Electro-Optic Deflector Based on KTN Crystal for Phase-Stable Swept Light Source for OCT

Yuzo SASAKI  Takashi SAKAMOTO  Masahiro UENO  Seiji TOYODA  Junya KOBAYASHI  Tadashi SAKAMOTO  Masatoshi FUJIMOTO  Shogo YAMAGISHI  Mahiro YAMADA  Shogo YAGI  

IEICE TRANSACTIONS on Electronics   Vol.E99-C   No.2   pp.250-256
Publication Date: 2016/02/01
Online ISSN: 1745-1353
DOI: 10.1587/transele.E99.C.250
Type of Manuscript: Special Section PAPER (Special Section on Recent Advances in Photonics Technologies and Their Applications)
KTN,  EO deflector,  OCT,  

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We have developed a wavelength-swept laser source with ultrahigh phase stability. A potassium tantalate niobate (KTa1-xNbxO3, KTN) single crystal was employed as an electro-optic deflector for a high-speed wavelength sweep in the laser cavity. The device structure and performance of a KTN deflector is described. The device includes the beam-shaping optics, which can enhance the resolution of a KTN deflector. A 200-kHz sweep rate was obtained with an average output power of 20mW and a coherence length of 8mm for a wavelength range exceeding 100nm. We demonstrated a swept source with ultrahigh phase stability in the 1.3µm wavelength range as a result of the low-jitter operation of the deflector. The standard deviation of timing jitters measured between adjacent A-lines was confirmed to be less than 78ps, which corresponds to a phase difference of 0.017 radians at a Michelson interferometer path difference of 1.5mm. In addition to realizing the phase stability of neighboring A-lines, a long-term stable sweep was demonstrated by eliminating the refresh operation that was previously needed to prevent output power decay.