Fei Lou

A tri-wavelength synchronous mode-locked Nd:SYSO laser with a semiconductor saturable absorber mirror

We report on the generation of passive mode locking of a Nd:Sc0.2Y 0.8SiO5 (Nd:SYSO) laser using a semiconductor saturable absorber mirror. Linear polarized, tri-wavelength synchronous mode-locked pulses were obtained for laser emissions at 1075.55, 1076.80 and 1078.20 nm. An interference pattern was observed in the autocorrelation trace, the beat pulse had a repetition rate of 0.345 THz and the beat pulse width was 646 fs. Numerical simulation was conducted to clarify the formation of the autocorrelation trace.

Passively Q-switched 2 μm Tm:YAP laser based on graphene saturable absorber mirror

Using high-quality single-layer graphene as a saturable absorber, Tm:YAlO₃ (Tm:YAP) crystal as the gain medium, we demonstrated a laser-diode-pumped, compact, passively Q-switched (PQS) solid-state laser in the 2 μm region. The maximum average output power was 362 mW, with the corresponding largest pulse repetition rate and pulse energy of 42.4 kHz and 8.5 μJ, respectively. Under the same pump power, the pulse width of 735 ns was obtained, which is, to our best knowledge, the shortest pulse width among Tm-doped solid-state PQS lasers using graphene saturable absorber mirrors.

Multi-layered black phosphorus as saturable absorber for pulsed Cr:ZnSe laser at 2.4 μm

A high-quality black phosphorus (BP) saturable-absorber mirror (SAM) was successfully fabricated with the multi-layered BP, prepared by liquid-phase exfoliation (LPE) method. The modulation depth and saturation power intensity of BP absorber were measured to be 10.7% and 0.96 MW/cm(2), respectively. Using the BP-SAM, we experimentally demonstrated the mid-infrared (mid-IR) pulse generation from a BP Q-switched Cr:ZnSe laser for the first time to our best knowledge. Stable Q-switched pulse as short as 189 ns with an average output power of 36 mW was realized at 2.4 μm, corresponding to a repetition rate of 176 kHz and a single pulse energy of 205 nJ. Our work sufficiently validated that multi-layer BP could be used as an optical modulator for mid-IR pulse laser sources.

High-efficiency femtosecond Yb:Gd 3 Al 0.5 Ga 4.5 O 12 mode-locked laser based on reduced graphene oxide

A diode-pumped Yb-doped Gd(3)Al(0.5)Ga(4.5)O(12) mode-locked bulk laser based on chemically reduced graphene oxide (RGO) has been demonstrated for the first time to our best knowledge. Pulses with duration of 643 fs were produced at the central wavelength of 1041.1 nm. A maximum average output power of 0.8 W was obtained from the RGO mode-locked laser, corresponding to a slope efficiency of 20.1% and a peak power of 27.6 kW. The results indicate that RGO is suitable for obtaining high-power and high-efficiency ultrafast lasers.

Growth and optical properties of a new CGG-type laser crystal Nd 3+ :CNGS

A novel CGG-type laser crystal of Nd3+:CNGS is characterized, including crystal growth, structure, refractive index, spectroscopic and laser performance. For Nd3+:CNGS crystal, the unit-cell parameters are a = 0.88897 ( ± 8.89 × 10−5) nm, c = 0.497998 ( ± 4.85 × 10−5) nm and V = 0.28219 nm3. The refractive index no and ne of Nd3+:CNGS were calculated to be 1.772 and 1.854 respectively at 1065 nm. The transmittance spectra of Nd3+:CNGS were measured, four main absorption peaks were located at 586 nm, 748 nm, 804 nm and 804 nm respectively. The absorption cross-section in z-axis is 6.08 × 10−20 cm2 around 804nm. The strongest emission peak of the fluorescence spectra was located at 1064 nm with the emission cross-section of 6.81 × 10−20 cm2 for E//x polarization and the fluorescence lifetime was 255.6 μs. Moreover, the continuous-wave laser at 1065 nm was obtained with the maximum output power of 1.43 W in the z-cut sample for the first time to the best of our knowledge, the optical conversion efficiency was 29.3% and the slope efficiency was 31.0%, which indicated that Nd3+:CNGS crystal should be a promising gain material.

