Dingyuan Tang

A resonantly-pumped tunable Q-switched Ho:YAG ceramic laser with diffraction-limit beam quality

We demonstrated a Q-switched Ho:YAG ceramic laser operating at 2097 nm. The Ho:YAG ceramic laser was resonantly pumped by a Tm:YLF laser at 1908 nm. The laser performance with two Ho-doping concentrations of Ho:YAG ceramics in a U-shaped resonator was studied. Different pump spots were investigated to obtain high extract efficiency. The wavelength of Ho:YAG ceramic laser was tuned from 2090.70 nm to 2098.10 nm. The Q-switched pulse energy were 9.6 mJ at a pulse repetition frequency (PRF) of 200 Hz and 10.2 mJ at a PRF of 100 Hz, respectively. The beam quality M(2) factors were measured to be less than 1.1 in both directions.

Comparison of the 1319 and 1338 nm Dual-Wavelength Emission of Neodymium-Doped Yttrium Aluminum Garnet Ceramic and Crystal Lasers

The 1319 and 1338 nm dual-wavelength operation of neodymium-doped yttrium aluminum garnet (Nd:YAG) ceramic and single-crystal lasers was experimentally compared. It was found that, although the single-crystal lasers preferably to oscillate at 1319 nm under strong pumping, the ceramic lasers tend to operate at 1338 nm, indicating the existence of a subtle difference between the 4F3/2–4I13/2 transitions of the Nd3+ ions in the Nd:YAG crystal and ceramic lasers.

Efficient RTP-based OPO intracavity pumped by an acousto-optic Q-switched Nd:YVO 4 laser

This Letter describes an intracavity pumped optical parametric oscillator (OPO) based on noncritical phase matching RbTiOPO4 (RTP) crystal driven by a laser diode end-pumping acousto-optic Q-switched Nd:YVO4 laser. Simultaneous efficient signal light at 1.6 μm and idler light at 3.1 μm outputs were obtained. At an incident pump power of 10.5 W and a Q-switching pulse repetition frequency of 60 kHz, 1.42 W at center wavelength of about 1619 nm and 0.38 W at 3108 nm were achieved, with the diode to OPO total output conversion efficiency up to 17.1%. The pulse width is about 6.5 ns for the signal light corresponding to the fundamental light at 1064 nm of about 10 ns. The spectral widths of the signal and idler light are narrower than 0.5 and 1.0 nm. The result shows that the RTP crystal is an efficient crystal to generate eye-safe and mid-infrared lights by making full use of noncritical phase matching.

Vector Soliton Generation in a Tm Fiber Laser

Vector soliton generation is experimentally demonstrated in an all-fiber Tm/Ho-doped fiber laser operated at 1951 nm. To the best of our knowledge, it is the first clear evidence of group-velocity-locked vector soliton formation around 2 μm. Numerical simulation well reproduces the experimental observation and suggests that the central wavelength shift between the two orthogonal polarized components of the vector soliton is determined by the cavity birefringence. The central wavelength shift increased with the increasing of the cavity birefringence. However, the vector solitons become linearly polarized if the cavity birefringence is too strong. Experimental observation and numerical simulations both suggest that the vector soliton generation is wavelength independent.

Laser operation of diode-pumped Er,Yb co-doped YAG ceramics at 1.6 μm

1.6 μm eye-safe emission of a diode pumped Er,Yb co-doped YAG ceramic laser is firstly demonstrated. Operation of the ceramic laser under different ceramic sample lengths, co-doping concentrations and control temperatures were experimentally investigated. A maximum output power of 222 mW was achieved at an absorbed pump power of 8.1 W, corresponding to a conversion efficiency of 2.74%. Laser emission at 1.05 μm for transition of the Yb(3+) ions was also studied on the same ceramic samples. The results clearly show the existence of resonantly energy transfer from the Yb(3+) ions to Er(3+) ions.

High Power Continuous-Wave and Graphene Q-switched Operation of Er:YAG Ceramic Lasers at ~1.6 ㎛

We report on high-power continuous-wave operations of an Er:YAG ceramic laser in-band pumped by a cladding-pumped Er,Yb fiber laser at 1532 nm. With an output coupler of 10% transmission, the ceramic laser yielded 16.7 W of continuous-wave output at 1645 nm for 28.8 W of incident pump power, corresponding to a slope efficiency of 61.0% with respect to the incident pump power. The lasing wavelength switched to 1617 nm when output couplers of > 20% transmission were used. Up to 16.2 W of 1617 nm output was generated for 33.0 W of incident pump power, corresponding to a slope efficiency of 51.8%. Graphene Q-switched operation of Er:YAG cermic laser at 1645 nm was also demonstrated with stable pulses of 30-74 kHz repetition rates and 1.5-6.4 μs pulse widths.

Generation of 2-

We propose an experimental technique for efficient 2- μm light generation based on the intracavity noncritical phase matching optical parametric oscillator (OPO). Intra-cavity pumped by a diode pumped actively Q-switched Nd:YVO4 laser operating at 1.3 μm, we have achieved efficient 2093-nm signal beam emission making full use of noncritical phase matching KTA-OPO. At a diode pump power of 9.8 W and a Q-switching repetition rate of 30 kHz, a signal beam with a spectral linewidth of ~ 1 nm and an average power of 1.01 W have been obtained, giving a diode pump power to signal power conversion efficiency of 10.3%. The short pulse width of ~ 3.4 ns is achieved, which is much shorter than other approaches with Q-switched operation to generate 2-μm laser beams.

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An erbium-doped polycrystalline yttrium aluminum garnet ( Er:Y3Al5O12, and Er:YAG) ceramic laser is passively Q-switched by a few-layer graphene at 1617 nm. When in-band is pumped by a continuous-wave Er,Yb fiber laser at 1532 nm, the laser produces a continuous and stable train of Q-switched pulses with pulse energy of as much as 12.2 μJ, pulse repetition rate of 54.4 kHz, and average output power of 662 mW.

Light Based on a Noncritical Phase Matching OPO Technique

We show both theoretically and experimentally the temporal cavity soliton formation in a fiber ring laser. The cavity-induced modulation instability can automatically destabilize the CW operation of a fiber ring laser, transferring the CW laser beam into a periodic pulse train. Under strong laser emission, and particularly under the action of the effective gain bandwidth limitation, each pulse of the periodic pulse train could be further shaped into a dissipative soliton. The features of the temporal cavity solitons thus formed are experimentally studied and their similarity and difference to those of the mode-locked fiber lasers are discussed.

Efficient Graphene Q-Switching of an In-Band Pumped Polycrystalline Er:YAG Ceramic Laser at 1617 nm

A polycrystalline ceramic Tm3+-doped yttrium aluminum garnet (Tm:Y3Al5O12, Tm:YAG) laser based on the novel fiber-bulk hybrid configuration is demonstrated using a high-power and tunable Er,Yb co-doped fiber laser as the pump source. Lasing characteristics of a 4.0 at. % Tm:YAG ceramic are investigated at different pump wavelengths from 1617 to 1625 nm. With an output coupler of 10% transmission, a maximum output power of 3.9 W is obtained at 2013.2 nm under an 8.8 W incident pump power at the Tm:YAG absorption peak of 1620.4 nm, corresponding to a slope efficiency of 50.1% with respect to the incident pump power.