超短脉冲激光在掺Er3+ 磷酸盐玻璃中制备光波导的实验研究

超短脉冲激光通过非线性吸收调制光学材料折射率提供了一种高效制备集成三维光子器件的途径.掺Er³⁺磷酸盐玻璃由于其优异的特性以及在1.55μm通信波段附近的发射光谱，成为了集成光学主动增益材料中的研究热点.实验采用重复频率1 kHz,中心波长800 nm,脉冲宽度120 fs的钛宝石飞秒激光放大系统作为制备波导的光源，系统研究了加工参数对激光写入形貌、波导形成及光学特性的影响.实验结果表明，在狭缝整形辅助短焦物镜横向刻写条件下，写入脉冲能量为1.8μJ时，光波导可以在写入速度为10μm/s-160μm的较宽范围内形成；写入速度为40μm/s时，光波导写入脉冲能量参数窗口为1.6μJ-2.0μJ;波导写入深度在125μm-200μm范围时，波导横截面对称性较好且折射率修改明显；近场强度测量结果显示所制备波导近场强度分布对称，导光特性良好.通过有限差分法反推波导区域折射率修改分布，结果显示最大折射率修改为Δn=6.6×10^-4.截断传输损耗测量结果显示所制备波导的传输损耗低至0.91 dB/cm.

Experimental Study on Fabrication of Optical Waveguides in Er3+-doped Phosphate Glass by Ultrashort Pulse Laser

Ultrashort pulse laser provides an efficient way to fabricate integrated photonic devices by modulating the refractive index of optical materials with nonlinear absorption to form three-dimensional optical waveguides. Er3+-doped phosphate glass, due to its excellent characteristics and emission spectrum in the communication band near 1.55 μm, has become a research hotspot in integrated optical active gain materials. In the experiment, the Ti: sapphire femtosecond laser amplification system with the output pulse laser parameters of repetition frequency of 1 kHz, center wavelength of 800 nm and pulse width of 120 fs was used as the inscribed light source. The impact of processing parameters on waveguide formation, waveguide morphology and optical properties were systematically studied. The experimental results show that under the transverse writing condition with slit shaping assisted short focus microscope objective, with a fixed pulse energy of 1.8 μJ, the optical waveguide can be formed in the scan speed range of 10 μm/s-160 μm/s. With a fixed scan speed of 40 μm/s, the writing pulse energy window of the optical waveguide is 1.6 μJ-2.0 μJ. The waveguide cross-section is symmetrical and the refractive index is obviously modified, within the depth range of 125 μm-200 μm from the surface. The near-field intensity measurement results show that the near-field intensity distribution of the prepared waveguide is symmetrical, and the light guiding characteristics are maintained well. The refractive index modification distribution in the waveguide region is simulated based on the finite difference method, and the results show that the maximum refractive index modification value is Δn=6.6×10-4. The results of cut-back measurement show that the lowest waveguide propagation loss is only 0.91 dB/cm.