Efficient High-Peak-Power Wavelength-Switchable Femtosecond Yb:LGGG Laser

A systematic study of the spectral properties and ultrafast lasing characteristics of Yb:(LuxGd1-x)3Ga5O12(x = 0.062) (Yb:LGGG) disordered crystal was reported for the first time. The broad fluorescence spectral lines indicate a great potential of Yb:LGGG for tunable and ultrafast laser application. In the lasing experiment, a passively mode-locked Yb:LGGG laser was realized, which generated a maximum average power of 1.3 W with pulse duration of 324 fs at the central wavelength of 1029.6 nm, corresponding to a slope efficiency as high as 41.6%. The pulse energy and peak power were calculated to be 22.4 nJ and 69.2 kW. By optimizing the cavity design, the shortest pulse duration of 188 fs was achieved at the central wavelength of 1026.8 nm. In this case, the maximum average output power of 0.77 W was generated with a slope efficiency of 27.1%. The experimental results show the excellent potential of Yb:LGGG crystal for high-efficiency and high-peak-power femtosecond laser.

Triwavelength synchronously mode-locked fiber laser based on few-layered black phosphorus

A triwavelength synchronously mode-locked erbium-doped fiber laser with black phosphorus (BP) was demonstrated. The BP was proved to be not only an excellent saturable absorber (SA) but also a strong nonlinear material benefiting the stabilization of a multiwavelength fiber laser. The laser worked for a long time at three synchronous wavelengths of 1557.2, 1557.7, and 1558.2 nm. The autocorrelation trace of 9.41 ps pulses showed an interference beating of 0.06 THz, corresponding to a beating period of 16.37 ps. To the best of our knowledge, this is the first report on the usage of BP as an SA for building a multiwavelength synchronous mode-locked fiber laser.

Flux method growth of bulk MoS2 single crystals and their application as a saturable absorber

Molybdenum disulfide (MoS2) has attracted a great deal of attention because of its outstanding physical, chemical and optoelectronic properties. The method used to prepare large sized MoS2 crystals of very high quality is still an important issue for determining the feasibility of its application. Herein, we propose a novel Sn flux method to grow single crystal MoS2, and bulk MoS2 single crystals with a size of 3 mm × 5 mm were successfully obtained by using a cooling rate of 2–4 °C h−1. The growth mechanism of the MoS2 crystal in Sn flux was investigated in detail using optical microscopy and atomic force microscopy (AFM). The obvious screw dislocation steps that are revealed suggest that the growth of MoS2 is controlled by a screw-dislocation-driven (SDD) spiral growth mechanism. The flux-grown MoS2 crystals were exfoliated to produce high-quality large-scale films using the liquid-phase exfoliation method. Using ultrathin MoS2 films as a saturable absorber, a passively Q-switched laser at a wavelength of 1.06 μm was constructed and operated, with a narrow pulse width of 326 ns.

1342 nm High-Power Picosecond Pulse Generation by a Passively Mode-Locked

A high-power diode-pumped passively mode-locked Nd:YVO4 laser at 1342 nm with a semiconductor saturable absorber mirror is demonstrated in this letter. With the optimum cavity design, the maximum average output power of 2.19 W is obtained with an incident pump power of 12.35 W, corresponding to a slope efficiency of 19% and an optical conversion efficiency of 17.7%. The minimum pulse duration is measured to be 8.6 ps with the repetition rate of 63.4 MHz. The single pulse energy and peak power are calculated to be 34.5 nJ and 4 kW, respectively.

{\rm Nd}{:}{\rm YVO}_{4}

A diode-pumped passively continuous wave mode-locked laser at 1064.2 nm based on an ordered Nd:CNGS crystal has been experimentally investigated (for the first time, to our knowledge). Stable mode-locked pulses with a duration of 759 fs were produced at a repetition rate of 43.2 MHz. It is the shortest pulse generation of mode-locked lasers based on Nd3+-doped ordered crystal, as far as we know. A maximum average mode-locked output power of 133 mW was obtained at the absorbed pumped power of 6.7 W, and corresponding single-pulse energy and peak power were determined to be 3.1 nJ and 4.1 kW, respectively. The results indicate that the Nd:CNGS as an ordered crystal is indeed a potential candidate as a femtosecond laser gain medium.