[OPTICAL REVIEW Vol. 7, No. 4 (2000) 309-316]

Characteristics of Wavelength Tunable Femtosecond Soliton Pulse Generation Using Femtosecond Pump Laser and Polarization Maintaining Fiber

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