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This report experimentally demonstrates optical pulse compression and pedestal suppression of mode-locked fiber laser. A simple Fabry-Perot in the reflection mode is utilized as Gires-Tournois interferometer (GTI) inside the seed of fiber-based mode-locked laser setup to compensate the group velocity dispersion (GVD) in all normal dispersion regime at 1030nm.

This report makes a comparison between the spectrum features of plasmonic metamaterial metal-insulator-conductor (MIC) sensor with a monolayer of graphene and another MIC sensor with a multilayer of graphite as the back reflector. In both structures, the silicon substrate as an insulator layer was sandwiched between subwavelength periodic nanogold cones as the first layer and graphene and graphite as the third layer, respectively. Nanolayer of chromium nanorods was also considered in the structure of MIC sensors as an interface layer between silicon and nanogold cone metasurface. The performance of the sensor was evaluated under different incident polarized light angles and different thickness of the metasurface when the metasurface infiltrated with seawater and air. The transmission spectrum of monolayer graphene-based MIC sensor, respecting to s-polarized waves, reveals prominent feature to detect the air rather than seawater in invisible regime. Meanwhile, the reflection spectrum of graphite-based MIC sensor provides ∼0 % reflection under resonance condition regarding s- and p-polarized waves for detecting air in visible spectrum.

Generation of dual-wavelength using passive semiconductor microring resonator with two sections of apodized grating with total length of 26 µm on the right and left sides is presented here. In this research we use the timedomain travelling wave (TDTW) method to model and simulate the microring resonator made of InGaAsP/InP waveguide. Microring resonator based optical mirrors and band-limited reflectors have been the subject of intense investigations in recent years. Therefore, we propose the microring resonator made of InGaAsP/InP waveguide having two sides grating section. The grating sections have a trapezoidal profile. The gratings provide the means to suppress repetition of the reflection spectrum at every free spectral range (FSR) removed from the design wavelength. The total grating length is 26 µm (each grating side has length of 13 µm), where the total circumference of the microring resonator is 526 µm. Propagation of the input Gaussian pulse (with 10 mW power and bandwidth of 0.76 ps) within the grating sections is presented, where it shows a good confinement of the propagation within the waveguide. As a result, multiple dual-wavelengths with tunable spacing within a range of 127 pm (15.8 GHz) and 237 pm (29.6 GHz) could be generated at the throughput port of the microring resonator. The dispersion of the grating section versus the total grating length and the frequency response of the throughput port output signals are presented. The generated dual-wavelength has many applications in optical sensing, radio frequency (RF) radiation, optical communication, optical switching, millimetre wave generators and biological research.

We demonstrate the design and operation of novel narrow spacing and stable dual-wavelength fiber laser (DWFL). A 70-cm ytterbium-doped fiber has been chosen as the gain medium in a ring cavity arrangement. Our design includes a short length photonic crystal fiber, acting as a dual-wavelength stabilizer based on its birefringence coefficient and nonlinear behavior and tunable band pass filter (TBPF) to achieve narrow spacing spectrum lasing. Our laser output is considered to be highly stable, with power fluctuation less than 0.8 dB over a period of 15 min. The flexibility and tunability of TBPF, together with polarization controller enable the spacing tuning of the DWFL from 0.03 nm up to 0.07 nm for 1040 nm region, and 0.10 nm up to 0.40 nm for 1060 nm region. The tunable wavelength spacing shows the flexibility of the DWFL in addition to stable and reliable properties of fiber laser in 1-m region.

We demonstrate a stable tunable dual-wavelength erbium-doped fiber laser generated by launching a mode-locked laser into an add–drop microring resonator. Two silicon-based high-index-contrast microring resonators with $Q$ -factors of 1.2 × 10 5 and 0.6 × 10 5 have been used as add–drop filters independently. As a result, multiwavelength generation was achieved and demonstrated both theoretically and experimentally with free spectral range (FSR) of 0.202 and 0.404 nm corresponding to the microrings' diameter of $\textrm{D}=2.54$ and $\textrm{D}=1.27\,\mbox{mm}$ . A high-resolution tunable bandpass filter and fiber Bragg gratings (FBGs) are then used to extract a tunable and switchable dual-wavelength coherent source from the generated multiwavelength coherent source. Subsequently, the dual-wavelength coherent source with tunable FSRs from 0.404 to 3.232 nm is achieved and presented. The obtained dual-wavelength output has a side-mode suppression ratio of more than 30 dB.

