Mode coherence measurements across a 1.5 THz spectral bandwidth of a passively mode-locked quantum dash laser

The mode coherence of adjacent and non-adjacent spectral modes of a passively mode locked quantum dash (QDash) semiconductor laser are deduced through radio frequency beat-tone linewidth measurements. A wavelength conversion scheme that uses degenerate four wave mixing in a semiconductor optical amplifier is proposed which considerably extends the mode spacing beyond the limit imposed by conventional fast-photodetection and electrical spectrum analysis of around 100 GHz. Using this scheme, the mode coherence of the QDash laser was measured out to the thirty-first harmonic, or a mode separation of 1.5 THz.     

Ouput characteristics of a passively mode-locked ruby laser

Characteristics of the pulse train from a ruby laser have been studied at different output intensity levels. At a low output level, broadening of the spectrum of the pulses is followed by a gradual increase of temporal width in the train. At a high output level, rapid deformation arises closer to the peak of the train, resulting in splitting of the pulses into several fragments. The width of a transform-limited pulse obtained at the beginning of the train was 28±2 picoseconds.     

All-fiber bidirectional passively mode-locked ring laser

We report the design and operation of a novel all-fiber bidirectional passively mode-locked ring laser. An erbium-doped fiber was chosen as the active element in a ring cavity arrangement. A short segment of a fiber taper embedded in carbon nanotubes/polymer composite, acting as a saturable absorber, was used to enable bidirectional mode locking. The laser generates two stable femtosecond pulse trains in opposite directions. A beat note of about 2 MHz, having a bandwidth of less than 2 kHz, is measured when the pulses propagating in opposite directions are (temporally) overlapped at a photodetector. We believe this device will find important applications in precision rotation sensing.     

Simulation of the passively mode-locked laser with a SESAM

By solving the Haus master equation through split step Fourier transform method, several programs which can simulate the soliton mode-locked dynamic processes of the passively mode-locked solid laser with a semiconductor saturable absorber mirror (SESAM) are established, based on a MATLAB environment. The pulse evolution equations are solved numerically. Sample calculations for a diode-pumped Nd³⁺:YVO₄ (0.5% doped) laser with a SESAM are presented to demonstrate the use of the simulation programs and the related formulas. Several theoretical results such as the pulse width, the peak power and the average output power are obtained with a given cavity structure, which are in good agreement with the reported experimental results.     

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.     

Pulse dynamics in a passively mode-locked chirped-pulse fiber laser

We report experimental and numerical results on the new pulse dynamics in a passively mode-locked ytterbium-doped fiber laser operating in the chirped-pulse regime. Due to the negligible nonlinearity of added highly-positive GVD segment in the purely-normal-dispersion regime, highly-positive chirped pulses can be formed through weak intra-cavity temporal and spectral breathing. Numerical simulations reveal intra-cavity pulse evolution with local temporal stretching phenomena and pulse shaping properties.     

Dissipative soliton resonance in a passively mode-locked fiber laser

The phenomenon of dissipative soliton resonance (DSR) predicts that an increase of pulse energy by orders of magnitude can be obtained in laser oscillators. Here, we prove that DSR is achievable in a realistic ring laser cavity using nonlinear polarization evolution as the mode-locking mechanism, whose nonlinear transmission function is adjusted through a set of waveplates and a passive polarizer. The governing model accounts explicitly for the arbitrary orientations of the waveplates and the polarizer, as well as the gain saturation in the amplifying medium. It is shown that DSR is achievable with realistic laser settings. Our findings provide an excellent design tool for optimizing the mode-locking performance and the enhancement of energy delivered per pulse by orders of magnitude.     

高重复频率全光纤被动锁模掺铒光纤激光器

报道了一种高重复频率全光纤非线性偏振旋转锁模掺铒光纤激光器, 获得了重复频率217 MHz的锁模脉冲输出. 该激光器使用一个偏振相关隔离器和一个偏振控制器即可获得稳定的锁模脉冲输出, 结构简单, 系统稳定. 激光器锁模脉冲的脉冲宽度为69 fs, 3 dB光谱宽度为56 nm, 射频频谱信噪比为76 dB.     

Diode-pumped passively mode-locked Nd:CLNGG laser

Passive mode-locking of a diode-pumped Nd:CLNGG laser was demonstrated for the first time to our knowledge. The laser operated at a central wavelength of 1061.2 nm with a maximum average output power of 101 mW. The mode-locked pulses have pulse duration of 2.0 ps, a spectral bandwidth of 1.2 nm and a repetition rate of 88.4 MHz. The mode locking of the laser was enabled by a semiconductor saturable absorber mirror (SESAM).     

Period-doubling of multiple solitons in a passively mode-locked fiber laser

We report on the experimental observation of period-doubling of randomly distributed multiple solitons in a passively mode-locked fiber laser. We show that after a period-doubling bifurcation, the period of each soliton in the cavity becomes doubled. However, the intensity variation of the solitons is not necessarily synchronized, indicating that their period-doubling is unrelated. Numerical simulations verified the experimental observations.     

