Erbium-doped chalcogenide fiber ring laser for mid-IR applications

Absence of relaxation oscillation in SOA fiber ring lasers is analyzed in this paper, which is always presented in actively mode- locked erbium-doped fiber (EDF) ring lasers. The super-mode competition can be effectively suppressed in SOA ring lasers due to the gain saturation of SOA. The experimental demonstrations were confirmed the above issues and good stability in a SOA mode-locked fiber ring laser without any feedback circuits was shown.

A simple scheme for a switchable multi-wavelength erbium-doped fiber (EDF) ring laser is investigated by using a single stage of a Sagnac loop mirror. The multiple lasing outputs are obtained and switched readily by controlling the state of polarization (SOP). Since the transmission characteristics of the Sagnac loop mirror in terms of peak wavelengths and peak powers strongly depend on the SOP, the switching performance of the proposed multi-wavelength EDF laser can be effectively obtained. The proposed multi-wavelength EDF laser has versatile lasing outputs in states of a single-, dual-, triple-, and quadruple-wavelength oscillations. The multiple outputs are effectively switchable by adjusting the SOP.

In the paper, we study a single-longitudinal-mode (SLM) erbium-doped fiber (EDF) ring laser with a switchable single- and dual-wavelength output in C-band scale simultaneously. When a 1 × 4 wavelength-division-multiplexing (WDM) multiplexer is placed inside the ring cavity, four tunable single wavelengths and five sets of dual-wavelength with several mode-spacing can be accomplished, respectively. To achieve the selective and stable output characteristic, the suitable adjustment of cavity and birefringent losses are operated. Additionally, the laser characteristics of output wavelength, detected power, and optical signal to noise ratio (OSNR) have also been discussed.

We propose and experimentally demonstrate an all-pole-type cavity structure to force single longitudinal mode (SLM) operation in fiber lasers. The proposed structure is based on the modified version of the Smith predictor, which compensates delay in a closed-loop feedback system. This structure is applicable to arbitrary wavelengths and gain media, does not limit the tunability range of the laser, and does not require few centimeters long loops or Fabry-Pérot tunable filters to achieve SLM operation. Thus, the major drawbacks of the conventional SLM forcing mechanisms are alleviated. Therefore, this structure can be considered as a universal approach to SLM operation in fiber lasers. To exemplify this structure, an erbium-doped fiber ring laser in continuous-wave mode is implemented. The SLM operation is confirmed from the RF spectrum over a 10 GHz bandwidth, and the laser is tunable over 62 nm from 1512 to 1574 nm.

The performance of an erbium-doped fiber (EDF) ring laser based intra-cavity gas sensor is investigated theoretically and experimentally. A theoretical model for analyzing the effects of the EDF parameters and the system parameters on the performance of this gas sensor was established using coupled rate equations and propagation equations. We investigated a number of specific cases and suggested practical choices of their parameters. Experiments with two cavity losses were conducted to test the system sensitivity enhancement and the trend of the results matched well with the theoretical prediction. The results showed sensitivity enhancement factors ranged from 17-20 in the experimental system can be achieved.

A soliton mode-locked erbium-doped fiber (EDF) laser has been experimentally demonstrated using copper oxide (CuO) thin film as a saturable absorber (SA). The dispersion of the EDF cavity including the CuO-SA was balanced by a suitable length of single-mode fiber (SMF). The fabricated CuO-SA has 3.5% modulation depth and 3.3 MW/cm2 saturation intensity. The mode-locked train pulses have 1.7ps pulse width and 983kHz repetition rate, while the pulse energy and output power are 1.29nJ and 1.27mW, respectively, at maximum pump power of 159mW. These results indicate that the CuO thin film is a good SA candidate for a fiber laser operating at a low pump power. To the best of our knowledge, this is the first demonstration of a CuO-SA-based mode-locked fiber laser.

This work demonstrates a high-quality erbium-doped fiber (EDF) ring laser in the L-band gain range by combining the Rayleigh backscattering (RB) feedback signal and unpumped EDF induced saturable absorber (SA) filter. The optical filter effect induced by the RB feedback injection and EDF SA could generate single-longitudinal-mode (SLM) behavior and shrink the linewidth to sub-kHz. The output linewidth, power, and optical-signal-to-noise ratio (OSNR) of the fiber ring laser were also shown within the 42 nm wavelength bandwidth of 1565.0 to 1607.0 nm. Also, the instabilities of output power and central wavelength of each lasing lightwave were analyzed with a measurement time of 45 min.

