Optimization of GaAs semiconductor saturable absorber Q-switched lasers

The expressions of pulse characteristics such as output energy, peak power, and pulse width are obtained by solving the coupled rate equations describing the operation of GaAs semiconductor saturable absorber Q-switched lasers. The key parameters of an optimally coupled GaAs saturable absorber Q-switched laser are determined and several design curves are generated from these expressions for the first time. These key parameters include the optimal normalized coupling parameters and the optimal normalized saturable absorber parameters that maximize the output energy or maximize the peak power, and the corresponding normalized energy, normalized peak power, and normalized pulse width. Using the expressions and design curves, one can predict the pulse characteristics and perform the design of an optimally coupled GaAs saturable absorber Q-switched laser.     

A Single-Longitudinal-Mode Passively Q-Switched Nd:YVO_4 Laser Using Black Phosphorus Saturable Absorber

A black phosphorus(BP) saturable absorber(SA) solution with different concentrations(1.0 and 0.5 mg/ml) is fabricated with the liquid-phase exfoliation method. By using the BP-SA, a compact diode-pumped passively Q-switched Nd:YVO_4 laser is demonstrated. One reflecting Bragg gratings is used as the output coupler for mode selection. By inserting those BP-SA solutions in the laser cavity, the maximum single longitude mode,Q-switched output powers of 126 mW at 692.5 kHz and 149 mW at 630.3 kHz are achieved at the pump power of 8.0 W, corresponding to the pulse durations of 144 ns and 196 ns, respectively. Moreover, longitudinal-mode characteristics of Q-switched output laser in different optical cavity lengths based on two-kind BP-SA solution concentrations are investigated. Our results show that BP-SA could also be developed as an effective SA for the Q-switched, single longitudinal mode pulse laser.     

Laser–diode-pumped passively Q-switched Nd:NaY(WO4)2 laser with GaAs saturable absorber

A laser–diode-pumped passively Q-switched new type crystal Nd³⁺:NaY(WO₄)₂ (known as Nd:NYW) laser with GaAs semiconductor saturable absorber has been realized. The dependence of pulse repetition rate, pulse energy, pulse width, and peak power on pump power for different output coupler reflectivities are measured. The coupled rate equations are used to simulate the Q-switched process of laser, and the numerical solutions agree with the experimental results.     

Diode end-pumped passively Q-switched Nd:YAG ceramic laser with Cr4+:YAG saturable absorber

We report on a diode end-pumped passively Q-switched Nd:YAG ceramic laser. By using a Cr⁴⁺:YAG single crystal with an 80% initial transmission as the saturable absorber, stable Q-switched pulses with a 126-μJ pulse energy, a 12-ns pulse width, and an 8.4-kHz pulse repetition rate have been obtained. The Q-switching performance of the laser under different saturable absorption strengths and output couplings was experimentally investigated.     

Pulse width compression and enhancement of peak power in a diode-pumped doubly Q-switched Nd:GdVO<Subscript>4</Subscript> 1.34 μm laser with AO and V<Superscript>3+</Superscript>:YAG saturable absorber

By using both acousto-optic (AO) modulator and V³⁺:YAG saturable absorber, a diode-pumped doubly Q-switched a-cut Nd:GdVO₄ laser at 1.34 μm is realized. The average output power and the pulse width for different AO repetition rate f have been measured. The experimental results show that the doubly Q-switched laser can compress the pulse width and improve the pulsed peak power in comparison to the singly Q-switched laser with AO or V³⁺:YAG saturable absorber. At the pump power 10.34 W and f = 10 kHz, the greatest pulse width compression ratio 72% and the highest peak power improvement 8.8 times have been obtained, respectively.     

Multi-wavelength Q-switched erbium doped fiber laser with a short carbon nanotube based saturable absorber

We demonstrate an all-fiber passively multi-wavelength Q-switched Erbium doped fiber laser (EDFL) based on a short Carbon Nanotube based saturable absorber. With the saturable absorber connected in a longer standing wave based fiber laser cavity, stable single, dual, and multiple wavelength Q-switched low threshold EDFL are achieved. Experimental results show that the output pulse of the filtered single wavelength has the same repetition rate as that of the multi-wavelength output while its average output power is lower than that of the multi-wavelength output.     

Numerical calculations of intracavity dye Q-switched ruby laser

A mathematical model describing the dynamic emission of the Q-switched ruby laser has been adapted. The suggested model allows the investigation of the effects of a dye cell on the mode characteristics of the ruby laser and, moreover, the study of the effect of the laser input parameters on the output laser pulse. This model simulates the nonlinear effects of dye pulse modulation on the laser emission.In addition, a numerical solution of a nonlinear rate equation system of the adapted model is discussed. The solution estimates the density of the emitted radiation, population inversion and energy transfer processes of the ruby laser rod and dye cell for different emission regimes (one pulse regime, free running pulses, repetition periodic pulses). The estimated results of the laser output pulse characteristics are in a good agreement with the other calculated and experimental results.     

