Sota Okamoto

Frequency doubling of a Nd:YAG laser using a crystal-cored fiber of an organic 4-(N,N-dimethylamino)-3-acetamidonitrobenzene

Optical second-harmonic generation from a glass-clad fiber with an organic core crystal of 4-(N,Ndimethylamino)-3-acetamidonitrobenzene (DAN) is demonstrated. Phase matching was due to cerenkov radiation. Linear and nonlinear optical properties of DAN, a fabrication technique of a crystal-cored fiber, and a focusing method of the generated second-harmonic wave are studied.

Collimating properties of an axicon for the Čerenkov-radiation-type second-harmonic light from a crystal-cored fiber

The optical second-harmonic wave generated from a crystal-cored fiber from the Čerenkov-radiation-type phase matching can be collimated by an axicon and then can be focused by a spherical lens to a diffraction-limited spot. Tolerance of the optical system to meet the Maréchal criterion is analyzed; tolerable maximum errors in alignment and fabrication of the axicon lens are evaluated.

Design, fabrication, and evaluation of crystal-cored fibers for efficient second-harmonic generation based on Čerenkov-radiation-type phase matching

A formulation for calculating the optical second-harmonic power based on the Cerenkov-radiation-type phase matching is derived for a crystal-cored fiber. The prerequisite condition for high efficiency is expressed by a simple relation by use of the refractive indices of a core crystal, a core radius, and a fundamental wavelength. An organic crystal-cored fiber is designed and practically fabricated by the guiding principle derived here. A blue second-harmonic wave of 1.4 mW is obtained from a 1-mm-long fiber by use of a 60-mW semiconductor laser, and the second-harmonic intensity agrees well with the prediction. Degradation of the organic core crystal caused by the generated blue wave is observed, and the lifetime of the device is evaluated.