Self-stabilized passive, harmonically mode-locked stretched-pulse erbium fiber ring laser

We have studied a passive, harmonically mode-locked stretched-pulse erbium fiber ring laser with net positive dispersion that is self-stabilized by gain depletion and electrostriction. Periodic pulses with supermode suppression of >75 dB and picosecond jitter are achieved. The pulses are compressible to 125 fs by external chirp compensation. The repetition rate is 220 MHz, and the average power is as high as 80 mW.     

Frequency comb linewidth of an actively mode-locked fiber laser

We report what is to our knowledge the first measurement of the linewidth of the frequency comb lines of a mode-locked Er-doped fiber laser. By propagating the output pulses through fiber as long as 1000 km in a modified self-heterodyne arrangement, we have measured the effective linewidth of the comb lines to be less than 12 kHz on a 5-ms time scale; the width is due primarily to frequency jitter from environmental fluctuations. Deconvolution of the spectral line shapes by use of Voigt analysis yields an upper limit of the intrinsic Lorentzian width of 3 kHz.     

Highly stable, passively mode-locked fiber laser with low pump power for subpicosecond pulse generation

We present the design of highly stable, passively mode-locked fiber lasers which are based on a simple configuration and require a low pump power for the generation of optical pulses with subpicosecond pulsewidth. Our designed fiber laser uses a semiconductor saturable absorber mirror to realize the self-starting, passive mode locking at a low pump power of 29 mW, with which a stable optical pulse train is obtained at the fundamental repetition rate of 52.5 MHz and the central wavelength of 1557 nm. The output mode-locked optical pulses have a pulsewidth of 881 fs and an average output power of 1.78 mW, respectively.     

Generation of a 660-2100 nm laser frequency comb based on an erbium fiber laser

We present a multibranch laser frequency comb based upon a 250 MHz mode-locked erbium-doped fiber laser that spans more than 300 THz of bandwidth, from 660 nm to 2100 nm. Light from a mode-locked Er:fiber laser is amplified and then broadened in highly-nonlinear fiber to produce substantial power at ～1050 nm. This light is subsequently amplified in Yb:fiber to produce 1.2 nJ, 73 fs pulses at 1040 nm. Extension of the frequency comb into the visible is achieved by supercontinuum generation from the 1040 nm light. Comb coherence is verified with cascaded f-2f interferometry and comparison to a frequency stabilized laser.     

169 MHz repetition frequency all-fiber passively mode-locked erbium doped fiber laser

Passively mode-locked stretched-pulse erbium fiber laser is presented. With all-fiber configuration 111 fs pulses were achieved with the fundamental repetition rate of 169 MHz and an average output power of more than 30 mW. Proposed setup shows excellent stability, reliability and ‘turn-key’ operation. The impact of the pump power on laser parameters is described.     

Investigation of passively mode-locked erbium doped fiber ring laser due to nonlinear polarization rotation

Passively mode-locked erbium doped fiber ring laser was investigated. We present optimization of laser configuration where nonlinear polarization rotation was used for modes synchronization. Simulations of pulse propagation inside a laser cavity were applied in order to confirm the optimisation technique. Experimental results are presented and more than 32-nm spectral width of the output frequency comb was obtained.     

All-fiber mode-locked fiber laser

An environmentally stable mode-locked fiber laser based on nonlinear polarization rotation is experimentally demonstrated. The laser is based on a novel laser configuration that has negligible low-power steady-state reflectivity from one side and, consequently, no CW gain. The laser is self starting and the configuration is implementable as an all-fiber laser with standard polarization-maintaining fiber-pigtailed components. A pulse duration of 5.6 ps is obtained at a repetition rate of 5.96 MHz and at an average power of 8 mW. As an application of the proposed laser configuration, 213 mW of supercontinuum (600-1750 nm) was demonstrated from a fiber laser system with no sections of free-space optics.     

