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11 February 2011A mechanical-free 150-kHz repetition swept light source incorporated a KTN electro-optic deflector
We present a new light source for the swept-source OCT, that is, an external-cavity LD incorporating an electro-optic
deflector. We use a KTN deflector that is unique in being very fast and simultaneously providing an appreciable
deflection caused by injected carriers. Particularly, high-speed and nearly linear to the applied voltage operation is
attained when KTN crystal is pre-charged. Our 1.3-μm Littman-Metcalf external-cavity laser exhibits static linewidth <
0.1 nm, and a 110-nm scanning range up to 150-kHz under a ±200 V sinusoidal driving voltage to the deflector. Being
free of mechanical resonance, the laser would hopefully realize a faster (in a separate study, deflector itself worked up to
400 kHz) and wavenumber-linear scan that is ideal for the swept-source OCT by designing the waveform of driving
voltage. And as for the resolving power of deflector, while our KTN deflector has only 35 spatial resolvable points, the
number of wavelength points for the swept source clearly exceeds to this limit, which we attribute to line narrowing
effect accompanied by the laser operation. Preliminary OCT images taken using the swept source are also presented.