Controllable dissipative soliton and Q-switched pulse emission in a normal dispersion fiber laser using SESAM and cavity loss tuning mechanism

We report on the controllable generation of the dissipative soliton and the Q-switched pulse in a normal dispersion fiber ring laser. The hybrid saturable absorber is used to obtain the dissipative soliton or the Q-switched pulse by slightly adjusting the polarization controller. Based on the experimental results and theoretical analysis, the controllable dissipative soliton and Q-switched pulse emission can be induced by the cavity loss tuning mechanism of the fiber laser.     

Single-walled carbon nanotubes on side polished fiber as a universal saturable absorber for various laser output states

We demonstrated four different laser operational states in the same passive fiber ring laser cavity by controlling solely the polarization state in a saturable absorber. The demonstrated laser operational states were continuous wave, mode-locking, Q-switching, and Q-switched mode-locking. The saturable absorber was fabricated by spin-coating a single-walled carbon nanotubes (SWCNT)/polymer composite on a side polished fiber providing enhanced nonlinear interaction with the SWCNT. The wide tuning range of the saturable absorber allows the simple means to generate different forms of laser output from a single laser cavity.     

Passive Q-switching of a laser-diode-pumped intracavity-frequency-doubling Nd:NYW/KTP laser with GaAs saturable absorber

Passive Q-switching of a laser-diode-pumped intracavity-frequency-doubling Nd:NYW/KTP laser has been realized with GaAs semiconductor saturable absorber. The dependence of pulse repetition rate, pulse energy, and pulse width on incident pump power are measured. The coupled rate equations are used to simulate the Q-switched process of laser, and the numerical solutions agree with the experimental results.     

Diode-pumped passively Q-switched Nd:YVO4 laser with GaAs saturable absorber

The intracavity photon density is assumed to be of Gaussian spatial distributions and its longitudinal variation is also considered in the rate equations for a laser diode(LD)end-pumped passively Q-switched Nd:YVO4 laser with GaAs saturable absorber.These space-dependent rate equations are solved numerically.The dependences of pulse width,pulse repetition rate,single-pulse energy,and peak power on incident pump power are obtained.In the experiment,the LD end-pumped passively Q-switched Nd:YVO4 laser with GaAs saturable absorber is realized and the experimental results are consistent with the numerical solutions.     

Nd:Sr5(VO5)3F Q-Switched Lasers with Cr4+:YAG

The Cr4+-doped saturable absorber Cr4+:YAG is used as the passive Q-switch for a conventional pulsed Nd:Sr5(VO5)3F(Nd:S-VAP) oscillator, and the short high-peak-power pulses of laser have been obtained. The laser output characteristics are investigated under the conditions of different small-signal transmittance of Cr4+:YAG and different reflectivity of the output coupler. The rate equtions of Q-switched coupling wave are given, and the numerical solutions of equations are in agreement with the experimental results.     

氧化石墨烯被动调Q掺铒光纤激光器

报道了基于氧化石墨烯的被动调Q掺铒光纤激光器。激光器采用环形腔结构,调Q器件为自制的氧化石墨烯可饱和吸收镜。泵浦功率在81~505 mW范围内时,得到了重复频率68~124 kHz的稳定的调Q脉冲输出,脉宽为0.47~1.60 s。由于泵浦功率限制,激光器最大输出功率为10 mW, 相应单脉冲能量为80.6 nJ。此种基于氧化石墨烯可饱和吸收体的被动调Q光纤激光器体积小、成本低廉、结构简单、稳定性高、光束质量高,具有广阔的应用前景。     

基于少模光纤被动调Q柱矢量光光纤激光器

通过单模光纤和少模光纤熔融拉锥耦合的方法制备出模式转换器,而后将一层多壁的碳纳米管薄膜作为可饱和吸收体覆盖到拉锥光纤的锥区,形成一种可饱和吸收体柱矢量光器件.结合调Q光纤激光器和模式转换器件的优势,可以简单高效地产生脉冲柱矢量光束,并得到具有峰值功率高、模式纯度高等特点的脉冲高阶模式激光输出.通过实验实现了中心波长为1560nm、最大单脉冲能量和最大峰值功率分别为116nJ和57mW的稳定调Q脉冲输出.通过调节光路中的偏振控制器,可以分别实现径向和角向偏振的调Q脉冲激光的输出.     