A system of soliton array (SA) for optical communication using the wired/wireless link is presented. Gaussian laser beam with relevant parameters is input into the rings system. Here, bright soliton with Full Width at Half Maximum (FWHM) and Free Specrum Range (FSR) of 120 ps and 370 ps are generated respectively. We demonstrate that SA can be obtained by a series of micro ring resonators with input optical laser pulse. A PIN photodetector with responsivity of 1 A/W and dark current of 10 nA is used to convert the optical pulses to array of radio frequency (RF). Here, transmission of SA via 70 km fiber optics and 25 m wireless has been investigated.

This paper describes a demonstration of a passively dual-wavelength Q-switched ytterbium-doped fiber laser using a selenium bismuth-based saturable absorber. By utilizing a short-length photonic crystal fiber in a ring cavity and performing adjustments to the polarization state of an incorporated polarization controller (PC), we obtained a stable dual-wavelength Q-switched output at 1037.14 and 1037.69 nm, with maximum pulse energy of 0.65 nJ, shortest pulse width of 8.46 μs, and pulse repetition rate from 15.37 to 59.24 kHz. The Q-switched laser output consistently achieved high-power stability with a 0.8 dB maximum fluctuation over a period of 20 min.

The add-drop ring resonator system is the fundamental building block of optical transmission and communication systems. An add-drop microring resonator (MRR) consisting of a $$120\,\upmu \hbox {m}$$ diameter loop of optical waveguide was used to filter the input spectrum of a mode-locked laser. The experimental setup is used to generate soliton mode-locked laser pulse, where we used the experimental data to model and simulate the propagation of the mode-locked soliton laser pulse within the MRR. The transmission characteristics of the through and drop ports output signals from this system are described in this paper. As results, multi-wavelength mode lock soliton with full width at half maximum and free spectral range (FSR) of 8 pm and 0.67 nm were generated respectively. The FSR of the input signals are enlarged significantly by the system, thus separating signal wavelengths by a resonator has been investigated. In the proposed scheme, FSR-spaced signals are leveraged as a means of obtaining higher bandwidth output signals while using an add-drop MRR.

This paper describes a demonstration of soliton transmission over fiber-wireless (Fi-Wi) networks using mode-locked stable solitons over a 50-km-long fiber and a short-distance wireless link. Ultrashort optical pulse sources in the 1.5- $\mu\hbox{m} $ region are seen as increasingly important for achieving ultrahigh-speed optical transmission and signal processing at optical nodes. Mode-locked solitons were generated by a simple ring laser cavity incorporating a very thin layer of carbon nanotube (CNT), together with an erbium-doped fiber (EDF) laser used as an active bulk gain medium. Experimental measurements involved the transmission of the generated mode-locked soliton over a 50-km-long single-mode fiber (SMF), and a radio-frequency (RF) spectrum subsequently generated was a result of beating frequency of wavelengths launched into the photodetector at the other end of the SMF. This RF spectrum array was in the range of WiFi frequencies. System performance was evaluated by first selecting one of the RF carriers centered at 2.5 GHz via an RF bandpass filter and subsequently using this carrier to transmit quadrature phase-shift keying (QPSK) and 16-quadrature amplitude modulation (16-QAM) data signals. The described optical circuit, containing an EDF laser, a CNT, an SMF, and a wireless link, was shown to achieve ultrastable transmission of mode-locked soliton over a long-distance Fi-Wi network.

This report experimentally demonstrates self-starting ultra-low repetition rate 4.5 kHz) mode-locked fiber laser in 1550 nm region. The combination of nonlinear polarization rotation (NPR) and nonlinear amplifying loop mirror (NALM) in the figure of eight configuration setup leads to achieve a stable self-starting mode-locked laser.

This paper describes the demonstration of a simple ytterbium-doped fiber (YDF) laser that utilized a short length of photonic crystal fiber (PCF) in a ring cavity and adjustments to the polarization state of an incorporated polarization controller (PC) to achieve a stable dual-wavelength output. The dual-wavelength lasing operation exploited the Mach-Zehnder interferometer effect, and the laser output consistently achieved high power stability with a 0.8 dB fluctuation over a period of 30 min. This proposed setup has the capability for adjustable spacing of two lasing wavelengths from a minimum of 0.40 nm to a maximum of 3.40 nm, allowing for flexibility in dual-wavelength laser generation in addition to stable and reliable system features. © 2016 Astro Ltd.

