SESAMs structure design for GHz femtosecond lasers

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• 作者：Sha Wang^a ; ^{shawang.laser@outlook.com" class="auth_mail" title="E-mail the corresponding author} ; Yan-biao Wang^a ; Guo-ying Feng^a ; ^{guoing_feng@scu.edu.cn" class="auth_mail" title="E-mail the corresponding author} ; Shou-huan Zhou^a ; ^b
• 关键词：SESAM ; Gigahertz repetition rate ; Femtosecond laser ; Two photon absorption
• 刊名：Optik - International Journal for Light and Electron Optics
• 出版年：2016
• 出版时间：March 2016
• 年：2016
• 卷：127
• 期：5
• 页码：2647-2652
• 全文大小：1290 K

文摘

SESAM mode locked femtosecond laser at higher frequency up to gigahertz repetition rate suffers from the tendency for Q-switching instabilities. Increasing the pump power and decreasing the spot size at both the laser crystal and SESAM could help to stabilize the cw mode-locking of a gigahertz ultrafast laser. However, this is limited by the available laser diode pump power and may result in SESAM damage. Two photon absorption (TPA) effect in SESAM will generate ‘roll over’ effect of nonlinear reflectivity curve, which will decrease the critical pulse energy and critical pump power for cw mode-locking. By designing SESAM structures, we could optimize the ‘roll over’ effect and suppress the Q-switching instabilities. From simulation, we find out that enhanced SESAM with a cap layer thickness of 116 nm and first GaAs layer thickness of 517 nm will lead to a minimum critical pump power of 12.1 W for our designed 1 GHz laser cavity.