped fiber laser using a gallium selenide (GaSe)-based saturable absorber for passive optical modulation

A wide-band and tunable passively optically modulated fiber laser using a gallium selenide (GaSe) based saturable absorber (SA) is proposed and demonstrated. The GaSe-based SA is prepared by mechanical exfoliation and is able to generate self-starting pulses that have a maximum repetition rate of 57.9 kHz and minimum pulse width of 3.6 s. The highest pulse energy generated by the pulse laser is 30 nJ. The laser has wide-band tunability covering a broad wavelength range of 1501 nm to 1586 nm, giving a total tuning range of over 85 nm. The proposed laser would have potential for use in various optical telecommunications and measurement applications. © 2019 Astro Ltd

Optically Modulated Tunable O-Band Praseodymium-Doped Fluoride Fiber Laser Utilizing Multi-Walled Carbon Nanotube Saturable Absorber*

A tunable and optically modulated fiber laser utilizing a multi-walled carbon nanotube based saturable absorber is demonstrated for operation in the O-band region. A praseodymium-doped fluoride fiber is used as the gain medium and the system is capable of generating modulated outputs at 1300 nm. Pulsed output is observed at pump powers of 511 mW and above, with repetition rates and pulse widths that can be tuned from 41 kHz and 3.4 μs to 48 kHz and 2.4 μs, respectively, at the maximum pump power available. A maximum average output power of 100 μW with a corresponding single pulse energy of 2.1 nJ is measured, while the tunability of the proposed laser is from 1290 nm to 1308 nm. The output is stable, with peak power fluctuations of ∼4 dB from the average value. © 2019 Chinese Physical Society and IOP Publishing Ltd

Dissipative soliton resonance in a passively mode-locked praseodymium fiber laser

Dissipative soliton resonance (DSR) operation in a passively mode-locked praseodymium-doped fluoride fiber laser with a nonlinear optical loop mirror is proposed and demonstrated. A praseodymium-doped fluoride fiber is employed as the gain medium to allow lasing in the 1.3 μm region, and a stable square pulse emission at 1303 nm is observed. The width of the square pulse broadens with the increment of pump power, from 83 ns to 239 ns, whereas the peak power remains at a comparable level. The highest single pulse energy is recorded at around 2.3 nJ without the appearance of pulse breaking, validating the predicted DSR operation. To the best of author's knowledge, this work is the first study of DSR operation in the 1.3 μm region

Multi-wavelength Praseodymium fiber laser using stimulated Brillouin scattering

A multi-wavelength Brillouin Praseodymium fiber laser (MWBPFL) operating at 1300 nm region is demonstrated based on the hybrid scheme by utilizing Brillouin gain medium and Praseodymium-doped fluoride fiber as linear gain medium. A 15 µm air gap is incorporated into the cavity to allow the switching of Brillouin frequency spacing from double to single spacing. Under the Brillouin pump of 8 dBm and the 1020 nm pump power of 567.2 mW, 36 Stokes lines with a wavelength spacing of 0.16 nm and 24 Stokes lines with a wavelength spacing of 0.08 nm are achieved. The wavelength tunability of 8 nm is realized for both MWBPFLs by shifting the Brillouin pump wavelength. The MWBPFLs exhibit an excellent stability in the number of generated Stokes and power level over one-hour period

Mode-locked pulse generation in erbium-doped fiber laser by evanescent field interaction with reduced graphene oxide-titanium dioxide nanohybrid

In this work, a new nanohybrid saturable absorber (SA)is successfully fabricated from reduced graphene oxide (rGO)nanosheets and titanium dioxide (TiO2)nanoparticles. The nanohybrid material is synthesized using the simple and inexpensive hydrothermal technique. The SA is fabricated by depositing the nanohybrid solution onto a D-shaped fiber in an erbium-doped fiber (EDF)laser cavity. The evanescent wave interaction between the incident light and rGO-TiO2 nanohybrid material induces mode-locking in the EDF laser at the threshold pump power of 100.80 mW. A stable soliton pulse with a center wavelength of 1560.45 nm and 3-dB bandwidth of 2.47 nm is obtained. The generated pulses have a repetition rate and pulse width of 11.19 MHz and 1.05 ps at the highest pump power of 268.10 mW. The proposed rGO-TiO2 nanohybrid of this work is a promising SA material for generating mode-locking in an EDF laser for optical modulation applications. © 201

Supercontinuum Micrometer-Displacement Sensor Using Single-Multi-Air-Gap-Single Mode Fiber as Sensing Probe

In this paper, a displacement sensor utilizing a Mach-Zehnder interferometer with a single-multi-air-gap-single mode (SMAS) fiber structure is proposed and demonstrated. A 30-cm-long four-mode step index fiber (FMSIF) is used as the multimode fiber in the SMAS structure, with the left end of the FMSIF fusion spliced to a 50-cm-long single-mode fiber (SMF-28). The right end of the FMSIF is aligned to another 50-cm SMF-28 on the v-groove of Fitel S178A fusion splicer but without splicing, creating an air gap with a tunable length of 0-300μm. The performance of the displacement sensor is investigated over the range of 1.1-1.7μm using a supercontinuum source. Through the experiment wavelength range, the highest sensor sensitivity is achieved at 1.7 μm with a sensitivity of 12.3 pm/ μm and an R2 coefficient of 0.926. The implementation of a displacement sensor utilizing the simple and cost-effective concept of the SMAS will be beneficial for use in various areas, such as biomedicine, manufacturing, and engineering