Stable multigigahertz pulse-train formation in a short-cavity passively harmonic mode-locked erbium/ytterbium fiber laser

We demonstrate a short-cavity erbium-ytterbium fiber laser that is passively mode locked by a saturable Bragg reflector with a fundamental repetition rate of 235 MHz . The laser operates in the soliton regime and under passive harmonic mode locking with 11 pulses in the cavity and produces output pulse trains at 2.6 GHz with transform-limited 270-fs pulses and 1.6 mW of average power. Within the cavity the multiple pulses form a stable pattern with fixed, nearly equal pulse-to-pulse temporal spacings, causing the output pulse train to have timing offsets of less than 15 ps. A slow gain-recovery model is proposed to explain the pulse-train self-organization.     

20-GHz broadly tunable and stable mode-locked semiconductor amplifier fiber ring laser

We present an actively mode-locked fiber ring laser that uses a single active semiconductor optical amplifier device to provide both gain and gain modulation from an external optical pulse train. The laser source generated 4.3-ps pulses at 20 GHz over a 16-nm tuning range and is stable against environmental changes and simple to build.     

Stable mode-locked fiber laser using 49 cm long bismuth oxide based erbium doped fiber and slow saturable absorber

A stable mode-locked fiber laser employing a 49 cm long bismuth oxide based erbium doped fiber (Bi-EDF) by using a slow saturable absorber is demonstrated. Near transform limited short pulses with a repetition rate of 8.27 MHz are obtained at a wavelength of 1560 nm with a maximum spectral width of 15 nm. Results indicate that pulse characteristics are strongly dependent on pump power rather than spectral width. Moreover the Time-Bandwidth products (TBWP), pulse duration, the energy fluctuation and timing jitter decrease with increasing pump power. The pulse width is continuously varied from 1.2 ps to less than 300 fs. It produces stable mode locking with a maximum spectral width of 15 nm, minimum timing jitter of 4 ps and energy fluctuations of 2.5%. The pulse train was amplified using a two-stage amplifier up to 447 mW average power corresponding to peak powers of 177.3 kW.     

Mode-locked fiber laser frequency-controlled with an intracavity electro-optic modulator

We demonstrate a mode-locked, erbium-doped fiber laser with its repetition frequency synchronized to a second fiber laser via an intracavity electro-optic modulator (EOM). With servo control from the EOM (bandwidth approximately 230 kHz) and a slower speed intracavity piezoelectric transducer (resonance at approximately 20 kHz), we demonstrate stabilization of the repetition frequency with an in-loop rms timing jitter of 10 fs, integrated over a bandwidth from 1 Hz to 100 kHz. This represents what is to our knowledge the first time an EOM has been introduced inside a mode-locked laser cavity for fast servo action and the lowest timing jitter reported for a mode-locked fiber laser.     

High-sensitivity mode-locked fiber laser gyroscope

We report significant performance improvement of a mode-locked fiber laser gyroscope. A Fabry-Perot cavity GaAlAs laser diode whose front facet was antireflection coated was used as a gain medium. The rms noise equivalent rotation rate measured with a time-interval counter was improved to 0.06deg/ radicalh. The long-term drift of the gyroscope signal was reduced to 100deg/ radicalh after a polarizer was inserted into the laser cavity formed with a polarization-maintaining fiber.     

Colliding-pulse harmonically mode-locked fiber laser

A Fabry–Perot semiconductor saturable absorber has been implemented in a colliding pulse configuration for stabilizing a harmonically mode-locked fiber laser. An environmentally stable CPM design is shown to enhance supermode suppression. Received: 24 October 2000 / Revised version: 28 November 2000 / Published online: 9 February 2001     

Tunable, high-repetition-rate, harmonically mode-locked ytterbium fiber laser

We report a ytterbium fiber laser mode locked at its 281st harmonic, which corresponds to a repetition rate greater than 10 GHz. The laser produces linearly polarized, 2-ps pulses with up to 38-mW of average output power. The mode-locked pulses are tunable over a 58-nm window centered on 1053 nm.     