Intrinsic dual-wavelength operation of a passively mode-locked fiber ring laser

We report on the dual-wavelength operation in an erbium-doped fiber ring laser mode-locked through nonlinear polarization rotation technique. In addition to dual-wavelength continuous wave operation, alternative mode-locking at the dual wavelengths was realized experimentally. By analyzing the transmissivity of the laser cavity, we find the dual-wavelength operation is an intrinsic feature of the laser associating with the dispersive cavity loss. Numerical simulations confirm the experimental and theoretical results and further demonstrate that the location of the dual wavelengths and the separation between them closely depend on the cavity birefringence and the profile of the gain medium.     

Chaotic dynamics of a passively mode-locked soliton fiber ring laser

We report on the experimental and numerical studies of the chaotic dynamics of a soliton fiber ring laser passively mode-locked by using the nonlinear polarization rotation (NPR) technique. Period-doubling route to chaos on the soliton repetition rate of either the single pulse soliton or the bound solitons of the laser was experimentally observed. Based on a coupled complex Ginzburg-Landau equation model and also taking into account the laser cavity effect, we further show numerically that the period-doubling bifurcations and route to chaos are intrinsic properties of the laser, whose appearance is independent of the details of the laser cavity design and the laser soliton operation. Property of the solitons under the dynamical bifurcations is also numerically investigated.     

Rains of solitons in a figure-of-eight passively mode-locked fiber laser

We report experimental observation of rains of solitons in figure-of-eight fiber laser passively mode-locked through nonlinear optical loop mirror. Soliton pulses are created from an extended noisy background and drift until they reach a condensed phase comprising several tens of aggregated solitons. The observation of this dynamics tends to strengthen the idea of the universality of the collective behavior of solitons.     

Nearly transform-limited optical pulse from a passively mode-locked laser diode

An optical ultra-short pulse train with a duration of 2.9 ps was successfully generated from a passively mode-locked laser diode. The time-bandwidth product was 0.43, and it was very close to the transformlimited value of a Gaussian waveform. The highest peak power of 10 mW in an InP-based passively mode-locked laser has been achieved. The laser is promisng as an optical source for an ultra-high-speed bit rate transmission system, especially for the optical time division multiplexing (OTDM) system.     

Bidirectional passively mode-locked soliton fiber laser with a four-port circulator

We present an all-fiber bidirectional passively mode-locked soliton laser with what we believe is a novel cavity configuration. Using a four-port circulator, we incorporate two different semiconductor saturable absorber mirrors (SESAMs) into the laser cavity, which enables bidirectional mode locking. The laser allows the generation of two independent countercirculating mode-locked pulse trains, each with an individual fundamental repetition rate that can be adjusted by varying the SESAM pigtail length. Two countercirculating pulse trains with repetition rates of 21.3 and 15.2 MHz are obtained simultaneously. By controlling the intracavity loss imposed on these two pulse trains, either one of the two pulse trains can be switched on or off. The bidirectional operation with other repetition rates is also demonstrated.     

Bound soliton pulses in a passively mode-locked fibre ring laser

The bound solitons in a passively mode-locked fibre ring laser are observed and their formation mechanism is summarized in this paper. In order to obtain stable bound solitons, a strong CW laser field at the centre of the soliton spectral is necessary to suppress and synchronize the random soliton phase variations.     

Diode-pumped passively mode-locked femtosecond Yb:CTGG laser

A diode-pumped passively mode-locked Yb:CTGG disordered crystal laser has been demonstrated for the first time to our knowledge. With a semiconductor saturable absorber mirror for passive mode locking and two Gires–Tournois interferometer mirrors for dispersion compensation, pulses as short as 389 fs at a repetition rate of 45 MHz were obtained at the central wavelength of 1,037.8 nm. The maximum average power was 420 mW, corresponding to pulse energy of 9.3 nJ and peak power of 24 kW.     

All-fiber wavelength tunable passively mode-locked erbium-doped ring laser

An all-fiber, wavelength-tunable, passively mode-locked erbium-doped ring laser is presented. Erbium-doped fibers (EDF) are used as the gain media because of their large gain bandwidth. Nonlinear polarization rotation (NPR) plays the dual role of realizing mode-locking and effectively adjusting the intensity-dependent loss of the cavity. An unbalanced Mach-Zehnder interferometer (UMZI) is used as a tunable optical beam filter. By using the UMZI and adjusting the polarization controllers (PCs), a sub-picosecond mode-locking laser is realized that is self-starting with central lasing wavelengths that can be accurately tuned over a range of about ~ \sim 30 nm and also has controllable spacings between different tunable wavelengths.     

Wavelength-tunable prism-coupled external cavity passively mode-locked quantum-dot laser

A wavelength-tunable mode-locked quantum dot laser using an In As/Ga As quantum-dot gain medium and a discrete semiconductor saturable absorber mirror is demonstrated.A dispersion prism,which has lower optical loss and less spectral narrowing than a blazed grating,is used for wavelength selection and tuning.A wavelength tuning range of 45.5 nm(from1137.3 nm to 1182.8 nm) under 140-m A injection current in the passive mode-locked regime is achieved.The maximum average power of 19 m W is obtained at the 1170.3-nm wavelength,corresponding to the single pulse energy of 36.5 p J.