Jian Ning

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 power single-frequency Innoslab amplifier.

A laser diode array (LDA) end-pumped continuous-wave single-frequency Innoslab amplifier has been demonstrated. The Gaussian ray bundle method was used to model the light propagation in the Innoslab amplifier for the first time to the best of our knowledge. With discrete reflectors, the maximum output of 60 W with a linewidth of 44 MHz was achieved under the pump power of 245 W, corresponding to the optical-optical efficiency of 24.5%. The beam quality factor M2 at the output power of 51 W in the horizontal and vertical direction was measured to be 1.4 and 1.3, respectively. The long-term power instability in 2 h was less than 0.25%.

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.

Passively Q-switched mode-locking of Tm:YAP laser based on Cr:ZnS saturable absorber

Using a Cr:ZnS wafer as the saturable absorber, diode-pumped passively Q-switched mode-locking of a Tm:YAP laser at 1976 nm has been realized for the first time, to the best of our knowledge, and nearly 100% modulation depth of Q-switched mode-locking was achieved. The width of the mode-locked pulse was estimated to be about 980 ps with a repetition rate of 350 MHz within a roughly 300-ns-long Q-switched pulse envelope. A maximum output power of 940 mW was obtained, corresponding to the Q-switched pulse energy of 0.55 mJ. The emission wavelength evolution between the continuous-wave and Q-switched mode-locked operations was presented and discussed. The experimental results indicate that the Cr:ZnS absorber is a promising saturable absorber for passively Q-switched mode-locking operation around 2 μm.

Diode End Pumped Continuous Wave and Graphene Q-Switched Tm:LGGG Lasers

A detailed investigation was conducted on continuous wave, wavelength tunable, and graphene passively Q-switched (PQS) lasers of Tm:LGGG crystal. In continuous wave operation, a maximum average output power of 2.26 W at 2003 nm was obtained under the absorbed power of 12.1 W, giving an optical-to-optical conversion efficiency of 18.7% and a slope efficiency of 23.6%. By using a quartz plate, the emission spectrum could be tuned from 1907.5 to 2055.9 nm, corresponding to a full-width at half-maximum (FWHM) of 83 nm. Dual-wavelength operation could be obtained by rotating the quartz plate at an appropriate angle. In graphene PQS regime, the Tm:LGGG laser produced a 1.29-μs pulse under the pulse repetition frequency of 43.9 kHz, corresponding to a pulse energy of 3.19 μJ.

Dual-wavelength synchronously mode-locked Nd:LaGGG laser operating at 1.3 μm with a SESAM

We have demonstrated a diode-end-pumped synchronously dual-wavelength mode-locked Nd3+:(La0.1Gd0.9)3Ga5O12 (Nd:LaGGG) laser operating at 1.3 μm with a semiconductor saturable absorber mirror (SESAM) for the first time to our knowledge. The mode-locked laser emitted an average output power of 530 mW with two wavelengths centered at 1331.2 and 1336.5 nm. The pulse duration and repetition rate were 17 ps and 37.6 MHz, respectively. A frequency beat signal with respect to two stationary wave interference patterns of 0.876 THz was observed from the autocorrelation trace.

83.4 W, 17.69 kHz spectral bandwidth, continuous-wave, beam densely folded Innoslab amplifier

Combined with the advantages of the narrow bandwidth of a non-planar ring oscillator seed laser and the structure of a direct pumped Innoslab amplifier, a high-efficiency and high-power continuous-wave (CW) single-frequency laser was obtained by densely folding the seed laser beam in an Innoslab amplifier with a wedged multi-folded configuration. A maximum output power of 83.4 W of a single-frequency amplifier with a bandwidth of 17.69 kHz was obtained under a pump power of 234 W, corresponding to an optical-to-optical conversion efficiency of 33.2%. The beam quality factor M2 at the maximum output power in horizontal and vertical directions was measured to be 1.15 and 1.24, respectively. The long-term power instability in 2 h was less than 1.63%.