Actively mode-locked visible upconversion fiber laser

Active mode locking of a Pr(3+)/Yb (3+) -doped upconversion fluoride fiber laser with an all-fiber ZnO acousto-optic phase modulator is demonstrated for the first time to the authors' knowledge. Optical pulses of ~550-ps duration with a repetition rate of 239 MHz at a wavelength of 635 nm have been generated.     

Figure-eight actively-passively mode-locked erbium-doped fiber laser

The advantages of using nonlinear optical loop mirror (NOLM) to compress pulse with slight amplitude fluctuation and reflected energy loss are analyzed in theory. Experimentally the NOLM is placed in an actively mode-locked erbium-doped fiber ring laser to form a figure-eight actively and passively mode-locked fiber laser. 12 ps mode-locked pulses centered at 1.543 μm were obtained with the modulation frequency of 2.498748700 GHz. 3.715 mW output power is achieved with 50 mW pump power.     

Broad-spectrum frequency comb generation and carrier-envelope offset frequency measurement by second-harmonic generation of a mode-locked fiber laser

A frequency comb spanning more than one octave has been achieved by injecting the second-harmonic generation (780 nm) of a mode-locked fiber laser (1.56 microm) into a photonic crystal fiber. We propose and realize a novel interferometric scheme for observing the carrier-envelope offset frequency of the frequency comb. Frequency noise has been observed on the measured carrier-envelope offset frequency, which has been confirmed to be generated in the photonic crystal fiber by comparing the measured beat frequencies between cw lasers and frequency combs before and after the photonic crystal fiber. The mode-locked fiber laser is considered to be an important candidate for the light source used in realizing a compact optical frequency measurement system including applications in the telecommunication bands.     

Bandpass filters based on pi-shifted long-period fiber gratings for actively mode-locked erbium fiber lasers

We have fabricated bandpass filters based on pi-shifted long-period gratings for application in actively mode-locked erbium fiber lasers. Introducing the pi-phase shift in the middle of the grating opens a bandpass within the core-cladding mode resonance peaks. With a 22-nm bandwidth filter inserted in an actively mode-locked erbium fiber sigma laser, solitonlike pulses are generated, with a power-dependent duration of approximately 3-5 ps , at a 3-GHz repetition rate. These all-fiber filters have the advantages of low insertion loss (<0.5 dB) and a wide bandwidth (10-20 nm), and they do not require that a circulator be inserted into the laser cavity.     

Observation of stable bound soliton with dual-wavelength in a passively mode-locked Er-doped fiber laser

A phase-locked bound state soliton with dual-wavelength is observed experimentally in a passively mode-locked Erdoped fiber(EDF) laser with a fiber loop mirror(FLM). The pulse duration of the soliton is 15 ps and the peak-to-peak separation is 125 ps. The repetition rate of the pulse sequence is 3.47 MHz. The output power is 11.8 mW at the pump power of 128 mW, corresponding to the pulse energy of 1.52 nJ. The FLM with a polarization controller can produce a comb spectrum, which acts as a filter. By adjusting the polarization controller or varying the pump power, the central wavelength of the comb spectrum can be tuned. When it combines with the reflective spectrum of the fiber Bragg grating, the total spectrum of the cavity can be cleaved into two parts, then the bound state soliton with dual-wavelength at 1549.7 nm and 1550.4 nm is obtained.     

Multimode interference filter for tuning of a mode-locked all-fiber erbium laser

We present a mode-locked all-fiber erbium laser that can be tuned in wavelength while in pulsed operation. A low-cost multimode interference bandpass filter based solely on standard fibers was employed in a sigma-shaped cavity design. By bending the fiber filter, the spectrum could be continuously shifted by up to 11.6 nm without interrupting pulsed operation, and output powers of more than 3.3 mW at pulse durations below 350 fs were achieved.