单偏振半导体光放大器扫频光相干成像系统

Optical Coherence Imaging System Based on a Polarization-Dependent Semiconductor Optical Amplifier-Enabled Swept Laser

搭建完成了基于单偏振半导体光放大器扫频光源的光相干成像系统,此系统可以实现高速光相干层析成像与光相干显微成像。系统中的扫频光源使用偏振相关的半导体光放大器作为放大单元,该光放大器有着增益谱宽大、输出功率高的优点,使得光源仅使用一个放大器即可获得合适的增益谱宽与输出功率,并可采用傅里叶域锁模技术大幅提高其扫频速率。采用傅里叶域锁模技术时,扫频光源输出功率达到32 mW左右,有效扫描频率为45kHz,输出光谱的中心波长为1326nm,光谱宽度为115nm。利用系统进行高速光相干层析成像时,横向分辨率为9μm,纵向分辨率为12.9μm左右,灵敏度为105dB。利用系统进行光相干显微成像时,可以清楚地看到洋葱内表皮细胞的结构。

As noninvasive biomedical imaging techniques, optical coherence tomography （OCT） and optical coherence microscopy have good application prospects in future. A swept-source imaging system based on a polarization-dependent semiconductor optical amplifier （SOA） enabled Fourier domain mode locked laser （FDML） is demonstrated, which can be used for the two imaging techniques mentioned above. The FDML with a polarization- dependent SOA generates ～32 mW output power at 45 kHz sweep rates, with a tuning range of 115 nm centered at 1326 nm. Because of the broad bandwidth and high saturation power of the polarization-dependent SOA, the laser has the advantage of simple structure. It uses only one SOA for operating with enough bandwidth and output power. Using the SOA-enabled FDML laser, an OCT system with axial resolution of ～ 12.9μm, transverse spot size of 9 μm and sensitivity of 105 dB is achieved. The structure of the epidermal cells of onion can be observed by this imaging system.