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We demonstrate an 806 nm laser diode end-pumped continuous-wave (CW) and actively Q-switched (AQS) orthogonally-polarized dual-wavelength Nd:YLF laser operating at 1314 and 1321 nm. Benefitting from the small difference of the stimulated emission cross sections at 1314 and 1321 nm in Nd:YLF crystal, the power equalized emissions at both wavelengths were achieved by simply titling the output coupler. A maximum CW output power of 9.2 W was obtained with the incident pump power of 32.5 W, giving an optical-to-optical conversion efficiency of approximately 28% and a slope efficiency of approximately 33%. Furthermore, active Q-switching was realized by inserting a Brewster-cut acousto optic modulator. For an incident pump power of 30 W, this oscillator delivered an average power of 6.5 W at a pulse repetition frequency (PRF) of 20 kHz, and a pulse energy of 2.6 mJ with a peak power of approximately 72 kW at a PRF of 1 kHz.

The effect of Nd3+ co-doping as sensitizer and deactivator to the Er3+ ion for enhancing ~2.7 μm emissions under 808nm LD pump was first studied in the Er/Nd co-doped PbF2 crystal. The Er0.01Nd0.02Pb0.97F2 crystal has been successfully grown by the Bridgman method, and the crystals’ fluorescence emission properties and energy transfer mechanisms of series crystals were investigated. It can be seen that through the Nd3+ ion, the lower energy level of Er3+: 4I13/2 has been depopulated, and the upper energy level of Er3+: 4I11/2 has been populated at the same time. Simultaneously, the energy transfer efficiency from the Er3+: 4I13/2 level to the Nd3+: 4I15/2 level is 84.06%, and from the Nd3+: 4F3/2 level to the Er3+: 4I11/2 level is 55.81%, respectively, which indicate that the Nd3+ ion is an effective deactivator and sensitizer ion for enhancing the ~2.7 μm emission in Er/Nd: PbF2 crystal. These advantages suggest that the Er/Nd: PbF2 crystal may be a potential material for ~2.7 μm mid-infrared lasers under the 808 nm LD pump.

An in-band pumped passively Q-switched (PQS) self-Raman laser with a c-cut Nd:YVO4 composite crystal is demonstrated for the first time to our knowledge. A Cr4+:YAG composite crystal was utilized to improve the stability and misalignment sensitivity of the resonator. The PQS self-Raman output performance was systematically investigated with different initial transmissions (T0) of the Cr4+:YAG and different transmissions (TS) of the Raman output coupler. In addition, the focus position of the incident pump beam and cavity length have been optimized during the experiment. With Cr4+:YAG of T0=90% and output coupler of TS=10%, the maximum average output power at 1178 nm was up to 2.53 W under the absorbed pump power of 20.6 W, corresponding to an optical-to-optical conversion efficiency of 12.3%. The pulse repetition frequency and pulse width were measured to be 39.1 kHz and 20.4 ns, respectively, and the corresponding pulse energy and peak power were calculated to be 64.7 μJ and 3.2 kW. At the full output power, the fluctuation of Raman output power was less than ±0.5% within one hour. To the best of our knowledge, we have improved the PQS self-Raman laser about 3.2 times.

The use of Tb3+ co-doping for the enhancement of Er3+: 4I11/2 → 4I13/2 mid-infrared emissions can conquer the self-termination bottleneck and provide possible applications in medical surgery, dentistry, remote atmospheric sensing, light detection, and the optical parametric oscillator. The effect of Tb3+ co-doping on the fluorescence emission properties and mutual energy transfer mechanisms were investigated. It was found that Tb3+ greatly increased Er3+ 2.7μm emission by depopulating the Er3+: 4I13/2 level while having little influence on the Er3+: 4I11/2 level, leading to a greater population inversion. The energy transfer efficiency from Er3+: 4I13/2 to Tb3+: 7F0 is as high as 90.27%, and the Er3+: 4I11/2 → 4I13/2 fluorescence lifetime ratio (τ(4I11/2)/ τ(4I13/2)) of the Er3+/Tb3+: PbF2 crystal was calculated to be 422.79%, indicating that Tb3+ ion is an excellent deactivator with which the self-termination bottleneck effect was effectively suppressed. All of these factors imply that Er3+/Tb3+: PbF2 crystal may be a promising material for 2.7μm laser applications.

