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Batop SAM 可飽和吸收體

內(nèi)容：

微芯片安裝

工作原理

脈沖能量Ep

重復(fù)率frep

脈沖寬度tp

微芯片安裝

上圖所示是的被動(dòng)調(diào)Q的單片微片激光器由Nd摻雜YVO4激光晶體和可飽和吸收鏡(SAM)粘合在一起組成。激光腔體長(zhǎng)度L在區(qū)域100μm..300μm主要由激光晶體厚度決定。典型摻Nd是2&或3%。 來自一個(gè)連續(xù)二極管激光的線性極化808nm泵浦光平行面向c軸自動(dòng)對(duì)焦激光晶體。激光晶體中的一個(gè)典型的泵浦光斑直徑約為50μm-100μm。1064nm波長(zhǎng)單模激光輸出光脈沖是從分色鏡中反射出。

微芯片的主要特性取決于以下參數(shù)：

脈沖能量Ep

重復(fù)率frep

脈沖寬度tp

工作原理

可飽和吸收體（SAM）作為被動(dòng)調(diào)Q開關(guān)。 對(duì)波長(zhǎng)為1064nm的激光來說低強(qiáng)度非飽和SAM反射率在0.75-0.9的區(qū)域。激光晶體的連續(xù)泵浦上部將被填補(bǔ)直到獲得足夠大的自發(fā)輻射。然后SAM飽和，激光器發(fā)出一個(gè)強(qiáng)大的短脈沖。 在連續(xù)泵浦期間，發(fā)展重復(fù)，重復(fù)頻率德國(guó)財(cái)務(wù)報(bào)告管理小組inceasing與泵浦功率密度接近線性關(guān)系。由于光能量的一部分是在SAM的吸收層消退，安排必須刪除此芯片產(chǎn)生的熱量。如果激光腔長(zhǎng)度短，單模激光泵浦光斑直徑小。

pulse energy E_p

_{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

F_{sat，L saturation fluence of the laser material}

_{Apump spot area in the resonator}

_{ΔRmodulation depth of the SAM}

_{T transmission of the output coupler}

_{Ansnon-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 P_av 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 P_P repetition rates between 100 kHz and 2 MHz can be realized with a nearly constant pulse energy E_P. 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 t_P

The pulse duration t_P 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.