Hainian Han

70-fs mode-locked erbium-doped fiber laser with topological insulator.

Femtosecond optical pulses have applications in optical communication, astronomical frequency combs, and laser spectroscopy. Here, a hybrid mode-locked erbium-doped fiber (EDF) laser with topological insulator (TI) is proposed, for the first time to our best knowledge. The pulsed laser deposition (PLD) method is employed to fabricate the fiber-taper TI saturable absorber (TISA). By virtue of the fiber-taper TISA, the hybrid EDF laser is passively mode-locked using the nonlinear polarization evolution (NPE), and emits 70 fs pulses at 1542 nm, whose 3 dB spectral width is 63 nm with a repetition rate and transfer efficiency of 95.4 MHz and 14.12%, respectively. Our experiments indicate that the proposed hybrid mode-locked EDF lasers have better performance to achieve shorter pulses with higher power and lower mode-locking threshold in the future.

Generation of dark solitons in erbium-doped fiber lasers based Sb(2)Te(3) saturable absorbers.

Dark solitons, which have better stability in the presence of noise, have potential applications in optical communication and ultrafast optics. In this paper, the dark soliton formation in erbium-doped fiber lasers based Sb(2)Te(3) saturable absorber (SA) is first experimentally demonstrated. The Sb(2)Te(3) SA is fabricated by using the pulsed laser deposition method. The generated dark solitons are centered at the wavelength of 1530 nm and repetition rate of 94 MHz. Analytic solutions for dark solitons are also obtained theoretically.

Tungsten disulfide saturable absorbers for 67 fs mode-locked erbium-doped fiber lasers

In this paper, we demonstrate 67 fs pulse emitting with tungsten disulfide (WS2) in mode-locked erbium-doped fiber (EDF) lasers. Using the pulsed laser deposition method, WS2 is deposited on the surface of the tapered fiber to form the evanescent field. The fiber-taper WS2 saturable absorber (SA) with the large modulation depth is fabricated to support the ultrashort pulse generation. The influences of the WS2 SA are analyzed through contrastive experiments on fiber lasers with or without the WS2 SA. The pulse duration is measured to be 67 fs, which is the shortest pulse duration obtained in the mode-locked fiber lasers with two dimensional (2D) material SAs. Compared to graphene, topological insulator, and other transition metal dichalcogenides (TMDs) SAs, results in this paper indicate that the fiber-taper WS2 SA with large modulation depth is a more promising photonic device in mode-locked fiber lasers with the wide spectrum and ultrashort pulse duration.

Efficient femtosecond mode-locked Nd,Y:SrF2 laser

An efficient femtosecond mode-locked laser using Nd and Y-codoped SrF2 crystal as the gain medium is presented in this letter. A 332 fs pulse centered at 1057 nm with a repetition rate of 89.8 MHz, a spectral width of 4.3 nm, and a mode-locked output power of up to 395 mW has been obtained under 1 W pump power, corresponding to an optical-to-optical efficiency of 39.5% and a slope efficiency of 69%. To the best of our knowledge, this is the highest optical efficiency in femtosecond Nd-doped crystal lasers.

Contrast enhancement in a Ti:sapphire chirped-pulse amplification laser system with a noncollinear femtosecond optical-parametric amplifier

We experimentally demonstrated the contrast enhancement in a Ti:sapphire chirped-pulse amplification (CPA) laser with a noncollinear femtosecond optical-parametric amplifier. A total gain of 3.4 × 10(4) and pulse energy of 26 μJ were achieved. With the clean high-energy seeding pulse, the contrast ratio of the main amplified laser pulse to the amplified spontaneous emission in the Ti: sapphire CPA laser system was improved to around 10(10) within the time scale of hundreds of picoseconds.

Breathers in a hollow-core photonic crystal fiber

In this work breathers are obtained in a hollow-core photonic crystal fiber (HC-PCF) for the first time. The nonlinear Schr?dinger equation describing the propagation of pulses in a HC-PCF is investigated using the Hirota bilinear method and the auxiliary function method. Analytic breather solutions are derived by an appropriate choice of parameters. Dynamical behavior of breathers is exhibited, and the influences of different parameters on the characteristics of breathers are discussed. The presented results could be used in fiber lasers, nonlinear optics and Bose?Einstein condensates.

Diode-pumped 88-fs Kerr-lens mode-locked Yb:Y3Ga5O12 crystal laser

We realized a stable Kerr-lens mode-locked operation in a diode-pumped Yb:Y₃Ga₅O₁₂ laser. Pulses as short as 88 fs at the center wavelength of 1042 nm were obtained at a repetition rate of 159.3 MHz. The maximum output power was 104 mW under the incident pump power of 3.9 W. By comparing the mode-locked characteristics under different output transmissions, we obtained pulses with the highest output power of 330 mW and a duration of 149 fs. To the best of our knowledge, this is the first demonstration of a Kerr-lens mode-locked Yb:Y₃Ga₅O₁₂ laser.

Diode-pumped Kerr-lens mode-locked Yb:LYSO laser with 61fs pulse duration

A stable diode pumped Kerr-lens mode-locked (KLM) Yb:LuYSiO5 (Yb:LYSO) laser of generating 61 fs pulses at a central wavelength of 1055.4 nm is experimentally demonstrated. This is, to the best of our knowledge, the first demonstration of femtosecond KLM operation in Yb:LYSO laser, and it is believed that 61 fs is the shortest pulse duration ever produced from an Yb-doped orthosilicate laser. The average output power of the mode-locked laser is 40 mW and the repetition rate is 113 MHz.

Quasi-steady-state air plasma channel produced by a femtosecond laser pulse sequence

A long air plasma channel can be formed by filamentation of intense femtosecond laser pulses. However, the lifetime of the plasma channel produced by a single femtosecond laser pulse is too short (only a few nanoseconds) for many potential applications based on the conductivity of the plasma channel. Therefore, prolonging the lifetime of the plasma channel is one of the key challenges in the research of femtosecond laser filamentation. In this study, a unique femtosecond laser source was developed to produce a high-quality femtosecond laser pulse sequence with an interval of 2.9 ns and a uniformly distributed single-pulse energy. The metre scale quasi-steady-state plasma channel with a 60–80 ns lifetime was formed by such pulse sequences in air. The simulation study for filamentation of dual femtosecond pulses indicated that the plasma channel left by the previous pulse was weakly affected the filamentation of the next pulse in sequence under our experimental conditions.

A 350MHz Ti:sapphire laser comb based on monolithic scheme and absolute frequency measurement of 729nm laser

We realized a novel frequency comb based on femtosecond Ti:sapphire laser with 350MHz repetition rate and monolithic scheme for carrier-envelope-offset frequency generation. Long-term stabilization of more than 9 hours was demonstrated by simultaneously locking repetition rate (frep) and carrier-envelope-offset frequency (fceo) to an atomic clock. The Allan deviations of fceo and frep are 2.3×10-13 and 1.5×10-15 at 100s averaging time, respectively, and the reproducibility of fceo with high accurate performance is also verified by comparison of the locking results recorded in 3 different days. By avoiding the extra noise induced by photonic crystal fiber, we obtained the accumulated phase error increase from in-loop to out-of-loop as small as 12 mrad [1Hz, 100kHz]. Furthermore, the absolute optical frequency of a stabilized 729nm Ti:sapphire laser which is referenced to a ultra-low expansion (ULE) cavity is measured by the comb and determined to be 411041985391583±10Hz.