Bi/Ta double doped Gd0.1Y0.9AlO3 (Bi/Ta:GYAP) near-infrared (NIR) laser crystal was successfully grown. The codoping of Ta5+ was demonstrated to effectively enhance the NIR fluorescence emission in Bi/Ta:GYAP crystal for the first time. The introduced Ta5+ ion can induce the change of valence states from Bi3+ to Bi+ based on the charge compensation mechanism, bringing about the enhanced NIR fluorescence emission. The three NIR fluorescence emission peaks centering at 1005, 1195, and 1280 nm were ascribed to three different Bi+ active centers in Bi/Ta:GYAP crystal. These results suggest that the Bi/Ta:GYAP crystal may have potential applications in NIR broadband lasers.

Ho: LuAG, Yb, Ho: LuAG and Yb, Ho, Pr: LuAG laser crystals with high optical quality were successfully grown by the Czochralski method. Compared with Ho: LuAG and Yb, Ho: LuAG crystals, Yb, Ho, Pr: LuAG crystal not only shows a better absorption characteristic but also exhibits weaker ~2 μm emission, as well as superior mid-infrared (MIR) at ~3 μm emission. The ~3 μm MIR emission intensities of Yb, Ho, Pr: LuAG under excitation of a common 970 nm laser diode (LD) is almost nine times that of the Ho: LuAG crystal and twice as much as that of the Yb, Ho: LuAG crystal. The crystal growth, absorption spectra, J-O parameters, emission spectra, fluorescence lifetimes and the energy transfer mechanism in Yb, Ho, Pr: LuAG crystal were studied in this work. The energy transition efficiency from the lower laser level of Ho3+: 5I7 to Pr3+: 3F2 level is as high as 66.6%, indicating that the Pr3+ ion is an effective deactivation ion for Ho3+ ion in Lu3Al5O12 crystal. All these results show that Yb, Ho, Pr: LuAG crystal may become a promising material for developing solid state lasers at around 3 μm under a conventional 970 nm LD pump.

The use of Tb3+ codoping for the enhancement of the transition of Tm3+:3H4→3F4 ∼1.4 μm emissions was investigated in the Tm3+/Tb3+ codoped (Gd0.5Lu0.5)2SiO5 (Tm/Tb:GLSO) crystal for the first time. The ∼1.4 μm fluorescence emission properties and energy transfer mechanism of the as-grown crystals were investigated in detail. It is found that the codoped of Tb3+ ion in Tm/Tb:GLSO crystal greatly enhances Tm3+:1.4 μm emission under excitation of a common 789 nm laser diode, depopulates the lower laser level of Tm3+:3F4, and has little effect on the upper laser level of Tm3+:3H4 at the same time. The energy transfer efficiency from the Tm3+:3F4 level to the Tb3+:7F0 level is as high as (74.4±1.5)%, indicating that the Tb3+ ion is an effective deactivation ion for enhancing the ∼1.4 μm emission in Tm/Tb:GLSO crystal. These results suggest that Tm/Tb:GLSO crystal may be a promising material for ∼1.4 μm laser under the pump of a conventional 789 nm LD.

A Dy3+/Tb3+ co-doped Na2Gd4(MoO4)7 yellow laser crystal was successfully grown and analyzed. The use of Tb3+ codoping for enhancing the Dy3+:4F9/2→6H13/2 yellow emissions was investigated in the Na2Gd4(MoO4)7 crystal for the first time. In comparison to Dy3+ single-doped Na2Gd4(MoO4)7 crystal, the Dy3+/Tb3+ co-doped Na2Gd4(MoO4)7 crystal possessed a higher fluorescence branching ratio (80.2%), transition probability (3704 s−1), and fluorescence emission cross section (1.34×10−20 cm2) corresponding to the laser transition 4F9/2→6H13/2 of Dy3+. It was found that the introduced Tb3+ enhanced the 573 nm emission by depopulating the population of the laser lower level Dy3+: 6H13/2, and has little influence on the laser upper level Dy3+: 4F9/2 at the same time. These results suggest that Dy3+/Tb3+ co-doped Na2Gd4(MoO4)7 crystal may be an attractive host for developing solid state lasers at around 573 nm under a conventional 450 nm LD.