Recent advances in power scaling of fiber lasers and amplifiers are hampered by the transverse mode instability, which deteriorates the output laser beam quality: the main cause is the overheating of the optical fibers. Radiative cooling has been suggested as a potentially viable heat removal scheme: the rare-earth-doped optical fiber is pumped at the pump wavelength, which is higher than the mean fluorescence wavelength of the active ions; therefore, the anti-Stokes fluorescence removes some and ideally most of the excess heat. In practice, the pump absorption cross section is considerably lower than its peak value, because the pump wavelength must be sufficiently longer than the mean fluorescence wavelength for efficient radiative cooling. Therefore, the design of such lasers and amplifiers must naturally depart from the conventional designs. I will focus on general scaling laws that govern the design of radiation-balanced fiber amplifiers and lasers. In particular, I will show that the undesirable parasitic absorption can make conventional designs unrealistic or at best irrelevant. In other words, a sufficiently large (and realistic) value of parasitic absorption can totally dominate the thermal balance, because its contribution scales linearly with the power, while the radiative cooling saturates at high power values. I will show that in conventional designs, radiation balancing can only be achieved at power values sufficiently low that may not even warrant any sophisticated cooling effort. However, there exist unconventional design strategies that make radiation balancing relevant even at high powers and I will explore such designs and their consequences.

High-power erbium-doped fiber laser with a carbon nanotubes-doped sol-gel glass mode-locker

Based on the fiber Bragg gratings (FBGs) and high nonlinear photonic crystal fiber (HN-PCF), a novel dual-wavelength erbium-doped fiber (EDF) laser is proposed and demonstrated. The experimental results show that, owing to the contributions of two degenerate four-wave mixings in the HN-PCF, the proposed fiber laser is great stable and two output signals are uniform at room temperature. With adjustment of the attenuator, our fiber laser can selectively realize one wavelength lasing.

In this investigation, we propose and investigate a stable and tunable dual-wavelength erbium-doped fiber (EDF) ring laser with self-injected Fabry-Perot laser diode (FP-LD) scheme. By using an FP-LD incorporated with a tunable bandpass filter (TBF) within the gain cavity, the fiber laser can lase at two single-longitudinal-mode (SLM) wavelengths simultaneously due to the self-injected operation. The proposed dual-wavelength laser has a good performance of the output power and optical side-mode suppression ratio (SMSR). The laser also shows a wide tuning range from 1523.08 to 1562.26 nm. Besides, the output stabilities of the fiber laser are also discussed.

In this paper, the usefulness of parabolic index profile with single clad as well as double clad fiber structure has been investigated for the design of erbium doped fiber amplifier (EDFA) and laser (EDFL). The characteristics of parabolic profile fiber lasers in terms of couple pump power and cavity length have been simulated for 980 nm pump and 1550 nm signal. At pump wavelength, the power confinement of double clad (94.55%) is higher than single clad (93.30%). At signal wavelength, the power confinement of double clad (83.80%) is much higher than single clad (67.88%). We found that, EDFL exhibits very high gain. Output power of 68.68 mw (18.36dBm) for single clad and 68.92 mw (18.38 dBm) for double clad is obtained at 140 mW pump power and 50 cm fiber length. It is observed that EDFA provides very high small signal gain in expense of low pump power and small fiber length. We obtained 40 dB small signal gain with 120 mW pump and 1m fiber length. Therefore, parabolic index profile may be useful to design EDFA and EDFL. In the case of EDFL, both geometry offer almost same performance but double clad shows very well result for EDFA.

The narrow linewidth fiber laser is useful in applications such as fiber sensing, optical communications, and spectroscopy. This paper presents an investigation of the model and an experiment of a stable, wavelength-selective, narrow linewidth, ring cavity erbium-doped fiber laser incorporating two fiber Bragg gratings (FBG) at 1530.18 nm and 1550.08 nm, respectively. An F-P tunable filter was used to select a specific wavelength after optimizing the spectral output from the two FBGs to measure their respective linewidths. The erbium-doped ring fiber laser was optimized by adjusting the optical cavity loss using a variable optical coupler at a coupling ratio of 95%. The variable coupler was set to an optimal coupling ratio of 95%, where the spectral output powers of 3.4 mW at 1530.18 nm and 3.1 mW at 1550.08 nm were achieved as the optimal fiber laser output powers. The balanced output power had an optical signal-to-noise ratio of (OSNR) of 61 dB for each wavelength. The linewidth was measured for both wavelengths without saturable absorbers, and 27.7 kHz and 28.3 kHz for 1530.18 nm and 1550.08 nm were obtained. Using the saturable absorber, the linewidths were narrowed to 25.3 KHz and 21.1 kHz for 1530.18 nm and 1550.08 nm, respectively.

Erbium-doped photonic crystal fiber laser with 49 mW

In the investigation, we propose and demonstrate a wavelength-selectable C- plus L-band erbium-doped fiber (EDF) ring laser with single-longitudinal-mode (SLM) output. Here, a C-band erbium-doped fiber amplifier (EDFA) is utilized to serve as gain medium together with proposed multi-cross-ring (MCR) scheme to extend the wavelength tunability to L-band range. Besides, the MCR can also suppress the multi-longitudinal-mode (MLM) significantly. Therefore, the measured output power and optical signal to noise ratio (OSNR) of each lasing wavelength are between -10.1 and -2.7 dBm, and 26.4 and 35.0 dB/0.06 nm, respectively in the wavelength range from 1530.0 to 1584.0 nm. In addition, the output stabilities of power and wavelength in the proposed EDF MCR laser have been also analyzed experimentally.