The novel technique for generating the robust, ultra-wideband (UWB) signal in the optical domain using a mode-locked laser incorporated with an add-drop microring resonator filter is presented. In order to enable the down conversion of the UWB signal to the RF domain, two wavelength ranges 1553.72 and 1553.92 nm, which are 24.65 GHz apart from each other, are used. These wavelengths were generated based on a single longitudinal mode (SLM) dual-wavelength fiber laser in a laser ring cavity. The upper wavelength of the generated dual-wavelength laser is modulated with the UWB spectrum using an optical carrier suppression (OCS) scheme and the lower wavelength is kept unmodulated. After beating the modulated and unmodulated wavelength by launching into the photodiode, the 24 GHz UWB signal can be generated to be applied to UWB over fiber (UWBoF) technology. The error vector magnitude (EVM) for the signal transmission was calculated and the EVM below 10% is achieved for 25 Km optical and 20 m wireless links.

In this work, we demonstrate a simple Q-switched pulsed ring ytterbium-doped fiber laser based on a few-layer TI:Bi2Se3 saturable absorber (SA). Few-layer bismuth selenide within a suspension was induced onto a fiber ferrule at room temperature via an optical deposition method, resulting in a simple SA for the laser. Stable Q-switched pulsed lasing was achieved at a low pump threshold of 122.2 mW at 974 nm. The pulse repetition rate ranged from 18.97 to 45.41 kHz, and the narrowest pulse width and the maximum pulse energy were 13.1 μs and 5.88 nJ respectively. Results indicated that TI:Bi2Se3 was also compatible with the 1 μm waveband, and hence could be considered a potential broadband SA for passively mode-locked and Q-switched optical fiber lasers.

The dual-wavelength fiber laser provides a compact, robust and stable platform for the generation of microwave signals. Two approaches towards generating microwave emissions using dual wavelengths are explored in this work, with both exploiting the heterodyning beat technique. Both approaches are based on a ring fiber laser with an erbium-doped fiber, having absorption coefficients of 16.0?20.0?dBm at 1531?nm and 11.0?13.0?dBm at 980?nm, serving as the active gain medium. A 10?cm long photonic crystal fiber with a solid core diameter of 4.37??m and surrounded by air holes of 5.06??m diameter with a separation of 5.52??m between them serves to create the desired dual-wavelength output. A tunable band pass filter with bandwidth of 0.8?nm serves as a tuning mechanism together with a polarization controller. Channel spacings as narrow as 0.00043?nm can be realized, giving a microwave output of about 671.9?MHz. Furthermore, the channel spacing can be extended to as large as 0.03631?nm, giving a microwave emission in excess of 4.59?GHz. The output is highly stable, with little change in power or wavelength observed over a test period of 22?min.

An ultra-stable dual-wavelength saturable absorber based on a cladding-embedded commercial graphene oxide (GO) solution by capillary action in a solid core photonic crystal fiber (PCF) is demonstrated for the first time. The saturation absorption property is achieved through evanescent coupling between the guided light and the cladding-filled graphene layers. Stable spacing dual-wavelength fiber lasing is attained by controlling the polarization state of a simple 0.9 m long ring of highly doped Leikki Er80-8/125 erbium-doped fiber as the primary gain medium with PCF, polarization controller and tunable bandpass filter. Embedded GO is used to generate the desired pulsed output, and the laser is capable of generating pulses having a repetition rate of 24 kHz with an average output power and pulse energy of 0.167 mW and 8.98 nJ, respectively, at the maximum pump power of 220 mW.

A Q-switched dual-wavelength fiber laser with narrow channel spacing is proposed and demonstrated. The fiber laser is built around a 3 m long erbium doped fiber as the gain medium and a 10 cm long photonic crystal fiber (PCF) as the element used to generate the dual-wavelength output. The PCF has a solid core approximately 4.37 μm in diameter and is surrounded by microscopic air-holes with a diameter of about 5.06 μm each as well as a zero-dispersion wavelength of about 980 nm. A graphene oxide based saturable absorber is used to generate the desired pulsed output. At the maximum pump power of 72 mW the laser is capable of generating pulses with a repetition rate and pulse-width of 31.0 kHz and 7.0 μs, respectively, as well as an average output power and pulse energy of 0.086 mW and 2.8 nJ, respectively. The proposed fiber laser has substantial potential for use in applications that require longer duration pulsed outputs such as in range finding and terahertz radiation generation.

By controlling the polarization state of a simple ring erbium-doped fiber laser with photonics crystal fiber, polarization controller (PC) and tunable band-pass filter, this paper demonstrates stable operation of narrow spacing dual-wavelength fiber laser (DWFL). The flexibility of the tunable band-pass filter and PC allows the spacing tuning of the DWFL from 80 pm up to 600 pm. Such tuning ability offers flexibility in the application of DWFL, particularly in tunable microwave generation and radio over fiber. Throughout the experiment, the DWFL shows high power stability within 0.6 dB and wavelength shift of less than 10 pm. In addition to that, it also produces a narrow linewidth optical output of 3 pm with a high signal to noise ratio of more than 60 dB.