高功率垂直腔底发射激光器的偏振特性

Polarization Properties of High-Power Vertical-Cavity Bottom-Emitting Lasers

在垂直腔面发射激光器(VCSEL)作为显示光源的应用中,为了获得高功率的偏振激光,研究了980nm大口径底发射VCSEL的偏振特性。通过刻蚀矩形台面和矩形出光口径,制备矩形VCSEL。在连续条件下,出光口径为550μm×300μm的底发射矩形VCSEL最大输出功率为660mW,微分电阻为0.09Ω。实验中,矩形VCSEL在工作电流下,同时存在稳定的水平偏振光和竖直偏振光,并且沿着矩形长边出射的水平偏振光一直占据主导地位。而圆形VCSEL在水平和竖直方向的激射情况几乎相同。水平偏振光的激射光谱相对于竖直偏振光出现蓝移,并且用对称三层波导模型解释了蓝移现象。研究了矩形VCSEL的正交偏振比与矩形口径长宽比的关系。实验结果表明,矩形柱结构能够有效地稳定VCSEL的偏振方向,使大口径器件激射高功率的偏振激光。

When using vertical-cavity surface-emitting lasers（VCSEL） as laser source,in order to obtain high-power polarized laser,polarization feature 980 nm large-aperture bottom-emitting VCSEL is investigated in this paper.A rectangular-shaped VCSEL is fabricated by etching rectangular mesa structure and rectangular output aperture.The maximum power of bottom-emitting rectangular-shaped VCSEL is 660 mW with 550 μm×300 μm output aperture under continuous wave condition,and the differential resistance is 0.09 Ω.It is found that H-polarization（horizontal） and V-polarization（vertical） demonstrated steadily coexistence over the entire range of operation current.And H-polarization dominated over V-polarization which is parallel to the shorter side of the rectangular output aperture.Compared with the circular-shaped VCSEL,both H-polarization and V-polarization nearly have the same lasing situation.Spectrum blue-shift of H-polarization light occurres with respect to V-polarization light.This phenomenon is explained by the symmetric three layer waveguide model.The dependence of the orthogonal polarization ratio on the aspect ratio of the output aperture is investigated in the rectangular-shaped VCSEL.It is found that the rectangular post is an effective way to stabilize the output polarization of large-aperture VCSEL,which can emit high-power polarized laser.