Yoshiro MATSUO¹ Norihiko NISHIZAWA,¹ Masakazu MORI² and Toshio GOTO¹

¹Department of Quantum Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-8603 Japan, ²Department of Information Network Engineering, Aichi Institute of Technology, 1247, Yachigusa, Yakusa-cho, Toyota, 470-0392 Japan

(Received August 17, 1999; Accepted March 21, 2000)

We have investigated both experimentally and numerically the characteristics of wavelength tunable femtosecond soliton pulse generation using a pulse width variable fiber laser and two different types of polarization maintaining fibers. The generated soliton shows the feature of the pulsewidth becoming almost constant at ~ 250 fs under any conditions of the pump pulse for 220m fiber. High conversion efficiency from pump pulse to a generated soliton pulse accounting for as much as 73% can be obtained. This efficiency decreases with increase in the input power or wavelength shift. A superior conversion efficiency and broad wavelength shift can be obtained by using a more shortened pump pulse. In the numerical calculations, it is predicted that under a condition of constant power of pump pulse, the maximum wavelength shift is achieved when the soliton number N is ~ 1.4. The difference of mode field diameter and the group velocity dispersion (GVD) coefficient β₂ affect the wavelength shift and conversion efficiency. Using the fiber with small mode field diameter and small absolute value of GVD coefficient β₂, a high conversion efficiency and large wavelength shift can be obtained.

Key words : soliton pulse, optical fiber, Raman scattering, nonlinear effect, wavelength conversion, ultrashort pulse, chromatic dispersion

y-matsuo@echo.nuee.nagoya-u.ac.jp