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Batop SAM 可饱和吸收体
内容：
微芯片安装
工作原理
脉冲能量Ep
重复率frep
脉冲宽度tp
微芯片安装
上图所示是的被动调Q的单片微片激光器由Nd掺杂YVO4激光晶体和可饱和吸收镜(SAM)粘合在一起组成。激光腔体长度L在区域100μm..300μm主要由激光晶体厚度决定。典型掺Nd是2&或3%。 来自一个连续二极管激光的线性极化808nm泵浦光平行面向c轴自动对焦激光晶体。激光晶体中的一个典型的泵浦光斑直径约为50μm-100μm。1064nm波长单模激光输出光脉冲是从分色镜中反射出。
微芯片的主要特性取决于以下参数：
脉冲能量Ep
重复率frep
脉冲宽度tp
工作原理
可饱和吸收体（SAM）作为被动调Q开关。 对波长为1064nm的激光来说低强度非饱和SAM反射率在0.75-0.9的区域。激光晶体的连续泵浦上部将被填补直到获得足够大的自发辐射。然后SAM饱和，激光器发出一个强大的短脉冲。 在连续泵浦期间，发展重复，重复频率德国财务报告管理小组inceasing与泵浦功率密度接近线性关系。由于光能量的一部分是在SAM的吸收层消退，安排必须删除此芯片产生的热量。如果激光腔长度短，单模激光泵浦光斑直径小。
pulse energy Ep
According to the well established formalism (Journal of the Optical Society of America B, Vol. 16, Issue 3, pp. 376-388, 1999) of passive Q-switched microchip laser the pulse energy Ep can be estimated as follows:
with
Fsat,L saturation fluence of the laser material
A pump spot area in the resonator
ΔR modulation depth of the SAM
T transmission of the output coupler
Ans non-saturable losses, mainly from SAM
With typical values Fsat,L = 37.3 mJ/cm2, A = 1.3x10-5cm2 ( 40 μm spot diameter), ΔR = 0.1, T = 0.1, and loss = 0.05 the pulse energy can be estimated to Ep ~ 32 nJ.
repetition rate frep
The average output power Pav is proportional to the pump power. Therefore the repetition rate shows a linear behavior by changing the pump power according to:
with
ηs slope efficiency
Pp pump power
PP,th pump power threshold
By changing the pump power PP repetition rates between 100 kHz and 2 MHz can be realized with a nearly constant pulse energy EP. Because the pulses start with spontaneous emission, the repetition rate shows a time jitter of about 1 %, increasing with decreasing pump power and rate.
pulse duration tP
The pulse duration tP in passive Q-switched lasers can be estimated by:
with
TR resonator round trip time
ΔR modulation depth of the SAM
n refractive index of the resonator material
L resonator length
c speed of light in vacuum.
With a short laser crystal length L = 0.2 mm, refractive index n ~ 1.95, and a SAM modulation depth of ΔR = 0.1 the pulse duration is about 91 ps.
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