We demonstrate numerically the ability for directionally releasing the stored ultrashort light pulse from a microcavity by means of two-pulse nonlinear interaction in a cascading Bragg grating structure. The setting is built by a chirped grating segment which is linked through a uniform segment, including a tunable microcavity located at the junction between the two components. Our simulations show that stable trapping of an ultrashort light pulse can be achieved in the setting. The stored light pulse in a microcavity can be possibly released, by nonlinearly interacting with the lateral incident control pulse. Importantly, by breaking the symmetry of potential cavity, the stably trapped light pulse can be successfully released from the microcavity to the expected direction. Owing to the induced optical nonlinearity, the released ultrashort light pulses could preserve their shapes, propagating in a form of Bragg grating solitons through the uniform component, which is in contrast to the extensively studied light pulse trappings in photonic crystal cavities which operate at the linear regime.

The use of Nd3+ codoping for sensitizing the Ho3+ ion and enhancing the ∼3.9 μm emission from Ho3+:I55→I65 was investigated in the PbF2 crystal for the first time, to the best of our knowledge. The ∼3.9 μm fluorescence emission properties and energy transfer mechanism of the as-grown crystals were investigated. The results show that the Nd3+ ion can act as a sensitizer to the Ho3+ ion, providing an efficient excitation channel, making the Ho3+/Nd3+:PbF2 crystal propitious to be pumped by commercialized InGaAs laser diodes (LDs). Moreover, an enhanced ∼3.9 μm emission was obtained in the Ho3+/Nd3+:PbF2 crystal due to the codoping of Nd3+ ions, leading to an efficient energy transfer from a lower laser level of Ho3+:I65 to Nd3+:I15/24, while having little influence on the higher laser level of Ho3+:I55. These advantageous spectroscopic characteristics indicate that the Ho3+/Nd3+:PbF2 crystal might have potential application in ∼3.9 μm mid-infrared lasers under a conventional 808 nm LD pump.

The Yb3+:BaGd2(MoO4)4 crystal was grown by the Czochralski method and investigated. The absorption and emission spectra reveal that this crystal can be efficiently excited by a commercial laser diode (LD) around 970 nm and its strongest fluorescent peak locates at 1013 nm. Besides, a significant frequency-doubling effect and a Raman effect of the crystal were observed in the experiment, which reveals that the rare-earth (RE) ions doped BaGd2(MoO4)4 crystal has the potential to generate the self-frequency-doubling laser and self-Raman laser simultaneously.

A compact dual-wavelength passively Q-switched green laser by intra-cavity frequency doubling of a Yb:YAG/Crsup4+/sup:YAG/YAG composite crystal was demonstrated for the first time to our best knowledge. The maximum green laser output power of 1.0 W was obtained under the pump power of 9.7 W, and the corresponding slope efficiency is 15.2%. The shortest pulse width, largest pulse energy, and highest peak power were achieved to be 5.54 ns, 246.1μJ, and 40.76 KW, respectively. Dual-wavelength laser oscillation simultaneously at 515 nm and 524.5 nm has been achieved. This passively Q-switched dual-wavelength green laser can be used as a laser source for Terahertz generation.

The use of Pr3+ codoping for enhancement of the transition of Er3+: 4I11/2 → 4I13/2 2.7 μm emissions was investigated in the Er/Yb codoped LiNbO3 crystal for the first time. It is found that the codoped of Pr3+ ion in Er3+, Yb3+ and Pr3+ triply doped LiNbO3 crystal (Er/Yb/Pr: LN) greatly enhances Er3+: 2.7 μm emission under excitation of a common 970 nm laser diode, depopulates the lower laser level of Er3+:4I13/2, and has little influence on the higher laser level of Er3+:4I11/2 at the same time for population inversion. The 2.7 μm emission characteristics and energy transfer were investigated in detail. The energy transition efficiency from lower laser level of Er3+:4I13/2 to Pr3+:3F4 level is as high as 0.42, indicating that the Pr3+ ion is an effective deactivation ion for Er3+ ion in LiNbO3 crystal. These results suggest that Er/Yb/Pr: LiNbO3 crystal may become an attractive host for developing solid state lasers at around 2.7 μm under a conventional 970 nm LD pump.

An Nd:YAG/YAG/Crsup4+/sup:YAG/YAG composite crystal and an LBO crystal were used to generate a passively Q-switched frequency-doubling 473 nm blue laser for the first time, to the best of our knowledge. The result demonstrated that the slope efficiency of this system reaches 18%, which is the highest in all the passively Q-switched 473 nm laser systems reported, to the best of our knowledge. Under the pumped power of 8.64 W, the maximum average output power of 0.93 W was obtained with a pulsewidth of 78 ns, and the repetition rate of 18.5 kHz.

