Ruwei Zhao

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.

Femtosecond solid-state laser based on a few-layered black phosphorus saturable absorber.

In this Letter, a high-quality, few-layered black phosphorus (BP) saturable absorber (SA) was fabricated successfully, and a femtosecond solid-state laser modulated by BP-SA was experimentally demonstrated for the first time, to the best of our knowledge. Pulses as short as 272 fs were achieved with an average output power of 0.82 W, corresponding to the pulse energy of 6.48 nJ and peak power of 23.8 MW. So far, these represent the shortest pulse duration and highest output power ever obtained with a BP-based mode-locked solid-state laser. The results indicate the promising potential of few-layered BP-SA for applications in solid-state femtosecond mode-locked lasers.

Dual-wavelength, passively Q-switched Tm:YAP laser with black phosphorus saturable absorber

A compact saturable absorber mirror (SAM) based on multi-layered black phosphorus (BP) nanoplatelets was fabricated and successfully used as an efficient saturable absorber (SA) in a passively Q-switched Tm:YAP laser at 1.9 μm. With the BP SAM, Q-switched pulses with duration of 181 ns and average output power of 3.1 W were generated at a pulse repetition rate of 81 kHz, resulting in a pulse energy of 39.5 μJ, to the best of our knowledge, which is the record among the reports on BP SA-based Q-switched lasers. In addition, the simultaneous dual-wavelength Q-switched operation at both 1969 and 1979 nm has been observed. The results indicate the promising potential of multi-layered BP nanoplatelets as SAs for achieving efficient pulsed lasers at around 2 μm.

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.

High-power passively mode-locked laser at 1062.4 nm based on Nd:LaGGG disordered crystal

A diode-pumped passively continuous-wave mode-locked Nd:(La(x)Gd(1-x))3Ga5O12 (Nd:LaGGG) laser at 1062.4 nm with a semiconductor saturable absorber mirror was demonstrated for the first time, to the best of our knowledge. Pulses with duration of 12.78 ps were produced at a repetition rate of 59.8 MHz. A maximum average mode-locked output power of 3.18 W was obtained at the absorbed pumped power of 10.12 W, corresponding to a slope efficiency of 35.7% and a peak power of 4.2 kW. As far as we know, this is the highest power obtained in the passively mode-locking operation with Nd3+-doped disordered garnet crystals.

Passively mode-locked 1.34 μm bulk laser based on few-layer black phosphorus saturable absorber

By using few-layer black phosphorus (BP) as saturable absorber, an efficient mode-locked Nd:GdVO4 bulk laser operating at 1.34 μm was realized. An average output power of 350 mW was achieved with a slope efficiency of 15%. The corresponding mode-locking pulse repetition rate, pulse duration and pulse energy were 58.14 MHz, 9.24 ps and 3.0 nJ, respectively. To the best of our knowledge, the pulse width is the shortest among the mode-locked 1.34 μm neodymium lasers ever obtained with other two-dimensional materials saturable absorber. The results clearly indicate the few-layered BP is a kind of promising saturable absorber for ultrafast 1.34 μm lasers.

759 fs pulse generation with Nd 3+ -doped CNGS ordered crystal based on a semiconductor saturable absorber mirror

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.

Third-order nonlinearity and saturable absorbed performance of Cr 4+ :Gd 3 Ga 5 O 12 crystal

In this work, the third-order nonlinear optical properties and saturable absorbed performance of Cr4+-doped Gd3Ga5O12 (Cr4+:GGG) crystal were investigated. By using the Z-scan technique, the third-order nonlinear properties were analyzed systematically. Compared with Cr4+:YAG crystal, Cr4+:GGG crystal has a large third-order nonlinear refractive index, ground-state absorption, and excited-state absorption cross section. It has been successfully employed as a saturable absorber for passively Q-switched and Q-switching mode-locked lasers in this paper. In the Q-switched regime, the maximum average output power of 600 mW was obtained with the shortest pulse width of 4.76 ns and the repetition rate of 41.4 kHz, corresponding to single pulse energy and pulse peak power of 14.5 µJ and 3 kW, respectively. For the Q-switching mode-locking operation, the maximum output power of 468 mW was obtained with a repetition rate of 141.2 MHz. The results indicate that Cr4+:GGG crystal has the potential to be used for passive Q-switching and mode-locking laser generation.