脉冲LDA泵浦Nd∶YVO4/GaAs被动调Q锁模激光器

用脉冲激光二极管阵列（LDA）作为泵浦源、微柱透镜阵列和透镜导管作为耦合系统,以As＋注入GaAs可饱和吸收片作为被动调Q锁模元件,实现了Nd∶YVO4激光器调Q锁模运转.调Q运转阶段,激光器每泵浦脉宽内输出一个调Q脉冲,调Q脉宽7ns.调Q锁模运转阶段,初始透过率60％的GaAs晶片对调Q包络内的锁模脉冲的调制深度达到95％以上,锁模脉冲重复频率991 MHz.研究了加在LDA上的电压、方波脉冲的脉宽和重复频率对调Q锁模脉冲特性的影响,并对实验结果进行了讨论.     

Passively Q-switched Self-frequency Doubling NYAB laser with GaAs Saturable Absorber

By using a passive Q-switch with GaAs saturable absorber, the Q-switched self-frequency doubling NYAB laser at 0.531μm has been successfully realized. The pulse width and the single pulse energy are measured. The numerical solutions of the coupling wave rate equations are in agreement with the experimental results.     

Diode-pumped doubly passively Q-switched c-cut Nd:GdVO4 1.34 μm laser with V:YAG and Co:LMA saturable absorbers

By simultaneously using both V³⁺:YAG and Co:LMA saturable absorbers in the cavity, a diode-pumped doubly passively Q-switched c-cut Nd:GdVO₄ laser at 1.34 μm is demonstrated for the first time. The average output power, the pulse width and the pulse repetition rate have been measured. The experimental results show that the doubly passively Q-switched laser can generate shorter pulse width with higher peak power in comparison to the singly passively Q-switched laser only with V³⁺:YAG or Co:LMA saturable absorber. At the pump power 13 W, the pulse width has been compressed 83% and the peak power has been improved 15 times, respectively.     

Passively Q-switched Self-frequency Doubling NYAB laser with GaAs Saturable Absorber

1　Ｉｎｔｒｏｄｕｃｔｉｏｎ　　Ｉｎｒｅｃｅｎｔｙｅａｒｓ ,ｉｎｃｒｅａｓｉｎｇａｔｔｅｎｔｉｏｎｈａｓｂｅｅｎ ｐａｉｄｔｏｈｉｇｈ ｐｅａｋ ｐｏｗｅｒａｌｌ ｓｏｌｉｄ ｓｔａｔｅｐｕｌｓｅｄｂｌｕｅ ｇｒｅｅｎｌａｓｅｒｓｆｏｒｓｏｍｅａｐｐｌｉｃａｔｉｏｎｓｓｕｃｈａｓｓｐｅｃｔｒｏｓｃｏｐｙ ,ｄｉｓｐｌａｙ ,ｏｐｔｉｃａｌｄａｔａｓｔｏｒａｇｅ ,ｕｎｄｅｒｓｅａｃｏｍｍｕｎｉｃａｔｉｏｎｓａｎｄｓｏｏｎ .Ｓｕｃｈｌａｓｅｒｓｃａｎｂｅｒｅａｌｉｚｅｄｂｙｉｎｔｒａｃａｖｉｔｙｏｒｅｘｔｅｒ…     

Mathematical modeling of TE CO2 laser with SF6 as a saturable absorber

A mathematical model describing the dynamic emission of a single mode TE CO₂ laser with saturable absorber has been adapted. A six-temperature model has been used to describe the amplifying medium, while a four-coupled energy level is used to describe the selective absorbing medium. The suggested mathematical model allows the investigation of the effects of the intracavity absorber on the mode characteristics of the TE CO₂ laser and, moreover, the study of the effect of the laser input parameters on the output laser pulse. The model simulates the passive Q-switch in both low- and high-pressure cases in the absorbing medium.

In addition, numerical solutions of a non-linear rate equation system of the suggested model are quantitatively discussed. The solutions describe the photon number density, the population inversion and the energy transfer processes of amplifying and absorbing media.     

Diode-pumped Nd:YVO<Subscript>4</Subscript> laser passively Q-switched with graphene oxide spin coated on ITO substrate

Two graphene oxide saturable absorbers (GO-SAs) spin coated on indium tin oxide (ITO) substrate have been prepared and their transmissivity spectra have also been measured. The performance of the diode-pumped passively Q-switched Nd:YVO₄ laser with GO-SA has been investigated for the first time. The shortest pulse width of 113 ns and the highest peak power of 4.3 W are obtained at the pump power of 5.04 W. The output laser characteristics have demonstrated that graphene oxide is a promising saturable absorber for passive Q-switching.