We investigate the broadband anti-Stokes emission (BASE) from Ybsup3+/sup-doped crystals with a laser diode (LD) pumping at 940 nm. Our experiment reveals that Ybsup3+/sup-doped crystals with random cracks are able to generate bright BASE at room temperature and atmospheric pressure. By examining the various characteristics of the crystals and the emitted light, we supply a theory for interpreting the underlying physics for this variety of BASE. In particular, we take into consideration the effects of energy migration, avalanche process, and charge-transfer luminescence. This represents the first time, to the best of our knowledge, that BASE was obtained from Ybsup3+/sup-doped bulk crystals with a high optical-optical efficiency.

Nd:YAG/KTA intra-cavity Raman lasers with two different Raman shifts are experimentally compared for eradiating around 1.15 µm. The different Raman processes are attributed to polarization dependent Raman gain of KTA crystal and nearly linear polarization of Nd:YAG fundamental light with Q-switch operation. Under an incident pump power of 10.2 W and a pulse repetition frequency of 15 kHz, 1.24 W output for the third-Stokes at 1150 nm in X(ZZ)X Raman configuration with the Raman shifts of 234 cm−1 and 1.21 W output for the first-Stokes at 1146 nm in X(YY)X Raman configuration with the Raman shifts of 671 cm−1were achieved by rotating the KTA crystal. The conversion efficiency in both Raman configurations were about 12% respect to the same incident pump power. The slight differences of spectra and pulses are investigated.

We construct a microscopic hyperspectral imaging system to distinguish between normal and cancerous gastric cells. We study common transmission-spectra features that only emerge when the samples are dyed with hematoxylin and eosin (H&E) stain. Subsequently, we classify the obtained visible-range transmission spectra of the samples into three zones. Distinct features are observed in the spectral responses between the normal and cancerous cell nuclei in each zone, which depend on the pH level of the cell nucleus. Cancerous gastric cells are precisely identified according to these features. The average cancer-cell identification accuracy obtained with a backpropagation algorithm program trained with these features is 95%.

We experimentally demonstrate efficient passively Q-switched bulk lasers with composite Yb:YAG/Cr4+:YAG/YAG crystals at 1030 nm for the first time, to the best of our knowledge. The output performance was investigated based on different initial transmissions (T0) of Cr4+:YAG and different transmissions (Toc) of output coupler. Stable passive Q-switching with composite crystal of T0=85% and output coupler of Toc=32% resulted in the maximum average output power of 2.55 W, with corresponding pulse duration of 11.5 ns and repetition rate of 5.71 kHz. The pulse energy and peak power were 446.25 μJ and 38.8 kW, respectively.

Compact passively Q-switched YVO4 first Stokes Raman laser and its frequency doubling laser were reported by using Nd3+:YAG/Cr4+:YAG composite crystal for what is believed to be the first time. Nanosecond lasers at 1176 and 588 nm were obtained. At the incident pump power of 7.84 W, the average output power at 1176 nm was 423 mW with a pulse width of 1.32 ns and the pulse repetition frequency (PRF) of 13.7 kHz. By applying a KTP crystal, an intracavity second harmonic generation (SHG) laser at 588 nm also was realized. With an incident pump power of 8.95 W, we obtained 105.3 mW average output power of a yellow laser corresponding to the pulse width of 4.95 ns and the PRF of 10.75 kHz. In addition, the composite crystal efficiently compacted the resonant cavity.

We present the first observation, to the best of our knowledge, the spontaneous generation of picoseconds pulse trains in a diode-pumped Nd:YAP laser with gigahertz repetition rate. Spatially dependent temporal dynamics were experimentally observed. After theoretically reconstruct the experimental temporal-resolved patterns, we verify that the complicated spatially-dependent temporal dynamics were originated from simultaneous coherent locking combination of fundamental and several additional higher-order transverse modes.

The stable compact operation in the deep ultraviolet laser at 266 nm is reported from a diode-end-pumped acoustic-optic Q-switched Nd:YVO4/KTP/BBO laser. Fourth harmonic is generated by employing multiple reflections of 532 nm light for taking full advantage of the green beam. An ultraviolet laser at 266 nm with average power of 388.5 mW is obtained with a repetition-rate of 20 kHz, a pulse width of about 59.80 ns, and the corresponding optical to optical conversion efficiency of 11.9% from green to UV. High conversion efficiency and a circular spot of 266 nm laser beam have been achieved in an unfocused beam arrangement.