It is shown that the resonance-like phenomena or the relaxation oscillations in the light output of the directly modulated injection lasers is suppressed by a non-resonant π-type electric circuit connected to the laser diode. Application of this suppressor circuit is not sensitive to the bias current of laser diode and the cut-off frequency of modulation is sufficiently large. It is pointed out that the use of this method at the narrow stripe laser is the most effective.

The wavelength shift of a dynamic-single-mode (DSM) laser directly modulated by sinusoidal current has been investigated using the large-signal analysis. A rate equation which includes carrier diffusion terms is solved numerically. The variation of the carrier density as an origin of the dynamic wavelength shift is calculated. The calculated dynamic wavelength sifts are in good agreement with experiments. At high modulation frequency range, the dynamic wavelength shift is mainly caused by relaxation oscillations and the shift is almost constant to the stripe width of active guide. It shows that the dynamic wavelength shift in pulse modulation is also independent of the stripe width of active guide. An analytical expression of dynamic wavelength shift is given at low modulation frequency range. When the modulation depth is below 30 percent, the small-single analysis is in agreement with large-signal analysis. By considering the effect of spontaneous emission, a modified small-signal analysis presented here is applicable to a modulation depth of 100 percent in the case of low frequency limit.

Phase-matched film thickness are studied precisely for SHG in a nonlinear quartz-glass waveguide. The glass film waveguide deposited upon the surface of quartz suffers non-uniform stress due to the thermal expansion. This effect generates an anisotropic property in the film. Taking this anisotropy of the glass film into account, the observed film thickness for phase-matched condition results in good agreement with the theory.

Wavelength-tunable 1.5 µm GaInAsP/InP bundle-integrated-guide distributed Bragg reflector (BIG-DBR) dynamic-single-mode lasers are presented. Tuning is due to free carrier plasma effect generated by the injected tuning current at the monolithically integrated tuning regions. Low threshold current CW operation of 28 mA was obtained in junction-up mounting. Wide-range continuous wavelength tuning more than 9 was demonstrated for the first time.

Field induced refractive index variation and the ratio of index to loss variations p' which is an important parameter deciding the loss characteristics of an intersectional optical switch, was analyzed for GaInAs/InP quantum box structure. We found that large index variation and large | p| value(10) with low fundamental absorption, which are required for low insertion loss switch(1 dB), can be attained. Further the usable wavelength range for low loss switching operation is shown to be around 8 nm.

The harmonic and phase distortions in the direct modulation of injection lasers are given theoretically with help of a large signal analysis by a Fourier-series-expansion method. It is shown that the distortions are relatively small when there is no-kink in the I-L curve and the magnitudes of the distortions are inversely proportional to the bias current above threshold and proportional to the photon lifetime in laser cavity. It is also shown that the maximum modulation frequency in the analog-modulation is limited by the phase distortion rather than the amplitude distortion.