The frequency chirp of current modulated semiconductor diode lasers

Wavelength modulation or frequency chirp accompanies the power modulation of current modulated semiconductor diode lasers. Standard diode laser theory predicts that the laser gain and wavelength are clamped for modulation frequencies well below the relaxation oscillation frequency (except at frequencies so low that temperature modulation in the laser induces wavelength modulation). The wavelength clamping is not observed in experiments. We show that straightforward analysis of the wave equation for the laser waveguide can re-solve this discrepancy.